Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!vsi1!daver!lynx!neal
From: neal@lynx.uucp (Neal Woodall)
Newsgroups: sci.space
Subject: Where the hell are electric-ion thrusters????
Summary: I want "Neptune at Night" to be a regular season show!!!
Keywords: not to mention "Jupiter at Night" and "Saturn at Night", etc, etc!
Message-ID: <6091@lynx.UUCP>
Date: 29 Aug 89 05:44:51 GMT
References: <8908241857.AA02943@fermat.Mayo.edu> <1989Aug25.183710.3054@utzoo.uucp> <4256@utastro.UUCP>
Reply-To: neal@lynx.UUCP (Neal Woodall)
Distribution: usa
Organization: Lynx Real-Time Systems Inc, Campbell CA
Lines: 49

In article <4256@utastro.UUCP> terry@astro.UUCP (Terry Hancock) writes:

>1> Depends on what you mean by "current technology" -- Ion
>drives capable of doing this (with the appropriate power source),
>do exist and have undergone vacuum chamber testing.  That they have
>not been used for main thrust on a spaceprobe has more to do with
>senseless conservativism than with any real technical challenge.

Now here is a subject that I have been meaning to bring up lately:
ion thrusters. Where the hell are they? I understand that the US has
had one tested and ready to go for over seven years now. I uses
(mercury, cesium....I cannot remember which) as the reaction mass, and
uses very high voltages to shoot the charged particles out at HIGH
velocities....not much thrust, but an exceedingly high specific
impulse (although I have read that some tested designs will produce
about 50 lbs of thrust!).

These things don't give very high accelerations, but they can run
continuously for *months*.....thrust all the way! Accelerate for half the
trip, decelerate for the other half. How do the thrust forces compare
to the chemical thrusters used on deep-space probes of today? I know
that chemical rockets give more acceleration, but they can only burn
for short periods of time.

Didn't the US conduct a test called SERT a few years ago? (SERT = Space
Electric Rocket Test) What was the outcome of the test??

Also, it seems that an electric-ion thruster is perfect for earth orbit
transfer vehicles....you could move large masses with them, it would just
take awhile.

>(Some people are distrustful of letting a probe use such "new and
>unproven technology" -- of course it wouldn't be such a big risk if we 
>had a larger exploratory program than we do, but as it is, losing one
>probe would be catastrophic to the program).

Is this the real reason? Why the hell cannot our country do with two fewer
B2 bombers, and give that money to JPL for probes, including a full
program of electric-ion engine probes to various parts of the solar system?
All of the JPL people on TV the other night were saying that this is the
last Neptune mission in their lifetimes (even some of the younger ones said
this).....if we had an working electric-ion system, we could send probes
to all points in our system! Hell, a manned Mars mission would be fast
with an ion thruster!




Neal