I have a piece up at Popular Mechanics about the AIAA conference this week, and ULA’s non-heavy-lift architecture. Hell hath no fury like a rocket company scorned.
Meanwhile, it looks like there may be a battle in Congress to preserve the Ares pork. At some point, though, they’re going to have to confront budgetary and programmatic reality.
[Noon update]
Here is the permalink.
[Another update a few minutes later]
Paul Spudis has a longish essay on the history of the VSE, how NASA mangled it, and what we need to do going forward.
Excellent insights on the effects of the ULA paper, Rand. I have distributed as many of the ULA graphics as I can to builders in Second Life, and anyone may soon be able to see them in 3-d there, at the National Space Society Island, or maybe a nearby island where our NSS Mass Driver can launch lunar oxygen capsules to it.
Some of the pork may be directed in a more fruitful direction. J2X could be replaced with RL-60, AIUS with ACES, the 5 seg SRB with Delta/Atlas configurations with more solids, CECE with a new US kerolox engine. All luxuries of course, but at least they wouldn’t be harmful.
Martin makes a good point. Someone ought to be lobbying harder to have pork spent on more useful things. Until we have real campaign finance and electoral reform pork isn’t going away, so it might as well be helpful.
@ Paul Spudis:
Let there be no misunderstanding. No one knows if the use of space and lunar resources is even possible, let alone whether it can be done “for profit” (defined here as giving you more capability somewhere than you could obtain for equal expenditure of launching the same materials from the surface of the Earth.) It could well be that given the operational difficulties, power requirements, or nature of the lunar surface that using these resources may not be feasible. But it is NASA’s task to try and answer this question with both technical detail and financial fidelity.
I agree 99% …
Players other than NASA should also be encouraged to ascertain whether such things are feasible.
That said, if profitable lunar ISRU is feasible, then EML-1 and EML-2 are the most valuable points in all of cis-lunar space. If a robust human lunar presence emerges, owning a depot facility at either of those locations would be immensely profitable.
Why? Because I agree with Dr. Spudis 100% on this:
Cargo can be transported out of LEO using efficient but slow, solar electric propulsion to the Earth-Moon Lagrange point, either L1 or L2, depending upon the trade studies. Crew can follow in faster, chemical rocket transports. At least two different sized landers should be developed. A small, 1-2 mT class cryogenic lander can deliver robotic rovers, surveyors, and resource demonstration landers. After outpost establishment, it can be used in the same manner as the Russian Progress spacecraft are now used to resupply ISS. It can also deliver science payloads around the Moon after being re-fueled with lunar propellant. For human missions, a permanent, reusable lunar lander should be developed. It need not be a 50 mT behemoth; a smaller 20-30 mT lander would suffice. Its only purpose is to transport humans and high-value cargo down to the lunar outpost and back. Initially it will be fueled from the depot established at the L1 staging node; ultimately, we want to fuel it with lunar-produced propellant.
That said, whether NASA the right player to do this is a different question.
Also @ Paul Spudis
If a Shuttle-derived heavy lift is easily and cheaply done, it should be used. If not, scrap it. Existing EELV can put about 25 mT in LEO; through the use of such features as propellant depots, a lunar return architecture could be designed around these launch vehicles. Rockets should be the means, not the ends of space faring. Our quest is to free ourselves from their more onerous constraints as quickly as possible.
Again, I agree.
Direct 3.0 as well as ULA’s proposal need to be transparently evaluated without ideological blinders either in favor or or against heavy lift. An EML transfer station + RLL (reusable lunar lander) architecture would be very well served by Jupiter launch vehicles augmented with depots.
The part of the Paul Spudis essay I find interesting
“The International Space Station (ISS) is an asset whose potential for creating space faring infrastructure remains unrealized. In addition to its possible use as a staging node to points beyond LEO, it could become a technology test-bed, allowing us to obtain valuable experience with a variety of technologies essential for sustainable spaceflight. Much of this research involves understanding the issues and mitigating the problems of handling and using cryogenic liquids in microgravity. ”
Why aren’t we doing that on the ISS? If we are doing that on ISS, why haven’t we heard about it?
Paul M. says, quoting Paul Spudis “” Much of this research involves understanding the issues and mitigating the problems of handling and using cryogenic liquids in microgravity. ”
Why aren’t we doing that on the ISS?”
3 reasons:
The least important but most immediate is lack of money when all ISS money was going into getting ISS complete.
Of middling importance is that the tasks themselves are handled outside in vacuum, and all EVA work is considered dangerous, so projects needing an Astronaut out in vacuum doing it are not well looked upon by many.
