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

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

(OP)
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.

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

I'll go with the "nuts" option !

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

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.

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

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 - http://www.flaminsystems.com

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

?? 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! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

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

(OP)
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.

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

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).

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

KirbyWan:

Do you have someone you would like to eliminate, a la Isaac Asimov's short story, "The Billiard Ball"? LOL See link below.

https://en.wikipedia.org/wiki/The_Billiard_Ball

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

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

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

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

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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

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]

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

Quote (KC)

...only a single task could be supported with artillery forces involved.

edit: in reference to...

Quote (comcokid)

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

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.

(All this is public info.)

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

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

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.

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

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.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

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

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 - http://www.flaminsystems.com

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

Oh, I like it IR. Make the net from the same stuff and pyrotechnically release one side.

Keith Cress
kcress - http://www.flaminsystems.com

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

(OP)
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.

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

(OP)
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.

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

Yep, Armor Piercing, Fin-Stabilized, Discarding Sabot.

Eddy effects will only slow down your probe; might be useful for stopping a high-speed probe, but even a milliradian misalignment could spell D-I-S-A-S-T-E-R

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

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

which is why this won't work … you cannot control the exit direction

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

rb1957; There are likely craft trajectories for some studies that don't care which way the satellite actually goes as long as it goes fast.

Keith Cress
kcress - http://www.flaminsystems.com

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

I thought the point was to gain velocity for the "vehicle" ? I assumed the point to doing this was to go somewhere. The rebound trajectory from an asteroid impact is likely to be very variable.

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

(OP)
For interstellar missions, one of the things I was thinking of for getting a big momentum transfer from a passing asteroid, the direction really isn't all that important. Pointed toward the heliopause within 30° would be good enough. Also with the idea of using a craft that has a toroidal magnet to "softly" transfer momentum the set up would tell us with a fair amount of accuracy where we would be headed and let us select the direction based on where we encounter the asteroid.

Maybe for any of these ideas we could use an ion thruster to reduce the delta-V between the asteroid and the vehicle to a survivable level. then use the ion thruster again to fine adjust the path after the encounter.

Let's be honest, this is a probably unworkable idea, but the back and forth has refined the idea and given us new ideas. It's the kind of impractical engineering that occasionally comes up with a workable, useful solution.

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

I was only thinking of targets in the plane of the Solar System being of interest, when I suggested a rail gun.
There are a LOT of different possible methods of electromagnetic acceleration, and deceleration hadn't even occurred to me at the time but I can see that as a possibility, too.
It's a common tool in Sci-Fi to move from one place to another, on the Moon for example, where air isn't an issue and you only need to clear the terrain. Usually works like the Japanese maglev trains.
Some attempts have been made to find a practical design. Superconductors are feasible in space. Look up the Star Tram for just one example.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

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

"starTram" for taking things into orbit ? space elevator for me !

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

(OP)
I have ideas about workable space elevators. I never liked the idea of a tether that reaches down to the earth's surface and up to geosynchronous orbit. It would take a huge amount of material and the location it attaches to the planet would be a target. Here's my idea for a space elevator:

It uses an airplane as a first stage to get a payload as high and fast as possible. We could get the SR-71 to 80k feet and mach 3 in the 60's we could go higher and faster for a purpose build first stage air breathing launch vehicle.

This vehicle would rendezvous with a rotating space station with a long tether so that the tether would dip into the highest layers of the atmosphere when needed to receive a payload and then retract enough to minimize drag. If the tether rotated counter to the direction the space station traveled it would reduce the velocity at the end of the tether. The length of the tether, height of the space station, rate of rotation would all be adjusted to match the height/speed a launch vehicle could attain. When the tether is not being used to catch payloads, it could be used as an electro-dynamic tether for propulsion and station keeping. Rotation bonus: The station would have some artificial gravity since I expect the center of mass would be somewhere along the tether, though I expect much closer to the station end of the tether.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

That's called a skyhook by the tether guys. Workable, in theory, with current technology (material strengths), you just need to figure out how to build and deploy the tether. If down-going mass (really momentum change) (i.e. from asteroid/lunar mining?) equals up-going mass/momentum over time, you don't necessarily need to provide propulsion for the skyhook/tether, provided aero drag is minimized or avoided altogether. A skyhook combined with a surface railgun or ram accelerator launch system has been proposed as a low-cost to orbit tech.

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

so instead of geo-synchronous we'd go for an orbit with a low ground speed, something we could match with the plane. Maybe flying to the end of this tether isn't much different to inflight refueling (except much faster) ?

