Whats does NASAs Manned Mars Architecture Look Like Now?

Dayton Kitchens · 2006-12-11 13:44:43

Your basic idea seems reasonable GCN.

By I'm opposed to the multiple dockings for each mission.

If just one docking out of several fails for whatever reason, your mission is screwed.

And I think we need to decide what would be an acceptable level of risk for a first mission.

I think a 10% chance of death of one or more astronauts is reasonable. It is what the Mercury astronauts were supposed to accept. Its reasonable for a mission of this scope.

And about a 25% chance of mission failure.

That is, the astronauts survive, but for whatever reasons, the majority of the first mission objectives are not met (Mars landing aborted or severely shortened, loss of all or most of the samples and scientific data, mission success in other areas but loss of large amounts of hardware expected to be reused.......)

GCNRevenger · 2006-12-11 16:39:07

There is no alternative to the large numbers of flights for a "SemiDirect" with payloads comparable with NASA's DRM-III plan. I think you are too scared of dockings, and perhaps conflating them with the lunacy of suited ISS construction. Dockings have been performed ever since the Gemini program, and a large number of both automated and manual dockings have been performed in recent years. Even Apollo with its two docking operations performed flawlessly, and all but one Russian Soyuz/Progress docked just fine, many of those without human control. Likewise the ESA ATV and NASA's unmanned Orion cargo capsule will also dock with the ISS on their own. You worry too much about that.

...but you don't worry enough about astronauts perhaps. I would think a 1-in-50 chance would be the largest I would swallow, 1-in-10 is crazy.

cIclops · 2006-12-11 16:57:32

About 1 in 50 (1.6%) is the number NASA tucked away in Chapter 8 of the ESAS. It's the Loss of Crew (LOC) risk for the complete 1.5 architecture Lunar mission. The Loss of Mission (LOM) risk is much higher at 5.9% The LOR docking holds 17% of the LOC/LOM risk.

dicktice · 2006-12-11 17:24:02

How about this, as a first Mars expedition: send a Skylab type of out-and-return vehicle to polar orbit Mars without landing anyone, but send down any of a number of clever rovers in logical order of capabilities which can be operated remotely from orbit in realtime (having dispersed relay satellites around the planet beforehand. Think of all the research that could be done quickly at nothing like the risk of landing, etc. etc. just to survive and return bedraggled from the surface. The next expedition following on in two years could be devoted to the first landing and surface survival experiments. A Mars version of Apollo 8 followed by Apollo 11 all over again?
Nah, remote control of robots from Earth isn't that bad because they are inherently so slow, you wouldn't gain that much by saving the time lag.
Look, Saturn and by extension SkyLab are long, long gone. They are not going to come back. The cost to rebuild Saturn would be about as much as going clean-sheet, which NASA doesn't have the money for. Since Ares-V is only two stages, a Skylab like ship makes less sense too.
Even if we did, Saturn was a ruinously expensive rocket. The old F-1 engines and the -six- J-2's would really add up.

You misunderstood my comparisons with past projects almost unbelievably so, since you pretend to assume repeating the past. But, taking you at your word, let me restate my suggestion more specifically with the future in mind:

Control by means of remote presence requires realtime linkup, so you gain everything by eliminating the time lag. The idea being that progressively more specialized rovers and/or tools can be landed and applied to tasks, and conceivably samples even obtained, by return-rocket for analysis under isolation lab conditions in conjunction with Earth-link consultations. The payload, in other words, would comprise a lot of remotly controllable probe hardware instead of landing, surface living quarters, and return hardware.

By "Skylab-type ofout and return vehicle" I meant the type of simple, roomy zero-gee living quarters, no spin to simulate gravity but with a perimeter track for running and leaping to keep fit, leaving the axis clear for moving from one functional zone to another. Saturn is ancient history. I'd like to see the living quarters prototype tested and proven as a self-sufficient module in LEO, and it or preferrably a new one assembled together with the propulsion modules in orbit prior to leaving on Mars Expedition 1, equivalent to Apollo 8.

