New idea for Mechanical CounterPressure suit

GW Johnson · 2015-08-07 17:18:42

NASA's 0.3 bar is overkill for life support. They do this because of tradition, nothing more compelling. Webb used about 0.25 bar. My data show that 0.15-to-0.20 bar is quite feasible. Those are all suit pressures in very simple pure oxygen breathing gas. Webb's test subjects exercised very strenuously with oxygen supplies like that. Overkill is quite unnecessary.

Long-term habitat atmospheres ought to be "real" air at a fair fraction of 1 bar, because that is what we evolved to breathe. That simply avoids all questions and potential problems. Why incur them? MCP suit donning times in about 0.3 to 0.5 bar pure O2 provide the N2 blowoff time to decompress the person to suit conditions. What could be simpler?

GW

RobertDyck · 2015-08-07 20:01:29

Apollo A7L suit was used for Apollo 7-14. A7LB was used for Apollo 15-17. The document by Paul Webb (submitted for publication December 1966) stated the pressure of the A7L suit was 3.3 psi because that would allow for 10% decompression and still leave 3.0 psi pure oxygen. Partial pressure O2 at sea level (KSC launch site) is 3.0 psi. But later documents I found on the A7L suit says they increased the pressure 3.5 psi by 1963, and then to 3.7 psi by 1964.

The Case for Mars states air for Apollo and Skylab was 5.0 psi total, with 60% O2 / 40% N2. That provides 3.0 psi partial pressure O2, which again is the same partial pressure as the KSC launch site. However, documents cite "nominal" Skylab air as 5.0 psi total with 70% O2 / 30% N2, and actual inspired air had a little less oxygen, a little more water vapour and CO2.

I have argued for lower pressure for Mars. I suggested habitat 2.7 psi partial pressure O2. Boulder, Co, has 2.53 psi partial pressure O2, so next time you're at a Mars Society convention in Boulder, realize the O2 you're breathing is less than I recommend for the Mars hab. And a mixture of N2 and Ar for diluent gas. Human lungs become sensitive to humidity at very low pressure. And human lungs require more partial pressure O2 when total pressure is very low. The limit is 2.5 psi pure O2, but the subject must go through high altitude training, and humidity must be very high to endure this safely. Following the principle of allowing 10% suit pressure loss and still maintain the same partial pressure O2 as the spacecraft cabin, this mixture would allow suit pressure of 3.0 psi pure O2 with zero pre-breathe time.

For zero pre-breathe, there is a calculation. Partial pressure N2 of the higher pressure environment must be no more than 1.2 times total pressure of the lower pressure environment. So if total suit pressure is 3.0 psi, then the Hab/spacecraft must have no more than 3.6 psi partial pressure N2. There's a ratio for Ar as well, but I don't know that number. My guess was to keep N2:Ar ratio the same as Mars ambient, which results in low Ar pressure. It also makes production of diluent gas easy. Just take Mars atmosphere, decompose CO with O2 over a platinum or palladium or rhodium catalyst to produce CO2, then remove most of the CO2. Mars atmosphere has more O2 than CO, so you don't need to add O2 to do this.

One interesting feature of atmosphere harvesting is self-pressurization. Robert Zubrin's "Mars Atmosphere Carbon Dioxide Freezer" would operate at night because temperature was so low it only takes a few degrees to freeze out dry ice. Then seal the canister and heat to convert into CO2 gas. The phase change will self-pressurize. Your sorbent to collect O2 from Mars atmosphere might have the same property. Thermal release of O2 might self-pressurize. This is important because pumps to go from 7 mbar to Habitat pressure will consume a lot of power. My design to produce diluent gas required pressurizing to 10 bar while freezing out CO2. Going from 7 mbar to 10 bar requires a LOT of power. That's the catch. If you can avoid that, you may have something good.

GW Johnson · 2015-08-08 12:53:11

Hi RobertDyck:

I'm guessing that if we went with MCP, there's no purpose for a 10% leak allowance. Nothing can leak but the helmet, and if that leaks, it's broken, and you're dead anyway. Might as well go with the minimum.

GW

RGClark · 2015-08-08 12:57:15

RobertDyck wrote:

The Popular Science article links to a science paper published by Chemical Science. here Quoting that paper...
Oxygen desorption for the parent [{(bpbp)Co2III(O2)}2(bdc)]4+, crystallized with four different counteranions, was measured by heating up to 160 °C at 5° min-1 under a steady flow of N2 gas.
...
At approximately 100 °C the nitrate salt has lost both O2 molecules, whereas the PF6- salt is completely deoxygenated first at 160 °C.
Figure 2 of that paper shows thermal cycling from +30°C to +140°C. How much energy for that thermal cycling? What is the specific heat for this material? What mass of material per unit mass of oxygen? Then there's energy efficiency: is the material compatible with radio frequency heating, like a microwave oven? If you use electro-resistive heating, there's thermal mass to the heating element and container.

Thanks for that. It would definitely take more power to effect the oxygen release than to collect the air through a fan.

Bob Clark

RGClark · 2015-08-08 20:04:23

RobertDyck wrote:

...
One interesting feature of atmosphere harvesting is self-pressurization. Robert Zubrin's "Mars Atmosphere Carbon Dioxide Freezer" would operate at night because temperature was so low it only takes a few degrees to freeze out dry ice. Then seal the canister and heat to convert into CO2 gas. The phase change will self-pressurize. Your sorbent to collect O2 from Mars atmosphere might have the same property. Thermal release of O2 might self-pressurize. This is important because pumps to go from 7 mbar to Habitat pressure will consume a lot of power. My design to produce diluent gas required pressurizing to 10 bar while freezing out CO2. Going from 7 mbar to 10 bar requires a LOT of power. That's the catch. If you can avoid that, you may have something good.

I ran some numbers on another forum about replacing scuba tanks. It should be doable technically to do electrolysis to separate the oxygen out of water at a much lighter weight than a scuba tank, which run about 15 kilos for about an hour's worth of breathing time underwater.

