Conference 7.286::space

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.military
Date: 29 Jun 90 19:48:45 GMT

	CAPE CANAVERAL, Fla. (UPI) -- The 17-inch-wide fuel line connectors
between a space shuttle and its external fuel tank are complex
assemblies that must work properly to channel fast-flowing rocket fuel
safely to the ship's main engines.
	Two such fittings, one for liquid hydrogen and the other for liquid
oxygen, feed propellants into the belly of the shuttle during launch
while giant valves in the lines are used to seal them off just before
the tank is jettisoned in space.
	Leaks in the 17-inch liquid hydrogen ``disconnect'' fitting used by
the shuttles Columbia and Atlantis have temporarily grounded NASA's
fleet of spaceplanes and raised questions about the critical umbilical
system and how it is assembled for launch.
	The shuttle is mounted on an external fuel tank by giant, exploding
bolts in the disconnect fitting near the ship's fuel lines. Electrical
cables and smaller propellant pressurization lines also are routed
through the shuttle-tank connectors.
	The fuel lines from the tank butt up against matching lines in the
belly of the ship that then split three ways to route propellant to each
of the three engines.
	Various internal seals are used to ensure a leak-free fit between
all the lines and the system requires an elaborate assembly procedure in
the Vehicle Assembly Building at the Kennedy Space Center before a
shuttle can be moved to the launch pad.
	The 17-inch fittings, built by Parker Hannifin of Irvine, Calif.,
do just what the name implies: they allow the fuel lines to separate in
space so the tank can be jettisoned.
	During the climb to space, giant 17-inch-wide ``flapper'' valves on
the tank side of the fittings and inside the shuttle fuel lines are wide
open.
	After engine shutdown, however, the valves rotate shut to prevent
any fuel trapped in the lines from escaping into space and imparting an
unwanted push to the spaceship in the weightlessness of space.
	``Valve closure on the orbiter side of each disconnect also
prevents contamination of the orbiter main propulsion system during
landing and ground operations,'' according to a reference book published
by shuttle-builder Rockwell International.
	A thin, white ``interface seal'' runs around the lip of the shuttle
fuel lines where they butt up against the disconnect. Other leak
barriers, called ``shaft seals,'' are in place around the linkages used
to rotate the valves shut.
	Trouble with a seal is the leading suspect in the leaks that
grounded Columbia and Atlantis.
	But because the full 100-ton weight of the shuttle is focused in
the area of the disconnect fittings, repairs to such seals cannot be
made at the launch pad. The only way to gain access is to first remove
the shuttle from the external tank, a procedure that requires an
overhead crane in the Vehicle Assembly Building.
	The disconnect fittings are critical to a safe launch and veteran
astronaut John Young raised major safety questions about the valves in
the wake of the Challenger disaster.
	Should one of the valves inadvertantly close during engine
operation, a catastrophic failure likely would result, destroying the
shuttle and dooming its crew.
	Special modifications were made to the flapper valves after the
Challenger disaster to eliminate any possibility of a premature closure
and a new design, in which the valves are not located directly in the
flow of fuel, currently is under development.

From: [email protected] (Peter E. Yee)
Newsgroups: sci.space.shuttle
Date: 29 Jun 90 22:28:11 GMT
Organization: NASA Ames Research Center, Moffett Field, CA

Mark Hess
Headquarters, Washington, D.C.                  June 29, 1990
(Phone:  202/453-4164)                          5:45 p.m. EDT

Ed Campion
Headquarters, Washington, D.C.
(Phone:  202/453-8536)

Lisa Malone
Kennedy Space Center, Fla.
(Phone:  407/867-2468)


RELEASE:  90-89

HYDROGEN LEAK DISCOVERED ON SHUTTLE ATLANTIS


     A propellant loading test of the STS-38 Space Shuttle 
vehicle, slated to conduct a dedicated Department of Defense 
mission in mid-July, revealed a hydrogen leak.  Although similar 
to the leak that caused the postponement of the STS-35/Astro-1 
mission, the leak appears to be smaller than the one detected 
during the tanking exercise on the STS-35 vehicle prior to its 
rollback to the VAB and demating.

