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Using a direct elastic collision with a passing asteroid for propelling a spacecraft? 10

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KirbyWan

KirbyWan

Aerospace
Apr 18, 2008
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Howdy all,

So every time I see a news story about an asteroid that will pass close to the earth, I wonder if it would be possible to use an elastic collision with the passing asteroid to propel a spacecraft to deep space. I imagine either a long, multi-stage cylinder to compress a gas (I don't think this would work) or perhaps a pair of micro-satellites connected by a cable that would be in the path. (I think this has a chance of working.)

What would be the max G-loading a satellite could be designed to withstand while having useful systems for positioning, communication and of course science, survive?

If the elastic collision was efficient it could propel a spacecraft twice as fast as the asteroid was going.

Is this a reasonable idea? Or am I nuts? (for this specific idea since I know generally, yeah I'm a bit nuts.)

Thanks,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.
 
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As far as maximum g-loading a satellite could be designed to withstand, I would look into the maximum g-loading of electronic fused artillery shells. There is research to put some pretty complex sensors into artillery, so this would represent the maximum g-load practical for electronics.

As far as any physical material making contact with an asteroid as part of any form of momentum-stealing propulsion system??? It would have to be made out of a fantasy science fiction material. At the closing speeds involved things tend to vaporize upon contact. Kinetic energy is 1/2mv^2 and the delta-v involved becomes a whole lotta heat.
 
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I think Comco is a bit optimistic. An artillery shell's electronics are very specific and can rationally be laid out to cope. I suspect only a single task could be supported with artillery forces involved. For instance you could maybe make the satellite able to communicate but probably noting else or do one science task but not communicate (then why bother).

Probably about 10 ~ 12 gees could be managed.

My problem with your scheme is the utter lack of control about the collision face. Hitting a rolling random faced surface will result in a randomized impulse, one possibly not in the designed high g plane.

A second problem is that the required parabolic antenna needs to be included if you want to hear anything back from a 100AU they tend to be thin and kinda fragile.

Keith Cress
kcress -
 
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?? I'd go with nuts as well.
> As mentioned above, there's no longer a thing called elastic collision for any objects in space
> Even if you could, it would do nothing; an asteroid is essentially an immovable object relative to a satellite, so you might as well be bouncing the satellite off the Moon, i.e., there's nothing to be gained, energy-wise
> People already have a better and less destructive way to steal kinetic energy, albeit, it takes longer. Read up on slingshot effect, wherein you use existing planets and moons to gain gravitational acceleration and change your direction. This has even been featured in many a sci-fi story, including at least one episode of the original Star Trek.
> Since

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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IRstuff,

Yeah, I'm familiar with the slingshot method of gaining delta V. It just doesn't add very much because the time you are close enough to gain that gravitational boost is so short.

I'm not sure I agree with the 'no elastic collisions' part of your argument. I understand the kinetic energies we're talking about would vaporize a satellite. But if you had one made out of unobtanium that could withstand an impact with a perfectly rigid satellite I think the physics idealization would overcome the gravitational effects of the interaction. This would be a good physics test question I bet.

I just want to play some planetary billiards, Velikovsky be damaged. :)

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.
 
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I think you "could" like deliberately (oddly, that kept coming out as dilbertly … maybe appropriate too) crash into an asteroid , but with a KE absorption and release mechanism … like a spring. Other than max g loading, which could possibly be controlled with k, the exit flightpath is very questionable.

Possibly you could slingshot around the asteroid, with multiple passes. It's be a tricky problem to solve, capture would be tricky (but has been done).

another day in paradise, or is paradise one day closer ?
 
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Hollow out the asteroid. Eject the debris to stop its rotation. Build a big rail gun through the middle.
Cover the face of the asteroid with solar panels, which always face the sun now that it's rotation is stopped.
Fly your spacecraft through the middle. This would be a good time to put your seatbelt on.
Activate the rail gun at the moment of entry. Emerge with several GJ more KE than you entered with.
While flying through, gravity will temporarily give you some KE as you approach, and lose just as much as you leave, but the momentum the rail gun gives you as you pass through is yours to keep.
The owner may charge you a *cough* modest fee.

