June 20, 2009
Inflatable Tower Into Space?
New Scientist has a report about a proposal to build an an inflatable tower into space.
Inflatable pneumatic modules already used in some spacecraft could be assembled into a 15-kilometre-high tower, say Brendan Quine, Raj Seth and George Zhu at York University in Toronto, Canada, writing in Acta Astronautica (DOI: 10.1016/j.actaastro.2009.02.018). If built from a suitable mountain top it could reach an altitude of around 20 kilometres, where it could be used for atmospheric research, tourism, telecoms or launching spacecraft.
Supposedly this is buildable from existing materials. Anyone think this could work?
Regards telecoms: My impression (correct me if I'm wrong) is that the spread of fiber optic cable and transmission rate increases of such cable makes satellite comm less important as compared to ground comm than used to be the case. Fiber optic cable is especially important for the internet because it offers lower latencies than satellites. People want their pages painted immediately.
What is the potential for a bigger space industry? The biggest potential I can see: cheap launch for a fleet of solar power satellites. Space manufacturing doesn't seem like a compelling benefit. It is far easier to do manufacturing down here. Whereas cheaper energy strikes me as far more valuable.
space manufacturing is actually a really compelling reason...there's tons of exotic materials that can only be made in zero gravity...particularly metal alloys featuring metals with different melting points/density/other properties...of specific interest: titalum, a superstrong, ultralight titanium/aluminum blend.
This does nothing for the real problem of getting into space: velocity.
What is far more interesting about static high altitude structures is that they can be used to generate electricity.
See the floating solar chimney for an example.
At 20km there is virtually no decrease in gravity - zero gravity manufacturing
would not work.
20 km is a bit less than 66,000 feet. It's slightly above Learjet cruising levels. It doesn't have much to do with space. On the other hand, if you could make e.g. a long, tough balloon with an opening down the center and use compressed air to shove a cheap pressure-fed rocket out the end of it at 20 km up and several hundred MPH vertical speed, it could make access to space quite a bit cheaper and easier. A rocket running 100 PSIA chamber pressure at that altitude can have roughly the same expansion ratio as a rocket running 1600 PSIA chamber pressure at sea level, plus rather light tankage and no turbopumps—not a trivial advantage.
"At 20km there is virtually no decrease in gravity - zero gravity manufacturing
would not work."
Nah, the idea isn't to do the manufacturing at the top of the tower. It's just to use the tower so that you can launch your rockets above most of the atmosphere. Having to operate at widely different atmospheric pressures limits rocket engine performance, and you can consume quite a bit of fuel coping with air resistance.
Launching at 60,000 feet will make getting to orbit a lot easier than just the mere height difference would suggest, because of those factors.
Imagine such a tower built to 200 km, like the authors propose! I haven't seen many Lear jets cruising at that altitude.
Brian Wang suggests using such towers as supports for J. Storrs Hall's space pier concept. A space pier at 200 km could sport an electromagnetic accelerator for routine launches into orbit for humans and material.
Just like that the cost of space development becomes affordable.
Long term benefits to humanity from cheap access to space are a million times more than from Obama's health care plan, and would cost less.
We'll also eventually start running out of easily accessible strategic materials, which are abundant in asteroids.
In addition, space would be an excellent place to relocate our most hazardous and polluting industrial processes. Confining nanotech assemblers to space -- while shipping down the end products -- might also be a sensible precaution.