Smallest Human Ascent or Descent Lander for Mars Or Earth

RobertDyck · 2015-04-07 20:44:32

Well, I have suggested a rover like Mars Direct. Robert Zubrin included a rover with enough fuel for 1,000km one way in case the habitat lands that far from the Earth Return Vehicle. If they land correctly, then the rover can be used to explore. Furthermore, the nuclear reactor will have fuel for years, so could continue to produce extra propellant. That propellant could be used for the rover. That's a lot of exploring. And my plan included a reusable ITV, initially with expendable TMI stage, and expendable MAV that would act as TEI stage. But eventually that stage would be replaced with a reusable one. That would require refilling propellant in Mars orbit, either from Mars or one of its moons. And a way to ferry crew from orbit to surface and back. A reusable Mars shuttle would look like DC-XA; a land-on-your-tail rocket. Now SpaceX is building reusble rockets, so the Mars shuttle would be one of theirs. That shuttle would allow exploring the entire surface of Mars. Not from orbit, but a surface base.

We're all struggling with ways to make a humans to Mars effort effective, not "flags and footprints", but at the same time affordable. Congress has already said "no" to the 90-Day report, and it's price tag. "Old Space" corporate executives keep trying to manipulate plans to be the 90-Day report, and it's full price tag. The rest of us keep trying to find ways to reduce cost, but at the same time ensure it isn't flags-and-footprints.

kbd512 · 2015-04-07 23:31:29

RobertDyck wrote:

Well, I have suggested a rover like Mars Direct. Robert Zubrin included a rover with enough fuel for 1,000km one way in case the habitat lands that far from the Earth Return Vehicle. If they land correctly, then the rover can be used to explore. Furthermore, the nuclear reactor will have fuel for years, so could continue to produce extra propellant. That propellant could be used for the rover. That's a lot of exploring. And my plan included a reusable ITV, initially with expendable TMI stage, and expendable MAV that would act as TEI stage. But eventually that stage would be replaced with a reusable one. That would require refilling propellant in Mars orbit, either from Mars or one of its moons. And a way to ferry crew from orbit to surface and back. A reusable Mars shuttle would look like DC-XA; a land-on-your-tail rocket. Now SpaceX is building reusble rockets, so the Mars shuttle would be one of theirs. That shuttle would allow exploring the entire surface of Mars. Not from orbit, but a surface base.

What type of internal combustion engine would we use on Mars? We're likely to subject it to some fairly extreme thermal cycling and it would require a substantial radiator. If you're tied to a gas station, you have to continuously go back for refills. The internal combustion engines are preferable to electric motors here on Earth because there's a global infrastructure, built over many decades, to support their use and repair. On Mars? Not so much. It's doable, but at what cost?

This is what I had in mind for Mars:

http://www.ointres.se/2010-11-30_sep-band1.JPG

Using all-electric versions of these vehicles figures heavily into my proposal for the use of micro capsules. The MTVL's are tele-robotically operated by crew members remaining with the MTV prior to EDL of the first and third astronauts. The second and fourth astronauts are picked up by the first and third crew members operating the MTVL's after they've reached the surface.

If supplies for only half the surface stay are packed into each vehicle, rather than for the entire duration, then the weight of each vehicle drops to less than 15t. Deployment of three such vehicles to the surface provides a spare, substantially lower per-vehicle mass resulting in better range, and an intermediate cargo mass for initial ADEPT use on Mars. This would do away with the immediate requirement to land a substantial 40t to 80t habitat module.

DC-XA on Mars? That thing had enough problems on Earth. Why would it fare better on Mars? Would the payload be nearer to the base of the rocket? How are you planning to get the payload to the surface after you land?

RobertDyck wrote:

We're all struggling with ways to make a humans to Mars effort effective, not "flags and footprints", but at the same time affordable. Congress has already said "no" to the 90-Day report, and it's price tag. "Old Space" corporate executives keep trying to manipulate plans to be the 90-Day report, and it's full price tag. The rest of us keep trying to find ways to reduce cost, but at the same time ensure it isn't flags-and-footprints.

I've given quite a bit of thought to things that don't involve substantial risk to the entire crew. I think having all crew members in the same surface habitat or rover or descent/ascent vehicle is a substantial mission risk, which is why I split the four person crew into pairs for surface operations and land/launch them individually.

With the same line of reasoning, if at all possible I only want to use two of the five major EDL technologies (ADEPT, HIAD, parachutes, airbags, retro-propulsion) for any particular descent vehicle whether it's landing humans or cargo. Given state of development limitations, I went with HIAD + parachutes for humans and ADEPT + retro-propulsion for cargo.

RobertDyck · 2015-04-08 13:08:15

If one single astronaut dies, your mission is complete failure. So splitting up astronauts just increases chance of failure.

SpaceNut · 2015-04-08 17:23:15

A death of an astronaut does not deem a mission failure as there are more parts to a mission than just safe return of a crew man as it is an excepted risk that all that journey into space take....

Whether it happens at launch to orbit or coming back down and even when on another planets surface death is part of the risk. No one wants a dead crew member for any reason but life is just that way even here on Earth.

A mission failure is dependant on all other details of what we would expect a crew to do while on a mission which is from start to stop and not just while we are on the Mars surface.

So what is the science that would be cause to say a mission is also a failure if not completed?

Please open a new topic if anyone thinks there is a enough thoughts to warrant it to be discussed.....

kbd512 · 2015-04-08 18:42:08

RobertDyck wrote:

If one single astronaut dies, your mission is complete failure. So splitting up astronauts just increases chance of failure.

Rob, There's something fundamentally flawed about all-or-nothing thinking. We killed 14 people with the Space Shuttle and kept flying them. All space flight incurs substantial risk and all of our astronauts are well aware of that. If they were overly concerned with the possibilities, they'd seek life elsewhere. That said, whether you kill one or all of the crew with a single event is a question of design.

We're not going to Mars for the purpose of returning astronauts alive, we're going there to explore. Returning them alive is a mission objective, but not the most important one. If the crew's well-being was first priority, we'd never send them to Mars in the first place. Results are never guaranteed, but one thing is entirely certain. If you kill the entire crew in one lander/rover/habitat, then there is no further manned space exploration for that particular mission.

Instead of being so arrogant as to think it's possible to account for all potential failures with "better" hardware, perhaps we could try sending "more" hardware of simpler, task-oriented design. No matter how well engineered a particular vehicle is, if humans are involved then failures are inevitable.

