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We'll get to Mars. I'm just wondering when.
It will never happen if we just wait. We will have to make it happen.
Nobody will send humans just for exploration. The costs will be huge compared to the ones of sending robots / automatic probes etc.
I agree that sending robot probes is a cost effective means of preparing for a human mission, but robot probes will never have the skill of a human explorer. For example, geologists learned quite a lot from the anorthosite sample returned by Apollo 15. No robot probe would ever have found that sample.
One reason the public has become apathetic about space exploration is that so little has been accomplished. They will support human exploration much more if we can demonstrate results; but we have to produce results, and do so within a reasonable budget.
The idea of in-situ resource utilization is not new, but relatively little work has been done on it. The majority of work that has been done is ISPP by Robert Zubrin's company. We need a minimill, a flexible manufacturing facility that can be configured for short production runs. NASA and the US military have been working on rapid prototyping techniques to produce just a single component. Their solution is laser solidification of liquid polymer to produce plastic parts, and laser melting of metal powder to produce solid metal parts. Both produce complex 3D shapes, but the first is plastic and the second is a porous metal. A minimill uses small numerically controlled milling machines to literally mill solid parts. A minimill is applicable to short production runs rather than one-off parts. Considering the cost of transport from Earth, it should be applicable to Mars.
Yes, that cylinder is supposed to represent a slice through a pressurized greenhouse. The slice, however, is not pressurized. The Arthur C. Clark greenhouse on Devon Island is not pressurized, or even cylindrical. It's a commercial greenhouse with ribs and a slant roof, and has a plywood floor. That was an attempt to get "something" on Devon Island. The GreenHab folks have wanted to build a grey water sewage processing system to recycle human waste into nutrients for plants in the greenhouse. Environmentalists in Nunavut have prevented building such a thing on Devon Island; they aren't permitted to import the bacteria for fear of "contaminating" the ecosystem of the island. I thought those rules prevented importing any plants, but the greenhouse is built. In fact, last I heard they aren't permitted to build an outhouse; human waste must be air-lifted off the island.
I prefer the design of a pressurized greenhouse without ribs, and a non-cylindrical shape. That design was first developed by Penelope Boston, and depicted in the painting of a Mars base by Robert Murray.
International Launch Services resells Russian launch services. They list Angara here. The Angara 5 configurations appear different than in Astronautix. But lift capacity for Angara 5A is listed as 28.5t to 200km, and for Energia-M as 38t to 200km. Astronautix lists them both part of the Energia family.
You are probably thinking of the Vulkan. That could lift 170t to 200km, but was never developed beyond an engineering study.
The letter I sent to RSC Energia (RKK Energia) also asked about Energia-M. That launch vehicle lost the contract to Angara. Energia-M is no longer available; if you want a launch vehicle of that size look to Angara.
I do favour the launch vehicle Energia (LV Energia) over Shuttle-C or Magnum for the simple reason it already exists, therefor no development cost.
There is always a catch. The carbonyl process is used on Earth to extract nickel, but it only works with ferrous metals in metalic form. It won't work on oxides. All iron ores on Earth are oxides (hematite, magnesite, etc.) but iron on M-type asteroids is metal. Iron in Martian soil is also mineral oxides, so the only Martian iron that could be extracted that way would be meteorite remnants.
F.I.N.D.S. research, however, found this process can work on mineral oxides as well if you pump the pressure and temperature high enough. This is a new finding that may increase smelter efficiency on Earth. You have to love those spin-offs.
The idea to replace the Shuttle orbiter with just engines is a good one, but not new. The Shuttle-C was supposed to be just that: replace the orbiter with engines surrounded by a heatshield and parachutes to recover the engines. Magnum is similar: mount the engines on the underside of the external tank, and reshape the oxygen tank to a cylinder instead of tear-drop. That permits mounting the hab or cargo on top of the tank. Shuttle-C or Magnum would have the lift you are talking about. Shuttle-C with 3 main engines (same as the current Shuttle) or Magnum would have equivalent lift to Energia.