PS
Read the link before making comments about steel spacecraft.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF
 
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The force in a bolo style pair of satellites is pretty much going to be coaxial with the string, so that objection doesn't really apply. it's about 4000g from memory in a shell. It can of course be reduced by any desired amount via compliance in the string.

I don't think the density of asteroids going in the right direction is going to make it a mass effective approach, compared with the interplanetary transport network and solar sails.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Solar sail and Ion propulsion...

Solar sail may provide free propulsion at the cost of a huge sail and lack of maneuverability and serendipity of solar radiation and 'flow'.

Ion propulsion requires 'xenon' fuel but is incredibly efficient and allows precise targeting. When compared to structure needed to survive elastic impact/rebound... these are likely to be a lot lighter... not to mention reliable deceleration at end of flight [arrival at a target body]. Use of one or more radioisotope thermal generators [RTGs] with several jettisonable xenon tanks would allow true deep-space operations for decades.



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
 
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KC said:
...only a single task could be supported with artillery forces involved.
Click to expand...

edit: in reference to...

comcokid said:
...maximum g-loading of electronic fused artillery shells. There is research to put some pretty complex sensors into artillery...
Click to expand...

To clarify and expand on this, the acceleration experienced by an artillery shell is on the order of 15,000g.

It's obviously pretty much like 'being shot out of a gun...'

The single task is to hit the target.

But this 'single task' includes battery and power supply, sophisticated GPS system including antenna, inertial measurement unit, even laser seekers in recent versions, computer guidance of course, fin actuators, and much more.

[sub](All this is public info.)[/sub]

Joke Alert: Dealing with the 15,000g requirement is trivial. One merely opens up the Requirements database and types it in. Easy! ;-)




 
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Several science fiction stories from the late 60's-early 70's timeframe used solar sails to move asteroids from their orbit back towards an earth orbit, moon orbit, and various other spots.
One of two even expanded that into "inter-world races" like the international yachting races.

Much drama of rescues, solar flares, hijacking, corporate competition and pirates to get the asteroid metals.

Deflection will be needed at some point in time on a randomly rtating, mixed and irregular surfaced, concentric center of gravity random rock though.

My opinioin? Blow at least part of it up with big nuclear weapons, use the cracking and reaction forces to spread the resulting chunkc slightly apart on slightly differtent paths.

Blow up whatever the biggest piece left over that is still heading towards earth with a second nuke.
Rinse, wash, repeat.

Kinetic impact - even of a solid object far larger than the old battleship projectiles of 2000 - 4000 kg at 1500 kps would likely be too little energy.
 
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I've run the interior ballistics analyses for a couple of cases in the dim past. The numbers can actually be much higher, particularly for tank rounds. Thankfully, the duration is short.
Interior_Ballistics_azdws3.gif


TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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I wonder if something like a 100 mile-long piece of super-ball like string that could catch an asteroid with a net then spread out the impulse over many seconds or a few minutes as it accelerates the satellite would greatly reduce the peak g.

I haven't figured out how this trailing sat would eventually pass the asteroid rather than splatter on the very back of it.

Keith Cress
kcress -
 
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IRstuff,

I've fired those 105mm rounds. I used to be an M60 tanker. At least the HE (training) rounds. What's APFSDS? Is that Sabot rounds?

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.
 
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A toroidal magnetic drive? You've seen the classic drop a magnet down a copper pipe? What about a toroidal magnet that aligned along the path of the asteroid so there is no physical contact, but creates enough...impedance...counter...magnetic, okay I'm a mechanical engineer, not an electrical. But it could be a way to manage the momentum transfer without a direct physical contact. Sort of an inverse rail gun like what SparWeb suggested. And the rotation of the asteroid shouldn't be critical, it just has to have enough conduction to ... act as a ... conductor?

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.
 
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