If it's too technologically challenging to land a manned trash can using an inflatable aeroshell and parachute, perhaps we should resign ourselves to looping around Earth. The vehicle you (Dr. Zubrin, actually) proposed is many times heavier, far more complicated, and substantially more expensive than my proposal. It's designed for the crew to live in during return to Earth, so it has to be.

Apart from landing in a habitat module or a fully fueled ascent vehicle, if you're so far off course that a rover can't reach you, then what follows should be obvious. We could land the humans with the cargo if we wanted to. That doesn't make much sense here on Earth and I doubt it makes much sense on Mars, either. The primary reasons not to make human and cargo EDL solutions the same are peak deceleration force and margins required for man-rated systems.

I'll ask one last time for a minimal mass, multi-person human EDL solution proposal that doesn't weigh substantially more than what I've proposed. NASA says it wants to save substantial weight for future interplanetary missions, as much as 40%. Unfortunately, there are no miracle materials industry can provide to the agency that will make up for poor engineering. If you want to save substantial weight, then you make calculated technology selections designed to reduce the mass of the mission payloads. My solution is paring lander weight down to what is essential for a human to land on Mars and survive for a brief period of time outside of a habitat or rover. It is not "best" from a survivability standpoint. My presumption is that our highly trained and experienced human can pilot the micro capsule to within driving range of one of three rovers prepositioned at the periphery of the landing area.

kbd512 · 2015-04-08 20:04:59

Here's my reasoning behind using micro capsules, ~15t payloads, and MTVL derivatives for initial mobile Mars exploration missions:

* mobility provided by a MTVL derivative is required for both surface exploration and retrieval of the astronauts from their micro capsules

* MTVL is not a golf cart, it's a combat vehicle that's seen decades of service in conflicts around the world

* combat loaded MTVL's actually weigh less than 15t with men, weapons, ammunition, fuel, etc (we're replacing all that with supplies accommodations, and CL-ECLSS for two crew members, four for short duration contingency purposes like a stranded MTVL)

* the aluminum armor is an alloy specifically designed for pressure vessels and space applications

* the hull is anywhere from 12mm to 38mm thick, in other words not a paper thin pressure vessel

* several manufacturers make NBC kits for the M113 that use PE and other materials technologies to attenuate radiation

* a variety of electric and hybrid drive systems have already been tested on this platform

* segmented steel and synthetic band tracks have been developed for the M113 and tested in arctic conditions (obviously not equivalent to Mars temps, but as much as we're capable of doing here on Earth outside of an environmentally controlled facility- more testing required)

* if obstructions for unneeded turrets and hatches are removed from the top of the vehicle, a large flat surface suitable for mounting large solar panels on is available

* the M113 is late 1950's technology, so it's not as if an entirely new vehicle has to be developed from scratch

* tele-robotically operated M113's have already seen military use

* M113 and MTVL are relatively small and fit well within the payload shroud of a F9H, so ADEPT could easily be wrapped around the rover

* combined all-up weight with EDL-related hardware should be well within the capability of two F9H flights, even if we have to use chemical propulsion for TMI, and within the capability of one F9H flight if we use a SEP tug for TMI

* gives NASA an opportunity to test an intermediately sized SEP tug to transfer the payload to Mars and to test ADEPT at Mars, arguably far more useful for future manned Mars exploration than playing with space rocks

* no SLS flights are required, so yearly flight capability is preserved for flagship missions

* Multiple micro capsule EDL tests are possible per F9H flight using chemical or SEP for TMI; using SEP permits the capsules to be de-orbited from a variety of orbital inclinations, at different times of the day, and during different seasons to demonstrate performance characteristics in the wildly varying atmospheric conditions at Mars.

RobertDyck · 2015-04-09 02:08:48

Many people already ridicule the 1950s idea of teleoperating robotic vehicles from a manned vehicle in Mars orbit. The question is if you are going to have robots operate remotely, then why put operators in Mars orbit? Why put operators in space at all? Instead put operators on the surface of Earth. This line of reasoning leads to MER, MSL, and all the other robotic explorers of JPL. So your argument to use teleoperated robotic equipment is actually an argument to not send humans to Mars at all. That may not be what you intend, but that's how it works.

Several scientists have pointed out you need field geologists with the mark 1 eyeball. That means boots on the ground. Dr. Carol Stoker did one experiment with graduate students. She set up robotic explorers somewhere on Earth, and asked them to find evidence of life. The students operated the equipment remotely, and weren't told where the robots were. One student did find one fossil, but not of the others found any. The robots were in Dinosaur National Park, the richest fossil bed in the world. The point is you need boots on the ground. Robotic explorers aren't good enough.

You asked about reducing mass. Robert Zubrin and his partner David Baker came up with Mars Direct in late 1989 and 1990. That initial plan had a single story Mars habitat, with stuff strapped to the under side: landing rockets, fuel tanks, life support equipment, batteries to store power from solar panels. And the pressurized rover was slung under the hab, with a winch to lower it to the ground on Mars. That was later changed to a second floor. I still point out most of the second floor will be equipment, but experience on ISS has shown that astronauts need access to life support equipment for repairs.

When I tried to reduce mass to fit on Energia, one idea was an open rover that would look much like the Apollo lunar rover. But with 4 seats instead of 2. Astronauts would ride in spacesuits, and carry a pup tent they could erect to sleep or service their spacesuit. Or if they need to "go to the bathroom". They would only have a plastic bag to go into, like Apollo. If you want an actual bathroom, stay in the hab. Life support for the tent would be the PLSS backpack from the suit. A power cord would supply power from the rover to the suit PLSS for extended range, and the rover would carry extra oxygen bottles. The hab itself would be an inflatable, similar to Transhab. But it wouldn't need a micrometeor shield on Mars, because Mars surface doesn't have micometeoroids. It would require a scuff later to protect the hab against astronauts rubbing against it, and against Mars dust/sand storms. So that means an outer later of Tenara achitectural fabric, or the same Ortho-fabric used for white EMU spacesuits and ISS modules. The lander would have this inflatable hab and all internal equipment and supplies, as well as a tiny capsule for astronauts. The capsule for landing would be just a seat for each astronaut, that's all. The ITV would use an umbrella style heat shield for aerocapture into Mars orbit. The heat shield would have to stay attached, because it would be used for aerocapture into Earth orbit for return. This heat shield only has to be sufficiently robust for aerocapture; it doesn't need to withstand direct entry. The lander would be attached during aerocapture. Then the lander would separate, using another folded heat shield. This one has to protect from atmospheric entry, but only from Mars orbit, not direct entry. The entry heat shield would be single-use, discarded.

