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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.
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.
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.
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.
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.
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.
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.
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.
The beginning and end of the problem is the impetus for change and the nature of our political structures.
For quite some time, ULA was the only company to go to for launch services here in America. We now have a set of fledgling companies that are cost competitive with ULA and capable of delivering services. Purchasing proclivities won't change until there is an impetus to change. We should start by cutting the budget of the Air Force. USAF would then need to decide whether or not they want/need silly little things like GPS. If you want/need that capability, then issue contracts to companies who can provide services at sane prices.
The government is well aware that ULA has broken the law pertaining to cost increases but refuses to do anything about it. Both political parties are part of the problem and neither has made any serious attempt to rectify the situation. In an ideal world, USAF would realize that they have far less expensive options for launch services, select a company capable of providing services at a reasonable cost, and use the money to fund the purchase of other items like the F-35.
With respect to government procurement practices, there has not been any such thing as a level playing field in living memory. Our revolving door political / corporate lobbying cabal actively attempts to influence purchasing decisions with bribes, better known as campaign contributions and employment, and it's so naked that only willfully ignorant people wouldn't notice it. Whether strictly legal or not, it's inherently corrupt. As such, the procurement process for major purchases now has little or nothing to do with how cost competitive a good or service is.
We can complain about this until the cows come home, but apart from booting both parties and electing independent candidates, I don't see this changing. Even if we elect independent candidates, I don't think it's possible to have good stewards of our money until such time as all corporate contributions to campaigns are outlawed, that law is actually enforced, and nobody who was a lobbyist can ever become a politician and vice versa.
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.
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.
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?
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.
Lets look at it another way. If you are on Mars, for what purpose would you try to reach orbit, if not to return to Earth?
If there was some other part of Mars you wanted to go to, wouldn't it make more sense to take a surface vehicle? Blasting off into orbit takes a lot of fuel, and most landers are designed to leave parts of themselves behind when they take off again, so they typically aren't reusable. If you want a second landing, you will have to bring a second lander, now it is possible but expensive to have two surface missions going at the same time on different parts of the planet.
You mean like a habitat failure or some kind or loss of supplies required for sustainment?
Even if your rover won't run or your habitat has a hole in it, you still need air, food, and water. If you can make it to an ascent vehicle, hopefully the MTV fared better than whatever caused you to cut your Martian travel plans short.
In my plans, there are two 20t pressurized rovers (electrically driven, solar powered M113 derivatives) and a habitat module that's more pressurized storage than a place I intend for the astronauts to live. My boys and girls are wild red rovers, not squatters. Martian cavalry, such as it were.
In any event, both the rovers travel convoy style for mutual protection. If either vehicle has a major malfunction, the other is immediately available to collect the astronauts from the stranded vehicle and either assist with repairs or return to the storage habitat for parts to fix the busted rover.
If a repair can't be effected, then absent a spare rover the surface exploration mission is largely over. They could either mill about their base site for the remainder of their time on Mars or return to an orbital station for a new dragon lander (no rovers if the rovers aren't close enough to drive themselves to the new site, but them's the breaks) and open a new base site.
More options means a far greater return for our efforts.
And criminals *need* to stop committing crimes. Just saying it doesn't make it happen.
You're absolutely correct. I like to write letters and make phone calls to my Congressmen and Senators and anyone else I think might listen who could actually do something about it. I have no idea what effect I have, if any, but it won't stop me from trying.
GW, another point. You said any government funded mission to Mars would most likely only happen once. That means no way to do the human scouting that you describe. Any human mission means one trip from Mars orbit to the surface and back. One. No mission will park in Mars orbit and send multiple excursions to the surface. We just don't have propellant for that. In fact, to make a single mission affordable, we have use ISPP for just one.
Think positively, Rob. Would anyone complain if NASA built an orbital station at Mars? Certainly not I. The longer we maintain a presence there, the better. For whatever reason, all space agencies love their space stations. Let's build the next space station at Mars.
Mars sample return can be done as a Scout class mission. That means a budget between $300 million and $485 million, including data analysis. Analyzing returned samples may cost more, in fact scientists would go nuts over samples. Keeping a sample return mission that low is possible, but only if you use ISPP, and don't use a large rover.
