Faulty hardware found on shuttle

In article ,
rk wrote:
...Commercial aircraft don't have star trackers that
look at the sky and see if they spot the one star they are expecting to
see based on current location around earth AND current attitude of
shuttle.

Star trackers, scanners, etc., are rather common devices, even for small
spacecraft. Didn't the SR-71 have a star tracker?

It did, as did other military aircraft (and even some cruise missiles)
dating back well into the 50s. Commercial aircraft of the day didn't have
quite such an urgent need to minimize crew, so they simply carried human
navigators. (If you look carefully at the pre-jet airliners, somewhere
near the main cockpit windows you'll usually see a small transparent dome
sticking up -- that's for the navigator to do star sightings.) Both the
military star trackers and the civilian navigators were swept away by the
advent of aircraft-sized inertial navigation systems.

MOST, which weighs 53kg as launched and totalled maybe US$4M development
cost, has a star tracker that holds it on target to within a few
arcseconds. The software for it, while by no means trivial, is nothing
supernatural (and I speak as the project's Software Architect).
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

"Henry Spencer" wrote in message
...

MOST, which weighs 53kg as launched and totalled maybe US$4M development
cost, has a star tracker that holds it on target to within a few
arcseconds. The software for it, while by no means trivial, is nothing
supernatural (and I speak as the project's Software Architect).

So your software is merely astronomical, then?

(Henry Spencer) wrote:

It did, as did other military aircraft (and even some cruise missiles)
dating back well into the 50s. Both the military star trackers and the
civilian navigators were swept away by the advent of aircraft-sized
inertial navigation systems.

Early inertial systems weren't considered particularly stable. It was
not uncommon to have *both* systems installed. Civilian navigators
were also helped out the door by the increasing availability and
reliability of LORAN/DECCA/OMEGA etc...

D.
--
Touch-twice life. Eat. Drink. Laugh.

"Derek Lyons" wrote in message
...

Early inertial systems weren't considered particularly stable. It was
not uncommon to have *both* systems installed. Civilian navigators
were also helped out the door by the increasing availability and
reliability of LORAN/DECCA/OMEGA etc...

Air NZ flights to Antarctica in the late '70s carried a human navigator, but
this did not save ZK-NZP despite its state-of-the-art INSs, which were found
to be only as safe as their programmers.

In article ,
(Derek Lyons) writes:
(Henry Spencer) wrote:

It did, as did other military aircraft (and even some cruise missiles)
dating back well into the 50s. Both the military star trackers and the
civilian navigators were swept away by the advent of aircraft-sized
inertial navigation systems.

Early inertial systems weren't considered particularly stable. It was
not uncommon to have *both* systems installed. Civilian navigators
were also helped out the door by the increasing availability and
reliability of LORAN/DECCA/OMEGA etc...

For aircraft, there were a lot of Doppler Nav systems, as well. The
same sort of integration as an INS, for the most part, but mostion
sensing was done with a set of 4 radar beams. Change of postion was
measured by the Doppler Shifts of the beams. With a good alignment,
it was rather accurate, but, also rather unstealthy, and susceptible
to weather problems.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

Derek Lyons wrote:

Early inertial systems weren't considered particularly stable. It was
not uncommon to have *both* systems installed. Civilian navigators
were also helped out the door by the increasing availability and
reliability of LORAN/DECCA/OMEGA etc...

In the case of Hound Dog, the missile originally had purely inertial
guidance; but later a star tracker was located on each of the B-52's
twin launch pylons that would update the missile's INS right up to the
moment of launch- since twin sensors were used, I imagine that not only
did you have system redundancy, but could split the difference in what
both the star trackers were giving as bearing and location, and give the
missiles a very accurate set of data; I suspect the bomber's nav system
used them also, particularly in areas where a radar check of the ground
would be an invitation to a SAM arriving pronto.
Our star sensors were far more compact than the first generation Soviet
equivalents; the transparent housing for the star sensor on the Buran
missile was the size of a fighter plane's canopy!
Here's a shot of the Hound Dog's star tracker under test- I assume that
the top assembly is the star tracker and the pylon-mounted electronics
system; and the large pod it's sitting on top of, the missile's INS
gear: http://www.ammsalumni.com/PlatforAst...r2_340x240.jpg
They seem to be testing it in a room with no ceiling, so that the star
tracker can see the sky.

Pat

Pat Flannery wrote:

Here's a shot of the Hound Dog's star tracker under test- I assume that
the top assembly is the star tracker and the pylon-mounted electronics
system; and the large pod it's sitting on top of, the missile's INS
gear: http://www.ammsalumni.com/PlatforAst...r2_340x240.jpg

Your assumption would be correct based on the systems I've
seen/studied/worked with. For obvious reasons you want your star
tracker rigidly (and if possible physically) aligned with your
intertial platform.

D.
--
Touch-twice life. Eat. Drink. Laugh.

Pat Flannery wrote:

Here's a shot of the Hound Dog's star tracker under test- I assume that
the top assembly is the star tracker and the pylon-mounted electronics
system; and the large pod it's sitting on top of, the missile's INS
gear: http://www.ammsalumni.com/PlatforAst...r2_340x240.jpg

Your assumption would be correct based on the systems I've
seen/studied/worked with. For obvious reasons you want your star
tracker rigidly (and if possible physically) aligned with your
intertial platform.

I'd be willing to bet that it was an analog system, and the star
tracker and INS were aligned and maintained as mated pairs.

D.
--
Touch-twice life. Eat. Drink. Laugh.

Derek Lyons wrote:


I'd be willing to bet that it was an analog system, and the star
tracker and INS were aligned and maintained as mated pairs.

Want proof of that? Behold Hound Dogs mounted on their pylons in
storage- they are apparently stored as mated pairs:
http://www.ammsalumni.com/stored-2_220x160.JPG (the red star tracker
protective cover is visible on the pylon's upper surface)
I saw one being worked on at Grand Forks AFB...it was also on its pylon.

Pat

Pat Flannery wrote:


Want proof of that? Behold Hound Dogs mounted on their pylons in
storage- they are apparently stored as mated pairs:
http://www.ammsalumni.com/stored-2_220x160.JPG

That's from this website, by the way http://www.ammsalumni.com/index.html
.....as is this truly impressive example of bad taxiing technique by
either a Stratofortress or Stratotanker pilot:
http://www.ammsalumni.com/NosetoNose61-2121_400x320.jpg

Pat