Yet another Mars architecture

GW Johnson · 2014-02-27 11:00:29

Nothing is as expensive as a dead crew. NASA has proved that beyond any shadow of a doubt.

GW

RobertDyck · 2014-02-27 15:31:04

GW Johnson wrote:

Nothing is as expensive as a dead crew. NASA has proved that beyond any shadow of a doubt.
GW

Yea yea. You said that before. But the over arching engineering requirement you must always think about is cost control. The 90-day report asked for $450 Billion in 1989 dollars. If you deduct the price of ISS, then apply inflation to the remainder to today's dollars, the result is $750 Billion. There are individuals who seriously expect Congress to authorize that, and corporate executives of "Old Space" companies seriously attempt to manipulate any space effort to become that expensive, but there is no way in Hell that Congress will ever do that. They will authorize NASA's current budget. That's all. That includes all space centres that serviced the Shuttle. That includes work on SLS and Orion. Once they're finished, funds will be available for something else about the same price. That's all. That's what you have to work with.

So your options are either zero-G, or get a tether to work.

Last edited by RobertDyck (2014-02-28 01:43:22)

SpaceNut · 2014-02-27 18:26:50

GW Johnson wrote:

Spinning rigid structures work very well, actually. One sees them at Friday night football games all over the US, in season. The baton twirlers throw their batons spinning end-over-end high into the air. They are extremely stable, and easily controlled. Basic spinning dynamics says so, too.

Unfortunately the rocket is unbalanced about the center point as you are using multiple tmi stages which once the momentum of spin is removed goes off center and will cause it to tumble at a different mass center. Then there is movement of equipment, consumables, fluid such as water & waste sloshing about and crew, multiplying the effects of a shifting central axis further causing erratic moton.

Quaoar · 2014-02-28 08:45:44

RobertDyck wrote:

Yea yea. You said that before. But the over arching engineering requirement you must always think about is cost control. The 90-day report asked for $450 Billion in 1989 dollars. If you deduct the price of ISS, then apply inflation to the remainder to today's dollars, the result is $750 Billion. There are individuals who seriously expect Congress to authorize that, and corporate executives of "Old Space" companies seriously attempt to manipulate any space effort to become that expensive, but there is no way in Hell that Congress will ever do that. They will authorize NASA's current budget. That's all. That includes all space centres that serviced the Shuttle. That includes work on SLS and Orion. Once they're finished, funds will be available for something else about the same price. That's all. That's what you have to work with.
So your options are either zero-G, or get a tether to work.

If we want to cut cost, instead of cut artificial gravity, number of rovers, and habitat volume, why not to cut propellent mass using a 9 km/s exaust velocity NTR?

GW Johnson · 2014-02-28 10:06:34

What RobertDyck says about budget constraints is quite true. Unfortunately, what I said about dead crews being supremely expensive is also true.

So, the real question is this: is there a solution space where we can insure crew survival and still meet a realistic budget?

That’s actually a very good question. In my opinion, the answer is “no” if we attempt to do this the same way we have done everything earlier.

But, the answer might be “yes” if we learn from those experiences what not to do, and do this a lot differently.

Solution space: what is the budget constraint, really?

We already know that numbers in the $500B to $1T range are politically infeasible, as RobertDyck pointed out just above. I’m going to guess that $200B might be feasible, $100B even better. Just pulling numbers “out of the air” here.

If you assume the project can be run more like the way the private launch business is run, not the way NASA does things, then your direct launch expenses might be around 20% of your overall budget. That means your sub-budget for direct launch expenses might be in the $20B-$40B range.

Atlas-5, Titan-4, and Falcon-9 all fly (fully loaded) for unit prices to LEO in the $2500/pound ($5500/kg, or $5.5M/metric ton) range. Atlas-5 and Delta-4 can handle payloads in the 15-20 ton range, and Falcon-9 13 tons. There will soon be Falcon-Heavy at about $1000/pound ($2200/kg, $2.2M/metric ton), but it will be a small fraction of the total launch rate achievable for some time to come.

But you need to fly fully loaded, or the unit price is far, far higher! That sets your payload masses discretely. Which in turn suggests a modular design for your mission vehicle(s).

