SpaceX is launching an inflatable space habitat
techcrunch.com
techcrunch.com
Some details and photos of the BEAM here:
https://en.wikipedia.org/wiki/Bigelow_Expandable_Activity_Mo...
http://bigelowaerospace.com/beam/
Kudos to the team at Bigelow for making it this far. Let's hope for a successful deployment. Inflatables have often been assumed to be how we'll build habits off planet. They're light but durable and could soon be deployed on the moon with our current technology to act as a semi-permanent base. Imagine a dozen of these tied together. The lift cost would be a fraction of what a 'hard' habitat would cost.
Or from less ambitious perspective, one of these acting as a commercial space hotel. Space tourism works better with a destination.
For humans, a habitat should replicate earth's environment. Gravity is the first thing that comes to mind, but there are other things it should provide.
I hope in the near future we work on actually building/sending habitats in space with the goal of actually living there, and not only for scientific research.
Then what is the point of having the habitat in space in the first place? Should we block off the windows, too, and replace them with posters of the side of some terrestrial apartment? Hamstring the solar panels because the atmosphere would block a lot of energy?
Living in space should be different than life on earth. Humans need some things to be similar to survive, so give them those things - possibly including some time in gravity - but we don't need a few more square feet of living space equivalent to a vacant lot.
On the other hand, the word "habitat" literally means the natural home of an animal or plant, and a gravity-free inflatable balloon in space is about as far from the natural living space of a human. It's going to be a long, long time before anyone can recreate Earth-like conditions in space.
Living in zero gravity tends to be very bad for long term health because bone and muscle mass start disappearing.
Radiation shielding is a huge problem. Inflatable habs provide almost none, so they're dangerous in LEO and potentially fatal further out.
And then there's danger from micro-debris.
So inflatables could be good for short trips - space hotels, especially - and for extra storage. But they're really not a solution for long-term occupation.
Or there's robotic in-situ water mining - Ceres has a shallow gravity well and probably has as much water as Earth. Easy? No, but space is always going to be hard.
What they actually propose to do is inflate the walls, then store water and supplies on the interior walls.
But if you're using water for radiation shielding and you then dedicate it to some other purpose, you no longer have radiation shielding.
Thanks for the recommendation for The Millenium Project, jasonpeacock, I'll check it out. :-)
Of course, there are questions to answer about safety, shielding against debris and radiation protection, but that's the point of doing the research. I love this kind of stuff. It serves to remind people that space travel isn't just launch vehicles. Part of, as you say, providing a place in space for humans to live, is providing spacecraft that aren't utterly cramped.
The advantage is actually in mid-sized structures where you can more easily compact them for transport where rigid structures are sent up in a single piece for strength.
PS: This is also why you need buttressing around above ground pools. For comparison 1ATM = 33.9 feet of water. Above ground pools rarely go above 1/3 ATM at there base. Granted, they are also not made out of Kevlar, but the same basic problems apply in space.
Factor in each of size, cost, and deployment complexity, and it's clear many feel that inflatable structures represent huge potential wins.
Besides, it's not like you actually need to build single, huge volumes. Space-based habitats built of multiple, smaller linked structures makes more sense, anyway, as it enables module isolation in case of failure.
From a safty standpoint you want modular structures. But, you also want to minimize the areas directly linked to space. Thus you end up with something like a nuclear submarine vs an ever expanding ant hill.
Remember apartment builds give every room a view, but that's high risk in space. You can also reuse walls, between areas to cut down on mass without compromising if there is a leak.
To me, "it's inflatable" is a good temporary hack to get something up while we are still early in the space robots age.
Make it big enough, and vaguely cylindrical, and you could spin it up to provide simulayed gravity - you'd just need internal webbing to prevent it bulging from centripetal forces.
This all adds mass of course, but it still be lighter and more compact than an equivalent rigid structure.
But some thought experiments about enormous pools - ponds, really - make me think that you're correct.
Indeed, looking it up, in a sphere, the stress (in units of pressure) is equal to (pressure x radius) / (2 X thickness). In a cylinder, it's worse - axial stress is the same as a sphere, but hoop stress is (pressure x radius) / (thickness)! You also have to think about increased stretching in the hoop direction compared to the ends of a flat-plate cylinder, which should probably be a sphere or complicated ellipsoidal shape to best deal with the stress.
Applying these equations, an ideal steel (assume an alloy with tensile strength 700 MPa) sphere with 1cm thick walls would have a maximum radius of 138.2m. A cylinder would have half the radius. Using Kevlar (tensile strength 3620 MPa) increases the radius by 3.62.
Doubling the thickness doubles the allowable radius but also increases the mass of our sphere from an already staggering 136 metric tons (3 Falcon Heavy payoloads) to an astonishing 546 metric tons, or more than 10 Falcons Heavy.
Kevlar is, of course, lighter than steel by about 5 times, but that many tons of Kevlar will not be cheap. That's about 0.5% of the total world annual production of the stuff!
We won't be going up to inflatable planets anytime soon.
I was really excited to see Bigelow's ideas here, and have enjoyed seeing stories of their test modules floating around in orbit. It seems to make a lot of sense if you want something that transports small, and grows big when it is deployed (no joke intended). I remember thinking it was like one of those "pop up" tent trailers you see at the campground. Easy to transport but very spacious and useful once set up.
Still, it seems like the way of the future for human living spaces. I visited the Air and Space Museum in DC and the Skylab was amazingly roomy compared to ISS modules.
Expanding: Space craft and stations should be modelled on the spittle bug's nest, a cluster of bubbles.
These metal cans are a conceptual hold-over.
Standing ovations for NASA!
Sorry.
I'd also be curious how the tether would avoid getting cooked by the rocket exhaust. I think a long mast, putting the riders in front of a large mass of fuel, would be much simpler.
But you're right, it is a lot easier to design an ultra-light, super-strong tether than a giant mast.
Another free benefit would be that on a change of acceleration, angular momentum would be conserved. Rotation would increase or decrease to keep the acceleration felt by the occupants approximately constant!
http://james-camerons-avatar.wikia.com/wiki/Interstellar_Veh...