NASA's new sleeping bags could prevent eyeball 'squashing' on the ISS | Hacker News Reader

NASA's new sleeping bags could prevent eyeball 'squashing' on the ISS

engadget.com

Why can't we tether the spaceship that carries the astronauts with a separate spaceship that carries the cargo (that will be only needed on mars) via a set of long, thin cables (to act as a counterweight) and spin the two around their joint center of mass? That solves the problem of needing a really large ship to make the rotation not uncomfortable, and allows for artificial gravity

Depends on the situation, though usually because of the force.

Spinning a spaceship around a point with a long cable, you obviously produce a (fictitious if you're pedantic) outward force, that's kind of the point. For that fictitious force to exist though, that very force acting on the spaceship must be counteracted by an equal and opposite reaction force provided by your cable, creating the action-reaction pair required for tension. This much is obvious. The problem arises when you think about how large that force is.

To generate an apparent artificial apparent gravitational acceleration of 1 G for the occupants, the entire ship must experience the same spin and thus the same acceleration. That's the source of the problem, the force you're counteracting is the same as the weight of the ship on Earth. What is being asked here is to hang a loaded spaceship from a building with cables. That might work for smaller spacecraft, whose mass is measured in metric tonnes, but it won't work for anything larger. You can get incredibly strong and light cables out there, but one capable of functioning in the space environment, light enough to launch, and strong enough to counter the tens of meganewtons of force required from it is going to be more difficult to find.

Not only that, but you need to consider the counterweight as well. Because of the cable, the tension force total is also dependent on the acceleration of the counterweight. Since launching a heavier counterweight than an entire habitable ship is probably out of the question, you'll probably need twice as long a cable and experience roughly twice the force required just to lift the ship on earth. Needless to say, that's getting a bit out of the realm of current space capability. Not to mention the immense size you'd need to make a ship like this for the situation to not cause immense discomfort.

Even 0.1G would do wonders with things like stopping blood pooling and moving co2

Two starships at 200t each linked by 10 cables would need 40kN each, a 5cm diameter cable, at 2.5kg/m a 1km cable, you'd need need 25 tons of cable, about 10% of the cargo capacity. You'd be well under 1rpm

https://www.engineeringtoolbox.com/wire-rope-strength-d_1518...

Starships when full weight some 1300 tons, which is what you'd want them to be at while waiting in LEO or in martian orbit. They'll be a little lighter in transit, but not empty, since they have a lot of other tasks and getting back to worry about. Working at 0.1 G certainly would be probably fairly possible. If you go with Kevlar, it's actually just 2.5 tonnes, very well within your cargo needs.

The required cables for something that small could very well be produced on Earth and launched up. It's still probably cheaper to just go with sleeping bags, and replicating Mars gravity is going to go on the "very difficult" side again, but yeah 0.1 G and other such very low gravity situations are certainly possible.

>That's the source of the problem, the force you're counteracting is the same as the weight of the ship on Earth. What is being asked here is to hang a loaded spaceship from a building with cables.

We're talking about 10,000-100,000lb (i.e. just the crew module) depending on mission profile and the craft in question. You can handle that and more with commodity wire rope and hardware. Whoever we're sending to Mars will probably appreciate having a useful tow rope on Mars anyway so it's probably wise to just use a boring old steel cable rather than something that weighs 3lb but isn't up to the rigors of surface use. Remember, we're using "needs to go into space" margins here, not "overhead lifting on earth in a jurisdiction where OSHA matters" or "what makes Redditors sleep at night" margins here so you're not going to need a behemoth of a cable. Furthermore, you don't even need to generate 1g, just enough to not cause health problems and greatly simplify craft design.

Yeah something that small is going to be fine. But the ISS will not be. It's 440 metric tons, generating 4.4 MN of force on a cable. That's not going to spin.

And you're sending something to Mars here. In the ideal case we'll be sending six worth of supplies at the same time per person per ship. The amount of people permitted by NASA's guidelines on long-term habitation on a ship based purely on volume range from 1 for smaller ships to 30 for something the size of Starship. Hauling everything they need is not going to be below 50 metric tonnes by any means. We can probably spin as much as we like here, near the Earth, but anything further away is going to have ropes the breaking strength of which is again measured in meganewtons and the width of which is going to be around half a meter. Making that out of steel for the kind of cable you'd need for comfortable spinning (~1 rpm, 1.6 km of cable) is not going to space any time soon.