Could we analyze samples at a space station at Mars?
Actually, I'm uncomfortable with sending robotic probes to potential sites for human exploration. That's too many robotic probes. JPL sent a lot already. We should be able to select a location with data from existing robotic explorers: orbiters, landers and rovers.
You're probably right.
So build a permanent base with the first human mission. And park a reusable Interplanetary Transit Vehicle at ISS. Then if politicians cancel any further exploration, a commercial corporation could use that reusable vehicle to return to the permanent base.
Even though it's what we ultimately need to do, construction of a permanent base would take many years. A handful of F9H launches or two SLS launches and we could have an orbital station delivered. From there, we could stage Red Dragons for future or contingency use, cache spares and supplies, and use tele-robotic rovers to explore as much of the surface as we can before we send humans. If the MTV's use electric propulsion, we could refuel there, too.
Argon may not be as good as Xenon, but there's plenty of it in the Martian atmosphere. Seems like a shame to drag all that propellant from Earth just to get back there. Finally a socially acceptable use for Profac? Just a thought.
GW, I see what you're saying. But I still point out that Mars atmosphere blocks a lot of radiation. And completely eliminates micrometeoroids; they burn up 30km or higher above the surface, depending on size of meteoroid. And you have gravity. Yes, you keep arguing for artificial gravity for the transit vehicle, which means both have that so no difference. But NASA so far is absolutely afraid of artificial gravity. The bureaucrats are afraid of anything new, so someone is going to have to demonstrate it in space before they even consider it.
NASA needs to get over their fears of artificial gravity and use it for the benefit of their explorers. Humans don't fare well without it.
Robert Zubrin has argued strenuously for his plan. It was very valid in 1989 & 1990, but I argue some aspects are obsolete. For example, he said don't build a space station in Earth orbit. Well, we have it now, so let's use it. NASA wanted a life support system that could recycle 95% of water and oxygen, but he argued to go with what existed at that time. Robert Zubrin said if we wait for a 95% efficient life support system, it would be the 21st century before we're ready to go. Well, it is the 21st century now; we've pissed away so much time that the 21st century caught up with us. And ISS only needs a few additional specific pieces of equipment to make it 95% efficient. He argued for initial exploration by humans, not robotic explorers. Some who like robots would argue, but my point is this is now moot because robotic exploration is essentially complete. We should send a robotic lander to each potential site, specifically designed to evaluate for the human base. I waffle between a lander with tiny rover like Pathfinder, or MER rover. But definitely an MSL rover would be *way* overkill.
NASA's manned space program is still busily pissing away funding on things that won't ultimately permit them to explore our solar system. Obama gave them an opening and they didn't take it. It's time to start serious development of closed loop ECLSS, active radiation shielding, and ISRU. Our propulsion technology is near to where it must be to support sustainable exploration activities, but after three decades of throwing money at various high-risk, high-payoff technologies we still don't haven't CL-ECLSS, ARS, ISRU, or an affordable HLV. If we don't right the ship now, NASA is at substantial risk of having its manned space program shut down by short-sighted politicians.
And we need to test/demonstrate ISPP with a robotic Mars lander. Either a sample collection arm like Phoenix, or tiny rover like Sojourner. You definitely don't need an MSL size rover. And you don't need multiple Mars sample return missions, just one to demonstrate ISPP.
The sooner, the better.
The beauty of ISPP designed by Robert Zubrin and David Baker is that it uses Mars atmosphere. Not Mars permafrost. One reason is Mars atmosphere is already well characterized, so we don't need any further data. But the real beauty is the atmosphere is the same across the planet. So ISPP works the same anywhere on the planet.
Unfortunately, the Martian atmosphere isn't the same everywhere on the planet except in general composition. We still need ISPP, so we have to find a way to make it work.