The same prototype could then be used for the follow-on crew for Expedition 2, equivalent to Apollo 11. I haven't read anything quite like this for the initial manned Mars expedition, but now I can't see why this approach wouldn't be better both for the adventure of it as well as the scientific means of getting the equivalent of human "presence" on the surface without all the risks and commitment to locale that a landing would mean. In fact, aside from financing this scheme at the same time as the current Moon Colony planned for 2020 (too late for many of my generation to witness, much less to participate in) I can't think of any other objection. In fact, speaking internationally, this might be the ideal way to tackle the problem of accomplishing both interplanetary expansions simultaneously.

GCNRevenger · 2006-12-11 20:14:38

Going all the way to Mars but not landing is stupid, coming all that way but not the last few hundred kilometers? This is not like Apollo-VIII, Mars is a multi-year round trip and six months each leg. Nobody, not the public, not the politicians, and not me would understand nor tolerate this "robots only" lunacy, going all the way to Mars orbit but not to land.

Plus consider the increased hazard from radiation and extended zero-gravity exposure (running around a big ring does not give you much down force) than if you were on the ground. An emphasis should be placed on spending as little time as is practical in space, in a way its much akin to air travel in dangerous conditions, that you want to spend as little time with your landing gear off the ground as is possible. Space bad, ground good.

And its nonsense to suggest that the time lag is the #1 problem that robots have, the biggest problem slowing them down is lack of power. It makes no difference if you save 20-60min with reduced time lag if it takes hours to drill a hole or if the rover crawls along so slowly that terrain comes at you slowly. Witness the MERs, which their puny drill really does take all day to punch a hole or two, or an entire days' driving can be measured in meters and not kilometers. Plus with all the data you will be collecting, the power supply limits the communication rate you can establish. The MERs' super-spiffy color camera only uses a few of its 11 color filters, which is why the pictures look a little weird, to save on communication time. And thats just a camera! Having zero command lag won't help anything.

Plus, all the robots would have to be on the ground at the same time as the ship is in orbit... that will take a lot of choreography, unless the robots are carried aboard the ship in the first place... wait a minute, if you are going to send down a horde of mega nuclear robots from your ship, why not a lander with a crew? This idea makes no sense except to the robophiles at JPL who don't give a rip about astronauts on the ground.

Lastly, this "big simple Mars ship" is an oxymoron in triplicate, if its big then it can't be simple, and it can't be simple if it has to go all the way to Mars and back with humans aboard. This big exercise ring imparticular is a laughable idea that will never fit on any practical launch vehicle, thus necessitating orbital construction and not simple docking assembly. Even if could be built, it would then be too wide to aerobrake effectively, radically increasing the amount of fuel required. Plus, contiguous volume is very important to the psychological health of the crew, and much of this volume will sit idle and wasted.

Its an awful idea, spitting in the face of the "inspiring adventure" requirement, going all the way but stopping right at Mars's front door! It also makes little difference science wise versus remote control from Earth. Finally, the fact that you "can't see any reason why not" is one of my most hated mantras around here because it so often accompanies the default attitude that everything should work on a shoe string and always be worth it, just like Crazy Bob Zubrin or Robert Dyck.

Dayton Kitchens · 2006-12-11 21:25:16

So how many launches per "Mars Semi-Direct" mission would you suggest GCN?

You think I have an inordinate fear of dockings? Not the dockings themselves but the multiple launches just to pull off one manned mission.

Just a single failed launch could torpedo your enter mission.

Same with a more Mars Direct type mission of course, but to me, fewer launches means lower overall mission risk.

Every time Hans and Franz have to trundle to the pad to me means a heightened risk at all levels of something going wrong.

And IIRC, the Mercury astronauts were told that a 10% chance of dying was a reasonable guess. If it was good for them why not good for us on a far more daring mission?

