stephenbrooks.orgForumTalkSensibleInterstellar travel? [pulled over from UD board]
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Stephen Brooks
2002-05-22 12:39:31
Stephen Brooks
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posted May 14, 2002 22:59
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Remind me not to start threads just because I've done nothing all day except think around in circles about really WEIRD stuff that most people wouldn't bother with.  Well I won't do it next time.  I was thinking like this...

Fusion power has been demonstrated, and now is just a matter of scaling up and engineering to work well.  NASA are looking at all sorts of fusion systems - some rather more "direct" than I'd considered.  What I mean is, instead of waiting until about 2050 for controlled fusion reactors (those "Tokamac"/doughnut-shaped things) to be developed, and then another 20 years for them to be scaled down and adapted for spacetravel, they're thinking "maybe we don't need a controlled plasma at all" and just have the idea of starting the fusion in the rocket nozzle.  Anyway, that's not what I was going to talk about.

What I was thinking was, by 2100 we may be coming across some _other_ limits to space exploration other than mere propulsion power: namely, to get to some places in a reasonable length of time (even in our own Solar System) would require accelerations that would crush you.  The minimum time a "comfortable" ride to Saturn would take is 8.5 days - that's accelerating at 1G half way there and decelerating at 1G for the rest, to come to a halt at Saturn.

To get there faster, the spacecraft would have to accelerate more.  The problem with this is that the _spacecraft_ accelerates, but the passengers initially do not.  What makes the passengers move then?  It's actually their point of contact with the spaceship that does it, just as when you're in a coach and it accelerates you feel the seat pushing you forward.  In a way, it's not the coach engine that's making you move so much as the seat, or the floor, or whatever you're touching at the time.

If the spacecraft is accelerating at say 20G, that means the floor or whatever is going to have to exert that much _more_ force on you.  As it turns out, more than a few seconds at 20G is lethal for a human: the force/pressure exerted on you is equivalent to 1.5 tons.  However, there are instances where such forces are encountered and they aren't a problem - for instance the atmosphere around us is at a fairly high pressure - 10 tons per square metre.  This is because we are really like those deep-sea fish that explode when taken out of their deep ocean.  In our case, the ocean is the atmosphere of air above us.  This doesn't to me suggest any immediate solution to the high-acceleration problem.

The thing I was thinking of today was that if, before the flight, you were drinking water with a biologically inert but highly magnetic compound suspended in it, then by putting a magnetic field within the spaceship, force could be exerted on the compound (which would have to attain an approximately even distribution throughout you - the more even, the higher acceleration would be possible) and that would mean that you weren't going to be crushed against the floor any more because every part of you is being accelerated rather than you just being pushed from one side.

I also thought of another way of doing this "evenly applying force" thing, but it turned out to involve _very_ high levels of radiation so not a sensible proposition for humans in space!

And I'm posting all this because... I'm wondering if anyone else has thought about all this?


Caulkhead
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Rate Member posted May 14, 2002 23:11
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How about a damper system, that cushions the effect...like a gun recoiling.


Une Fois
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posted May 14, 2002 23:19
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Stephen--There is no real relation between the *translational* force required to accelerate the human and the *hydrostatic* force exerted by the atmosphere.  It is not the force on the skin or lungs that causes rapid death at high G-forces.  It is shearing.

There are long-term problems (days?) including the shutting down of digestive function and probably that of the spleen.  I expect that this would occur at quite low G-forces, I'll hazard a guess of 2-4G. You'll have to beat this problem for extended acceleration.

The mid-term problem (seconds) is the failure to move blood properly.  This is what causes black-outs.  This occurs at 5-9 G depending on the individual.  You'll have to beat this problem, too.  There is some research on this of course, but I don't think anyone knows how long one can endure this with even the best flight suits.

The immediate problem (milliseconds) is rupture of internal organs.  This is not caused by force, per se, but by shear forces, the *differential* forces within the body that cause internal structures to twist, bend, split.  Under close (terrestrial) care, many organ ruptures are survivable, but above 15 Gs, depending on how the forces are applied to the body, the aorta ruptures, and that is immediately fatal.  Same for segments of the spine, the heart, and large blood vessels.  No one has any idea how to beat this!--and there has been a huge amount of research on this, including by the auto industry for obvious reasons.

For space travel, the obvious preventive measure would be structural surgery on the traveler before space travel to rebalance translational forces, in turn to minimize shear.  In essence, inserting a fairly large amount of scaffolding throughout uncomfortable regions of the body.

You first.


Stephen Brooks
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posted May 14, 2002 23:22
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quote:
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Originally posted by Caulkhead:
How about a damper system, that cushions the effect...like a gun recoiling.
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Those work great for systems where there is an intense brief acceleration, but unfortunately the mechanics work out so that the _average_ acceleration stays the same.  So in most vehicles on Earth right now, a cushioning system would work, since they never attain _really_ high speeds and never accelerate continuously for a long length of time (acceleration is usually followed by deceleration too).

If you tried to put a cushioning system in a continuously-accelerating craft you'd simply sink into the cushion until it was exerting the same 20G or whatever on you as the floor would have anyway: the force would only be reduced for the short period before the system was in equilibrium again.

(Is that what you had in mind, or something else?) It's seems to be a fairly difficult thing to think of ways to work around, although I haven't done a thorough search of the internet yet. 


Stephen Brooks
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posted May 14, 2002 23:30
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Thanks for the information about the effects of G-forces - I knew they were pretty nasty.


quote:
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Originally posted by Une Fois:
Stephen--There is no real relation between the *translational* force required to accelerate the human and the *hydrostatic* force exerted by the atmosphere.  It is not the force on the skin or lungs that causes rapid death at high G-forces.  It is shearing.
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What I had in mind at the time was what would happen if the hydrostatic force could be applied asymetrically in some way.  But as I said that line of reasoning probably leads nowhere much.

The constant acceleration problem would really be solved if there was some way of getting rid of that _differential_ force (the shear you mention is one part of that, others are simple compression forces) between parts of the body.  That is, some method for applying force to all parts of an object (ideally) in proportion to their mass.  The spacecraft would be subjected to these sorts of forces too: the engine would tend to want to tear away from the rest of the ship! 


simplybarry
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posted May 14, 2002 23:44
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Having all tissues 100 percent saturated with a fluid would mitigate this problem.  A fluid such as flourinert(sp) can carry enough dissolved ozygen to support respiration but would require diaphram muscles of a herculean scale to overcome the inertia and viscosity of a liquid fluid.

This system converts vectorial forces into hydrostatic forces and fluids arnt compressible.

Moma nature gives us a good prototype-the fetus in the amenotic sac.  But you still got to cycle the liquid and solid wastes in and out of the system...messy

Seems easer to freeze the crew and then thaw them out when you get there.

Tink I'll stay here, send me a note when you get there.

Id rather see old things with new eyes then new things with old eyes.


rynther
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posted May 14, 2002 23:47
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why don't you look at the liquid breather systems that are used for REALLY deep diving

breathing liquid isn't exactly cozy, but a block of liquid with no air bubbles might just do the trick (the toilet might be rather funky, and the "air" scrubber as well)

just a thought


simplybarry
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posted May 15, 2002 00:02
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WOW I am out of date.  I was not aware the U-deep divers were breathing anything other than gas mixes.

The system I am talking about is essentually living inside a water balloon (see local splash thread for samples and sources).

I saw 2001 when it first came out, didnt AC Clarke have a fetus inside its amniotic sac somewhere in the film?

The ship would be a giant placenta (shades of Woody Allen) with the crew floating in fluid and attached by ambilicals.


Une Fois
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posted May 15, 2002 00:07
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It appears the point being missed here is that the body's tissues *themselves* differ in density.  That means that even if force is perfectly evenly or at least smoothly distributed across the body's surface, even if the tissues are saturated with any kind of fluid, there will be immense shear forces.

Over time (and maybe not even very much time) under heavy acceleration, bones and cartilage (denser than the rest) will tend to sink to the back of the body, and fat (the least dense) will tend to separate and buoy to the front of the body.  Not a pretty picture.


Caulkhead
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Dont think cryogenics work.
Those people who paid mega-cash to be frozen have wasted their money.
There is still deterioration however quickly deep-freezing occurs.


simplybarry
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posted May 15, 2002 01:10
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Une, in a pure hydrostatic regime the is no up-down, front-back...
Time to get out the sketch pad and do some free body diagrams.

If we use consider two bodies of of different mass and then change the gravitational attraction the following is clear.
Since force (weight)=mg and the mass is constant the force is propotrional to the force of gravity.  F~g

Now change to an inertial regiem and replace gravity with acceleration.
F=ma, and since mass is constant the force is proportional to the acceleration.  F~a

Now bodies of different density will have different mass/inertia (per unit volume).

So if they are both subjected to the same gravity/acceleration the do not have any differential force.

Stepping outside the inertial frame we see that a blob of light oil, a blob of liquid mercury and a chunk of lead all fall/accelerate at the same rate (thanks Newton)

My argument is that a light organ sitting beside or under/over a denser organ would accelerate at the same rate--therefore no force differential, no shear force.

But then his brilliant facade crashes and spills across his keyboard...but then we use a centrifuge to separate the cream from the milk?

This is fun and begs further investigation...perhaps we ought to refer the matter to one of the new moderators eh?


Une Fois
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posted May 15, 2002 01:47
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Sorry, SB.  If you have a less dense object suspended in a denser fluid, the two together in a gravitational or accelerative field, the light object will migrate against the gravitational or with the accelerative field vector.  Boats float.

Likewise, a denser object in a less dense fluid will migrate in the opposite direction.  Rocks sink.