Or are you talking about ISRU for construction material? That's tricky. You'll never find a single site that has all resources you would want. Have to pick which you want to focus on. Curiosity found hematite and cristobalite, the first is iron ore, the second can be melted to form glass. There's abundant plagioclase feldspar in Mars soil everywhere. The trick is to find plagioclase with more than 70% anorthite (calcium aluminum silicate). If it has too much albite (sodium aluminum silicate) it won't dissolve in acid. The Bayer process extracts aluminum from bauxite, you can reverse the pH to do it with plagioclase feldspar high in anorthite. So iron, glass, and aluminum all in one spot! And Curiosity hasn't found ice, but soil minerals that release water when baked; about 2 pints per cubic foot of soil. Great! Would be nice to get other metals as well, such as copper for electrical wiring, but as I said you aren't going to find everything at one spot.
We're many decades away from mining building materials on Mars. That shouldn't stop us from locating the resources and experimenting with the most efficient methods of obtaining them, but it'll be quite some time before we can actually use them.
Rob,
I would never suggest leaving any of the crew in orbit around Mars. My assumption has always been that they're all going to the surface. All other suggested approaches to landing humans involve vehicles that are many times the mass of what I've suggested and have a hard requirement for retro-propulsion. I understand that ADEPT, or something like it, is an absolute requirement for cargo and therefore the same tech would be available for crewed landers. However, there's virtually no chance that a lander that requires retro-propulsion would be less expensive or time consuming to develop.
NASA is either lying about the problem or overly concerned with radiation, but I think the MTV will have adequate radiation shielding or they won't go. I would think that any responsible planner would have to at least consider the possibility that once the crew arrives at Mars that they can't all land, or land at all, or are prevented from using the free return trajectory to abort. If there's no one aboard the MTV and something fails while the crew is on the surface, there are few possibilities for repair.
Any potential for stranding applies equally to any landing scheme. As previously stated, if a single multi-person lander with the entire crew aboard fails, then the entire crew is lost and the mission is lost. If each person has their own lander, loss of one lander doesn't cause instant loss of mission. I'm not overly concerned with a single or multi-person lander failure, but any honest assessment of what happens after a lander failure indicates the obvious.
Thanks for all the input on this. After consideration of all the potential problems, micro capsules are most definitely Plan B. However, if Plan A (development of a proper multi-person lander combined with a fully fueled ascent vehicle) is so expensive as to be unworkable, then I think Plan B should receive some consideration because it's still better than no plan at all, which is what we currently have.
Rob and GW, thank you for the criticism of this plan. Every plan needs a reality check. I still think Plan B is workable, but it would most definitely require further experimentation just to prove feasibility. It may only be workable under specific atmospheric conditions on Mars.
So far, I've come to the conclusion that any significant navigational error with a micro capsule is likely to result in the death of the astronaut inside, once you commit the inflatable aeroshell and parachute have to work perfectly because there's no abort-to-orbit capability as with a multi-person lander, and the density variability of the Martian atmosphere may make the size of the parachute required to guarantee a soft landing without airbags or retrorockets impractical. To my knowledge, a soft landing on Mars without airbagas and/or retrorockets has never been done, so this may be impractical. However, the payloads in question were also substantially heavier than the micro capsule would be, so if the payload is light enough and an inflatable aeroshell can bleed speed quickly enough, landing on a parachute alone may still be practical.
No matter how small, development and testing of altimeter triggered retrorockets that work perfectly, every time, on another planet is sure to be insanely expensive. If there's a simpler and less expensive option to successfully complete EDL for humans, then that's what we should work on until the Orion and SLS spending projects are over. Once we've blown enough cash on those two projects without meaningful result or someone at NASA grows a pair and says what needs to be said to the morons in Congress, then we can develop two stage multi-person landers that can return to the MTV if they land substantially off-course.
At no time have I thought that my solution was in any way optimal, but a $3B total outlay over six years is eminently reasonable compared to the alternatives. Any multi-person lander with contingency supplies that includes a fully fueled ascent vehicle is far, far preferable to my solution.
If we have reasonably priced and fully tested EDL solutions for humans (HIAD + Parachute) and cargo (ADEPT + retro-propulsion), I think we stand a far better chance of going to Mars than if there was no solution because we had to wait ten or more years for funding availability. ADEPT and retro-propulsion are a little further away than HIAD and parachutes; just far enough that I think two separate approaches to solving the problem is appropriate.
