Backpacking on Mars - A base in a backpack... possible?

Trebuchet · 2005-02-06 16:29:27

Yeah, the idea is somewhat nutty, but I was thinking - is it possible to design a man-portable shelter for use on Mars, either for recreational use by colonists or, in the earlier exploration phase, to augment other trips into the extraterrestrial wilderness?

The concept I'm having is of a very lightweight airlock - basically two very lightweight aluminum and carbon fiber doors connected by an airtight polymer tube. The doors would be built as lightly as possible, and no provision for pumps, etc. would be made (lost air would be replaced by compressed gas bottles). The tent itself would also be made of an airtight polymer and sealed against one of the airlock doors. You prop the tent up (unpressurized), space the two airlock doors apart (with their own tent poles), then pressurize to 5 psi. You would probably need some sort of foam rubber insulating mat for the floor... but nothing says you can't split the load across two or three people, so it's doable.

Remember, you're in a 0.38 gravity field. Do you think it's doable? If it is, such disposable temporary bases might be useful. You could stash them on board a rover quite easily and deploy them at need, or simply hike over to a site of interest if it's near the base.

Trebuchet · 2005-02-06 16:30:51

For some reason, when looking for the correct folder to put this in, I read "Life on mars" and thought '... yeah, this will be about (human) life on Mars'.

You might want to move it, I guess.

Rxke · 2005-02-06 16:53:54

Heh, i've been thinking about that kind of thing, too. It should have a way to connect to your life support system of the suit you walk around in, for filtering and power or maybe coat it with solar cells to power pumps ( to re-compress the gasses back into the bottles etc...)

I was thinking about something very basic, more like a big plasticky sack, with airtight zipper, you step into and inflate. Would come handy as emergency 'bubble' when you are wounded or something, and too far from a hab or rover: step in to the sack with a healthy person, inflate, and then do the first aid in a more or less pressurized environment.

Trebuchet · 2005-02-06 21:30:57

Perhaps you could use electrostatic cling - like saran wrap - to form the seal? Three ply tent, ballistic nylon, an airtight polymer, and a clinging plastic. The outer two layers of the door zip, then you press the clinging plastic from the door to the inside of the tent. Presto, instant seal. Not perfect, naturally, but it's probably good enough for short term stuff.

Just don't forget your Demron sleeping bag to protect from ionizing radiation. :laugh:

Shaun Barrett · 2005-02-07 07:24:07

Are you guys sure you won't run into logistical problems here? ???
I did a bit of googling on the subject of scuba tanks, just to get an idea how much compressed air can be stored in them. A typical tank, 7.25" in diameter and 28.25" in height, pressurised to 3000 psi, can contain 107 cu.ft of air at Standard Temperature and Pressure (STP). Such a tank weighs 38 lbs empty. [Please excuse the Imperial units but the site I found uses them.]
Using Boyle's Law (P1V1 = P2V2 and ignoring temperature differences for the sake of simplicity), that tank could hold enough pure oxygen to provide 315 cu.ft of atmosphere at 5 psi.

That's about all you'd need to inflate a 'Mars-tent' some 7 x 7 x 6.5 ft, which would be a cosy but sufficient space for maybe 3 people.
But you could only do it once, unless you could recover all the oxygen each morning. And I think this would be difficult because of consumption of O2 and the inevitable leakage.

The tank itself would be bulky and awkward to carry but, on Mars, would weigh only 14.4 lbs. However, I think you may have to carry a small CO2 scrubber as well, considering you've got three people in such a small volume for maybe 8 hours or more.
Toilet facilities would be primitive (bags and wet-ones) but, in a life-threatening situation, that would be a secondary consideration, I suppose. And I guess the Apollo astronauts got to know each other pretty well, too!
Dividing up the Mars-tent hardware between the three hikers is an obvious solution to the problem of transporting it all, but it's potentially a problem in itself. If one of the hikers were to become separated from the other two by some mishap, it might be impossible to erect the tent because all the parts aren't there!

I think Kim Stanley Robinson got round some of these problems by transporting the camping gear on motorised hand-carts, if memory serves. It's not as sexy as backpacking but it may prove to be the minimum requirement for roughing it on Mars.
Or am I being unduly pessimistic? ???

Rxke · 2005-02-07 07:41:43

Thanks for the numbers, Shaun

Bulkyness will be the major concern here, so... an electric kart could come in handy as you say, but it isn't romantic.... power, as I said: from your backpack, or solar, fuelcells... to run the pumps, and the toilet(?)

Wel: pack a sled like thing, either on a 'leash' or like some Native American tribes did : directly on poles, resting on your shoulders, etc.

Aaaah: romance, suffering, hardship...

