and that is a 100% perfect assessment of the situation, and totally agree.I might only add that they (HEOMD) might consider doing this if they could do a dual launch (launch of opportunity) for something else, like an empty depot, another spacecraft, or goodness knows what. But not likely.
Quote from: robertross on 09/26/2012 02:28 pmand that is a 100% perfect assessment of the situation, and totally agree.I might only add that they (HEOMD) might consider doing this if they could do a dual launch (launch of opportunity) for something else, like an empty depot, another spacecraft, or goodness knows what. But not likely.I do think it would be an interesting--possibly worthwhile--exercise to evaluate the benefits of heavy lift for planetary missions. I know of no detailed studies that have done it. When we did our assessment of Constellation for science, we didn't have any planetary missions to look at, so all we could really do was discuss the C3 and payload benefits without having anything more.Dual manifesting has some potential in niche cases, but would require study. There was a ridiculous study about five years ago called CEMMENT (Worst. Name. Ever.) that looked at the possibility of doing an engineering test of a human lander at Mars that would be loaded up with science experiments. The basic idea was reasonable, but they went crazy with it, thinking that because they would have a lot of payload and volume, they should fill it all up with sciency stuff. The end result was a science fiction fantasy, because there was no way that, even if they got the launch vehicle and lander for free, the science program could afford to build all the science spacecraft.
Quote from: Star One on 09/25/2012 09:34 pmWith that kind of price tag no one is going to fund this anytime soon are they?The quick answer is "no." The more complex answer is that OMB has apparently decided to not approve any flagships for planetary science, so it doesn't matter which ones get proposed, in what order, there is simply no support for doing it.
With that kind of price tag no one is going to fund this anytime soon are they?
I don't know if a study was done per se, but using the Ares V (more like Ares VI...hehe) for science missions was definitely persued (more like flaunted) by NASA (obviously to gain support). Those docs are here on the public side or the L2 side.Edit: here it is:http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070038373_2007037046.pdf
1-Interesting that the mission can be traded to solar.2-The decadal survey says so. No MSR = Europa. That's the flagship priority. The MSR guys just can't let go yet.3-I mean that's the whole reason for having something like SAM isn't it? So you can test the rocks at Mars without bringing them back.
I still think about the C3 benefits of a Heavy launcher (or a depot architecture). How do you trade the possibility of basing one mission on the results of previous one? If you have 6 to 8 years of travel, you can't get more than one mission per decade, if you are lucky, that need the previous one. On the other hand, at 2 to 3 years of transit, you can do twice the number. It get's interesting if you can use the previous missions assets. Say you want to send a lander to Europa. Communications with Earth is very difficult. May be, if it only has to wait for five years, there's a way to put it on hibernation and use the orbiters communication capabilities to support the lander. But if it took longer, the degradation would be too great, even in case of hibernation and protecting shrouds.On hte other hand, a heavy launcher could send the communication orbiter AND the lander on the same mission. I'm just trying to get creative.
Quote from: baldusi on 09/27/2012 10:23 pm[...]I think that is the kind of trade it would be interesting to perform. But the key trade to explore would be cost reduction in missions. For instance, if you decrease the transit time and increase the mass margins and fuel margins and things like that, could you bring the cost of the mission down significantly? I've only seen very thin speculation about this, but nobody has actually gone into it in any depth.
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1-My intuition, is that any sort of increase in structural or payload mass due to lowering the cost, will be offset by the increased fuel and thrust increase needed. After all, the rocket formula is exponential on the pmf. Besides, AFAIK, the bulk of cost it on certification and testing, not on the materials themselves.2-The other issue, and I think this is the core issue, is: how do you keep the scientists and engineers from adding features and science payload that actually increases the cost since they have weight and volume to spare? In other words, if the budget was made reasonably, the biggest danger is the project management's own desire for a better mission.
Quote from: baldusi on 09/28/2012 08:11 pm1-My intuition, is that any sort of increase in structural or payload mass due to lowering the cost, will be offset by the increased fuel and thrust increase needed. After all, the rocket formula is exponential on the pmf. Besides, AFAIK, the bulk of cost it on certification and testing, not on the materials themselves.2-The other issue, and I think this is the core issue, is: how do you keep the scientists and engineers from adding features and science payload that actually increases the cost since they have weight and volume to spare? In other words, if the budget was made reasonably, the biggest danger is the project management's own desire for a better mission.1-I don't think that's an issue here because the initial margins are so huge. We're talking about throwing a relatively small spacecraft to the outer planets. With a heavy lift vehicle you can easily throw twice the mass. So if you give the designers 50% more margin to play with, the other penalties don't really bite.