Even in the Martian atmosphere, I have a hard time believing that we would not achieve a substantial reduction in velocity before touchdown with a payload that's less than half the mass of Pathfinder, using the same size/type parachute, and an inflatable aeroshell capable of generating more lift than the rigid aeroshells used by Pathfinder and MSL. We may still need some sort of airbag to absorb the impact on touchdown, but if it's possible to only use HIAD and a parachute, that's the way to go.
I am submitting a request for MarsGRAM data to NASA so that I or someone else can determine what the feasibility of soft landing 150kg or less without retro-propulsion would be.
GW,
Is there any reason why it would be impossible to slow the capsule to subsonic velocity using lift from the inflatable heat shield, at which point a more effective parachute could be deployed?
I need to know the drag coefficient for the type of supersonic parachute that Pathfinder used and what the density of the atmosphere is between 15km and the surface if you have that information. You seem to have some goodies that JPL provided to you, so I thought I'd ask.
The velocity of Pathfinder was between 50m/s and 60m/s when it fired its retrorockets. Any idea what that velocity would have been if it used the same parachute and weighed half of what it did?
Heck, MSL's velocity was only ~80m/s at ~1.6km in altitude when it fired its retrorockets. Is there some reason why it's not possible to skirt around the requirement for retro-propulsion with more altitude and a lighter payload?
SpaceNut,
I'm trying to avoid using sky cranes, retrorockets, and even supersonic parachutes if it's possible to use inflatable heat shields and subsonic parachutes only. Steering control for the parachute is as fancy as I want to get. The goal here is to land the astronaut and a couple extra oxygen bottles a few hundred meters from the mobile habitats and that's it. Two mobile habitats will be in the landing area to collect the four astronauts.
I discussed updating Mars Direct. That means sticking with Robert Zubrin's mission architecture, not mine, but building it with current equipment. Robert Zubrin's ERV includes a capsule, and a 2-stage rocket to throw directly from Mars surface to trans-Earth trajectory. That 2-stage rocket would use LCH4/LOX engines, and would be a new rocket. One point I made is rather than develop a new capsule, use Dragon. However, to survive 6 months you would need a small, light-weight module attached to the nose with recycling life support. I suggested the same life support as ISS, and just barely enough room for one person to float in the centre to do repairs/maintenance. Base the hull of that module on Cygnus, but smaller. That module would be discarded before entering Earth's atmosphere.
Using a minimum mass ERV sounds expensive, difficult, and potentially far more hazardous than an off-course landing on Mars.
The capsule I proposed is for LMO to Mars and Mars to LMO only, rather than any type of interplanetary transfer.
And I argue that NASA has enough money to do all this right now. They don't need more money. It would require cancelling Orion and ARM, complete SLS, give up on the Moon and Constellation, focus exclusively on Mars.
I like the fact that the plan involves going to Mars instead of playing with space rocks, but I also think that what you're proposing would cost every bit as much as Orion's development and then some. Dragon, like Orion, is incapable of sustaining the astronauts for the period of time they're in deep space between Mars and Earth and docking a sustainment module to the front of the capsule doesn't make it a deep space habitat. If you're sending your explorers to Mars in a ITV/MTV anyway, why not bring them back in that vehicle? We now have reliable propulsion capable of doing that without blowing mass budgets and therefore breaking the bank.
Even if we complete SLS, what does SLS do for us except suck down a few billion in development and operations each year? It's entirely wrong for any type of sustainable Mars exploration campaign.
With NASA's current budget, it can't spend a few billion on ISS, a few billion on SLS, and a few billion on Orion every year and have funding remaining for closed loop ECLSS, deep space habitats, landers, and ISRU. Two of the three would need to be cancelled if we ever want to go to Mars. ISS has the potential to have real utility to assist with that goal, whereas an unaffordable rocket and an insanely heavy capsule don't.
