-
#320
by
CJ
on 24 Feb, 2015 02:27
-
Have a look here. The three current candidates have all been imaged -- one (Itokawa) by a Japan's Habayusa spacecraft, the other two (Bennu and 2008 EV5) by radar.
Thanks!
Itokawa, due to having been photographed close up, seems definite. But the radar data on the other two only, per the article, infers that suitable boulders exist. It's far from conclusive, and thus launching an option B mission to one of them would seem to me to be one heck of a risk.
As for Bennu, it seems to me it ought to be ruled out, as it's the target of the Isiris-Rex mission (assuming the mission is a success); it'd IMHO make little sense to sample the same asteroid twice when we'd learn far more by sampling two.
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
-
#321
by
The Amazing Catstronaut
on 24 Feb, 2015 08:20
-
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
Using just the data presented, yep, Itokawa seems like the best option. It would be a wonderful sense of pan-national endeavour if an American mission retrieved a bolder from an astronaut imaged by the Japanese.
There's still a lot of time and other possible candidates drifting around out there, of course. We'll discover more over time.
-
#322
by
jongoff
on 24 Feb, 2015 17:00
-
Have a look here. The three current candidates have all been imaged -- one (Itokawa) by a Japan's Habayusa spacecraft, the other two (Bennu and 2008 EV5) by radar.
Thanks!
Itokawa, due to having been photographed close up, seems definite. But the radar data on the other two only, per the article, infers that suitable boulders exist. It's far from conclusive, and thus launching an option B mission to one of them would seem to me to be one heck of a risk.
As for Bennu, it seems to me it ought to be ruled out, as it's the target of the Isiris-Rex mission (assuming the mission is a success); it'd IMHO make little sense to sample the same asteroid twice when we'd learn far more by sampling two.
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
Option A has similar risks--asteroid masses and sizes are typically known very imprecisely. If you fly up to what you think is a 5m asteroid, but it ends up being 15m, you might be hosed as well.
Also, I'm not sure that doing multiple samples from one body is entirely useless. That assumes the body is nearly homogenous, which is still at best an assumption. IIRC, there's evidence suggesting that asteroid boulders are often not made of the same material as the bulk regolith, so getting an additional sample could very well be useful. Or if they are of similar composition, but Bennu is a type interesting for ISRU development, getting a larger sample might still be worthwhile. It depends strongly on what your goals are with bringing the samples back.
~Jon
-
#323
by
Warren Platts
on 24 Feb, 2015 17:38
-
It depends strongly on what your goals are with bringing the samples back.
I think some would say there's not a whole lot of new scientific results to be expected because we already have in hand thousands of asteroid samples in the form of meteorites. I would counter that fine-grained, unconsolidated regolith does not survive the passage though the atmosphere for the most part, and so characterization of that would be a genuine scientific first.
-
#324
by
CJ
on 24 Feb, 2015 21:05
-
Have a look here. The three current candidates have all been imaged -- one (Itokawa) by a Japan's Habayusa spacecraft, the other two (Bennu and 2008 EV5) by radar.
Thanks!
Itokawa, due to having been photographed close up, seems definite. But the radar data on the other two only, per the article, infers that suitable boulders exist. It's far from conclusive, and thus launching an option B mission to one of them would seem to me to be one heck of a risk.
As for Bennu, it seems to me it ought to be ruled out, as it's the target of the Isiris-Rex mission (assuming the mission is a success); it'd IMHO make little sense to sample the same asteroid twice when we'd learn far more by sampling two.
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
Option A has similar risks--asteroid masses and sizes are typically known very imprecisely. If you fly up to what you think is a 5m asteroid, but it ends up being 15m, you might be hosed as well.
Also, I'm not sure that doing multiple samples from one body is entirely useless. That assumes the body is nearly homogenous, which is still at best an assumption. IIRC, there's evidence suggesting that asteroid boulders are often not made of the same material as the bulk regolith, so getting an additional sample could very well be useful. Or if they are of similar composition, but Bennu is a type interesting for ISRU development, getting a larger sample might still be worthwhile. It depends strongly on what your goals are with bringing the samples back.
