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#500
by
Robotbeat
on 06 Apr, 2015 00:14
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But don't you also want to be able to reuse the capture mechanism, too?
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#501
by
notsorandom
on 06 Apr, 2015 19:14
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While it may be good to reuse it should it work out well it may not be unreasonable to think that there will be some lessons learned by operating the SEP system. This would be the first use of SEP on that scale. That operating experience would be fed into the second unit. Those changes may be such an improvement that it is worth building another unit and forgetting about the first one.
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#502
by
jongoff
on 06 Apr, 2015 20:19
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But don't you also want to be able to reuse the capture mechanism, too?
Maybe. A lot depends on which capture mechanism approach they take, and how much it costs/weighs. Right now the capture mechanism is how the boulder is connected to a docking port. For repeat visits you'd probably want to leave it attached to something that can make it easier for future vehicles to attach to it--leaving the boulder totally free-flying is an option, but my preference has always been to leave the capture mechanism as sort of a mechanical interface, and just fly a new one along with the propellant needed to refuel the SEP module.
More than one way to skin the cat though, and you definitely would want to reuse the robot arms if you went with the current Option B baseline of fancy satellite servicing arms with microspines on them.
~Jon
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#503
by
Graham
on 10 Apr, 2015 00:13
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#504
by
jongoff
on 10 Apr, 2015 05:55
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According to NASA Watch the NAC is looking into the possibility of sending ARM to Phobos.
http://nasawatch.com/archives/2015/04/nasa-advisory-c-5.html
https://twitter.com/nasawatch/status/586273809419935745
While Option B should work just fine on Phobos, you're going to either need a much bigger spacecraft, or you'll be bringing back a much smaller rock. Might make more sense for a second mission than a first one. And going to Phobos you do not get to demo any planetary defense tech. It's not a stupid idea, but I'd still prefer to see an asteroid (preferably carbonaceous chondrite) visited first.
~Jon
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#505
by
TrevorMonty
on 10 Apr, 2015 07:48
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A sample return form Phobos of Deimos would get a lot more public support. The sample could be used for testing ISRU technology eg oxygen extraction.
The only issue with a change of plan is that I don't think $1.25B would cover this mission, it would tend to grow and become bloated/expensive.
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#506
by
Ben the Space Brit
on 10 Apr, 2015 11:40
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A sample return form Phobos of Deimos would get a lot more public support. The sample could be used for testing ISRU technology eg oxygen extraction.
The only issue with a change of plan is that I don't think $1.25B would cover this mission, it would tend to grow and become bloated/expensive.
I think that the only significant modification of the spacecraft design would be to replace the capture bag with some kind of grapple to grab something off of Phobos's surface. The moonlet's gravity is so weak that descent, hover and ascent could be handled with the probe's hydrazine RCS motors. Oh, and some kind of imaging system to identify potential grab targets. The 'business end' of the probe would probably need to be totally redesigned.
The big cost driver would be writing the software for the autonomous target identification and grapple sequence. I don't think that anything like that has been attempted before; it could require self-modifying polymorphic code.
Those who know more about this will doubtless correct me.
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#507
by
Blackstar
on 10 Apr, 2015 11:41
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the NAC is looking into the possibility of sending ARM to Phobos.
There's been talk about doing that for almost a year now within some circles. This image is from a January AIAA paper. And last July NASA was showing off a "Phobos mission" model that featured ARM. I've got pictures of that and will try to post them here. That concept is more appealing to the scientists, who have little interest in the asteroid mission. (There is a lot of scientific interest in asteroid missions, but to specific types of asteroids, such as those containing organics, metals, etc. ARM would pick a boring bolder.)
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#508
by
Star One
on 10 Apr, 2015 11:55
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A sample return form Phobos of Deimos would get a lot more public support. The sample could be used for testing ISRU technology eg oxygen extraction.
The only issue with a change of plan is that I don't think $1.25B would cover this mission, it would tend to grow and become bloated/expensive.
Well it certainly captures my interest more. If it doesn't add too much in the way of complexity and cost to the mission it sounds like a worthy proposal.
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#509
by
Blackstar
on 10 Apr, 2015 14:54
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The sample could be used for testing ISRU technology eg oxygen extraction.
No.
They're still only talking about a rock.
Next time you're near a body of water pick up a rock and take it home and try to extract water from it.
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#510
by
Blackstar
on 10 Apr, 2015 15:23
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http://blog.chron.com/sciguy/2015/04/advisors-to-nasa-dump-the-asteroid-mission-and-go-to-phobos-instead/Advisors to NASA: Dump the asteroid mission and go to Phobos instead
Posted on April 10, 2015 | By Eric Berger
"NASA has an asteroid problem.
It needs to fly missions that show it’s on a pathway to Mars, and that capture the public’s attention. And those missions need to be affordable. Finally, the missions should bring the space agency closer to landing humans on Mars."
Here's a good quote:
“To validate the SEP stage you don’t need to tow around a large rock,” Squyres said.
Another council member, former Goddard Space Flight Center director Thomas Young, was more blunt in his advice for NASA, “What we really should be saying is terminate ARM, take the $1.25 billion and apply it to the technology to get people to Mars. That’s the cold hard facts of what we’re saying.”