Of most importance is that these very technologies are precursors and enablers for Propellant Depots, which the most powerful people in NASA rejected for decades, because they would make heavy-lift rockets obsolete. It is no accident that the first post-Apollo 11 plan from NASA involved launching Saturn Vs until sometime past, …oh, …about 1990, IIRC. This was to amortize not only the development costs of the huge rockets, but those of the huge ground equipment needed to handle them at Kennedy Space Center, and incidentally make the people involved with the Saturn V look really smart.
Propellant Depots were rejected for Apollo, in large part, because NASA would not then require a Saturn V to get to the Moon, as well as the need to learn freefall propellant cryogenic handling in vacuum taking time that *might* have pushed them beyond 1969 for the landing. NASA hierarchs have not yet shifted from their 1969 mode 40 years later. That is the biggest reason that propellant depot-enabling technologies have not advanced.
No one knows if the use of space and lunar resources is even possible, let alone whether it can be done “for profit…” But it is NASA’s task to try and answer this question with both technical detail and financial fidelity.
NASA is the wrong organization to decide whether *anything* can be done profitably.
A small, 1-2 mT class cryogenic lander can deliver robotic rovers, surveyors, and resource demonstration landers…. For human missions, a permanent, reusable lunar lander should be developed. It need not be a 50 mT behemoth; a smaller 20-30 mT lander would suffice.
20-30 metric tons *is* a behemoth. The Russian LK lunar lander was only 5.5 metric tons and the Gemini bug just over 4 metric tons. Langley designed one-man landers as light as 1 metric ton.
Even the Apollo lunar module was just 14.7 metric tons.
Paul’s gone right back to the Bush Vision, which called for a long series of unmanned probes before humans were allowed to go.
Note that MSFC estimated the first of those unmanned probes at over $2 billion. For that price, NASA could pay the Russian Space Agency to take the LK lander out of storage and send an astronaut to the Moon.
If human exploration were considered as important as robots, that is.
An EML transfer station + RLL (reusable lunar lander) architecture would be very well served by Jupiter launch vehicles augmented with depots.
Of course, NASA will have to cancel the depots to pay for your Jupiter launch vehicle. Along with COTS and anything else they can think of.
Or are you still under the delusion that Obama is going to give NASA unlimited funding?
Assuming change is again imposed upon NASA, how long before they again ignore/frustrate it?
Propellant Depots were rejected for Apollo, in large part, because NASA would not then require a Saturn V to get to the Moon, as well as the need to learn freefall propellant cryogenic handling in vacuum taking time that *might* have pushed them beyond 1969 for the landing. NASA hierarchs have not yet shifted from their 1969 mode 40 years later. That is the biggest reason that propellant depot-enabling technologies have not advanced.
OK, here’s a question about Constellation and Apollo and 1969 architecture: *IF* we are able to set up a propellant depot in lunar orbit or at EML, can we do away with the super-robust Orion capsule that returns astronauts from lunar orbit directly to Earth? In other words, if you can refuel your spacecraft in lunar orbit, why use a ship that consists of a CSM that gets thrown away and a re-entry module that might never be used again? (Is the Orion capsule intended to be re-used?)
Why not go back to the architecture of 2001: A Space Odyssey with a deep space craft that departs from LEO, goes to the Moon using a rocket engine to accelerate and decelerate, refuels from a depot in lunar orbit, and then, using that same rocket engine to accelerate and decelerate, heads back to LEO for a rendezvous with a space station in LEO where it can be refueled for another round trip?
Has anyone investigated the feasibility of this architecture since the days of Apollo, and if so can you point me to a study or at least a summary? Yes, I realize the feasibility critically depends on the existence of lunar fuel depots, but aren’t they on the table now?
Edward Wright wrote:
I think you’re forgetting that the Apollo LEM wasn’t reusable, and more than half of its empty mass was left behind on the surface of the Moon. Spudis is talking about a single vehicle that does not separate into a descent stage and an ascent stage, so it has to lift its descent fuel tankage and its landing gear back to lunar orbit. He’s also talking about a vehicle made from something a bit more durable than tinfoil. 20 to 30 tonnes seems like a reasonable mass for such a vehicle.
A short list of some things needed for space settlement (others?):
Very large habitats – lots of people
Hanger workshops
Farming (food self sufficiency)
Low launch costs
Transport infrastructure
Orbital assembly
Megawatt scale lightweight low cost solar power
High ISP rockets
Artificial gravity (spinning habitats)
Radiation resistance
Interestingly, none of these actually require extra terrestrial resources, though they might help. High ISP rockets necessary for getting around would presumably enable retrieval of desired resources from NEOs. I am not sure that NASA is really working on any of these.