To chemically separate the hydrogen and oxygen in water takes about 16 million joules of energy per kilo of water. This is at 100% efficiency. I don't know what the best efficiency actually is now but we'll see the amount that can done be using batteries is so high that likely it can be better than using scuba tanks for the same weight.

The ratio of oxygen to hydrogen in water by mass is 8 to 1. So using 16 megajoules of energy you get 8/9 of a kilo of oxygen. This means 16*(9/8) = 18 megajoules gives 1 kg of oxygen. Using as an estimate that oxygen usage for astronauts would be similar to scuba divers we need .5 kg of O2 for 7 hours underwater, or 1 kg of O2 for 14 hours.

Now for the weight of batteries. See this table for a list of energy densities per weight:

https://en.wikipedia.org/wiki/Energy_de … materialsy

The best energy density among the commonly available batteries is the lithium battery (non-rechargeable) at 1.8 megajoules per kilo. Then to provide the 18 megajoules to get 1 kilo of oxygen you would need 18/1.8 = 10 kilos of the lithium batteries. I'll assume the weight of the system will be dominated by the weight of the batteries since electrolysis can be done simply by placing electrified wires in the water. So at 15 kilos of the batteries, the same weight as the scuba tank for 1 hour of breathing time, you would actually get enough oxygen for (15/10)*14 = 21 hours. Or said another way, to get enough oxygen for 1 hour would only take 10/14 = .7 kilos, about 1.6 pounds.
(Note: Edited calculations.)

Practical problems of course are for one how efficient is the electrolysis procedure? Also I believe the lithium batteries catch fire when wet. You would need to insure the battery casings are super-waterproof.

Then there is the weight of the electrolysis components, and the weight of the tank to hold the oxygen as it is being produced. You would also need to dispense with the hydrogen in a way to insure it does not combine with the oxygen to catch fire. It might be sufficient for this to mix it with surrounding water.

Though this would be technically doable the biggest problem is that scuba tanks do not use pure oxygen because it is toxic at depth. Perhaps GW can answer a question on this. The ISS astronauts would not need to prebreathe if their suits were at .8 bar O2. If O2 was given to divers at this pressure could it be used at depth without toxic effects?

This method could also be used to replace the heavy compressed oxygen tanks in astronauts suits by just carrying the small amount of water instead. The Primary Life Support System used on the astronaut spacesuits weighs 38 kilos. The power to separate out the approximate .54 kg oxygen out of water would only take about 5 kg of lithium batteries.

However, for the Mars spacesuit case, it might be more advantageous to separate out the O2 from the CO2 atmosphere. How much power is needed to separate 1 kg of O2 out of CO2? If the power required is not too high you may even be able to do it with solar cells so the astronauts could spend virtually unlimited amounts of time on the surface in their suits.

Bob Clark

Last edited by RGClark (2015-08-09 07:28:07)

GW Johnson · 2015-08-09 08:28:19

All I have on the PP O2 question is some rules of thumb regarding scuba (and helmet) diving. The rule of thumb is to stay under about 1 atm PP O2, whatever total P you are at. It seems anecdotally that around half of folks have serious problems breathing 1 atm PP O2 if exposed long enough, although times-to-trouble vary (several minutes, to some fraction of an hour, some are OK for hours). That's also the 30 feet depth limit rule of thumb for divers breathing pure oxygen.

It also seems that 2 atm PP O2 is lethal to pretty much 100% of those exposed, although times-to-trouble vary; nevertheless, those times are but a few minutes. You hit that breathing compressed air about 300 feet down in the sea. You'd hit the 1 atm PP O2 point at around 150 feet down.

Few sport scuba divers ever bump these limits, because few want to do something that would force them to do the decompression stops. That's not one-tank stuff. The nitrogen narcosis point on compressed air is a fuzzy limit, but usually quoted as 170 feet down and equivalent to 3 dry martinis on an empty stomach, where PP O2 also exceeds 1 atm a little. Perhaps those two effects interact, who knows?

GW

RGClark · 2015-08-09 08:51:30

The heat of combination of C and O2 is given by: C(graphite)+ O2(g)= CO2 (g) Standard Enthalpy Reaction= -393.5 kJ/mol . Since the molecular weight of O2 is 32, this means in this reaction 32 grams of O2 would result in 393,500 joules of energy being released. So 393,500/32 = 12,300 joules per gram of O2, or 12.3 megajoules per kilo of O2. So reversing this reaction you would need to supply 12.3 megajoules of energy to chemically separate 1 kilo of O2 from CO2.
This is less energy than for water at 18 megajoules per kilo of O2. However, you would still have the problem of the high amount of power needed to compress the O2 to the pressure needed by humans.

Bob Clark

SpaceNut · 2015-08-09 09:13:45

Would require less if you input co2 blocks of dry ice from mars deposits into a chamber an add heat to make it possible to make oxygen.

RobertDyck · 2015-08-09 10:00:41

Rather than compare your proposed system to SCUBA, try comparing to a rebreather. That's essentially the same technology as a spacesuit PLSS. It uses lithium hydroxide to scrub CO2, and pressurized oxygen. A rebreather does need a counter lung. Modern ISS spacesuit PLSS replaces the lithium hydroxide with silver oxide because it's regenerable. For single use it's actually heavier than lithium hydroxide, the advantage comes after multiple uses. ISS only needs one silver oxide canister per suit, it can be used over and over again. But your system replaced bottled oxygen, while the rest of the system is the same as a rebreather. So how does your system compare to a diving rebreather?

