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#220 by MP99 on 20 Apr, 2010 06:41
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The total mass of the inner solar system asteroids (everything not a planet or moon inside of Jupiter) is just about 4% of the mass of the Moon. And half of that is in the four largest asteroids. In other words, the Moon isn't just big; it's bloody enormous.
The downside of which is that it's gravity well is deep, both directions, and has to be descended entirely propulsively. It's only virtue from an engineering-difficulty perspective is that it's short-duration, permitting open-loop life support.
Not the only virtue. Piled regolith can be used for radiation shielding. These both allow early, short-duration missions.
It is also possible to abort back to Earth in the event of an emergency. As an analogy, imagine trying to operate ISS without that Soyuz lifeboat!
CLLS & improved radiation shielding can be introduced and proved on later, longer duration missions.
It becomes a lot easier to countenance a 6-month-plus NEO mission once this low-TRL hardware has been refined and proved in Lunar missions. I shudder to think how bad the pLOC will be for the first NEO crew without a long programme of proving this hardware first.
cheers, Martin -
#221 by MP99 on 20 Apr, 2010 06:49
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Quote
Note that the planetary scientists themselves set scientific priorities via the decadal surveys, and apart from Lunar Prospector (pocket change), the US flew no pure science missions to the moon (IIRC?) between Apollo and LRO/LCROSS (which were themselves driven by the politics of Constellation). That speaks volumes about the priorities of the planetary scientists: Mars, NEOs, outer planets, inner planets, all above Luna. If that's changing for Astro2010, do tell.
No, that speaks volumes of what they thought they could get funded. Note that NASA successfully sent nothing to Mars between 1975 and 1996, a similar span of time between Apollo 17 in 1972 and Clementine in 1994. And both Clementine and Pathfinder were shoestring missions that barely made it to the pad.
I am an actual planetary scientist, a minor bodies specialist in fact, and can tell you that given the choice, the vast majority of us would never favor an unmanned mission to an asteroid over a manned one. The guaranteed return is just so much greater. However, because of the way NASA and NRC is set up, there is little opportunity to express this support. I was at several of the decadal survey meetings last fall and it was made clear that any manned missions or anything to do with CxP was beyond the scope of the survey. So don't take its lack to mean anything beyond bureaucratic baliwicks...
NASA's Flexible Path documents suggest that Humans would follow a robotic precursor - and they'd be doing different jobs.
Surely the problem justifying robotic probes to the Lunar surface is that Apollo has already plucked the sort of low-hanging fruit that they are capable of. The returned samples have been investigated in much more detail than on-board instruments could achieve.
cheers, Martin -
#222 by alexw on 20 Apr, 2010 07:46
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"Deep" is relative to the technology and mass ratios available. The V-2's mass ratio was, what, ~12:1? For hydrolox energy scales, aluminum-class structural materials, and modern launch costs and launch capacity (or launch rates, if you're using depots), I submit thatThe downside of which is that it's gravity well is deep, both directions, and has to be descended entirely propulsively.
No, Earth is deep gravity well. A circa-1944 V-2 could reach Earth from the surface of the Moon. It's not that hard. And anyone who tells you different is either an unimaginative engineer or a parrot.
it's reasonable to call climbing down and back from Luna's or Mars's gravity well as "deep". Even the basic TLI/TMI-class burn is ~50% fuel mass from LEO, no? What was the mass ratio of the Apollo CM vs. the SIVB stack in LEO? What are the mass ratios for the Mars HSF DRMs, or Mars sample-return? Can we do it at all, technologically? Yes. Can we afford it regularly? Not yet.Quote
Of course you can do science, tagging along on an HSF mission. All the Apollo guys did, I presume, especially the push for Harrison Schmitt. But is it remotely cost-effective for the science return?QuoteAgreed that Ceres would be fascinating, but if you want science, send robots. And, as the Obama plan provides funding for, do tech development missions like SEP and ASRG.