~Jon
I agree that getting more than one sample from one asteroid wouldn't be entirely useless, but I'm wondering if it's as good as getting samples from two?
IMHO, the primary reason for bringing samples back is ISRU research, especially volatiles content (the volatiles don't survive meteorite entry). A secondary (but still important) purpose IMHO is general knowledge - sometimes unexpected findings prove useful or important, such as to planetary defense. If there are other reasons, I'm simply unaware of them, not disagreeing with them.
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
Using just the data presented, yep, Itokawa seems like the best option. It would be a wonderful sense of pan-national endeavour if an American mission retrieved a bolder from an astronaut imaged by the Japanese.
There's still a lot of time and other possible candidates drifting around out there, of course. We'll discover more over time.
Retrieving a boulder from an astronaut? Hrmmm.. I'm not sure that's a viable mission plan, plus the astronaut might object.
Seriously though, discovering other candidates is an option, assuming there are imaging missions that will be occurring. I have no idea what sort of timeframe they have in mind for the launch of the retrieval probe. I'd assumed it was within a few years, due to the fact it'll probably take around 6 years from launch to rendezvous and then get the rock to lunar orbit.
Okay, my take at the moment;
Regarding the long mission time, plus the more-is-better aspect of the sample that's to be bought to earth, wouldn't a faster option be to send a the SEP-powered retrieval probe to the target, but incorporate a large return capsule? The probe could sample several spots on the asteroid, load the samples into the capsule (Perhaps could be quite large, even an Orion shell) and place the capsule on an earth-return trajectory? Seems to me that'd get us a larger sample from more locations on a large asteroid than just snagging a boulder, get the samples to earth years sooner (no need for the orbital insertion dance that takes years), and get a larger, more useful sample set? I think it'd take less delta/v than the current mission plan, too.
-
#325
by
Robotbeat
on 24 Feb, 2015 23:58
-
A "Big Osiris-Rex" wouldn't provide experience in deep space operations, EVA on a low-gravity body, nor would it provide in-situ sample handling experience or opportunity for significant ISRU demos in the future using at very minimum dozens of tons of material.
Also, a large capsule (and getting a significant amount of material into it) is not a trivial development.
-
#326
by
CJ
on 25 Feb, 2015 01:27
-
A "Big Osiris-Rex" wouldn't provide experience in deep space operations, EVA on a low-gravity body, nor would it provide in-situ sample handling experience or opportunity for significant ISRU demos in the future using at very minimum dozens of tons of material.
Also, a large capsule (and getting a significant amount of material into it) is not a trivial development.
EVA on a low gravity body? ISS has far more mass, and thus grav, than the boulder size they are thinking of for ARM - and it's essentially zero G for the purposes of this discussion, so ISS EVA gives us basically that experience base already. Visiting a sizable in-situ asteroid would give us experience in low (but not zero) grav opps, but ARM won't.
Deep space opps? If you mean manned deep space opps, then no, a super-Osiris-Rex wouldn't give us that. Apollo, on the other hand, already did (to the same degree ARM would). What, exactly, would we learn on the manned side of ARM that we didn't already learn from Apollo, or couldn't learn cheaper in LEO? It's not a viable test of a deep space Orion, because they won't be using one, they'll be using the 21-day version. Orion plus a hab, such as would be required for any BEO mission? They aren't doing that, either.
In-situ sample handling experience? I'd agree with that if they were going to an actual In-situ sizable asteroid, but they aren't with ARM. They're talking (with option B) something considerably less in diameter than than the Orion capsule. They could practice sample handling procedures in the pool and learn as much.
Would it really be more useful to have a few tons of asteroid in retrograde lunar orbit for ISRU practice, or a bit less in a lab on Earth? It costs a heck of a lot to send anything out to lunar orbit, so the future ISRU tests would be very expensive. If having it accessible in space for ISRU testing is a goal, then perhaps a more useful approach would be to use multi-pass aerobraking (no heat shield needed) to park the rock in LEO.
You're right that a large sample return capsule would not be an easy development. However... would adapting an Orion shell and avionics for the job cost as much or take as long as a manned mission to get far less material? It'd also serve to test the Orion at interplanetary re-entry velocities (which it will have to be capable of to be of any use for anything), something the current ARM won't do.
