NASA could make 'Skylab II' first deep space 'home'

SpaceNut · 2015-01-27 18:27:48

This topic started with these following posts...

GW Johnson wrote:

As for artificial gravity, two things: (1) it does not have to be a full wheel. Any long vehicle with a habitat at one end can spin end-over-end to put about 1 gee in that habitat. 4 rpm at 56 m is one gee. That's actually quite do-able, right now. (2) Until we know any better, I'd go with one full gee, both ways. We do NOT know that 0.38 gee at Mars is enough to be therapeutic. The returning crew, even from LEO, will see 4+ gees on reentry, maybe 10-15 if on a free return. They will die if unhealthy during that ride.
Radiation protection is more scare than real. Galactic cosmic radiation (GCR) is too energetic for any practical methods of shielding, you're just going to get a dose. How much you get depends upon when you go. GCR varies sinusoidally between 24 and 60 REM, in phase with the solar cycle. An active stormy sun is associated with the 24 REM, and vice versa. Current astronaut yearly limit is 50 REM, and there's a career max that varies with gender and age. A Mars crew does not need to fly outside the Van Allen Belts a second time. If they do get a bit too much in any one year (60 vs 50 REM), it's only a little bit too much. And the structures around them actually do have a tiny shielding effect.
Solar flare during active sun periods is the lethal item. This is far less energetic, and we can shield it. About 20 cm of water works fine for the worst flares, and most are nowhere that big. But some are, and you must have a way to shelter from them, or it will kill you in a matter of hours. Water, wastewater, frozen food, all qualify. You have them with you as part of your long-term life support, so use them as shielding materials, too. Not every habitable space needs shielding, just a spot where everyone can hide for a few hours. I'd make it the flight deck, so that critical maneuvers could be flown, regardless of the solar weather.
One of the remaining bugaboos is lightweight astronaut food. It only lasts 12-18 months in edible condition. Frozen and canned stuff lasts the years we need, it's just heavier. So bye-bye minimalist minimum-thrown-weight ideas!
The other bugaboo is space to stay sane, and this is usually underestimated, and it isn't arranged well, in most of the designs I have seen. People need spaces to congregate, and they need spaces to be alone (and that's not just a bunk!). They need an organized workstation, and they need something generalized and reconfigurable for recreation. The total volume per person ought to look about like the old Skylab. 3 was great in there, it'd be marginal at 6.
GW

RobertDyck wrote:

GW: I've argued that the Mars Direct habitat is a nice size. It was designed for artificial gravity during transit to Mars, and would be the surface habitat. It had the same ceiling height, and same floor area as a 60-foot class-A motorhome with slide-outs. That's the upper floor alone, not counting the lower floor. That's because the lower floor will be filled with: landing rocket engines, fuel tanks for the landing rockets, life support equipment, batteries, airlock, and a garage for the rover. It was to include a rover capable of carrying all 4 crew one-way up to 1,000km, in case the hab landed that far from the ERV. I use the word "garage" for storage space for the rover. That storage space will also have surface science equiment, and an inflatable greenhouse stored deflated/folded. So the entire lower floor will be completely unusable during transit to Mars. However, once on Mars that garage will be unpacked, that stuff won't come back in. So that will give them a single-car garage as workshop/lab. EVA prep will probably be part of that "single car garage". And once deployed, the inflatable greenhouse will be about as big as a double car garage. I think that's enough. The "Achilles' heel" of Mars Direct is the ERV. It's the size of a Dragon capsule.
I still think we need to start with this. I posted this before, it's the floor plan for the Mars Direct habitat. The original version of Mars Direct, circa (I think) 1990. The colour version published in the March 2000 issue of Scientific American.
This version has the airlock in the centre, with food storage in the walls. That makes the airlock double as radiation shelter. All updates to Mars Direct move the airlock to the ground floor. The lab is also here, but updates move the lab to the lower floor. The "garage" would serve as lab. The medical/health room doubles as exercise room; which is a good idea. This floor plan has a separate stateroom for each crewmember, with a desk. No chair, you would sit on the edge of the bed to use a desk. And the bathroom has a toilet, sink, and shower.
Care to draw an updated floor plan? Assume the outer wall will be smooth with stages of SLS, so the outer wall will be 8.4 metre diameter. How thick will the walls be? Do you want a chair for each desk? Should the bed have storage beneath (captain's bed), or fold like a Murphy bed, or fold like a railroad sleeping car? What would the radiation shelter look like?