There is absolutely, positively not reason why you can't do science with a manned mission. It's just that NASA HSF is run by engineers who don't understand or care about science and just want to build big rockets and space stations and prop depots and figure out the uses later. The "Flexible Plan" is emblematic of this. It's like letting the inmates run the asylum!QuoteAnd we don't need extra funding for lab-bench test of SEP or Stirling engines. We know they work; there's an SEP rocket on its way to Ceres for goodness sake! What we need is actual missions using that technology. But that's too ambitious-sounding for this administration...
Agreed on the lab bench, but what we (seem) to need are actual flight demos to push the TRL level, so that missions and PIs are willing to sign up for it. Is this maybe a matter more of perception than reality, in some cases? Dunno. It's absurd that cryogenic fuel transfer has some semi-mystical status -- we've been doing it in the lab for a hundred years. It's "just" dewar bottles and stainless steel and vacuum transfer lines and a little He ullage gas. Apparently we need to fly a whole autonomous mission to prove it out. But the engineers retort that rockets and spaceflight fail for the simplest reasons, and the distance from the lab to the "it's foolproof" is a long long way.Quote
I think your example supports the point, actually. It's been asserted that shuttle starved out many science payloads in that timeframe. (It also took out the high-energy massy launch capability for flagship missions of Titan IIIE, and again with Centaur-G, a capability only restored to science in the last few years with Atlas V.) You could budget to fling a reasonable science payload on Delta-II, but the costs to land that kind of mass on the surface of the moon or Mars were too much. Pathfinder found a way to do it without a Viking-scale effort, twenty years later.QuoteNote that the planetary scientists themselves set scientific priorities via the decadal surveys, and apart from Lunar Prospector (pocket change), the US flew no pure science missions to the moon (IIRC?) between Apollo and LRO/LCROSS (which were themselves driven by the politics of Constellation). That speaks volumes about the priorities of the planetary scientists: Mars, NEOs, outer planets, inner planets, all above Luna. If that's changing for Astro2010, do tell.
No, that speaks volumes of what they thought they could get funded. Note that NASA successfully sent nothing to Mars between 1975 and 1996, a similar span of time between Apollo 17 in 1972 and Clementine in 1994. And both Clementine and Pathfinder were shoestring missions that barely made it to the pad.
Put another way, the science return from Venus Express has got to be a lot less interesting than from a Neptune Orbiter. But one is doable at reasonable costs, and one is not.QuoteI am an actual planetary scientist, a minor bodies specialist in fact, and can tell you that given the choice, the vast majority of us would never favor an unmanned mission to an asteroid over a manned one. The guaranteed return is just so much greater. However, because of the way NASA and NRC is set up, there is little opportunity to express this support. I was at several of the decadal survey meetings last fall and it was made clear that any manned missions or anything to do with CxP was beyond the scope of the survey. So don't take its lack to mean anything beyond bureaucratic baliwicks...
Glad to meet a fellow scientist on these threads. But I'm puzzled by your remark -- do you really assert that y'all would give up all of SMD for a decade just to land a pair of boots on Eros??
-Alex
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#223 by MP99 on 20 Apr, 2010 12:30
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"Deep" is relative to the technology and mass ratios available. The V-2's mass ratio was, what, ~12:1? For hydrolox energy scales, aluminum-class structural materials, and modern launch costs and launch capacity (or launch rates, if you're using depots), I submit that
it's reasonable to call climbing down and back from Luna's or Mars's gravity well as "deep". Even the basic TLI/TMI-class burn is ~50% fuel mass from LEO, no? What was the mass ratio of the Apollo CM vs. the SIVB stack in LEO? What are the mass ratios for the Mars HSF DRMs, or Mars sample-return? Can we do it at all, technologically? Yes. Can we afford it regularly? Not yet.
Yes, it's fairly deep (about 9 km/s for Human return, IIRC), but that's easily within range of a pair of SDLV launches, even using the Altair lander (and lets face it, that's pretty mass-inefficient).
There's something to be said for substituting brute-force heavy launch (that we can easily do) for technologies that we hope will become available in a decade or two's time.
cheers, Martin -
#224 by MATTBLAK on 20 Apr, 2010 12:33
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bleh. The Moon is a NEO. It's just regular. And big.
CORRECTION!! The Moon is a WORLD!!!