GW Johnson: the second generation MCP suit of Dr. Webb's contractor report to NASA included a vest. That vest was an air bladder, using pressure to replace MCP over the chest. With the vest connected to the breathing mask / helmet, it ensured pressure outside the chest was exactly the same as breathing air inside the chest, so it eliminated difficulty breathing. That air bladder vest essentially is a counter lung. But it also means leakage could come from the helmet, PLSS, vest, or interconnection hoses. Besides, 3.0 psi pure oxygen is easy for anyone to breathe without high altitude training. And the extreme limit low pressure risks dehydrating lung tissue. If lung tissue dehydrates, it will crack and bleed. That means hemorrhaging inside the lungs. Very bad. At 2.7 psi pure oxygen, astronauts only require moderate high altitude training, and humidity isn't an issue as the breathing system is so small that breath alone with humidify recycled breathing air. But 3.0 psi pure O2 appears to be very safe.

SpaceNut · 2016-01-09 20:18:43

Bump adding life support space suit items.

http://www.hq.nasa.gov/alsj/LM15_Portab … ppP1-5.pdf

http://ntrs.nasa.gov/archive/nasa/casi. … 017068.pdf

http://web.mit.edu/16.00/www/aec/lif_sup.html

GW Johnson · 2016-01-16 12:11:26

ISS spacewalk cut short by water leak into Tim Kopra's helmet. This is the very same suit that nearly drowned Luca Parmitano with a water leak back in 2013.

MCP suits, if made of porous material, need no water cooling system. You sweat right through it, just like you do your street clothes. This offers a way to eliminate a drowning risk, as well as a lighter, easily-launderable, and far more dexterous space suit.

This latest leak prompted me to post an article about MCP over at my "exrocketman" site. It goes into most, but not all, the design issues and features (I left out the discussion of the tidal volume breathing bag). http://exrocketman.blogspot.com

GW

RGClark · 2016-01-17 01:23:19

What is the difficulty with MCP suits for why they haven't been implemented?

Bob Clark

kbd512 · 2016-01-17 07:45:40

RGClark,

My understanding is that the compound curves of the human body make even application of mechanical counter-pressure an issue. Application of sufficient pressure also makes breathing difficult. Perhaps more important is the difficulty of suiting up. It makes no difference how difficult it is to breathe in a space suit if you can't put it on.

An air bladder was eventually used to reduce breathing difficulty. Compound curves like the armpits, groin, hands, and feet were also pressurized with air bladders. At that point, the suit was a hand made garment intended to fit a specific astronaut. That said, virtually all space suits of that era were hand made garments intended to fit a specific astronaut.

Perhaps the biggest issue was that the astronaut office did not trust the suits to protect the men wearing them. IIRC, that non-technical issue was ultimately responsible for the shut down of the space activity suit project.

Today, we have whole body laser scanning that can very precisely measure and model a person's body. We also have sewing machines that can rapidly produce garments that would require many hours of skilled labor in years past. A modern space activity suit would benefit from materials advances made since the 1960's, too.

Given the small numbers of astronauts that must be outfitted, and the incredible technology available for this task, a modern version of the space activity suit is well worth the effort to dramatically reduce the weight and volume of the suit, improve mobility and dexterity, and the risk of decompression from puncture.

Ideally, the air bladders previously used to assist with breathing and adequately pressurize appendages would be replaced by better materials. Someone at NASA needs to admit that current suit technology doesn't work very well for planetary environments or microgravity environments and then allocate resources appropriately.

A space suit that can be stuffed into a helmet is entirely possible. Obviously the PLSS will still be the size of a backpack. Hopefully technological advances will make it similar in size to a student's book bag rather than a hiking pack.

RobertDyck · 2016-01-17 08:20:01

RGClark wrote:

What is the difficulty with MCP suits for why they haven't been implemented?

Two issues, and only two issues. One, MCP suits are uncomfortable when partially on. They have to be either entirely on, or entirely off. This does mean when donning a spacesuit (putting it on) the suit will be partially on. At that point it's uncomfortable. The solution is to complete putting it on. Once fully on, the suit is more comfortable than any suit NASA has designed.

The other issue is competition. You would think researchers and those working on existing gas bag spacesuits would simply work on the new type of suit. But that hasn't happened. Instead those working on gas bag suits see MCP suits as competition, so they want to protect their jobs by criticizing MCP suits. So politics has slammed the MCP suit. When Apollo was cancelled by President Richard Nixon in 1972, many Apollo projects were cancelled too. The MCP suit was designed for the surface of the Moon, but wasn't ready in time for Apollo 11. They used the gas bag suit instead. The first Mercury suit was just the pressure suit used by the US Air Force for high altitude aircraft. It was designed for a pilot sitting in a cockpit with a multi-point seat belt, with just enough movement to be able to operate controls. Mercury never had an astronaut leave the spacecraft, so requirements for Mercury were the same. NASA incrementally improved the suit to increase mobility. The first Gemini suit was based on the last Mercury suit, so still incremental improvements. The first Apollo suit was based on the last Gemini suit. The suit suit worn on the Moon was the 7th generation improvement, known as A7L, meaning Apollo 7th generation. After Apollo, NASA incrementally improved the Apollo suit further, the result was the EMU, the white suit used on Shuttle. That suit is still used on ISS. They replaced the lithium hydroxide canister used to scrub CO2 from spacesuit air, the new suit uses silver oxide sheet metal. Silver oxide is heavier, but CO2 can be baked out with an oven, so the canister can be reused. One reusable canister weighs less than several expendable canisters, so this reduces total launch mass from Earth. This means the ISS suit is an incremental improvement on the Shuttle suit. NASA spacesuit guys have come up with further incremental improvements, all still gas bag suits, so based on the same basic concept as the original 1950s Air Force pressure suit. The Air Force had incrementally improved their design from initial suits developed in the 1930s. So this is a very old design.

Dr. Paul Webb was a medical doctor who specialized in decompression sickness. He started from scratch. He started with what the human body needs, and designed a spacesuit optimized to talk on the surface of the Moon. That's what it was for.