The reason I mentioned 88t to 200km altitude, is that's the capacity of Energia and Robert Zubrin said we could do it with 3 Energias. I just tried to look at how to accomplish that goal.
Jim Brown did some work on the carbonyl process to extract iron. See his Mars 1 web page. Derrick Davis also did some work, see Bootstrap Mission Chemistry - 101.
Some other web sites regarding space resource extraction are Colorado School of Mines, NEEP - University of Wisconsin, IEEE Spectrum Online - Mining Asteroids, and most especially F.I.N.D.S. - ferrous metal extraction from Near Earth Asteroids.
In another discission, C.COMMARMOND (FR) recommended sending a crew of 20-40 on the initial manned mission. Since that addresses mission design, I'll respond here.
Requiring a crew of 20-40 for the initial manned mission to Mars would require such a large spacecraft that no one could afford it. The point of Mars Direct is to make it affordable. The principle of "bootstrapping" means to start small, then build with each successive mission. Another point of Mars Direct I disagree with is manned missions to different locations, and only focusing on a single location after several missions. Unmanned probes (MGS, Pathfinder, Odyssey, Mars Exploration Rover, etc.) can do the scouting for us. An unmanned sample-return is the only addition needed to select a location for a permanent base. But the base must start small. Clustering habitats together is a simiple way to start a permanent base with an affordable initial manned mission.
For colonization, we will eventually need a permanent shuttle that can carry a significant number of colonists, say 100. But that will require infrastructure on Mars to refuel for the return to Earth. It will require ISPP on Mars or one of its moons, a fuel tanker, and a shuttle to carry colonists and their luggage from Mars orbit to the surface.
On-orbit fuel transfer has not been developed yet. Could freezing fuel lines block fuel transfer? Could pressure changes from the transfer cause thermal problems with the tanks? Could rapid fuel movement in zero-G of cryogenic fuel cause fluid flow problems? These issues can be worked out in Earth orbit before we go to Mars, but it hasn't been done yet.
what is your avatar supposed to represent?
That is the logo of my little company. It is the name Ardeco surrounded by an ancient Egyptian cartouche. Egyptian hieroglyphs would surround an important person's name that way. The oval is a highly stylized rope, and the vertical line on the right represents the ends of the rope. I'm not Egyptian, actually I'm Canadian and my ancestors are English, Scottish, Irish, Welsh, and Mennonite. The Mennonites started in Holland and wandered all over Europe before settling in Canada. I just thought this thing from hieroglyphics looked neat, and it would be cool to use an ancient symbol as a modern logo. The horizontal line through the letters ending with a starburst in the O was just to make it futuristic and more cool. Actually, the logo is supposed to say "aerospace" in the space beneath Ardeco, but compression to an icon made it unreadable. I like your impression that it looks like a missile.
Actually, the orginal Mars Direct plan called for 2 launches of Ares: 121.2t to 300km orbit, or 47.2t to trans-Mars trajectory. The solar-electric option of NASA DRM version 3 attempts to do the same with 3 launches of Magnum: 54.4-93.9t to 407km orbit (2 or 4 SRB's). I suggest 3 launches of Energia: 88t to 200km orbit, or 29.3t to trans-Mars trajectory.
If you want to look at high-performance systems without concern for public outcry, then I would look at NTR, not Orion. The Timberwind 75 engine had an Isp of 1,000 seconds (vacuum) and 890 seconds (sea level). As a launch vehicle, the Timberwind Titan was supposed to be able to lift 63.636t to 155km orbit. With a unit cost of $166.66 million in 1985 dollars, and a vehicle status of "development", I think the Russian Energia is a more cost effective option.
Orion Saturn V would have had a specific impulse between 1800-2500 seconds and able to launch 100t into trans-Mars trajectory in a single launch, but it was based on nuclear bombs. I don't think anyone would accept a vehicle that carries multiple nuclear bombs into space.