I think you’re forgetting that the Apollo LEM wasn’t reusable, and more than half of its empty mass was left behind on the surface of the Moon. Spudis is talking about a single vehicle that does not separate into a descent stage and an ascent stage,
I think you’re forgetting I gave you four data points — not just one.
The Gemini bug didn’t separate into a descent stage and an ascent stage. Nor did the Langley 1-ton lander.
Nor did the Human Lunar Return lander, which was 4.5 metric tons, if you want something a bit more modern.
He’s also talking about a vehicle made from something a bit more durable than tinfoil. 20 to 30 tonnes seems like a reasonable mass for such a vehicle.
When did I propose using tinfoil, Mike? That’s a strange material to construct your strawman out of.
The Human Lunar Return lunar lander *and* habitat module had a mass of only 6 metric tons *combined.* HLR used composites and inflatable structures but no tin foil. Sorry.
Ed,
If you really want to hammer home the point, just refer people to this page in Encyclopedia Astronautica…
http://www.astronautix.com/craftfam/lunnders.htm
…and, more specifically, this one…
http://www.astronautix.com/craft/lev.htm
…which has some rather interesting mass estimates in the last paragraph for the dry vehicle and payload mass.
Once you accept that you don’t need to launch the element fully loaded with propellant, the “minimum” mass restrictions on the launcher can reduced significantly (i.e. well below 10 metric tons).
A question: The cited report advocates depots in LEO and at L-2. What’s the advantage of L-2 over L-1?
Paul’s gone right back to the Bush Vision, which called for a long series of unmanned probes before humans were allowed to go.
Yes, because I think the original Bush VSE was pretty good. It’s what NASA has done to it that makes it unworkable.
Note that MSFC estimated the first of those unmanned probes at over $2 billion. For that price, NASA could pay the Russian Space Agency to take the LK lander out of storage and send an astronaut to the Moon.
You’re wrong about the cost of t5hat mission; various options were examined, ranging in cost from $300 M to $1.6 B. The high end mission was for a nuclear-powered rover put on the Moon by a cryogenic-fuel lander that could deliver up to 1.5 mT per landing. The lander recurring costs would be a couple hundred million and could both emplace robotic assets on the Moon for future use, demo ISRU experiments, and later serve as an outpost re-supply vehicle, all launched on an EELV.
In the 4 years since that study, NASA has spent almost $35 B on Constellation and we have nothing to show for it. Even if the Stick works, we’re still stuck in LEO.
The “tinfoil” remark is not a straw man.
The LM had serious problems with its weight budget, and to get to the Moon, the Apollo program had the LM contractor embark on a “super weight reduction program” that famously shaved the walls of the LM cabin to the point that they were indeed a heavy grade of “aluminum foil.” Michael Collins in his book remarked that one could put one’s hand through a wall if one did not exercise care.
Whether you could really punch your hand through the wall of the LM or whether you needed a sharp object to do that level of dangerous vandalism is something I don’t know, but the astronauts had remarked that the LM cabin separating them from space vacuum was shaved down to the bare essentials.
On the other hand, some of the Lunar Bug proposals had the astronauts out in the open, where the entire lunar descent, visit, and ascent was “EVA inside space suits”, and in that case you don’t even have the weight of the “tin foil” pressure cabin. Or the environmental controls.
But the LEM used it. Take a look, Edward:
http://www.reformation.org/lunar-lander2.jpg
What’s the advantage of L-2 over L-1?
Lower delta-v for a ~9 day trajectory, which might be acceptable for crew. Slower trajectories for cargo have similar cost to EML1/2 and SEL1/2. A 3 day direct trajectory to L1/L2 would be more expensive than the 9 day trajectory to L2.
But the LEM used it. Take a look, Edward:
And from that single data point, you conclude that every lunar lander must use it?
Edward-
I think the original point was that a reusable lander WOULDN’T use tinfoil. It would need to be more substantial. In response to your other examples, I think that a reusable lunar lander would also need a pressurized section.
I think the original Bush VSE was pretty good. It’s what NASA has done to it that makes it unworkable.
The Bush Vision of Space Exploration specifically placed NASA in charge of all space exploration.
If you read the President’s speech and the accompanying fact sheet, you will find no mention of any role for the military, private enterprise, or any other government agency.
The Aldridge commission declared that human spaceflight would “remain the province of government” for the forseeable future — the week *after* Mike Melvill earned his commercial astronaut wings by flying SpaceShip One. That’s not exactly 20/20 vision.
It’s irrational to say you support a policy that placed space exploration entirely in the hands of NASA, then say NASA was the sole cause of the policy’s failure.