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#225 by Ben the Space Brit on 20 Apr, 2010 13:31
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Purely FWIW:
To me, the big advantage of NEO and other asteroid missions is that you can use broadly the same equipment on them as you do on lunar missions. You just use them in different ways. Instead of using the bulk of the propellent in the lander for lunar landing and ascent, instead you are using it for the ROI from the target object. Additionally, you can fit all the surface instrument packages and MMUs for asteroid exploration into the SEP racks on a lunar lander. You simply add harpoons to the landing struts of your lunar lander to make it small asteroid-ready.
The only significant unique mission component required for asteroid missions that cannot be used for lunar missions is the hab/consumables storage module. However, I suspect that this could potentially be a fairly simple vehicle, perhaps a modified ATV or even a Bigelow module mounted between the CRV and lander.
With smaller objects, you do not even have to undock the lander but simply 'dock' the entire stack onto the target object. With only theoretical levels of gravity, there would be no significant structural load issues involved with the lander being in contact with the object whilst the hab and CRV sit 'on top' of it.
Because of this, lunar and NEO missions go very well together. NEO missions without lunar landings do not go so well together and leave an 'exploration' program with big gaps. That is why "we've been there already" will soon be relegated to the same scrap-heap as "potatoe". The trick is to develop the hab and lander first and then tell Congress: "Oh, look! We can go to the Moon too! Cool!" -
#226 by Garrett on 20 Apr, 2010 13:55
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To me, the big advantage of NEO and other asteroid missions is that you can use broadly the same equipment on them as you do on lunar missions. You just use them in different ways.
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Not sure what you're saying. To me a NEO mission and a lunar mission are like apples and oranges, with only the launch vehicle and crew return vehicle being the same or somewhat similar. As would be the case for a mission to Mars.
- But a Moon mission does not require a hab for the trip, but does need one for the lunar base. The opposite is more or less true for an asteroid mission.
- A lunar mission requires a lander, an asteroid mission does not (in the usual sense).
- A lunar mission, to make long term economic sense, would have to part of a long term program to establish a permanent base on the Moon. Not so for an asteroid mission.
- science equipment for a lunar mission would probably be designed to stay on the Moon for a long time and be reused by future missions. Long term experiments could be carried out on the Moon, but a NEO mission might mainly be a "gather as much rocks as you can" mission.
- there's no need for asteroid rovers so no overlap there either with a lunar mission -
#227 by Nathan on 20 Apr, 2010 14:03
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Purely FWIW: The trick is to develop the hab and lander first and then tell Congress: "Oh, look! We can go to the Moon too! Cool!"
We shouldn't need "tricks". We should have a viable plan. -
#228 by Ben the Space Brit on 20 Apr, 2010 14:23
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Purely FWIW: The trick is to develop the hab and lander first and then tell Congress: "Oh, look! We can go to the Moon too! Cool!"
We shouldn't need "tricks". We should have a viable plan.
Why isn't this one viable? Seriously? We get lunar and asteroid capability and, thanks to the long-range hab, orbiter capability for the entire inner solar system. Unfortunately, drawing a slight veil over The Powers That Be's eyes so that we get as much capability before they realise that we've passed several possible cut-off points is a necessary survival tool.
@ Garrett,
I was focussing mostly on spacecraft. You can use the landing struts on a lunar lander (with harpoons) to 'dock' with a target small asteroid. By placing the spacecraft on the surface, you have virtually unlimited access to the surface as you will not need to cancel out the rotation of the object itself when moving around the surface. Of course, with the smallest (10-20m-class) meteoroid-sized NEOs, even a 'docking' is impossible. However, larger Earth-grazers could use a landing platform.
If you want to go into equipment specifics, it should be possible to modify some lunar SEPs for use on asteroids, both large and small. Naturally, some of the sensors would be unique to different classes of object. Some would be unique to just a single mission.