At the very least 6 months of food is required for the crew module, or some complex procedure of periodic de-spin & rendezvous with a cargo vessel. The kinds of missions NASA has been planning are 30 months in overall length if everything goes well, though 24 of that is not required to be accessible during transit. Spinning again in ĺow martian orbit is going to be quite feasible, once you jettison all of your life support and such and instead do very frequent cargo stops.

Most people are giving technical explanations. But actually its very non-technical and deliberate. For some historical reason astronaut office space biology gained primacy in the NASA after Apollo. The reason they never seriously considered artificial gravity is because THEY WANT TO STUDY MICROGRAVITY. The whole goal of station is to solve micro-gravity research and human medical research is the most important of those.

Its not a goal of the station to figure out how to most efficiently keep humans alive in space. Its simply a great reason to stay in LEO and do research for 50-100 years.

There is a reason many space advocates since the 60s have pushed for artificial gravity research and almost nothing has been done. Its political. The technical problems are approachable and solvable but it has not political base unfortunately.

This is one of several things I hope to see if SpaceX succeeds in crashing the cost/kg to orbit. I think it's difficult to overestimate how hamstrung our space program has been by the sheer expense of mass. New technology was certainly always going to be necessary, but there is so much that would be easier and/or possible if we could just get mass to orbit and weren't counting every gram.

At current prices, it's hard to justify lifting dead weight just to spin.

We can. It's been written about for decades. It's just expensive.

But why is it hard or expensive. These spacecraft can already withstand earth gravity, because we built them here on earth and they didn't collapse during construction. They typically already have lifting points to lift them with a crane too.

Cable is cheap and light.

Getting the whole lot spinning can be done very slowly over many days with the same ion thrusters that are used for stationkeeping. Total delta-V isn't very high. Total fuel used isn't very high either.

The only disadvantage really is that you lose most of the benefits of zero-G. for example, long running experiments requiring zero G. You also start to need walkways and paths. The ceiling of rooms becomes dead unusable space. etc. Docking new spacecraft requires stopping the spinning, which takes many days. Comms antennas and solar arrays get more expensive.

I actually agree with your underlying urge: space travel should be pleasant! But what separates out engineering from science is essentially economics. In science we don't know the scale a discovery will make until we've made it. Before nuclear weapons how could we know that studying these tiny atoms would essentially end total war between major powers. With engineering smart people looked at the costs and said something like:

> We're 99.9% sure this is going to be >2x the alternative and it's not worth it.

Just off the top of my head costs that go up:

- Instruments (lol, our cameras now need faster f-stops)

- Every need now needs to be met during the spinning state and the non-spinning state. (lol, Frank you used the gravity toilet in the middle of the night but we stopped the spinning state yesterday)

- Harder to maintain, since crew needs to lose angular momentum as they travel along the bridge and they can't toss things around as easily.

>The only disadvantage really is that you lose most of the benefits of zero-G. for example, long running experiments requiring zero G. You also start to need walkways and paths. The ceiling of rooms becomes dead unusable space. etc. Docking new spacecraft requires stopping the spinning, which takes many days.

For a one way trip to "elsewhere" none of that matters much.

We'll probably see this approach investigated more fully when a one way trip to elsewhere seems more likely.

TO dock you have to spin down and then spin back up again? It's a hard problem.

We could also use an inflatable module with a centrifuge inside it. The smaller diameter would make coriolis forces worse and walking would be tricky, but, at least, your body would spend some time under some gravity.

Putting it inside a large inflatable makes it easier to pack and solves a problem with rotating seals and the need to stop rotation when a spaceship is docked (because an internal part is rotating, but the rest of the craft is static). One issue that it doesn't solve is that it'll doubtlessly pass some vibrations and some oscillations to the rest of the craft, so any microgravity experiments will need to account for that.

But if you're in an inflatable you're no longer in a vacuum so you'll have air friction to deal with (and thus constant propulsion) right?