OK, just use the current $5.5/m.ton price. For $20-40B, you can send about 3600 to 7300 metric tons of “stuff” to LEO to assemble whatever you need to pull off this trip. In any way that seems prudent, I might add. So far I have said ABSOLUTELY NOTHING about what that mission might look like, other than modular vehicles!

OK, call it a nominal 4000 metric tons of stuff in LEO, delivered in chunks between 13 and 20 metric tons, matched to the rockets they ride, with a few 53 ton items in the mix. What can you do with that?

Can you design-in “a way out” for the crew in every mission phase?

Can you design-in a way to cope in the field with whatever equipment items prove not to work, and still meet basic mission objectives (which require proper definition by the way)?

As a bonus, can you design-in ways to accomplish more than the basics if all your stuff actually works right, and can you make any of your equipment reusable for other missions?

You all can answer those questions in any way that you want to. Everybody gets a different set of answers. As they should.

But, simply by changing the way you manage the project (from the government model to a commercial model), you get 4000 (not just dozens or a hundred) metric tons in LEO, which is a quite generous allotment of launched mass.

But, remember, it’s based on nothing but a budget-bounding calculation, as described just above.

However, we should be able to accomplish one hell of a lot with that 4000 ton mass in LEO budget, actually. A whole lot more than most of what I’ve seen proposed.

The way I looked at it used an orbit-to-orbit manned transport (crew of 6) that goes both ways with spin gravity, and is recovered in LEO for reuse; and three reusable landers pushing a propellant supply dump one-way to Mars orbit.

The reusable landers and propellant supply dump were sufficient to enable 6 surface landings and one trip to Phobos. If propellant ISRU works well at any of the surface sites visited, that propellant enables other sites to be visited sub-orbitally by the same landers. That’s a lot of “bang” for the bucks spent on the one trip to Mars.

First 6 months, 3 do science from orbit and provide rescue capability for 3 on the surface at any one time. Surface stays are in the 2 weeks to 1 month range, until the “right” site is positively identified. Then everyone goes down to that site with all the landers.

Surface habitat IS the lander. Suborbital trips are flown one vehicle at a time, so the other vehicles provide rescue capability. I based it around 3 lander vehicles, so that if one “craps out”, you still have a rescue bird and need not abort any remaining planned trips.

Second 6 months is spent building a “base” at that site in the sense of a facility that does propellant and life support ISRU. That facility is left operating unmanned when the crew goes home, to serve the next mission. I personally would include road and building construction and materials processing experiments in that facility. The idea is to learn as much as possible about “living off the land” while the crew is there, and more yet after they go home.

This mission rough-out is posted over at “exrocketman” as “Mars Mission 2013”, dated 12-13-13. My fleet in LEO is 4 ships, one manned that is under 1000 tons assembled. The 3 unmanned ships are about 1000 tons each.

In my plan, I reused EVERYTHING. Not even one empty tank was staged-off into deep space. I left the landers and empty tanks in Mars orbit for future missions to utilize. If I had stage-off the empties, my fleet would have been lighter still. Or I could have baselined even more landings in the one mission to Mars.

This is almost all docked modules with quick-disconnects, just like ISS, except that there are only about 4 distinct types of modules, not a whole plethora. The exception is the landers, which have heat shield diameters around 10-12 meters diameter. Those have to be assembled from components small enough to fit the launch rocket payload shrouds.

That in turn requires astronauts with real dexterity and mobility, unlike today. But there is a way to do this, too, and it needn’t break the bank. Far from it, actually. See also “On-Orbit Repair and Assembly Facility”, posted 2-11-14 on “exrocketman”. That article describes a free-flyer, but one of these could easily be added to the ISS, where we could test out the suits and the assembly techniques.

All of this is a house of cards that tumbles down, if you don’t radically change the management approach.

Do this the traditional NASA way, and all you can afford is 2 guys in a two-module rig that might have to forgo spin gravity, and has single-point failure modes at every single mission phase. They’ll likely die from mishap, radiation exposure, or the effects of microgravity exposure. That expensive outcome will end the possibility of any other people ever going to Mars on any tax dollars at all.

So, it’s all in the assumptions, including the ones you may not even know you are making. Gotta think WAY outside the box, if there is to be a solution space here!