In the 4 years since that study, NASA has spent almost $35 B on Constellation and we have nothing to show for it.
Is that surprising? The Bush approach to every problem was to throw huge amounts of money at it. Why would you expect the Bush Vision of Space Exploration to be any different?
Even if the Stick works, we’re still stuck in LEO.
Ah, the “LEO is a dump” meme again. 🙂
No, Paul, you aren’t stuck in LEO. You’re stuck in Houston. The humidity alone should be enough to prove that.
Who, exactly, do you think is “stuck in LEO?” Not the ISS astronauts — they’re all volunteers who wanted to be there. Not your robots — didn’t you work on that Indian satellite that went to the Moon?
Right now, people are working hard to build affordable suborbital vehicles. There’s a long waiting list of people who want to go to ISS. If LEO is so awful, why do all the astronauts (except Jerry Linenger) come back talking about what a great time they had there?
Do you expect people to throw money at you merely because you complain about being “stuck” someplace that *most people would dearly love to go to but can’t afford*???
I think the original point was that a reusable lander WOULDN’T use tinfoil. It would need to be more substantial. In response to your other examples, I think that a reusable lunar lander would also need a pressurized section.
Tom, spacesuits are pressurized, they’re reusable, and anyone going to the Moon is going to need to have one anyway. Why not use those as the “pressurized section”?
What’s the point of carrying a heavy pressurized habitat up and down on every flight? If you’re going to deliver a habitat module to the Moon, why not leave it there?
OK, Edward. I sort of see where you’re coming from. My gut still tells me that spacesuit-only descent to the moon is a bad idea (a couple issues include travel time from an L-point (or orbit), leading to spacesuit design issues as well as a near-immediate need to ‘run’ for the habitat after arrival), but I’ll put some gray matter into it if I get the chance.
I should have realized that I was wasting my time to attempt a rational conversation with you, Edward. My mistake.
Tom, spacesuits are pressurized, they’re reusable, and anyone going to the Moon is going to need to have one anyway. Why not use those as the “pressurized section”?
Spacesuits are not actually the most efficient of pressure vessels. For the weight of a space suit one could construct a cockpit sized inflatable pressure vessel that would perhaps be safer and more comfortable.
A double wall raw envelope two meters long by one meter in diameter might only weigh two kilograms – windows and shielding are extra, an airlock might be little more than a fancy zip. Pressurized habitat modules do not need to be heavy.
Pete, what you missed that the person landing on the moon will likely need to have the suit _anyway_. Whether the suit is most efficient pressure vessel is irrelevant.
Spacesuits are not actually the most efficient of pressure vessels. For the weight of a space suit one could construct a cockpit sized inflatable pressure vessel that would perhaps be safer and more comfortable.
But the weight of the spacesuit can’t be avoided. Even with a pressurized lander, the astronaut has to have a spacesuit, or what is he going to do on the Moon? Sit and look out the window?
A double wall raw envelope two meters long by one meter in diameter might only weigh two kilograms – windows and shielding are extra, an airlock might be little more than a fancy zip.
Two kilograms seems low. The NASA rescue ball is 24.5 pounds. The HLR Surface Inflated Habitat shell was 332 kg. That’s 2.5 meters in diameter by 3 meters long — scaling the volume down by 22.5 gives 15 kg.
Still, it doesn’t explain why a lander has to weigh 20-30 metric tons.
Of course, Paul’s a geologist, not an engineer. Maybe he’s planning to build it out of rock. 🙂
I have two things to add to the pressure suit bonfire. First, we don’t need space suits. The astronaut could reside in a mobile pressure vessel with some waldos or other widgets to manipulate the outside world. It’d be a sort of reverse glove box. It might be a bad idea for all sorts of reasons, but it is an alternative to wearing a suit on the surface.
Second, for those brave few advocating pressure suit only missions, how is the astronaut going to eat or defecate in a suit that they need to wear for say a couple of weeks? It’d be rough, if you can’t empty the suit of fecal material because of a valve problem. Reminds me of a scene in the movie, “Christmas Vacation” involving emptying the black water tank of an RV into a public drain.
“For the weight of a space suit one could construct a cockpit sized inflatable pressure vessel that would perhaps be safer and more comfortable.”
Who boy! We have gone from a “tin foil” lander to a “beach ball.”
“But the LEM used it. Take a look, Edward:
www-dot-reformation-dot-org-slash-lunar-lander2.jpg”
The “tin foil” in question was not that gold crinkly on the descent stage. The actual LM cabin was made from aluminum shaved down to the weight of a heavy aluminum foil.
