Faulty hardware found on shuttle

Richard Lamb wrote:

Bruce Palmer wrote:

Exeter wrote:

Disturbing on many levels.


I have an idea how to expand the "Civilians In Space" program. Screw
the teachers, when the CEV is built I propose that the first manned
flights include one crewmember from the design and engineering teams.
Hell, if they decide to include auto-land functionality in the CEV then
the initial manned test flights should be crewed entirely by contractor
personnel.

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

Igor Sikorski was quoted something like,

"There are good designers with good designs,
good designers with bad designs,
bad designers with good designers
and bad designers with bad designs.

If designers flew their own designs,
there would soon be only good designers
with good designs."

Pretty cocky, huh?

As an experienced amateur aircraft designer,
given to occasional fits of introspection,
and one who flies his own design,
I often wonder where I fit in that list.

Igor flew his helicopter prototypes wearing a full suit with a dress
hat, tie and polished shoes. Now that's cocky.


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Why can't anyone pinpoint the reason no
inspection was previously done? Was it a requirement that was
overlooked?

The thing was assembled wrong. It was not obvious to casual observation.
One day a guy was looking at the tech manual and the assembly and said "Hey,
wait a minute....."

This doesnt explain never having been inspected...............

Sure parts can be assembled wrong But NEVER looked at a critical one system
in over 30 YEARS?
Hey this is my opinion

If designers flew their own designs, there would soon be
only good designers with good designs."

While that's cute, I'd say it misses the mark somewhat. It's like asking
a cook to eat the Fugu he has prepared for his exam himself - a practice
that was discontinued in modern times when the failure rate was no longer
deemed societally acceptable. Furthermore, even a good designer likely is
not a good tester (i.e., pilot in your example) - why unnecessarily kill
a good designer when a good test pilot might have survived the fault?

Jan

"Jorge R. Frank" wrote:

Richard Lamb wrote in
:

But even a Boeing 7^7 is only a pale glimmer of the complexity
involved in designing and building something on the level of
the Orbiter.

Actually, Boeing's modern 7*7 designs are comparable in complexity to the
orbiter. The biggest difference is that modern airliners have several
design generations behind them, so their designers have a pretty good idea
what works and what doesn't.

The orbiter is still essentially a first-generation design. If it's balky
and temperamental, it's mainly because its designers did *not* have a prior
experience base for reusable spacecraft.

--
JRF

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check "Organization" (I am not assimilated) and
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Tell you what, Jorge.

I'll conceed that spacecraft design is comporable to airliner
design - same way my little airplane is comporable to a 747.

Yeah, sorta, give or take a few orders of magnitude.

Richard

Richard Lamb wrote in
:

"Jorge R. Frank" wrote:

Richard Lamb wrote in
:

But even a Boeing 7^7 is only a pale glimmer of the complexity
involved in designing and building something on the level of
the Orbiter.

Actually, Boeing's modern 7*7 designs are comparable in complexity to
the orbiter. The biggest difference is that modern airliners have
several design generations behind them, so their designers have a
pretty good idea what works and what doesn't.

The orbiter is still essentially a first-generation design. If it's
balky and temperamental, it's mainly because its designers did *not*
have a prior experience base for reusable spacecraft.

I'll conceed that spacecraft design is comporable to airliner
design - same way my little airplane is comporable to a 747.

Yeah, sorta, give or take a few orders of magnitude.

More like give or take a factor of two, at most - especially for recent
top-of-the-line airliners like the 777. Both vehicles have redundant
electrical power, avionics, and hydraulics. The SSME is complex, but
comparable to a modern turbofan engine. The orbiter's landing/deceleration
system is considerably simpler than that of an airliner. The orbiter does
have a thermal protection system that the airliner lacks, but said system
is not terribly complex, all things considered. The orbiter has a reaction
control system that airliners don't have, and that system *is* fairly
elaborate. On the other hand, the avionics on recent airliners are
dramatically more elaborate than those on the orbiter.


--
JRF

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"Jorge R. Frank" wrote in message
...