And I said Dragon is appropriate to return crew to Earth. The heat shield material is appropriate for Mars. A custom lander is required for Mars. Dragon can be used either by Mars Direct as the ERV capsule, or as an emergency escape pod for a reusable ITV during aerocapture at Earth. Dragon is the not the Mars lander. I never said it is. You are obsessing about Red Dragon from the Mars One mission plan. I don't know anyone here who believes that's a good plan. MIT did an analysis, they believe settlers would survive 2 weeks after arriving on Mars. Yes, a multi-person capsule does have to be substantially redesigned to use ADEPT. One option is the Mars Direct habitat (hab). I came up with a mission plan to use Russia's Energia, so suggested a minimum size landing capsule and all-inflatable surface habitats. That plan was developed in 1999-2002 when Russia was behaving itself. The idea of using Energia was from Robert Zubrin's book "The Case For Mars". As Dr. Zubrin said in his book, using Energia requires splitting the mission into 3 parts instead of 2, because Energia has 2/3 the lift capacity of Saturn V / Ares / SLS. Doing it today with SLS might permit a hard wall habitat. But that's all custom landers. At no time did I ever claim that Dragon was the Mars lander. What I do say is Dragon can be used for return, and Dragon is overall a much better choice than Orion. That's because Dragon has a dry mass of 4.3 metric tonnes, with full fuel tanks (wet mass) is 8.0 metric tonnes. Orion is much heavier, with fairing and LES and full tanks it's 28 metric tonnes. I've said this many times. That doesn't mean I claim Dragon is the crew lander.
What is your proposal for this custom multi-person lander that we don't have money to develop, Rob? Please share your proposal. When do you think we'd have money for that? Around 2030, maybe?
Dragon's going to be an ERV? Got it. Now we just need to land a rocket big enough to launch it off the surface of Mars. What would be easier to design and test on Mars, rockets capable of lifting 1t to LMO or 8t to LMO?
I'm obsessing over Mars One? Find a post of mine, except this one, where I mention it. I've never seen any of their proposals, so I'll have to take your word for it.
As for MER, yes it is a fair comparison. Don't you think they would have landed with parachutes if that would have worked?
The retro rockets on MER brought the lander to a full stop 10M above the surface and then dropped the lander onto the surface. The peak deceleration that you referenced was the result of the lander slamming into the ground after it was dropped. MER weighed 533kg. Micro capsules will be significantly lighter.
Rob,
I'm tired of arguing the point with you. You keep using arguments that apply equally to any EDL solution or are demonstrably false. When that doesn't work, you propose something that I did not in order to construct something with weight/dimensions/reentry profile/etc that won't work on Mars without lots of expensive, complicated, and failure prone technology.
The micro capsule is an unpressurized aluminum trash can with a fabric seat bungee corded to the walls and a service module attached to its rear end with an inflatable or deployable heat shield (I don't care which) and reaction control system for de-orbit. Anyone with the desire and enough time on their hands can engineer it into a Rube Goldberg contraption that won't work reliably on Mars, but you have to work overtime to do it.
I wanted to keep EDL for humans on Mars spectacularly simple, which would be a first for anything designed by NASA, but some people apparently have complexity cravings that rival NASA's. Multi-person landers are an admirable goal, something I would love for us to build, but there's simply no funding to do that because Congress forced us to squander so much of our available funding on Orion and SLS rather than a spacecraft that could actually land on something other than Earth or a rocket that we could afford to operate. Unfortunately for us, funding hasn't been coming out the wazoo lately.
Rob,
Dragon's problem with reentry on Mars doesn't have anything to do with its heat shield material, it has everything to do with its weight and ballistic coefficient. It doesn't land enough mass to be anything more than a more expensive flying coffin than a micro capsule would be, if either land substantially off course.
Your second argument was that this thing will experience a higher peak deceleration force than a sitting astronaut can tolerate. That's been pretty thoroughly debunked by GW and the documentation by NASA regarding peak reentry deceleration forces encountered on Mars from actual missions. MSL encountered a greater peak declaration force for the reasons I already noted.
Your basic grade school education about area and volume ignores the fact that Red Dragon is already substantially more massive than 4 micro capsules would be because Red Dragon lands propulsively.
Regarding how inflatable heat shields are "different" from using deployable articulating heat shields for the entire crew, the only multi-person capsule that could potentially land on Mars would have to be substantially redesigned to use this novel new ADEPT technology. I don't care if NASA does that, and it would be my preference, but so far there's no talk of doing that.
