HPM@S1-A (12/08/82)
From: Hans Moravec <HPM at S1-A> My friends at Livermore have thought about this, and have come to an even nicer variant - namely the metal foam can have its cells filled with VACUUM. If you do the calculations, you find that almost any meterial is easily strong enough under compression to make a flyable vacuum balloon; the practical problem is simply buckling of the skin. Foam with the appropriate bubble size solves the problem.
emil (12/09/82)
Hate to put a damper on foamed metals, but ...
According to Curtis Watts, an aerospace/materials technology comsultant,
("Space Factories a Long Way Off", High Technology Nov/Dec 82 pg. 23),
"tests showed that metals solidified in space form imperfect spheres that would have to be ground for use as ball bearings; the process is better done on
earth. Similarly, metal foamed in space proved to be *nonuniform* ."
Areas that still show great promise include:
* Continuous flow electrophoresis (to obtain highly pure pharmaceutical
products)
* Single crystal devices for electronics or electro-optics from silicon,
gallium arsenide, mercury cadmium telluride, and other compounds.
* Exotic glasses for high-index-of-refraction lenses, fiber optics, & lasers.
* Composites for high-strength magnets, and other novel or high-purity
metals or alloys.
* Unusually shaped parts, including high performance turbine blades.
These are just a few ideas, lets hear of others.
Emil Rainero
P.S. Its the only way NASA will ever get to build a manned space station.REM@MIT-MC@sri-unix (12/09/82)
From: Robert Elton Maas <REM at MIT-MC> You say metal foam can be made, just it isn't uniform? That's encouraging, better than if it couldn't be made at all due to lack of surface tension. How badly nonuniform is it? Bad enough to prevent use for delivering metals to Earth by floating the foam down? (It would seem a slight nonuniformness would merely mean the foam isn't uniform in density, thus would be heavy on one side, and thus sink with the heavy side downward. An extreme nonuniformness would however cause the lightest part to be too weak to hold under stress while the heaviest part would come crashing to Earth. Which is closer to the actual state of nonuniformness?) Could it be made more uniform in a subsequent experiment by bubbling it more carefully, or does it inherently push toward a particular nonuniform state such as a gradient of density from the center to the outside of the mass of foam? P.s. thanks for providing the first info about the result of the experiment.