Under acceleration, the bones, tissues, and fat do indeed accelerate at approximately the same rate, but that doesn't mean the forces between them are zero!  The forces differ by the difference in densities, and that is what causes the body parts to shear or to tend to separate.

Hydrostatic force is not relevant: by definition you cannot accelerate an object by hydrostatic force.  Period. 

That one immerses the object to be accelerated in a fluid also changes nothing.  There will always be shear (well, tension if they lie along the accelerative axis) between proximate, accelerated objects that differ in density.


Caulkhead
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Not convinced that mass is constant when accelerated.
Or is that only relative to an observer?


simplybarry
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posted May 15, 2002 04:20
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Good points Une, this is a facinating problem but Im gonna have to think some more before I conceed the point.
I have a nagging feeling we have overlooked something fundamental...tink boyant force!

Skyfleur, could you moderate this for us?

Caulkhead in Newtonian Physics mass is constant.  In Relativistic Physics mass does increase but this is only significant at ~96 percent of the speed of light.  Please let us keep it Newtonian the math (its only Algebra) gets messy.  Besides the energy required to accelerate mass to light approaches infinity.


Scribe
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posted May 15, 2002 05:41
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quote:
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Originally posted by simplybarry:
....Skyfleur, could you moderate this for us?

.
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You guys don't need Moderation - this is what a discussion should be about!  We should get the whips out to keep you at it and working faster.

PS wasn't there some form of 'statis' field the SF writers used to overcome this?

Also how long does it take to reach light speed at a constant 2g of acceleration? 


Jack007
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posted May 15, 2002 06:36
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OK,
Only now I am drunk enuf to get in this discussion.  Unfortunately it is irrelevant.  You CAN'T do this with current physics.  But I would give my future children to be wrong and YOUR future children also....chaulkhead the acceleration is constant so your original idea(which I can't remmeber) wouldn't work.  However the deep sea diver type might be right.  If we go to space immersed in water or another like substance we might be able to deal with the great G forces (which are worse than way below sea level forces.  I admit I have no science and formulas to deal with here just some experience with the NAVY deep sea diver types (they are the guys who MADE the diver tables).  Please PLEASE though if we are wrong someone let us know cause I ain't been exited about space travel in a while (and I LOVE the stuff and want so bad and would give up everything I own to do it!)
thanks all serioius responders.


Sami
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posted May 15, 2002 08:41
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I might be a bit off the point, but I'm not sure where do you need acceleration much more than 1G (or a bit more, 1.3G may be comfortable enough, 2G definitely is not for a long period of time).  If you can accelerate/decelerate at 1G you can go around the solar system nicely; sure, it takes two or three weeks to go to the outer planets, but how often do you need to go there?  I don't travel to the other side of the world more than once or twice a year, most of my trips are much shorter.  If you accelerate more you have a bit higher top speed, but since the distance is short the average travelling time would not be significantly shorter.

If you want to go to the stars higher acceleration would help, but not that much.  Accelerating at 1G you would hit light speed in 354 days (which is not possible, so you would hit your actual top speed earlier).  If you are going to nearest star Alpha Centauri (4.3 ly away) at 1G it takes 2.3 years, at 2G 3.6 years ship time.  Your top speed would be 0.95c and 0.98c, respectively.  If you are going really really far, say, galaxy center (30000 ly), it takes 20.0 years at 1G and about half the time at 2G. In that case you have travelled practically all the time at ~1c and accelerating 100G won't do much difference.

I think that while fast acceleration would be nice, it is not that important.  Even 1G takes you anywhere you want to go.  It's the matter of costs and benefits.  Just look at the flight travel today.  People prefer to sit on the plane a while longer rather than pay more for higher speed.

The real difference would be if we could travel faster than light.  Maybe that is possible, but not by *accelerating* beyond it.

My two c's


upquark
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posted May 15, 2002 09:03
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quote:
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Originally posted by Une Fois:
For space travel, the obvious preventive measure would be structural surgery on the traveler before space travel to rebalance translational forces, in turn to minimize shear.  In essence, inserting a fairly large amount of scaffolding throughout uncomfortable regions of the body.

You first.
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What an interesting concept!  So we recruit Wolverine from the X-Men, stick him in a high-acceleration vehicle of some description, light the blue touch paper and retire.  Result: Wolverine's artificial skeleton stays put; rest of Wolverine is spray-painted onto the back wall of the vehicle.  (OK I know you meant more than an artifical skeleton but the imagery was good - thanks!).

Une, isn't this Heath Robinson method of julienning a carrot?  Or a human?

If anyone's read a book called Macroscope by Piers Anthony (won some SF prizes years ago) he postulated a method of enabling humans to survive extraordinary accelerations by a machine-induced "reverse evolution" which created, well, I guess, soup out of the unfortunate traveller.  Reconsititution resulted in the human climbing out of the vat after arrival.  Hmmmm.

The potential effect of a stray high-energy particle on the soup doesn't bear thinking about! 


Stephen Brooks
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posted May 15, 2002 12:07
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quote:
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Originally posted by Sami:
Accelerating at 1G you would hit light speed in 354 days (which is not possible, so you would hit your actual top speed earlier).  If you are going to nearest star Alpha Centauri (4.3 ly away) at 1G it takes 2.3 years, at 2G 3.6 years ship time.  Your top speed would be 0.95c and 0.98c, respectively.  If you are going really really far, say, galaxy center (30000 ly), it takes 20.0 years at 1G and about half the time at 2G. In that case you have travelled practically all the time at ~1c and accelerating 100G won't do much difference.
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Yes that's partly what I had in mind: very long trips are _just_ feasible in the human lifespan due to time dilation, although in the example of travelling to the centre of the Galaxy in 20 years, it would evidently be 20 of your years but 30000 years for people back on Earth (just thought I'd clarify that for people who haven't recently done a course on relativity).

The reason I thought 20G would be good if it was attainable (by my magnetic compensation system or some other such) was because although it would only speed up non-relativistic journeys (e.g. within our own solar system) by a factor of sqrt(20) or about 4½, it would speed up the crew-time for relativistic jouurneys by a whole factor of 20 because you reach light-speed that much quicker.

This would make the difference between a 3-year journey to the nearest star and a 5½-month one (not the full factor of 20 in this case since we're not _fully_ relativistic for that short-ish journey).  From the human perspective, there is a big difference between 3 years and 5½ months: to the extent that I'd volunteir for the shorter journey but not the longer one.

It also gets really quite cool when you consider longer trips.  A journey with a crew-time of 16 months at 20G would get you to the galactic centre.  Again, I'd prefer this to 20 years.  The main reason people would not want to go on a trip like that is that they would return to Earth (if they tried to) some 60`000 years in the future.

However I suppose one possibility is that you _start_ on such a trip and are then overtaken by warp-speed ships several months in, after the people back home have invented them!

[Note for anyone who finds the crew-time figures in the above a little "strange": when the acceleration gets into relativistic speeds, the crew time distortion works out so that crew-time vs. distance travelled is actually a logarithmic curve, which bizarrely compresses the timeline so that you can get anywhere in the universe within a few years.  Accelerating at 20G you'd get outside the visible universe in 16 months (the 16 month figure for galactic-centre was longer due to having to stop again at the other end).  Even accelerating at 1G you'd get outside it in 23.3 years.]


simplybarry
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posted May 15, 2002 22:32
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Une, I conceed but dont understand the why.  We see this is hydro-cyclones and ultra centrifuges and I guess a good example beats flawed logic every time.

There is still something nagging me here though.


skyfleur
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posted May 15, 2002 23:12
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quote:
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Originally posted by simplybarry:

Skyfleur, could you moderate this for us?


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Like Scribe said, no moderation needed here
If moderation was needed, you know the drill, PM all the mods

Not to be a blonde or anything, but I thought that if science fiction series showed people travelling in space, it meant that some scientists were actually working on the stuff and thus implying it should be possible.  Like teletransportation has been examined for the past 40 years or more, right?

And another question, what's the G force exerted on astronauts/cosmonauts/spationauts?  just that I had some idea as to the scale you're talking about. 


Une Fois
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posted May 15, 2002 23:22
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Stephen Brooks: I think there is a bit of a catch here, though. 

I have Newtonian physics pretty well in hand (I know, a dinosaur), but not relativistic, still: I can't see how the 20G acceleration can be a given.  Doesn't the increase in mass require proportionately more energy to accelerate as the speed and mass increases?  And doesn't this preclude achieving 20Gs at unlimited speeds with any engine of finite energy output?  Help me out, please, if I've got it wrong.


numist
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posted May 16, 2002 01:26
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there is one thing you have all missed, correct me if Im wrong

The faster your velocity, the more gravity is produced by the objects in motion.  This means that if you did accelerate constantly, your personal gravity would eventually crush you.  This would happen before you reached .8c, but if you were planning on going a long way, this is a serious problem.  not only that, chances are that soon after you implode, your ship would too, as the forces of gravity generated by objects in high motion are huge.

Id sooner fly a cessna into deep space

scott


Une Fois
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posted May 16, 2002 01:30
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And I guess my point has been: other effects will kill you long before the slightest gravitational difference could be detected.


simplybarry
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posted May 16, 2002 02:05
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Skyfleur: One aspect of science/technology is trying to get the imaginary/magical to work--early space advocates thought of shooting people into space in giant guns...A typical modern gut with a range of ~20 miles imparts about 40,000 g to the shell.  A projectile to the moon would be many many times this.
Recent discoveries in Quantum Mechanics-Dynamics give some tantalizing clues that teleportation may work for small inanimate objects but QM is so weird I douldnt count on it.
If my memory serves me well g max for shuttle launch is about 4-g and is in consideration for the shuttle not the astronauts.  I could look it up or calculate it but not tonight other things on my mind.