Robert Zubrin and David Baker's Mars direct included a Mars hab with hard walls. They used Weldalite, which is aluminum-lithium alloy. That's the lightest weight alloy available in 1989. David Baker designed the folding heat shield and landing rockets. The habitat would be separated from the heat shield by the landing legs, so there's some separation to protect the hab from heat. Apparently that is enough to allow use of aluminum alloy habitat. If that's good enough for an all metal hab, then the crew capsule for a lander with an inflatable habitat should be aluminum alloy as well. The umbrella style heat shield keeps hot gasses during atmospheric entry well away from the habitat, so high temperature alloy outer hull is not required. Only works on Mars, but that means we can use light-weight alloys for the Mars lander.

Again, figures from the ADEPT team show the lowest mass EDL used 3 technologies: heat shield, parachute, and landing rockets that start at subsonic flight. Using their figures, do the same for the Mars lander.

But, I'm trying to reduce cost by reducing mass. You want to send a tank to Mars?

Last edited by RobertDyck (2015-04-09 15:10:30)

kbd512 · 2015-04-09 08:26:21

RobertDyck wrote:

Many people already ridicule the 1950s idea of teleoperating robotic vehicles from a manned vehicle in Mars orbit. The question is if you are going to have robots operate remotely, then why put operators in Mars orbit? Why put operators in space at all? Instead put operators on the surface of Earth. This line of reasoning leads to MER, MSL, and all the other robotic explorers of JPL. So your argument to use teleoperated robotic equipment is actually an argument to not send humans to Mars at all. That may not be what you intend, but that's how it works.

Rob,

The tele-operated rovers are mobile habitats that the remaining crew in LMO in the MTV can use to direct a rover to the first and third astronauts (once these two land, they will drive the rovers to the landing sites for the second and fourth). Three rovers, two astronauts per rover, one complete spare rover, all rovers ring the landing area. First two astronauts verify that the rovers are fully functional. If there's a problem that inhibits a surface stay, all astronauts return to the MTV in LMO using microcapsules atop fully fueled ascent vehicles.

Regarding tele-operation, instead of having to rely only on homing beacons to guide the rovers to the astronauts after they land, sensors on satellites in orbit can track the position of the micro capsules and rover in real time, relay that information to the MTV crew, and the MTV crew can then drive the rover to each astronaut's landing coordinates. A computer guidance program that homes in on the astronaut's beacon can serve as a backup.

RobertDyck wrote:

Several scientists have pointed out you need field geologists with the mark 1 eyeball. That means boots on the ground. Dr. Carol Stoker did one experiment with graduate students. She set up robotic explorers somewhere on Earth, and asked them to find evidence of life. The students operated the equipment remotely, and weren't told where the robots were. One student did find one fossil, but not of the others found any. The robots were in Dinosaur National Park, the richest fossil bed in the world. The point is you need boots on the ground. Robotic explorers aren't good enough.

No disagreement here. The MTVL's are repurposed armored personnel carriers designed for human habitation and convoy-style mobile surface exploration on Mars. The tele-robotic operation is a design feature to assist our human explorers and for testing purposes.

RobertDyck wrote:

You asked about reducing mass. Robert Zubrin and his partner David Baker came up with Mars Direct in late 1989 and 1990. That initial plan had a single story Mars habitat, with stuff strapped to the under side: landing rockets, fuel tanks, life support equipment, batteries to store power from solar panels. And the pressurized rover was slung under the hab, with a winch to lower it to the ground on Mars. That was later changed to a send floor. I still point out most of the second floor will be equipment, but experience on ISS has shown that astronauts need access to life support equipment for repairs.

I want to do away with the whole notion of a pressurized surface habitation module being a house.

RobertDyck wrote:

When I tried to reduce mass to fit on Energia, one idea was an open rover that would look much like the Apollo lunar rover. But with 4 seats instead of 2. Astronauts would ride in spacesuits, and carry a pup tent they could erect to sleep or service their spacesuit. Or if they need to "go to the bathroom". They would only have a plastic bag to go into, like Apollo. If you want an actual bathroom, stay in the hab. Life support for the tent would be the PLSS backpack from the suit. A power cord would supply power from the rover to the suit PLSS for extended range, and the rover would carry extra oxygen bottles. The hab itself would be an inflatable, similar to Transhab. But it wouldn't need a micrometeor shield on Mars, because Mars surface doesn't have micometeoroids. It would require a scuff later to protect the hab against astronauts rubbing against it, and against Mars dust/sand storms. So that means an outer later of Tenara achitectural fabric, or the same Ortho-fabric used for white EMU spacesuits and ISS modules. The lander would have this inflatable hab and all internal equipment and supplies, as well as a tiny capsule for astronauts. The capsule for landing would be just a seat for each astronaut, that's all. The ITV would use an umbrella style heat shield for aerocapture into Mars orbit. The heat shield would have to stay attached, because it would be used for aerocapture into Earth orbit for return. This heat shield only has to be sufficiently robust for aerocapture; it doesn't need to withstand direct entry. The lander would be attached during aerocapture. Then the lander would separate, using another folded heat shield. This one has to protect from atmospheric entry, but only from Mars orbit, not direct entry. The entry heat shield would be single-use, discarded.

I guess I've described an updated version of your mission design, less capsule capacity, with pressurized rovers so the astronauts don't have to live in their space suits. I intended for our explorers to wear mechanical counter-pressure suits, thermally protective clothing, and use the "hookah hoses" that GW illustrated in the article about the mechanical counter-pressure suits on his website for making repairs to the MTVL's.

I designed my missions to primarily use F9H. It might make sense to launch the MTV aboard SLS to avoid some orbital assembly operations or it might not.

RobertDyck wrote:

Robert Zubrin and David Baker's Mars direct included a Mars hab with hard walls. They used Weldalite, which is aluminum-lithium alloy. That's the lightest weight alloy available in 1989. David Baker designed the folding heat shield and landing rockets. The habitat would be separated from the heat shield by the landing legs, so there's some separation to protect the hab from heat. Apparently that is enough to allow use of aluminum alloy habitat. If that's good enough for an all metal hab, then the crew capsule for a lander with an inflatable habitat should be aluminum alloy as well. The umbrella style heat shield keeps hot gasses during atmospheric entry well away from the habitat, so high temperature alloy outer hull is not required. Only works on Mars, but that means we can use light-weight alloys for the Mars lander.

Ok.

RobertDyck wrote:

Again, figures from the ADEPT team show the lowest mass EDL used 3 technologies: heat shield, parachute, and landing rockets that start at subsonic flight. Using their figures, do the same for the Mars lander.