2-Yes, that is an issue. But you're going to be cost constrained from the start. The way to do the initial trade is to take a spacecraft designed for a smaller vehicle and then tell the designers "You cannot add instruments, but you can add mass, fuel, operations, and other margins." I imagine that in some missions that would cause the scientists to hyperventilate and faint because they'd love to have those things even without more instruments. For example, the key limitation is radiation. If you told the scientists that instead of a 180 day mission they could have enough shielding for a five-year mission, they would be more than happy.
Quote from: Blackstar on 09/28/2012 09:03 pmQuote from: baldusi on 09/28/2012 08:11 pm1-My intuition, is that any sort of increase in structural or payload mass due to lowering the cost, will be offset by the increased fuel and thrust increase needed. After all, the rocket formula is exponential on the pmf. Besides, AFAIK, the bulk of cost it on certification and testing, not on the materials themselves.2-The other issue, and I think this is the core issue, is: how do you keep the scientists and engineers from adding features and science payload that actually increases the cost since they have weight and volume to spare? In other words, if the budget was made reasonably, the biggest danger is the project management's own desire for a better mission.1-I don't think that's an issue here because the initial margins are so huge. We're talking about throwing a relatively small spacecraft to the outer planets. With a heavy lift vehicle you can easily throw twice the mass. So if you give the designers 50% more margin to play with, the other penalties don't really bite.But more mass means higher thrust engines. Higher mass means higher momentum of inertia, thus, bigger reaction wheels and thrusters, plus thruster fuel, etc. Bigger fuel tanks in relation to the payload also means a more over sized control authority when the tanks are near empty, thus requiring higher precision firings and more sophisticated control. Then you have to certify and test everything. I seriously doubt you would save much. The only way I see this saving money is if they can use a legacy platform and parts that are already designed and certified for the expected environment. If said parts and/or platform was too heavy for the "small" LV, then yes, using a more powerful rocket might actually lower the cost. But you won't save much, if anything, by doing it custom.You know very well that planetary missions have very particular requirements that nobody else needs. You have to tolerate the environment from Venus to the outer planets (if you do a VVEGA maneuver), the radiation degradation environment is unique to deep space probes, and the thermal environment is very particular. You might save a bit if you can use a bigger LV to save the Venus Gravity assist, and thus you don't have to design for that thermal environment. Of course, we are talking about a mission already planned with a conservative estimation and good margins. If you want to put a 2.5tonnes mission on a 1.9tonnes LV, of course it's going to be cheaper to put it on a bigger LV than making enough technological advances to reduce the weight enough. But going from an EELV to SLS the jump in performance is so huge, that's not the case.Quote2-Yes, that is an issue. But you're going to be cost constrained from the start. The way to do the initial trade is to take a spacecraft designed for a smaller vehicle and then tell the designers "You cannot add instruments, but you can add mass, fuel, operations, and other margins." I imagine that in some missions that would cause the scientists to hyperventilate and faint because they'd love to have those things even without more instruments. For example, the key limitation is radiation. If you told the scientists that instead of a 180 day mission they could have enough shielding for a five-year mission, they would be more than happy.I quite get how it would be ideally. But you have to plan the system for the "misbehaving". And in any case, more mass usually means more cost. You can add some layers of composite Ti/Br to protect the electronics. But then you have to actually certify that for a five year radiation and thermal environment. That means weeks, if not months on environmental testing chambers and more time in from of the accelerator. And then, how do you protect your sensors? You added protection to your electronics but now you have to develop hardened sensors, which you can't protect unless you don't want to get any reading. Might be an option if you want to take extended time domain samples. But then you have to design, certify, integrate and test a sensor protection system. More money and complexity.And again, I think you can do that if you jump from an Atlas V531 to a 551. But even from a Falcon Heavy to SLS there's so much differential, that I can't think of any use save delta-v that will be "cheaper".
But NASA is also thinking about ways to investigate the possible habitability of Europa, Jupiter's fourth-largest moon. One concept that may be gaining traction is a so-called "clipper" probe that would make multiple flybys of the moon, studying its icy shell and suspected subsurface ocean as it zooms past."We briefed [NASA] headquarters on Monday, and they responded very positively," mission proponent David Senske, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said here Dec. 7 at the annual fall meeting of the American Geophysical Union.
The chronic mechanical problems plaguing the scientists drilling that frozen lake in Antarctica don't bode well for the classical sci-fi notion of drilling the ice sheet on Europa. That kind of mission seems to be well beyond our near-term capabilities.