GW

RobertDyck · 2014-02-28 13:24:50

So we aren't pulling figures out of thin air. NASA budget office estimated the price for Dr. Zubrin's Mars Direct. Dr. Zubrin and Dr. Baker designed Mars Direct in 1989, but NASA estimated price sometime later; I think 1990. Using the prices NASA pays, they estimated $20 billion for the first mission including research, development, and construction of infrastructure. That includes a shuttle derived launch vehicle; SLS is basically the same as Ares. That $20 billion would be spread over 8 years, so about $2.5 billion per year. Then $2 billion per mission there after, with one mission every 26 months, so about $1 billion per year. Or if NASA commits up front to 7 missions, $30 billion. That works out to "buy 6 missions, get one free."

NASA redesigned the mission, the result was semi-direct. It included 6 crew instead of 4, and brought fuel for the return from Mars orbit all the way from Earth. NASA budget guys estimated that one as $55 billion for 7 missions. When Congress saw the price jump from $30 billion to $55 billion before anything had even been built, Congress was afraid they would try to increase it to the full $450 billion. So they refused to approve anything.

This is what I'm worried about. We had a great opportunity when George H. W. Bush was president. NASA bollocks'ed it up. Martin-Marietta engineers pulled their ass out of the fire, but NASA bollocks'ed it again. George W.'s Constellation was intended to go to the Moon, with no progress at all toward Mars, but "old space" contractors still demanded the full $450 billion. Anyone who seriosly wants to go to Mars has to learn from this. Control cost or you get nothing.

Many in the Mars Society thought funds for Shuttle would be available for Mars once it was cancelled. But most of that money is for NASA centres to support the Shuttle, and Congress doesn't want to lay off those people. So all that money is still being spent. Rather than operate Shuttle, they're building SLS and Orion. No real current plans to use them, but that's what they're doing. SLS is the launch vehicle we need for Mars Direct, so let's build on that. Basically, cancel Orion and redirect those same engineers to build the Mars spacecraft, and redirect SLS engineers to the Mars vehicle once SLS is completed. That should do it. Use Dragon, DragonRider, Cygnus, and DreamChaser instead of Orion. The danger with that is SLS currently is intended to launch Orion, so the Orion managers would try to take down SLS with them. But that gives you an idea how much money is available.

This week the Inspiration Mars guys made a pitch to Congress. Rather than doing it on their own, they want hundreds of millions of dollars. Instead of using Dragon and a Bigelow hab launched by Falcon Heavy, they now want to use Orion with Cygnus launched by SLS. But rather than launching crew with the vehicle, they want "commercial crew transport" to launch the crew separately. That sounds dumb. But with Cygnus stacked on Orion, it won't have the launch escape tower. By using the features Congress wants to support (SLS and Orion) they got the Congress committee to write a letter to NASA in support of their request. So that's how it's done. Keep cost down, but spread the cost over congressional districts for those congressmen on the science committee.

Last edited by RobertDyck (2014-02-28 16:28:26)

GW Johnson · 2014-02-28 14:51:51

Inspiration Mars was supposed to be a privately-financed flyby that would shame NASA into actually doing something useful. Going for government money actually bollixes the basic concept up. Thus NASA still need not do anything useful. As long as they do nothing useful, the odds are they won't kill another entire crew. Just onesey's and twosey's on suit malfunctions and such like.

I have no real problem with the basic Inspiration Mars design concept, other than it is more likely to be a suicide mission than not. Regardless of the capsule chosen, that and a Bigelow inflatable as a habitat does not provide solar flare radiation protection. And 500 days' exposure to zero gee is an accident waiting to happen when you look at free-return-from-Mars entry gees. It was 11 gees with Apollo coming back from the moon at only 2/3 of Mars free return speed.

The design I posted could be done by somebody other than NASA. Or ESA. Or any of the government agencies. In the quarter century since the time of Bush 41, I think the trend is quite clear: NASA is unwilling to make the fundamental management changes necessary to go to Mars both safely and affordably. I have pretty much lost faith in government-run manned space programs, myself. The track record does not justify such faith.

So, I kinda doubt they'll be the ones to do it. Somebody like a Spacex might be. Tito might more likely shame Musk into doing it sooner, instead of screwing around waiting on NASA. That last is why manned Dragon is slated to fly no sooner than 3 years from now, instead of late this year or early the next.