Until a really good spacesuit design comes along I suspect small shirtsleeve environment pods may be better (perhaps safer, similar weight and more convenient), whether they be on lunar rovers, space tugs, lunar landers, orbital assembly forklifts, or whatever. Consider the utility of a car verse walking, is a spacesuit really going to be better? Is the capacity to be able to walk away from a lunar crash landing going to be a requirement?
You know all the problems with spacesuits. There is also a lot to be said for being able to scratch one’s nose and go to the toilet – the little things.
Cuben fiber fabric (Spectra sail cloth) is around 2GPa with a density close to that of water, not that one would necessary use Cuben fiber. Assuming the high specific strength fibers, a reasonable factor of safety, some allowance for sealing and a redundant double wall hull – I get the approximate masses I suggested. Windows perhaps pose a weight problem, not sure how to solve that just yet (fiber reinforced clear Mylar?).
We have gone from a “tin foil” lander to a “beach ball.”
Ed started it. A spacesuit pretty much is just a collection of beach balls, and smaller ones than I was advocating. 🙂
Second, for those brave few advocating pressure suit only missions, how is the astronaut going to eat or defecate in a suit that they need to wear for say a couple of weeks?
It does not take two weeks to go from lunar orbit to the lunar surface.
How many times did Apollo astronauts stop to eat or defecate during a lunar landing?
It does not take two weeks to go from lunar orbit to the lunar surface.
So what happens on the surface? They’re still wearing those suits right? I’m not getting the full picture here.
So what happens on the surface? They’re still wearing those suits right? I’m not getting the full picture here.
They take the suits off when they enter the habitat.
Or, if it’s just a sortie, they get out, do whatever they came to do, then get back in, take off, and return to the mother ship.
Dang. It sure is a good thing the astronauts will never need to bring any cargo with them — instruments, change of clothing, lunar rovers, guinea pigs, whatever — or take anything that weighs more than a few kilos from the lunar surface back to the ship in orbit.
And those habitat bubbles, possibly made of Cuben fiber (a.k.a. Ultra High Molecular Weight Polyethylene, a.k.a. UHMWPE) fabric … how well do they hold up under raw solar ultraviolet? UHMWPE is UV-resistant here on Earth, but I wouldn’t want to bet my life on it in space. Remember, folks, we’ve supposedly been talking about reusable vehicles here.
And then how do the astronauts see through the bubble to pilot the damn thing? As Pete noted, “Windows perhaps pose a weight problem, not sure how to solve that just yet (fiber reinforced clear Mylar?).” Try transparent aluminum, it’s as likely to work …
The HLR Surface Inflated Habitat shell was 332 kg. That’s 2.5 meters in diameter by 3 meters long — scaling the volume down by 22.5 gives 15 kg.
Jeeze … Unless you make the walls thinner, you can’t make an accurate estimate of the mass of the habitat enclosure by scaling down the volume. You have to scale down the surface area, which is where the mass is.
How many times did Apollo astronauts stop to eat or defecate during a lunar landing?
The Apollo astronauts ate special low-bulk diets to minimize their fecal matter. And they didn’t “stop” — they essentially wore diapers, crapped when they had to, and kept moving.
This second half of this discussion thread seems to be infused with an “it’s as simple as that!” attitude. That’s the same sort of design philosophy that led to The Stick.
Dang. It sure is a good thing the astronauts will never need to bring any cargo with them — instruments, change of clothing, lunar rovers, guinea pigs, whatever — or take anything that weighs more than a few kilos from the lunar surface back to the ship in orbit.
Dang. I guess all the engineers who worked on Human Lunar Return were stupid. They included life support, medical kit, bio-wipes, personal equipment, power, communications, computer, mission recorder, and camera — but no guinea pigs!
Why are guinea pigs necessary on the Moon, Mike? Emergency food source? 🙂
Did the Apollo astronauts have guinea pigs?
Jeeze … Unless you make the walls thinner, you can’t make an accurate estimate of the mass of the habitat enclosure by scaling down the volume. You have to scale down the surface area, which is where the mass is.
Jeeze… Most engineers think the mass of a pressure vessel scales with the volume of contents — not the surface area.
How many times did Apollo astronauts stop to eat or defecate during a lunar landing?
The Apollo astronauts ate special low-bulk diets to minimize their fecal matter. And they didn’t “stop” — they essentially wore diapers, crapped when they had to, and kept moving.
That was during the Moon walks, not the landing.
I suggest you take a look at a jet fighter. You won’t find any toilets.
The Apollo lunar landing took about 2-1/2 hours from command module undocking to touchdown. There are movies longer than that. If an astronaut can’t go that long without a potty break, do you think he’s going to pass a NASA flight physical.