     Engineers today loaded the Shuttle's external fuel tank to 
about the 5 percent level to check for leaks in the umbilical 
between the orbiter Atlantis and the fuel tank.  Instrumentation 
located in the umbilical area detected hydrogen shortly after the 
fueling process went from a slow fill to a fast fill mode.

     Engineers believe the leak is in a cavity between the 
orbiter and external tank umbilical plates.  While the leak's 
precise location is not known, tests today indicate the 17" line 
between the orbiter and the ET used to feed hydrogen to the 
orbiter's three main engines is contributing to the leak.  The 
leak appears to be both temperature and flow-rate dependent.

     Columbia is currently in the Orbiter Processing Facility 
(OPF).  Its umbilical has been removed and is scheduled to be 
shipped to Rockwell-Downey this weekend for installation in a 
test stand for further leak testing.  Tests of the ET side of the 
STS-35 umbilical did not reveal any leaks large enough to account 
for the leak seen during tanking of the STS-35 vehicle.  

     Leonard Nicholson, Deputy Director, Space Shuttle Program, 
will lead the NASA/industry team charged with analyzing the cause 
of the leak and determining corrective actions.

     Until the cause of the leak has been determined, further 
processing of the STS-38 vehicle has been suspended.  When the 
problem has been identified it is expected that STS-38 will be 
brought back to the VAB and the orbiter demated from the tank to 
make the necessary repairs.  While a new target date is not known 
for the STS-38 launch, it is expected the flight will be delayed 
a minimum of two weeks.

     Briefings to the news media updating the progress on the 
investigations are tentatively planned for Tuesday, July 3 and 
Friday, July 6 from NASA Headquarters, Washington, D.C.

I suppose this will lead to more NASA bashing in Congress.  I can hear Senator
Mikulski and Representative Gore gearing up to toss accusations around over this
one, too.

Wook

From: [email protected] (Peter E. Yee)
Newsgroups: sci.space.shuttle
Date: 2 Jul 90 18:14:51 GMT
Organization: NASA Ames Research Center, Moffett Field, CA

Mark Hess
Headquarters, Washington, D.C.                       July 2, 1990
(Phone:  202/453-4164)

                     LH2 LEAK INVESTIGATION

History

     During the launch attempt for the STS-35 mission on May 29, 
1990, a hydrogen leak, in excess of limits established to 
maintain safe operating conditions, was detected by onboard 
hazardous gas detection systems.  Leakage was detected both in 
the aft compartment and external to the liquid hydrogen external 
tank/orbiter umbilical assembly.  

     A subsequent tanking test, that incorporated special ground 
instrumentation, further isolated the leak to the free space 
between the two halves of the umbilical assembly.  The umbilical 
provides capability to load propellant into the external tank and 
transfer propellant from the external tank to the Space Shuttle 
main engines during launch.  The umbilical disconnect assembly is 
the separation point between the orbiter and the external tank 
after main engine cutoff.  

     The design of the umbilical disconnect has remained the same 
throughout the Shuttle flight program except that a safety 
modification to incorporate a valve latch, which precludes 
inadvertent closure, was authorized after the Challenger 
accident.  Data from the tanking test determined that the design 
changes incorporated by this modification did not contribute to 
the leakage.

     Following rollback and orbiter demate, the LH2 External Tank 
(ET) side of the umbilical was removed and tested at Rockwell 
International, Downey, Calif.  The testing was performed under 
precisely controlled liquid hydrogen test conditions.  No leaks 
were detected.

     On June 29, 1990, NASA conducted a modified propellant 
loading test of the STS-38 Space Shuttle vehicle to ensure the 
safety and integrity of the orbiter/ET umbilical.  The test 
revealed a hydrogen leak.  The results indicate the leak is in 
the vicinity of the umbilical mating plates.  It appears to be 
primarily from the 17-inch line but possibly with a contribution 
from the 4-inch line.  The leak is flow rate and temperature 
dependent.  It is not as high as STS-35 but it exhibits many of 
the same characteristics.  

Current Status

     An extensive investigation is being performed to isolate the 
source of the leakage observed on both the STS-35 and STS-38 
vehicles.  