GW

GW Johnson · 2014-03-01 09:20:39

Found a news release on MSNBC confirming what RoberytDyck and I were saying in the two previous postings just above. Tito's Inspiration Mars is now "integrated" into NASA, in that the vehicle is now Orion plus Cygnus, to be launched by SLS. Now that Tito is "part of NASA", he cannot shame NASA into doing anything about Mars.

The whole point of the mission is now completely defeated.

The date has been pushed from 2018 to 2021, because Orion and SLS won't be ready before then (if ever). Had they stayed with Dragon and either a Bigelow or a Cygnus, plus a Falcon-Heavy, they could still have flown in 2018.

From there the discussion in the news release devolved into political wrangles over what NASA's long term plan ought to be: moon, asteroids, or Mars? The wording of the article definitely suggests this is more about what will be made in whose congressional district, not about anything that might make good common sense, without actually coming right out and saying that.

THAT is why I have little faith in government-run manned space programs.

Musk, are you paying attention to all this?

Your capsule, Bigelow's and / or Cygnus modules, a long-life smaller LH2-LOX engine like the XCOR replacement for Centaur engines, LH2-LOX tank modules that have powered cryocoolers to greatly reduce boiloff, a reusable lander, a supple space suit, and a rover car with a digging bucket and a drill rig on it, are all we really need to go to Mars. Now.

Stack them up as a modular ship with a spinning baton shape for spin gravity, and reconfigure the stack between burns to maintain "radius". You need the supple suit to build the landers from component in LEO, and you need it to explore on Mars. Everything else is just dock modules and connect them.

We already have everything we need except the tank module, the lander, the supple suit, and the rover car. None of those need to be a massive development spread out over the maximum number of congressional districts, either. (If that IS done, those things will NEVER be done in time to support going anywhere.)

It need not break the bank, either. Reduce scope a bit from my "Mars Mission 2013" proposal on "exrocketman", and I'd bet this could be done for $50B, make more than one landing, and leave behind an operating ISRU facility. With a "way out" designed-in at every mission phase.

Now, where does Musk get his $50B?

GW

Last edited by GW Johnson (2014-03-01 09:24:14)

RobertDyck · 2014-03-01 09:46:43

I learned about this from the Mars Society DC email list.
Announcement of the hearing: http://www.americaspace.com/?p=54024
House Science Committee press release: http://science.house.gov/press-release/ … by-mission
Letter from House Science Committee to NASA, from that same press release: http://science.house.gov/sites/republic … 20Plan.pdf

Last edited by RobertDyck (2014-03-01 10:01:43)

RobertDyck · 2014-03-01 10:58:25

GW Johnson wrote:

where does Musk get his $50B?

Any privately run space venture must be profitable. Elon Musk founded SpaceX because he wants human exploration of space. He sold Paypal, got gobs of cash. Since he founded SpaceX and Tesla Motors. But even with that, he has limited funds. He got contracts to launch satellites with his Falcon 1 rocket. He used that money to expand SpaceX. He bid on CEV, that was the Crew Exploration Vehicle which was part of George W.'s Constellation program. Boeing won with their Orion, many others lost. But Elon didn't give up, he continued to putter with Dragon. When Obama asked for bids for commercial resupply of ISS, his Dragon was still active. He got a contract to do that. It's now profitable. He also got a contract to launch a satellite with a Falcon 9 rocket. So SpaceX is profitable. That's where the money comes from. You want to jump directly to humans to Mars? Where does the profit come from?

RobS · 2014-03-01 11:20:21

I think some of the profit comes from LEO tourism. If Musk can reuse his capsules and his stages, launch prices will continue to drop. SpaceX is already getting lots of satellite launch contracts. Bigelow wants to put a hotel in orbit; the Dragon can take people to it. I wouldn't be surprised if SpaceX couldn't generate a fair amount of profit over time supporting LEO.

There's also the moon; there are companies interested in going there, and two Falcon 9s have the launch power of a Saturn V, when you remember that the lunar landers and capsules can be lighter now than in the 1970s. That's $200 million to launch the necessary mass into LEO for a moon mission. Less, if reuse becomes possible.

