It's official

There was also the problem of joint rotation which caused the O-rings
to unseat when the casing was pressurized and prevented the secondary
O-ring from sealing at all. This led to the joint being reclassified
from Crit-1R to Crit-1.
Another problem was the decision to increase the pressure used to
leak test the joints which tended to cause blowholes in the puddy
used to fill the gap in the insulation between two segments of the SRM.
Aerodynamic stresses would have NOT been a factor if the joint had
functioned as intended.

Not quite. The leak in the SRB caused the lower attachment point of the
SRB to break loose from the ET. The SRB then pivoted around the upper
attachment point and its top crushed the ETs LOX tank. At nearly the
same time the weakened aft dome of the LH2 tank fell out and the
LH2 burned very rapidly. The orbiter was destroyed by aerodynamic
break-up, not an explosion.

   NO, the fix was to redesign the joint to add a capture feature to
prevent joint rotation, add a 3rd O-ring as added safety, add joint
heaters to keep the O-rings warm in cold weather, and change the
insulation in the segments so that it meets and seals with the
insulation in the ajoining segment eliminating the gap that was
filled with puddy in the old design. These changes apply to the
three field joints between the four segments of the RSRM. Changes
were also made to the nozzle joints (where the current problem is)
and the igniter joints.
  Throttling down at Max-Q has always been done since STS-1 and
has NOTHING to do with fixing the problem that caused the Challenger
accident.

Tom Faber
tfa @america.net

A lot of parts of the SSA (Space Suit Assembly) involve RTV.
Top of my head list:
Glove finger caps
Glove palms
Boot soles (old blue soles, don't know if the new white soles are RTV)
gasket around helmet light mount
Helmet bubble to neck ring seal
suit-side neck ring to HUT seal (Hard Upper Torso)
...

Dow-Corning will likely survive, maybe under a different name (like
Johns-Mansville (sp?)).

bcnu - Grungy (John Gladu)
Systems Support Center -- Baylor College of Medicine
INTERNET: jgl @bcm.tmc.edu  | VOICE: (713)798-7370
 US MAIL:  One Baylor Plaza, Houston, Texas  77030
.opinions expressed are just that.obviously.
fegorote  n. an unintelligible public announcement

First of all, that wasn't the fix.  The fix was to redesign the
joints.  Second of all, it has little to do with the current problem.
The current problem is with the internal nozzle joints; the Challenger
problem was with the field joints.  Third of all, if the NASA press
release (release 95-130) is to be believed, all that is needed to deal
with the current situtation is to make sure that the RTV thermal
barrier is where it is supposed to be.

As for your larger conclusions about SRBs being risky, pretty much
everyone I have heard express an opinion on the subject agrees.  NASA
wanted to design a liquid fly back booster, but Congress wouldn't fund
it.  The solution is not to pretend that the shuttle has no risks (the
astronauts are quite aware that it does according to all reports), but
keep working on X-33 and DC-XA so that we will be able to someday
retire the shuttle in favor of a system which is cheaper and less
risky.

Until the problem is fixed it is too early to make any sort of predictions
on what would happen to the manifest.  IF the problems requires
"Destacking" it will be a significant impact to the manifest.
Stacking is about a 3 month process, and 73 would most certainly
slip and I would bet 74 would have to slip too.

John Coggeshall

: In article <3vbrhm$ @hecate.umd.edu>,
: jby @astro.umd.edu says...
: >
: >Just heard that NASA has grounded the shuttle fleet
: until the O-ring
: >damage problem is solved.
: >
: >-Jeff

: Could someone describe the problem with the O-rings?

To make it very short, sweet, and I hope accurate, the shuttle solid
rocket boosters have field joints circumnavigating the boosters
which are sealed by O-rings (rubber circular gaskets). During the
Challenger disaster, a coupling of cold weather (made the rings
less responsive to maintain a seal), harmonic and aerodyanmic stresses,
(created horizontal pressure on the boosters (flexing like bending
a pencil)), and gas pressure (from the hot gases), allowed the gases
to erode and destroy the O-rings as the gas blew by. This allowed
the hot gas from the solid rocket booster to escape and contact
the immense hydrogen fuel tank and it exploded (catastrophic failure).

The fix for this (weather restrictions, throttle down at maximum
aerodynamic pressure) is apparently not working as some of the
seals have apparently been once again contacted by the hot gas
leaving "pencil point sized shiny dimples" (nasa's own words)
in the O-rings.

Discussion for Rocket scientists: (GRIN)

During my tenure with the USAF I was a historian with the Strategic
Air Command and had occasion to browse the official records and
other discussions. My conclusions:

Continued in next message!

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Caution: The opinions expressed may not even be my own.

The problem isn't with the o-rings but with the process of applying the
sealing compound currently injected into the joint surface that is designed
to protect the o-rings from gas-path damage. A first line of defense, if you
will.

With the present method, air can be trapped and compressed behind the RTV
compound that is injected into the joint with a needle at incremental points
around the interior circumfrence of the nozzle. Before the compound has had
an opportunity to cure the air creates a tunnel through the compound and
escapes creating a gas-path into the joint. Studies are being conducted to
arrive at a better method of applying the compound as well as the best method
to identify and repair a gas-path in the field.

"Buttered" joints, used in the SRB version nozzle and SRB and RSRM field
joints, have been superceded by the injection method on the RSRM nozzle.

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Sounds as if this problem is correctable and will not require any
major redesigns, test firings, etc. Thank goodness.

I assume the motors for 73/Columbia and 74/Atlantis have not yet been
stacked. If not, then there should be no problem in checking their rings/seals.
Any flaws can be easily corrected and their launches should not be impacted.

However, 69/Endeavour has already been delayed from July 20 to some point
in August, we hope. The next Endeavour flight, 72, was supposed to launch
on Nov. 30. This seems unlikely now. Will they have time to get this one
off before Christmas, or is a delay into January likely? If so, can the
remaining launches early next year remain on track?

Please post or e-mail me with comments. Thanks.

Tom