Also, it would also be a bad idea to have a pilot get up and use the toilet during takeoff or landing. The FAA doesn’t even allow passengers to do that.
I’ve put more thought into it, and think that a pressurized envelope that isn’t integral to the lander’s structure (it can be removed to allow autonomous cargo landings or other forms of transit) is the best way to go forward for a reusable craft. Hopefully, this is a little more useful than the anecdotal info cited in recent comments, though there are no guarantees.
While occasional or eventual utilization of ‘topless’ landers to rapidly take 2 or more astronauts from orbit to the surface or from one surface location to another may eventually have a niche that grows, to start with cargo is going to be the primary mass delivery to the surface. An absolutely minimalist two-way lander, while it could carry additional cargo if planned for a one-way trip, is going to keep individual pieces pretty small. I recognize that this could be made into a parallel for the heavy-lift launch vehicle discussion for exploration, but here were talking about pieces that weigh 1500kg vs 5000kg, and I think there’s a serious knee in the curve between those values for useful hardware delivery to the moon, though it’s just my opinion.
Plus, having a crew in a pressurized envelope (even though they need to have spacesuits on board in addition) takes a lot of time pressure off the whole travel-to-the-surface portion of the architecture. I saw that Apollo 17 landed 2.5 hours after separation, does anyone have estimates on travel times from Earth/Moon L1 to various landing sites? Of course, L1 ‘drop’ times can be decreased by burning additional propellants.
One thing that my analysis brought out is how tight the margins are for a single-stage reusable lunar lander without refueling (re-oxidizering?) on the surface. According to my calculations, the unrefueled case doesn’t close (tankage+engine mass > minimum dry mass) unless LOX and LH2 are used for propellants, and I didn’t take propellant loss while on the surface into account. My dry + astronaut mass of 2500kg lander (LOX/LH2 fueled, 15% tankage+engine mass) massed close to 10000kg at the beginning of an unrefueled sortie.
While this is kind of interesting, I’ve put about all the thought I want to into it for now.
You’re lucky I didn’t say gerbils … “Guinea pigs” was shorthand for “biological specimens,” of course, which might include experimental animals, or might someday include chickens or tilapia as a food source for a long-term habitat.
No, but the Apollo astronauts didn’t stay on the Moon, either. If we’re ever going to go to Mars, or the asteroids, don’t you think it might be useful to keep experimental animals in a low-G environment for a few years to see what happens to them?
“Pressure vessel”? “Scales with the volume of the contents“? We were talking about an inflatable habitat, and there’s air at one atmosphere or less inside.
That’s it. It’s clear that either you don’t know what you’re talking about or you’re a troll. Goodbye.
A very good point. A fuel depot at the Earth-Moon L-1 point is still a good 35,000 miles or so from the lunar surface.
A single stage lander makes so much more sense if you can refuel it on the surface, which I think was Spudis’ point. And if you can produce propellant on the Moon and take it back up to EML on the lander, this will (a) be far more cost effective than shipping it from Earth, and (b) let the lander carry cargo back to EML, since most of the cargo mass will be going the other way to resupply a manned or unmanned base.
Lightweight landers make sense for sortie missions, in which we’re basically doing only what the Apollo missions did. By the time we have fuel depots and reusable spacecraft (with or without crews) I think we’ll be interested in other missions as well. There may well be a place for both kinds of landers in the greater scheme of things … but I think that ultralights wouldn’t be a good fit for a lot of missions.
You’re lucky I didn’t say gerbils … “Guinea pigs” was shorthand for “biological specimens,” of course, which might include experimental animals, or might someday include chickens or tilapia as a food source for a long-term habitat.
This is silly. Are you seriously suggesting that a 20-30 ton lander is necessary to carry guinea pigs, chickens, or tilapia?
“Pressure vessel”? “Scales with the volume of the contents“? We were talking about an inflatable habitat, and there’s air at one atmosphere or less inside.
Correct. It seems you do not understand what the term means.
“Pressure vessel”? “Scales with the volume of the contents“? We were talking about an inflatable habitat, and there’s air at one atmosphere or less inside.
Assuming a given pressure, pressure vessel mass scales with volume – very basic stuff. This of course assumes that one is above minimum gauge constraints – which is rather the point of inflated structures.
Assuming a given pressure, pressure vessel mass scales with volume – very basic stuff. This of course assumes that one is above minimum gauge constraints – which is rather the point of inflated structures.