And what exactly kind of rocket did you suggest GCN up above as a bridge between chemical rockets and nuclear thermal systems of the future?

I don't recall ever hearing of it.

GCNRevenger · 2006-12-11 22:48:29

I think that using the SemiDirect concept, keeping the ~40MT/6-crew performance characteristics, and without a clean-sheet mega launch vehicle then six launches per missions is as good as it gets.

~500MT (nuclear) or ~750MT (chemical) is really the minimum for a mission that can do this. Ares-V is the largest practical rocket to build right now for any reasonable expense, which means at least six launches. It isn't perfect, but its what we have.

I think that its reasonable to talk Ares-V having a 99%+ reliability rate, after all the EELVs have this and the Shuttle (minus the Shuttle) has this too. Since Ares will be a combination of the two (Shuttle boosters/tanks, EELV/Apollo engines) then six launches gives about a 95% chance of success. I don't think that its practical to talk about a much better chance with rockets. This would be versus ~98.5% for MarsDirect, a 5-in-100 chance versus a 2-in-100 isn't much worse.

As far "bridging chemical and NTR rockets" I don't plan on it, I don't think plain old solid-core nuclear rockets are worth fooling with, since their performance benefits for "medium delta-V" applications like Earth-Mars trips are marginal versus chemical engines. Its better just to make a bigger chemical rocket instead. The big Ares-V can lift a 130MT chemical rocket that gives you similar TMI mass as the lighter 90MT nuclear rocket called for by the old 1990's DRM-III plan, plus we would already have the chemical engine in the form of the Lunar EDS stage.

Now if we are talking high-energy nuclear (GCNR, NSWR) then that is a different matter. In that event, the ERV could serve as the crew module for the Mars cycler with the nuclear engine stage on the back, but by this point, being so far in the future, I think it makes more sense to start over from scratch.

The Mercury project was a special case, these men were truly and literally soldiers of the cold war, locked in battle with Communism for the hearts & minds of the people of this planet, and so in this a higher risk was acceptable just like a dangerous military attack. This is not the case with a Mars trip, America does not face an existential threat or serious international trouble if we can't mount the mission. Thats why its not good enough for today's astronauts.

Dayton Kitchens · 2006-12-11 22:55:09

Great post GCN!!

You pretty well answered my questions. Your point about the Mercury astronauts was rather insightfull.

Regarding Mars Semi-Direct, do you think that Zubrins concept of a 100 meter tether from the Hab to the spent upper stage and using rotation around the center of gravity to be a viable means of simulating Mars level gravity on the outbound leg of a Mars mission?

And finally, IF we had to have a larger booster sometime in the future than the Ares V, in what direction would you suggest going? Say something in the 150-200 ton payload to LEO size range?

GCNRevenger · 2006-12-12 07:31:08

Bob's tether is probably unnecessary for a 6mo trip, but it would be the easiest way to produce artificial gravity if it turns out gravity is a must. ISS astronauts seem to be okay without it though, my problem is with superlong duration exposure (>6mo).

If we did have a massive 180MT (nuclear)/220MT (chemical) class launch vehicle, then you would only need three of them per mission. But, this will definitely increase development costs for a Mars mission by several if not tens of billions of dollars. Since we will be paying the launch crew year-round whether they are flying rockets or not, and we need a minimum staff size to operate the launch complex, then six smaller rockets probably won't cost any more than three huge ones, development costs considered.

Dayton Kitchens · 2006-12-12 07:49:16

You are probably right about that. I had not considered the costs on the ground that have to be paid whether we launch one a year or six.

But I was asking about the route you would go for the large booster kind of as an intellectual exercise.

IIRC, in one of the Case For Mars studies, there was a look at some 100 meter tall superboosters. One I believe used four SRBs around an "Ares type" core.

I thought it was in that range of lift capacity.