-
#327
by
Nilof
on 25 Feb, 2015 10:29
-
EVA on a low gravity body? ISS has far more mass, and thus grav, than the boulder size they are thinking of for ARM - and it's essentially zero G for the purposes of this discussion, so ISS EVA gives us basically that experience base already. Visiting a sizable in-situ asteroid would give us experience in low (but not zero) grav opps, but ARM won't.
That is true for option B, but not necessarily for option A, which could retrieve asteroids with three times the mass of the ISS using an Atlas-launched spacecraft. Don't be fooled by the small diameter, even small asteroids are very massive.
Would it really be more useful to have a few tons of asteroid in retrograde lunar orbit for ISRU practice, or a bit less in a lab on Earth? It costs a heck of a lot to send anything out to lunar orbit, so the future ISRU tests would be very expensive. If having it accessible in space for ISRU testing is a goal, then perhaps a more useful approach would be to use multi-pass aerobraking (no heat shield needed) to park the rock in LEO.
Not really. Reaching lunar orbit isn't really that hard if you ride share to GTO(~1 km/s in impulsive delta-v, can be reduced at the cost of time with low-energy transfers), and finding ride-sharing opportunities should be quite a lot easier in the upcoming years with the significant overcapacity of the Falcon Heavy.
Areobraking to LEO could boil off the volatiles on the asteroid, and thus destroy what scientifically differentiates the captured asteroid from meteorites. Furthermore, it requires active control with a lot of correction maneuvers, which may imply a borderline impossible impulsive delta-v budget when the spacecraft is lugging around a payload that may be fifty times its mass.
Imho, Lunar orbit is indeed the best final orbit for captured asteroids, because apart from being the easiest place to park an asteroid, it is where you'd ideally want to have your ISRU fuel for a lunar lander or a Mars transfer stage.
-
#328
by
Robotbeat
on 26 Feb, 2015 02:41
-
....
Would it really be more useful to have a few tons of asteroid in retrograde lunar orbit for ISRU practice, or a bit less in a lab on Earth? ...
No. We know enough about asteroids and meteorites that ground analysis can be done, and Osiris-rex will bring more back. I'm talking about in-space....
If having it accessible in space for ISRU testing is a goal, then perhaps a more useful approach would be to use multi-pass aerobraking (no heat shield needed) to park the rock in LEO.
Not really. That'd be quite non-trivial, besides (especially for the larger rocks from Option A) is somewhat of a liability. You're talking hundreds of tons of mass, being pushed around by a relatively small spacecraft. Getting sufficient control authority over it to do reliable aerobraking (yes, multi-pass) would mean a whole bunch more development. Also, LEO has its own issues like reboost requirements, atomic oxygen, and debris-avoidance if you want to keep the asteroid around long enough to manage it. The thermal environment is much different, so some ISRU methods wouldn't work as well (like using a cold plate to condense volatiles). Even if you're talking aerobrake, that's still a quite non-trivial level of delta-v.
...It'd also serve to test the Orion at interplanetary re-entry velocities (which it will have to be capable of to be of any use for anything)...
That last point is NOT necessarily true. Some architectures propose leaving Orion at a Lagrange point (or, I suppose, lunar DRO) rendevzous point (or station), and going without Orion's heavy mass. If you're planning on reusing your Mars Transfer Vehicle anyway and so need to return it to an EML1/2 Gateway or something anyway, this makes a lot of sense. Additionally, some Mars return trajectories are mild enough that they're comparable to lunar return.
...and again, you might WANT that material in a high energy orbit like DRO or EML1/2 to use at a Gateway there (for shielding crew quarters) or for fueling up your Mars Transfer Vehicle. Propellant at DRO or EML1/2 (which is only a few hundred m/s away from DRO) is worth more (for Mars trips) than propellant in LEO.
-
#329
by
Space Ghost 1962
on 27 Feb, 2015 21:58
-
Actually, the most valuable fuel is likely where you need the most and where it is most costly.
For manned returns, Mars low orbit or surface, depending on launch architecture.
Working backward from that highest point in a logistical system, your can design a means to supply the entire chain most effectively with the fewest dependencies/risk.