Last edited by SpaceNut (2015-01-27 18:30:47)

SpaceNut · 2015-01-27 18:36:31

NASA could make 'Skylab II' first deep space 'home'

130404-SkylabPhoto-hmed-1050a_files.660;660;7;70;0.jpg

With a little tinkering, the upper-stage hydrogen propellant tank of NASA's huge Space Launch System rocket would make a nice and relatively cheap deep-space habitat, some researchers say.

130404-Skylab1Photo-hmed-1050a_files.380;380;7;70;0.jpg

Its upper-stage hydrogen tank is big, too, measuring 36.1 feet tall by 27.6 feet wide (11.15 m by 8.5 m).

The tank's dimensions yield an internal volume of 17,481 cubic feet (495 cubic m) — roughly equivalent to a two-story house. That's much roomier than a potential deep-space habitat derived from modules of the International Space Station (ISS), which are just 14.8 feet (4.5 m) wide, Griffin said.

130404-Skylab2Photo-hmed-1050a_files.380;380;7;70;0.jpg

kbd512 · 2015-01-27 20:06:34

If NASA makes a deep space habitat out of aluminum, given their understanding of the radiation environment, then they can stop with all the radiation danger hoopla.

The researchers who think an aluminum can is a good deep space habitat probably haven't been exposed to too many SPE's.

A habitat of that volume would certainly provide more storage.

Astronauts of the Sea. Shipped direct to Mars in fantastic plastic.

RobertDyck · 2015-01-27 20:13:48

kbd512: Which plastic are you thinking of? What is its embrittlement temperature? How does it withstand vacuum?

kbd512 · 2015-01-27 20:21:09

RobertDyck wrote:

kbd512: Which plastic are you thinking of? What is its embrittlement temperature? How does it withstand vacuum?

I'll let the people doing the work provide the explanation:

http://www.tms.org/pubs/journals/JOM/0901/sen-0901.html

SpaceNut · 2015-01-27 20:51:25

The lunar mission outpost topics of the past did talk of a hydrogenated plastic to be one of the protective elements but from what irc was it was 6 inches thick making it not pratical for a complete vehicle but as a shelter area it would be more preferable to use it for with those specifications of need.

RobertDyck · 2015-01-27 21:23:14

So you don't know. The linked article talks about fundamental research. Although research is good, this material is far from ready. You realize one goal of any spacecraft design is reduced weight. Once you do that, you reduce radiation shielding. And the article talks about polyethylene. This article gives some data on high density polyethylene. It states embrittlement at -180°F, which is about -117.78°C. LEO experiences wide temperature swings. The Canadian Space Agency website says a spacesuit must handle +120°C to -150°C. Wikipedia says +250°F (+121°C) to -249°F (-156°C). I guess it depends if you round to Celsius or Fahrenheit. Either way it doesn't sound like polyethylene will provide structural strength to hold air pressure.

TransHab uses more advanced polymers. But they're light, not optimized for radiation shielding. Kevlar is an advanced form of Nylon, containing chlorine. Nomex also contains chlorine. Nextel is alumina-boria-silica. Initially, TransHab provides more protection against micrometeoroids than aluminum alloy. However, I have to ask how it will stand up over time.
TransHab has Multi-Layer Insulation on the outside, which is the same thermal insulation as ISS. That consists of the aluminized Mylar, with Kapton backing. Dacron fabric keeps the Mylar layers separate. I believe the outer most fabric is Orthofabric, the same as EMU spacesuits. That is a double layer plane weave of PTFE fabric facing, with Nomex backing, and every 3/8" two thread of Nomex are replaced with Kevlar.
NASA: Multi-Layer Insulation