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

(OP)
rb1957,

Yeah, The expensive part of getting to space is getting out of the atmosphere. Since the tether is rotating backwards, it's ground speed is much lower than the station. The ISS is at an altitude of 400 km, and we probably don't need to be that high, above a 100 km absolute minimum, say 150 km and subtract off the 30 km or so for the first stage and we're working with a 120 km tether, much more workable from an engineering perspective than 23,000 km to geostationary orbit. Once you can obtain a low earth orbit, high efficiency ion thrusters (or again electro-dynamic tethers, why has this propulsion tech never taken off?) could get you to the orbit you want, just not quickly.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

(OP)
Dang, that's 23k miles for geostationary orbit, or 35,000 km. -Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

you know you can edit your posts now ?

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

KirbyWan (Aerospace) (OP) 7 May 19 15:42 "I have ideas about workable space elevators. ..."

Re: Space Elevators

Reportedly, one of the most difficult aspects (*) of a vehicle climbing a tether to reach space is the energy needed by the vehicle. Dreamers imagine beaming microwave or laser energy up the vehicle, as it climbs higher and higher.

(* A loony claim, but let's go with it for now.)

The solution is obvious and perfectly trivial.

Install a pulley at the top.

Make the cable twice as long, and form it into a loop.

Then use an electric motor at the bottom to turn the cable. The electric motor can obviously be wired to the grid.

Easy.

Acknowledge that the cable will be twice as long, twice as heavy, under twice the tension, and that's before making it thicker to deal with the added tension. But these are mere details, since "the most difficult aspect" was carrying the necessary energy.

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

you're welcome !

we're talking more today about returning to the moon. I wonder if a lunar space elevator makes sense ? it'd be easier to accomplish but I think it'd be a very long term investment … but it makes for good wondering.

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

With the strongest carbon fiber now available the longest a cable can possibly be, and support only its own weight, is about 300 kilometers.

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

(or again electro-dynamic tethers, why has this propulsion tech never taken off?)

I have a colleague, who's probably still in the biz, who did some research work while we were interns at Nasa-Lewis, mostly regarding tethers.

ED tethers work against a magnetic field, like that of Earth's. Far enough away from those fields and you get no propulsion. But, even for satellites, the concept is tricky, because having a long tether means increased chances for collisions with space debris. A lot of trials have failed due to deployment issues, not sure what is up with that. In the comsat biz, they are looking for spacecraft with 10-yr and by now closer to 15 or 20 years lifetimes. At GEO orbits a longer tether is required to get propulsion (and the main component for delta-V is N-S stationkeeping, which I don't think tethers can do, cuz the magnetic field lines are running N-S? Not sure). But anyway, longer tether means bigger odds of collisions and shorter tether life expectancy.

Past that, there have not been any really successful deployments and verification of propulsive tethers. Lots of trials and experiments, lots of failures, a few notable successes - see

https://en.wikipedia.org/wiki/Space_tether_mission...
and more generally
https://en.wikipedia.org/wiki/Space_tether
https://en.wikipedia.org/wiki/Electrodynamic_tethe...

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

GRACE and GOCE and a number of superpressure balloons have used magnetic paddle torquers for attitude adjustment instead of reaction wheels

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

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

Torque rods on LEO spacecraft are a thing, I know that all of the Iridium s/c since the first ones had them. But they don't work as well at higher orbits, and most GEO comsats don't use them.

from https://en.wikipedia.org/wiki/Magnetorquer :

A broader disadvantage is the dependence on Earth's magnetic field strength, making this approach unsuitable for deep space missions, and also more suitable for low Earth orbits as opposed to higher ones like the geosynchronous. The dependence on the highly variable intensity of Earth's magnetic field is also problematic because then the attitude control problem becomes highly nonlinear. It is also impossible to control attitude in all three axes even if the full three coils are used, because the torque can be generated only perpendicular to the Earth's magnetic field vector.[2][3]

Magnetorquers or torque rods are fairly small, compact devices, not tethers.

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

(OP)
I hate when I have a brilliant idea that someone else thought of 50 years ago. Btrueblood, I looked up Skyhook on wikipedia and this is exactly what I was thinking of. The HASTOL even includes the first stage part I was thinking of. I probably came across this in the distant past and forgot about it only to "invent" the idea again.

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

wot ? you don't think other people can be equally "brilliant" ? (smile)

btw, if it was such a brilliant idea, how come nothing came of it ? won't that make it an "average" idea ? (great/good concept, lousy implementation)
Sure some things are slowly being developed, but the things SX has accomplished (in the face of traditional "rubbishing") are truly amazing.

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

(OP)
Maybe the state of technology just hasn't advanced yet to make the idea workable, or is just on the cusp of becoming workable. See also: Flying cars.

Kirby Wilkerson

Remember, first define the problem, then solve it.

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

Quote (btrueblood)

Magnetorquers or torque rods are fairly small, compact devices, not tethers.

Very compact: Cubesat size

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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