One of the benefits of such an approach is the maximal economic effect it provides shifts the balence of cost so much that the risk self minimizes.
-
#330
by
Robotbeat
on 28 Feb, 2015 02:39
-
No argument there.
And that's one reason the Asteroid Retrieval Mission is interesting. Once we figure out how to do ISRU using Option B, you could also do ISRU in Mars orbit with Phobos (or Deimos) or with a Near Mars Asteroid (which is essentially what Phobos/Deimos are anyway) using the very same method. In addition to refueling on the surface of Mars, you'd drastically reduce the total mission IMLEO to almost ridiculously low levels while also allowing fast transit (and high shielding levels while hanging out in Mars orbit for the early missions, if that's your thing).
Definitely counts as "game-changing."
-
#331
by
jongoff
on 28 Feb, 2015 04:17
-
No argument there.
And that's one reason the Asteroid Retrieval Mission is interesting. Once we figure out how to do ISRU using Option B, you could also do ISRU in Mars orbit with Phobos (or Deimos) or with a Near Mars Asteroid (which is essentially what Phobos/Deimos are anyway) using the very same method. In addition to refueling on the surface of Mars, you'd drastically reduce the total mission IMLEO to almost ridiculously low levels while also allowing fast transit (and high shielding levels while hanging out in Mars orbit for the early missions, if that's your thing).
Definitely counts as "game-changing."
Bingo. An ARM mission to Phobos would bring back a boulder about the size of the one we're trying to grab with our prototype. If we could use that to figure out how to do ISRU on Phobos (or Deimos) that would be huge. But to add to something SG1962 was saying, once you've taken care of that high cost area, some other area will become the cost bottleneck, and you can start working on that one. If you could refuel in LEO, EML-2, LMO, and the Martian surface (and if you had aerobraking hardware), that would dramatically change the required vehicle sizes. Admittedly, the question will be how much cheaper you can get propellant from off-Earth destinations. As SG1962 was pointing out, its easiest to win the farther you get from earth. Selling ISRU propellant in LEO is always going to be a tough market, but in lunar orbit or Mars orbit, definitely a different story.
Sorry if I'm babbling.
~Jon
-
#332
by
sdsds
on 28 Feb, 2015 23:28
-
Although planetary defense is a useful motivator and can certainly help overcome funding hurdles, the real reason behind the asteroid redirection concept is to create a BLEO destination for human spaceflight that is accessible in the short term. And the reason behind that is precisely to generate passion and advocacy.
There are already young enthusiasts, 8 or 10 or even 12 years old, who never experienced an STS launch in real time, i.e. by watching one broadcast live on NASA TV. Commercial crew to ISS will staunch the bleed-out of passion a little. Indeed even Soyuz to ISS helps some.
But rebuilding a truly healthy passion and advocacy for human spaceflight is going to take more than just crew transport to an aging LEO platform. Orion taking crew to a redirected asteroid could be a really good start to that.
I think the KISS study was helpful, but I'm unconvinced that a lunar DRO is the best choice. In February 2021 there is a low deltaV opportunity to redirect 2006 RH120 into a Sun-Earth Lagrange point halo orbit. Wouldn't visiting an object in an SEL halo be a great mission for an Orion crew?
-
#333
by
Robotbeat
on 01 Mar, 2015 02:22
-
Actually, that may have been what motivated some people to support this, but I now think the Asteroid Redirect Mission has much more potential than a mere "destination." Especially for Option B (Jon has convinced me!).
The enhanced gravity tractor idea is genuinely new to me. I've read a few papers about planetary defense, and I had never came across this concept before. And I think without ARM it would've been considered unrealistic and perhaps too risky. But this can genuinely improve on the capability of a gravity tractor craft, by a good order of magnitude, allowing the gravity tractor method to be useful on much more dangerous asteroids with less warning time.
And the ability to jump-start asteroid mining by at LEAST a decade is an enormous game-changer.
-
#334
by
sdsds
on 01 Mar, 2015 04:13
-
The enhanced gravity tractor [with its] ability to jump-start asteroid mining by at LEAST a decade is an enormous game-changer.
Oops! Apology and explanation in a later post.