Unless I am mistaken the Human Lunar Return Surface Inflated Habitat shell wasn’t this type of pressure vessel. It would have been constructed of fabric gores between ribs that provided rigidity and support. Take a look at http://www.astronautix.com/graphics/z/zhlrhab.gif … I think with this design you are into the realm of minimum gauge constraints when you’re talking about one atmosphere or less. Do you honestly think that if the engineers wanted to scale the structure to be a bit larger or a bit smaller, they’d use thicker or thinner fabric? Or would they just use a few more or less stiffeners and gores?
You know, there probably were some pretty sound engineering reasons why this was called the “Surface Inflated Habitat,” too. Given that it’s on top of the lander, why didn’t they start out with the thing inflated and keep it that way during the entire mission? Why didn’t the HLR study propose a balloon lander like the one Edward wants?
I don’t know what Edward’s obsession is with guinea pigs, other than to be a twit. My point was that cargo of all sorts would need to be ferried down to the lunar surface; some types of cargo would need to be pressurized and might even need access to the general life-support system, so an open lander with the astronauts in spacesuits wouldn’t suffice.
If the trip down is from a fuel depot at EML — which I believe is what Paul Spudis was talking about — rather than from LLO, it’ll take quite a bit longer than the couple of hours that Edward claims. Would you want to stay inside a spacesuit for a 40,000 mile trip?
And again, if we’re talking about a reusable lander with a lifetime measured in years, how well would a fabric shell of whatever material hold up under raw solar UV? (Note: Edward seems to have ruled out covering the fabric with tinfoil!) And how well would an anflatable shell hold up to occasional physical insults during a mission? (And please don’t use “Oh, that will never happen!” as an engineering design parameter for any system that includes humans.)
Assuming a given pressure, pressure vessel mass scales with volume – very basic stuff. This of course assumes that one is above minimum gauge constraints – which is rather the point of inflated structures.
Unless I am mistaken the Human Lunar Return Surface Inflated Habitat shell wasn’t this type of pressure vessel. It would have been constructed of fabric gores between ribs that provided rigidity and support. Take a look at ***. I think with this design you are into the realm of minimum gauge constraints when you’re talking about one atmosphere or less. Do you honestly think that if the engineers wanted to scale the structure to be a bit larger or a bit smaller, they’d use thicker or thinner fabric? Or would they just use a few more or less stiffeners and gores?
[*** URL deleted to avoid moderation delay. There’s an earlier version of this comment in the queue that includes the URL.]
You know, there probably were some pretty sound engineering reasons why this was called the “Surface Inflated Habitat,” too. Given that it’s on top of the lander, why didn’t they start out with the thing inflated and keep it that way during the entire mission? Why didn’t the HLR study propose a balloon lander like the one Edward wants?
I don’t know what Edward’s obsession is with guinea pigs, other than to be a twit. My point was that cargo of all sorts would need to be ferried down to the lunar surface; some types of cargo would need to be pressurized and might even need access to the general life-support system, so an open lander with the astronauts in spacesuits wouldn’t suffice.
If the trip down is from a fuel depot at EML — which I believe is what Paul Spudis was talking about — rather than from LLO, it’ll take quite a bit longer than the couple of hours that Edward claims. Would you want to stay inside a spacesuit for a 40,000 mile trip?
And again, if we’re talking about a reusable lander with a lifetime measured in years, how well would a fabric shell of whatever material hold up under raw solar UV? (Note: Edward seems to have ruled out covering the fabric with tinfoil!) And how well would an anflatable shell hold up to occasional physical insults during a mission? (And please don’t use “Oh, that will never happen!” as an engineering design parameter for any system that includes humans.)
Flight rate is probably just as critical for lunar landers as it is for launch
vehicles or any other space transport for that mater. I could see a justification for higher mass slow traveling habitats, but a short duration lunar lander transport probably does not justify that. A two person (or cargo equivalent) lunar lander might be fairly optimal. 4-5 of them flying once a day each – it will be a long time before lunar traffic volumes justify something bigger.
If one does need to land something bigger (which probably infers a general design failure), then attach a number of lunar landers together. Multiple landers are necessary for redundancy and general development anyway, fleets of one are generally a bad idea.
I would think lunar LOX a first priority- perhaps even before people land (20:1 LOX:LH2 rocket engines are also interesting). But prior to that, use your lander to stock a propellant depot on the surface, then the lander need only be sized for a one way flight. Or are propellant depots a bad idea?
Given that it’s on top of the lander, why didn’t they start out with the thing inflated and keep it that way during the entire mission?
Because their proposal was to land the habitat first, on an unmanned lander, so it would be waiting when the astronauts got there. Inflating it in orbit would just introduce additional failure modes and increase atmospheric leakage.
If the trip down is from a fuel depot at EML — which I believe is what Paul Spudis was talking about — rather than from LLO, it’ll take quite a bit longer than the couple of hours that Edward claims. Would you want to stay inside a spacesuit for a 40,000 mile trip?
