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When Robert Zubrin first presented his proposal to NASA in 1990, he called for an 85kW nuclear power unit. However, the guys working on the SP-100 nuclear reactor finished their work in 1992, they said reducing power output from 100 kW to 85 kW would not reduce reactor mass at all. So Zubrin may as well take the stock off-the-shelf design.
Zubrin's design included the "Mars Atmosphere Carbon Dioxide Freezer" (MACDOF). That would operate only at night, when Mars atmosphere was just a few degrees above the freezing temperature for dry ice. MACDOF uses freezer coils to accumulate dry ice, then at dawn seal the container and reverse the coils to sublimate the dry ice to gas. The phase transition in a sealed container self-pressurizes. A brilliant design that takes a lot less power than pumps. Catches: only operate the freezer at night, and it only collects CO2.
I've talked about a device the collect nitrogen and argon from Mars atmosphere for habitat air. And nitrogen as fertilizer for greenhouses. That requires pumps. But Robert Zubrin's design only produces propellant to return to Earth, so it only needs CO2.
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I just wonder what scale one would have to use in order to collect enough CO2 during a Martian night to collect a meaningful amount. Some pretty large coils in order to get more than just a few kilograms, I'd expect. These questions are essential in order to manufacture the amounts of CH4 to make the refueling system realistic.
Edit. After some additional thought, there would need to be a compressor running during the night in order to get enough CO2 available to condense as dry ice.
Last edited by Oldfart1939 (2017-02-07 16:16:40)
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I just wonder what scale one would have to use in order to collect enough CO2 during a Martian night to collect a meaningful amount. Some pretty large coils in order to get more than just a few kilograms, I'd expect. These questions are essential in order to manufacture the amounts of CH4 to make the refueling system realistic.
Edit. After some additional thought, there would need to be a compressor running during the night in order to get enough CO2 available to condense as dry ice.
No. For a system that freezes CO2 as dry ice, a compressor would have no benefit. Just ensure there's a continuous flow of Mars atmosphere over the freezer coils. Convection my be enough. Since the goal is to freeze dry ice, which is 95+% of the atmosphere of Mars, would depleting Mars atmosphere of CO2 be a concern? Would an open top and sealed bottom hold cold atmosphere in, making better use of cold? As CO2 is frozen out, pressure will drop which will draw fresh atmosphere in the top. Or perhaps some leakage of Mars atmosphere through the bottom, just to ensure atmosphere within the container doesn't accumulate gasses other than CO2? With optimized flow to contain cold as much possible, while ensuring fresh CO2 is drawn in the top?
Again, this is more efficient than any sort of compressor because Mars atmosphere at night is so close to the freezing temperature for dry ice.
::Edit:: Mars Direct expected this system would take a few months to accumulate enough propellant to return to Earth. But it would be finished several months before astronauts depart Earth for Mars. So radio signals would tell mission control on Earth that ERV propellant tanks are full, ready to return, before astronauts leave home.
Last edited by RobertDyck (2017-02-07 16:34:03)
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Red Dragon appears capable of soft-landing 1-2, perhaps just possibly 3, metric tons on Mars (unproven yet). NASA-JPL is limited to 1 ton, and only with Rube Goldberg designs if over half a ton (proven already).
So how much does the nuke power plant and all this gear really weigh, for making several hundred tons (maybe 1000+, nobody knows the answer to that, either) of propellant in the space of only several months to a year or two? That is the answer I seem unable to get from anyone.
Further, it totally ignores the robotics required to set all this stuff up and get it working in the first place. Since it must work before a crew can go.
I say again: send the first crew with everything they need, including a way home. Let them spend their year on Mars setting this propellant factory up and getting it working right.
It would really help if we already knew "for sure" which site would work with the gear we send, wouldn't it? I have a real ethical problem with betting lives on inference with remote sensing. There is no truth like ground truth.
GW
Last edited by GW Johnson (2017-02-07 17:35:03)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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What's really needed by the chemists in this group is an estimate of the fuel and oxidizer required for the return to Earth flight. So...do we need to accumulate 100 kg, 200 kg, or ...500 kg of solid CO2 per night to make this work? Numbers! The concept is truly elegant, but the devil is in the details.