*Me imagining the would-be hikers returning after 10 minutes, figuring it's not worth the hassle after all

Trebuchet · 2005-02-07 10:28:27

You could pull the tanks on a golf handcart-like thing, I suppose. But such a tank would weigh about 14.5 pounds on Mars.

Weight allowances on Mars are an interesting subject. The decreased weight means all sorts of interesting things. Normally, the rule of thumb is something like 20-25% of body weight for carried stuff, although soldiers tend to carry more, relative to their weight... but we'll use the lower figures here for calculations. Now, on Earth, that means a 200 pound man should carry around 40-50 pounds. On Mars, this balloons to 105-132 pounds (all pounds are on Earth, of course!)... and he also gains 326 pounds because his body is designed to support 200 pounds, but is only moving 76 ((200-76)/.38). Granted, a lot of that extra weight allowance is going to be used on his spacesuit... but even if the suit weighs 200 pounds, that is, more than an Apollo suit, he can still carry more than his body weight in stuff without a problem. Even if you say that he can only lift the 105-132 pounds where the percieved weight on Mars is the same as the 40-50 pounds on Earth, that's still a *lot* of camping gear.

All that gear will still mass the same, of course, but that's not what kills your back hiking... it's holding that stuff up that's the killer. And Mars's low gravity puts a big hole in that one.

As far as the scrubber, the crude ones used on early submarines would probably be fine for the sort of short term stuff we're talking about. They used two chemicals, both of which I forget, one to remove moisture, and the other to remove CO2. You could have a small one rigged up with a fan and a couple batteries, no problem.

Remember, we're thinking fairly short term (one, two nights or so) stuff.

Rxke · 2005-02-07 14:05:50

Hey, and don't forget to pack a set of them Russian oxygen-generating candles!
Hmmmm... together with one-shot scrubbers, that might be a fairly lightweight solution.

RobertDyck · 2005-02-07 15:08:58

Think "pup tent". I actually submitted a short paper to NASA on this.

Don't use any frame at all, let air pressure form a dome tent. Apollo A7L suits used a back entry with compression seal and a zipper to hold the fabric closed. With the seal on the inside, air pressure helped push the two sides of the seal closed. Use the same thing for the Mars pup tent and don't bother with an airlock. Apollo found the zippers got fouled with fines, can anyone think of a way to hold the fabric closed that provides even tension (not ties or button)? Make the tent out of a single layer of aluminized Kel-F. That’ll handle the colder temperatures than will ever occur on Mars, is the most impervious to oxygen, and light-weight and transparent. The aluminized treatment will make it reflective to keep in radiant heat and keep out UV, but you could leave a panel for a window. Treat that panel with spectrally selective “heat mirror” to reflect 98% UV and ~40% IR but transmit visible light. Give it an aluminized flap that can be tied closed over the window.

Heat control is a big issue. Due to low atmospheric temperature, the tent will loose more heat at night to ground than air. Add an air mattress. Give the mattress several layers of polymer film inside suspended by threads. That’ll give astronaut(s) multi-layer insulation from cold ground. To prevent over heating, add a fan that circulates air between the lowest upper most layer, and a thermostat to control the fan. Run it from the PLSS battery. No overheating, you’ll dump excess heat directly to the ground; and no freezing, insulation and reflective interior will contain body heat.

Breathing would be accomplished by using the PLSS of the suit as life support in the tent. Just carry an extra oxygen bottle and CO2 sorbent cartridge for extended duration. As Trebuchet said, just inflate with compressed gas and then vent when leaving. Toilet facilities? Um, yea, this is camping. Bring some toilet paper and a baggie.

Add a sleeping bag and you’re set. You could get fancy and add a couple MREs, first aid kit, and repair kit for the suit and its PLSS.

BWhite · 2005-02-07 16:29:24

One company is already making parkas with pieces of aerogel sewn into the fabric. Use small overlapping pieces of aerogel and flexibility can be designed into the fabric.

Heat transfer is virtually nil with aerogels. (Add an optional system to bleed heat through tubes running outside of the aerogel.)

= = =

Sew some of those new wi-fi or wi-max microchips into the tent fabric and you have broadband as well.

= = =

A 4WD open air ATV - - like those used on Devon and in Utah - - with trailer? would seem a necessity if someone wanted to travel more than a few miles per day.

Edited By BWhite on 1107815541

Trebuchet · 2005-02-07 18:18:10

Apollo found the zippers got fouled with fines, can anyone think of a way to hold the fabric closed that provides even tension (not ties or button)?

Have you ever seen those kid's tents with the collapseable metal/plastic hoops sewn into the linings? I'm thinking you could make a door/airhatch frame and door/airhatch from two of them, and pop them together to seal things well. I suppose you could use ties as well on the inside to provide extra strength, too, depending on the operating pressure, though it's probably going to be a flat 5 psi oxy atmosphere.