Scott: Gravity is a universal force of attraction between all objects having mass but unlike the electromagnetic force it's is always attractive, never repulsive.
The universal gravitational constant big "G" is known to 10 or 12 decimal places and according to conventional wisdom both universal and constant.  I dont recall any mention of relativistic changes in G but I dont know Jack!

a Une Just getting the bags checked and through the security gate would consume several lifetimes.


numist
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posted May 16, 2002 03:58
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it was tested and determined that gravity is exerted between objects and on the object itself.. Thats why fusion in stars is posible, because of the imense gravity caused by the large mass of gases there.  It does work between objects, but it also works on the object, it would cause things (and people) to implode.  Besides this, your memory serves you quite well. 

and quantum mechanics only really works with small and mostly random particles, I dont think we can count on it at all...


ISEN
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posted May 16, 2002 13:49
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On the gravity note, have we invented artificial gravity yet ?

Interstellar travel will hold astronauts in zero gravity for very long periods of time, during this time the bodies muscles tone will waste away and leave the astronauts unable to move on a planets surface i.e. within an atmosphere.  How do we deal with this 'little' problem. 

Would a Babylon 5 approach work, with the spinning station creating it's own gravity ?

Would the Magnetic boots approach work, as in 'Enterprise' ?

What are viable solutions to this problem ?


Low tech village idiot
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posted May 16, 2002 14:51
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Basic problem with plain old acceleration upto G forces:
Inertia and what has been mentioned above.
Your body wont stand the pressure and is further magnified by wanting to stay in one place and not moving.
This will never be solved until either Inertia is totally removed or dampened somehow.
Another Sci-fi way would be to slip into an alternate universe where light traveled several times faster, and accelerate at 1G over there. 
Again, its only a thought


Stephen Brooks
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posted May 16, 2002 15:15
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quote:
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Originally posted by Une Fois:
Stephen Brooks: I think there is a bit of a catch here, though. 

I have Newtonian physics pretty well in hand (I know, a dinosaur), but not relativistic, still: I can't see how the 20G acceleration can be a given.  Doesn't the increase in mass require proportionately more energy to accelerate as the speed and mass increases?
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Nope, because in your _own_ instantaneous reference-frame, you are only needing to produce a 20G or 1G acceleration.  The "mass increase" only is applied to objects which are not travelling in the same reference-frame as you are.

If you consider things in the rest-frame of everybody _else_, then they _do_ see that your spaceship has increased greatly in mass.  However, the spaceship is also travelling VERY close to the speed of light (c) already, so in fact it does not need to accelerate much at all.

In the limit of speeds close to c, if the mass has increased by a factor gamma then the speed achieved will be approximatey c - 0.5*c/(gamma^2).  The "gamma^2" is the important bit, since it means that the difference in velocity between you and c is decreasing _more_ than in proportion to how your mass is apparently increasing.

Sorry I couldn't give an explanation without going into equations, but it's one of those things (see the geology in the Creation Science thread!) that you can't argue properly about unless you do it quantitatively.


quote:
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Originally posted by Numist:
The faster your velocity, the more gravity is produced by the objects in motion.  This means that if you did accelerate constantly, your personal gravity would eventually crush you.
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No I don't think it works like that: in each non-accelerating reference-frame (whether it is travelling near the speed of light relative to others or not), the laws of physics are consistent and identical to those at rest - or at least that's what relativity says, and that theory has been tested quite stringently.

The physics in operation in your accelerating frame of reference will simply be the physics you'd get back on Earth if you were accelerating at 20G or 1G. The large constant velocity you are going at doesn't come into it because there is always a "nearby" frame of reference (what I called the instantaneous rest frame above) which has physics identical to the at-rest frame and differs from the spaceship's frame only by a 1G acceleration.

However physicsists have still been on the lookout for defects in relativity at _really_ close to the speed of light since we cannot test the _very_ limits ourselves.

There is one thing about gravity that I think _might_ become important in this proposed mission, but only at the very highest velocities, and that's gravitational shearing caused by flying _Very_ rapidly through regions near things like superclusters of galaxies in which space is warped somewhat.  It's on a sufficiently vast scale that it's essentially undetectable curvature in any normal situation, but if you're whizzing past galaxies by the minute, it'd probably start causing you problems.

In some places in the universe, space is actually _visibly_ warped: there are these "lensing" phenomena, but also if you could "see" the space like in one of those black-hole diagrams, it would be definitely bendy (and the bend would be fairly noticable on the diagram to human eyes).  This is because some galaxies and galaxy clusters have 10% of the mass required to actually become a black hole!


Stephen Brooks
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posted May 16, 2002 18:41
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quote:
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Originally posted by ISEN:
On the gravity note, have we invented artificial gravity yet ?
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Oh yeah.  I've been inside a device that changed the gravity I felt between about 0.5G and 2.5G-ish.  I'm sure quite a few of the more adventurous around here have too.


quote:
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Originally posted by ISEN:
Interstellar travel will hold astronauts in zero gravity for very long periods of time, during this time the bodies muscles tone will waste away and leave the astronauts unable to move on a planets surface i.e. within an atmosphere.  How do we deal with this 'little' problem.
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Aha - in this thread we've actually got the opposite problem.  The proposed space missions (outer planets in weeks, other stars in months/years) are done under the assumption that the rocket's engines fire enough to give an acceleration of 1G _all the time_, as that's the only way to get to these high speeds.  I wanted 20G because it would be that much faster, but needed a way to actually _reduce_ that gravity so people wouldn't get squished!

So basically the spacecraft in these will be accelerating, so the crew will feel gravity with "down" in the opposite direction to the acceleration vector.


quote:
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Originally posted by ISEN:
Would a Babylon 5 approach work, with the spinning station creating it's own gravity ?
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Yep, that's fine, but if you make the rotating thing too _small_ you get "error" forces (corriolis) which will tend to make you move a bit sideways if you jump up in the air, etc.

One of those systems is going to be installed on the International Space Station in 2006.


quote:
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Originally posted by ISEN:
Would the Magnetic boots approach work, as in 'Enterprise' ?
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That'd stick your feet to the floor.  You'd still have the slightly-odd 0G feeling though because the rest of your body would not be feeling any gravitational force.  Magno-boots are fine for doing stuff like EVAs when you don't want to fall off, but (1) it might not stop the bone-degradation problem, or at least not entirely and (2) systems like that can't be used for inertial damping (like I'd need for the 20G acceleration) because they only act on the surface of your body and don't equalise the internal forces (what Une Fois calls shear). 


quote:
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Originally posted by SimplyBarry:
early space advocates thought of shooting people into space in giant guns...A typical modern gut with a range of ~20 miles imparts about 40,000 g to the shell.  A projectile to the moon would be many many times this.
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In various TV dramatisations of that guy's idea (I think it was H.G.Wells), the "gun" is depicted more as a long tube >20m length, so the acceleration is spread out a bit.  I'd admit that propelling people like that with explosives would almost certainly not work!  However, NASA are looking into the possibility of having a maglev system (a mile or two long) that accelerates the launch vehicle up to Mach 0.8 (in about 10 seconds!!  so 2G) before it even starts climbing off the ground.  A system like this which is also inclined (i.e a big ramp) would give the craft even more of a boost to get off the ground, and this would cut on-board fuel considerations etc. etc.


necronomicon
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posted May 16, 2002 19:22
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Ok Mr Brookes this is the kind of sad thing that I spend my daytime thinking about.

You have to think further ahead than the above - firstly I truelly believe that this obsesion we have with expending vast quantities of energy etc to get from A-B is a complete waste.

Proove to me that there is a difference between me being sat here and you being sat where you are - add energy to the system and you have created an imbalance (we call it travel - I think that it is wholey uncivilised and bad for our sense of well-being).

That aside and based on what we know at the moment we have to remove the mass from the human body - so suck the Higgs Bosons out and then put them back after.  ( I like bosons their great!  )


Stephen Brooks
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posted May 16, 2002 20:48
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quote:
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Originally posted by necronomicon:
You have to think further ahead than the above - firstly I truelly believe that this obsesion we have with expending vast quantities of energy etc to get from A-B is a complete waste.
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It probably is, but it would get kind-of dull if we never went into space.  'If we stay on one planet long enough we'll destroy ourselves somehow' is the way I see it.


quote:
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Originally posted by necronomicon:
Proove to me that there is a difference between me being sat here and you being sat where you are
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Yeah but you don't _want_ to be where I am because it's probably at least as dull as where you are.  If there was somewhere genuinely interesting to go it would probably be worth it.  (I travel to the duckpond, for instance, to look at the ducks, because I like ducks).


quote:
--------------------------------------------------------------------------------
Originally posted by necronomicon:
That aside and based on what we know at the moment we have to remove the mass from the human body - so suck the Higgs Bosons out and then put them back after.  ( I like bosons their great!  )
--------------------------------------------------------------------------------

I personally prefer Goatals as a means of travel.