     Columbia is in the Orbiter Processing Facility (OPF).  The 
orbiter side of the LH2 umbilical from Columbia was shipped to 
Rockwell-Downey on Saturday and is being installed in a test 
stand which can test the orbiter and ET umbilicals in a mated 
configuration.  Engineers expect to begin cryogenic hydrogen 
testing of the umbilical on Thursday to further isolate the 
source of the leak.  

     In the interest of safety, all potential leak sources, 
including the very low probability of a parent metal flaw, are 
being investigated.  A detailed investigation of all aspects of 
the STS-35 and STS-38 component history, including acceptance 
test procedure requirements and data, and design changes being 
performed.  

     Processing of the STS-38 vehicle has been suspended.  
Engineers are continuing troubleshooting efforts on the Shuttle 
vehicle at Launch Pad 39-A.  Today, the external tank will be 
pressurized and leak checks conducted in the area of the orbiter-
to-external tank umbilical.  Another special tanking test is 
being considered using special leak detection sensors to help 
pinpoint the leak's location.


Program Team

     Leonard Nicholson, Deputy Director, Space Shuttle Program, 
will lead the NASA/industry team charged with analyzing the cause 
of the leak and determining corrective actions.

     Under Nicholson, four work teams have been formed:

     - Design and Analysis Team - to assess the flight hardware 
and ground support equipment hardware designs, fabrication and 
test programs, and assess ground processing procedures to ensure 
compliance with design intent.

     - Hardware Processing Team - to review all Kennedy Space 
Center procedures associated with the ET and orbiter processing, 
including "as run" data, problem reports, processes, procedures 
and personnel certification.

     - Data Analysis Team - to analyze data from the tanking 
tests and applicable launches to identify trends, define 
additional tests and instrumentation needed to understand and 
isolate the source of the leak and review all tests currently 
planned for completeness and appropriateness.

     - Fault Tree/Test Requirements Team - to develop and provide 
to the other teams a fault tree identifying failure scenarios, 
and identify additional tests and data requirements.

     An independent team, headed by Wayne Littles, Deputy 
Director of Marshall Space Flight Center, Huntsville, Ala., also 
has been formed with senior NASA and contractor representatives 
who are experts in liquid hydrogen technology.  While they will 
work independently of the investigation teams, they will report 
to Nicholson, and support the team, as appropriate.


Acceptance Test Procedure (ATP)

     The ET/Orbiter umbilical is fully developed and qualified 
flight hardware that has met all of the functional requirements 
stipulated by specification.  

     An acceptance test procedure, which is a screen to verify 
the manufacturing process for each component delivered, has been 
developed from performance requirements.  The ATP stipulates the 
use of liquid nitrogen as an acceptable substitute for liquid 
hydrogen, which is extremely dangerous and volatile to handle.  

     The disconnect component specification allows a maximum 
hydrogen leakage of 200 standard cubic inches per minute (scim) 
for the mated disconnect assembly at cryogenic temperature (150 
scim for the ET and 50 scim for the orbiter).  The ATP has a more 
stringent limit on the ET disconnect, which is 50 scims.  This 
allowable leakage rate was established to compensate for the 
temperature and media differences between liquid nitrogen and 
liquid hydrogen.  The orbiter disconnect underwent ATP testing 
with liquid hydrogen because there are a limited number of 
production units.


Future Steps

     Until the leak investigation is completed, Shuttle flights 
have been suspended.  Returning the Shuttle fleet to flight 
status is the highest priority in the Space Flight Office, and 
every available resource within the Shuttle program is being 
brought to bear on solving this problem.  NASA is confident that 
the source of the leak can be isolated quickly and the problem 
fixed with minimum disruption to the Shuttle flight program.

     Independent of these events, a component redesign to replace 
the current umbilical disconnect with a new design has been 
underway and is well into the preliminary design phase.  The new 
disconnect incorporates significant safety improvements, 
including redundant seals at all locations.