Here's the chemistry for both needed products:
2 CO2 ---------------------------> 2 CO + O2 At 100% efficiency, we need 88 kg of CO2 to produce 32 kg of O2.
(catalyst + heat)
CO2 +4 H2 ----------------------> CH4 +2 H2O At 100% efficiency, we need 44 kg CO2 and 8 kg H2 to produce 16 kg CH4 and 36 kg
(catalyst + heat to initiate) H2O.
For combustion at the stoichiometric ratio, we need 64 kg of O2 to completely consume 16 kg of CH4.
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GW: In the thread Light weight nuclear reactor, updating Mars Direct I proposed a few small changes to Mars Direct. The premise of Mars Direct was to bring hydrogen from Earth, since the first mission won't know how reliable ground ice is, how to find it, how to harvest it, how to process it. The only robotics necessary are to move the nuclear reactor to a safe distance from the ERV. Robert Zubrin and David Baker's plan in 1990 was a small robotic truck that would drop the reactor in the bottom of a crater, with a power cable leading back to the ERV. Chose a crater deep enough that there is no line of sight from the reactor to ERV, so no line for radiation. That means regolith of the sides of the crater would be shielding from reactor radiation. His idea was the robotic truck would drop the reactor, then back away before the reactor starts. The truck could potentially be used by the crew.
My update was to propose using mobility parts from the Curiosity rover. That is new parts identical to those for Curiosity: wheels, suspension arms, drive motors, power electronics, navigation computer, navigation software, and "nav-cam". Bolt these parts directly to the reactor, so no separate rover body, the reactor is the body. No RTG, because it will have the full-size reactor. This rover would drive itself to the bottom of a crater, and permanently park itself there. I suppose the rover will not be able to use reactor power, because it will operate before the reactor is turned on. But the ERV will have to land without the reactor, so the power cable could provide power from the ERV to the rover. Once the reactor is turned on, power will flow in the opposite direction: from reactor to ERV.
In that thread I gave detail numbers about the SAFE-400 nuclear reactor. Again, a reactor designed by the exact same guys that developed SP-100. It provides exactly the same power (100kWe), and operates in the same environment (space). SP-100 was completed in 1992, SAFE-400 was completed in 2007. SAFE-400 is newer and lighter.
There. That's the robotics.
As for which site? I proposed starting the permanent base with the first human mission. That requires verifying a source of water exists first. So yes, I have proposed an unmanned rover the size of Spirit or Opportunity with a multi-segment drill like CanaDrill to verify ground ice is there. But again, the first mission would bring hydrogen so not dependant on it.
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So--we will have the ERV on the surface of Mars for 18 months before the first crew arrives, basing the Mars trip on the most energy conservative flight path. That means ~540 days (and nights) available for O2 and CH4 preparation. Oxygen is needed in a 4:1 mass ratio to methane. As a small "plant scale" process, it would seem feasible to me for ~320 Kg of O2 to be manufactured a day, and easily make 80 Kg of Methane. In the 540 days available before the next Hohmann transfer window, the system could accumulate 43,200 Kg of CH4 and 172,800 Kg of O2. That would seem to be "enough" to boost to escape velocity , make trajectory corrections, and possibly do some retropropulsive braking. This would require the capture and utilization of 1100 kg of CO2 nightly (or nightly and daily). What really needs occur is sending two completely independent SAFE-400 reactors, each with it's own plant; one for O2 and the second for CH4. My concern now is collecting enough atmospheric CO2 in the system.
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Oldfart1939, have you read "The Case for Mars"? Have you read the Mars Direct mission plan? When I suggested some modifications at a presentation I made at the 2002 convention, members of the Mars Society were extremely critical. They didn't want to hear any changes. But NASA had some serious concerns, I've tried to address those concerns as well as make the plan sustainable. And since the object of Mars Direct was to keep launch mass to a minimum, there was one point I made in 2002 which would reduce launch mass further. It was based on a principle of Apollo, something NASA reluctantly accepted in late 1961 / early 1962. Since I've tried to update it as new technology comes out.
The reason I ask is Mars Direct would use a minimum launch mass trajectory for the ERV, so 8.5 month transit. But for crew it would use an "express trajectory", which takes 10% more propellant or correspondingly less launch mass, so a 6 month (180 day) transit. The ERV would be launched in one launch opportunity, then 26 months later the hab would be launched with crew. As a 3rd tier backup, a second ERV would be launched a couple weeks after the hab with crew, but the second ERV would also use an 8.5 month transit. So it would arrive 3 months after crew. If the crew arrives at the site of the first ERV and everything is Ok, then the second ERV would land a the second mission site, starting that mission.