In all cases, 'flexibility' is the key word. As much Buck Rogers for as little buck as possible. Optimisation is a wonderful dream in a world of near-unlimited budgets but isn't ever really going to happen. Use common basic designs for the Mars and lunar habs. Base the asteroid lander on the lunar lander. Use aerocapture with any planet with an atmosphere. Use the MTV as the basis of an LEO-to-LLO shuttle. The list goes on. -
#229 by DigitalMan on 20 Apr, 2010 15:21
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Of course you can do science, tagging along on an HSF mission. All the Apollo guys did, I presume, especially the push for Harrison Schmitt. But is it remotely cost-effective for the science return?
Stephen Squyres recently said that the 5 years of science done by the Mars rovers could have been done in 1 week by a human. From this I would extrapolate that a mission lasting even a month would produce more science than decades of robotics.
It isn't reasonable to expect robotics to get all the answers for you or to do it in a reasonable timeframe, however robotics are necessary to find the places we need to go, and in other cases, (venus, etc.) telerobotics may be the only way humans will even get near it. -
#230 by alexw on 20 Apr, 2010 19:23
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And the MERs cost ~$1 billion combined and were on red soil in 2004, and the NASA DRM would come in at a good chunk out of a $trillion and two decades.Of course you can do science, tagging along on an HSF mission. All the Apollo guys did, I presume, especially the push for Harrison Schmitt. But is it remotely cost-effective for the science return?
Stephen Squyres recently said that the 5 years of science done by the Mars rovers could have been done in 1 week by a human. From this I would extrapolate that a mission lasting even a month would produce more science than decades of robotics.
Not even the same ballgame.
Also, the MERs are on (opposite) sides of the planet, and we don't yet know how to engineer human air transportation on Mars.
-Alex
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#231 by 2552 on 21 Apr, 2010 01:44
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The trick is to develop the hab and lander first and then tell Congress: "Oh, look! We can go to the Moon too! Cool!"
A lunar landing is not actually ruled out of the new plan, it just isn't the first destination. I remember Bolden saying in one of the hearings "and we are going back to the Moon". And Garver said in an interview with Popular Mechanics about a week before the speech:Quote from: Lori GarverThat exploration will include the government leading a return to the moon, visits to near-Earth asteroids and humanity's first steps on Mars.
Not necessarily in that order or course. Also, President Obama said in the speech:Quote from: Barack ObamaNow, I understand that some believe that we should attempt a return to the surface of the Moon first, as previously planned. But I just have to say pretty bluntly here: We’ve been there before. Buzz has been there. There’s a lot more of space to explore, and a lot more to learn when we do.
That doesn't rule out a lunar landing. -
#232 by vt_hokie on 21 Apr, 2010 01:56
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That doesn't rule out a lunar landing.
But it does rule one out before 2025, when he proposes the first exploration missions to asteroids. Basically, all of the goals are so far in the future, it's laughable. -
#233 by DigitalMan on 21 Apr, 2010 03:08
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Both robotics and HSF have their place. The FY11 plan is all about developing the infrastructure to enable regular human missions to places like mars in an affordable way.
If Congress instead chooses to stretch out budgets and drop critical research then I agree with you that talk of exploring Mars by humans is a nice goal but not realistic. Your budget argument only makes sense if we abandon attempts at new strategies (prop depots, cyclers, etc.) and try to go at it Apollo style.
And the MERs cost ~$1 billion combined and were on red soil in 2004, and the NASA DRM would come in at a good chunk out of a $trillion and two decades.Of course you can do science, tagging along on an HSF mission. All the Apollo guys did, I presume, especially the push for Harrison Schmitt. But is it remotely cost-effective for the science return?
Stephen Squyres recently said that the 5 years of science done by the Mars rovers could have been done in 1 week by a human. From this I would extrapolate that a mission lasting even a month would produce more science than decades of robotics.
Not even the same ballgame.
Also, the MERs are on (opposite) sides of the planet, and we don't yet know how to engineer human air transportation on Mars.
-Alex -
#234 by DigitalMan on 21 Apr, 2010 03:11
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I concur that lunar landings are not out since NASA discussed them on one of the conference sessions. What wasn't clear however was lander development, since they seemed to be most interested in inflatable descent technology that would seem to require an atmosphere.