I'll refer you to my previous comments about simplicity. Pick two of the five technologies for EDL, one for reentry and one for landing. Theoretically, using ADEPT + parachute + retrorockets lowers the mass devoted to EDL. We'd need to test that theory against reality.

RobertDyck wrote:

But, I'm trying to reduce cost by reducing mass. You want to send a tank to Mars?

Me, too, Rob. I also want to send very light, durable, and mobile personnel carriers to Mars for greater exploration returns. Want durable rovers? The M113/MTVL is what a durable rover looks like. Tracks give greater off-road mobility, better traction, and lower surface pressure here on Earth and the same applies to Mars. The loaded weight of the MTVL equipped for surface exploration, assuming only half the supplies for the entire surface stay were kept with each rover, would work out to about ~15t. It just so happens that the rest of the numbers for EDL mass and an intermediately sized SEP tug that NASA wants to use for ARM (that could also push this payload to Mars) work out to about what a single F9H can lift.

With four F9H launches, you can have the three MTVL's required for mobile surface exploration and a small pressurized parts and supplies depot (not large enough for long term habitation without transferring supplies from the MTVL's). Basically, you have a mini-base you don't spend much time at except for supply replenishment midway through the surface stay and you have exploration vehicles actively hunting resources and interesting finds for as much of the surface stay as possible.

Unlike the Earth version of the MTVL, we don't need two 250kW motors to travel at over 100 kph on Earth (I don't want the Mars variant of the vehicle to go over 30 kph if anyone is inside it), lead acid batteries, an internal combustion engine to recharge the batteries, a thicker glacis plate, top hatches capable of supporting heavy weapon rings, etc.

Using micro capsules means we can EDL test ten or more of them with a single F9H launch. More testing under varied atmospheric conditions is the goal. Successfully launching one or perhaps two landers doesn't tell you much. For example, look at the number of STS flights that occurred before we had a failure. Similarly, we get to test ISRU for fueling the much smaller ascent vehicles and we get to launch more of them to a docking target in LMO to confirm through testing that the vehicles function as intended.

kbd512 · 2015-04-09 13:59:30

Rob,

If we include the third or perhaps a fourth rover in our exploration plans, then the unmanned rover(s) would function as spare parts, LOX generation, and water carriers for the two manned vehicles.

A basic Mars exploration convoy would consist of three or four MTVL's, all of the same basic design but carrying different cargo. The unmanned carrier rover(s) may also include equipment to obtain water from the soil.

That would more or less take care of air, water, and spares. With a four rover convoy, there's not much reason for landing a pressurized supply depot.

SpaceNut · 2015-04-09 19:00:39

I think we wouild be better of with something more like this:
NASA's Moon-Bound Geology Lab that Never Quite Got Off the Ground
GM completed the MOLAB (or "MGL" for "Mobile Geological Laboratory") in 1964 for NASA's use in the Apollo astronaut program.

The size of the MOLAB (20 feet tall, 8200 pounds) made it difficult to transport into space; it could only ride aboard a Saturn V.

Rather than a modified version of M113:

The interior is not bad...

RobertDyck · 2015-04-09 20:10:08

The Apollo LM initially had a total launch mass of 33,500 pounds (15,200 kg). That was used for Apollo 11, 12, 13, and 14. It was also used for Apollo 9 (Earth orbit), and Apollo 10 (dress rehearsal at the Moon). The LM for Apollo 15-17 was a little heavier: 36,200 pounds (16,400 kg). That included a lunar rover, and one more battery for extended stay on the Moon. The descent stage included propellant for de-orbit, as well as landing. The descent stage acted as the launch pad for the ascent stage. My point is there certainly wasn't room for a mobile geology lab.

The LM ascent stage had a gross mass of 10,300 lb (4,700 kg). An Apollo LM descent stage could have landed it, but then how do you get home? Could a separate Saturn 1B have launched it in parallel to an Apollo CSM & LM? The upper stage of Saturn 1B was S-IVB, the same as the 3rd stage of Saturn V, which was the TLI stage. Saturn 1 with the much smaller S-IV upper stage was able to lift an Apollo CSM into LEO without LM. But even if it could, how do you enter lunar orbit? Lunar Orbit Insertion was done by the service module. A separate LOI stage? Could Saturn 1B lift the S-IVB stage into LEO, plus the mobile geology laboratory, plus a modified LM descent stage, plus a custom LOI stage, and still have enough propellant left into the S-IVB stage for TLI?

One Apollo mission landed so closer to an unmanned lunar lander that astronauts removed parts for return to Earth. So the mobile geology laboratory could have been pre-landed, with an Apollo mission following. A skycrane like Curiosity could have done it, a lot lighter than a LM descent stage, but NASA didn't have that in the late 1960s. We'll never know.

But notice what I'm saying. The mobile geology lab would have to be landed in *ADDITION* to an Apollo LM. You need a way to get home. But if a Mars Direct ERV is your ride home, could you land a rover/hab?

James Cameron came up with a mission plan. He wanted a the crew lander to be a rover. But even his mission plan included a static base, using inflatables. Overview: click here.

kbd512 · 2015-04-09 20:10:37

SpaceNut,

Molab is far higher off the ground than the M113. The prototype shown is not reflective of the actual model NASA intended to use on the moon. Molab, like all NASA specials, uses giant wheels with little contact with the ground and a paper thin pressure vessel. Look at how much contact the M113 has and how thick the hull is. I would also like to point out that the variants you posted have five road wheels and are shorter than the MTVL, which has six road wheels and more internal space for cargo. The M113 weighs substantially more than MOLAB because it's more durable.

I found a photo that better illustrates NASA's MOLAB concept:

NASA recently revived the idea of putting a cylindrical habitat module on wheels. Dr. Zubrin proposed the "The War of the Worlds" thing years ago. What can I say? Some people really like wasting time and money.

kbd512 · 2015-04-09 20:55:33

The reason for not establishing a base with the first missions is simple. We're going to Mars to explore and to determine where the resources are. You only tend to do that when you're mission architecture is mobile. Any mission architecture that uses immobile habitat modules tends to have operations centered around that fixed site. That's the exact opposite of what we need if we truly intend to explore.