Of course I've argued that since Mars Direct could have launched an unmanned test of all equipment in 1997, and the first manned mission in 1999. It didn't, we wasted 20 years on robotic probes: orbiters, landers, rovers. Since we did all that exploration with robotic equipment, duplicating the exploration phase with humans would be redundant, wasteful. So chose a site to start the base. That means we need 3 more robotic missions: (1) an orbiter as technology demonstrator for aerocapture, (2) a lander as technology demonstrator for ISPP, (3) a rover to prove water ice is present at the site.
Also, Robert Zubrin argued for 500 days on Mars surface. I point out that means the second crew mission will launch a couple months before the first mission arrives back on Earth. That creates a few problems; one is the need for mission control to monitor two missions in space at the same time. So I argue to reduce the science mission to 425 days on Mars surface. That would take just a touch more propellant (or lower hab mass) due to slightly late launch, and the ERV would require a touch more propellant due to early departure. But I think it's worth it. Besides, if crew launches up to a month late, that will require less propellant, not more. They would arrive on Earth after the scheduled launch for the second crew, but less propellant would make it easier/lower-risk.
But getting back to CO2. If the first ERV is launched at the optimal launch time, and takes 8.5 months. And assuming Earth and Mars align every 26 months (varies a bit with each year, depending on planetary orbits). And assuming the crew launches 34 days after the optimal launch time, and takes 180 day transit. That means crew will be ready for launch from Earth 26 - 8.5 + 1 = 18.5 months after the ERV lands on Mars. Oh! So your estimate is 18 months before the first crew arrives is bang on. Uhhh...Ok.
Robert Zubrin's ISPP would use a Sabatier to combine H2 from Earth with CO2 from dry ice collected from Mars atmosphere. That would produce CH4 and H2O. Then run H2O through an electrolysis tank, recycle H2, and chill O2 to liquid to fill the oxidizer tank. That would not produce enough O2 for the correct engine mix ratio, a little extra O2 is required. But the water electrolysis tank will provide most of the O2. The rest will come from direct CO2 electrolysis. That is take CO2, heat to 900°C to 950°C in a thin wall ceramic tube. Electrolysis across the wall of the tube will pull O2 out of the tube, while CO2 and CO will remain inside. It converts 80% of CO2 to CO. Then dump the CO2/CO mix into the atmosphere of Mars, start again with a fresh batch of CO2. Between heat and electrolysis this takes 3 times as much power (watt-hours) as water electrolysis for the same unit mass of O2, but works with pure CO2. So this produces O2 to balance combustion. It was expected that the CH4 tank would be filled in months, but long before the 18 month deadline, so plenty of time to use reactor power to top-up the O2 tank using direct CO2 electrolysis. That's why one reactor for one ERV.
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The mav only is fueled to get it back to orbit to rendevous with the orbiting erv which is fully fueled.
That said when we looked at the red dragon we were not able to get back to orbit. That said we need to land a 2 stage rocket that has an empty first stage upon landing and an empty second stage to allow for refueling of both stages to get to orbit.
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Have I read The Case for Mars? Uhhh...only about 4 or 5 times. I'm using a lot of information provided in Zubrin's second book, Entering Space. I've been involved with Physical Chemistry most of my professional career and have lots of Industrial Scale and Pilot Plant experience. My concern is the tendency to be overly optimistic about the efficiency of robotic operation of a very remote manufacturing facility--exactly what the Sabatier Reaction plant will be. Ditto the Oxygen generation reactor. Yes, I'm aware that electrolysis of H2O requires less energy than direct disproportionation of CO2, but that's an energy issue. There will not be enough H2O available from the initial H2 supply brought from Earth. In a chemical plant operation scheme, there would be 2 independent reactors always working in parallel; one for direct production of O2 from CO2, in parallel with the Sabatier reactor.
Regards your comments above about the stay time on the Martian surface; another argument for that approach involves the consumables; food and water. I think we've got the O2 issues covered. Food and consumables for a 425 day stay would drastically lower the supply logistics tail. I've been figuring on a optimal 7 person crew, but initially will more likely be a 5 person mission. All at the 170 Earth pound weight of FAA average passengers and my 2 % body weight food allowance per day. This means food for Mars residents is now only 7225 pounds of food.
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The mav only is fueled to get it back to orbit to rendevous with the orbiting erv which is fully fueled.