How would development costs change for something that used four SRBs (the extended ones probably) as part of the first stage. would very heavy modification of the ground facilities be necessary?

cIclops · 2006-12-12 07:51:03

Teleoperating robots from LMO or Phobos is daft. What exactly are these robots going to do? Advanced robots won't need to be realtime teleoperated for survey work, the MERs showed how much can already be done with current technology. The small extra benefit of reducing time lag is totally outweighed by the enormous cost of sending people there. Unless the mission only lasts a few weeks there's also the problem of unproven long duration weightless flight. All of which is what GCNRevenger said more or less.

The biggest advance that can help missions to Mars would be an onorbit fuel depot. Apparently the EDS is half empty when it reaches LEO with its payload, topping it up would make a BIG difference.

Dayton: The Reference Mission of the NASA Mars Exploration Study Team - Version 3.0 June, 1998 will be the starting point for NASA's Mars Architecture, read and memorize

GCNRevenger · 2006-12-12 10:02:33

IIRC, in one of the Case For Mars studies, there was a look at some 100 meter tall superboosters. One I believe used four SRBs around an "Ares type" core.
I thought it was in that range of lift capacity.
How would development costs change for something that used four SRBs (the extended ones probably) as part of the first stage. would very heavy modification of the ground facilities be necessary?

The trouble with clustering large SRBs is that after adding more and more you get diminishing returns since the engines are not very efficient and their steel casings are pretty heavy.

I think, with serious upgrades to the engines (eg SSME instead of J-2X, regenerative RS-68), that such an "Ares-VI" could lift quite a bit more payload but the 180MT mark much less the 220MT mark are probably out of reach. Such a rocket would also require extensive modifications to the main tank to accomodate the strain from four boosters, and the launch pad would need rearranging again for the larger flame trenches and a second pair of hold-downs.

Saturn-V was already 110M tall too

PurduesUSAFguy · 2006-12-12 10:04:35

I just noticed something I hadn't cought before in the DRM:

DRM III baselines a "Magnum" Launch vehicle which has a lift capacity of 90 metric tons to LEO, With the Ares V we are talking about ~130+ metric tons. That gives that mission design alot of wiggle room and a whole lot of margin for the inevitable launch mass creep.

GCNRevenger · 2006-12-12 10:22:06

I just noticed something I hadn't cought before in the DRM:
DRM III baselines a "Magnum" Launch vehicle which has a lift capacity of 90 metric tons to LEO, With the Ares V we are talking about ~130+ metric tons. That gives that mission design alot of wiggle room and a whole lot of margin for the inevitable launch mass creep.

Yes and no:

-Most importantly, an upgraded 130MT Lunar EDS stage could replace the 90MT nuclear stage
-If the Mars vehicle is more than 90MT, it couldn't be pushed to Mars the 90MT nuclear nor 130MT chemical stage. A 130MT nuclear stage could however.
-A big 130MT nuclear stage combined with a 130MT Mars ship payload limit might make a "giant Mars kinda-direct" practical, sticking with Zubrin's two-ship approach, but using much bigger ships and mating each ship to the nuclear booster in LEO first.
-A variation I would like to consider is to launch the EDS stage with oxygen only, and put a tank of Hydrogen on the back of the Mars ship. You'd need about 20-25MT of Hydrogen for TMI, so it would just come in under the 130MT limit. This would increase TMI mass by ~5-10MT plus increase the EDS stage loiter time by a factor of 6.
-The cost of 6X Ares-V's would add up however. I wonder if there would be much cost difference with my "Ares-IV" rocket: shorter main tank, three or four RS-68s, four-segment SRBs, light-duty kick stage instead of EDS. This would about reach the 90MT mark and might cost considerably less.
-In the longer run, maybe the USAF's hybrid booster first stage could be used in place of the SRBs on the "Ares-IV" with a reduced count of upgraded RS-68s.

cIclops · 2006-12-12 11:26:38

-A variation I would like to consider is to launch the EDS stage with oxygen only, and put a tank of Hydrogen on the back of the Mars ship. You'd need about 20-25MT of Hydrogen for TMI, so it would just come in under the 130MT limit. This would increase TMI mass by ~5-10MT plus increase the EDS stage loiter time by a factor of 6.