The only fixed site in my architecture is a designated launch area for four single person ascent vehicles, each vehicle separated by a few kilometers or so, for return to the MTV in LMO. My contention is that my MTV concept is suitable for deep space transit whereas small capsule ERV designs are not. My MTV concept has triple redundant power, life support, avionics, active radiation shielding, distribution of consumables amongst the three MTV modules, and artificial gravity. I think the most hazardous part of the mission, apart from ascent/descent from Earth and Mars, is the transit to/from Mars. Skimping on mass for the return to Earth makes no sense whatsoever. If anything goes wrong in transit, there is literally nowhere for the crew to escape to.

RobertDyck · 2015-04-09 22:58:03

We're going to Mars to establish the first off-world human settlement. That means building a home. Construction requires industry to mine and refine materials, to machine and manufacture parts. That starts as a workshop, and grows. And feeding settlers requires some sort of farm, most likely a greenhouse.

Part of my strategy is to establish a permanent human base on Mars, and park at ISS a reusable interplanetary spacecraft. Politicians will have difficulty not using them. If they do cancel all Mars efforts, then it becomes easy for a commercial like SpaceX to use them.

kbd512 · 2015-04-10 10:55:54

RobertDyck wrote:

We're going to Mars to establish the first off-world human settlement. That means building a home. Construction requires industry to mine and refine materials, to machine and manufacture parts. That starts as a workshop, and grows. And feeding settlers requires some sort of farm, most likely a greenhouse.

NASA's charter is to explore. I have no problem with them investigating technologies for colonization but NASA is a space exploration agency, not a space colonization agency.

SpaceX and others can concern themselves with the colonization of Mars. NASA desperately needs to develop a coherent development program to get there. Everything that Dr. Zubrin said about how you plan a mission is spot on. You first decide where you want to go and what you want to do. Then, you build the technology to achieve those goals. Giving people something to do is not a plan for space exploration, it's a plan to keep people busy. We could easily keep people busy developing the technologies that take us where we want to go so that we can do what we say we want to do.

Development of low cost descent/ascent vehicles and mobile surface exploration architecture is all about economic feasibility and getting the greatest science returns. We can't do the missions we say we want to do if we can't afford the vehicles to go where we want to go or if we intentionally make the explorers dependent upon a fixed site for operations.

If you take into account what's most affordable and therefore doable with reality based budgets to develop hardware in support of mission objectives, you'll see a running theme throughout everything I've proposed.

* F9H for launch services, whenever possible- Using the most affordable existing rocket to send hardware to Mars

* SLS tank and/or ISS module to construct the MTV- A proposal to use existing hardware for transit to/from Mars

* Single person landers- A proposal for using existing and demonstrated EDL technology to land humans on Mars

* M113 variants as rovers- Using existing, durable, and thoroughly demonstrated vehicles for mobility on Mars

I've intentionally set the technology development bar very low so that money can be directed to the handful of technologies that make all future long duration space exploration missions possible, namely closed loop life support, artificial gravity, and active radiation shielding.

If any part of a mission architecture is not affordable with respect to the overall budget, we simply won't do the mission. Each successive program for manned space exploration has been increasingly unaffordable. The giant multi-person descent/ascent vehicles (ERV's), giant space capsules (Orion), and giant rockets (SLS) are all unaffordable within existing budgets.

The maximum payload mass I want to land on Mars is around ~15t. All other plans call for landing payloads between ~40t and ~80t. There may be absolutely no difference in technology required to land ~80t, as opposed to ~15t, but one payload requires a single launch of the most affordable rocket we have, which is still $100M to $150M per flight, whereas the ~80t payload would require at least two flights. How many missions could we realistically afford if simply landing a habitat module cost more than a quarter billion dollars? No advanced mathematics are required to figure this out.

RobertDyck wrote:

Part of my strategy is to establish a permanent human base on Mars, and park at ISS a reusable interplanetary spacecraft. Politicians will have difficulty not using them. If they do cancel all Mars efforts, then it becomes easy for a commercial like SpaceX to use them.

As far as a commercial enterprise coming in and operating mission hardware built by other companies for NASA, that's unlikely to say the least. SpaceX has its own hardware development plans for Mars colonization. That's a good thing because SpaceX could never afford to operate the way NASA does.

RobertDyck · 2015-04-10 11:16:02

If you don't build anything, then as soon as some politician wants to spend money on something else, probably on Earth, they'll cancel the Mars stuff. What you are describing is the next flags-and-footprints that will be cancelled as fast as Apollo.

kbd512 · 2015-04-10 11:39:28

RobertDyck wrote:

If you don't build anything, then as soon as some politician wants to spend money on something else, probably on Earth, they'll cancel the Mars stuff. What you are describing is the next flags-and-footprints that will be cancelled as fast as Apollo.

Rob,

In all probability, there's a 1% or less chance of colonizing Mars within our lifetime and that's being overly optimistic. That'd be math speak for "ain't gonna happen."

However, we could, if we decided to, affordably put humans on Mars using the architecture I've outlined. All the science and technology development directed towards that effort doesn't have to completely disappear if NASA decides to maintain it rather than abandoning it as has been the case with the lunar program technology. There's a golden opportunity here to set sail for a new world. All that's required for that to come to fruition is for a decision to be made.

I don't think going to the moon was a mistake.

I don't think going back to the moon would be a mistake.

I don't think going to Mars would be a mistake.

I think trying to develop an unaffordable mission architecture would guarantee that we don't go anywhere within our lifetime and therefore would be a mistake.

The general public perception and the perception of politicians is that NASA is a special interest group and/or jobs program for intellectuals. They're not intelligent enough to make the connection between what NASA does and how it improves everyday life here on Earth and they never will make that connection. The spending is tolerated because it's tolerable.

Do we want to continue to dream about what could be if only the government rained down funding on NASA or develop a mission architecture that's affordable, in terms of both development and operations, with the existing budget?

From my perspective, not going because we can't have everything we really want seems more like a tantrum rather than the behavior of reasonable adults who work with what they're given to work with and make the best of what they have.

A handful of real manned missions with an affordable architecture is about as good as it's going to get.

RobertDyck · 2015-04-10 12:01:36

Your exploration mission is a demand for on-going copious quantities of cash. As long as you demand that, you get nothing. To use your words: "ain't gonna happen."

kbd512 · 2015-04-10 12:16:07

RobertDyck wrote:

Your exploration mission is a demand for on-going copious quantities of cash. As long as you demand that, you get nothing. To use your words: "ain't gonna happen."