That said when we looked at the red dragon we were not able to get back to orbit. That said we need to land a 2 stage rocket that has an empty first stage upon landing and an empty second stage to allow for refueling of both stages to get to orbit.
The 1961 issue I alluded to is NASA intended to land the Apollo Command Module on the surface of the Moon. The lead engineer for the manufacturer of the Lunar Module argued strenuously for Lunar Orbit Rendezvous. You could argue he tried to sell his company's Lunar Module, but he was right. Direct Launch meant the CSM would be so big that Saturn V could not launch it. They would have required a form of NOVA. Similarly I argue to leave the Earth Return Vehicle in Mars orbit, and use a Mars Ascent Vehicle to reach it. Same as Apollo CSM/LM. However, land the hab just like Mars Direct. But one of the brilliant ideas of Mars Direct is use of ISPP. To ensure all return propellant is ISPP, use the MAV as the TEI stage. So the MAV would have minimal crew cabin, perhaps even non-pressurized with crew riding in spacesuits, and the MAV would have over-size propellant tanks. Once inserted into Trans-Earth trajectory, the spent MAV could be used as counterweight for spin gravity just like the hab during transit to Mars.
I also argue for aerocapture into Mars orbit, and aerocapture into Earth orbit. In Earth orbit, aerobrake down to ISS orbit, then rendezvous and dock with ISS. This allows the Interplanetary Transit Vehicle to be reused. But all propulsion stages are expended. It also means the ITV will have all food and life support supplies for transit both to and from Mars. And the surface hab till be docked to the ITV during transit to Mars, which will have food and supplies for the surface stay. So if free return is necessary, all those supplies will be available to crew. With Mars Direct, supplies for return to Earth are in the ERV, so not available in case of free return.
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Here is a paper on gas separation. MACDOF is one of the technologies studied. MACDOF was developed by Pioneer Astronautix, Robert Zubrin's company, with Robert Zubrin himself as the lead for this project. Anthony Muscatello was one of Zubrin's employees, but moved on to work directly for NASA. Anthony is the lead for this paper. This paper also covers other separation technologies, such as separating CH4 from feed stock and intermediates of the Sabatier process, and others. Available from NASA's technical report server, received October 3, 2011.
Evaluation of Mars CO2 Capture and Gas Separation Technologies
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Regards your comments above about the stay time on the Martian surface; another argument for that approach involves the consumables; food and water. I think we've got the O2 issues covered. Food and consumables for a 425 day stay would drastically lower the supply logistics tail. I've been figuring on a optimal 7 person crew, but initially will more likely be a 5 person mission. All at the 170 Earth pound weight of FAA average passengers and my 2 % body weight food allowance per day. This means food for Mars residents is now only 7225 pounds of food.
Ok. Is that whole food, or freeze-dried? In Robert Zubrin's book, he argued for whole food based on life support technology available in 1989 & 1990. He said NASA wanted 95% recycling efficiency, but Dr. Zubrin argued if we waited for that it would be the 21st century before we're ready to go. But we're in the 21st century now. NASA reports water recycling efficiency on ISS is now 93%. So I argue freeze-dried food like that used on Shuttle missions could dramatically reduce food mass. Have you taken that into account?
We once heard a supplier for NASA claim space food will not last long enough for a Mars mission. Sounds like they want funding. A local camping store has freeze dried food, the one with most shelf space is Mountain House. Their food comes in paper packages lined with a thin coating of aluminum, but essentially the same thing as Shuttle food. The plastic of Shuttle food should provide just as effective a barrier to moisture and oxygen. If not, I could provide suggestions for how to make it so. Technology from pharmaceutical packaging. The point is Mountain House taste tested their own product. They report no difference in taste between fresh food and 12 year old packages. And they found packages 30 years old are still "quite tasty". Notice they say it doesn't taste the same, just that it's "quite tasty". So definitely long enough for a 26 month mission. That camping supply website is here: Mountain House
I had also counted on just 4 crew members. For the initial science missions. Keep it small. My bias is partially due to the same reason as Dr. Zubrin's: NASA has been saying 4 crew to Mars since 1965. An Apollo capsule could carry 3 crew to Lunar orbit and back, along with food and life support supplies. And enough space for lunar samples once food and supplies for transit to the Moon, and Lunar stay had been consumed. A rescue Apollo was built for Skylab. They didn't need food or extra lithium hydroxide canisters, so storage space behind the seats could hold 2 more seats. So the Apollo Command Module could carry 5 crew back from Skylab. I believe it could deliver 5 crew to Skylab, but was never used for that. NASA did studies for Mars in 1965 and 1968, but got serious in 1970. After Apollo 11 landed, the Soviet Union seriously considered trumping America's achievement by going straight to Mars. When spy agencies told NASA this, they got serious. They announced to the public that they developed PICA heat shield, capable of protecting a Command Module returning from Mars. In recent years we learned the US military had developed PICA; NASA had just adopted it for Mars. The version of PICA in 1970 was 3 times the mass of the AVCOAT heat shield used by Apollo to return from the Moon, but was able to do the job. The 1965 study tried to use propulsion to slow sufficiently that the AVCOAT heat shield could enter Earth's atmosphere, but every attempted design was impractical. They found propellant and thrusters would weight much more than a PICA heat shield. With the PICA heat shield, there was only enough weight allowance for 4 crew members. And all food and extra lithium hydroxide canisters would have to come from a deep space habitat of some sort. So that's where we got "4 crew for Mars".