Regarding MER, it's not a valid comparison. The lander weighed 533kg and it was dropped from a height of 10M onto the surface of Mars. The capsule plus astronaut won't be anywhere near 533kg and we're not dropping it from 10M with the astronaut in it.
In order to produce pressure vessels of substantial size, such as those required for attachment of Centaur like upper stages to planetary probes, satellites, and repurposing of space junk, an empty SLS tank should be utilized.
SLS can put 70t in LEO with no upper stage. If an orbital manufacturing facility could be attached to ISS, then we could have astronauts separate the interstage, LOX, and LH2 tanks. The expensive RS-25's could be de-orbited using HIAD or ADEPT instead of reactivated Space Shuttles (an earlier concept I wanted to employ that, thankfully, is no longer necessary because we have like-kind capability), captured mid-air by aircraft, and returned to KSC for reuse. $288M is too much cash to blow on RS-25's alone.
We still need SEP tugs for collecting space junk and a fuel depot, which should not be anywhere near ISS for obvious reasons. Satellites and upper stages would be refitted or refurbished at ISS. The SEP tugs transfer the remanufactured satellites and upper stages to the fuel depot for relaunch. Any SEP powered satellite or probe and the tugs could be refueled with Xenon/Argon/Krypton at ISS.
Rob,
Moreover, it wouldn't matter if an astronaut was flat on his or her back at 12.9 G's, he or she would be unconscious either way. Perhaps I'm oversimplifying things, but it seems as if JPL has two problems to solve here.
P1. In order to decelerate fast enough for supersonic parachutes or retro-propulsion to function properly, our reentry vehicle has to bleed away enough of its initial velocity at an altitude high enough above the surface of the planet to permit effective use of parachutes and/or retrorockets. This generally means a shallow entry angle that will increase peak heating.
S1: Develop lightweight materials capable of withstanding higher heating and reentry vehicle shapes or structures that lower the ballistic coefficient.
P2. In order to reduce peak deceleration force to levels tolerable by humans, a lower rate of descent is required. This generally means producing lift to counter gravity, thereby decreasing the rate of descent.
S2: Use the reentry vehicle's shape and center of gravity manipulation to produce lift.
MSL's reentry angle was around 20 degrees to reduce peak heating. The combination of the weight of the vehicle, relatively small lifting body, and poor lift generation created a plunging descent, increasing peak deceleration force. JPL and NASA favor plunging descents for unmanned reentry vehicles subject to substantial peak heating, as unmanned vehicles can readily be designed to survive deceleration forces that would injure or kill humans.
The micro capsules I proposed would reenter at shallow angles, have far lower ballistic coefficients than MSL, and generate more lift than MSL was capable of generating. You keep trying to invalidate this micro capsule concept using faulty logic that does not correlate with what NASA has published with regards to reentry. Even if what you stated applies to the micro capsule concept was true, which it is not, then it applies to an even greater degree to larger capsules with higher ballistic coefficients and lower lift generation capability.
A single person capsule can be made so light as to be capable of landing by parachute alone, especially if the service module and inflatable heat shield are discarded before landing. The same cannot be said for the multi-person capsules and heavier rovers or surface habitats.
SpaceNut,
Without an altitude at which peak G's are experienced, how can we determine that the reentry peak deceleration force on Venus would be the same as it is on Mars? Do you have an atmospheric density model for Venus? MSL reentry started around 125km at 5.9 km/s, experiencing a peak deceleration force of 12.9g, and it was ~127kg/m^2. One of the hypothetical sphere cone reentry vehicles in Fig 2 experienced 32g at an unspecified altitude and was 44kg/m^2. Between 200km and 75km in altitude, is the density of the atmosphere on Venus an analog for Mars? What am I missing?
The ARM is a total waste of time and money and I think NASA is paying lip service to the idea with the knowledge that this nonsense mission will be cancelled when Obama leaves office.
If this new space station has, artificial gravity, closed loop ECLSS, active radiation shielding, and a manufacturing facility, then I'm all for it. However, I see this as yet another potentially expensive distraction that prevents us from developing the technology to go to Mars.