Rob,

NASA has been supplied with ongoing copious quantities of cash for many, many years now. In fact, we've been at Apollo program levels of funding for many years now. It's been more than four decades since we've left low earth orbit. Sooner or later, someone's going to want something to show for all that money spent. Wouldn't it be better if NASA could say, "Mr. President, we have interplanetary transfer vehicles, landers, rovers to explore the surface of other planets with, and we use affordable rockets to launch it all." This would be in direct opposition to "Mr. President, we don't have manned space flight capability because our spacecraft costs too much to develop and we have a rocket we can't afford to launch it on."

Why do you think that development of things that we don't have money to develop, much less operate, is better than development of things we could actually afford?

If a single person lander is too expensive to develop, why would a multi-person lander cost any less?

If using armored personnel carriers that have been manufactured continuously for more than fifty years for surface exploration is too expensive, would development of a rover from scratch cost any less?

If using ISS modules or SLS tanks for a MTV is too expensive, are there other proposals that would actually cost less?

Everything I've proposed, apart from the landers, is reusable. Here on Earth, there's no such thing as reusability after reentry. There are spacecraft that are reused after months of refurbishment work in facilities employing hundreds of workers, but nothing amounting to actual reusability.

I don't understand your logic. Please elaborate.

Last edited by kbd512 (2015-04-10 16:06:58)

SpaceNut · 2015-04-10 22:30:29

http://en.wikipedia.org/wiki/M113_armor … el_carrier

Weight 12.3 tonnes (13.6 short tons; 12.1 long tons)
Length 4.863 metres (15 ft 11.5 in) Width 2.686 metres (8 ft 9.7 in) Height 2.5 metres (8 ft 2 in)
Crew 2 Passengers 11 passengers
Engine Detroit Diesel 6V53T, 6-cylinder diesel engine 275 hp (205 kW)
Power/weight 22.36 hp/tonne Suspension torsion bar, 5 road wheels
Operational range 480 km (300 mi) Speed 67.6 km/h (42.0 mph), 5.8 km/h (3.6 mph) swimming

Imperial ton of 2,240 lbs. or 1,000 kilograms is equivalent to approximately 2,204.6 pounds, 1.10 tons US long

Problem one for mars temperature which even if it could have the oxygen to allow the diesel to work would gel and clog in the tank.... 12.3 tons or 12.1 long ton... as compared to the MOLAB 8200 pounds or 3.72 tons and needs no extra oxygen to run.....Sure it has some things to change but its not massive beyond the small envolope profile which is what we wanted.

Also the tracks would be torn up in no time with mars jagged rocks and temperatures....much like the tires would and even the rims that we have on mars at current will not be good enough either for any rover for a crew In my mind...

The capacity for crew passenger while nice as you would want it filled with supplies but we are already to heavy to even land...

I agree that a thick shell is of importance but we can go overboard.

I understand tried and true for dependability but its still got to make the grade for use and on mars it does not....nor does the molab....

kbd512 · 2015-04-11 01:30:34

SpaceNut wrote:

Imperial ton of 2,240 lbs. or 1,000 kilograms is equivalent to approximately 2,204.6 pounds, 1.10 tons US long
Problem one for mars temperature which even if it could have the oxygen to allow the diesel to work would gel and clog in the tank.... 12.3 tons or 12.1 long ton... as compared to the MOLAB 8200 pounds or 3.72 tons and needs no extra oxygen to run.....Sure it has some things to change but its not massive beyond the small envolope profile which is what we wanted.
Also the tracks would be torn up in no time with mars jagged rocks and temperatures....much like the tires would and even the rims that we have on mars at current will not be good enough either for any rover for a crew In my mind...
The capacity for crew passenger while nice as you would want it filled with supplies but we are already to heavy to even land...
I agree that a thick shell is of importance but we can go overboard.
I understand tried and true for dependability but its still got to make the grade for use and on mars it does not....nor does the molab....

SpaceNut,

Please read what I proposed. I did not propose using diesel powered M113's on Mars. In fact, there is no internal combustion engine anywhere in my proposal. I proposed using all-electric MTVL's (the MTVL is a longer M113 produced by BAE with six versus five road wheels and 20% more internal volume). When you take all the heavy stuff out of the MTVL that has no use on Mars (equipment removal includes the diesel engine and transmission, top hatches, heavy weapons ring and turret, glacis plate, and steel tracks), you have a much lighter and more capacious vehicle.

My MTVL proposal is solar-powered. The vehicle would have two 30kW electric motors and a top speed not to exceed 32kph (20mph for us Americans) on Mars.

MTVL has multiple track options, ranging from rubber band tracks (requires a synthetic compound with a low glass transition temperature, as explained in previous posts), aluminum, and steel. Steel will not be "cut up" by the rocks on Mars. However, I think a particular compound with a very low glass transition temperature (developed by Dow IIRC) will permit use of lighter weight rubber band tracks.

The tires/rims on the Mars rovers are the dinkiest things imaginable that can still support the weight of the vehicle. Military vehicles routinely see abuse that NASA wouldn't dream of putting a rover through. Trust me, the tracks will be fine.

This is a cutaway of a hybrid electric MTVL interior (hybrid electric MTVL's with much more powerful electric motors and lead acid batteries have been built and tested):

http://www.combatreform.org/mtvlHEDtroopsinside.jpg

Using ADEPT + retrorockets and a SEP tug for orbital transfer (the SEP tug is a current development item for ARM), which is exactly what I prosed, we're not too heavy to land. I calculated the weight of the MTVL to be around ~15t fully loaded, but that weight could grow to ~17t and not present an issue with respect to mailing it to Mars with a single F9H flight. The SEP tug is around ~8t. That leaves ~25t for ADEPT and retro-propulsion mass with a ~3t margin.

Internally, the two crewed MTVL's would carry two astronauts, two navigational computers, two radios, two water storage units, two CL-ECLSS units, two food storage units, two mechanical counter-pressure suits, two hookah hoses for use while repairing the vehicle's running gear, two hammocks and blankets for nap time, one mini sit-down shower enclosure, one mini washer/dryer unit, one tool kit for field repairs, one medical kit, and one user's manual.

It might make sense to have a hatch separate the driver's compartment from the main compartment so that the driver does not have to don a suit while his or her partner performs an EVA.

Externally, the two crewed MTVL's would have two solar panels for recharging the batteries, two omni-directional antenna for the radios, a complete set of running lights (the vehicles are traveling in a convoy), and one spotlight for signaling and exploration of dark places (like lava tubes).

Internally, the two robotic MTVL's would carry two navigational computers, two radios, two water storage units, two CL-ECLSS units, two food storage units, two additional mechanical counter-pressure suits - one for each astronaut, two hookah hoses, one mini sit-down shower enclosure, one mini washer/dryer unit, spare rover batteries and electrical parts, one LOX generation unit for replenishment of the manned rovers, one mini-lab for samples analysis, one medical kit, and one user's manual.