However, in his book Robert Zubrin argued for 2 exploration teams: 1 scientist & 1 engineer to fix stuff. Sounds good to me.
::Edit:: That sounds arrogant. Dr. Zubrin has a Ph.D. in nuclear engineering, and Master degree in aerospace engineering. And he worked for Martin-Marietta, and has his own aerospace company. I'm just a wanna-be.
Last edited by RobertDyck (2017-02-08 00:26:30)
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Robert-
I've always argued for a minimum 5 person mission, preferably 7, based on my Triads argument. Any extra habitat mission must always have 3 bodies involved. Yeah, I know--we're never going to fall down a steep slope and break a leg or such, but if we do--2 "rescuers" for the "victim." With all the Hi Tech electronics around, there's also a need for an electronics specialist on the mission. An odd number of crew makes decisions easier. I've been on mountaineering expeditions where the decision making gets tense with an even number--especially if there is no designated "mission commander." Standoffs have occurred in the damndest places--friends went on mountaineering trips and came back enemies.
With regard to foods, Mountain House freeze dried stuff is OK, but it IS pretty thirsty. I'm stating that whole foods OR freeze dried and water combined must equal 2% of body weight to avoid losing weight under stressful activities. Whole foods have a psychological edge, being "comfort foods." They also provide some of the radiation shielding discussed by Zubrin in his books, since they contain masses of water. The freeze dried Beef Stroganoff and Turkey Tetrazinni packages will not provide the same shielding as long shelf life vacuum packed hydrated foods. A lot of food these days is packaged in plastic containers and are irradiated to preserve the foods. Our plant engineer ( a Chem Engineer) quit the company where I was last working and went to work at Mountain House, so yes, I'm familiar with their operations and products. What ever we do---NO MREs! They are OK for short term use and don't taste too bad; they are by design, low bulk and are pretty constipating.
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But recycled water means you don't have to carry enough for all that freeze dried stuff. Just enough for the current meal, plus water in-process, and a certain reserve to replenish losses. Robert Zubrin's design is fine, but needs updating. Life support equipment is heavier than he estimated, and the SAFE-400 reactor is lighter than the SP-100 he planned for. I've suggested storing reserve water in a bladder in the walls of the radiation shelter. Just thick enough for effective radiation shielding, so the bladder covers as much wall area as possible. And a bladder so it can operate in zero-G. No air in the bladder, instead a soft bladder that collapses as water is sucked out. But rather than increase weight, instead reduce weight as much as possible. Remember we still have to reduce number of launches. We can't take so many launches that assembly in Earth orbit takes as long as ISS took. Just for one mission. That means it will be cancelled before it ever launches. And certainly no follow-up missions. So keep it simple, keep it small.
Current habitat design includes a temporary radiation shelter than can be erected quickly. Rather than do that, why not have a central storage closet that acts as the shelter? Instead of storing plastic sheet walls for radiation shielding, make the walls of the closet permanently out of that stuff. So just remove the brooms or anything not in cupboards, then stand in the closet.
They're looking at polyethylene and polypropylene polymers for radiation shielding. Water is H2O, these plastics are (H2C)n. Same hydrogen content, and the carbon is actually lower atomic mass. Radiation will cause cross-bonding and polymer scission, water won't do that but water can't form solid walls.