A lot of materials. Nextel particularly is not your plastic radiation shielding. It's a ceramic fibre of aluminum, boron, silicon oxides. The MOD shielding is Nextel, then foam, then ballistic Kevlar. TransHab repeats that sandwich 3 times. Nextel breaks up micrometeoroids, the foam separates Nextel from Kevlar so the pieces can separate, then ballistic Kevlar acts as a bullet-proof vest to stop them. But heavy ion GCR will react to Nextel the same as so much aluminum alloy.

kbd512 · 2015-01-27 22:07:12

SpaceNut wrote:

The lunar mission outpost topics of the past did talk of a hydrogenated plastic to be one of the protective elements but from what irc was it was 6 inches thick making it not pratical for a complete vehicle but as a shelter area it would be more preferable to use it for with those specifications of need.

This was an attempt to create a technology set that covered everything from deep space operations to reentry into the Earth's atmosphere. A purpose built deep space habitat need not utilize all aspects of the materials solution provided, but perhaps a multi-function habitat that makes use of all these technologies could service all mission requirements. If we drop the launch abort system requirements, our intrepid explorers could conceivably launch in their transfer habitat, use the habitat to transfer to go to/from Mars (assuming a methalox propulsion module that can take advantage of ISRU is included), and then reenter Earth's atmosphere after they've completed their mission.

Anyway, that's the juice. Worth the squeeze? Not sure.

SpaceNut · 2015-01-27 22:12:34

The link date from a search did yield a few places to read up on the protective thoughts on plastic... plastics that mimic human tissue to look at how these highly energetic particles penetrate and interact with the human body

http://science.nasa.gov/science-news/sc … ctivemoon/

By placing the radiation detectors in CRaTER behind various thicknesses of a special plastic that has similar density and composition to human tissue, Spence and his colleagues will provide much-needed data:

June 14, 2013 Plastic Could Protect Astronauts from Deep-Space Radiation

Plastic shielding could help protect astronauts from harmful radiation on long journeys through deep space, new observations from a NASA moon probe suggest. "This is the first study using observations from space to confirm what has been thought for some time —that plastics and other lightweight materials are pound-for-pound more effective for shielding against cosmic radiation than aluminum,"

Radiation Protection for Lunar Mission Scenarios

[url=http://isru.msfc.nasa.gov/lib/Documents/wksp2005/day2/Radiation_Shielding.pdf]Radiation Shielding:
Lunar Simulant Requirements[/url]

kbd512 · 2015-01-27 22:26:23

RobertDyck wrote:

So you don't know. The linked article talks about fundamental research. Although research is good, this material is far from ready. You realize one goal of any spacecraft design is reduced weight. Once you do that, you reduce radiation shielding. And the article talks about polyethylene. This article gives some data on high density polyethylene. It states embrittlement at -180°F, which is about -117.78°C. LEO experiences wide temperature swings. The Canadian Space Agency website says a spacesuit must handle +120°C to -150°C. Wikipedia says +250°F (+121°C) to -249°F (-156°C). I guess it depends if you round to Celsius or Fahrenheit. Either way it doesn't sound like polyethylene will provide structural strength to hold air pressure.

You did read the part of the article about the second composite, right? I am not aware of any thneed material that's all things to all people at all times. The second composite was developed to provide thermal and ballistic protection. PE fabrics are not going to survive a reentry or even withstand the thermal flux of space very well, but it's about as good a material for passive radiation shielding that a spacecraft could realistically use.

RobertDyck wrote:

TransHab uses more advanced polymers. But they're light, not optimized for radiation shielding. Kevlar is an advanced form of Nylon, containing chlorine. Nomex also contains chlorine. Nextel is alumina-boria-silica. Initially, TransHab provides more protection against micrometeoroids than aluminum alloy. However, I have to ask how it will stand up over time.
TransHab has Multi-Layer Insulation on the outside, which is the same thermal insulation as ISS. That consists of the aluminized Mylar, with Kapton backing. Dacron fabric keeps the Mylar layers separate. I believe the outer most fabric is Orthofabric, the same as EMU spacesuits. That is a double layer plane weave of PTFE fabric facing, with Nomex backing, and every 3/8" two thread of Nomex are replaced with Kevlar.
NASA: Multi-Layer Insulation

There's only one way to find out how well a material holds up over time. Last time I checked, we still had a rather large orbital facility to test it at.