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.military,clari.news.top
Date: 2 Jul 90 18:23:04 GMT

	CAPE CANAVERAL, Fla. (UPI) -- NASA engineers are considering
everything from misaligned fuel tanks to the remote possibility of
sabotage to explain the elusive fuel leaks that have grounded the
shuttle fleet, officials said Monday.
	Agency managers are considering another fueling test for the
shuttle Atlantis, possibly as early as this weekend, to pinpoint a tiny
leak in the ship's 17-inch-wide fuel line ``disconnect'' fitting that
forced NASA to cancel the ship's launch later this month on a secret
military mission.
	Engineers said Monday Atlantis's leak does not appear at all
similar to the one that grounded Columbia and that another fueling test
might show the leakage detected during a test last week showed up only
because of the location of a critical sensor and a lack of wind to
dilute the concentration.
	In California, meanwhile, engineers are preparing to pump frigid
liquid hydrogen through disconnect hardware removed from Columbia in a
test Thursday to duplicate the much larger leak that forced NASA to
cancel the ship's May 30 liftoff.
	Regardless of what ultimately may be required to fix the grounded
shuttles, engineers say it will be virtually impossible for NASA to
launch both Columbia and Atlantis as planned before Discovery's
high-priority Oct. 5 flight to carry the Ulysses solar probe into orbit.
	``We're right on the edge where two flights no longer fit before
Ulysses and we'll be addressing that in the next few days,'' said
William Lenoir, NASA's associate administrator for space flight.
	NASA managers are considering the possibility of launching Atlantis
before the Ulysses mission, assuming the leak issue is resolved, and
then launching Columbia after Discovery.
	Columbia was grounded when sensors detected a massive fuel leak
during propellant loading the night before the ship's planned launch in
May.
	A subsequent fueling test showed hydrogen leakage in the engine
room as well as in the cavity between the two halves of the 17-inch
disconnect fitting, which allows the shuttle's propellant lines to
separate before the tank is jettisoned in space.
	Hydrogen concentrations higher than the allowable limit of 40,000
parts per million -- 4 percent -- were detected in the engine compartment
and up to 58 percent in the disconnect cavity.
	In sharp contrast, no hydrogen leaked into Atlantis's engine room
last week during its fueling test and the concentration in the
disconnect cavity was around 8 percent.
	There was virtually no wind at launch pad 39A for Atlantis's test
and engineers could not rule out the possibility that a sensor located
very close to a 4-inch hydrogen line in the disconnect fitting was
picking up signs of leakage that might otherwise have been within
allowable specifications.
	Lenoir said five teams have been assesmbled to look into the design
of the 17-inch disconnect fitting, its history, ground processing,
assembly techniques and so on to find evidence of anything that could
explain the leakage.
	``After as many flights as we've had ... all of a sudden two in a
row seems more than coincidental,'' he said. ``That seems to weigh
against a generic problem that's been there lurking all along. It would
seem there's something different that we've either done in manufacturing
this hardware or in the way we're using it.''
	A space shuttle is assembled for launch by bolting the spaceplane
to giant fittings on the side of the external fuel tank where the tank's
propellant lines enter the belly of the orbiter.
	The attachment fittings on the tanks used by Columbia and Atlantis
are out of line by a record amount and engineers are looking into the
possibility that the resulting misalignment might have something to do
with the leakage.
	``There's always some small degree of misalignment,'' Lenoir said.
``The last two attempts, while within the ability, we believe, of the
shuttle system to accommodate, they are the largest offset of all the
flights to date.''
	Lenoir also refused to rule out the possibility of sabotage,
although he and NASA Administrator Richard Truly said that appeared to
be unlikely.
	``Yes, we've considered sabotage and we're not proceeding
vigorously down that path,'' Lenoir said. ``We may come back down that
path once we understand technically what is the problem.''
	Truly said, ``If you set out to sabotage the system, you'd have to
carefully design a flaw that could be introduced that would pass every
pre-flight test we had but then would fail only when we filled the tank
with (supercold) hydrogen. It seems like if you were a saboteur you'd
find a solution that was simpler than that.''