You'll need an electric motor to spin the centrifuge and a flywheel to store the momentum so the station doesn't rotate. Ideally, it'd be two separate motors and a clutch between them that acts in a catastrophic failure to prevent the whole station from rotating itself.

The issue is probably the strength of the structures involved.

Starship weighs 1300+ metric tonnes. Accelerating to earth gravity, the cable will have a tension of 1.3 MN. On the other end the counterweight has to be of roughly equal mass by way of not being able to launch anything heavier (so prob. another starship), meaing that the barycentre will be roughly in the middle, and the counterweight applies a second 1.3 MN. The total tension the cable is under is going to be 2.6 MN, well outside any single cable today. Taking a comfortable velocity of 1 rpm, and calculating a radius, we get a cable 894 meters long. This is right in the comfort zone as far as difference in force over your body and disorientation from spinning are concerned. Our strongest cables, made of Aramid (which degrades too quickly because of radiation, but ignoring that) is going to be 58 cm and have a weight of 2.2 metric tonnes. Since we actually need twice the cable, it's actually 4.4 tonnes. A similar cable made of carbon fibre or another such element will give us a launch weight of 430+ tonnes (close to the mass of the ISS), which rules basically anything but polymer fibres out. The R&D funding that would have to go into developing the cabling and methods of shielding it and preventing MMOD, solar, or GCR degradation is astronomical. It's way cheaper to just make a special sleeping bag or two.

I agree it's impractical, but I believe you're double counting the force on the cable. Each end of the cable pulls with 1.3 MN, which means that the cable itself can be in static equilibrium (in the rotating frame of reference). The same is true if you hang a 1.3 MN space station from the ceiling. The space station pulls down with a force of 1.3 MN, while the ceiling pulls up with a force of 1.3 MN.

That's probably a reasonable conclusion. It does happen to be totally overshadowed by my bigger mistake, which is an order of magnitude. Repeating the calculations using my physics CAS today:

Starship mass: 1.3·10³ kg Starship weight: 1.3·10⁷ Newtons

Converting that into something reasonable, it's 13 MN, not 1.3. A Kevlar fibre cable will be 22 tonnes, a PE one 9000 tonnes, and a carbon one 2200 tonnes. I wouldn't like to even imagine steel. And these are just with a breaking strength of 13 MN.

Not the most reasonable, though obviously we've held up things like Arecibo in the past. Using multiple smaller cables would be the optimal solution and what we would go with, since a single cable is >1 meter in diameter in any case. The mass doesn't get any smaller like that, though, so it's not a consideration we'd need to make.

I don't think you'd need full earth graffiti to minimise the negative health effects of microgravity. Probably half or so would be enough. Just make sure people don't try to jump lol

Low gravity will always have health effects. If you plan on returning to the Earth and have a very short stay, 0.5 G is probably a massive improvement over 1 G, especially if you keep doing exercise. For a martian transfer, you'd acutally only need 0.38 G as they'll be losing their bone structure to Martian gravity either way.

Funny thing actually, a person born on Mars could probably never walk on the Earth without years of intensive physiotherapy.

Can't we use multiple cables then? There are ships that can lift over 10,000 tons with their cranes. Some of these are decades old.

Yeah, we can. The issue is that tensile strength is measured as pressure, as force per area. Splitting a one meter cable into 10 cm cables is certainly possible. Those are half the length of your normal school ruler. You will need 100 of them, though, and since the area and length are the same, the volume, and by extension the mass are the same. It's certainly easier to manufacture, but it doesn't change the calculation. Cranes capable of lifting metric tonnes are giant. Just the cabling alone can weigh as much as a small skyscraper. That just isn't going to space.

Sleeping in zero G. Another issue is that CO2 won't disperse. IIRC from a discussion on Henry Spencer's sci.space, there is a fan at every sleep station.

Why won't CO₂ disperse there? I'd expect diffusion to be sufficient to keep the CO₂ concentration fairly uniform throughout the station.

Diffusion is definitely not sufficient--natural convection is usually sufficient to do this on earth, but gravity is a requirement for most natural air convection. Interestingly, a surprisingly large percentage of a spacecraft's power draw is spent just on air circulation (other conditioning adds as well).

