NASA brings engineer out of retirement to help find sensor glitch

On Wed, 20 Jul 2005 13:09:05 -0500, John Doe wrote
(in article ):

3- Since the ET burns up, it is a fair bet that any electronics in the ET are

new.

Not necessarily. There have only been a few more than a hundred tanks
built. It's much more likely that components like this were bought in
a single batch of a few hundred units at the time the design was
finalized. In fact, the overhead costs associated with producing and
procuring aerospace components a few at a time at quite prohibitive.
This is an area where I have some first-hand knowledge (specifically,
valves, fluid couplings and pressure and flow-rate transducers).

--
"Fame may be fleeting but obscurity is forever."
~Anonymous
www.angryherb.net

Herb Schaltegger wrote:
Not necessarily. There have only been a few more than a hundred tanks
built. It's much more likely that components like this were bought in
a single batch of a few hundred units at the time the design was
finalized.


Even if the design was never changed and NASA is still running on inventory
that was received and stored in the late 1970s, the parts used an each ET are
still "new" and not refurbished, have not suffered though the vibration ,
heat, cold etc cycles of a launch.

John Doe wrote:

Even if the design was never changed and NASA is still running on inventory
that was received and stored in the late 1970s, the parts used an each ET are
still "new" and not refurbished, have not suffered though the vibration ,
heat, cold etc cycles of a launch.

Even without those cycles - the components still age. (Indeed for
long service systems it's somewhat of a problem to determine which
aging effects are enviromental and which are inherent.)

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

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

On Wed, 20 Jul 2005 13:50:17 -0500, John Doe wrote
(in article ):

Herb Schaltegger wrote:
Not necessarily. There have only been a few more than a hundred tanks
built. It's much more likely that components like this were bought in
a single batch of a few hundred units at the time the design was
finalized.


Even if the design was never changed and NASA is still running on inventory
that was received and stored in the late 1970s, the parts used an each ET are
still "new" and not refurbished, have not suffered though the vibration ,
heat, cold etc cycles of a launch.

They may have decay issues, however, regardless of use. And platinum
is a catalyst for many chemical reactions. I'd be curious about the
possibility of such things were I doing the troubleshooting.

That pesky Second Law of Thermodynamics doesn't let up . . .

--
"Fame may be fleeting but obscurity is forever."
~Anonymous
www.angryherb.net

On Wed, 20 Jul 2005 14:09:05 -0400, John Doe wrote:

There are many stories of NASA paying the big bucks
to have small runs of old electronic parts built in order to maintain its
spare parts inventory.

That could be worse. In the early 80's a company I worked for was
starting to use cartridge tape backup units. All of a sudden, no new
tapes would work in them. IIRC, we were told by the drive manufacturer
that the engineer who mixed the tape backing for a certain unnamed
tape manufacturer had died and the tapes they were producing were
useless until they figured out what they were doing different.

Things weren't as automated then as they are now and WHO made the part
was sometimes important.

-- David

"Dr. P. Quackenbush" wrote in
k.net:

Nothing else with wings is half as complex as a shuttle.

I saw a DC-3 overhead yesterday. One of the reasons DC-3s are still
in the air is that you can fix most of one with the tools you keep in
the garage.

That may have been true at one time, but the newest generation of airliners
like the Boeing 777 are comparable to the shuttle in complexity.

--
JRF

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