    	Once again NASA has said that a condition lies outside the range of
    past experience, but it SHOULD be OK. [re. misalignment of orbiter to
    tank umbilical] [since the shuttle is the constant, this means the tank
    fabricators have been getting sloppy on the last two/few?].
    	Anybody want to bet that the safe range of misalignments is a lot
    less than what they thought it was (like the safe launch temps. were
    a lot higher than they thought)?  - skeptical Chris

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.top
Date: 4 Jul 90 04:17:33 GMT

	CAPE CANAVERAL, Fla. (UPI) -- Rocket engineers worked through the
Fourth of July holiday Wednesday gearing up for crucial tests to
pinpoint the source of crippling hydrogen fuel leaks that have grounded
NASA's shuttle fleet.
	William Lenoir, NASA's associate administrator for space flight,
said Tuesday it might take another two weeks to resolve the problem and
that another launch pad fueling test will be conducted next week using
the shuttle Atlantis.
	Even so, Lenoir said he does not expect the shuttle fleet to be out
of action much longer and that at least one of two delayed flights
likely will get off the ground before a high-priority October mission to
ferry the Ulysses solar probe into space.
	``I don't expect we'll be down for a long time,'' he said at a news
briefing. ``If I'm here in two months eating crow, please bring some
pepper.''
	Lenoir, giving reporters a detailed update, said engineers will
pump liquid hydrogen back aboard Atlantis's external tank Tuesday or
Wednesday for additional measurements to better isolate the source of a
leak that showed up during a similar test last Friday.
	In the meantime, engineers in California are gearing up to pump
supercold hydrogen through the shuttle Columbia's leaky 17-inch fuel
line ``disconnect'' fitting Thursday or Friday to duplicate launch
conditions in the laboratory where the problem can be more easily
assessed.
	Leaks somewhere in the massive disconnect fittings forced NASA to
indefinitely delay Columbia's planned May 30 liftoff on a 10-day
astronomy mission and Atlantis's mid-July flight to ferry a secret
Pentagon payload into orbit.
	In both cases, the leaks were traced to the fittings where a
17-inch-wide hydrogen fuel line from the external tank butts up against
the belly of the orbiter. The disconnect umbilical is what allows the
fuel line to break apart in space so the tank can be safely jettisoned.
	Lenoir said engineers are studying a variety of possible
explanations for the leakage, including the effects of slightly
misaligned fuel tanks, damaged or faulty seals, improper tightening of
bolts holding the disconnect hardware together and so on.
	But until all the test results are in, he said, it will not be
possible to determine what might be required to fix the trouble or when
the shuttle can resume flying.
	Problems with the disconnect hardware cannot be fixed at the launch
pad, and Atlantis, like Columbia before it, ultimately will have to be
hauled back to a rocket assembly building and removed from its tank for
an inspection and possible repairs.
	The two halves of Columbia's disconnect hardware -- valves and seals
on the tank side of the joint and matching hardware mounted in the
shuttle's belly -- were removed and shipped to a Rockwell International
facility in Downey, Calif., for exhaustive tests.
	Engineers had planned to bolt the assembly together and pump liquid
hydrogen through it Thursday in a critical test to precisely locate the
leak. But Lenoir said the test could be delayed to Friday.
	The problem cropped up when NASA managers realized a seal used by
Columbia's disconnect assembly had not been sent to Downey along with
the rest of the hardware. The seal has several blemishes but engineers
do not know if they contributed to the leak or not.
	``They're all very, very small,'' an official said. ``You'd have to
use a magnifying glass to see them.''
	Engineers hope the test will be able to duplicate the launch pad
conditions that created the original leak and provide insights into how
to fix the problem.

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.top
Date: 6 Jul 90 20:15:50 GMT