Higgs Bosons only _disappear_ at energy densities present in the first 10^-35 seconds of the universe, so like a lot of other things that sound like good ideas, they actually only turn out to make good microwave ovens. 


necronomicon
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posted May 16, 2002 22:24
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"Oh duck" purved me worng again !

science wasn't one of my strongest subjects!

how about this though -

you eat a 25kg bag of powdered iron then jump into a magnetic field that suspends you intact untill journeys end ( If you were a woman you could set the magnetic field to shake you "washing machine style" for the duration of the journey!  )

hehehehee


rynther
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posted May 16, 2002 22:51
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Well, lets see, so far we have a hyper-alloy chasis, that will spray paint you to the back of the capsule, iron filings and a big magnet that will spray paint you onto the front, and liquid immersion, that might get you 3g instead of 1.3g, but nowhere near 20g.

just a minor question, if relative shear is really that bad, then how can you go jogging?


rynther
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posted May 16, 2002 22:54
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those iron filings would REALLY want to go visit that large attractive magnet across the room, and leave you looking like a large pincushion


necronomicon
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posted May 16, 2002 23:07
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quote:
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Originally posted by rynther:
Well, lets see, so far we have a hyper-alloy chasis, that will spray paint you to the back of the capsule, iron filings and a big magnet that will spray paint you onto the front, and liquid immersion, that might get you 3g instead of 1.3g, but nowhere near 20g.

just a minor question, if relative shear is really that bad, then how can you go jogging?
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ok so we have to genetically modify ourselves so that we have greater resistance to tear / tear propogation - I suggest that instead of eating iron fillings we eat iron impregnated kevlar then jump into the magnetic field !

Upon arrival we eat prunes to purge ourselves of the gook then go rambling!



rynther
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posted May 17, 2002 00:07
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besides, as long as we're borrowing the "mister fusion" (from back to the future), why not grab a flux capacitor while we're at it, and loose the relativity difference when we get back?


rynther
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posted May 17, 2002 00:43
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"....thanks for flying united intergalactic, we hope you like prune juice"


HETTATLONGUN
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posted May 17, 2002 03:13
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..."Just a reminder for your return trip: The Restrooms only take French Francs."


ISEN
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posted May 17, 2002 10:15
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What kind of propulsion do we have to play with at the moment ?

Nuclear reactors

Plasma drives

fission

What are the pro's and con's of each ?
Stephen Brooks
2002-05-22 12:40:30
Caulkhead
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Horse and cart is far more pleasant!

How about as an info package, rather like a hologram, fired by laser to the required destination.
Only trouble is, some sort of descrambling receiver would probably be needed at the other end.
And some sort of energy boosters might be needed on the way...and, wish I`d never started this!


Stephen Brooks
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posted May 18, 2002 00:29
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quote:
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Originally posted by ISEN:
What kind of propulsion do we have to play with at the moment ?

Nuclear reactors

Plasma drives

fission

What are the pro's and con's of each ?
--------------------------------------------------------------------------------

Nuclear reactors _are_ fission so far as I know.  They are actually excellent and the best powersource we have available at the present day.  However, right now people really don't like rockets being launched with radioactive payloads because of the fear they might crash.  Despite this, NASA is ploughing ahead with developing new, safer fission propulsion systems.  Once they're here, we'll be able to send probes to the outer planets rather quicker - I dunno what the implications for human spaceflight will be - it could concievably make the trip to Mars much faster.

Plasma drives... Well there are ion drives, which were first tested in space by the probe Deep Space 1, launched 1999 (I think).  This test was a complete success.  Ion drives provide less thrust than conventional rocket propulsion, but for a _much_ longer time (so higher top speed) and with _much_ lighter fuel.  These will be used for interplanetary missions.

Another sort of plasma drive that's being considered (but for about 40 years' time) is a direct fusion drive, where instead of a chemical reaction at about 3000°C in the rocket's exhaust cone, there is a nuclear fusion reaction going on at about 3 million °C . This is a very cool concept, as the fusion drives will go extremely fast and use very little fuel.  In fact the fuel that they do use will be gases that are common in space anyway.  The only method of propulsion known to science that is more powerful than fusion (per kg fuel) is a matter-antimatter reaction.


necronomicon
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posted May 18, 2002 05:49
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Um < sticks head in thread >

ALH 84001

before we go interstellar lets go to Mars!



Stephen Brooks
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posted May 18, 2002 16:49
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That's not Mars that's Io.  Mars is more of a uniform red colour. 


evy
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posted May 18, 2002 16:59
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wasn't Io the one where the probes found the volcanoes?
or do i have my moons all messed up now
or was Io the one most likely to host some for of life
no that was one of Saturn's
Titan that's it
still....nice picture though



Stephen Brooks
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posted May 18, 2002 18:10
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quote:
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Originally posted by evy:
wasn't Io the one where the probes found the volcanoes?
or do i have my moons all messed up now
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That's right - Voyager went past and got a rather famous photograph where a volcanic plume was visible coming up off the edge of Io.


quote:
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or was Io the one most likely to host some for of life
no that was one of Saturn's
Titan that's it
still....nice picture though

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Well actually, Europa, the 2nd major moon out from Jupiter (Io is the innermost, the vulcanism being caused by the strong gravity there) is quite a good candidate for life because people now think that under its ice surface there is an ocean of liquid water.  The water is liquid for the same _sort_ of reason as Io is volcanic, but the heating effect is less strong because Europa is further out.  Titan (around Saturn) is another good candidate for alien life, but for a different reason: it's the only moon to have a substantial atmosphere.  It has an orange one which no probe has yet been able to see through.

NASA has planned landers/orbiters for both of these moons for launch in the next 10 years or so.


quote:
--------------------------------------------------------------------------------
Originally posted by Caulkhead:
How about as an info package, rather like a hologram, fired by laser to the required destination.
Only trouble is, some sort of descrambling receiver would probably be needed at the other end.
And some sort of energy boosters might be needed on the way...and, wish I`d never started this!
--------------------------------------------------------------------------------

Well 80 years ago people would have said similar things about transmitting packets of information all over the world through the internet...


evy
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posted May 18, 2002 18:34
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quote:
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Originally posted by Stephen Brooks:
That's right - Voyager went past and got a rather famous photograph where a volcanic plume was visible coming up off the edge of Io.
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yep i saw that documentary in the days i still wanted to be an astronaut (give me a break i was 8 or so my sense of reality was in even worse shape than it is nowadays)
i remember being very jealous of the people working with voyager


quote:
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Originally posted by Stephen Brooks:
NASA has planned landers/orbiters for both of these moons for launch in the next 10 years or so.
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i thought cassini/huygens was an ESA project but then it could be that cassini is sent by NASA and ESA only contributed huygens (that's the one going to be dropped into the athmosphere of titan i think)
now i suddenly have trouble remembering whether these missions were scrubbed due to lack of funding or were actually launched
i am getting old


Stephen Brooks
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posted May 18, 2002 18:39
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They'd have difficulty scrapping Cassini-Huygens considering it's currently about 60% of the way from Jupiter to Saturn. 

Present position:


Yes, the Huygens probe is intended to land on Titan's surface, although a lot of the instrumentation is going to be used for looking at the atmosphere.  I think when they say a "Titan lander" they might mean a successor to Huygens with a bit more functionality.  Probably higher up their list of agendas is some sort of Europa probe - definitely an orbiter, but they're also talking about systems where a lander could "melt its way through" the ice by producing heat, and then swim about in the ocean below.


evy
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posted May 18, 2002 18:51
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thanks


Room 101
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posted May 18, 2002 21:08
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quote:
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Originally posted by Stephen Brooks:
That's not Mars that's Io.  Mars is more of a uniform red colour. 
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hehehehe < wooops > I just thought that it looked nice!  I could make it red-er if you like !


Stephen Brooks
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posted May 19, 2002 14:42
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This is what Mars looks like.



BTW, that image with the Cassini position, above, is updated on the NASA server so it'll update on this thread in real time!  Cool or what? 


evy
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posted May 19, 2002 14:45
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quote:
--------------------------------------------------------------------------------
Originally posted by Stephen Brooks:
Cool or what? 
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we aren't allowed to use enough cool 's to express just how cool that is


Scribe
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posted May 19, 2002 16:35
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quote:
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Originally posted by Stephen Brooks:
.....In fact the fuel that they do use will be gases that are common in space anyway. 
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Also intended that they could use a hydrogen 'ram' drive by scooping up the hydrogen as they boost along.

There is also the 'light sail' ship - very low mass - using the photon pressure on the 'sails' which are miles in area. 


Stephen Brooks
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posted May 20, 2002 01:21
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quote:
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Originally posted by Scribe:
Also intended that they could use a hydrogen 'ram' drive by scooping up the hydrogen as they boost along.
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Hmm.  I did some calculations on this way of doing things based on the interplanetary particle density and the "scoop" had to be rediculously large (1000km across) in order to work!  However I probably got it wrong somewhere.  Do you have any links to articles about this?


quote:
--------------------------------------------------------------------------------
Originally posted by Scribe:
There is also the 'light sail' ship - very low mass - using the photon pressure on the 'sails' which are miles in area. 
--------------------------------------------------------------------------------

Those are quite good - apparently if you make them big enough they can get up to like 10% of the speed of light.  However the big sail sounds like a real engineering problem!


Scribe
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posted May 20, 2002 05:37
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quote:
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Hmm.  I did some calculations on this way of doing things based on the interplanetary particle density and the "scoop" had to be rediculously large (1000km across) in order to work!  However I probably got it wrong somewhere.  Do you have any links to articles about this?

--------------------------------------------------------------------------------

Correct Stephen, as I remember it there was a 'magnetic' scoop many miles in diameter as the hydrogen density was very low.


Gliuck and Rob
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posted May 20, 2002 11:09
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Magnetic scoop sounds like a good idea, but you could start with a rich reservoir of gaseous hydrogen (some hundred Kg should be enough), and then refuel as you go.
Also remember that friction in open space is very low, that nuclear fusion is extremely powerful, and that by a judicious trajectory planning you can exploit the planets' gravity to accelerate with no fuel required at all.
So a ram-fusion doesn's sound so unlikely to me.