EDS is needed to lift itself and the payload to LEO so it can't be modified to contain only LO2. The TLI mass is about 65 mT, and TMI is about 45 mT. The mass to TMI would be increased further if a third stage was lifted first. This could weigh 130 mT. A second Ares V/EDS then lifts the heavy payload using all its fuel to reach LEO and discards its EDS. The payload then docks on top of the third stage/EDS stack.

(edit: changed TMI mass)

GCNRevenger · 2006-12-12 12:26:47

Well, then make the Hydrogen tank on the "mostly oxygen" EDS stage smaller (just enough to get to orbit) and live with its dead weight, or as you suggest just launch a second EDS stage on top of the first. The point is to use the excess ~30MT of payload that Ares-V affords over Magnum to increase TMI mass as well as leaving only the oxygen needed aboard the EDS, increasing its LEO loiter time.

Another alternative would be to forgo "fuel sharing" between the two vehicles for TMI, and instead attach a beefed up Centaur (or something) upper stage to the Mars vehicle as a 3rd/4th stage to take advantage of the extra payload. In this case you would trade complexity of the plumbing and somewhat increased performance for another staging event and the weight of a another engine.

However this engine would be more efficient than the J-2X most likely, as later models of Centaur have reached quite high specific impulse, and then there is the added benefit of another staging. Unfortunately it would mean losing the EDS extended loiter time and add another engine to the "must not fail" list. It might however add an additional abort option in the event the EDS stage fails then the Centaur plus landing fuel might be enough for a direct abort to Earth.

To review:

Option 1: Nuclear-Chemical trade, modified 130MT EDS, lofted on top of a regular EDS on Ares-V, replaces the 90MT nuclear stage called for in DRM-III. Mars ship launched on less powerful (and less expensive?) rocket.
- ~Advantage: simple, minimum number of engines, no fuel transfer, minimum tank mass. Possibly lower overall launch cost with Mars ship launched on lighter rocket.
  ~Disadvantage: smallest TMI mass, may suffer from poor J-2X performance, short loiter time
Option 2: Reduce EDS Hydrogen but increase Oxygen carriage, with the Hydrogen for TMI later supplied by a separate tank on the Mars ship also lofted by Ares-V. Otherwise identical to Lunar TLI, with the EDS stage doubling as a TMI stage.
- ~Advantage: increased TMI mass, same number of engines and burn as 1, simplest way to take advantage of excess payload. Increases EDS loiter time from 1mo to 6mo. Only two total EDS stages instead of three.
  ~Disadvantage: requires complex fuel transfer between vehicles for TMI, increased Hydrogen tank dead weight.
Option 3: Combination of 1 & 2, a second modified EDS stage is launched atop the first as in 1, but it carries only Oxygen. Hydrogen would be supplied by the Mars ship as in 2
- ~Advantage: Slightly simpler than 2, less Hydrogen tank dead weight
  ~Disadvantage: requires three total EDS stages instead of two as in 2
Option 4: Same as 1, except Mars ship would be launched by Ares-V with a smaller Centaur booster rocket on the back, used for TMI in addition to the modified EDS stage.
- ~Advantage: no fuel transfer like 2 & 3, somewhat higher average specific impulse, possibly enabled direct abort to Earth in the event of EDS failure. Slightly increased payload due to additional staging too. Centaur rockets are relatively cheap. Highest total TMI mass.
  ~Disadvantage: increases number of engines and burns necessary, no enhanced loiter time like 2 & 3

Dayton Kitchens · 2006-12-12 13:10:07

I tried to post this earlier.

How much would it reduce the mission mass to reduce the crew size from 6 astronauts to 3?