I think it’s more about local pockets over temporally short periods of time. Gravity probably plays a role in kicking off the dispersion process by moving them from their initial place of production (where you exhale) so it doesn’t just cluster there.

Gravity definitely plays a role in convection, which is the main form of dispersion. The air one exhales has different composition — more CO2, more water — which means it has different buoyancy. Usually, this means the parcel of air rises here on Earth, but falling of your face is fine too. No gravity means no convection. Without wind to cause turbulence, mixing is really slow, leaving molecular diffusion as the only process. Remember, that’s random, and CO2 will still accumulate near the point source with a Gaussian distribution.

I'm curious about nocturnal cerebral edema and its potential relation to Alzheimer's and dementia. IIRC, some of the brain's cells may change size to accommodate what could be considered a "flushing" routine to remove detritus but tangles of tau and/or ABeta don't want to go. Perhaps exercise and/or spaceflight could dislodge them.

Is there a good list of major health issues associated with space flight?

Would be interesting to see what still needs to be solved for multi-year stays.

https://en.wikipedia.org/wiki/Effect_of_spaceflight_on_the_h...

Not comprehensive, but link between radiation - viruses - cancer here

https://www.ted.com/talks/madison_campbell_viruses_in_space_...

ISS doesn’t have much radiation. It’s not the moon.

Yeah, the ISS is barely even in space. You can go that far on a train before lunch.

> Dr. Levine discovered SANS by flying cancer patients aboard zero-G parabolic flights. They still had ports in their heads to receive chemotherapy, which gave researchers an access point to measure pressure within their brains

what

I would have loved to be on whatever panel read and approved that grant. Obviously this is a brilliant methodology and a wonderful science hack, but how stoned did someone get that 'zero G cancer patients to tap their brain fluids' came out.

> vacuum cleaner-like suction device is then activated that draws fluid toward the feet, preventing it from accumulating in the head.

How does that even work? The liquid is accumulating inside the head. How would pulling a vacuum (presumably outside the body, in the sleeping bag) help? If anything the vacuum would force liquid to the head by squeezing liquid from the body.

They've been experimenting with this on the Russian side of the station for years. Their version is semi rigid and creates low pressure around the astronaut's legs so the natural pressure in the body and the air pressure of the ISS on the upper body and face squeeze the blood into their lower extremities away from where it pools naturally in micro gravity.

http://www.astronautix.com/c/chibis.html

https://blogs.nasa.gov/ISS_Science_Blog/2015/06/02/rubber-va...

I guess it sucks on the "skin balloon" by creating low pressure around the lower body, thus "inflating" the legs (think swollen feet).

But I'm a little surprised that would work. Another way to look at it, would be that the higher pressure on the head and torso "squeezes" fluids down, like a water balloon - squeeze one end, and liquid goes to the other end?

Create low pressure around the legs, they puff up with blood which means less blood in other parts of the body. If you need a demonstration then google “penis pump”

Iirc there is a lot of debate on the minimum g level required to avoid negative effects. Spinning people tends to make them uncomfortable and nautious.

However, I'd be quite curious if the g level is actually very low. You could have a small gently rotating section of a station.

The tough part with making it small is the smaller the torus or device the larger the gradient of forces along a riders body which can be disorienting. Any useful G level and comfortable size would likely be larger than any existing module.

  > small gently rotating section of a station

A small rotating section near the center would have extremely uncomfortable tidal effects. You want to be as far as possible from the fulcrum to reduce the tidal effects.

You don't need humongous modules for that. Just take two normal ones and tether them together with a long strong wire.

You can probably just lie down and sleep though. The tidal effects would be interesting, but I'm not sure they'd be uncomfortable. Walking would be more difficult, as you'd feel you are about to fall on your face (or back) but I don't think it's something one wouldn't be able to get used to.

Wouldn't work with the 4.5 m size limit of the current ISS modules, it's barely doable with a Starship-wide module, but seems totally doable with inflatables. Bigelow was designing 12m+ wide modules and that was a limitation of the rocket fairing that was launching it. With, say, Starship, the module could be much wider.