Externally, the two robotic MTVL's would have two solar panels for recharging the batteries, two omni-directional antenna for the radios, and one unit for obtaining water from the Martian soil for water replenishment of the manned rovers.

My MTVL design puts the user replaceable batteries in the main compartment on the floor of the vehicle. The water bladders and food storage units are side-by-side over the tracks. The mini washer/dryer unit, mini shower, and kitchen are against the driver's compartment bulkhead. The suits and clothing are stowed near the exit hatch at the rear of the vehicle. One ECLSS unit is in the driver's compartment and the other is in the main compartment. The latrine is near the exit opposite where the suits are stowed. This arrangement leaves an open area in the main compartment so that the astronauts can move about without bumping into each other and hang their hammocks.

In short, my proposal ensures that our four Martians remain mobile in vehicles that are substantial enough to survive and small enough to transport using a single F9H flight. I'm not sure how much more detailed I can get before we start going through design processes.

Last edited by kbd512 (2015-04-11 01:38:24)

Antius · 2015-04-11 06:39:06

Interesting thread. I've only read about half of the posts so far and I am not so up to speed on the Mars thing anymore, so forgive me if I say something ignorant. A number of thoughts come to mind based on what I have read:

1. kbd512 raises some valuable points w.r.t the large redundant masses that might be avoided in repeat lander vehicles by scaling down hotel requirements. However, the use of minimalist lander vehicles with reduced long term life support imposes specific limitations on the use of those vehicles (i.e. landing in vicinity of a well-stocked, manned base). It also imposes additional risks, as the crew are in grave peril if they fail to do so. I would point out that there are risk analysis tools that allow engineers to balance risks against cost. This can in turn be used to determine a required minimal survival time for the vehicle in order to reach tolerable risk. If you are delivering to a manned base, then people can presumably reach you within a week, even if you land 1000km from the base. On the other hand, reduced hotel capabilities may prevent using the vehicle being used to reach another part of the planet to carry survey missions or a rescue. All of these things would have to be brought into a cost-benefit analysis.

2. The use of regional resupply dumps for rovers is a good idea in my opinion. It allows the range of surface exploration to be extended without the mass requirements of an entirely new Mars Direct mission. The supply station merely needs to contain additional fuel, food, water and maybe some spare parts for a rover. Landing mass might not be much more than a tonne, with a small solar powered Sabatier reactor making fuel and water.

3. If such architecture is workable from a risk point of view, then the Mars Direct architecture should be abandoned. It would appear more economical to focus all manned landings at a specific point on the planet starting with the first mission and use long range rovers to explore the entire planet from that point. That way, you don’t need to deliver a new hab to the planet for every new mission and you can use that additional payload to ship out valuable equipment, which could extend the capabilities of the base. Establishing a single base from day 1 has a lot of advantages in terms of concentrating resources. In that case, you would want to choose a site for which it is easy to achieve a landing, relatively close to the equator and low altitude. Isidis and Chryse Planitia appear to provide a good balance for these requirements.

4. If reusable landing vehicles are developed, then it also makes sense to develop a reusable Earth-Mars solar electric transfer vehicle. Only humans strictly need to return to Earth, so my suspicion is that the transfer vehicle would be dedicated to human transport, plus a few rock samples on the return trips. Cargo delivery will probably be carried out using direct throw heavy lift vehicles for some time to come, which only need to travel in one direction.

kbd512 · 2015-04-11 09:44:58

Antius wrote:

Interesting thread. I've only read about half of the posts so far and I am not so up to speed on the Mars thing anymore, so forgive me if I say something ignorant. A number of thoughts come to mind based on what I have read:

The pertinent points are:

* Absolute minimum mass EDL solution using single person unpressurized capsules with HIAD + parachutes for EDL

* Four single person ascent vehicles pre-positioned and fueled on Mars using ISRU in a designated launch area (ten kilometers or more away from the landing area)

* Three or four all-electric rovers based on the thoroughly proven MTVL (larger M113 variant) design pre-positioned on Mars

* Two crewed rovers, seating two astronauts apiece, are tele-robotically operated by the remaining crew in the MTV to collect the first two astronauts who land; radio homing beacons and robotic operation are a backup

* One or two robotically controlled rovers as mobile spares (identically equipped to the crewed rovers except for spare parts, a mini-lab for samples analysis, and units to obtain oxygen and water from Mars)

* The unmanned rover or rovers follow the manned rovers in convoy for exploration ops; if a rover fails, for whatever reason, there's a backup traveling with you wherever you happen to be

* ~15t to ~17t landed cargo mass cap, so each MTVL requires a single F9H launch and lands using ADEPT + retrorockets for EDL; the MTVL can actually carry far heavier payloads at lower speeds, if required

* All cargo landed on Mars uses a single F9H (MTVL's, crew supplies and spare parts, experiments)

* Only the Mars Transfer Vehicle requires multiple launches (a manned mission to Mars is a flagship mission, so the insanely expensive SLS may validly be utilized to launch the core module or modules to reduce assembly steps)

Antius wrote:

1. kbd512 raises some valuable points w.r.t the large redundant masses that might be avoided in repeat lander vehicles by scaling down hotel requirements. However, the use of minimalist lander vehicles with reduced long term life support imposes specific limitations on the use of those vehicles (i.e. landing in vicinity of a well-stocked, manned base). It also imposes additional risks, as the crew are in grave peril if they fail to do so. I would point out that there are risk analysis tools that allow engineers to balance risks against cost. This can in turn be used to determine a required minimal survival time for the vehicle in order to reach tolerable risk. If you are delivering to a manned base, then people can presumably reach you within a week, even if you land 1000km from the base. On the other hand, reduced hotel capabilities may prevent using the vehicle being used to reach another part of the planet to carry survey missions or a rescue. All of these things would have to be brought into a cost-benefit analysis.

If you are completely mobile on Mars, you don't have to worry about how far you landed from a stationary habitat module. If a habitat module becomes uninhabitable or you can't reach it to begin with, you have a serious problem. Each MTVL is laden with approximately half of the supplies required to sustain the explorers for a 500 day surface stay (the number I used when I calculated how much food, water, and oxygen was required).

This architecture is not about better survivability, that's just a welcome benefit that comes from layers of redundancy, it's about better mobility and having a real capability to explore. The MTVL is your home, not a large stationary habitat module that virtually guarantees you'll never explore very far from home.