RobertDyck · 2015-01-27 23:57:26

kbd512 wrote:

There's only one way to find out how well a material holds up over time. Last time I checked, we still had a rather large orbital facility to test it at.

Damn good idea. Bigelow Aerospace wants to add a small module that can be carried in a Dragon CRS trunk. Good idea. Even if it isn't used, just to test the material.

I'm saying PE can't be used for pressure containment, or restraint. You could stack sheets against the walls as radiation shielding. Polypropylene could be used for the same purpose. For radiation shielding, it's about the same. I read a NASA article that claimed PP could better withstand polymer degradation from radiation. But realize this doesn't replace the aluminum can, just add to it.

Ok, you want me to read the whole thing. Oh! They want to use UHMWPE, also known as Spectra. That's different. Same ratio of carbon to hydrogen, so same radiation shielding, but much stronger. Composite 1 is Spectra with resin. Still not comfortable with the idea of spacecraft pressure shell made of this stuff. Spectra 1000 is only rated for +100°C to -150°C. Spectra 1000 becomes embrittled below -150°C; but spacecraft exterior in LEO has to endure +121°C to -156°C, so that's really pushing it. Do they want to replace Nextel in the ballistic sandwich for TransHab? You can't replace a soft fabric with a rigid composite; it can't deploy.

kbd512 · 2015-01-28 04:05:14

RobertDyck wrote:

kbd512 wrote:
There's only one way to find out how well a material holds up over time. Last time I checked, we still had a rather large orbital facility to test it at.
Damn good idea. Bigelow Aerospace wants to add a small module that can be carried in a Dragon CRS trunk. Good idea. Even if it isn't used, just to test the material.
I'm saying PE can't be used for pressure containment, or restraint. You could stack sheets against the walls as radiation shielding. Polypropylene could be used for the same purpose. For radiation shielding, it's about the same. I read a NASA article that claimed PP could better withstand polymer degradation from radiation. But realize this doesn't replace the aluminum can, just add to it.
Ok, you want me to read the whole thing. Oh! They want to use UHMWPE, also known as Spectra. That's different. Same ratio of carbon to hydrogen, so same radiation shielding, but much stronger. Composite 1 is Spectra with resin. Still not comfortable with the idea of spacecraft pressure shell made of this stuff. Spectra 1000 is only rated for +100°C to -150°C. Spectra 1000 becomes embrittled below -150°C; but spacecraft exterior in LEO has to endure +121°C to -156°C, so that's really pushing it. Do they want to replace Nextel in the ballistic sandwich for TransHab? You can't replace a soft fabric with a rigid composite; it can't deploy.

Good grief, man. Reading required. The test articles were two composites, used in conjunction with each other, to cover the gamut of protection problems that a habitat module would encounter, from transit to reentry. Both composites are solid materials, so to speak. The spectra composite material is inside a carbon foam overwrap. The spectra composite provides radiation protection and atmospheric containment. The carbon foam provides thermal protection equivalent to the Space Shuttle HRSI tiles and has an impact resistant coating applied to provide high velocity impact protection.

Nothing's perfect, but this solution uses materials with complementary properties that are lightweight and efficient for their intended functions. If there's something better available, I'm sure we'll hear about it.

RobertDyck · 2015-01-28 04:44:51

Not required, and annoying. Your descriptions of those materials is overblown. I really don't see an applicaiton for either. Research is good, but neither appear to be truly applicable.

kbd512 · 2015-01-28 04:52:24

RobertDyck wrote:

Not required, and annoying. Your descriptions of those materials is overblown. I really don't see an applicaiton for either. Research is good, but neither appear to be truly applicable.

Dare I ask what would be applicable?

Do you have a different material or set of materials in mind?