Actually, the United States military has breeder reactors. Those use neutrons from fission of uranium U235 to convert uranium U238 into plutonium Pu239. Of uranium dug out of the ground, 99% is U238 which is not easily fissile. Commercial reactors in Canada use non-enriched uranium (1% U235) and just let the U238 sit around. Commercial reactors in the US require 2% U235, so the uranium has to be enriched. The left-over U238 is called depleted. Since uranium is heavier than lead and about as strong as steel, but U238 has very little radioactivity, it makes excellent cannon shells. Depleted uranium shells were used in the Gulf War. Plutonium Pu239 is a richer fuel than U235, but that also makes it good for atomic bombs. Its potential for nuclear weapons is what has prevented commercial breeder reactors in the US, but the technology to enrich uranium can simply be stepped-up to make uranium fission bombs anyway.
Last I heard on TV, the US military is decommissioning nuclear bombs. This involves dismantling them, but the plutonium is left over. To ensure bombs can't be reassembled, they are destroying the plutonium. The only way to destroy an element is in a nuclear reactor, so several commercial reactors are receiving small quantities of plutonium shaped into fuel rods.
Breeder reactors use radiation to convert the mild U238 into plutonium, which can be used as fuel, but the decay products are the real danger. Uranium will eventually decay into lead, but the intermediate products decay quickly (short half-life) and release a lot of radiation. It is the "fast and hot" elements that are the problem. They may decay relatively quickly, but it can still take decades or centuries before the radiation dies down enough to be safe. In contrast, I have seen video of workers loading uranium into fuel rods with their fingers. They wear the same plastic gloves you get with household oven cleaner.
I haven't heard of anyone developing a breeder reactor that recycles the fast-and-hots.
Thanks CC.
The point is to keep cost as low as possible while retaining safety. Use of Mars resources eliminates a lot of mass that must otherwise be brought from Earth. Bringing propellant from Earth not only increases launch weight by that mass, but also extra fuel to launch it from Earth surface to Mars. If you abandon ISPP that will greatly increase mission mass, and therefore mission cost. Another thing I tried to do is avoid duplicate hardware; to create backups with alternate use of existing hardware. For example, the laboratory would normally receive life support by air ducts from the habitat. If the habitat fails the laboratory can act as a habitat by using life support on the pressurized rover. Landing the MAV first and generating propellant guarantees it is ready for the return; the only reason for a backup is if the crew lands too far to reach it. The plan I described would have a smaller and less expensive MAV than the ERV of Mars Direct, therefore duplicate hardware is cheaper.
NASA DRM version 1 included 4 launches:
- MAV with ISPP, power system, pressurized rover, unpressurized rover, 3 teleoperated science rovers, science payload
- surface habitat, power system, unpresurized rover (launched unmanned)
- return habitat with fuel to return to Earth
- second surface habitat, power system, unpressurized rover (launched with crew)
Each of these would require a launch vehicle capable of lifting 200t to LEO. That is even larger than Ares; it would require a HLLV a large as Vulkan. NASA DRM version 3 reduced mass and repackaged the missions to launch the TMI stage separately. They replaced the unmanned hab with a cargo lander, and the second pressurized rover on the crewed hab with a TransHAB derived pressurized habitat. That would permit 8 Magnum or Energia launches instead. I'm trying to keep it down to 3 or 4 Energia launches per mission, and explore the option of Earth orbit assembly using existing launch vehicles: Proton M, Angara 5, Atlas V 551 or 552, or Delta IV Large.
If RSC Energia (in Russian, RKK Energia) wants to sell at least 10 launch vehicles, we can do that with multiple manned missions.
As for eliminating the Earth reentry vehicle, the alternatives are to aerocapture into Earth orbit and use a crew taxi to bring them back to Earth, or aerocapture and aerobrake into a circularized low Earth orbit to rendezvous with ISS or Shuttle. How much mass would that require and how much time spent in Earth's radiation belts? The plan I described would use the heatshield for Mars aerocapture to land the surface hab. Earth aerocapture requires bringing another heatshield. I believe lowering orbit to ISS or Shuttle range quickly enough to avoid crew radiation exposure would mass more than a reentry vehicle. The extra heatshield for aerocapture only may mass less.