How fast does it really need to spin? I'm not sure there have been any studies on 1/128g or less. In a 4.5 meter section 1/128g would only be 1 rotation per 30 seconds.

The issue is that at the average height of the astronaut the rotation speed at their head would be half of that at their feet given the 4-5m modules we can launch.

I don’t know what is the maximum difference that would be tolerable but it’s not 2x for sure.

So to get it down to single digit % you are looking at 200M+ or so in diameter.

If it’s just for sleeping and liquid pooling at the back won’t pose a health risk then if they are lying down the diameter can be much lower but you are still probably looking at 15-20M which might be possible with inflatable modules I think 3.5-4X expansion would be quite possible with the existing inflatable modules we have.

A 4.5 meter section rotating at 1 rotation per 30 seconds would likely suffer very noticeable Coriolis effects.

Think iron lung, not shrink-wrap.

There are veins for other liquids, just like there are for blood. The liquids don't lie around everywhere under the skin.

This is endemic of the problems at NASA. The concept is likely sound, and the problem likely needs to be solved, but doing it in such a tiny and insignificant way.....spin the spaceship, dont vacuum the space people.

Spinning the spaceship is a pretty hard problem. There's all sorts of constraints on how fast you can spin it for a given radius, and you have to spin it fast enough to be useful. The end result is that you're looking at a pretty huge spaceship that will take a lot of power to start spinning. Its not unreasonable to look at a smaller-scale solution given a world of limited budgets.

Scott Manley did a video looking at this, it’s a good and informative watch:

https://youtu.be/nxeMoaxUpWk

The gist is that is actually doable at the same(ish) scale as the ISS. Bigger is better but we can do it at a radius as little at 40m.

Is the problems of nasa that they don't have an unlimited budget? Why make a experimental rotating artificial gravity spacecraft when a fancy sleeping bag will do the trick?

We should experiment on rotating artificial gravity anyway, if only to expand our knowledge of space colonization:

https://www.nasa.gov/careers/our-mission-and-values

> Mission: Lead an innovative and sustainable program of exploration with commercial and international partners to enable human expansion across the solar system and bring new knowledge and opportunities back to Earth. Support growth of the nation's economy in space and aeronautics, increase understanding of the universe and our place in it, work with industry to improve America's aerospace technologies and advance American leadership.

But I agree that it should be a completely different mission than the International Space Station.

using centrifugal force would require a complete redesign and billions of dollars. Whereas the ISS space station is for a few people for a few months and mostly for research.

sophisticated space stations would have to wait untill a turning point in profitability is reached. Space elevators are still in the realm of science fiction and are on the edge of theoretical feasability

Agree this is a sound solution for now however the the ISS is currently only approved for service until 2024 (this will clearly be extended) and plans need to be made for its replacement.

With the (moderately) high probability that the SpaceX Star Ship will succeed and go into active service in the next few years the cost to orbit is going to drop significantly. There is an opitunity soon to rethink what a space station is. Realistically the internal area of a Star Ship could make a space station in the same vain as ISS, and would be “cheap”. But we could also feasibly construct a rotating station with the use of Star Ship.

Space is about to undergo a transformative change in how people approach building in it.

So far, most space endeavours are related to science in some way. which is problematic because there is little to no return on investment. also, everything we have and consume is on earth. I can't think of many products which are low in mass but extremely high in value and could benefit from the only properties of space we control right now; weightlessness and orbits.

To me, cheaper rockets could only help building a future space elevator which would reduce costs significantly but we would still need something to do in space.

So what do you think the first economic incentive will be to enrich society?

Sierra, Axiom, and Blue Origin are all working on commercial successors to the ISS.

Axiom's first modules will launch 2024ish and initially be connected to the ISS.

Spinning the ISS to achieve artificial gravity would be possible if the ISS had been designed for that from the beginning, but as far as I know it wasn't, so they'd have to either replace the whole thing or construct an addition that spins.

I'd like to see ISS greatly expanded now that access to space is getting cheaper, but given the constraints, designing vacuum sleeping bags is reasonable. (Also, expanding our range of techniques to limit the adverse effects of zero-G is useful in the long run. Ideally we won't have many people who need to be in zero-G for extended periods of time even if travelling to space becomes routine, but still the knowledge is good to have just in case.)