RobertDyck · 2015-01-28 05:40:58

I also have to point out the original Mars Direct habitat only had one level. The landing rockets and fuel tanks were attached to the bottom. And the pressurized rover was attached to the bottom by cables, between the landing rockets. Landing legs were long enough that landing rocket engines wouldn't dig a hole in the ground. That meant a significant ladder from the underside of the habitat to the ground. And the rover would be dropped via winch. The modern two-story design looks easier to use: ramp for rover, stairs to airlock side instead of ladder to airlock floor. But that's already increasing mass.

We've seen on ISS that life support equipment requires maintenance and repairs. The original Mars Direct habitat put life support beneath living space in an area in accessible during flight. That's not going to work. Building it into the walls of the "garage" mean it will be accessible. So that's an improvement. But realize this is already significant mass creep.

GW Johnson suggested increasing hab size to Skylab. I argue that's too much.

RobertDyck · 2015-01-28 05:52:49

kbd512 wrote:

Dare I ask what would be applicable?
Do you have a different material or set of materials in mind?

I was thinking of just Weldalite, which is aluminum/lithium alloy. That's the same alloy used for the external tank of the Space Shuttle. Robert Zubrin and David Baker used that for Mars Direct. So sticking with the original. But before you posted, I was thinking some more. To expand the habitat to the two deck/story design that I described, really demands lighter materials. The obvious candidate is carbon-fibre/epoxy composite. But the composite your web page describes is Spectra/epoxy. I pointed out temperature limitations, but if protected by multi-layer insulation, it just may work. That's the same insulation as ISS modules, and actually the same as an EMU spacesuit. Hmm.

And use ALON for windows instead of glass. Two reasons: it's 1/4 the thickness of the strongest glass, for the same strength, consequently 1/4 mass. And so impact resistant and so hard that I expect no micrometeoroid pitting. Of course with the same spectrally selective coating as ISS windows, to control UV and IR.

RobertDyck · 2015-01-28 06:46:51

kbd512 wrote:

Shipped direct to Mars in fantastic plastic.

Not enough sleep. This reminds me of a silly song.
YouTube: Barbie Girl

I'm a barbie girl, in the barbie world. Life in plastic, it's fantastic!

RobertDyck · 2015-01-28 07:17:25

GW Johnson: Question, will Spectra work as a tether? I'm worried about temperature. Mountain climbing rope is based on Spectra.
MEC: Choosing a Climbing Rope

Modern climbing ropes are manufactured using a process of kernmantel construction. A nylon sheath (mantel) is tightly braided around the core (kern) of the rope. This outer sheath is the rope's "armour", designed to protect the load-bearing core.

We had discussed this before. Spectra is more flexible than Kevlar, and greater tensile strength, so makes a better rope. That's why the core of mountain climbing ropes are this material. But instead of nylon sheath (mantel), use the same PTFE (Goretex) as the outer most layer of Orthofabric. That is fluoropolymer, so protects against mono-atomic oxygen.

kbd512 · 2015-01-28 08:48:33

RobertDyck wrote:

kbd512 wrote:
Dare I ask what would be applicable?
Do you have a different material or set of materials in mind?
I was thinking of just Weldalite, which is aluminum/lithium alloy. That's the same alloy used for the external tank of the Space Shuttle. Robert Zubrin and David Baker used that for Mars Direct. So sticking with the original. But before you posted, I was thinking some more. To expand the habitat to the two deck/story design that I described, really demands lighter materials. The obvious candidate is carbon-fibre/epoxy composite. But the composite your web page describes is Spectra/epoxy. I pointed out temperature limitations, but if protected by multi-layer insulation, it just may work. That's the same insulation as ISS modules, and actually the same as an EMU spacesuit. Hmm.

Why are so many people fixated on using the metal used in the ET? A lightweight gas tank that's used for a few minutes and a long duration deep space habitat have completely different design requirements. There's no economy to be had from using gas tank materials if it leads to the early demise of your crew.

Zubrin and Baker don't know bean dip about radiation. They want to ignore all of it and pretend that the storm shelter to protect against SPE's is all that's required. I have no doubt that the astronauts will get a dose from GCR's because we just don't have anything that can stop particles at those energies, but there's prudent design for that environment and then there's ignoring the problem.