Are 2 rescuers necessary for Mars? I'm thinking the buddy system. I can lift over 100 pounds without too much trouble. When I was in my early 30s, my weight used to fluctuate between 165 and 185 pounds, depending whether I was employed. Posted tables in a gym, based on military data, states a healthy weight for someone of my height is 185. I'm a bit overweight now. Had a contract job, a couple co-workers were overweight, went to an all-you-can-eat buffet every day. My weight ballooned to 205. I haven't been able to get rid of it. But Mars has 38% gravity. Apollo A7L-B suits weighed 212 pounds for EVA including PLSS. An MCP suit will weight substantially less. One advantage is an MCP suit has no liquid cooling system, just a bottle of drinking water. With ortho-fabric instead of beta-fabric. Even if a suit weighs 140 pounds, with 185 pound man, total weight 325 pounds. In 38% gravity that will weigh 123.5 pounds. With enough exercise to lose my 20 pounds of fat, I could carry the weight of my own suit and lift that. In Mars gravity I could carry a fellow crew member to the rover.
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Depending on the circumstances and range of motion required, a healthy astronaut may be capable of carrying an immobilized but not otherwise seriously injured astronaut for short distances. Increasing suit masses, volumes, or distances to cover make it increasing likely that a rescue attempt could injure or kill both astronauts. Carrying people isn't like carrying a heavy pack. Every time you take a step, the load shifts. You also need your hands free to prevent falls, so there must be a way to secure them to your body.
I don't think it's reasonable to ask someone to carry someone else twice their size, even in .38g. We're training astronauts, not firemen. I value their love for each other and their ability to think critically to problem solve more than brute strength. However, getting younger recruits would certainly help.
Maybe some sort of exoskeleton or motorized stretcher is required.
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Robert-
There is no doubt the Mars Direct plan needs some updating. As you point out, the Nuclear Reactor has lost weight. As for the food supply, there needs to be some mixture of freeze dry and fresh foods, simply for diet variety and mental health of the astronauts. Yes, I too was in pretty damned good shape when I was younger, and could fireman's carry a average weight person a decent distance. However, there are some injuries which require litter transportation--back and neck injuries. I'm standing fast with my triads. The other option of a triad is having one person stay with the injured while the 3rd arranges for additional backup help. Murphy's Law always applies to emergency situations, and Murphy was an optimist. By the way, my Army training was as a combat medic. The other argument for whole foods as opposed to freeze dry is the water content; cannot bring TOO MUCH water along.
Yes we need to keep the mission lightweight and simple, but it also MUST SUCCEED! If having a 5th crew member increases the odds of success significantly, we'd better make things a little bigger. My mission model always had overlap of crewed missions, such that at one point there would be 2 crews. This would require a larger Hab, but that will have to be in the planning. My thoughts were centered around 2 Triads plus a mission commander. a total of 7 astronauts per crew. Projecting that forward, construction of a decent base is going to require a lot of manpower, if only to avoid exhaustion of the crew members. Our hypothetical models are prone to failure due to overestimating the capacity to get tasks finished. There has to be adequate down time for rest and some sort of recreation. Going on a 24/7 schedule will destroy morale.
Your comments about using polyethylene and polypropylene as radiation shielding are right on the mark; these plastics are quite strong and do shield radiation from Solar Flares and van Allen radiation very effectively. Polymer sheeting and preformed injection molded components should definitely be incorporated into the buildable Hab structure, especially doors, airlock structure, roof components, etc. I'm strongly in favor of using regolith to partially bury the Hab into a hillside; that would provide shelter against Solar Flares, and reduce heat losses.
Regardless of which crew size model we work with, food will remain an issue. How much? What type? How much emergency food planning? I'm strongly in favor of a full mission reserve already on Mars before we arrive. Maybe solar activity during a Hohmann window prohibits a manned mission from taking place? We cannot allow a crew to starve to death ala Mark Watney in The Martian.
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We're training astronauts, not firemen. ... getting younger recruits would certainly help. Maybe some sort of exoskeleton or motorized stretcher is required.
I argue instead for lighter suits. I have a document by Dr. Paul Webb written in 2011. He stated an MCP suit weights 1/4 the weight of a gas-pressurized suit with mechanical joints. He also estimates the weight of a PLSS to be 85 pounds. An A7L-B suit used for Apollo 15-17 weighed 78 pounds, not including PLSS. So that works out to 19.5 pound suit plus 85 pound PLSS = 104.5 pound mass. That's mass, then adjust for gravity. For our European members, or Canadian members born after Canada went metric in the mid-1970s, that's 47.4kg.