The EMU suit has a hard fibreglass upper torso, including chest and shoulders. It has hard joints for the shoulders, but soft over the biceps and rest of the arms. It has hard fibreglass shorts over the pelvis and hip joints. It's soft part way down the thighs and legs. It has hard fibreglass boots that have no movement in the ankle, or ball of the feet. It isn't like Apollo boots. You can't walk on the Moon with an EMU suit, if you tried to you would fall: "I've fallen and can't get up." But there are no paramedics on the Moon to pick up astronauts. EMU is optimized for Low Earth Orbit, and only LEO. NASA has developed the H1 and Z1 suits, which would work on the Moon, but still aren't as advanced as MCP.

Again, you would expect NASA researchers working on spacesuits would want to work on the most advanced suit. But they don't, they're protecting their jobs by defending an old, obsolete design. So the issue is convincing NASA to actually do it. Most of the researchers for MCP suits have either retired, or died of old age. The only one left is Dava Newman. To be blunt, she hasn't published as many papers as the others, but the others have either retired or died of old age. Dava is middle age, but still young enough to be employed. In 2015 she was hired by NASA. I would like to see Dava head a project to develop an MCP suit for NASA.

kbd512 · 2016-02-14 22:34:09

RobertDyck wrote:

Two issues, and only two issues. One, MCP suits are uncomfortable when partially on. They have to be either entirely on, or entirely off. This does mean when donning a spacesuit (putting it on) the suit will be partially on. At that point it's uncomfortable. The solution is to complete putting it on. Once fully on, the suit is more comfortable than any suit NASA has designed.

This thing should be six pieces (slip layer, body suit, gloves, socks), right?

How long does it take to put the suit on?

If a garment is not comfortable when it's half-way on, why not just finish putting it on to resolve the comfort issue?

RobertDyck wrote:

The other issue is competition. You would think researchers and those working on existing gas bag spacesuits would simply work on the new type of suit. But that hasn't happened. Instead those working on gas bag suits see MCP suits as competition, so they want to protect their jobs by criticizing MCP suits. So politics has slammed the MCP suit. When Apollo was cancelled by President Richard Nixon in 1972, many Apollo projects were cancelled too. The MCP suit was designed for the surface of the Moon, but wasn't ready in time for Apollo 11. They used the gas bag suit instead. The first Mercury suit was just the pressure suit used by the US Air Force for high altitude aircraft. It was designed for a pilot sitting in a cockpit with a multi-point seat belt, with just enough movement to be able to operate controls. Mercury never had an astronaut leave the spacecraft, so requirements for Mercury were the same. NASA incrementally improved the suit to increase mobility. The first Gemini suit was based on the last Mercury suit, so still incremental improvements. The first Apollo suit was based on the last Gemini suit. The suit suit worn on the Moon was the 7th generation improvement, known as A7L, meaning Apollo 7th generation. After Apollo, NASA incrementally improved the Apollo suit further, the result was the EMU, the white suit used on Shuttle. That suit is still used on ISS. They replaced the lithium hydroxide canister used to scrub CO2 from spacesuit air, the new suit uses silver oxide sheet metal. Silver oxide is heavier, but CO2 can be baked out with an oven, so the canister can be reused. One reusable canister weighs less than several expendable canisters, so this reduces total launch mass from Earth. This means the ISS suit is an incremental improvement on the Shuttle suit. NASA spacesuit guys have come up with further incremental improvements, all still gas bag suits, so based on the same basic concept as the original 1950s Air Force pressure suit. The Air Force had incrementally improved their design from initial suits developed in the 1930s. So this is a very old design.

Is there any particular reason why the inflatable suit competitors can't produce a MCP suit? It's seamless woven lycra. The competitors could save truck loads of money on the suit itself and dump R&D funds into the PLSS. Even with stupid simple suits, there's still untold millions to be expended in refinements to the PLSS.

RobertDyck wrote:

Dr. Paul Webb was a medical doctor who specialized in decompression sickness. He started from scratch. He started with what the human body needs, and designed a spacesuit optimized to talk on the surface of the Moon. That's what it was for.

Why shouldn't we let the environment dictate the suit requirements?

Note:

This is just an idea. If there's some feasibility reason why this is not possible, I withdraw the suggestion.

Hard Vacuum:

MCP suit surrounded by an inflatable suit with a sealing locking collar for the helmet (MCP suit collar locks and seals on inflatable suit collar). If the MCP suit fails due to a puncture or abrasion, the inflatable serves as backup. The neck of the suit should have an inflatable locking collar that interfaces with the helmet such that only the helmet is pressurized with gas during normal operations. If the astronaut requires more dexterity, he/she may remove the inflatable glove to expose the MCP glove. The suit should be designed in such a way that there's no possibility of drowning the astronaut with the LCVG.

Mars:

MCP only suit only. The redundant protection of an inflatable is not a realistic option due to size/weight constraints. It's my understanding that Martian regolith is not quite as abrasive as lunar regolith.

RobertDyck wrote:

The EMU suit has a hard fibreglass upper torso, including chest and shoulders. It has hard joints for the shoulders, but soft over the biceps and rest of the arms. It has hard fibreglass shorts over the pelvis and hip joints. It's soft part way down the thighs and legs. It has hard fibreglass boots that have no movement in the ankle, or ball of the feet. It isn't like Apollo boots. You can't walk on the Moon with an EMU suit, if you tried to you would fall: "I've fallen and can't get up." But there are no paramedics on the Moon to pick up astronauts. EMU is optimized for Low Earth Orbit, and only LEO. NASA has developed the H1 and Z1 suits, which would work on the Moon, but still aren't as advanced as MCP.

I think the EMU should be evolved to be akin to full body armor for debris protection for the MCP suit with a more advanced life support system built into it.

RobertDyck wrote:

Again, you would expect NASA researchers working on spacesuits would want to work on the most advanced suit. But they don't, they're protecting their jobs by defending an old, obsolete design. So the issue is convincing NASA to actually do it. Most of the researchers for MCP suits have either retired, or died of old age. The only one left is Dava Newman. To be blunt, she hasn't published as many papers as the others, but the others have either retired or died of old age. Dava is middle age, but still young enough to be employed. In 2015 she was hired by NASA. I would like to see Dava head a project to develop an MCP suit for NASA.