Shaun Barrett · 2005-02-07 20:11:17

Don't underestimate the power of 5 psi.
It translates into about 3.5 tonnes per square metre.

A dome-shaped "pup-tent" will become more-or-less a sphere under those conditions, unless you have strengthening members to prevent it.

Trebuchet · 2005-02-07 20:20:22

Perhaps a Kevlar net holding the correct shape, or a different radius of curvature of the bottom like in one of Zubrin's city dome concepts?

RobertDyck · 2005-02-07 21:45:24

Actually, I had a dome tent with bent rod supports; don't anymore but the tent on my Aztek also uses those semi-circular supports. I'm saying you don't even need those; air pressure can support the tent.

You could use 5psi in the tent with 60% O2 / 40% N2, but it would be simpler to use the same pressure as the suit. Then you don't have to worry about gas mixtures. In case of emergency you would want to connect the gas bottle for the tent to your suit. Why not stick to 3psi pure oxygen? Managing a single gas is easy.

The real question, though, is the seal. The EMU uses metal rings at the waist, neck, and glove/boot cuffs. Rigid shapes are heavy and awkward to transport. Apollo suits used a firm synthetic rubber seal on either side of an opening with a zipper to pull them closed. Worked great except the zipper got fouled. Tent zippers also work great. Or do you mean 2 locking rings like EMU suits, but made of semi-flexible material that can be looped like those self-pop-up tents? That's a good idea! Design the material so it can bend into a tighter or looser ring, but not bend outward. It would have to twist somewhat so it could be looped, but you could prevent that from breaking the seal with a series of clips. You'ld want the door to open into the tent to ensure pressure kept it closed. So clips on the inside would be attached to the outer ring and fasten onto the inner ring.

Another question, would you want an outer layer of tent nylon, or just use fluoropolymer film? Kel-F is quite strong, tensile strength is 5,300 psi; as a comparison Teflon FEP tensile strength is 3,000 psi and its bursting strength for 1 mil film is 11 psi. That means 2 mil film of Kel-F should require 38.8 psi to burst. One atmosphere vs. complete vacuum is 14.7 psi. That means bursting pressure is 12.9 times the 3 psi operating pressure, a significant safety margin. A cylinder 1 metre (39.37") in diameter and 2 metres (78.74") long would have an area of 3.92699 square metres. One mil is 25.4µm and Kel-F density is 2.13g/cm^3 so that would mass 424.9 grams or 0.93678 pound. That's extremely light, but then add the hoop door seal, air mattress, fan the size of a computer case fan, and you would want a sturdy fabric where it meets the ground. Total mass is only a couple pounds. The oxygen bottle would mass more. Let's see... a 2 metre diameter dome tent that's 2 metres at the apex and a (relatively) flat floor. Integrate the air mattress so it is the floor of the tent, inflate it 4" deep with 4 mil top and bottom and 5 inner layers each 1 mil, the result is 3.623kg (8 pounds) of film. Add the weight of a single layer of tent fabric for the bottom, a tent bag, the ring seal, and it's still pretty light.

Trebuchet · 2005-02-07 22:53:06

Or do you mean 2 locking rings like EMU suits, but made of semi-flexible material that can be looped like those self-pop-up tents?

That was what I meant by

Have you ever seen those kid's tents with the collapseable metal/plastic hoops sewn into the linings?

This idea seems reasonably doable, it seems, although the final shape of the tent might not be traditionally tent shaped. I figure even a sphere is fine, as long as you anchor it well and fill the bottom with blankets and your suits and other crap to make a floor. Or just include a small suspended floor.

Wait, I have it. Just let the pressurized component of the tent be a sphere, for simplicity's sake, but inscribe that sphere in a collapsing-rod framework (pup-tent, tepee, whatever) to prevent it from rolling. Heck, have it look like a soap film bubble in a wire cube if you want. That would also let you suspend the manned portion of the tent off the icy Martian surface.

RobertDyck · 2005-02-07 23:25:57

Or just include a small suspended floor... let the pressurized component of the tent be a sphere...but inscribe that sphere in a collapsing-rod framework (pup-tent, tepee, whatever) to prevent it from rolling. Heck, have it look like a soap film bubble in a wire cube if you want. That would also let you suspend the manned portion of the tent off the icy Martian surface.

Woudn't an air mattress floor with multiple layers like a multi-pane window do exactly that?

SpaceNut · 2005-02-08 05:33:50

Here is a thought on the tent, make a x pattern in the fabric from corner to corner out of a blatter or tube sown between layers from the base to the top of the dome. Inflate under pressure this tube and the tent will take shape Add internal environment to support crew members inside.