If NASA insists on building their habitat from aluminum, then they can quit going on about the radiation threat because they already know what happens when ions hit thin aluminum cans and they don't need any further data on that. Heck, they had two of their team members who were working on habitat design give a presentation not too far back where they indicated that they were trying to get rid of as much metal in the habitat as they could get away with. The article describes use of two composites that work in conjunction with each other, as previously stated. The ISS modules and EMU are, by NASA's own description, rather poor for stopping particles from SPE's and GCR's.

RobertDyck wrote:

And use ALON for windows instead of glass. Two reasons: it's 1/4 the thickness of the strongest glass, for the same strength, consequently 1/4 mass. And so impact resistant and so hard that I expect no micrometeoroid pitting. Of course with the same spectrally selective coating as ISS windows, to control UV and IR.

How about we skip windows, irrespective of the rest of the materials selected? I think a camera or camera set is sufficient. There's no reason to compromise the integrity of the habitat any more than absolutely required. If the habitat is rotated to provide artificial gravity, they're not going to be looking at anything that won't make them want to hurl, anyway.

You're still thinking like we're operating in LEO. The environment is different and it's different enough to matter.

RobertDyck · 2015-01-28 09:26:10

Zubrin and Baker are engineers. They do know how to design a spacecraft. You are ignoring temperature, strength, mass, stress loads, etc. Aluminum lithium alloy is strong and light weight. It wasn't just for ET, it's also used for the fuselage of the Boeing 777X.

Spacecraft with no windows? I don't think so.

So your obsession is radiation.
Screen+shot+2010-07-13+at+3.38.58+AM.png

kbd512 · 2015-01-28 11:05:44

RobertDyck wrote:

Zubrin and Baker are engineers. They do know how to design a spacecraft. You are ignoring temperature, strength, mass, stress loads, etc. Aluminum lithium alloy is strong and light weight. It wasn't just for ET, it's also used for the fuselage of the Boeing 777X.

Yes, they're engineers from the 1980's to 1990's. This is 2015. When was the last time they designed a spacecraft? We know they didn't design Apollo and that was the last deep space transfer vehicle NASA flew.

The composites are comparable in mass to NASA's favorite alloy, which is why the researchers even bothered to determine their properties. You're still not getting this "no magic material" concept. Two composites with two different purposes were designed to be used in conjunction with each other. Mass is mass and it doesn't matter where you put it. You can lug additional descent/ascent vehicles with you, or you can use the transfer habitat as a multipurpose vehicle that precludes the requirement for additional vehicles to get to/from Mars and to/from Earth.

For overall mission design and cost, fewer pieces of flight hardware is better. If you asked if I'd like to take two or three different vehicles to go to/from Mars or just one, provided it could satisfy all the mission requirements, I know which option I'd select.

RobertDyck wrote:

Spacecraft with no windows? I don't think so.

A high-def image isn't good enough?

RobertDyck wrote:

So your obsession is radiation.

NASA's obsession is with radiation. I could care less if they fry as long as they do it after they complete their exploration mission on Mars.

RobertDyck · 2015-01-28 11:36:48

Radiation protection of this material is interesting. They cite how this material blocks radiation in comparison to pure polyethylene. I would like to see how much radiation it blocks. For a wall of appropriate thickness for the pressure of a spacecraft.

But my point is you obsess about radiation to the exclusion of all else. Radiation protection is nice, but doesn't cut it if a section of wall gets hot and suffers creep. Remember, with a composite the fibre is supposed to provide tensile strength. If you heat the fibre above its working temperature, it will permanently deform. Instead of a composite, you have nothing but resin. Or if you freeze the fibre to the point of embrittlement, it will break. Again, you have nothing but resin. If a section of wall breaks, then you have pressure loss. Spacecraft decompression is not pretty.

Also, TransHab uses multiple layers of soft materials to replace the rigid alluminum alloy wall. Part of that is MOD shielding. What is the impact strength of this composite? Again, we don't want a micrometeoroid punching a hole in the hull.

GW Johnson · 2015-01-28 12:23:06

This is a very interesting discussion going on about materials of construction for a spacegoing habitat module. One should note that the requirements are light years apart for a hab that stays in space “forever” vs a hab that must enter atmosphere and land somewhere. Those requirements will likely never be resolved for some centuries yet.

