Author Topic: Captured Asteroid mission - Redefining EM-2 for the bold challenge  (Read 32623 times)

Offline gladiator1332

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This is all good and exciting, but is anyone else skeptical of such an ambitious mission for the first crewed flight of Orion? Maybe I am missing something, but we have the unmanned earth orbit test flight on the Delta IV, then the unmanned EM-1 flight, and then this?
Or is NASA confident that the two unmanned flights will have enough of the issues solved that a manned LEO test flight is not needed? Pretty bold.

Offline MP99

This is all good and exciting, but is anyone else skeptical of such an ambitious mission for the first crewed flight of Orion? Maybe I am missing something, but we have the unmanned earth orbit test flight on the Delta IV, then the unmanned EM-1 flight, and then this?
Or is NASA confident that the two unmanned flights will have enough of the issues solved that a manned LEO test flight is not needed? Pretty bold.

I'm not seeing the target being there much before 2025.

That either means a long delay to EM-2, or it would be EM-3/-4/-5 that would actually go to the target.

IIRC the KISS report says 1-2 years to reach escape from LEO, 1-2 years to reach the target from there, up to 6 years to bring the object into Lunar orbit (not sure if dropping it at L2 makes that easier or harder).

I guess you can cut a little time off the mission by putting it on SLS/ICPS or FH, which will get that sort of mass to escape immediately.



Also, the feasible objects will have something like a 10 year synodic period (they're moving slowly relative to us, so when they go they take a long time before they come around again). If we catalogue something this year, it'll be back around 2023 ready for us to lasso it, then spend up to 6 more years getting it into position.



I also wonder whether L2 is the right place for this. It needs to have an orbit that will passively dispose of itself into the Moon if Congress stops paying the bills to go back to it, ISTM L2's potential energy means it could eventually wander into an Earth orbit. (Someone correct me on that if it's wrong.)

cheers, Martin

Offline KelvinZero

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There is a section labelled 'safety' in the Keck report, among other things it mentions the final destination being a "high lunar orbit" which would naturally decay into the moon if abandoned. Also claims that size and mass routinely impact the earth, and that carbonaceous asteroids (the target type) break up immediately in the atmosphere and dont make it near the ground.

Offline nlec

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This mission seems like overkill to chip a few fragments off of the asteroid for return to Earth.  If the probe is going to capture the asteroid autonomously, I would rather see an (inflatable?) heatshield added and try to bring the whole thing back to earth without placing a crew at risk.

Offline JohnFornaro

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NPR jumped on the bandwagon this morning in order to garner support from the few people who do not already vocally support this effort.
Sometimes I just flat out don't get it.

Offline JohnFornaro

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3. Putting something in high lunar orbit provides a justification for developing the ability to go there.

Isn't there a celestial body already in the lowest lunar orbit possible?
Sometimes I just flat out don't get it.

Offline JohnFornaro

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This is all good and exciting, but is anyone else skeptical of such an ambitious mission for the first crewed flight of Orion?

I don't think there's much opposition to the proposed effort at all. 
Sometimes I just flat out don't get it.

Offline ChileVerde

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That either means a long delay to EM-2, or it would be EM-3/-4/-5 that would actually go to the target.

<snip>

I also wonder whether L2 is the right place for this. It needs to have an orbit that will passively dispose of itself into the Moon if Congress stops paying the bills to go back to it, ISTM L2's potential energy means it could eventually wander into an Earth orbit. (Someone correct me on that if it's wrong.)

I don't know about the long-term orbitology associated with L2, but have also wondered about EML4/5. As points of stable equilibrium, wouldn't they be worry-free places to park asteroids?
"I cant tell you which asteroid, but there will be one in 2025," Bolden asserted.

Offline Robotbeat

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This is all good and exciting, but is anyone else skeptical of such an ambitious mission for the first crewed flight of Orion? Maybe I am missing something, but we have the unmanned earth orbit test flight on the Delta IV, then the unmanned EM-1 flight, and then this?
Or is NASA confident that the two unmanned flights will have enough of the issues solved that a manned LEO test flight is not needed? Pretty bold.
Shuttle had no unmanned test flights. Honestly, I think 2 unmanned test flights is fine. The mission this time is not terribly complicated (other than the EVA, which although very interesting, I don't think is the most complicated EVA that has been done).

Grappling the capture craft can be simulated, and perhaps the arm used can be tested on ISS (if deemed necessary). I suppose it's even possible for the EVA procedures to be tested somewhat at ISS, although I'm confident (as much as anyone can be that isn't an expert in EVA) that wouldn't be worth the risk and cost of testing it in LEO space (we have the Neutral Buoyancy Lab for a reason).
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Offline mikegi

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This is a little off-topic ... but I really admire the veterans here who can be enthusiastic about a new proposed NASA mission that involves HSF. I've gone completely over to the Dark Side of Cynicism in the years I've been lurking here on NSF. It goes something like this:

Year One: you discover NSF.com and are fascinated by all the technical discussion of NASA's proposed missions and hardware. You believe that NASA is actually building hardware to take us to the Moon and beyond. "We're going to the freaking Moon and Mars!". You consider posters like "Jim" to be cynical old men that only rain on other people's parades and that what they recommend is just "thinking small".