Dragons and Falcons that can land on the Earth have the technology to land something on Mars. Musk developed the Falcon 9 and the Dragon for about a billion dollars. How much would it cost him to develop a Mars lander? Another billion? It'd be basically a dagon with a methane stage (which he is developing) that can land vertically. Bigelow has already said he can develop a lunar surface shelter; that would be true of Mars surface shelter as well. How much would a rover vehicle cost to develop? A suit? Much less than a billion.

The other thing that a Mars mission probably needs is a LEO fuel depot, a place stages with fuel can dock to keep them cryogenic. How much would that cost Musk or someone else to develop?

I don''t think Musk needs $50 billion. NASA said they'd have to spend what? 12 billion to develop the Falcon and Dragon? Musk did it with 1 billion. I suspect he needs another billion or two. Recently he said he could people to Mars in the mid 2020s.

Last edited by RobS (2014-03-01 11:25:52)

RobertDyck · 2014-03-01 12:02:49

Interesting. But one technical correction.

RobS wrote:

two Falcon 9s have the launch power of a Saturn V

Saturn V could lift 118 metric tonnes to 185km orbit at 28° inclination. Falcon 9 can lift 13,150kg to LEO, or 4,850kg to GTO. Falcon Heavy has 3 Falcon 9 core stages strapped together, and one Falcon 9 upper stage. It will lift 53,000kg to LEO, or 21,200kg to GTO. So two Falcon 9s do not have the lift capacity of a Saturn V.

RobS · 2014-03-01 12:07:35

That's why I said "when you remember that the lunar landers and capsules can be lighter now than in the 1970s." A Falcon Heavy can lift 53 tonnes to LEO; two of them, 106 tonnes. Apparently the 53 tonnes does not include the fairing, which is 2 tonnes. If you can fly vehicles without fairings, you have 55 tonnes times two, or 110 tonnes. That's close enough to 118 tonnes, considering our improved technology. Even with 106 tonnes, you probably have enough mass to do a moon landing if you use methane/oxygen instead of hypergolics or the new lighter materials.

RobertDyck · 2014-03-01 12:29:05

The Apollo LM had a total mass of 14,696kg. If you don't like Wikipedia, there's this. Altair is designed with a mass of 45,864kg. Oops! And for the non-Wikipedia link, this is NASA's quick facts page. To be fair, the Apollo LM was able to carry 2 crew, while Altair will carry all 4. LM was designed for only 5 pressurize/depressurize cycles, while Altair will have an airlock. But still, that's not lighter.

RobS · 2014-03-01 12:40:30

How much mass was the Altair/Orion combo in LEO? And, of course, it was designed for the Ares. If one had to design a vehicle for the Falcon Heavy, you'd start with something smaller.

RobertDyck · 2014-03-01 15:19:45

Orion was 21,250kg, although they changed their design. Now they intend to use the service module from Europe's ATV instead of developing their own.

Capsule: 8,913kg
Original service module with propellant: 12,337kg
propellant: 7,907kg
subtracting to calculate empty mass: 4,430kg
Orion 606 service module proposed would include a fibreglass shroud/fairing, with solar panels stored during launch on sides instead of under: empty mass 3,700kg + propellant capacity 8,300kg = total 12,000kg
I don't have mass for the ATV service module.

This could be done with one Falcon Heavy to launch Altair, one Delta IV Heavy to launch Orion, then another launch for the TLI stage. Not sure how big the TLI stage would be. Falcon 9 is not large enough for Orion, Falcon Heavy is too big, and Boeing is the primary contractor for Orion so they would want to use their launch vehicle. Of course the original mission plan would have Ares V (now SLS) launch Altair into LEO. The Ares V EDS (SLS Block II Earth Departure Stage) would remain attached to Altair, with enough fuel for TLI. Ares I (now Delta IV Heavy) would launch Orion with crew to rendezvous with Altair. Then the stack would burn for TLI. Ares V EDS was going to have one J-2X engine, while SLS Block II EDS will have 2 or 3 J-2X engines. According to Astroautix, the Ares V upper stage would have a loaded mass of 172,000kg, empty mass of 13,200kg. But that would be used for LEO insertion as well as TLI. This may require a separate Falcon Heavy just for the TLI stage.