What I don’t understand is insisting on exposing plastics to vacuum and UV and wild temperature swings where they will degrade at one rate or another. There are some good ones now available that will last a while, but nothing one could construe as “permanent” for any kind of space station-like structure that never lands. Put the plastics on the inside, and put the glass and metals on the outside.

Based on nothing but existing materials and common sense, I’d suggest a thin aluminum pressure shell surrounded by a thick layer of ordinary pink fiberglass insulation, just like we use in our attics, paper backing and everything. Vacuum won’t hurt glass fiber or paper. Make it quite thick; the nominal commercial batt thickness is 6 inches, double-layer it if you need more.

This needs an over-wrap to protect it from UV. Make that out of simple textile-reinforced mylar (I’d consider using something woven of simple cotton yarns), aluminized on one side. Face the aluminized surface outward, and glue Velcro strips where geometrically appropriate when you fabricate it. Wrap this around your fiberglass layer, and overlap it over itself for securing with the Velcro. Nothing but aluminized mylar faces space and its vacuum and UV, and the mylar part is underneath the aluminum. If this degrades ever so often, it is quite easy to replace, and extremely light and compact to ship. Meteor hole? Stuff some more fiberglass batting into the hole.

On the inside is where you arrange your plastic furnishings that can help with radiation shielding effects. Although you’d get even better effects by arranging your water, wastewater and frozen foods as part of your shielding, which things you have to have anyway, although not enough for the whole hab; so just around the designated flare shelter space.

Inside, these plastics see no UV, no wild temperature swings, and no vacuum. Now you can use any appropriate plastic for any particular detailed purpose, exactly the same way we do down here on Earth. Why make things hard putting plastics outside in space when you don’t need to? (I gotta ask.)

Whatever you do, do NOT mount anything permanent to the inside of this aluminum pressure shell! Everything must be quickly removable, because you have to reach that shell quickly to patch punctures. There isn’t time for an EVA to do that, and besides, from the inside, the air pressure helps hold and seal your patch. Put your equipment and stores down the core, and put the people and their operating spaces around inside of the pressure shell.

As for windows, pick a transparency. But add an exterior metal (or composite build-up) shutter that you can operate remotely from the inside. When you’re not using the window, close the shutter. Your transparencies will last a lot longer in a very hostile environment that way. UV and meteoroid impacts are the threats. You can even multi-layer the shutter as metal foils and Kevlar. Just don’t expose the Kevlar to UV, make sure the metal layers cover up all the Kevlar. The shutter doesn’t need to hold pressure, vacuum won’t hurt these materials. If you never put much force on them, then brittleness in the cold is no problem either.

(What you would design for an article that lands is quite different.)

GW

Last edited by GW Johnson (2015-01-28 12:27:42)

kbd512 · 2015-01-28 15:23:56

GW Johnson wrote:

This is a very interesting discussion going on about materials of construction for a spacegoing habitat module. One should note that the requirements are light years apart for a hab that stays in space “forever” vs a hab that must enter atmosphere and land somewhere. Those requirements will likely never be resolved for some centuries yet.

There is no single technology that can make a habitat do all things. However, there are families of products, used in conjunction with each other, that have a synergy to them that makes their combined use suitable for variant requirements.

GW Johnson wrote:

What I don’t understand is insisting on exposing plastics to vacuum and UV and wild temperature swings where they will degrade at one rate or another. There are some good ones now available that will last a while, but nothing one could construe as “permanent” for any kind of space station-like structure that never lands. Put the plastics on the inside, and put the glass and metals on the outside.

If you read the article, they were thinking of exposing a carbon foam, selected for its light weight and very low thermal conductivity, to the thermal environment, not the PE composite (which, as Rob pointed out, was not really designed for the thermal environment of space). The PE composite forms a pressure hull, but it is inside of a carbon foam overwrap, where the foam can protect it from temperature extremes. The concept is much the same as the dual layer ET foam that both insulates the cryogenic contents of the ET and ablates as aerodynamic heating from drag increases the temperature during STS/SLS ascent. The ET foam is just one example of two different but complementary technologies that make lightweight cryogen gas cans possible.