I would like to be persuaded on this, but can't seem to follow the logic. Let's accept the truth of the statement quoted above as a "given." If developed the technology would do this game changing thing. Why does that make it likely that it will in fact be developed? Does the logic rely on some kind of economic profit motive?
-
#335
by
KelvinZero
on 01 Mar, 2015 05:21
-
Isn't it the ARM mission itself that will jumpstart asteroid mining by at least a decade?
I mean, asteroid ISRU anyway. It just isn't on the horizon apart from this, that Im aware of.
(That enhanced gravity tractor idea is cool though)
-
#336
by
A_M_Swallow
on 01 Mar, 2015 20:37
-
This mission is getting complicated:
SEP Tug
bolder grabber
gravity tractor
SLS
Orion
EVA
Possible habitat
ISRU test
ISRU operations.
Make it robust, design it so that failure of one aim does not result in the others failing. Have a costed contingency plan waiting for instance if the habitat does not get launched we could do the ISRU testing on Earth.
-
#337
by
Robotbeat
on 01 Mar, 2015 20:49
-
The enhanced gravity tractor [with its] ability to jump-start asteroid mining by at LEAST a decade is an enormous game-changer.
I would like to be persuaded on this, but can't seem to follow the logic. Let's accept the truth of the statement quoted above as a "given." If developed the technology would do this game changing thing. Why does that make it likely that it will in fact be developed? Does the logic rely on some kind of economic profit motive?
...you're (inadvertedly, I think) putting words in my mouth by editing my quote in that way. (I hope you edit your quote to fix the mistake.)
I actually said this:
"And the ability to jump-start asteroid mining by at LEAST a decade is an enormous game-changer." (referring to ARM, not about the enhanced gravity tractor technique.)
It's the ARM mission itself, placing a big asteroid or a big chunk of one in a relatively easily accessible orbit that will accelerate asteroid mining, not the enhanced gravity tractor technique (which is about planetary defense). Not just the material itself (which is itself VERY helpful for accelerating asteroid mining, since now you can access it easily and cheaply with a small sat piggy-backing on a GTO launch teleoperated with relatively low latency) but also the ability to bag or grab asteroid material and the practical engineering knowledge gained in doing it.
It lowers the barrier to entry dramatically.
-
#338
by
sdsds
on 02 Mar, 2015 03:18
-
...you're (inadvertedly, I think) putting words in my mouth by editing my quote in that way.
Yes, I'm truly sorry about my misunderstanding, and thus mis-representation, of your view. Thanks for correcting that!
It's the ARM mission itself, placing a big asteroid or a big chunk of one in a relatively easily accessible orbit that will accelerate asteroid mining
Yes, I too see it that way.
-
#339
by
HIP2BSQRE
on 15 Mar, 2015 14:32
-
Have a look here. The three current candidates have all been imaged -- one (Itokawa) by a Japan's Habayusa spacecraft, the other two (Bennu and 2008 EV5) by radar.
Thanks!
Itokawa, due to having been photographed close up, seems definite. But the radar data on the other two only, per the article, infers that suitable boulders exist. It's far from conclusive, and thus launching an option B mission to one of them would seem to me to be one heck of a risk.
As for Bennu, it seems to me it ought to be ruled out, as it's the target of the Isiris-Rex mission (assuming the mission is a success); it'd IMHO make little sense to sample the same asteroid twice when we'd learn far more by sampling two.
So, if I'm reading this right, Itokawa is the only viable current candidate for option B?
Option A has similar risks--asteroid masses and sizes are typically known very imprecisely. If you fly up to what you think is a 5m asteroid, but it ends up being 15m, you might be hosed as well.
Also, I'm not sure that doing multiple samples from one body is entirely useless. That assumes the body is nearly homogenous, which is still at best an assumption. IIRC, there's evidence suggesting that asteroid boulders are often not made of the same material as the bulk regolith, so getting an additional sample could very well be useful. Or if they are of similar composition, but Bennu is a type interesting for ISRU development, getting a larger sample might still be worthwhile. It depends strongly on what your goals are with bringing the samples back.
~Jon
Jon,
So what are the advantages with going with option A besides maybe getting a bigger rock?