RobertDyck · 2014-03-01 15:39:02

Of course I would like to send humans to Mars, and unmanned robotic explorers to the Moon. NASA is currently working on RESOLVE. A lunar rover to explore a lunar pole for subsurface volatiles. It would include a drill. Launch in 2018, would be NASA's first mission to demonstrate in-situ resource utilization (ISRU). You realize I still suspect lunar polar ice is not sufficient to justify mass of equipment necessary to harvest it. This mission is an excellant idea. Scouting for in-situ resources is definately something NASA needs to do. But lunar ice? Well, it could justify your assertion that it's there. Or my assertion that the concentration isn't enough to be worth harvesting.

Last edited by RobertDyck (2014-03-01 18:38:26)

louis · 2014-03-01 17:22:59

RobertDyck wrote:

Of course I would like to send humans to Mars, and unmanned robotic explorers to the Moon. NASA is currently working on RESOLVE. A lunar rover to explore a lunar pole for subsurface volatiles. It would include a drill. Launch in 2018, would be NASA's first mission to demonstrate in-situ resource utilization (ISRU). You realize I still suspect lunar polar ice is not sufficient to justify mass of equipment necessary to harvest it. This mission is an excellant idea. Scouting for in-situ resources is definately something NASA needs to do. But lunar ice? Well, if could justify your assertion that it's there. Or my assertion that the concentration isn't enough to be worth harvesting.

It's hardly top priority is it? The moon is four days away. A tonne of water imported from Earth will keep a young colony going for a long time with proper water recycling. The colonists can do the water prospecting.

NASA is so unambitious and unfocussed, it's so very sad, when you think back to the achievements of the sixties.

Last edited by louis (2014-03-01 20:55:27)

RobS · 2014-03-01 20:44:30

I don't agree, Louis. If the moon has water--and the evidence is that the craters at the North Pole have a fair amount, though the evidence at the South Pole is more ambiguous--then the moon is a potent source of hydrogen/oxygen propellant. Indeed, it may be a source of methane/oxygen if the coldest cold traps have carbon dioxide as well, and there is some evidence of that. If you move water to the L1 point between Earth and the moon and convert it into propellant, you have a propellant source about 3/4 of your way to Mars, in terms of delta-v. There are various commercial operators looking at this and there was a study by Michael Duke at the Colorado School of Mines about bringing water from the moon to LEO profitably. The moon may be a siren, as Zubrin fears; a distraction to a trip to Mars. But it also can be a key part of the architecture, if lunar fuel makes a mars mission easier and if passenger flights to the moon give the Martian transportation system experience and income. Those are both big ifs, though.

RobS · 2014-03-01 20:48:03

I don't know how reliable Wikipedia is, but Whipple crater at the lunar north pole supposedly ha a radar signature suggestive of ice 2 meters thick:

http://en.wikipedia.org/wiki/Whipple_(crater)

louis · 2014-03-01 20:57:27

RobS wrote:

I don't agree, Louis. If the moon has water--and the evidence is that the craters at the North Pole have a fair amount, though the evidence at the South Pole is more ambiguous--then the moon is a potent source of hydrogen/oxygen propellant. Indeed, it may be a source of methane/oxygen if the coldest cold traps have carbon dioxide as well, and there is some evidence of that. If you move water to the L1 point between Earth and the moon and convert it into propellant, you have a propellant source about 3/4 of your way to Mars, in terms of delta-v. There are various commercial operators looking at this and there was a study by Michael Duke at the Colorado School of Mines about bringing water from the moon to LEO profitably. The moon may be a siren, as Zubrin fears; a distraction to a trip to Mars. But it also can be a key part of the architecture, if lunar fuel makes a mars mission easier and if passenger flights to the moon give the Martian transportation system experience and income. Those are both big ifs, though.

I have always been a dualist - Moon and Mars together.

There is no problem with exploring water resources on the moon, it's just neither Mars nor Moon colonisation is dependent on that.

RobS · 2014-03-02 08:22:56

One issue that I'd like to discuss--even though I suppose it has been discussed before--is the best size for the interplanetary crew vehicle. Zubrin puts the crew in a metal hab that provides about 100 cubic meters per person, 400 cubic meters altogether. I think really only half of that is available because the lower level of the hab is primarily storage. I have never seen a design for the Earth Return Vehicle, but my impression from the images is that it has a two-level cabin with about 50 cubic meters per person.