Antius wrote:

2. The use of regional resupply dumps for rovers is a good idea in my opinion. It allows the range of surface exploration to be extended without the mass requirements of an entirely new Mars Direct mission. The supply station merely needs to contain additional fuel, food, water and maybe some spare parts for a rover. Landing mass might not be much more than a tonne, with a small solar powered Sabatier reactor making fuel and water.

Then you have to travel to the supply dump for resupply, rather than carrying supplies and spares with you in additional rovers. What's better in the Sahara, having a supply dump 100 kilometers away or another fully functional vehicle in your convoy? The rovers don't use fuel, so no fuel is required. The all-electric rovers would need spare batteries, solar panels, and running gear. No Sabatier reactor or nuclear reactor is required, either, except at the ascent vehicle launch sites.

Antius wrote:

3. If such architecture is workable from a risk point of view, then the Mars Direct architecture should be abandoned. It would appear more economical to focus all manned landings at a specific point on the planet starting with the first mission and use long range rovers to explore the entire planet from that point. That way, you don’t need to deliver a new hab to the planet for every new mission and you can use that additional payload to ship out valuable equipment, which could extend the capabilities of the base. Establishing a single base from day 1 has a lot of advantages in terms of concentrating resources. In that case, you would want to choose a site for which it is easy to achieve a landing, relatively close to the equator and low altitude. Isidis and Chryse Planitia appear to provide a good balance for these requirements.

With a completely mobile architecture, we're not tied to a specific point on the surface. That means we could just as easily land our ascent vehicles and rovers on the other side of the planet for subsequent missions. The entire problem with using stationary habitats is what it costs to land it on Mars. It's a launch vehicle economics problem. You would need a minimum of two F9H launches to land one 40t habitat module. You land 6t more of supplies/habitat with two F9H launches, but your cost doubles and you don't get double your initial capability with that second launch, as most of the mass of the second launch is for EDL equipment.

Antius wrote:

4. If reusable landing vehicles are developed, then it also makes sense to develop a reusable Earth-Mars solar electric transfer vehicle. Only humans strictly need to return to Earth, so my suspicion is that the transfer vehicle would be dedicated to human transport, plus a few rock samples on the return trips. Cargo delivery will probably be carried out using direct throw heavy lift vehicles for some time to come, which only need to travel in one direction.

My MTV proposal uses SEP. The MTV is assembled and loaded with supplies in LEO at ISS, robotically transferred to L1, the crew use Dragon and F9 or F9H to transfer to the MTV, and the crew departs for Mars from L1.

There's no such thing as a reusable lander. Once reentry is performed, refurbishment is required. This requires facilities and transportation infrastructure to accomplish that is not present on Mars.

Cargo delivery from direct throw severely limits payload. Therefore, I am using the same SEP tug being developed for ARM in my mission architecture.

kbd512 · 2015-04-11 15:40:34

Regarding the internal design and parts replacement schedule for the rovers, each MTVL will have user replaceable subsystems.

After the initial effort to land the fully functional and loaded rovers, subsequent mission will send only parts and crew consumables, rather than entirely new rovers.

Every two years, the band tracks (we want to use these if at all possible because they weigh approximately 45% of what steel M113 tracks weigh and have a much better operational life; the M113 band tracks weigh approximately ~730kg figure around ~810kg for the longer MTVL tracks - provided by Soucy International from Canada), batteries (I presume Tesla lithium ion), running gear (UHMWPE with an ultra-low glass transition temperature - also provided by Soucy International), navigational computer (Apple), radios (Harris or Thales), CL-ECLSS units (NASA), solar panels (ATK), shower (NASA), and toilet (NASA) are replaced.

The band tracks have a design life of ~8000km (a newer design than the design tested by DoD), a ~67% lower rolling resistance compared to steel tracks, and 50% to 70% lower vibration (this is extremely important because prolonged high levels of WBV can cause nausea) compared to steel tracks. Actual DoD testing has shown that the band tracks have a life of ~4700km here on Earth before separation (20% paved roads, 40% gravel, 40% off road; we need to test on 100% crushed granite and/or lava to determine performance on Mars), but we'll assume the tracks only have a 2000km life on Mars. Although not a good analog for Mars, the Soucy band tracks have been used on combat vehicles in Afghanistan.

Every four years, the water tanks, food storage units, and food preparation unit are replaced.

Here on Earth, M113's are in service for decades prior to replacement, but we'll assume an ultimate design life limitation of ten years due to numerous pressurization cycles and exposure to severe temperature changes. Changing a single track takes two people approximately 90 minutes here on earth, which is much longer than for steel tracks, but we'll assume approximately 3 hours on Mars. The first day or two of each subsequent mission is spent refitting and restocking consumables in the rovers and the second or third day is for retest of all critical subsystems using the new components.

Assuming no complete rover failures that strand a particular rover or rovers, each subsequent mission could expect to deliver a single replacement parts kit for four rovers and replacement consumables via two F9H flights. This means that any additional flights budgeted would be devoted to stationary habitat modules, if appropriate for mission objectives, or multi-person ascent/descent vehicles as funding for those technologies becomes available.

kbd512 · 2015-04-11 16:43:31

If, for whatever reason I can't think of at the moment, it's necessary to severely constrain propellant mass requirements for return to Earth and to reuse the SEP tugs that transfer the rovers and the MTV to Mars, we'd develop an updated PROFAC (PROpulsive Fluid ACcumulator) to separate Ar from CO2 and O2 from CO2 (for use in chemical kick stages with methane imported from Earth).

PROFAC is a space-based nuclear reactor that collects and liquefies the atmosphere from a low orbit, uses a portion for propulsion to counteract gravity and drag losses and stores the rest for transfer to other vehicles.

Mars atmosphere is about ~1.9% Argon. Argon is not as good as Xenon for electric propulsion, but Xenon is insanely expensive and the cost of launching it to Mars is added to that. Once the hardware has been developed and the PROFAC units are in operation in LMO, return propellant for use with SEP is essentially unlimited and the MTV's need not carry the added mass of propellant for return to Earth.

The LOX for chemical kick stages would come from PROFAC, too. Using a VUV laser (presumably a 10MW nuclear reactor can provide power for the laser), you can separate carbon from carbon dioxide.

The chemical kick stages are only necessary if someone is insistent on "getting there fast."

Anyway, just an afterthought for lowering the mission masses and reusing the SEP tugs required to ship all this hardware to Mars.

Some trade studies would have to be conducted to determine how many missions we'd have to execute for the hardware to pay for itself in terms of operational costs.

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