Ooh! Someone thinks my messages are out of his league! I'm just a computer programmer and wannabe aerospace engineer. Ok, so I develop real-time software for embedded systems including flight systems using the same operating system as CanadArm2, but I don't have a degree in aerospace engineering. I learned much of what I know by chatting on the original Mars Society message board and researching the web, reading science and technical journals like Science and The Journal of Propulsion and Power, reviewing my college physics text book, Zubrin's books, a text book on Orbital Dynamics, and technical papers from NASA. Any member could do the same.
How is this for a plan: Use the Mars Orbit Rendezvous with unpressurized rover included with the surface hab. Have a second MAV complete with ISPP and power arrive at Mars shortly after the crew lands. If the crew lands too far from base the second MAV can rescue them. If not, it can land at base to supply the second mission.
After a few successful missions, replace the MAV with a reusable one, and the orbital hab with a permanent shuttle. This permits an initial low-mass mission to reduce cost, and equipment can be improved after field trials for the permanent shuttle. This permits precision landing on Mars to be proven before committing astronauts to it.
You know, this discussion that the majority of the cost is R&D makes me think of a radical redesign. How much more would it cost to make the MAV reusable? That is, give it a metallic heatshield similar to the one developed for X-33. That would be durable and reusable without maintenance. Put engines and empty propellant tanks on the space habitat. The MAV would transfer propellant to the space hab on-orbit, then park in Mars orbit. Permit the MAV to keep its landing legs and retain enough propellant to land again. The space hab would keep its aerocapture heatshield. This would turn the space hab into a lot more than a habitat; it would become the permanent shuttle. In fact, if we sent the MAV with the manned mission it could act as the crew lander. The inflatable surface hab would be sent with the cargo lander. An initial MAV would be sent first with ISPP plant and power plant. When the crew arrives they have 2 MAVs at the base. If the first MAV failed they could transfer propellant to the MAV used to land, or use the ISPP plant and power plant to produce new propellant.
The second mission would rendezvous with the orbiting MAV and use that to land. The second mission wouldn't carry an MAV, surface hab, or other crew lander to Mars at all. Reusability of the parachute becomes an issue.
The permanent shuttle would use the same heatshield it used to aerocapture into Mars orbit to aerocapture into Earth orbit. It would then be met by an enlarged Soyuz space taxi, or a pair of Soyuz spacecraft to carry astronauts back to Earth. This completely eliminates taking a Crew Return Vehicle (either capsule or X-38) to Mars at all. It does require bringing a heatshield for aerocapture and ruggedizing the permanent shuttle to survive the stress.
All this would require robust equipment to survive multiple missions. Once built, the Mars base can be visited by multiple crews simply by refuelling, resupplying and transferring new crew. Additional equipment for new experiments can be sent on cargo landers. Each new delivery of cargo would enlarge the Mars base.
I think the "commit" factor will be with any Mars mission. The "Mars Orbit Rendezvous" plan I described would have a similar one. The space hab / surface hab / Crew Return Vehicle assembly could fly by Mars and return using a free return trajectory. Once captured into Mars orbit, the MAV could be remotely launched and rendezvous with the space hab to propell it back to Earth. The surface hab could make a close fly by of Mars and abort back to the space hab. Once the surface hab enters Mars atmosphere, however, it is committed; once in it is going down. At that point it better land close to the MAV.
Thinking of backup modes, I had described both rovers on the cargo lander. Perhaps we could still put the pressurized rover there, but move the unpressurized 2-man rover to the surface hab. Then if the hab lands far away from the MAV they can use the unpressurized rover to go get the pressurized one. They could carry the inflatable hab on the rovers to the MAV location. Furniture, life support, and other equipment could be removed from the lander and driven over to base. This would dismantle the surface hab lander and carry everything useful to the MAV location.
Mars Direct has an even more dire commitment. Once you launch from Earth you had better land on Mars. There is no abort option. The only backup is to send another ERV. There is a free return option, but would the hab survive Earth reentry?