Dayton Kitchens · 2006-12-12 13:11:48

By the way, isn't zero G transfer of liguid hydrogen an operation loaded with complications?

cIclops · 2006-12-12 13:25:53

Option 4 using an optimized Centuar like third stage lifted by a standard Ares V/EDS sounds good. Keep it simple. A standard Centaur weighs about 20 mT and its RL-10 ISP is 433, whereas the J-2X is 448 secs. There should be some sweet spot between the third stage mass and final TMI mass. My guess is TMI mass well over 100 mT should be possible.

Remember that one Ares V/EDS can put about 84 mT into TMI so this only makes sense if all this mass is needed in one package arriving at Mars. The two Ares Vs will cost about $2 billion, so it ought to be a very good reason indeed.

cIclops · 2006-12-12 13:27:30

By the way, isn't zero G transfer of liguid hydrogen an operation loaded with complications?

AFAIK it's unproven, but potentially extremely helpful.

Dayton Kitchens · 2006-12-12 13:31:26

By the way, isn't zero G transfer of liguid hydrogen an operation loaded with complications?
AFAIK it's unproven, but potentially extremely helpful.

I prefer to not gamble on unproven methods.

Lets keep things as simple as possible

GCNRevenger · 2006-12-12 13:37:26

I tried to post this earlier.
How much would it reduce the mission mass to reduce the crew size from 6 astronauts to 3?

Lets not go there. Even a four-man crew is awfully small to bother with given all this trouble and expense to get to Mars. Six with the option for eight substituting the laboratory space, thats the ticket.

Dayton Kitchens · 2006-12-12 13:44:46

I tried to post this earlier.
How much would it reduce the mission mass to reduce the crew size from 6 astronauts to 3?
Lets not go there. Even a four-man crew is awfully small to bother with given all this trouble and expense to get to Mars. Six with the option for eight substituting the laboratory space, thats the ticket.

But would it be doable?

You put one professional geologist and an amateur biologist on the surface of Mars for a year and I bet they could do one heck of alot of work.

The samples and first hand measurements alone they could make would be priceless.

GCNRevenger · 2006-12-12 13:48:05

Option 4 using an optimized Centuar like third stage lifted by a standard Ares V/EDS sounds good. Keep it simple. A standard Centaur weighs about 20 mT and its RL-10 ISP is 433, whereas the J-2X is 448 secs. There should be some sweet spot between the third stage mass and final TMI mass. My guess is TMI mass well over 100 mT should be possible.
Remember that one Ares V/EDS can put about 84 mT into TMI so this only makes sense if all this mass is needed in one package arriving at Mars. The two Ares Vs will cost about $2 billion, so it ought to be a very good reason indeed.

I am kind of partial to Option 2, but I would be happy with any of 2-4. Option 1 is kind of a cop-out since it probably wouldn't save much money versus these other options.

Actually modern versions of RL-10 have Isp's in the range of 450-460sec, with proposed advanced models hitting 470sec. I didn't know that NASA was going to aim for 448sec on J-2X though, which is quite good. Modifying Centaur with a wider, shorter fuel tank and the necessary hardware should yield about ~10MT extra TMI mass or ~5MT surface mass. Theres' your heavy pressurized rover.

GCNRevenger · 2006-12-12 13:54:21

But would it be doable?
You put one professional geologist and an amateur biologist on the surface of Mars for a year and I bet they could do one heck of alot of work.
The samples and first hand measurements alone they could make would be priceless.

I'm not going there. We either go to Mars with a crew big enough, or we shouldn't go at all. Six is the best compromise between rockets of practical size plus how much more you can accomplish with a dozen boots on the ground.

Three men to Mars is too much like repeating Apollo, and repeating Apollo on Mars would be MUCH WORSE than never going in the first place!

We go big enough to get stuff done, or we don't go.

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#26 2006-12-11 13:44:43

Re: Whats does NASAs Manned Mars Architecture Look Like Now?

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Re: Whats does NASAs Manned Mars Architecture Look Like Now?

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