NASA doesn't need any international cooperation to go to Mars, it just has to decide that that's the goal and then develop a coordinated plan to develop the technologies required to take us there. I would much prefer international cooperation and that all space faring nations coordinate their efforts to achieve the goal of becoming an interplanetary species, but politics always seem to interfere.
The existing budget is more than adequate to achieve the goal, but all the uncoordinated and expensive make-work projects need to end. SLS and Orion need to be cancelled ASAP. There's simply too much funding that has been funneled into these projects to justify the relatively meager returns and insane costs.
That may explain why you keep raising concern about coming out of hypesonics too low. What happens if you use something like ADEPT? That's a carbon fibre foldable heat shield. The goal is to catch more air when entering Mars thin atmosphere. Would that exit hypersonic flight high enough for a parachute to be useful? What G-load would that put on astronauts?
According to JPL, ADEPT would permit you to deploy a supersonic parachute at a high enough altitude on Mars to produce useful deceleration. However, the mass of the payloads we're talking about landing is so high that I think supersonic retro-propulsion is a better method for supersonic and subsonic deceleration and landing, even if it takes a little more propellant to do it. I like approach #3 in their infographics.
Peak G's for all proposed ADEPT control strategies is less than 4. ADEPT and HIAD shift the payload mass to "catch more air", as you put it.
The pages have just what we are looking for in ballistic angle and G force....
SpaceNut,
The document in your last post in this thread shows the peak deceleration force that the technology would likely produce if deployed at Venus with the specified area and loading parameters. How does that help us understand what the peak deceleration would be on Mars?
Let's have a look at the following document for more information about peak deceleration forces from actual Mars missions:
A micro capsule equipped with an inflatable heat shield with the same attitude control mechanism that IRVE uses would decrease rate of descent and the thin Martian atmosphere would decrease peak deceleration.
http://ntrs.nasa.gov/archive/nasa/casi. … 012170.pdf
The high deceleration forces imparted to the test articles has everything to do with deliberate use of plunging descents on suborbital flights to produce maximum heating and aerodynamic pressure on the shield for testing purposes.
http://solarsystem.nasa.gov/docs/p484.pdf
If I thought the micro capsule concept had no merit or posed significant technical challenges, I would not have proposed it.
It's a relatively simple solution to a complex problem. The primary disadvantage being that the micro capsule leaves nothing but a water ration and spare oxygen tank or two for the explorer to use to reach the habitat module (which is mobile and comes to him or her in my proposals).
To be clear, what I desire is a Mars EDL solution for humans that could be developed in 6 years time or less, at a cost of $3B or less. This is relatively inexpensive and therefore workable. All the realistic multi-person EDL solutions I've seen proposed aren't even in the same ballpark. Most involve a decade or more of development time and projected costs of around $10B or more. In other words, a human rated lander would be within NASA's budget using my proposal but a multi-person lander would take so long to develop or cost so much that it would most likely be cancelled.
If you disagree with my micro capsule proposal, then counter with a realistic multi-person lander with a development time of 6 years or less, costing $3B or less, that significantly improves the situation of our explorers if they happen to land off course. An all-propulsive EDL using Red Dragon would obviously function correctly, but it lands so little payload that the astronauts contend with the exact same surface survivability issues that astronauts landed with the micro capsule would have. Both solutions provide very little in the way of contingency supplies.
Apart from keeping the crew together, ensuring that they all die together if anything goes wrong (something that's obviously pretty high on the priority list of everyone but me), Red Dragon provides precious little advantage over my solution and would almost certainly cost more in terms of development and per unit purchase price. I like Red Dragon better than my proposal because I really want a cost effective multi-person lander, but it won't put the astronauts in any better a position if they land off course.
To complete the context of what I'm proposing, I would like two separate EDL solutions. I want to use a minimum mass and complexity solution like HIAD for humans and a somewhat more involved solution like ADEPT for heavy cargo.
If Red Dragon can be developed and properly tested for less money, then I would drop my proposal. My guess is that the weight and higher ballistic coefficient of the vehicle will make landings on Mars marginal at best.