I think NASA needs to design and manufacture the MCP suit. Otherwise, they'll never accept the painfully obvious due to NIH Syndrome. They can use input from industry experts when required. NASA can mandate that full-on hard vacuum inflatables manufactured by industry be compatible with the MCP suit. While we're at it, an advanced MMU should be integrated into the EMU.

It's long past time for a more robust personal protection suite to come of age and I think we can please everyone here while admitting to reality- there's no such thing as a one-size-fits-all space suit.

RobertDyck · 2016-02-15 01:30:39

kbd512: I agree. The problem is that NIH syndrome has already taken hold. All researchers working on MCP were laid-off when Nixon cancelled Apollo. Remaining spacesuit guys have NIH syndrome. One researcher in the mid-1980s developed an MCP glove compatible with the EMU. The purpose was to construct a space station, they were thinking of stations back then. The MCP glove has greater range of motion for each finger joint, less counter-force to bend finger joints, and greater safety. But they didn't use it. In 2015 NASA hired the only remaining researcher working on MCP, the only one who hasn't retired or died of old age. Hopefully that means they'll work on it now.

PLSS: They did replace lithium hydroxide with silver oxide sheet metal. The new one is heavier, but can be reused easily. Just put the cartridge in an oven to bake out CO2. However, I have a paper from the NASA technical support server about using a microwave oven instead of an electro-resistive oven (aka toaster oven). It requires a cartridge with silver oxide granules instead of sheet metal, but that has greater surface area per unit mass, so the cartridge is lighter anyway. And there's a paper on continuously regenerating CO2 sorbent. If you don't want to bring CO2 back to the hab for recycling, then regenerate the CO2 cartridge in-situ, and just dump the CO2. The question is whether batteries to power the regeneration mass more than a full-size sorbent cartridge.

MCP means we don't need a cooling system. The entire cooling system is a bottle of drinking water. That could be simplified by installing a 1 litre plastic pop bottle, with a plastic bag liner. The pop bottle is filled with air, and an air hose back to the helmet. The bag is filled with water, and a drinking hose back to the helmet. As you drink water, the bottle sucks in air. The "pop bottle" would be the same size, shape, and plastic thickness as a standard pop bottle, but obviously made of a more sturdy material. I would use one of the fluoropolymers because they can withstand the cold of space without cracking. My favourite is PCTFE because it's so impermeable to water and oxygen. You could aluminize the polymer to clog the pours, make it even more impermeable. FEP is cheaper, but not as impermeable. And there's polycarbonate and polyimides.

Replace the aluminum alloy oxygen bottle with carbon fibre epoxy composite? Carbon burns in oxygen, so you would line it with a fluoropolymer. Again my favourite is PCTFE.

When Shuttle was flying, NASA had standard sizes for EMU suit components. Shoe sizes for spacesuit boots. Glove sizes for spacesuit gloves. Etc. Apollo had custom suits tailored for each astronaut. Right now MCP requires a custom tailored suit. But laser body scans and computer design can give you a pattern in seconds. And automated looms can weave custom fabric. Would it be knit like a sweater, or sewn? I saw a show called "How it's Made" which had an episode about rubber boots. They start with a machine that knits the fabric, then that fabric is put into a mould before rubber is injected. An MCP suit obviously doesn't have rubber, but would the suit be knit that way?

MMU: NASA has already done a lot of work. Manned Maneuvering Unit (MMU):

Simplified Aid for EVA Rescue (SAFER):

kbd512 · 2016-02-15 12:23:09

RobertDyck wrote:

kbd512: I agree. The problem is that NIH syndrome has already taken hold. All researchers working on MCP were laid-off when Nixon cancelled Apollo. Remaining spacesuit guys have NIH syndrome. One researcher in the mid-1980s developed an MCP glove compatible with the EMU. The purpose was to construct a space station, they were thinking of stations back then. The MCP glove has greater range of motion for each finger joint, less counter-force to bend finger joints, and greater safety. But they didn't use it. In 2015 NASA hired the only remaining researcher working on MCP, the only one who hasn't retired or died of old age. Hopefully that means they'll work on it now.

I think fear is a powerful motivator and they're concerned now that the existing suit has some fundamental flaws that a component redesign or two won't fix. It's obvious that the suits are impair mobility, but obvious problems aren't enough to motivate them to do something. Someone has to suffer death, injury, or other serious accident before anyone there will admit that there's a problem.

RobertDyck wrote:

PLSS: They did replace lithium hydroxide with silver oxide sheet metal. The new one is heavier, but can be reused easily. Just put the cartridge in an oven to bake out CO2. However, I have a paper from the NASA technical support server about using a microwave oven instead of an electro-resistive oven (aka toaster oven). It requires a cartridge with silver oxide granules instead of sheet metal, but that has greater surface area per unit mass, so the cartridge is lighter anyway. And there's a paper on continuously regenerating CO2 sorbent. If you don't want to bring CO2 back to the hab for recycling, then regenerate the CO2 cartridge in-situ, and just dump the CO2. The question is whether batteries to power the regeneration mass more than a full-size sorbent cartridge.

The real key to better suit technology is continuous development. You can't stop development as soon as you have a workable solution to a problem. As you pointed out, the greater surface area provided by using silver oxide granules versus sheets improves the performance of the overall solution. There's probably no technical reason why that hasn't been developed and implemented yet. It's simply a matter of priorities.

RobertDyck wrote:

MCP means we don't need a cooling system. The entire cooling system is a bottle of drinking water. That could be simplified by installing a 1 litre plastic pop bottle, with a plastic bag liner. The pop bottle is filled with air, and an air hose back to the helmet. The bag is filled with water, and a drinking hose back to the helmet. As you drink water, the bottle sucks in air. The "pop bottle" would be the same size, shape, and plastic thickness as a standard pop bottle, but obviously made of a more sturdy material. I would use one of the fluoropolymers because they can withstand the cold of space without cracking. My favourite is PCTFE because it's so impermeable to water and oxygen. You could aluminize the polymer to clog the pours, make it even more impermeable. FEP is cheaper, but not as impermeable. And there's polycarbonate and polyimides.

