Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Ion Engines
Message-ID: <1991Mar25.184907.16454@zoo.toronto.edu>
Date: Mon, 25 Mar 1991 18:49:07 GMT
References: <1991Mar7.142311.10412@vaxa.strath.ac.uk> <6963@mace.cc.purdue.edu> <1991Mar11.201910.8476@casbah.acns.nwu.edu> <1991Mar12.003321.13988@zoo.toronto.edu> <3356@phred.UUCP> <1991Mar19.235853.6842@zoo.toronto.edu> <3361@phred.UUCP> <1991Mar22.043009.5544@zoo <1991Mar24.191051@hagar3.acc.Virginia.EDU>
Organization: U of Toronto Zoology

In article <1991Mar24.191051@hagar3.acc.Virginia.EDU> rnm8s@hagar3.acc.Virginia.EDU (Rory Mcleod) writes:
>|> What I'm looking for ON a solid rocket motor is dust, plus a museum
>placard
>|> saying "obsolete form of space propulsion system, abandoned in the
>early
>|> 1970s when ion rockets became practical"...
>
>	Ion engines cannot be used to launch payloads into space.

Is it too much to ask that when you enter in the middle of a discussion,
you read the back issues?  The subject of this particular discussion was
the IUS, which is not an Earth-to-orbit launcher.

Furthermore, the more general point still stands.  We could easily build
Earth-to-orbit launch systems far superior to solid rockets.  Even plain
old liquid-fuel rockets are better in nearly every way.

>... Technologies to replace chemical rockets
>for getting stuff into orbit will not be perfected until after the
>turn of the century.

This I will agree with, but the problem is lack of effort, not inherent
difficulty.

>The most promising are the airbreathing
>ramjet/scramjet engines being developed for the NASP...

NASP is a fiercely difficult design problem.  It would not be what one would
choose as the most promising technology, if the objective was cheaper and
better launches to orbit.  NASP is doing it the hard way on purpose, aiming
at development of hypersonic airbreathing technology rather than at an
optimal system for space launches.

>and perhaps
>laser propulsion.  I know of no major project, though there may very
>well be one, for the development of laser propulsion...

There is a minor project on laser propulsion at LLNL.  The technique looks
viable, and could progress very quickly if it got even a modest fraction
of the money being spent on NASP.

>Mass drivers,
>which have been discussed at length on sci.space (where this probably
>belongs), are best for transporting materials from airless bodies, like
>the moon.

Almost all non-airbreathing launch systems, including even solid rockets,
work better on airless bodies.  That doesn't mean they are unworkable for
launch from Earth.
-- 
"[Some people] positively *wish* to     | Henry Spencer @ U of Toronto Zoology
believe ill of the modern world."-R.Peto|  henry@zoo.toronto.edu  utzoo!henry
