Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: All solid rocket to orbit
Date: Fri, 20 Oct 2000 17:06:34 GMT

In article <8FD2C8BEDdasmillrpacbellnet@206.13.28.144>,
Mark Miller <dasmillr@pacbell.net> wrote:
>Once you're in space, though, you're going to need some kind of non-aerodynamic
>attitude control technique.  If it looks anything like a normal second-stage,
>then you won't be able to make it passively spin-stabilized.

Note that the Juno I, aka Jupiter C, which launched Explorer 1, used spin
stabilization for its second, third, and fourth stages.  The first stage
had inertial guidance, but once it spun the upper stages up, pointed them,
and turned them loose, there was no further attitude control.  Mind you,
the spin rate was high, the solid motors had to be specially qualified,
and the orbit insertion was very imprecise.

It's actually moderately common to spin-stabilize a final solid stage,
since it minimizes parasitic mass carried along with the payload.  Scout,
for example, had its guidance system on its third stage:  the third stage
pointed the fourth stage, spun it up, started an ignition timer, and then
separated.

Solids in general are notorious for sloppy orbit insertion, though.
Current all-solid launchers tend to have a little liquid-fuel trim stage
on top, to touch up the orbit after the solids have finished wobbling
around.
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)