archive: SETI Sagan: Need help again!/ Future of space travel.
SETI Sagan: Need help again!/ Future of space travel.
Larry Klaes ( lklaes@bbn.com )
Fri, 05 Feb 1999 14:02:03 -0500
>X-Sender: waw@clarke
>Date: Thu, 4 Feb 1999 19:20:39 CST6CDT,3,-1,0,7200,10,-1,0,10800,3600
>X-OldDate: Thu, 4 Feb 1999 17:20:25 -0800 (PST)
>Sender: carlsagan-owner <carlsagan-owner@craigerware.avalon.net>
>Reply-To: "Carl Sagan List" <carlsagan@craigerware.avalon.net>
>From: Bill Wheaton <waw@ipac.caltech.edu>
>To: Teresa Richards <richards@mind.net>
>Subject: Sagan: Need help again!/ Future of space travel.
>
>Hi Teresa & All,
>
>This question came up about 6 months ago on the ACC list, and I wrote a
>few paragraphs, which I will just reproduce here. This is all IMFLHO (in
>my fallable & limited humble opinion), obviously. I've made a few
>corrections in the original, in particular the velocity numbers for
>fission and fusion were too conservative, due to a mistake I made.
>
>---------------------------------------------------------------
>On Mon, 5 Oct 1998, Bryan Jackson wrote:
>
>> I was wondering today in my mad ramblings, and had some questions. Are
>> they are new type of new purpolsion systems for space, and how do they
>> work.... I know about ion, and solar sails and understand them but are
>> there any others? Also is there any plans for us to build a "hanger" in
>> space so we can get somewhere other than LEO? Is there any plans for
>> commercial industry to start space tourism?
>
>There are speculations and hopes, but no revolutions you can count on. I
>think ion drives powered by nuclear fission are a sure thing, just waiting an
>urgent need and some technological development, to reach velocities of the
>order of 4% of the speed of light, c. Fusion powered ion drives could get us
>up towards 15% of c, with a lot more uncertainty about when and exactly what
>the limits will turn out to be. Various scheme for cheaper launch methods
>from Earth into space will certainly lower the costs a good deal, but exactly
>when and how much is up for grabs. Solar sails will probably prove very
>useful for moving around the solar system, especially the inner solar
system.
>Laser powered sails seem to have the potential for driving vehicles away from
>the Sun at a remarkably high speed, maybe competitive with an ion drive, but
>how do you stop?!
>
>In my opinion that's pretty much it, as far as "reality" goes; every other
>idea I've ever heard of involves "magic": new physics, or something like
>that. Of course I assume there _is_ new physics to be discovered, but when,
>whether, and how it will give us better propulsion is sheer speculation, or
>so I judge.
>
>There is also something called a "Bussard ramjet", that gathers interstellar
>hydrogen for a fusion drive of some kind. This is so far off the scale in
>engineering terms that I have to class it with the fantasy ideas, even though
>it does not involve new physics.
>
>Schemes for space tourism abound, and will probably become reality when cost,
>market, and safety problems are solved. I'm not holding my breath, but maybe
>I'll be surprised.
>
>Sorry so gloomy. The interstellar game could be overturned in a flash, but
>there's no telling when. Right now we have the Solar System to deal with,
>and the technology to do it.
>
>---------------------------------------------------------------
>
>NASA has actually got a program for "off-the-wall" propulsion ideas, and
>of course it's good that they should want to keep an eye on new
>thoughts. But I don't find anything I see especially promising for the
>foreseeable future -- ie, anything you can say "we will have this by such
>and such a date, most probably". These are maybe 30 years, maybe a
>century, maybe 1000 years, maybe never.
>
>Anyhow some URLs are:
>
>www.lerc.nasa.gov/Other_Groups/PAO/warp.htm
>
>www.lerc.nasa.gov/WWW/bpp/
>
>
>Hope it helps.
>
>Bill W.
>
>___________________________________________________________
>Wm. A. Wheaton
>Infrared Processing & Analysis Center
>California Institute of Technology
>M/S 100-22
>770 So. Wilson Ave.
>Pasadena CA 91125
>
>626/397-7104 fax 626/397-9600
>
>waw@ipac.caltech.edu
>http://spider.ipac.caltech.edu/staff/waw
>
>
>
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