	CAPE CANAVERAL, Fla. (UPI) -- Slightly misaligned fuel tanks did not
cause the hydrogen leaks that grounded NASA's shuttle fleet, officials
said Friday, focusing attention on a series of weekend tests in
California expected to help pinpoint the problem.
	But if those tests and others at the Kennedy Space Center next week
fail to locate or duplicate the leak for further analysis, ``in all
honesty I'm not sure where we go from there,'' shuttle chief William
Lenoir said. ``That's a tough one. Maybe we all go on vacation.''
	Along with tests in California over the weekend, technicians at the
Kennedy Space Center are gearing up for another fueling test for the
shuttle Atlantis next Friday in an effort to track down a leak in the
ship's 17-inch-wide fuel line ``disconnect'' fitting like one that
grounded the shuttle Columbia in May.
	At the same time, NASA and contractor engineers across the nation
are reviewing manufacturing records, flight histories, assembly
procedures and the design of the critical 17-inch disconnect fittings to
find out what caused crippling hydrogen fuel leaks that have grounded
the shuttle fleet.
	The 17-inch disconnect ``umbilical,'' located where propellant
lines from the external tank enter the belly of the orbiter, allows the
tank to be safely jettisoned after reaching space. It is made up of
valves, seals and plumbing mounted inside the shuttle, along with
matching hardware on the external tank.
	While NASA engineers do not yet know what is causing the leaks,
they have been able to eliminate one possibility: the effect of slightly
misaligned fuel tanks.
	The external tanks used by both Columbia and Atlantis came from the
factory with mounting hardware that caused the shuttle to be slightly
``cocked'' to one side after attachment. The effect was for the nose of
the ship to be an inch or so from vertical as viewed from above the back
of the ship.
	``We have more or less exonerated what we have come to call the
crooked tank issue,'' said Lenoir, associate administrator for space
flight. ``We have analyzed that and re-analyzed that ... and, try as we
might, we cannot make that come even close to anything that would make
us suspicious.''
	Columbia's planned launch May 30 on a 10-day astronomy flight was
called off just six hours before liftoff, when hydrogen gas was detected
leaking into the ship's engine compartment. Atlantis's mid-July launch
on a military mission was put on hold after a similar leak showed up
during last week's fueling test.
	In both cases, the leaks were traced to the ships' massive 17-inch
disconnect fittings. But the precise location of the leakage inside the
disconnect assemblies remains unknown.
	Weekend tests in Downey, Calif., may pinpoint the source of the
leak once and for all.
	Engineers with shuttle-builder Rockwell International began a
series of tests Friday with Columbia's disconnect hardware in a bid to
duplicate the leakage under carefully controlled laboratory conditions.
	With the disconnect hardware hooked back up in a simulated launch
configuration, engineers pumped room-temperature gases through the
system Friday, setting the stage for tests Saturday and Sunday involving
frigid liquid hydrogen rocket fuel.
	``It's apt to be Sunday before we have really done the most
rigorous testing with liquid hydrogen,'' Lenoir said. ``We should be
able to pinpoint that leak and talk about the magnitude of the leak.''
	The leak only shows up when the shuttle plumbing is exposed to the
minus 420-degree temperature of volatile liquid hydrogen and engineers
hope they can duplicate the leak under laboratory conditions.
	But Lenoir cautioned the leak could still elude detection for two
reasons: the test rig cannot pump hydrogen through the umbilical at the
same rates as at the launch pad; and in the process of disassembling and
reassembling the hardware, ``we may have inadvertantly fixed the
problem.''
	Regardless of what turns out to be wrong, it appears unlikely
Atlantis can be ready for takeoff before mid-August and equally unlikely
Columbia can get off the ground before the shuttle Discovery's
high-priority Oct. 5 launch to ferry the Ulysses solar probe into space.
	Back at the Kennedy Space Center, engineers are gearing up to pump
hydrogen back aboard Atlantis's external tank next week to further
isolate the location of the leak that grounded the ship's July flight.
	Special ``baggies'' will be put in place around the disconnect
fitting to trap any hydrogen that escapes, making it easier for
engineers to pinpoint the source and magnitude of any such leakage.
	Regardless of the exact location of the leak, the fact that it
involves the disconnect fitting means Atlantis, like Columbia before it,
likely will have to be hauled off the launch pad and returned to the
Vehicle Assembly Building so the ship can be removed from the tank to
give engineers access to the suspect hardware.
--
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to [email protected].  

    I heard on the radio this morning that NASA would have a news
    conference today on this subject.  Any word yet?
    
    Tony

    I heard through the grapevine that the source of the leak has been
    found. I still have no word on the exact cause or when Shuttle flights
    will resume.
    
    				Drew
    

I heard that they reproduced it at Downey and restricted it to a certain area,
but had not actually *found* it.

Burns

    Re:.11
    	Well, "found it" was the words my source used. I also have heard
    more details about the leak. Apparently it has been narrowed down to
    the teflon seal betweeb the external tank and the shuttle's fuel line.
    
