[AR] Ionic orientation (was: Falcon 9 flight today)
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 6 Oct 2013 19:02:15 -0400
On Sun, Oct 06, 2013 at 03:43:42PM -0600, Ben Brockert wrote:
>For anybody else who hadn't heard of this system: it turns out that
>from 60 to 40,000+ miles there are a useful number of thermal ions,
>and the positive ions are basically stationary from the perspective of
>an orbiting craft. Counting those ions with negatively charged sensor
>grid/plate setups you can get pitch and yaw values relative to
>direction of motion.
Oh, so that's how the system Chertok writes about in "Rockets and
People" works.
It didn't always work correctly, though; they ran into nonuniformities
in the ion cloud or something. On their first orbital rendezvous
success:
"On day two, the ionic orientation failed, falling into “ion
pockets.”"
...
"...after somehow setting up the spacecraft using the ionic
system, the commands were issued to start up the descent cycle
programs. The ionic system slipped up somewhere in the
Brazilian Magnetic Anomaly, and the braking burn sent the
spacecraft toward Earth on a long, flat trajectory that
emerged beyond the limits of the authorized corridor."
(whereupon it was destroyed by the self-destruct system)
That led them to decide that:
"Ionic orientation was unreliable. The system needed to be
supplemented with an infrared sensor. This would provide
reliable pitch and roll orientation."
Of course, today we could do a lot more to detect and properly handle
such "ion pockets" than they could with 1960s Soviet electronics.
(Hmm, would their problem have been running into the Van Allen belts?)
--
Norman Yarvin http://yarchive.net/blog
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