Long distance from base would be via rover. An open rover would carry a pressure tent. I've argued for a dome pressure tent with an air mattress floor. Not just for comfort, but thermal insulation from cold ground. With multiple layers of aluminized polymer (Mylar or fluoropolymer?) suspended by threads so the layers are separated when the air mattress is inflated. Life support in the dome tent would be a spacesuit PLSS, just with an oxygen bottle to inflate. The tent could be used for suit repair, resting if caught long distance from the hab, or medical issues. The tent would also be aluminized to stop radiant heat loss, with one or more transparent windows, and an aluminized tent flap on the inside that can close over the window. Heat gain may be more of an issue than heat loss, so I suggested air channels form the top layer inside the air mattress to the bottom layer, and a fan the size of a computer case fan to circulate air between. A thermostat would control the fan. Run by a battery in the PLSS.
Rather than a motorized stretcher, use a rover. That's motorized.
Last edited by RobertDyck (2017-02-08 17:00:40)
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Lighter suits...yes! But before you think about picking up and carrying someone for even a short distance, consider the totality of the injuries. This assumes that the injury occurred on a nice flat and easily accessed spot. More likely, it will be a fall down a steep slope caused by bad footing; assume one thing: it will be in the worst possible place for a casualty evacuation. Remember: Murphy was an optimist. I learned every conceivable method of carrying a person injured at Ft. Sam Houston, Brooke Army Medical Center. More than likely it wont be a nice easily splinted arm or lower leg, and will probably have back or neck complications. By planning for the worst possible scenario makes us prepared for whatever comes along. A Stokes-type litter could be hauled up a steep slope by a winch on the rover, but putting a seriously injured person IN the litter is the problem, and one person cannot do it. Every person I ever worked on was thinking "well, I'M not going to get hurt...." Not trying to rain on anyone's parade here, Robert, but even careful people get hurt due to unanticipated circumstances. My crew plan of 7: 1 team leader; 2 Triad leaders and two triads. This has a definite pyramid structure, but ensures cohesive performance at all times.
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Rob,
I agree 100% with your argument for lighter suits. The current models are liabilities in a planetary environment with significant gravity.
Just like Oldfart1939, my thought process on this was that falls that would typically produce serious injuries are more likely to happen in steep terrain where a rover may have stability issues. It might not be possible to get the rover close enough to the injured astronaut. Maybe a kevlar fabric stretcher with composite stiffeners and a lanyard loop for connecting it to the rover's winch is the way to go. If the astronaut can lift the opposite end of the stretcher with a handle and activate some sort of remote to slowly winch the astronaut towards the rover, then perhaps the rescuer can use their body weight in a similar manner to a belay but with your feet on the ground. The stretcher is not dragged over the terrain as a result because the rescuer is using their body weight and the winch to suspend the stretcher in the air. It obviously wouldn't work over all terrain, but if it was just a steep hill then you can effect a rescue without the need for another person. There are lifting straps for moving furniture using this principle. It's known commercially as the Forearm Forklift or the Shoulder Dolly.
Oldfart1939,
If you had a long plastic needle to feed the straps under the patient and then used the composite poles to make the stretcher rigid, would that enable one person to load a casualty onto a stretcher without substantially moving the patient? I was thinking that relatively short composite poles and a series of adjustable kevlar straps could enable an astronaut to make a stretcher. It wouldn't take up much space or weigh too much. The device would basically be sort of like the ThermaRest LuxuryLite, but with straps instead of a solid piece of material.
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One cannot underestimate the potential for serious injuries in unknown terrain, and one rescuer is totally inadequate. Period. A serious injury situation on Mars has one real potential: things will get worse before they get better. Too many of the planners for missions do NOT have adequate experience on the ground to appreciate this. I'm not going on the movies, either; injury accident scenarios tend to evolve into a cascade of head to tail events making things nearly overwhelming. The smallest fully functional group devolves down to a group of 3; in a bad situation, one person of the team rest or sleeps; one other member does essential tasks, such as food preparation or equipment maintenance; the 3rd remains "on alert" for changing condition, or maintaining communications with a higher headquarters.
