Nicholas.Spies@H.CS.CMU.EDU (01/18/86)
Given: We are at the bottom of the gravity well of the Earth and also at the bottom of an ocean of air; the latter fact may help to overcome the former. The 14 lbs/in^2 pressure of the atmosphere [at sea level] is routinely used to generate lift; but could this simple principle be used to develop free-floating launch vehicles or large ground structures to gain a decisive advantage for a space launch? (I acknowledge that this is not an original idea as one of the first proposals for spaceflight involved evacuated copper balls, if I'm not mistaken, and also that some early rockets were launched from ballons.) It would seem that the ideal floatation medium would be superheated hydrogen constrained by a tough, thin Mylar-like film. A far safer but far more expensive next-best would be superheated helium. Superheating in both cases would produce higher pressures to counteract atmospheric pressure while reducing the mass/weight of the lifting gas, increasing lifting efficiancy. (Of course superheating would also complicate the design of the envelope; perhaps heat dissipation could be aided by introducing a small amount of steam that could condense on the inner surface of the envelope [or by taking off while raining!]). At any rate, it would seem that a giant donut-shaped lighter-than-air platform could, if large enough [how large?], carry a fully-loaded shuttle to a fuel-saving altitude from where it would be launched. Presumably "window-critical" launches could be carried aloft, above most weather, from where they could be launched on schedule. For the more defense-minded, such platforms could presumably reside indefinately in the upper atmosphere for a variety of survaillance and defensive purposes. Nearly-lighter-than-air structures might be a way of building a ladder to space because traditional wisdom about the strength of load-bearing members would be altered by the new distribution of the load between compressive and floating elements. Obviously such a structure would have to be designed to take advantage of the tensile strength of materials, which is typically many times greater than compressive strength. Wind loading would increasingly be a more important factor, which could be dealt with by distributing it to all other elements of the structure and ultimately the ground. If we were able to build a lasting tower 100 miles high (on a base perhaps 50 miles across) able to support a shuttle-sized craft would this realize much launch benefit? In the long term? What are the critical problems with these proposals? Nick Spies, Center for Art and Technology, CMU
space@ucbvax.UUCP (01/20/86)
We could get a good start just by climbing up existing mountains in South America, Africa or Asia. Imagine the top of Mount Everest flattened off for a space port (:-)!