I gather it is a NASA design standard that for long term voyages like a trip to Mars, the crew needs 90 cubic meters per person.

Those designs are all from the "pre-inflatable" era. Zubrin's "Falcon Heavy" design just uses a dragon capsule, which has 10 cubic meters (for 2 crew members) but adds a very light weight inflatable for the interplanetary cruise.

I am wondering whether it makes sense to merge the ERV and hab into one vehicle, essentially. The vehicle would have a small capsule for the landing and launch phases and would use inflatables in the cruise and surface phases. It would need a cargo bay so that all essentials are with the crew for the surface phase. The cargo bay itself might be convertable into habitable volume also, after the surface equipment has been moved out. One way to keep the resulting vehicle from getting too large would be to have a separate interplanetary transit stage with the propellant for trans-Earth injection and the light-weight inflatable for housing during the cruise phase. Such a configuration would require Mars orbital rendezvous instead of Mars surface rendezvous, but might save mass.

RobertDyck · 2014-03-02 08:56:01

RobS: That's what I described. Read post #30 on this thread, page 2. Direct link here.

GW Johnson · 2014-03-02 10:49:36

NASA's 90 cu.m per person criterion comes from Skylab. If you take the propellant tank volume total for an S-IVB stage and divide it by crew size 3, you get pretty close to 100 cu.m. Skylab was basically a reworked S-IVB with the internal tank shells removed. As a space station, it was very wide open inside, as the old photos so clearly indicate. Obstruct about 10% of the volume with station equipment, and you get about 90 cu.m per person.

Not only is a volume allowance per person important, its distribution and arrangement for use are also important. These are harder to put numbers to, though, as it's more about psychology. People need big wide open spaces in which to come together and do communal things. They also need some private spaces where they can be alone. And an awful lot of us need contact with nature, which suggests some sort of garden or greenhouse space might be very important. Individuals differ, too.

350-400 cu.m of unobstructed-by-equipment space for a crew of 4, properly distributed among communal, private, and garden spaces, is not something you can design into a capsule, or even a big descent vehicle. People can "camp out" for a while in more cramped spaces, but eventually (weeks? months? depends on circumstances) they must return to a more normal environment to remain sane and healthy.

Sitting in a capsule at 5-10 cu.m 8 months to Mars is a recipe to arrive insane. Insanity is a recipe for a dead crew. That plus microgravity diseases and radiation exposure is why the old vintage 1969-designs for the planned-for-the-1980's manned Mars missions probably would have killed their crews. We didn't know about stuff like that back then, but we do now.

If the required space is too large to land and live in for a year on Mars waiting to return, then leave it in orbit, land in something smaller, and erect something bigger on the surface. Or base from orbit and take turns "camping out" on the surface in your lander for shorter stays. Or both.

This is the sort of thing that ought to set the mission architecture, not budgets. The real engineering here is to design mission architectures as a function of expedition size, and determine their cost. Your budget then determines big vs small crew size (expedition size).

But, my point is that there will be no solution space between designing properly versus budget available, as long as the current NASA management model is used: let congress dictate designs by politics-of-pork-in-districts, then expensively-overbureaucratize every item to maximize the corporate welfare for favored contractors. Don't kid yourself, all the government space agencies now do it like NASA. It's not just NASA.

The NASA of 1960 did not work that way so very much, and budgets weren't screwed-down so tight, which is why Apollo actually reached the moon.

GW

RobertDyck · 2014-03-02 12:03:32

I've posted this before, but this time I'll give a larger line drawing.

The Mars Direct hab has 8 metre diameter, one floor of living space. This is used for transit to Mars, as well as on Mars. I keep saying this is how much room we need. The biggest issue with Mars Direct is the return vehicle. I've argued for an interplanetary vehicle for transit both ways. Size would be about the same as the Mars Direct hab.