This brings to mind something for the spacesuit design. presence of a special patch with an auto-sealing injection compound, just in case an injection of morphine, or other lifesaving medication needs to be administered.
I'm making these observations based on my 3 years of wearing Army Green as a medic in a variety of situations. I was also deeply involved with the Rocky Mountain Rescue Group based on the University of Colorado Campus in Boulder after my military experience. Believe me, I know about bringing someone down a near vertical rock face or on a steep scree slope. T'aint easy.
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If you have an MCP suit, special patches are unnecessary. The garment itself is porous and unpressurized, just tight. Stick a needle through it anywhere you want.
Small tears up to around a cm in size you can ignore entirely without much consequence. Something like duct tape holds it until you go inside and sew it up. Bigger holes, you patch with tape and go immediately inside.
Other experiments confirm: up to about a hand in size, you can completely depressurize for 20-30 minutes before swelling starts. It reverses some hour or so after repressurization. Times decrease and seriousness increases as the size of the depressurized body part increases.
The limit is whole body exposure: about 2 minutes max. The victim will be unconscious, but is resuscitatable. Such was actually done with a human victim in a vacuum chamber experiment that went wrong, in Houston, about 1965 or so.
GW
Last edited by GW Johnson (2017-02-10 16:10:59)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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You're making it sound like the first Mars colonists are going to go on some Wild West adventure. Of course they won't. If they do any major exploring it will be in a pressurised vehicle. They won't be exposed to anything. There may be some need for space-suited activities on the surface in the early stages but these will be few and far between and will be strictly controlled in my opinion.
As the colony grows, yes there will be accidents, but there are accidents on Earth and we live with it. But the first few missions will be strictly controlled to ensure that the missions are not compromised.
One cannot underestimate the potential for serious injuries in unknown terrain, and one rescuer is totally inadequate. Period. A serious injury situation on Mars has one real potential: things will get worse before they get better. Too many of the planners for missions do NOT have adequate experience on the ground to appreciate this. I'm not going on the movies, either; injury accident scenarios tend to evolve into a cascade of head to tail events making things nearly overwhelming. The smallest fully functional group devolves down to a group of 3; in a bad situation, one person of the team rest or sleeps; one other member does essential tasks, such as food preparation or equipment maintenance; the 3rd remains "on alert" for changing condition, or maintaining communications with a higher headquarters.
This brings to mind something for the spacesuit design. presence of a special patch with an auto-sealing injection compound, just in case an injection of morphine, or other lifesaving medication needs to be administered.
I'm making these observations based on my 3 years of wearing Army Green as a medic in a variety of situations. I was also deeply involved with the Rocky Mountain Rescue Group based on the University of Colorado Campus in Boulder after my military experience. Believe me, I know about bringing someone down a near vertical rock face or on a steep scree slope. T'aint easy.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis:
It's like the wild west, just worse. You cannot operate a drill rig from inside some pressurized rover. You do it standing right alongside the hardware, ready to intervene when the equipment screws up. Which we can be 100% sure that it will screw up.
There's no hope of recovering from an accident like a fall off a steep slope except what you can do for yourself. We can learn a lot from Earthly EMT's about how to do exactly that. Might be harder in a pressure suit, but I'll be damned if I wouldn't try. Basic human ethics.
I think there are good reasons to take both kinds of spacesuits on the voyage. It is easier and faster to don a full pressure suit. But only an MCP suit could possibly give you the dexterity you need to properly explore on a planetary surface. We already saw that effect as a negative, with full pressure suits on the moon.
Paul Webb's MCP suit was intended for use (with outerwear) on the moon, but could not be made ready in time.
GW
Last edited by GW Johnson (2017-02-10 18:27:29)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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When one starts "wargaming" various scenarios, it's simply inevitable that something gets overlooked. The Rover should have a powerful winch with say--100 meters of light aircraft cable on the spool. The suits should have attachment D-rings integral to them, and in a variety of body locations. Then--the rover should have a wireless remote drive controller in order to command the rover to start a winch and enable a bod haul up and out of a bad scenario. The Rover should actually have 2 winches; on at the front and one at the rear; this could, in principle, drag a stuck rover out of a sand trap. Needless to say, the proposed Rover and crews will need some serious desert training time and doing some injured crewperson evacuations.
I'm not trying to be a Negative Norbert here, just a realist. Just make plans and train for the worst possible scenario and in reality it will probably be even worse. At this juncture you ARE getting some input from an ex military version of an EMT.
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