One might setup a temporary camp around a solar powered compress c02 refueling station. Using the station to power a small reclaiming compressor to return the used air to the bottles each morning. Setup as many of these stations as possible from the base camp and spiral them out from it as we explore the area.

Trebuchet · 2005-02-08 09:48:50

Woudn't an air mattress floor with multiple layers like a multi-pane window do exactly that?

Yes, however, it wouldn't look as cool. :laugh:

Ian Flint · 2005-02-08 15:24:52

As for the seal...

1. take a single verticle opening,
2. attach a strong but flexible U-shaped connector along the length of each side of the opening,
3. interlock the two Us and
4. pressurize.

Like this:

------------------------------\
/---------------------o|
|o---------------------/
\-------------------------------------

What do you think, Robert?

Rxke · 2005-02-08 15:49:47

A Mars Society project in the making, perhaps?

Something that could be tried out incrementally at the Analog stations, without breaking the bank, for sure, pack it on the unpressurized rovers, for an extended hike, do some experiments on setting up, interfacing with backpacks etc...

It could be handy, if only for doing a lathering-up of your sweaty, itchy body after a day of exploring in your suit...

Trebuchet · 2005-02-08 17:39:48

Yeah, this would add utility to unpressurized rovers around the base, and it does seem to be something that can be tested 'on the cheap', as it were, right here on Earth. The only difficult bit here on Earth would be heat-build up in the tent (the opposite problem that Mars would have), but this could be eliminated by testing the device someplace cold... or even just testing in in a pool, to see if it's airtight; the water would effectively cool the tent. Tie a bunch of cinderblocks to it or something.

SpaceNut · 2005-02-10 09:37:41

Another use for this an simular concepts would be an inflatable cabin for the mars rover.

reddragon · 2005-02-13 17:19:19

Would there be any advantage to an inflatable cabin for the Mars rover? It would be more hassle to set it up each time you needed it and it would probably increase air loss. On a long journey such as you'd be using the pressurized rover for you'd be in the cabin most of the time both day and night anyway. It wouldn't be worth it to keep setting it up and taking it down.

An inflatable tent might be useful for use on short trips in the unpressurized rover or for emergencies but I don't think it would be good for long term use. I doubt it could be made as airtight and safe as a rigid structure.

Of course once people settle on Mars some will surely take up backpacking as a hobby (I'd probably be one of them if I lived there). They'll need pressurized tents and someone will probably develop them then if they haven't already. It's a pitty you'd have to hike in a pressurized suit and sleep in a pressurized tent and generally live in a separate enclosed environment. It takes away some of what I like about backpacking on Earth. But on Mars I guess that's the only way to go.

Trebuchet · 2005-02-13 21:52:35

An inflatable tent might be useful for use on short trips in the unpressurized rover or for emergencies but I don't think it would be good for long term use.

This happens to be exactly the point of the inflatable 'backpack' tent. For the rover, I believe that we're talking about a pop-up trailer type setup. For instance, you could have a 'second floor' on the rover, connected by a ladder, which is a sort of loft to toss your sleeping bags, put up a folding table, etc, if you made the walls out of airtight plastic and radiation-absorbing synthetic cloth. It would fold down to a foot or two when the rover is moving, and when you stop and need the extra space, you raise and inflate.

RobertDyck · 2005-02-14 00:30:33

For the Mars Direct emergency where the hab lands far from the ERV, you would use the pressurized rover. At the Mars Society conference in Eugene in 2003, Robert Zubrin said he was concerned the chapters developing analog rovers were building vehicles too big. It was intended to get astronauts to the ERV, not be a mobile laboratory. He asked Frank to design a tent trailer for an open rover to replace the pressurized rover. The range was designed for 1000km, if you assume average speed over rough terrain of only 30km/h (18.6mph) then it would take 33 hours and 20 minutes. I've driven 28 hours straight, only stopping for gas, washroom, and filling my coffee cup. I was wiped-out tired, but I did it alone. The one time I drove that stretch with a friend it seamed easy because I could nap while he was driving. On Mars the astronauts would have each other, although they would be in suits. The tent trailer appears luxurious compared to highway driving in a sports car, or highway driving with a friend in a moving van.

The pup or larger dome tent would be used for literally hiking on Mars. It would also be included as safety equipment on an open rover for any extended duration outing. Together with the tent bring a first aid kit, repair kits for suit/tent/rover, bottle of oxygen, CO2 sorbent cartridges, and a means to recharge suit batteries from the rover. Also bring an MRE or two, toilet kit (TP, baggie, wet wipes), and sleeping bag.

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Re: Backpacking on Mars - A base in a backpack... possible?

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Re: Backpacking on Mars - A base in a backpack... possible?

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