Year Two: you're still optimistic but watch the grandiose plans discovered in Year One get whittled away by Congress or the Administration. You start listening more to the posters here that always include political concerns in the design of their missions/hardware. Still, you figure you can manipulate the politicians to support your missions by throwing them a bone. Hey, we're still going to land men on the freaking Moon!

Year Three: the Year One plans have been cancelled after the USGov has blown billions on it. But ... there's a new HSF grandiose plan from NASA to replace it. You're concerned about the large recurring costs of the new plan but think that, given what you've seen over the previous years on NSF, those who designed it must have received a wink-and-a-nod from those who control the purse strings. But hey, while we're not going to the Moon's surface anymore, we're still going to a freaking space station at EML-1 or EML-2!

Year Four: well, the planned Space Station at EML-1/2 has been whittled away ... and the new HSF plan to go to an asteroid has been replaced by plans to bring the asteroid here and fly a smaller HSF mission to it. Your immediate thoughts are not whether that's an exciting idea and technical challenge but, rather, whether the appropriate Administration supporters and Congressional Districts benefit from such a plan. In other words, is it viable? You begin to realize that HSF has nothing to do with space or technology or science but rather is simply disinterested politicians fighting for various quantities of cash. It's like seeing a new SciFi show that starts with plenty of pew-pew and effects but then evolves into just another "character study", this time set in space. Yawn.

Is there any reason to believe that all this new pew-pew won't devolve into just another character study?

(mods, please delete if inappropriate)

Offline Robotbeat

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That's a very reasonable question to ask. Can we talk about it in a new thread?
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Offline Space Frog

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I apologize if this is covered (I haven't seen anything about it), and maybe this is a stupid question, but how do they intend to stop the captured asteroid's tumbling or rotating?  It's pretty safe to assume that it's going to be tumbling, so the only thing I can imagine they're planning on doing is bagging the thing and then dissipating the rotational energy through friction with the inside of the bag.  Which would, of course, transfer those forces to the spacecraft, which would then use it's RCS system to gradually correct for them?  The only other thing I could imagine working is some kind of harpoon-probe with an aimable hall effect thruster on it, to de-spin the object before it's bagged.  So - bag and de-spin, or de-spin first and then bag?  Or am I missing something?

Offline MP99

So - bag and de-spin, or de-spin first and then bag?

Bag first, then de-spin, I believe.

ISTM there will be considerable disruption to the surface - which the geologists will wring their hands ad gnash their teeth about.

Apparently, the behaviour of the dust is one of the things important to understand, and it won't be pristine, so ISTM the results will be questionable.

cheers, Martin

Offline sdsds

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is there much more information on the precision rendezvous? The docking?

What would that be particularly challenging?  It's a rendezvous and docking in lunar orbit with a co-operative object.  That's been done before.

Yes, good point. But as for the docking, Orion will have never done that before. As for the rendezvous, is there a way to calculate the added delta-v needed to not just reach HLO, but sync up with another vehicle in HLO? It could be zero if the timing were perfect. How often would those windows occur? If the timing weren't perfect, how much propulsion would rendezvous require in e.g. the worst case?

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do all four crew members completely suit up each time anyone goes out the hatch?

No doubt they would

Does this impose on the prior (unmanned EM-1) mission a requirement to depressurize the capsule while it is in cis-lunar space? Or are vacuum chambers on Earth good enough to simulate this, so it can be done the first time "for real" with crew lives at stake?

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as was the case for Gemini and Apollo EVAs.

Do ya think those missions would have met modern crew safety standards?
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Offline Proponent

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I also wonder whether L2 is the right place for this. It needs to have an orbit that will passively dispose of itself into the Moon if Congress stops paying the bills to go back to it, ISTM L2's potential energy means it could eventually wander into an Earth orbit. (Someone correct me on that if it's wrong.)

I don't know about the long-term orbitology associated with L2, but have also wondered about EML4/5. As points of stable equilibrium, wouldn't they be worry-free places to park asteroids?

Orbitalogically speaking, all of L1-3 are all unstable.  The Keck paper envisions parking the asteroid in lunar orbit rather than at L2 explicitly because an eventual collision with the moon rather than with the earth can be guaranteed.

I'd wondered about L4 and L5 too.  I'll bet it's more difficult to arrange a low-delta-V capture there than in high lunar orbit.
« Last Edit: 04/13/2013 12:06 AM by Proponent »

Offline Proponent

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As for the rendezvous, is there a way to calculate the added delta-v needed to not just reach HLO, but sync up with another vehicle in HLO? It could be zero if the timing were perfect. How often would those windows occur? If the timing weren't perfect, how much propulsion would rendezvous require in e.g. the worst case?