The descent module of the Soyuz-TM is only sized for 3 crew in Sokol spacesuits, but it masses 3 tonnes. Would a version designed for 4 astronauts plus samples and direct entry at interplanetary velocity mass 4 tonnes?
According to NASA's X-38 Fact Sheet (it's a glossy sales brochure) the mass is 25,000 pounds (11.3 metric tonnes). It can carry 7 astronauts in clothing, but I remember another announcement that it can carry 4 astronauts in spacesuits (I believe that's an ACES suit or equivalent, not an EMU).
Remember the mass that Energia can "direct throw" into a trans-Mars trajectory is 29.3 metric tonnes, and that is C3=15 which is a Hohmann transfer orbit: 10 month trip. That mass must include navigation systems and maneuvering thrusters to adjust course to Mars, heatshield/aeroshell, parachute, and landing system. One reason I suggested keeping the CRV in Mars orbit as well as food, life support and crew accomodations, was to reduce the total mission mass. The other reason was to reduce the Mars Ascent Vehicle so it could be launched with a single Energia. If the MAV can be launched by "direct throw" instead of solar electric propulsion, then by all means do so. Mass for the Mars Direct ERV is 28.36t (Earth to Mars mass) according to the Earth Return Vehicle Definition Sheet, which does fit, but many people are skeptical. Remember, Mars Direct also stated an Ares rocket would be necessary to launch it.
To benefit from gravity assist you have to depart in the direction the planet or moon is traveling. For our Moon, travel straight from Earth toward the Moon timed to pass the Moon on a full moon. That's when the Moon has greatest velocity in the direction of Earth's orbit about the sun. Change of angle will be about 90?. Mars is inside the ecliptic so that is not a concern. Departure velocity has to be more than Earth escape velocity, not necessarily enough for a Hohmann transfer orbit. Solar electric propulsion will continue to thrust the whole trip to Mars: 6 month spiral out of Earth orbit then 1.5 years to Mars. I get the time figures from the original planned path of Deep Space One. It was supposed to pass Mars to get a gravity assist on its way to one of the asteroids. Gravity assist from the Moon may not be much, but with solar electric propulsion every bit counts. Hohmann is the lowest energy transfer orbit, and for chemical rockets that translates to lowest propellant mass. However, solar electric propulsion collects solar energy as it travels so the longer the trip the more energy available. The lowest propellant for solar electric is continuous thrust to the destination at the highest specific impulse and highest thrust level the solar panels can supply. Spacecraft engineers balance solar panel mass vs propellant mass.
All this is applicable to unmanned vehicles.
Thanks for the Aerogel link. I didn't realize it is already available in transparent form, and blanket form. The blanket could be considered for spacesuits and the hab. The transparent form for a greenhouse. I'll see if my engineer friend from Montreal is willing to work on thermal anaylsis if the greenhouse. We can see if sheet plastic with spectrally selective cloating and argon between two layers is sufficient, or whether we should consider transparent aerogel.
The X-38 is an intriguing idea. It doesn't have a regenerable life support system, and I don't think it has enough room to accomodate the inflatable habitat, powerplant for life suport, furniture, or equipment. But you could include the habitat with the cargo lander. Video of the X-38 landing shows it skids only about 3 feet, so Mars rocks should not be significantly different than dessert. The only questions are whether the heatshield is applicable to Mars, how the parachute has to be reconfigured, and whether the parachute can slow the craft enough in Mars atmosphere to land without landing rockets. The X-38 would not be large enough to aerocapture the space hab, so that would require a separate heatshield. Would separating the hab from crew lander produce lower total mission mass, or larger?
The Mars Direct plan includes landing the ERV on Mars Surface. That includes the heat shield for Earth atmospheric entry, but it is not the heat shield used to land on Mars. The ERV has to include parachutes for Earth entry, high-temperature tolerant hull, landing or splash-down equipment, as well as food and life support for the 6 month trip back to Earth. None of this has any use during surface operations on Mars. The obvious question is why you would drop all of that into the gravity well of a planet just to lift it out again? Furthermore, Mars has an atmosphere. That may make aerocapture, aerobraking and landing easier, but it adds aerodynamic drag to anything leaving Mars. The Mars Habitat may have plenty of room for astronauts on the trip to Mars and on the surface, but the ERV is cramped for the trip back.