ISEN
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posted May 20, 2002 12:29
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Aren't the russians planning on launching a probe with a solar sail, at some point soon ?  Even though the test flight failed.

Continuation of Cosmo1 project.


upquark
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posted May 21, 2002 08:43
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quote:
--------------------------------------------------------------------------------
Originally posted by Gliuck and Rob:
Also remember that friction in open space is very low, that nuclear fusion is extremely powerful, and that by a judicious trajectory planning you can exploit the planets' gravity to accelerate with no fuel required at all.
So a ram-fusion doesn's sound so unlikely to me.
--------------------------------------------------------------------------------



What do you mean by extremely powerful?  It was my (probably limited) understanding that any propulsive effect that can be had from fusion is limited to throwing a bunch of particles out of the back of the spaceship and that the effect of it was due to being able to run the power source for years at a time.  i.e. low thrust, but long time.  How is that different to an ion drive (I know ions are charged particles)?  Are you meaning using fusion (or fission) to superheat a something like water or methane to chuck out the back?

Does anyone remember the British Interplanetary Society solution which involved a vehicle with a large parabolic reflector on the back - by large I mean LARGE.  Propulsion was achieved by lobbing a stream of fission bombs out the back and detonating them one after the other inside the parabolic reflector.  Can you imagine being in something like that for more than 10 minutes and NOT emerging mad?

Pass the ibuprofen.........


Gliuck and Rob
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posted May 21, 2002 10:06
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I mean that by fusion you have a very high energy/fuel mass ratio.
You can use that energy as you wish, for instance to heat a fluid and let it out through a nozzle.
I don't think that using fusion as combustion is now used in rockets is feasible, but that would be cool: a high-energy jet of gas, mass decreasing in the ship mean a good propulsion.
Then, you can collect hydrogen all over the place with your scoop and compensate for what is let out.


ISEN
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posted May 21, 2002 12:03
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Posted this in the 'Chinese going to the moon' thread, but, it also useful here.  The idea once consructed etc. would make interstellar travel far more accessible and less costly, it would also allow us construct larger craft in space rather than on earth.  So what do we reckon to this idea;

Space Elevator


Trader Jimm
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posted May 21, 2002 12:14
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quote:
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Originally posted by upquark:

Does anyone remember the British Interplanetary Society solution which involved a vehicle with a large parabolic reflector on the back - by large I mean LARGE.  Propulsion was achieved by lobbing a stream of fission bombs out the back and detonating them one after the other inside the parabolic reflector.

--------------------------------------------------------------------------------

I remember reading about that in Analog long ago.
I'm assuming they gave up when they figured out how many headache tablets they would have to take along.


QuarkBomb
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quote:
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So what do we reckon to this idea;

Space Elevator
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I like it, I want one.

Isn't it true though that the only material currently available and strong enough for such a structure is diamond?

And what about weather?


ISEN
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posted May 21, 2002 13:56
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_______________________________________________
It comes as no real surprise that carbon has been elevated to the material of choice.  In the form of diamond, it shows record-breaking mechanical properties.  Diamond can't be spun into filaments, but there is a form of carbon that combines strength with length: nanotubes.  These tiny, hollow cylinders made from sheets of hexagonally arranged carbon atoms exceed the tensile strength of steel by at least a factor of 100. Even conservative estimates place their strength at 130 gigapascals, which surpasses the magic number by a comfortable margin.

So what's the catch?  (And there's always a catch ...) For a start, they're extremely expensive, clocking in at a cool $500 per gram.  They're also a little short at present, with even the best synthesis methods yielding tubes no longer than a few micrometres.  Bradley Edwards of Los Alamos National Laboratory in New Mexico, who led the other NASA team, has worked out how long nanotubes would need to be to form a viable composite material.  The figure he has come up with is 4 millimetres.

But there is hope.  According to Dan Colbert of Carbon Nanotechnologies, a spin-off from Rice University in Houston, Texas, the cost of making nanotubes is set to tumble.  At the moment they are produced by laser vaporisation of graphite, a process that yields small batches of pure product perfect for laboratory use but far too expensive for the construction industry -- let alone anyone building a space elevator.

But Carbon Nanotechnologies has a new production process called "high pressure carbon monoxide deposition", or HiPCO, which promises to be scalable, so production plants could be as big as you like -- and bigger means cheaper.  Colbert reckons that within seven years HiPCO will have cut the cost of nanotubes to just a few cents a gram, though he won't give details of how it works.

What about the problem of length?  Things might not be too bad as they stand.  Nanotubes have a tendency to "rope up", or stick together side by side, and the cohesive forces between them seem strong.  Good news.  But on the downside, roped-up nanotubes also slip and slide erratically against one another in a way we don't fully understand.  Nobody has yet measured the strength of a nanotube rope, but early indications are that the tensile strength is reduced by at least a factor of 3, putting it "right on the ragged edge" of what is needed for an elevator, Colbert says.

And when a multibillion-dollar project is at stake, what engineer would work on the ragged edge?  Perhaps the simplest solution is to find a way of incorporating nanotubes into a composite material like fibreglass.  The downside of this approach is that whatever material is used to bind the nanotubes together will dilute their strength.

The most elegant solution would be to produce continuous nanotubes extending the full length of the cable.  There's no doubt that such a material would be strong enough, but is it a realistic prospect?  At present no one knows how to join individual nanotubes together to make longer molecules.  But researchers are working on the problem, and Colbert believes there's a very good chance of success
____________________________________________

A quote from an article, was very long so I picked out this bit.  Carbon Nanotubes is the answer. 


QuarkBomb
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Rate Member posted May 21, 2002 15:21
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Buckminster Fullerine (probably spelt wrong).

Named after the guy who gave lectures on the concept of a molecule shaped like a football.

It was created as a bi-product in the oil industry for many years, without anyone realising it.

Scientists finally cracked the composition, THEN realised that it had been a bi-product for many years.

It's composition is C60 (assume the 60 is subscript) and is composed like a football (football as in the one you kick, not the one you throw!!)

It is created by super-heating diamond (somewhere in the region of the temperature of the surface of the Sun) and then sucking into some sort of machine that does something regarding pressure.

Is that a bad explanation or what?
I remember watching a few reports on it, but it was a few years ago and this is everything I remember.

They say it would be much stronger than diamond, and reckon because of it's shape it could take a nuclear blast (possibly).
I've not heard anything more about it in years!! 


Stephen Brooks
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posted May 21, 2002 17:45
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quote:
--------------------------------------------------------------------------------
Originally posted by Gliuck and Rob:
Also remember that friction in open space is very low, that nuclear fusion is extremely powerful, and that by a judicious trajectory planning you can exploit the planets' gravity to accelerate with no fuel required at all.
So a ram-fusion doesn's sound so unlikely to me.
--------------------------------------------------------------------------------

Yep, but actually I think fusion is _so_ powerful that planetary slingshots might not be a large factor in the final efficiency: what I mean is, slingshotting around a planet can only add to your speed (relative to the Sun) something of the order of the planet's orbital speed around the Sun.  You might do a U-turn and change direction with it, but your speed won't be increased by more than about half the speed that space probes currently achieve.


quote:
--------------------------------------------------------------------------------
Originally posted by ISEN:
Aren't the russians planning on launching a probe with a solar sail, at some point soon ?  Even though the test flight failed.
--------------------------------------------------------------------------------

Yeah, actually I think about 3 NASA missions are planned to use solar sails in various ways, the most ambitious being the "interstellar" probe.  That's going to get to a distance of about 1/200th of a light-year from Earth (8x further out than Pluto) in order to probe the end of the Sun's solar wind and the various shock-fronts that occur in space where the solar wind hits the flow of the interstellar medium.  Its solar sail will be quite large and the probe will pick up most of its velocity by sweeping _towards_ the Sun and then unfurling the sail where the wind is strongest. 

Here's a picture of the Russian's solar sail, with big gaps between the "segments" to stop them getting tangled when it unfurls.



Here's an artists conception of a much larger "centrifugally deployed" solar sail.  The sails need some sort of force to keep them rigid, and a very easy way to get this is to spin the probe slowly so that they "fly out" from it of their own accord.



More about the Interstellar Probe mission is available from this website.


quote:
--------------------------------------------------------------------------------
Originally posted by upquark:
What do you mean by extremely powerful?  It was my (probably limited) understanding that any propulsive effect that can be had from fusion is limited to throwing a bunch of particles out of the back of the spaceship
--------------------------------------------------------------------------------

Well that's how almost every sort of propulsion system works, including the fairly powerful chemicl rockets that accelerate strongly for short journeys. 


quote:
--------------------------------------------------------------------------------
Originally posted by upquark:
i.e. low thrust, but long time.  How is that different to an ion drive (I know ions are charged particles)?  Are you meaning using fusion (or fission) to superheat a something like water or methane to chuck out the back?
--------------------------------------------------------------------------------

No actually what I'd heard was that the "proper" fusion-rocket would actually sustain fusion IN THE EXHAUST CONE, and hence be a bit like a normal chemical rocket on steroids.  [NB: Gluick and Rob - it is feasible, or at least some at NASA think so]. It would also have a much higher fuel efficiency both because fusion is intrinsically more efficient and because the temperature in the rocket nozzle would be about 10 million degrees rather than a few thousand.  I'd imagine they'd use magnetics to prevent the plasma in the exhaust from melting the exhaust nozzle.


quote:
--------------------------------------------------------------------------------
Originally posted by QuarkBomb:
Isn't it true though that the only material currently available and strong enough for such a structure is diamond?
--------------------------------------------------------------------------------

As ISEN posted after that, carbon nanotubes are a viable alternative to that and are in fact a bit stronger in tension than diamond.  However...


quote:
--------------------------------------------------------------------------------
Originally posted by ISEN:
So what's the catch?  (And there's always a catch ...) For a start, they're extremely expensive, clocking in at a cool $500 per gram.  They're also a little short at present, with even the best synthesis methods yielding tubes no longer than a few micrometres.  Bradley Edwards of Los Alamos National Laboratory in New Mexico, who led the other NASA team, has worked out how long nanotubes would need to be to form a viable composite material.  The figure he has come up with is 4 millimetres.
--------------------------------------------------------------------------------

Have a look at this article!