I'm not sure I'd go quite that far. I think you still need cooling.

RobertDyck wrote:

Replace the aluminum alloy oxygen bottle with carbon fibre epoxy composite? Carbon burns in oxygen, so you would line it with a fluoropolymer. Again my favourite is PCTFE.

I think we'd take the mass penalty associated with the oxygen bottle to avoid potential reactions with oxygen. However, it's certainly something to experiment with.

RobertDyck wrote:

When Shuttle was flying, NASA had standard sizes for EMU suit components. Shoe sizes for spacesuit boots. Glove sizes for spacesuit gloves. Etc. Apollo had custom suits tailored for each astronaut. Right now MCP requires a custom tailored suit. But laser body scans and computer design can give you a pattern in seconds. And automated looms can weave custom fabric. Would it be knit like a sweater, or sewn? I saw a show called "How it's Made" which had an episode about rubber boots. They start with a machine that knits the fabric, then that fabric is put into a mould before rubber is injected. An MCP suit obviously doesn't have rubber, but would the suit be knit that way?

The fabric for the suit would be woven/knitted by rather expensive computer controlled Shima Seiki looms that leaves no seams. NASA can afford to spend the several million dollars or so for the looms. I'm confident that a $10M to $15M outlay would cover the purchase price of the required machines. I firmly believe that leaving no seams in the fabric is that important for prevention of tears and even application of pressure. There also has to be some way to use directional fabric stretch to eliminate the requirement for inflatable air bags to reduce mechanical pressure applied over the chest cavity to assist with breathing.

RobertDyck wrote:

MMU: NASA has already done a lot of work. Manned Maneuvering Unit (MMU):

I'm aware of SAFER. I meant develop a MMU that uses AF-M315E propellant.

Aerojet makes a thruster with performance roughly equivalent to the MMU thrusters. The MMU weighs approximately 110 kg. I'm guessing we can either improve performance quite a bit or make the system more compact by using a propellant/thruster combination with an Isp of 235 (AF-M315E) vs 60 (GN2).

RobertDyck · 2016-02-15 12:52:07

MCP is fabric. You sweat through the fabric into space. Dr. Paul Webb did the initial work on MCP. He calculated water loss due to sweat. No need for anything more complicated than sweat.

The current system has long underwear with plastic tubes carrying water, with a circulation pump. That goes to a heat exchanger in the PLSS. And another water reservoir sprays water onto the outside of the heat exchanger, allowing it to sublimate into space. With MCP, no need for any of that.

And we have an incident that you could use to promote MCP. If you want to use political pressure, you could point out an astronaut already got a leak in the water cooling system while in space. He had to go inside, cutting his work outside ISS short. There was danger of drowning. Later a second astronaut had the same problem with the same suit. This isn't possible with MCP, because it just doesn't have the liquid cooling system. You could argue that we need to address this issue *BEFORE* someone dies. That's the hyperbole. But for this argument to be valid, the MCP suit must not have a liquid cooling system.

GW Johnson · 2016-02-15 13:11:38

I've revisited spacesuits and habitation atmospheres over at my site http://exrocketman.blogspot.com. The fresh posting includes four of Webb's old photos taken during his MCP experimentation in the 1960's. They're good photos, of the startling things that his test subject could do while pressure-breathing in the suit.

To have used this suit on the moon, as was intended, one would have to add a white insulated coverall as an outer garment over the MCP garment, plus some heavy hiking boots, and a selection of heavy leather or insulated gloves. These are all things to be bought at Walmart or equivalent stores. Think of his elastic leotard MCP rig as vacuum-protective underwear with a pressure-breathing helmet rig. It's quite the different way of thinking about how to make a space suit.

GW

RobertDyck · 2016-02-15 13:21:28

Dr. Paul Webb's first suit didn't have any air bladder. He used bags filled with liquid silicone to spread the force from MCP fabric evenly across hollows in the body. He covered the genitals, the crack of the ass, and trough of the lumbo-dorsal spine. He found they weren't needed for arm pits. Mitchell Clapp built the glove in the 1980s, using the higher pressure of the EMU suit. With higher pressure he found silicone filled bags were required for the flat of the back of the hand and palm. Paul Webb didn't need them because he used the lower pressure of Apollo suits.

Dr. Webb got a contract to build a prototype in 1967. He did, and submitted a contractor report. He then submitted a paper for publication in the Journal of Aerospace Medicine, submitted in December 1967, published in April 1968. Dr. Webb found that first suit had a problem. He had a test subject wear the suit in a vacuum chamber. The chamber he had access to was partial vacuum, the same pressure as 50,000 feet. The test subject had difficulty breathing. The tight fabric across the chest prevented embolism in skin, but that same tightness made breathing difficult. His second generation suit used an air bladder vest. It covered the chest and upper abdomen. When you breathe, your diaphragm causes your stomach to rise. So the air bladder vest provided constant pressure without restricting breathing. The vest extended down to the belt.

This vest solved a second problem. The US Navy found any rebreather requires a counter-lung. When you exhale, that breath has to go somewhere. The counter lung must expand as your chest and upper abdomen compresses. It must take the volume of air you exhale, and provide air for you to inhale with the next breath. Dr. Webb's vest is that counter lung. The outside of the vest is constant volume. As you inhale, the volume in your lungs increase. As you do so, you squeeze air out of the air bladder. The volume reduction of the bladder is exactly the same as the volume increase within your lungs, so there is no restriction to breathing. When you exhale, the reverse happens. If the suit didn't have an air bladder vest, you would need something else to be the counter lung. Any other design would be complicated and difficult. This is very simple, and very effective.