No, HLR had the the astronauts riding from the fuel depot to LLO in the X-38 command module.
There’s no law of physics that says you have to make a 40,000-mile trip in a lunar lander or in a space. Apollo didn’t do either one, did it?
Is this silly strawman season?
And again, if we’re talking about a reusable lander with a lifetime measured in years, how well would a fabric shell of whatever material hold up under raw solar UV?
If that’s a problem, you just cover the shell with regolith once it’s on the lunar surface. The habitat would not be part of the lunar lander, as you keep implying, it would simply be cargo on the lunar lander. There’s no good reason for bringing a habitat *back* from the lunar surface, at least in the early days.
Or are you completely unclear on the concept?
Pete, I think you and I — and Probably Paul, though I wouldn’t presume to speak for him — have substantial points of agreement; when we disagree, you and I seem to be talking about different things.
Flight rate is probably just as critical for lunar landers as it is for launch vehicles or any other space transport for that mater. I could see a justification for higher mass slow traveling habitats, but a short duration lunar lander transport probably does not justify that. A two person (or cargo equivalent) lunar lander might be fairly optimal. 4-5 of them flying once a day each – it will be a long time before lunar traffic volumes justify something bigger.
Some interesting implications here. This might be an overoptimistic flight rate, but that’s not a huge issue — I’d love it if we were in that situation. If large cargoes are delivered to EML by “slowboat,” you’d probably want some sophisticated robotics/teleoperation at the EML station to perform piecemeal cargo transfer as well as vehicle refueling. I think you’d want to avoid keeping humans there, due to concerns about radiation.
If one does need to land something bigger (which probably infers a general design failure), then attach a number of lunar landers together.
This might be far easier said than done. Also, some cargoes might be intrinsically large. Would it be more economical to have some reusable, refuellable “heavy-lift” landers at EML, or would it make more sense to ship large cargoes with their own single-use lander subsystems? (I don’t know the answer, it depends on specific costs.)
Multiple landers are necessary for redundancy and general development anyway, fleets of one are generally a bad idea.
Amen!
I would think lunar LOX a first priority- perhaps even before people land (20:1 LOX:LH2 rocket engines are also interesting). But prior to that, use your lander to stock a propellant depot on the surface, then the lander need only be sized for a one way flight. Or are propellant depots a bad idea?
Sounds good to me. Might the optimum mass for a “unit” of propellant to be shipped down to the lunar surface be a single filling of the reusable cargo lander’s fuel tank? In that case it might make sense just to swap tanks rather than to transfer fuel from one tto another on the surface.
Here’s what Paul Spudis wrote:
Cargo can be transported out of LEO using efficient but slow, solar electric propulsion to the Earth-Moon Lagrange point, either L1 or L2, depending upon the trade studies. Crew can follow in faster, chemical rocket transports. At least two different sized landers should be developed. A small, 1-2 mT class cryogenic lander can deliver robotic rovers, surveyors, and resource demonstration landers. After outpost establishment, it can be used in the same manner as the Russian Progress spacecraft are now used to resupply ISS. It can also deliver science payloads around the Moon after being re-fueled with lunar propellant. For human missions, a permanent, reusable lunar lander should be developed. It need not be a 50 mT behemoth; a smaller 20-30 mT lander would suffice. Its only purpose is to transport humans and high-value cargo down to the lunar outpost and back. Initially it will be fueled from the depot established at the L1 staging node; ultimately, we want to fuel it with lunar-produced propellant.
Sounds a lot like what you advocate, no? I think the notion of initially refueling both kinds of landers on the surface with fuel shipped down from EML is implied there even though he didn’t actually say it, but your mileage may vary.
Note that Edward specifically objected to this scenario, and that’s what got the thread onto a tangent. He claimed that a LEM-mass lander would be unnecessary.
If large cargoes are delivered to EML by “slowboat,” you’d probably want some sophisticated robotics/teleoperation at the EML station to perform piecemeal cargo transfer as well as vehicle refueling. I think you’d want to avoid keeping humans there, due to concerns about radiation.
Badly phrased. To avoid misunderstandings, let me re-state this:
If large cargoes are delivered to EML by “slowboat,” you’d probably want some sophisticated robotics/teleoperation at the EML station to perform piecemeal cargo transfer (i.e. breaking up one large cargo package into smaller chunks) as well as vehicle refueling. I think you’d want to avoid a long-term presence of humans at the EML station, due to concerns about cumulative effects of radiation. So although the EML fuel depot probably would include some sort of habitat, the only people who would use it would be transients or short-term repair/install personnel.