"This new method produced nanotubes that measured 20 centimeters, much longer than conventional nanotubes, said Pulickel Ajayan."


ISEN
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posted May 22, 2002 13:53
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Pick an equatorial country we don't need and lets start building.......

Nasa - Space Elevator


quote:
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The timetable for construction of an actual space elevator hinges mainly on development of the carbon-based building materials.  While NASA is using a planning horizon of the year 2100, private-sector companies currently working on designs think an operating space elevator could be built by as early as the end of this decade. 
--------------------------------------------------------------------------------

end of this decade eh!!, that early.  Lets get the private-sector moving on this, the Nano-tudes are almost there, we could be in space before I die..........

[This message was edited by Stephen Brooks on 2002-May-22 at 20:52.]
Stephen Brooks
2002-05-22 12:43:27
ARrgh.  All that came out without any hyperlinks on it.  Please ask if you want one particlar bit of text made back into a hyperlink again because I can edit it in.  I just don't want to have to do ALL of them.

Update: I've removed people's signatures from all that at least.  The hyperlinks and pictures still need doing.

[This message was edited by Stephen Brooks on 2002-May-22 at 20:53.]
Kameleon
2002-05-22 14:54:37
Hi
Just thought I'd try to bring a bit of joy to your life 'cos you thought someone wanted to hold a serious discussion big grin
Stephen Brooks
2002-05-23 05:36:07
If you are able to produce infrastructure for space travel, then these problems can be avoided, especially by using gravitational fields.  One idea I had was to have a thick tube made of a very dense material (iron would do).  You could free-fall into one end of the tube, travel along the interior at very high speed (given by ½mv² = gravitation potential energy defecit for spacecraft) and then decelerate to a a slow speed as you came out of the other end of the tube.  The interesting thing about this method is that it essentially uses zero energy to get from one place to another and because the ship is free-falling, the passengers would not feel any force at all.

Your method with black-holes sounds alright until you realise that the black-holes would be orbiting at a more-or-less constant speed whereas being in the gravitational field of one would cause you to _accelerate_ towards it, so you'd eventually catch it up, which is not what you want to do!  You were right in the assumption that free-fall in a gravitational gradient is a way to get around the acceleration problem though.
K0r/\/f1@k€$
2002-05-23 13:49:38
That's a lot of interesting stuff there.  When I've thought about it, I have always tended to be more concerned with making space travel a commercial possibility.  This seems to me to be the only way of getting some kind of reasonable backing for it.  That means mining, as far as I can see.  Aren't there some asteroids with orbits between Earth and Mars?  If one of them could be located, and redirected towards Earth (without hitting it big grin) then the amount of metal available would be huge, not to mention a ready source of building materials present in space.
Thomas King
2002-05-23 14:31:43
quote:
Originally posted by K0r/\/f1@k€$:
That's a lot of interesting stuff there.  When I've thought about it, I have always tended to be more concerned with making space travel a commercial possibility.  This seems to me to be the only way of getting some kind of reasonable backing for it.  That means mining, as far as I can see.  Aren't there some asteroids with orbits between Earth and Mars?  If one of them could be located, and redirected towards Earth (without hitting it big grin) then the amount of metal available would be huge, not to mention a ready source of building materials present in space.


Yeah, but if NASA were in charge of that, they'd get the calculations all wrong and the asteriod would actually hit the earth, because they use inches or something.  If they could get it just to hit the part of abingdon where Chris Johnson lives, however, I would be in favour.

Grank grank!
Stephen Brooks
2002-05-23 15:06:08
quote:
Originally posted by K0r/\/f1@k€$:
That's a lot of interesting stuff there.  When I've thought about it, I have always tended to be more concerned with making space travel a commercial possibility.  This seems to me to be the only way of getting some kind of reasonable backing for it.  That means mining, as far as I can see.


Yes commercial backing is important - NASA are very much behind this (and far-term ideas are related to how they could come out of near-term goals).  What I mean is, NASA's main priority right now is reducing the cost-per-unit-weight of getting objects into space.  If you go to the Marshall Space Flight Center's page you'll find a lot on this, but basically

2nd Generation Reusable Launch Vehicle (RLV) - due to start running 2012 if possible.  Will be 10x cheaper than lifting stuff with the shuttle, mostly due to not having to have the external 1st-stage fuel booster - i.e. it is more of a "space plane".

3rd G. RLV, more advanced, could use hypersonics or "air-breathing" engines (reacting the oxygen in the atmosphere with fuel in the jet engine I think).  These should be 100x cheaper than the shuttle per kg.  Timeframe ~2025.

4th G. RLV.  1000x cheaper per kg than shuttle - that makes it more expensive than a plane, but not by so much any more.  Plans for this a bit vague at present - basically all the ideas they couldn't fit into the previous 2 timeframes.  Planned launch ~2040.

Space tether... even cheaper than the 4th gen craft, but quite a massive initial outlay to get it working.  Prices to go into space would then be comparable to plane flights.  NASA say they could well have one going all the way up to geostationary Earth orbit by 2100.
Mike Ellery
2002-05-24 13:00:37
increasing saftey is the other main priority for NASA right now in terms of a new shuttle/ways of travel. 

It seems that right now NASA is focusing on completing the ISS, there has only been one science/research mission for the shuttle this year (excluding the hubble repairs).  I think that this is ok though, since there will be so much more research done on the ISS, while there are a few science experiments being done right now...

http://spaceflight.nasa.gov/station/science/index.html

The main reseach components of the station wont be added till after "core-complete" status of the station is complete (STS-120) in September of next year.

back to the saftey and cost, they are testing new materials for future shuttles/objects that will go into space, there was a rack of materials attached to the exterior of the station to see how they held up, and there is also a mock-human that has sensors that detects radation to see how much that will be a problem for when we send people out of lunar-earth orbit.  These will help with new ways of traveling in space.

as for commercialism (sp?) in space, until we find cheaper ways to get up there, we need to find a way to pay for it.

Just a few of my ideas
necronomicon
2002-05-24 22:10:32
I noticed that the Buran is being sold off by the Russians for 6million dollars
sposed to be fully operational as well

hehehe cool eh - I might buy it - for weekend jaunts to the moon....

Boing!
necronomicon
2002-05-25 00:45:42
oops would have put this in the post above but 30min edit rule !



Boing!
Chris Johnson
2002-05-25 05:07:23
I think theres a way around the problem of flying into black holes - you go around them in a slalom pattern.  I think this also causes you to accelerate as you go.

Still, your pipe idea is probably better.  I haven't done the maths, but it seems to me that if the pipe is your gravitational source, the force exerted on you when you are say 1/3rd through it is very small indeed:

Warning: Bad ASCII art


              |                |
--------------------------------------------- <-- PIPE
              |                Me             <-- Hole in middle of PIPE
--------------------------------------------- <-- PIPE
 Segment A    |  Segment B     | Segment C


Only segment A is affecting me, and its a rather long way off, so not much acceleration
Chris Johnson
2002-05-25 07:36:07
Actually, I just have done the maths (heh probably wrongly), but I found that a person at the end of a very (infinitely) long pipe made of iron, 1m radius, 10cm thick is accelerated at 5.19*10^-7 ms^-2. For a pipe 100m long, the acceleration is 5.15*10^-7 ms^-2, so its the first few meters that make the biggest difference.  If my segments (above) are 100m long each, the acceleration in the middle is only 1.65*10^-9 ms^-2 at the point I show myself at, compared to 5.17*10^-7 ms^-2 at the end.  Either way, its bloody slow.

The other problem is that acceleration is proportional to the density of the pipe (kg/m).  Thus one would need a mighty fat pipe (3.5km thick for 1G acceleration in an infinite pipe) in order to do anything with this.

If I've got my maths right (which is about 50/50) then the pipe method is probably impractical.  However, I don't doubt that the flying black hole theory has a few problems too...

[This message was edited by Chris Johnson on 2002-May-25 at 15:45.]
Stephen Brooks
2002-05-25 10:46:33
The pipe would definitely have to be huge - I thought more like the mass of the Earth or something, but one thing it does demonstrate is that high accelerations _without_ being squashed are feasible.  The few-km thickness you suggest actually makes it an awful lot _more_ feasible than I'd first thought.

The idea of a "slalom" pattern with black holes has actually been used to contruct a theoretical scenario (called the "great escape") in which there are several pairs of massive binary objects (e.g. pairs of orbiting black-holes) moving in a circle (so a ring of pairs) and a particle that goes around this large circle (it may be several particles).  Anyway, each time the particle encounters a binary system, it is slingshotted and speeds up, taking energy away from the binary system (so that its components orbit faster and closer to each other).  Anyway, this continues, and in the _theoretical_ situation of point masses, the large ring gets larger, the particles moving around it get faster and the binaries themselves get closer and closer together.  The things that would stop this in the real universe are special relativity (can't go faster than c) and the non-point sizes of black holes.
Chris Johnson
2002-05-25 13:58:17
Actually, a revised calculation indicates 20km thickness for a 1G pipe.  Still, thats fairly acceptable in the scheme of things.
Stephen Brooks
2002-05-25 16:08:47
We could line up some iron-based asteroids and bore a hole through the middle.
Helix_Von_Smelix
2002-05-31 08:04:26
Question...... what would happen if you had a black hole at the front of the craft that was being accelerated to what ever speed at what ever G. What would the distance to the travelers have to be to counter the G effect.  i would think that it would have to change inline with the G. just a thought, just need to manage the energy!  or the black hole could be moved through hyperspace to a few feet infront of the craft, this jump forward of the black hole could be repeated rapidly to give motion........ easy when you write it down and ignore all the problems.  i shall now go away and hide...