Mars Direct made excellent use of latest technology available when it was written, about 1990, but has not been updated to include developments since. For example, the hab to be constructed of weldalite; that is aluminum-lithium alloy. Space inflatables including TransHAB have been developed since. An inflatable hab optimized for Mars surface would not require the micrometeorite shield of TransHAB because Mars has an atmosphere. The surface hab would only need protection from wind-blown dust and sand, including high-speed wind storms, and from corrosion from alkali, salty, and super-oxidized dust.
Mars mission plan - Mars orbit rendezvous
The start of the mission would launch a Mars Ascent Vehicle, similar to the ERV of Mars Direct, but with just a single ascent stage, extra large propellant tanks, and a crew cabin barely large enough to accommodate the astronauts in spacesuits and their samples. The ascent cabin would not even have life support; astronauts would live on suit support during ascent. The MAV would be launched into LEO, then spiral out from the Earth by a TMI stage that uses solar-electric propulsion. The MAV would gain gravity assist from the Moon then slowly traverse to Mars unmanned. It would enter Mars atmosphere by direct entry to avoid propellant use, land automatically and start producing propellant for the return trip. Total trip time from launch to Mars surface would be about 2 years.
At the same time, a second unmanned launch would send a cargo spacecraft. This would also be lifted into LEO and use solar-electric propulsion and direct entry. It would also take about 2 years, but it would follow the MAV closely and use an active beacon from the MAV to land within walking distance. The cargo craft would carry a pressurized rover, an unpressurized 2-man rover, garage tent, inflatable greenhouse, and inflatable laboratory together with laboratory equipment. For examination of the MAV, the cargo craft could carry an automated inspection rover roughly the size of Sojourner.
After the MAV propellant tanks are full and ready to return to Earth, then the manned mission would be launched. But the manned spacecraft would consist of two parts: a dedicated zero-G space habitat and a surface habitat. The space habitat would be a space inflatable with micrometeorite shield constructed using TransHAB technology. Life support would use a reusable CO2 sorbent and electrolysis tank like that used on ISS, but it would be augmented with a Sabatier reactor to prevent consumption of water. Water recycling would be the high efficiency system NASA already developed. TMI for the manned mission would be chemical propulsion with the two habitats docked. Trip time for men to Mars would be about 6 months. Upon reaching Mars, the spacecraft pair would aerocapture into highly elliptical, high orbit; that is, barely captured into orbit. The crew would then transfer into the surface hab. At this point the surface hab would just be a capsule large enough to accommodate the astronauts; the rest of the hab would be collapsed and stowed. The surface hab would then detach from the space hab, taking the heat shield with it. The surface hab would use the heat shield to enter the atmosphere at a trajectory so fast it is almost direct entry. The surface hab would follow the beacon of the MAV, but the cargo lander would also have a beacon as a backup.
After landing, the first order of business would be deploying the inflatable surface hab. This hab would have a recycling life support system similar to the space hab. However, it would also have a box capable of accepting chunks of Martian permafrost, melting them and filtering the water with a reverse osmosis filter. In case the recycling system breaks down, this permits the crew to replace lost water. Since the air recycling system is based on electrolysis of water, this would also replace lost oxygen. The surface hab would land with food, life support, and spacesuits for all crew members for the entire surface stay. It would not include a rover, or any laboratory facilities. Since the cargo lander would be delivered to Mars immediately following the MAV, the laboratory would be confirmed on Mars surface before the astronauts left Earth. This keeps the surface hab very small.