This also provides another advantage. You can use one-way valves to route air. Three hoses: from CO2 sorbent canister in the PLSS backpack to helmet, second from helmet to vest, third from vest to backpack. With one-way valves, the act of breathing circulates air. So if power fails in your suit, you don't suffocate. Your own breathing moves air through the sorbent.

SpaceNut · 2016-02-15 22:27:51

I have worked on cool suit designs with regards to the heat exchanger and what bothers me is the water inside the visor of the current suit.. that spells disaster... we need to get away from that suit design for sure.

kbd512 · 2016-02-16 04:20:05

RobertDyck wrote:

MCP is fabric. You sweat through the fabric into space. Dr. Paul Webb did the initial work on MCP. He calculated water loss due to sweat. No need for anything more complicated than sweat.

I don't think the sublimation process that the MCP suit uses for cooling is sufficient in direct sunlight.

Did Dr. Webb conduct his tests in a vacuum chamber capable of simulating the temperature ranges that astronauts would encounter in a hard vacuum?

RobertDyck wrote:

The current system has long underwear with plastic tubes carrying water, with a circulation pump. That goes to a heat exchanger in the PLSS. And another water reservoir sprays water onto the outside of the heat exchanger, allowing it to sublimate into space. With MCP, no need for any of that.

I want to integrate the MCP suit with an improved EMU suit. I want two pressure vessels for the head and body that are physically separated from each other with a locking collar that locks and seals the head into the EMU in such a way that migration of coolant from the LCVG into the head compartment is impossible without penetration of the locking collar. I want the EMU to serve as a backup and provide ballistic protection for the MCP suit. In normal operations in applicable environments, the portion of the inflatable suit below the head would not be pressurized. If the MCP garment is compromised due to a tear in the fabric, then the astronaut can pressurize the body compartment.

If the astronaut requires enhanced dexterity to perform a task, he can remove his EMU glove and use the minimal protection that the MCP glove provides to perform the task and then reattach his EMU glove.

RobertDyck wrote:

And we have an incident that you could use to promote MCP. If you want to use political pressure, you could point out an astronaut already got a leak in the water cooling system while in space. He had to go inside, cutting his work outside ISS short. There was danger of drowning. Later a second astronaut had the same problem with the same suit. This isn't possible with MCP, because it just doesn't have the liquid cooling system. You could argue that we need to address this issue *BEFORE* someone dies. That's the hyperbole. But for this argument to be valid, the MCP suit must not have a liquid cooling system.

I want to fix the existing problems with the EMU suit through modifications that separate the head compartment from the body compartment. I would like to accomplish that using by incorporating a locking collar to seal the astronaut's head into a separate compartment that permits the astronaut to use an un-inflated EMU suit by wearing the MCP suit inside the EMU suit.

The MCP suit is not a cure-all. The MCP suit can assist astronauts with hard vacuum EVA's by making inflation of the body compartment of the inflatable suit unnecessary and serve as a standalone suit in planetary environments with an atmosphere.

GW Johnson · 2016-02-16 10:54:52

Using MCP together with an uninflated balloon suit is a unique idea. But, it does guarantee a body-overheat condition because you are inside the rubber balloon, the same problem full pressure suits have had from their very beginnings in the 1930's.

My question is this: why would you want to combine the worst problems of both suit approaches? Why not instead treat the MCP as vacuum-protective underwear, that you can sweat through, and then just use whatever thickness and color of insulating outerwear suits the task at hand, unpressurized, and bought from the local retail store?

I would think that for daylight operations near Earth or Mars, a white coverall (or hunting pants and coat, take your pick, whichever is easier to don) will turn sunlight well enough. Near Venus, we might want to tailor an additional outer reflective layer out of an aluminized space blanket. Just pick the insulation thickness of the coverall (or hunting pants and coat) to match the level of cold experienced when not in sunlight.

Add to that heavy or insulated hiking boots to wear over the compression booties-as-socks. Carry a selection of light leather work gloves, heavy leather work gloves, and insulated gloves to wear over the relatively-thin compression gloves. You're pretty much prepared to handle just about anything you find.

Rather than complicate the helmet with too many visors, what's wrong with an oversized broad-brimmed hat? Take it off in the shade, put it back on out in the sun. Tether it to your suit so it doesn't drift away in zero gee, or burden your hands walking on a surface in gravity.

This kind of dress-for-space doesn't require over-engineering-for-profit. The only part of MCP that needs some engineering attention is the vacuum-protective underwear and helmet/tidal bag/backpack pressure-breathing rig. That the bulk of that is really equipment trials and improvements; the feasibility was done about half a century ago. The rest of it you buy at Wal Mart, or at worst adapt and tailor from stuff you buy at Wal Mart.

There's no need to add to the gravy-train giant-corporate welfare projects to make this stuff space-ready. You give it to the "usual crowd" (which includes NASA itself as well as its favorite suit contractors), and you'll never see it come to be. We'll just continue seeing what happened the last 50 years: nothing.

I'm getting awfully old, but John Glenn was older when he rode the shuttle. I'd be willing to take Webb's 1970-vintage design with the breathing bag, plus some coveralls boots, and gloves from Walmart (or wherever) and try it out myself in an EVA on the space station. How many hours of EVA would convince you guys? How many do you think it might take to convince NASA?

GW

Last edited by GW Johnson (2016-02-16 10:58:24)

RobertDyck · 2016-02-16 11:43:06

MCP was invented for the Moon. It was intended for Apollo, for the lunar surface. It's designed for hard vacuum. That said, it is intended for planetary surfaces: Moon or Mars. It's strengths are great flexibility, both greater range of joint motion and dramatically reduced counterforce, increased safety, reduced suit mass, simple cooling system, and cleaning. Since it's fabric, this spacesuit is literally machine washable. The weakness of the suit is donning and doffing: it takes time to put on the tight suit. And nothing will change that. Attempts to make donning and doffing easier and quicker will just obstruct development of this suit.