If you make instant coffee in to a microwave do you go back in time??
Ben Whitten
2002-06-11 08:08:16
Well I'm not verry knolagable in these subjects but here goes, Arnt balck holes just big old stars that inplode to verry small size but still have the same mass?  if so ud be crushed if u where that close, hell if u where that close to the center to the earth (other that being burnt) ud be crushed aswell, and could u explain bout hyperspace and all that what-not, as for that idea a while back bout drinking some magnetic solution wouldn't it be beta to have a little magnetic suit of ancle or wrist braslets to hold u in suspention (suit would be betta cause ur then held all over), to that is my rambelings personaly I think by the time they have got all that fancy stuf like the reusable space craft thingy they would have perfected the gravity puls and anti-grav generator that there are working on now smile

well u can skip this section is u like cause I am MAD and tend to ramble
bradsercombe
2002-07-09 19:08:16
More spanners in the star-travel works

I remember reading a while ago that the faster you travel the shorter the apparent wavelength the radiation that you are travelling through becomes.  I don't necessary believe this (and don't have the tools to test such a statement) but it would mean if your destination was some other solar system, the faster you traveled towards that star, the higher energy its radiation output would appear to be.  So visible Light would be shifted to UV, Xrays to gamma etc.
kruemi [Swissteam.NET]
2002-07-10 02:30:06
quote:
Unfortunately, I think that travel beyond the solar system is not likely unless alien life is found outside it, simply because of communication problems.  Unless we can do something very odd with relativity, theres not a great deal we can do about a ping time of 8.6 years to Alpha Centuri.  Even Mars has a lag time of about half an hour.


Ok, with this lag it isn't cool to play Quake...
No, there could be a solution with quantum-physics!
If you generate a lot of Quantum-Pairs and transport halve of them to the destination.  Everytime you measure one quantum here, it will be the same way there... without lag!

So you only had to transport ernough of the quantums .-)

bye

kruemi

--
Don't read this.  And neither this!
bradsercombe
2002-07-11 02:36:05
Done some research and calcs.  There was a big DB of stars that I pulled down and sorted to get all the stars out to 50 light years (I made this limit as it is roughly 50 years ago that we started making loud EM noise - mainly sonar pings from submarines etc but that's not really relevant. 

Of the 1000 or so stars out to 50 lights IN THE DB (there may be more not in the D only 5 were G2V (sol-like) stars.  Further research said it would be possible for earth-like environments to develop around stars ranging from late F to Early K in spectrum so this increases the number of stars to 40-50.

Some other things you should know are the space shuttle (yes I know it's in gravity and atmosphere when it launches etc.) burns up 1.6 million kg of fuel (both solid and liquid) during it's 8.5 minutes of launch.  This accelerates it at 3G so by the time it's in orbit it's doing a whisker over 28,000km/h. The reason it does this is partly for the consideration of scientists and non-professional astronaut types (the moon shots used Astronauts and launched at higher Gs). 

Space shuttle engines are only rated to be used for 7.5 hours total.  The programme is trying to extend their re-usability to 50 launches.  But we all knew chemical propulsion was out anyhow.

The nearest G2V star is alpha centauri (beta is also close enough in spectra to possibly have earth-like planets, proxima is THE closest star but is not a contender).  Things are complicated there because alpha and beta get as close as 11AU to each other.... that would be good for humankind if there were possibly habitable planets around each, and IMHO the nearby star may act like Jupiter by attracting all the passing dross and help protect the rocky planets from bombardment.  10AU I think is enough distance so the radiation from alpha or beta centuri (whichever your theoretical planet is NOT orbiting) won't add too much.

I don't think ion engines are the go because if you want 1G of acceleration you're going to need a BLOODY HUMONGOUS ion drive to get it (each DAY the ion drive on deep space 1 added between 24 and 32km/h to the speed of the probe so acceleration was pissant).

It's really going to be fusion I think at this stage.  I read today that the last man on the moon said that there is the possibility of commercially mining the moon for Helium III to use in fusion reactors.  The time frame he mentioned was 10-15 years to put together something that may be commercially fesable.

Helium III is nice and light too- highly compressible and not explosive etc. etc. etc. but you might still need too much of it to carry around.  I mean that the crux of the problem is that you need reaction mass not just energy to create thrust.  Therefore you're either going to have to carry it with you or pick it up along the way a-la magnetic field-type ramscoop as someone mentioned earlier.  If you have shitloads of energy from fusion then you can make a big field to suck hydrogen from space, compress or accelerate it mightily then eject it as reaction mass.  2 x HeIII = 2H + He, no Oxygen sad to say.  You can make Oxygen from 2 x HeIV but it takes a fair chunk more pressure and heat to do it.

Question for the brilliant physicists (which I am NOT), if we accelerate at 1G to Alpha centuri (approx distance 4.395LY or 1.37848E^15m) - meaning by this that we have to decelerate at 1G once we hit the half way mark, how long does it take to get there (my answer came to 194 days) Also, what speed are you travelling at when you hit half way?  I started with an initial velocity of zero which is accurate enough considering the errors that are bound to be in my other calcs!

All the data for this ramble came from the net so take it with salt- lots of salt.  I did some cross-checking but still don't trust all of it.

Brad.
bradsercombe
2002-07-11 03:37:31
Oops.  Looks like HeIII+HeIII is not a really great fusion reaction.  For an interesting discussion of the pros and cons of possibly achievable fusion reactors try the following link:

http://home.earthlink.net/~jimlux/nuc/reactions.htm

Looks like D+HeIII might be more suitable for various reasons.  I have another project for you Stephen- create a distributed processing project that uses Genetic algorithms to design a fusion reactor.  I'd be in it.  I have about 30 1Ghz pentiums (plus a couple of 1Ghz Xeons and an E450) which do practically nothing for 80% of a day.

Sorry guys, but I'm more interested in something that is possibly achievable in my lifetime and I just don't see quantum physics coming to the party yet (if ever). 

Some other things I didn't take into account are that you are obviously travelling at multiples of C if you can get 4.3 light years in 190 days... you're likely to find that friction against even interstellar gas is significant.  Running into a warm fart could crush your ship.
Stephen Brooks
2002-07-14 08:02:27
quote:
Originally posted by bradsercombe:
The nearest G2V star is alpha centauri (beta is also close enough in spectra to possibly have earth-like planets, proxima is THE closest star but is not a contender).  Things are complicated there because alpha and beta get as close as 11AU to each other....


Now here's some confusing astronomical terminology if you've ever seen it: the binary companion to Alpha Centauri A is actually called "Alpha Centauri B", and Proxima Centauri is also known as Alpha Centauri C. Beta Centauri, on the other hand, is the second-brightest star in Centaurus (also known as Hadar) and is a blue-white supergiant star some 300 light-years away.

quote:
You can make Oxygen from 2 x HeIV but it takes a fair chunk more pressure and heat to do it.


4 x HeIV = Oxygen16, which happens in stars about to go supernova, usually via:

3 x HeIV = Carbon12, then HeIV + Carbon12 = Oxygen16.

(2 x HeIV = Beryllium8, which is unstable I seem to remember).

quote:
Question for the brilliant physicists (which I am NOT), if we accelerate at 1G -to Alpha centuri (approx distance 4.395LY or 1.37848E^15m) - meaning by this that we have to decelerate at 1G once we hit the half way mark, how long does it take to get there (my answer came to 194 days) Also, what speed are you travelling at when you hit half way?


Since this involves going close to the speed of light, you have to include the effects of special relativity into the calculation.  When I did a course on this, I made a spreadsheet for calculating just this sort of thing.  At 1G, it takes 3.55 years to accelerate to half-way and then decelerate again (so 1.78 years for each half).  But that's time as-observed-on-the-ship, so the apparent travelling more than 1 light-year per year is because of time dilation.  The people on Earth would observe that your voyage took more like 6 years (I seem to have lost the spreadsheet that works out that figure) and the top speed on that journey would be something like 90% of the speed of light.

For larger distances the time distortion gets more extreme.  You can reach anywhere in the visible universe at 1G in about 50 years of your time, but the _actual_ time will be around x+2 years where x is the light-years distance you travel.  The top speed will be very, very close to light-speed in most of these cases (99.999...% and the like).

quote:
Some other things I didn't take into account are that you are obviously travelling at multiples of C if you can get 4.3 light years in 190 days... you're likely to find that friction against even interstellar gas is significant.  Running into a warm fart could crush your ship.


Well you can't travel at multiples of c using the known laws of physics - if you kept on accelerating at 1G you'd just get closer and closer to c without exceeding it (but would feel like you were going much faster due to the increasing time-distortion).  Still, this doesn't negate the fact the ship would be running into interstellar gas at quite a rate.

As far as I know, no space mission so far has actually taken much notice of the drag effects of the interplanetary medium (which is somewhat denser than the interstellar medium) because they are small at low speeds.  It will be interesting to see at what speeds these start to come into play.