Surface operations would include a suitcase style PLSS on the unpressurized rover. The suits would have a 30 minute backup, and astronauts would be restricted to a 30 minute walk from the rover. This permits exploration for the full duration of the suits. In case of suit failure and rover failure, astronauts could be rescued with the other rover. The suit PLSS would use a reusable sorbent, microwave regenerable in the hab. The backup would be a closed-loop system that uses LiOH sorbent, a second oxygen tank, and an airbladder over the chest, neoprene air dam around the face, and one-way valves routing air from the helmet to the chest airbladder, from the airbladder to the sorbent, then past an oxygen regulator back to the helmet. Backup oxygen would be pressure regulated only. This permits the backup system to operate without electricity, so it works in case of battery failure. The primary sorbent cartridge would be field replaceable in Mars atmosphere, as would the battery. The primary oxygen tank would be field refillable, and the PLSS would include hoses and fittings for buddy breathing. The suitcase style PLSS would have the same duration as the backpack PLSS, include another 30 minute backup, and use the same systems as the backpack PLSS so parts are interchangeable.
Departure from Mars would involve astronauts loading all their samples onto the MAV, then getting into the cabin in their spacesuits. The MAV would ascend without dropping any stages, rendezvous with the space hab and dock. Yes, this involves Mars orbit rendezvous, and in a highly eccentric orbit at that, but orbit rendezvous and docking was developed by Gemini, and used routinely by Apollo, Skylab, Mir, and ISS. I would call it a mature technology. After docking, the assembly would thrust toward Earth. The MAV would be the Trans-Earth Injection stage using propellant from ISPP. The MAV would remain docked to the space habitat all the way to Earth. All life support including food stores for the return trip to Earth would be in the space hab. This means that if a free return to Earth is necessary, the space hab the astronauts rode to Mars would be their intended ride back to Earth, so it is already stocked for the trip.
Upon reaching Earth, the astronauts would climb into the Earth reentry capsule. This would be separate from the MAV cabin since a free return would not have the MAV docked. This provides the added advantage that the heat shield, parachute, and other landing or splashdown equipment does not have to be landed on Mars. In the case of a normal mission, it would be parked in Mars orbit until return to Earth. The MAV cabin, in fact, would not be pressurized; it would barely be an aeroshell optimized for the ascent. Docking the MAV would involve making a solid attachment for thrust, not a pressure seal. The MAV "docking hatch" would be nothing more than an access door to line-up with the outer pressure hatch of the space hab's airlock. Obviously the landing legs, ISPP plant and power plant of the MAV would be left on Mars surface.
The Earth entry capsule could be based on the descent module of the Russian Soyuz spacecraft. The "headlight and windshield" design provides the minimum exterior surface area with maximum interior volume. The Russians designed a Soyuz for direct entry from lunar return trajectory, but we would have to scale it up for 4 astronauts plus sample containers from over a year of field work. If development of such a capsule was not available, we could use the X-38; but I question whether its heat shield could withstand direct entry at interplanetary velocity. I favour the capsule because it may not be reusable, but it has lower mass than a lifting body.
As an additional backup mode, the cargo lander could include a duplicate set of food for the surface stay. The inflatable laboratory in the cargo lander could be used as backup habitat, and the pressurized rover's life support system could supply the laboratory in case the surface hab's life support failed.
This mission has another advantage: In case we don't have an HLLV available, the manned vehicle is already composed of separate components docked together. It consists of the space hab, Earth reentry capsule, surface hab, and TMI stage. Since the space hab would be based on TransHAB technology, it could be launched within a payload fairing narrow enough for Energia, or even Space Shuttle, Proton, Angara 5A, Atlas V, or Delta IV Large. In the case where Earth orbit assembly is required, the TMI stage could be launched last so long term on-orbit storage of cryogenic propellant is not required.
This may sound similar to the NASA DRM, but the primary difference is use of the MAV as the TEI stage. This enables ISPP for the return to Earth. It also eliminates storage of cryogenic propellant in Mars orbit.
I heard the concentration of water ice on the moon from the NASA web coverage for Lunar Propsector. This was data directly from the source as the data came in. When I looked up the Lunar Prospector to link to this message, it does describe concentrated pockets: 4.6% on the north pole and 3.0% on the south. I didn't see that at the time they stopped live web coverage, but it is still a low.
