Text File

Aucbvax.5508 fa.space utzoo!decvax!ucbvax!space Sat Dec 19 03:34:35 1981 SPACE Digest V2 #64 >From OTA@S1-A Sat Dec 19 03:27:44 1981

SPACE Digest Volume 2 : Issue 64

Today's Topics: Skyhooks Nuclear Power Plant vs. SPS for Laser Launch System Power Laser launches Spaceports Spaceports Momentum ----------------------------------------------------------------------

Date: 18 December 1981 18:05 est From: Tavares.Multics at MIT-Multics Subject: Skyhooks To: Space-Enthusiasts at MIT-MC In-Reply-To: Message of 18 December 1981 06:03 est from Ted Anderson

I assume you're suggesting building a hollow pyramidal skyhook, 200 meters wide at the base and meeting at the point? It seems to me that this would ADD strain to the structure. For instance, small to medium-size radio towers come to a point at the bottom just so wind flexing won't tear them apart. I should think that the magnitude of possible side forces on a skyhook structure would be much worse.

------------------------------

Date: 18 Dec 1981 17:39:41-PST From: A.exp at Berkeley Subject: Nuclear Power Plant vs. SPS for Laser Launch System Power

I don't like radiation. Why not use an laser SPS instead of the nuclear power plant for the laser-launched shuttle? The power could be beamed to Earth and stored, then fired from Earth based lasers during the first part of launch to reduce thermal bloom while the shuttle is still deep in the atmosphere. After the shuttle gets out of the atmosphere it could be illuminated directly by the laser on the SPS, saving storage costs on the ground and allowing you to get away with fewer lasers on the ground since the reduced ground cost would allow decreased efficiency during part of the boost.

If only ground-based lasers are used, the thermal bloom must be fought even after the shuttle itself clears the atmosphere, but for an SPS laser, after the shuttle gets through the denser layers there is a corresponding reduction in the thermal bloom effect, so you would need only one laser on it. Also note that nuclear power plants have had the problem that they are out of commission .2 to .5 of the time.

------------------------------

Date: 19 Dec 1981 00:47:53-EST From: dee at CCA-UNIX (Donald Eastlake) To: space at mc Subject: Laser launches

If you need a lot of power for just 90 seconds, can't you accumulate it in flywheels or something over a longer period of time?? (Maybe a flywheel at each of multiple lasers?)

------------------------------

Date: 19 December 1981 03:10-EST From: Robert Elton Maas <REM MIT-MC AT> Subject: Spaceports To: Hans Moravec at CMU-10A cc: SPACE at MIT-MC

Even if the mass and complexity of the 600 km linear accellerator is the same as the rotating&dipping cable in orbit, the l.a. is much easier to build. Why? (1) It can be built and tested incrementaly. Each piece can be installed in sequence and suborbital test flights of cheap passive material (dirt, rock) can be made. When enough sections are installed to achieve orbital velocity, it becomes operational. The dipping cable, on the other hand, must be built and installed as one big piece somehow. (2) The cable must be put into space somehow whereas the linear accellerator can be installed by conventional means such as bulldozers cranes trucks etc. Thus the linear accellerator can be started now without needing the shuttle whereas the dipping cable will DETRACT from shuttle payload capacity by diverting capacity from normal use to cable use, and can't be started anyway until the shuttle is operational. Thus I don't think the cable should be done until after we are well out into space, whereas unemployed construction workers could be assigned to the accellerator in 1982. We could use the shuttle for delicate equipment and people, and the linear accellerator for bulk materials. (I'm not sure whether we should do the Earth-based accellerator now and use it for bootstrapping ourselves into space industry, or go instead with the moon-based accellerator which WILL need a few shuttle payloads to get it installed but possibly be more effective due to lower moon gravity and lack of atmospheric friction.)

------------------------------

Date: 19 December 1981 04:22-EST From: Jerry E. Pournelle <POURNE MIT-MC AT> Subject: Spaceports To: Hans Moravec at CMU-10A cc: SPACE at MIT-MC

Galombos proposes a spaceport, cnsisting of a large mass in high orbit that can lower a cable about 400 km long; hook onto a suborbital mass at Shuttle; and up it goes. The energy in the spaceport is restored by ion engines and solar arrays.

------------------------------

Date: 19 December 1981 04:25-EST From: Jerry E. Pournelle <POURNE MIT-MC AT> Subject: Momentum To: HPM at S1-A cc: SPACE at MIT-MC

AHA! You want to use Earth's rotational energy for space launches. YUou technologists never care about the environment at all. What about all the creatures that can't survive longer days and nights?

------------------------------

End of SPACE Digest *******************

----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen <jgoerzen@complete.org> of http://communication.ucsd.edu/A-News/

This Usenet Oldnews Archive article may be copied and distributed freely, provided:

1. There is no money collected for the text(s) of the articles.

2. The following notice remains appended to each copy:

The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.