To address GW Johnson's concerns: this has one stateroom per crew member. This is the private area. It isn't just a bunk like a nuclear submarine. Some proposed this before FMARS was built, so that's what is installed there. You could argue that reduces private space too much. A stateroom from the original Mars Direct is a room, floor to ceiling, with one bed and a desk. To use the desk you have to sit on the bed, no separate chair. Communal space includes a galley/lounge/library with a full sofa/chesterfield, one comfy chair, table with 4 kitchen chairs, and a bachelor suite kitchenette. There's also a bathroom with toilet, sink/vanity, and full shower. As well as a lab and exercise/health room (sick bay). That has plenty of room.

When I was in grade 9, our social studies teacher arranged the class to take a one week trip to Ottawa to see Parliament. We stayed in the University of Ottawa dorm. Beds were a little narrower than a twin bed. Not sure exactly the size, but North American twin beds are 39"x75". According to Wikipedia, a UK/Ireland single bed is 36"x75", New Zealand/Australia single is 36"x74", Norway/Sweden/Denmark/Finland single is 79"(200cm) long but width can be 31"(80cm), 35"(90cm), or 47"(120cm). Pick your favourite.

The original hab didn't have a lower floor at all. Just a landing rocket engine and fuel tanks. The rover was strapped to the underside, somewhere between the fuel tanks. Note: the Apollo LM had one floor, living space in the ascent module. The descent module had a landing rocket engine in the centre, with fuel tanks surrounding. Storage compartments were between fuel tanks, and the Apollo 15/16/17 rover was stowed in one of those compartments. All modern hab designs move the air lock to the lower deck. And Mars landers from Viking through the sky crane for Curiosity have multiple small engines on the periphery rather than one large central engine. That allows the air lock and garage we are now familiar with. But again, the lower deck will be packed full during transit from Earth. And will still have life support, fuel tanks, rocket engines, batteries to store power. Expect usable space on the lower floor (after unpacking on Mars) to be about the same size as a single car garage: 20'x10'.

In my post (#30), I described landing crew with a capsule, and all inflatable habitat. Is that a good idea? I also described the ITV as about the size of the US hab module designed for ISS. For the ITV, you could reduce crew space to a bunk like FMARS, delete the science lab, and arrange the floor plan to eliminate any corridor. But you wouldn't want to reduce it any further.

"Contact with nature"? Well, not much. The surface hab will have the inflatable greenhouse. You would want it connected to the hab so it would extend living space. But during transit from Earth, I would want pictures of Mars. During transit back to Earth, I think I would want a poster of a Caribbean island.

New Mars Forums

Announcement

#251 2014-02-27 11:00:29

Re: Yet another Mars architecture

#252 2014-02-27 15:31:04

Re: Yet another Mars architecture

#253 2014-02-27 18:26:50

Re: Yet another Mars architecture

#254 2014-02-28 08:45:44

Re: Yet another Mars architecture

#255 2014-02-28 10:06:34

Re: Yet another Mars architecture

#256 2014-02-28 13:24:50

Re: Yet another Mars architecture

#257 2014-02-28 14:51:51

Re: Yet another Mars architecture

#258 2014-03-01 09:20:39

Re: Yet another Mars architecture

#259 2014-03-01 09:46:43

Re: Yet another Mars architecture

#260 2014-03-01 10:58:25

Re: Yet another Mars architecture

#261 2014-03-01 11:20:21

Re: Yet another Mars architecture

#262 2014-03-01 12:02:49

Re: Yet another Mars architecture

#263 2014-03-01 12:07:35

Re: Yet another Mars architecture

#264 2014-03-01 12:29:05

Re: Yet another Mars architecture

#265 2014-03-01 12:40:30

Re: Yet another Mars architecture

#266 2014-03-01 15:19:45

Re: Yet another Mars architecture

#267 2014-03-01 15:39:02

Re: Yet another Mars architecture

#268 2014-03-01 17:22:59

Re: Yet another Mars architecture

#269 2014-03-01 20:44:30

Re: Yet another Mars architecture

#270 2014-03-01 20:48:03

Re: Yet another Mars architecture

#271 2014-03-01 20:57:27

Re: Yet another Mars architecture

#272 2014-03-02 08:22:56

Re: Yet another Mars architecture

#273 2014-03-02 08:56:01

Re: Yet another Mars architecture

#274 2014-03-02 10:49:36

Re: Yet another Mars architecture

#275 2014-03-02 12:03:32

Re: Yet another Mars architecture

Board footer