The trick is to develop the hab and lander first and then tell Congress: "Oh, look! We can go to the Moon too! Cool!"
A lunar landing is not actually ruled out of the new plan, it just isn't the first destination. I remember Bolden saying in one of the hearings "and we are going back to the Moon". And Garver said in an interview with Popular Mechanics about a week before the speech:Quote from: Lori GarverThat exploration will include the government leading a return to the moon, visits to near-Earth asteroids and humanity's first steps on Mars.
Not necessarily in that order or course. Also, President Obama said in the speech:Quote from: Barack ObamaNow, I understand that some believe that we should attempt a return to the surface of the Moon first, as previously planned. But I just have to say pretty bluntly here: We’ve been there before. Buzz has been there. There’s a lot more of space to explore, and a lot more to learn when we do.
That doesn't rule out a lunar landing. -
#235 by yg1968 on 21 Apr, 2010 04:10
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It's probably been posted elsewhere but here is the flexible path video from NASA that was released on April 15:
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#236 by CessnaDriver on 21 Apr, 2010 05:19
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That doesn't rule out a lunar landing.
But it does rule one out before 2025, when he proposes the first exploration missions to asteroids. Basically, all of the goals are so far in the future, it's laughable.
Agreed. He might as well have promised stargates and warp drives.
It would be just as meaningful
Constellation at least had destinations and hardware being designed and worked on now. Not sure what start over and begin again in five years is supposed to accomplish other then waste more time.
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#237 by pathfinder_01 on 21 Apr, 2010 05:56
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That doesn't rule out a lunar landing.
But it does rule one out before 2025, when he proposes the first exploration missions to asteroids. Basically, all of the goals are so far in the future, it's laughable.
Agreed. He might as well have promised stargates and warp drives.
It would be just as meaningful
Constellation at least had destinations and hardware being designed and worked on now. Not sure what start over and begin again in five years is supposed to accomplish other then waste more time.
While I do agree about the long time frames I can think of several things that might be accomplished.
1. reduce the cost of manned spaceflight via commercial
2. Improve our technology so that we don't build stuff we can't afford yet(Apollo).
3. gain/expand capabilities in space like propellant transfer of cryogenics, and automatic docking(on larger craft).
Man spaceflight technology has been stagnate and I think new ideas/fresh approaches are needed. -
#238 by telomerase99 on 21 Apr, 2010 06:05
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If the abilities Pathfinder mentions are able to be developed during this five year period then we will be 30 years ahead of where we would have been had we continued to plow money into a solid rocket booster based capability that was plagued with problems.
It is a shame we did not begin this effort 4 years ago, but I guess its better to start late than never. -
#239 by Arthur on 21 Apr, 2010 13:28
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Both robotics and HSF have their place. The FY11 plan is all about developing the infrastructure to enable regular human missions to places like mars in an affordable way.
If Congress instead chooses to stretch out budgets and drop critical research then I agree with you that talk of exploring Mars by humans is a nice goal but not realistic. Your budget argument only makes sense if we abandon attempts at new strategies (prop depots, cyclers, etc.) and try to go at it Apollo style.
How is the FY11 plan affordable?
I am not just being critical of it, but I genuinely do not see any dramatic 'cost saving' advances to be made in a 5-10 year research program (at least none that are being seriously discussed in open debate).
A new Kerolox engine will perform in the same ballpark and for the same cost as existing hydrolox engines - certainly nothing here to reduce the cost per kg to LEO by even 20%. The total number of engines built would have more impact on the cost to orbit.
Super propulsions like Plasma and Ion are unsuitable for launch, thus of no impact until the 2025+ missions.
NTR are not under development (and for good reason) although these might change ISP enough to really impact costs.
The areas that COULD impact costs and ARE being discussed include EELV based Flexible Architectures and Fuel Depots. As far as I know, neither of these needs any real research.
If EELVs and Fuel Depots are the path forward, then why doesn't the FY11 plan just shift 5 years and start development right now. There are no technology 'game changers' on the horizon.
I don't see anything that will change the Augustine Commission cost estimates, so why burn Billions of dollars with unnecessary delays and useful - but not game changing - research.
