I'm surprised to hear Option A might be slightly cheaper, although obviously they were ambiguous about whether they favored one or the other.
I'm not happy they just deferred the decision until January...then again considering January is barely 3 weeks away it could have been a longer delay. At best, I think this asteroid project is entering a countdown that times out on January 20, 2017 when Obama leaves office. Unless they cobble something together impressive, there will be a decisive change of tune.
I sympathize with NASA being cautious between Obama's orders, working with Orion's inherent limitations, and an unimpressed Congress...but they need to start making hard decisions especially if they want ARM to fly along with SLS and Orion.
...all the same personally, I doubt this will fly off the drawing board in the end.
I have high hopes that it will be done. If not ARM, then what for the same $ that utilizes SLS/Orion at this early stage?
{snip}
One of the issues I have with ARM is that it's a one-off. There'd be a good bit of tech development enabled by the robotic part of the mission, so that's a plus, but there's no "next step" using that tech (if people travel to an asteroid on SLS, I suspect there won't be a robotic precursor or need to grab meter-sized boulders, though perhaps I'm wrong). At least if a hab module was designed and built, you'd have that. I do not hope for a reusable one that stays in space, for hope has forsaken these lands, but maybe a low-cadence assembly line could get started. Maybe use the first as a pathfinder (semi-functional) for a long duration hab as will be needed for really deep space missions. Or just pay ESA for a few ATV knockoffs and use those.
Planetary defence requires later missions to catch and divert increasingly larger asteroids. This continues until we can successfully divert asteroids that are a danger to the Earth.
I agree 100% that what you say needs to be done. But the ARM is not part of a clear, funded, endorsed program to do it. If the point of the ARM is to demonstrate moving a small asteroid (which is, IMHO, a reasonable step in an overarching plan) I am simply not convinced that astronauts need to be involved.
If the goal of ARM is to do *something* with SLS and Orion, it's about all that can be hoped for, for the next 10-15 years, and that assumes the robotic part is funded and works. But if the goal is asteroid defense, then build the pusher to show the capability to move an asteroid, and leave out the astronaut part of ARM and use the money to fund Sentinel and swarms of smallsats to investigate the diverse population of asteroids.
Of course, without the astronauts, the robotic part of ARM isn't going to happen, and not the rest, either. So this is make-work. Probably, I should applaud something useful happening, but when it costs 10x what it needs to, that is hard for me to do.
I seriously don't understand the reasoning behind our vacation plans; why drive the car all the way to Florida, just to send the kids to see a few guys in fluffy costumes? If entertaining the kids is the goal, surely it'd be far simpler and more cost-effective to turn on the tv and change to the Disney channel. (I'd bet you could get more fluffy costumes that way).
{snip}
Or... instead of moving the NEO to lunar orbit, why not move it to LEO where it can be studied in detail (perhaps at ISS?) The delta/v needed (sans aerobrake) would be higher, so get a smaller NEO (though still far larger then the samples the current ARM plan could return with). But, why omit aerobraking? Enter a high apogee, low perigee orbit with the perigee at about 100 miles, and it ought to be possible for the spacecraft to endure repeated passes without the need for a heat shield. You need about .7 kps to go from earth C3 to either lunar orbit or a GTO, so I can't see the delta/v budget being all that different for the retreval mission with a destination of LEO rather than lunar orbit (assuming multipass aerobraking is used to change your GTO to LEO).
{snip}
Exit question; how large (roughly) is the mass and diameter of the rock they aim to retrieve (be it a boulder or a very tiny asteroid)? I can't seem to find numbers for this, though if one of NASA's "artist's conceptions" showing Orion docked to the retrieval spacecraft is any indicator, the rock in question is smaller than the Orion capsule.
Exit question; how large (roughly) is the mass and diameter of the rock they aim to retrieve (be it a boulder or a very tiny asteroid)? I can't seem to find numbers for this, though if one of NASA's "artist's conceptions" showing Orion docked to the retrieval spacecraft is any indicator, the rock in question is smaller than the Orion capsule.
Some presentations here: http://www.nasa.gov/content/asteroid-initiative-related-documents/
Bag option seems to be up to 10m diameter, 1000 tons
Boulder option 1.5 - 2.5m diameter, 5-30 tons
Retrieval capacity seems to be sensitive to schedule (more time = bigger rock).
{snip}
Or... instead of moving the NEO to lunar orbit, why not move it to LEO where it can be studied in detail (perhaps at ISS?) The delta/v needed (sans aerobrake) would be higher, so get a smaller NEO (though still far larger then the samples the current ARM plan could return with). But, why omit aerobraking? Enter a high apogee, low perigee orbit with the perigee at about 100 miles, and it ought to be possible for the spacecraft to endure repeated passes without the need for a heat shield. You need about .7 kps to go from earth C3 to either lunar orbit or a GTO, so I can't see the delta/v budget being all that different for the retreval mission with a destination of LEO rather than lunar orbit (assuming multipass aerobraking is used to change your GTO to LEO).