The whole point of the ISS is that it provides a stable zero-G environment for experiments. Spinning it would be counter-productive.

It's possible to spin on section and not another. Vibration would likely be an issue, but already is.

How to walk from fixed to rotating section then?

Via the hub.

https://yewtu.be/watch?v=0iiXUeil5fQ

https://yewtu.be/watch?v=nxeMoaxUpWk&t=11m6s

How would one dock with a rapidly spinning spaceship?

Elegantly

https://www.youtube.com/watch?v=0ZoSYsNADtY

or heroically:

https://www.youtube.com/watch?v=a3lcGnMhvsA

One would dock to the axis of rotation, I would think, spinning up your spaceship to match station spin?

Ah, from my layman's perspective that seems to makes sense. A spinning top has an axis that doesn't move, so dock there, but if the people are to enter, the docking ship needs to spin at the same speed or they'll feel the difference immediately.

Thank you!

The docking port would need to be coaxial with the axis of rotation.

a docking station at the central point that the ship rotates around

Archive link for anyone irritated by engadget's cookie settings nightmare:

https://archive.md/z4czx

IMO the problems of living in space are so numerous that unless we can seriously come up with a good general solution for artificial gravity we probably shouldn’t even bother with the idea of being in space for anything longer than a flight to some celestial body. Why has it taken so long?

I know space is at a premium on a space craft. But wouldn't it still be simpler just to have a sleepingbag that rotates around a center by the upper torso? Seems overengineered to sleep in a vacumbag.

Maybe I've misunderstood your idea, but it seems to me that a vacuum sleeping bag is less complicated than a sleepingbag/bed that constantly rotates its occupant

well a vacum sleeping bag is a motor plus more (and the bed). A rotating bed is just a motor (and also the bed). But yeah it's probs not any better.

That would push some down into the feet but also accelerate some up to the head. In addition that's a lot of space in a pretty cramped area. Then you have to mount it so it doesn't induce vibrations on the space craft which is an issue they already fight with the existing exercise equipment. On top of all of that you're creating pretty sizable gyroscopes that you need to spin up and down requiring a counter force from somewhere.

I guess you could say staying in space long enough gives you SANS vision.

The solution that sprung in my mind was akin to an artificial gravity simulator ring, slowly spinning beds arranged like a flower petal.

That works, but the necessary radius is larger than anything we have in space right now.

The vestibular system would be so confused you'd quickly develop motion sickness. Kids with low-viscosity fluid find the Scrambler at the carnival fun, adults can have fun for a while...but nobody I know of falls asleep on it.

Here's a cool page discussing appropriate radii and spin velocities for artificial gravity:

https://www.artificial-gravity.com/sw/SpinCalc/

TLDR: A space habitat with artificial gravity should have the rotating section on a cable or truss at a radius on the order of 100m or more!

>by the time NASA is ready to go to Mars

Don’t hold your breath.

Technical issues aside, why would they even want to?

For NASA in particular, they'd be interested in doing science locally, establishing multiplanetary infrastructure, national pride reasons and help people think that the human race is making some kind of forward progress, and to motivate young people to be interested in science. Basically reasons that are similar to the reasons why NASA does anything.

For people in general, I'd say people might want to go to Mars for mining (maybe direct mining of Mars or more likely to serve as a refueling spot with a shallow gravity well for mining operations in the belt), real estate speculation, science, low-gravity sports and entertainment, retirement communities for people with mobility issues, to establish new communities according to their rules rather than working within the established systems of Earth, tourism, curiosity, a sense of adventure, and so on.

Humans are still generally better than just having a robot there because they're both more flexible and capable of problem solving. Maybe for the same money you could get enough robots there to make up the gap but sending humans to Mars is sexier and attracts more money than you could get for the robot missions. Then even if we never actually go 'preparing' to go to Mars attracts ongoing money for studies on the ISS and for sending robotics missions.

I’ll go to space when there are mattresses and the ice cream isn’t plaster.

Really the solution is to just send robots.

Remind me of Misha who goes practically blind during his trip to Mars in series Away.

Reply on news.ycombinator.com