The density of the interstellar medium (ISM) where we are was quoted at 0.1 atoms/cm^3 on one website.  Going through that at approximately the speed of light, a frontal area of 1m^2 on the spaceship would intercept c*0.1*100^3 = 3*10^13 atoms per second.  Say those are hydrogen atoms (as is most likely) with a mass of 1.675*10^-27 kg each.  That makes about 5*10^-14 kg per second of ISM encountered.  This doesn't sound much, but when going at say 85%c, the kinetic energy of this stuff is about the same as its mass-energy, E=mc^2, so the energy of heating of the front of the spacecraft would be 5*10^-14*c^2 = 4500 Watts for each square metre of frontal surface area.  An electric bar fire is 1000 Watts of heat, so we see that this figure (appropriate for some speed around 85%-90%c) is not to be dismissed, but on the other hand it is not as big as the amount of heat a shuttle has to cope with on reentry.

If you go to http://spacsun.rice.edu/~twg/pc500.html it shows how the interstellar medium is not uniform.  We are lucky to be inside a 'bubble' of relatively-low-density ISM caused presumably by a supernova quite a long time ago.


"As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline"
Stephen Brooks
2002-07-14 08:10:33
One thing I probably should mention is that the best way to verify the risks of going through the interstellar medium is to run a probe through it first at lower speeds, make measurements of the heating etc. on it, and then scale those up to see what would be likely to happen at higher speeds.  I would not feel happy boarding a 85%c-rated ship based only on the ballpark calculations I did above.


"As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline"
bradsercombe
2002-07-14 18:05:56
Thanks for the corrections in my ramblings!  I am not personally convinced (being a non-physicist) that the speed of light is an unalterable barrier.  I remember reading somewhere that Eienstein said that the assumption that nothing can travel faster than light was essential to his models of physics but had not been proven.  Quantum physics seems to violate the assumption with the ability to transmit information between "entangled" particles instantaneously.  On a similar note, does anyone know if the time dilation effect of high speeds has been measured experimentally?
bradsercombe
2002-07-14 18:09:34
Thanks for the corrections in my ramblings!  I am not personally convinced (being a non-physicist) that the speed of light is an unalterable barrier.  I remember reading somewhere that Eienstein said that the assumption that nothing can travel faster than light was essential to his models of physics but had not been proven.  Quantum physics seems to violate the assumption with the ability to transmit information between "entangled" particles instantaneously. 

Seems that relativistic effects have been proven many times, not the least of which being a proof using the decay of cosmic ray muons!

http://www.prestoncoll.ac.uk/cosmic/muoncalctext.htm
Stephen Brooks
2002-07-15 16:39:18
I said you can't travel at multiples of c using the known laws of physics. I'm not convinced that the speed-of-light barrier is inpenetrable either.  The only trouble is, if you can go faster than light then most observations suggest that you can also go backwards in time and wreak havoc with causality etc. You are also correct that quantum effects apparently transmit "something" faster than light, although importantly this cannot actually be utilised to transport real information (or matter) faster than light.

One theory around at the moment suggests that at one point our universe collided with another in which the speed of light was different.  Particles could flip between those two universes, and hence exceed the speed of light in one of them.  Causality gets somewhat blurred in quantum theory, so it turned out that if you solved the equations with those possible faster-than-light and 'paradox' events included, you ended up not with a logical contradiction, but with a massive release of energy.  They say that was what caused the Big Bang.


"As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline"
kruemi [Swissteam.NET]
2002-07-16 23:51:08
Waht's about your mass, when you reach 90% 99%, 99.999% of c?  I thougt the mass will get bigger and bigger!  Wont this mean, you'll end up beeing a black hole if you're getting to fast?

bye

kruemi

--
Don't read this.  And neither this!
Stephen Brooks
2002-07-17 04:49:56
As measured in your reference frame (i.e. inside, moving with the ship), your mass will stay constant.  As measured by people at rest, you mass will appear higher, or at least your kinetic energy as measured by them will appear to be larger than ½mv² (the standard Newtonian amount), which by some physicists is interpreted as a mass-increase so that k.e. = ½Mv² with a larger M. I prefer to think your mass stays as m but the kinetic energy just increases by a different formula.

In other words (as far as I know) it is a myth that things will turn into black holes if they get close enough to the speed of light.


"As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline"
DrHanser
2002-10-29 07:23:22
I didn't have the time to read the whole thing, perhaps I will go back and look at it a second time, but I did see this and it got me to wondering.

quote:
The thing I was thinking of today was that if, before the flight, you were drinking water with a biologically inert but highly magnetic compound suspended in it, then by putting a magnetic field within the spaceship, force could be exerted on the compound (which would have to attain an approximately even distribution throughout you - the more even, the higher acceleration would be possible) and that would mean that you weren't going to be crushed against the floor any more because every part of you is being accelerated rather than you just being pushed from one side.


Could this be applied to artificial gravity scenarios?  Magnetism as opposed to current inertial models (spinning donuts).  This would suppose that the inert particle would have to be evenly dispersed throughout the body, within the very cells that make up a multi-celled living organism (as opposed to just the bloodstream, in a human's case).

One could then have a magnetic source in the belly of a spacecraft/station simulating gravity.  Because the magnetic particles are evenly distributed throughout the body, the force of the "gravity" pulls evenly on the whole body.  Granted, this scenario wouldn't help objects when they start floating around in zero-gravity situations, such as interplanetary travel, but I would think that it *could* help humans stay fit.

I would imagine this could also be modified in a case where gravity exceeds that of earth's gravity, could it not?  repulse rather than attract?  I would guess that it would have to do with the specific polarity and orientation of said inert particles.  Hrm.

--
The mark of an educated man is one who knows a lot about something, and a little about everything.
Stephen Brooks
2002-10-29 13:02:00
quote:
Originally posted by DrHanser:
Could this be applied to artificial gravity scenarios?  Magnetism as opposed to current inertial models (spinning donuts).


Yes, but to my knowledge, the inertial models are much "nicer" ways of getting gravity - i.e. they wouldn't require careful balancing of the concentration of a certain compound like my system.  The best proposal is to have a ship or station connected to one end of a ~10km long space tether (20km tethers have already been demonstrated in LEO and a 4km tether has survived years in the face of micrometeorite/debris impacts), and on the other end of the tether some sort of counterweight (another ship, or a small asteroid, or storage/garbage).  The reason this is good is that with a very long radius, the whole thing doesn't have to spin at a particularly high frequency to get 1G of gravity at the ends.  Slower spin means less likelihood of the astronauts getting motion sickness looking out of the window, and more "linear" gravity (i.e. it would stay at about 1G in the same direction for 100m or so, allowing a large ship to be built).  Also corriolis would be reduced - you wouldn't get pushed sideways by jumping up and down, as will be true on the ISS's small rotating module, if it ever flies (2006ish with funding).

Reason I used the much more 'cludged' magnetic solution for high linear accelerations is because you can't get around these with rotation tricks.

quote:
This would suppose that the inert particle would have to be evenly dispersed throughout the body, within the very cells that make up a multi-celled living organism (as opposed to just the bloodstream, in a human's case).


I thought of water so that the compound would 'osmotically' balance in most of the liquids in the body, although being into medical science you'll probably know more about the practicalities of how this would work than I do.  Unfortunately I think certain things (bone?) will contain much less water than others, which will limit the usefulness of this.


"As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline"
tron
2003-04-28 10:32:32
so what?  a high enough magnetic field would lead to a imperfect distribution of the iron in your blood- dead.  did i mention, that if you drink a magnetic substance your veins are forced to leave your organism in a very spectacular way...
Outtatime
2005-07-01 22:42:33
Hi all, i have heard of a new device, which our military uses that can decrease inertia and g force by up to 89 percent!!!  Its called the Magnetic Field Disruptor which is a plasma filled accelerator ring that is pressured at 150 times the force of gravity.  Our government uses it on their "disc" aircrafts.  Which are the ion powered aircrafts, which are powered by a nuclear Reactor.  The only problem is that their pilots are exposed to constant radiation and weightlessness.  This in turn can cause a huge aray of problems and can make it difficult for the pilots of these crafts.  People who see these crafts don't know what they are and think that they are Aliens visiting us but they really arn't!!!  These crafts as they call them are used as the ultimate defense weapon for our country against a nuclear invasion from other countries.  The reason why them have to be so fast is b/c they have to be able to catch up with the missles so that they can disarm them.  The discs are equiped with lasers that emit electromagnetic pulse upon contact that can scramble the circuits in these missles which will cause them to self destruct!!!  Sorry if i got off topic a little bit!!!!!!!!!!!
Stephen Brooks
2005-07-02 18:45:59
Would this have anything to do with the crop circles I saw coming back home the other day?

Regarding my other idea, I thought recently of another way of doing it, using electrically-charged insulating particles and an applied E-field instead of the B-field and ferromagnetic particles.  Not sure which of these would turn out to be better, though.
KT
2006-04-07 20:54:42
Interesting discussion.  first thing I thought of was NASCAR and forces the driver goes through on the track.  Also wonder if rotation would solve the problem.  Of course sheilding for Cosmic rays would probably keep the craft from approacjing any speed that will cause the concerns you have.

Also there is at least another set of physical laws that have yet to be discovered which when appliedshold solve the problem.
Stephen Brooks
2006-04-18 14:13:33
I like this thread, it never dies.

Rotation is good for producing a G-force where there is none (artificial gravity), but you can't use it to reduce the G-forces if your craft is required to accelerate, unfortunately.

I also found this interesting link the other day:
http://www.nasa.gov/mission_pages/exploration/mmb/antimatter_spaceship.html
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