Apollo found a problem with that, they used a zipper on the back for donning and doffing (putting the suit on, taking it off). The zipper pulled closed two sides of the neoprene rubber pressure layer. It had a thicker rubber piece on either side of the zipper, and the zipper pressed them to each other forming an air-tight closure. That means the zipper had to close to provide an air-tight seal. The problem is lunar dust clogged the zipper. That's for a mission with just a few hours outside. A Mars mission will last months. The EMU uses metal ring seals with rubber O-rings, it doesn't have any zipper. Ironic considering the EMU isn't designed for the Moon.

NASA can continue to use gas bag suits for LEO. MCP is intended for planetary surface so the Moon and Mars. It doesn't need a cooling system, and don't even try to compromise. Just the bottle of drinking water. And no hybrid with any form of gas bag, not EMU or anything else.

EMU has a rigid fibreglass torso, with rotating joints around shoulders. It has rigid fibreglass "shorts", with rotating joints around hips. And rigid fibreglass boots that don't bend at all. It has convolute joint around the abdomen, but that doesn't work very well. The results are arms move well, but legs are stiff, ankles and toes cannot move at all, and the body is stiff. It's perfectly designed for use in LEO.

MCP provides enough dexterity for mountain climbing. And the helmet of an Apollo suit or EMU suit is "shoulder worn", with the head moving freely inside. That provides no restriction to turning your head, but it also provides no protection. Mars Society simulations at MDRS and FMARS revealed an issue: safety driving a 4-wheel ATV while wearing a shoulder-worn helmet. Many teams consider this so unsafe that they break sim, and remove their helmet while driving. You can't do that on Mars for real. An MCP suit has a head-worn helmet, like a closed-face motorcycle helmet. Mercury and Gemini did this too. It allows the helmet to be designed as a crash helmet, like a motorcycle helmet. It adds safety instead of creating danger.

I suggested the helmet have layers for backup. Two visors, one inside the other, and both pressure sealed to the metal ring around the visor. The hard shell of the helmet pressurized. And closed cell foam inside the hard shell, then a plastic bag inside that. Then open cell foam comfort layer inside the bag. The bag would be pressure sealed to the metal ring of the visor. So if the hard shell cracked on impact with a rock, then the plastic bag forms a backup pressure containment layer. To ensure the backup layer does not rupture at the same time, it must be separated from the hard shell (closed cell foam) and flexible.

As GW Johnson said, the MCP layer is worn as underwear. A parka and ski pants are worn over the underwear. They jacket or "parka" will provide a protection from tears and scuffs, and thermal insulation. For Mars, you could use Orthofabric, the same as the EMU suit. However, the Nomex backing is not needed on Mars. Micrometeoroids burn up in Earth's atmosphere 100km above the surface, they burn up in Mars atmosphere 30km above the surface. The bottom line is they burn up kilometres above the surface. Mars had rocks and equipment and sand storms, it doesn't have micrometeoroids. So we could use Tenara fabric instead of Orthofabric. Orthofabric is double layer plain weave, with 400 denier PTFE fibre outer layer, and the backing is Nomex with 2 threads replaced with Kevlar every 3/8" in both the warp and weave directions. Tenara is a single layer with a twill weave (same weave as jeans), made of the same 400 denier PTFE fibre but no backing.

And multilayer insulation works great in the vacuum of space, either LEO or the Moon, but doesn't work on Mars. The atmosphere of Mars may be thin, but it's enough that the aluminized Mylar acts as a heat sink, actually making the astronaut colder instead of keeping him warm. You need something like Thinsulate for Mars, the same insulation as ski pants and ski jackets on Earth.

This means one set of jacket/pants for the Moon, a different set for Mars.

I had also said you would want the air bladder close to the body. A neoprene rubber bladder would inflate to a cylinder. You could squish that flat over the chest and back, giving it an oval cross-section like the body. This would be moulded plastic, not fibreglass. And to give it strength, you want ridges moulded into the shape. Like the ridge of a car hood, or fluting of medieval body armour. The ridges can be any shape, but may as well make then aesthetically pleasing. So a muscle plate for men, or breast plate for women. It would be covered by the parka/jacket of the thermal-micrometeoroid/scuff garment anyway. Astronauts tend to be middle age, this muscle plate would be thin plastic, but would give every man a chest like Arnold Schwarzenegger and every woman a chest like Xena or Sif from the Thor movies.

GW Johnson · 2016-02-16 14:57:57

Air bladder (tidal volume breathing bag): Webb didn't use a hard shell for that, he used a kevlar jacket. The bag was something resembling a hot water bottle, if I recall correctly. The jacket may not need to be kevlar, per se, it just needs no "give", very inelastic. I think he used kevlar for the same reason I hate it for tow lines: only 2% elongation to failure. Hard plastic would serve the same function, but I doubt it's as cheap and easy as an inelastic fabric jacket.

As for the outerwear fabrics, what's wrong with ordinary canvas and bluejean material? That stuff is pretty damned tough out here on the semi-arid Texas cattle-rock-and-cactus ranch where I live.

Can't argue about the helmet, I know too little. The kind of crash helmet you suggest sounds like the oxygen-pressurized crash helmet of the old partial pressure suits. If the gas seal to the neck or suit is done "right", then suit pressures would not cause high forces trying to turn your head. The old partial pressure suits used a lower breathing pressure than the kind of suits we are talking about, but only a little lower. The bib tucked under the compression suit seemed to work for that.

Actually, for exposures of 10 minutes max, the old 1947 partial pressure suit would preserve functional life, even in outer space. The compression it achieved was too uneven to prevent fainting beyond 10 minutes due to blood pooling in arms and legs, and the uncompressed hands and feet would begin to swell after about 30 minutes. But he'd still be alive, just unconscious, even long after that. And after recompression makes the swelling go down, good as new.

I'm sorry, with MCP, this spacesuit thing is just not that hard. And THAT is what NASA and Hamilton-Standard, et al, do NOT want you to know.

GW

Last edited by GW Johnson (2016-02-16 15:03:14)

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