possible January launch

On 13 Feb 2004 16:53:03 GMT, (John F. Carr) wrote:


Challenger was weather-related. Did January weather affect
foam shedding on Columbia's tank?

There was some speculation that a rainstorm in December may have
effected the foam on the tank, but the CAIB did not include it among
the 'causes' of the accident.

Brian

On Thu, 12 Feb 2004 21:56:51 -0800, David Ball
wrote:


Can someone here comment on how a Shuttle launch compares to an Apollo
launch?

Shuttle is a lot faster leaving the pad, which means Saturn V spent
more time down low making a racket.

Brian

Can someone here comment on how a Shuttle launch compares to an Apollo
launch?

-- David


I viewed the STS-3 launch from Cocoa Beach. You could see it before you
could hear it, but when you heard it the sound was incredibly loud, like
very loud thunder - and that was 5-6 miles from the pad!


JD

On Fri, 13 Feb 2004 07:50:48 GMT, Bruce Palmer
wrote:



Shuttle usually re-boosts it, but the main problem is its gyros are
failing. 2, maybe 3 years max remaining useful life if the servicing
mission isn't done.

Forgive my ignorance, but presumably a gyro failure is down to
mechanical failure, in which case can someone more knowledgeable
please explain why solid-state laser ring gyros are not being used?

And in the event that the shuttle follow-on programme is delayed, so
postponing a future servicing mission unexpectedly, is using
solid-state gyros as a retro-fit package out of the question?

Regards

Godfrey Rock

In article ,
wrote:

Forgive my ignorance, but presumably a gyro failure is down to
mechanical failure, in which case can someone more knowledgeable
please explain why solid-state laser ring gyros are not being used?

I believe that they're not precise enough for the level of pointing
needed; ICBW...


--
-Andrew Gray

Andrew Gray wrote in
:

In article ,
wrote:

Forgive my ignorance, but presumably a gyro failure is down to
mechanical failure, in which case can someone more knowledgeable
please explain why solid-state laser ring gyros are not being used?

I believe that they're not precise enough for the level of pointing
needed; ICBW...



A top laser ring gyro can sense a rotation rate of 10^-8 degree per hour.
This is quite a bit in excess of what any mechanical device can achieve.

Of course, if you really want utter precision....
There are methods of using quantum interactions in a bose-einstein
condensate that (promises to) give another 10^12 better resolution.


The problem with these advanced non-mechanical gyros is that they tend to
be physically big devices, with rather large energy consumption rates. They
also tend to be *much* more sensitive to temperature fluctuations than
mechanical devices.

Smaller laser ring gyros are in common use in aviation though. While
totally good enough for terrestrial use, these are less accurate than the
best, and have a problem with "lock-in frequency" that prevents sensing
very low rates. For example a gyro may have a rate sensitivity of S, but
only for rotation rates greater than 50 S. Bypassing this problem requires
obscenely perfect optics with mirror reflectivity better than 99.99999%

This is a lot of techno-talk, so here is the basic:
When Hubble was designed, mechanical gyros were known and trusted, laser
gyros were new and experimental. Only in recent years have space-grade
laser gyros been available, and none yet with quite the accuracy that
hubble wants.

It is this extreme accuracy that hubble requires that causes all the
headaches, *including* triggering the weakness of the present gyros. Too
many design elements had to be taken to extreme to satisfy the demands,
resulting in an inherently weak design. Added to that the silly quality-
control error of contaminating the first batch's suspension fluid with
oxygen... tsk. tsk.

wrote:

On Fri, 13 Feb 2004 07:50:48 GMT, Bruce Palmer
wrote:



Shuttle usually re-boosts it, but the main problem is its gyros are
failing. 2, maybe 3 years max remaining useful life if the servicing
mission isn't done.


Forgive my ignorance, but presumably a gyro failure is down to
mechanical failure, in which case can someone more knowledgeable
please explain why solid-state laser ring gyros are not being used?

And in the event that the shuttle follow-on programme is delayed, so
postponing a future servicing mission unexpectedly, is using
solid-state gyros as a retro-fit package out of the question?

That I do not know. Maybe someone with more knowledge of the situation
will chime in.

--
bp
Proud Member of the Human O-Ring Society Since 2003

On Fri, 13 Feb 2004 20:37:41 GMT, Bruce Palmer
wrote:

John F. Carr wrote:
In article ,
Bruce Palmer wrote:

David Ball wrote:


I was just reading http://space.com/news/okeefe_shuttle_040212.html
and it looks like they might miss the fall 2004 time frame and end up
launching in January 2005.

Considering the history of problems with January launches, does anyone
find this idea discouraging?

The January thing is a coincidence, nothing more.


Challenger was weather-related. Did January weather affect
foam shedding on Columbia's tank?


Not according to the CAIB report.

Nor was the Apollo 1 fire due to January weather. A sad coincidence, nothing
more.

--
Michael R. Grabois # http://chili.cjb.net # http://wizardimps.blogspot.com
"People say losing builds character. That's the stupidest thing I ever
heard. All losing does is suck. " -- Charles Barkley, 9/29/96

Shuttle usually re-boosts it, but the main problem is its gyros are
failing. 2, maybe 3 years max remaining useful life if the servicing
mission isn't done.

Forgive my ignorance, but presumably a gyro failure is down to
mechanical failure, in which case can someone more knowledgeable
please explain why solid-state laser ring gyros are not being used?


Is not the gyros used to point the telescope as well ? (no propulsion
system...)
A lasergyro would have a hard time doing that...

:-)

Ole wrote:

Is not the gyros used to point the telescope as well ? (no propulsion
system...)
A lasergyro would have a hard time doing that...

:-)

2 different things. Both are "gyroscopes" but one type is small and
used for measuring angular rates of rotation. The other is massive and
is used for applying torque to a spacecraft for the purpose of pointing
it or stabilizing it. The latter are called "control moment gyros" and
a Google search will turn up plenty of good references.

--
bp
Proud Member of the Human O-Ring Society Since 2003