GW Johnson wrote:

Based on nothing but existing materials and common sense, I’d suggest a thin aluminum pressure shell surrounded by a thick layer of ordinary pink fiberglass insulation, just like we use in our attics, paper backing and everything. Vacuum won’t hurt glass fiber or paper. Make it quite thick; the nominal commercial batt thickness is 6 inches, double-layer it if you need more.

Why is everyone so fixated on using aluminum? Thin aluminum sheeting is good for not only experiencing the direct effects of high energy ionized particles, but secondary effects from interaction between the ions and the atomic structure of the material they're being driven though.

GW Johnson wrote:

This needs an over-wrap to protect it from UV. Make that out of simple textile-reinforced mylar (I’d consider using something woven of simple cotton yarns), aluminized on one side. Face the aluminized surface outward, and glue Velcro strips where geometrically appropriate when you fabricate it. Wrap this around your fiberglass layer, and overlap it over itself for securing with the Velcro. Nothing but aluminized mylar faces space and its vacuum and UV, and the mylar part is underneath the aluminum. If this degrades ever so often, it is quite easy to replace, and extremely light and compact to ship. Meteor hole? Stuff some more fiberglass batting into the hole.

Correct. Overwrap required. More stuff made with aluminum?

GW Johnson wrote:

On the inside is where you arrange your plastic furnishings that can help with radiation shielding effects. Although you’d get even better effects by arranging your water, wastewater and frozen foods as part of your shielding, which things you have to have anyway, although not enough for the whole hab; so just around the designated flare shelter space.

As previously mentioned, NASA has people trying to figure out how to arrange cargo, food, and water to provide shielding.

GW Johnson wrote:

Inside, these plastics see no UV, no wild temperature swings, and no vacuum. Now you can use any appropriate plastic for any particular detailed purpose, exactly the same way we do down here on Earth. Why make things hard putting plastics outside in space when you don’t need to? (I gotta ask.)

You don't have to and you probably shouldn't.

GW Johnson wrote:

Whatever you do, do NOT mount anything permanent to the inside of this aluminum pressure shell! Everything must be quickly removable, because you have to reach that shell quickly to patch punctures. There isn’t time for an EVA to do that, and besides, from the inside, the air pressure helps hold and seal your patch. Put your equipment and stores down the core, and put the people and their operating spaces around inside of the pressure shell.

NASA is right there with you, GW.

GW Johnson wrote:

As for windows, pick a transparency. But add an exterior metal (or composite build-up) shutter that you can operate remotely from the inside. When you’re not using the window, close the shutter. Your transparencies will last a lot longer in a very hostile environment that way. UV and meteoroid impacts are the threats. You can even multi-layer the shutter as metal foils and Kevlar. Just don’t expose the Kevlar to UV, make sure the metal layers cover up all the Kevlar. The shutter doesn’t need to hold pressure, vacuum won’t hurt these materials. If you never put much force on them, then brittleness in the cold is no problem either.

Using metal and poking holes in the pressure hull for windows is not a good idea, but if you're going to do it anyway you might as well be smart about it. Good idea.

GW Johnson wrote:

(What you would design for an article that lands is quite different.)

More overwrap required.

Quaoar · 2015-01-28 16:05:12

kbd512 wrote:

Why is everyone so fixated on using aluminum? Thin aluminum sheeting is good for not only experiencing the direct effects of high energy ionized particles, but secondary effects from interaction between the ions and the atomic structure of the material they're being driven though.

More overwrap required.

Because it's lightweight, robust and cheep. You cannot have a passive shield against GCR even with polyethylene, unless you build a spaceship with two meters thick walls.
What you need is only a solar flare protected zone: a double aluminium wall filled with 20-25 cm of water ice is good. Ice it is also a very good heat sink for waste heat and a protection against meteorite puncture.
For CGR protection it will be better something like Boeing's 1500 kg superconductive mini-magnetosphere

http://arxiv.org/pdf/1406.1159.pdf

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