It would all be calculated in advance, of course, and there would be an allowance for errors in velocity and timing.  It's always possible that the allowance could prove inadequate, and the rendezvous would not be accomplished.  But it's the same on every rendezvous mission that's ever flown.

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do all four crew members completely suit up each time anyone goes out the hatch?

No doubt they would
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Does this impose on the prior (unmanned EM-1) mission a requirement to depressurize the capsule while it is in cis-lunar space? Or are vacuum chambers on Earth good enough to simulate this, so it can be done the first time "for real" with crew lives at stake?

The first Gemini EVA was on the second manned flight.  I don't believe a Gemini spacecraft had ever been depressurized in flight before.  I'm sure that Orion would be extensively vacuum-chamber tested.

Offline sdsds

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3. Putting something in high lunar orbit provides a justification for developing the ability to go there.

Honestly, I think that's disingenuous.

Yes there was an attempt to include some wry humor, perhaps verging on cynicism. But no, it was a genuine attempt to provide the original questioner with a semi-complete set of answers regarding the benefits of the Keck approach over the one he described. (Going a bit semiotic, the "3." was intended to signify what followed was a tertiary benefit, not a replacement for the other two which had already been listed.)

Stated without humor or cynicism, the questioner's alternate plan would be inconsistent with the well-understood goal of using SLS and Orion for human exploration beyond LEO, whereas the mission as outlined in the President's budget request would be consistent with that goal.
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Offline Solman

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Wouldn't make better sense to tow a BIG asteroid to Earth and leave it in orbit there? Astronauts will need to travel to lunar orbit to reach the little thing NASA is preparing to fetch. We could hollow out a big one and use it as a space station. Thick dirt walls make excellent shielding against solar and cosmic radiation. Surely that would benefit us more.
Big asteroids are big, they have much more mass.  Which means you need a lot more fuel to move them.  Basically, if you're using the same type of propulsion for each, and moving them the same amount (same delta-v), you need the same % of it's mass in propellent for each to move them. ( http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation )

So, if you want to do the same thing with an asteroid 1000 times the mass, it takes 1000 times as much fuel.

And mass scales with radius^3, so if you wanted something that has 10x the radius, it would be (10^3) = 1000 times as massive.

 Unless you use the asteroids' volatiles as propellant in a resistojet or similar propulsion system. As has been pointed out volatiles might be extracted from just having a dark colored bag. This would be true if an appropriate icy NEO could be found. Otherwise a means of extracting and heating, perhaps with mirrors, small amounts of regolith and exhausting the volatiles derived after further heating could propel the asteroid.
 I realize this may be too ambitious for the first mission but some way of using the asteroid material as propellant will have to be developed if asteroid mining is to occur on a large scale. 

Offline Robotbeat

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Capturing a small, icy asteroid would be a pretty convenient way to get hundreds of tons of water... Put it in a bag pressurized to above triple point of water, heat it slowly with the Sun, spin slowly so all the solid parts went to the bottom of bag (may need a tether so center of mass isn't inside the asteroid), and place a "dehumidifier" cooled by radiators inside the bag, collecting the water as it condenses on the cooling coils. No chipping away at anything required. You could extract most of the volatiles that way.


The only thing is that there probably aren't any icy asteroids until you get out in the asteroid belt, closer to Mars...
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Offline deltaV

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I apologize if this is covered (I haven't seen anything about it), and maybe this is a stupid question, but how do they intend to stop the captured asteroid's tumbling or rotating?  It's pretty safe to assume that it's going to be tumbling, so the only thing I can imagine they're planning on doing is bagging the thing and then dissipating the rotational energy through friction with the inside of the bag.  Which would, of course, transfer those forces to the spacecraft, which would then use it's RCS system to gradually correct for them?  The only other thing I could imagine working is some kind of harpoon-probe with an aimable hall effect thruster on it, to de-spin the object before it's bagged.  So - bag and de-spin, or de-spin first and then bag?  Or am I missing something?

Page 35 of the KISS study (http://www.kiss.caltech.edu/study/asteroid/asteroid_final_report.pdf) proposes to match rotation rate with the assteroid, bag it, and then de-tumble the spacecraft/asteroid combination using RCS thrusters.

Quote from: KISS
De-spin To estimate the time and propellant required to de-tumble the asteroid, the object was assumed to have a mass of 1,100 t, be rotating at 1 RPM about its major axis, and have a cylindrical shape of 6-m diameter x 12-m long. The 200-N RCS thrusters would be used for this process and are assumed to have a moment arm of 2 m. The angular momentum of spacecraft with asteroid would be 1.7x10^6 Nms, and the major and minor moments of inertia (MOIs) with the spacecraft attached are estimated to be 1.65x10^7 kgm^2 and 5.52x10^6 kgm^2. The resulting time for despin would be ~33 minutes assuming continuous firing, and approximately 306 kg of propellant would be required.

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