{snip}Because the NEO is no where near LEO. The delta-v from Earth C3=0 to the Lagrange points may be 0.14 km/s but the delta-v C3=0 to LEO is a gigantic 3.22 km/s. Aerobraking a NEO without a heat shield will destroy it and probably take several years.
There's lots of analogies for people confusing science results with the purpose of "exploration" missions.
Exit question; how large (roughly) is the mass and diameter of the rock they aim to retrieve (be it a boulder or a very tiny asteroid)? I can't seem to find numbers for this, though if one of NASA's "artist's conceptions" showing Orion docked to the retrieval spacecraft is any indicator, the rock in question is smaller than the Orion capsule.
Some presentations here: http://www.nasa.gov/content/asteroid-initiative-related-documents/
Bag option seems to be up to 10m diameter, 1000 tons
Boulder option 1.5 - 2.5m diameter, 5-30 tons
Retrieval capacity seems to be sensitive to schedule (more time = bigger rock).
There's lots of analogies for people confusing science results with the purpose of "exploration"
Exit question; how large (roughly) is the mass and diameter of the rock they aim to retrieve (be it a boulder or a very tiny asteroid)? I can't seem to find numbers for this, though if one of NASA's "artist's conceptions" showing Orion docked to the retrieval spacecraft is any indicator, the rock in question is smaller than the Orion capsule.
Some presentations here: http://www.nasa.gov/content/asteroid-initiative-related-documents/
Bag option seems to be up to 10m diameter, 1000 tons
Boulder option 1.5 - 2.5m diameter, 5-30 tons
Retrieval capacity seems to be sensitive to schedule (more time = bigger rock).
Huh. We were designing for a 3.75m diameter boulder (about 90mT assuming 3.3tonne/m^3 rock) for our "Option B" ARM BAA design point. Now, I don't know if the rest of the system can handle that size with realistic destination asteroids, etc., but 1.5-2.5m is a lot smaller than what we've been focused on.
Heck, the 1G ground test prototype we're building is sized for a 1m diameter boulder...
~Jon
Then what, exactly, is the purpose of the ARM? The claims are science, and pathway to Mars, and being "exploration".
So, if we rule out science, then we're looking at pathway to Mars (or other deep space destinations) and the only component of the ARM that's plausibly related to that is the SEP system for the retrieval probe. If we accept that assumption, an all-robotic sample return mission fulfills the requirement.
If "exploration" is the main goal, then moving the rock to earth-sun L2 would IMHO make more sense than what's planned. (Unlike lunar orbit, we haven't sent a manned mission there, and it's beyond cislunar space - a true "deep space" mission), as well as slightly easier on the retrieval probe's delta/v budget. (Depending on the original orbit of the rock, IMHO L1 might be a better choice from a delta/v perspective).
There's lots of analogies for people confusing science results with the purpose of "exploration"
I'm not one of those people, thanks. But spending billions of dollars to have two people spend a day or two chipping at a floating rock, which they won't even see except through a hole cut in a plastic bag, doesn't strike me as very exciting "exploration." I am willing to grant, however, that it's the best SLS+Orion will give us for the next 15 years. On whether it meets the excitement standard for exploration, well-meaning people may disagree.
Exit question; how large (roughly) is the mass and diameter of the rock they aim to retrieve (be it a boulder or a very tiny asteroid)? I can't seem to find numbers for this, though if one of NASA's "artist's conceptions" showing Orion docked to the retrieval spacecraft is any indicator, the rock in question is smaller than the Orion capsule.
Some presentations here: http://www.nasa.gov/content/asteroid-initiative-related-documents/
Bag option seems to be up to 10m diameter, 1000 tons
Boulder option 1.5 - 2.5m diameter, 5-30 tons
Retrieval capacity seems to be sensitive to schedule (more time = bigger rock).
Huh. We were designing for a 3.75m diameter boulder (about 90mT assuming 3.3tonne/m^3 rock) for our "Option B" ARM BAA design point. Now, I don't know if the rest of the system can handle that size with realistic destination asteroids, etc., but 1.5-2.5m is a lot smaller than what we've been focused on.
Heck, the 1G ground test prototype we're building is sized for a 1m diameter boulder...
~Jon
The presentation I was looking at is old. I'm sure you have better information.
There's lots of analogies for people confusing science results with the purpose of "exploration"
I'm not one of those people, thanks. But spending billions of dollars to have two people spend a day or two chipping at a floating rock, which they won't even see except through a hole cut in a plastic bag, doesn't strike me as very exciting "exploration." I am willing to grant, however, that it's the best SLS+Orion will give us for the next 15 years. On whether it meets the excitement standard for exploration, well-meaning people may disagree.
Just so we're clear, you don't think "science" is the purpose of "exploration" but you do think excitement is?
It's not bread, it's circuses?