More like give or take a factor of two, at most - especially for recent
top-of-the-line airliners like the 777. Both vehicles have redundant
electrical power, avionics, and hydraulics. The SSME is complex, but
comparable to a modern turbofan engine. The orbiter's landing/deceleration
system is considerably simpler than that of an airliner. The orbiter does
have a thermal protection system that the airliner lacks, but said system
is not terribly complex, all things considered. The orbiter has a reaction
control system that airliners don't have, and that system *is* fairly
elaborate. On the other hand, the avionics on recent airliners are
dramatically more elaborate than those on the orbiter.

I also believe the 777 and even more so the current 7x7 is being designed
expressly for cost of ownership in mind. This includes making it easier to
diagnosis issues, repair them, access to items, etc.

Some of that was cut out of the shuttle design due to mass overruns or never
even considered. Again a difference between a 1st generation re-usable
craft and an N-th generation (I'd estimate 4th? but not sure if there's an
industry metric there.)






--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
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As an engineer in a manufacturing environment I'd cite this problem as:

Not fool-proofing the design. A gear tends to be round with teeth on it's
circumference. This means it's pretty easy to install backwards and not
notice. A simple stamping on the gear such as "This side faces out" or
better yet design the shaft the gear fits onto so that the gear can only go
on in the direction intended. This type of error happens a lot when it is a
circular object that is symmetrical about it's circumference. Design the
assembly so it can't be put together wrong.

As for inspection, LOL! You don't inspect quality into anything. The general
rule of thumb for visual inspection is 80-90% accuracy. If you look at 1000
objects and there's 10 defects in the group, you most likely will miss one
of the 10 defects.


"bob haller" wrote in message
...

Why can't anyone pinpoint the reason no
inspection was previously done? Was it a requirement that was
overlooked?

The thing was assembled wrong. It was not obvious to casual observation.
One day a guy was looking at the tech manual and the assembly and said
"Hey,
wait a minute....."

This doesnt explain never having been inspected...............

Sure parts can be assembled wrong But NEVER looked at a critical one
system
in over 30 YEARS?
Hey this is my opinion

"Jorge R. Frank" wrote in
:

The SSME is complex, but comparable to a modern turbofan engine.


More like a turbojet that runs on canned oxidizer and has a rather large
afterburner :-)

--
Reed

"Greg D. Moore (Strider)" wrote:
Some of that was cut out of the shuttle design due to mass overruns or never
even considered. Again a difference between a 1st generation re-usable
craft and an N-th generation (I'd estimate 4th? but not sure if there's an
industry metric there.)

Shuttles are not only first generation products, but also, especially in the
case of Columbia, test articles for a concept that had never flown before.

The first couple 747s were also test articles, outfitted with plenty of
non-production sensors. They use one to test the structures, measure the point
where wings break etc. The rest are used for flight testing.

NASA hasn't had the opportunity to design/build improved shuttles and only had
5 built. And while airline have been able to ditch their older 747-200s in
favour of 747-400s based on lower cost of operation and abilitty to do
non-stop flights over pacific, NASA has not been allowed to order a
new-improved Shuttle that would have reduced the cost of maintenance/operations.

But NASA has been able to retrofit its existing ones with some improvements,
but has not been allowed to retrofit all of the improvements it has wanted.

What is needed is for some real/independant accountants to do se serious
cost-of-ownership study of existing shuttles versus cost of building 4 new
shuttles that include all of the improvements NASA knows are possible with
today's real/tested technology.

NASA maintenance personel know very well what is difficult to acces/maintain
on existing shuttles and improvements in that area could potentially make a
big difference in maintenance costs for a new shuttle.

At the time the original batch was produced, NASA had no clue on what would
and wouldn't really need maintenance. Now it does.

Reed Snellenberger wrote:
The SSME is complex, but comparable to a modern turbofan engine.


More like a turbojet that runs on canned oxidizer and has a rather large
afterburner :-)

In the SSME, are there turbines aft of combustion used to drive turbopumps
forward of combustion ? (eg: fan blades that must widtstand direct intense
heat/pressure) ?

Or are the SSME simply glorified sprayers of fuel mixed just right and are
then ignited aft of any mechanical devices ?