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#511
by
notsorandom
on 10 Apr, 2015 16:07
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I have been on the record as disliking this whole idea of ARM but am warming up to Phobos. Using SEP to bring back a large mass from Mars orbit would demonstrate returning a crew vehicle and likely getting one there in the first place. Propulsion is a major item on the to do list for Mars.
Phobos is also more scientifically interesting. When option B was announced they said there would be a full suite of scientific instruments on this craft. It has been hypothesized that there may be chunks of Mars that got flung on to Phobos. The moon could also itself be a chunk of Mars, the jury is still out on that. If there was a way for this craft to collect some targeted sample and not just a boulder this might be worthwhile. I don't see how it would be too hard to check out poor unloved Deimos along the way too. It would be a two for one deal on small bodies.
There is also the potential that it could return a sample from the surface should an accent vehicle be added. 2025 though is a bit soon under the notional Decadal Survey's plan and the MAV is still the most expensive part of that architecture. So I'm not goign to hold my breath on that one.
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#512
by
Graham
on 10 Apr, 2015 18:31
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#513
by
TrevorMonty
on 10 Apr, 2015 18:32
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The sample could be used for testing ISRU technology eg oxygen extraction.
No.
They're still only talking about a rock.
Next time you're near a body of water pick up a rock and take it home and try to extract water from it.
0xygen as in oxides, which makes up 90% of fuel by mass.
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#514
by
Graham
on 10 Apr, 2015 18:36
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I like this idea a lot more because it'll give us a good look at Phobos for the first time, all while helping validate SEP on its way to, at and on the return trip from Mars. Perhaps another possibility is to move a boulder from Phobos to a Mars orbit and then send a crew to Mars orbit and check it out. Probably be a heck of a lot more expensive, but it might be worth it. It would give an orbiting crew something to do, all while further validating the techniques that will be needed for a crewed Mars mission.
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#515
by
Blackstar
on 10 Apr, 2015 20:31
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The sample could be used for testing ISRU technology eg oxygen extraction.
No.
They're still only talking about a rock.
Next time you're near a body of water pick up a rock and take it home and try to extract water from it.
0xygen as in oxides, which makes up 90% of fuel by mass.
Oh, I see. It's like extracting oxygen from rust.
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#516
by
rcoppola
on 10 Apr, 2015 20:49
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Unfortunately this type of mission switch will need to wait until we have a new President and new Administrator. (And even then it is dependent on who they are)
I am certainly pleased to see this being aired publicly as well as the recent Lunar rumblings.
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#517
by
Robotbeat
on 10 Apr, 2015 23:59
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http://blog.chron.com/sciguy/2015/04/advisors-to-nasa-dump-the-asteroid-mission-and-go-to-phobos-instead/
Advisors to NASA: Dump the asteroid mission and go to Phobos instead
Posted on April 10, 2015 | By Eric Berger
"NASA has an asteroid problem.
It needs to fly missions that show it’s on a pathway to Mars, and that capture the public’s attention. And those missions need to be affordable. Finally, the missions should bring the space agency closer to landing humans on Mars."
Here's a good quote:
“To validate the SEP stage you don’t need to tow around a large rock,” Squyres said.
Another council member, former Goddard Space Flight Center director Thomas Young, was more blunt in his advice for NASA, “What we really should be saying is terminate ARM, take the $1.25 billion and apply it to the technology to get people to Mars. That’s the cold hard facts of what we’re saying.”
That's being "honest?" If they were being honest they would cancel SLS. $1.25 billion is nothing. Besides, doing just the SEP demo but not capturing a boulder and not doing any planetary defense demos is going to save you a fraction of that.
I still don't see any kind cogent argument there. "But it's not directly Mars" is not a real argument since it can test SEP tech just as well doing the boulder capture and planetary defense as it would going to Mars and back. NASA has other priorities, too, and this is a unique opportunity to get 3 or 4 birds with one stone of reasonable cost.
But I get it. It has become fashionable to oppose ARM, even though the reasons for doing so are either absurd or weak. Now that those arguments are falling apart, redirecting ARM to Phobos is a way for those people to not have to admit it's actually a good idea.
(Also, "cold hard facts"? poppycock. It's clearly just opinion, and not terribly well reasoned, either. Is that a good quote?)
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#518
by
jongoff
on 11 Apr, 2015 03:04
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The sample could be used for testing ISRU technology eg oxygen extraction.
No.
They're still only talking about a rock.
Next time you're near a body of water pick up a rock and take it home and try to extract water from it.
Umm...I don't think that is correct. AIUI, Phobos and Deimos are thought to be carbonaceous chondrites, which means that a properly selected boulder will likely also be of similar composition, and carbonaceous chondrites have non-trivial amounts of water mixed-in. Not as good as solid ice, but still potentially useful from an ISRU basis, unless I'm missing something.
~Jon
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#519
by
A_M_Swallow
on 11 Apr, 2015 03:16
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{snip}
ARM is one of those things that we need to develop in order to become a truly spacefaring species and be able to travel wherever in the solar system we please. ARM can certainly be improved, but I'm actually VERY impressed by the capabilities we'd get for just $1.25 billion.
For $2 billion can we build two space tugs?
Possibly send the first to collect a rock from the asteroid and the second to Phobos?