    				Drew
    

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.military,clari.news.top
Date: 10 Jul 90 04:15:34 GMT

	CAPE CANAVERAL, Fla. (UPI) -- More tests are needed to pinpoint the
source of an elusive hydrogen fuel leak that grounded the shuttle
Columbia, but engineers are focusing on a critical Teflon seal as one
possible culprit, officials say.
	William Lenoir, NASA's associate administrator for space flight,
said at a Washington news conference Monday that nothing has been ruled
out and that until the problem is fully characterized and corrected, the
shuttle fleet will remain grounded.
	``We have not yet eliminated any potential source from our suspect
list,'' he said. ``Certainly all of our seals ... are still on our list,
and we're going to dig into them. The main disconnect seal is our
primary suspect. That's what we're tunneling in on.''
	The problem involves Columbia's 17-inch-wide ``disconnect''
fitting, the massive assembly that connects fuel lines from the ship's
external fuel tank to matching pipes in the belly of the orbiter.
	Engineers at a Rockwell International test facility in Downey,
Calif., conducted a critical series of tests over the weekend to isolate
the leak using Columbia's disconnect fitting. While a leak was
confirmed, its precise location has not yet been identified and more
tests were ordered.
	``They found a little (leak), but not a lot,'' Columbia skipper
Vance Brand said in a telephone interview from Houston. ``I think, so
far, the tests they had over the weekend haven't given us the answer.''
	But engineers are increasingly confident that additional work will
finally pinpoint the elusive leak in Columbia's 17-inch disconnect
fitting that grounded Brand and his six crewmates just six hours before
their planned May 30 liftoff on an astronomy mission.
	A similar leak forced NASA managers to postpone the shuttle
Atlantis's planned mid-July launch on a military flight, effectively
grounding the fleet.
	At the Kennedy Space Center, engineers are gearing up to pump
supercold liquid hydrogen rocket fuel aboard Atlantis early Friday in a
bid to finally isolate the source of its leakage.
	The disconnect fitting is a massive assembly of valves, seals,
explosive bolts and other hardware that allows fuel to flow from the
ship's external tank to its three main engines during liftoff. As its
name implies, the disconnect fitting allows the shuttle's external tank
to be disconnected and jettisoned once the orbiter reaches space.
	The fuel lines from the external tank butt up against matching
lines in the belly of the orbiter and they are bolted together at the
disconnect assembly. Where the two sections join is a spring-loaded
Teflon ``interface seal'' to ensure a leak-free fit.
	Lenoir said records indicate the possibility that the interface
seal used by Columbia's disconnect system was compressed slightly at one
time, possibly allowing a small leak to occur.
	He said the leak rate corresponded to what could be expected from a
hole 40-thousandths of an inch in diamter. But he stressed that
additional tests were required to resolve the matter one way or the
other.
	It is not yet known whether the problem with Atlantis's 17-inch
umbilical is the same as the one that grounded Columbia. To find out,
engineers plan to pump hydrogen back aboard Atlantis's external fuel
tank early Friday, duplicating a test carried out June 29.
	But this time around, various parts of Atlantis's disconnect will
be enclosed in special plastic baggies to trap any gas that might
escape. In that fashion, engineers hope to isolate the source of the
leak.
	NASA originally hoped to launch Columbia and Atlantis before the
high-priority launch of the shuttle Discovery on Oct. 5 to carry the
European Ulysses solar probe into space. Lenoir said it now is
``extremely unlikely'' both flights can be launched before Discovery's
mission.

From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Newsgroups: clari.tw.space,clari.news.aviation,clari.news.military,clari.news.urgent
Date: 13 Jul 90 20:51:44 GMT

	CAPE CANAVERAL, Fla. (UPI) -- Engineers believe they have pinpointed
leaks grounding the shuttles Columbia and Atlantis, and officials said
Friday at least one orbiter should get off the ground before a
high-priority October flight by the shuttle Discovery.
	William Lenoir, associate administrator for manned spaceflight,
said data from a critical fueling test Friday at the Kennedy Space
Center indicates the small leak that grounded Atlantis may involve a
relatively easy-to-fix Teflon-coated ``flange seal'' in a 17-inch-wide
fuel line joint.
	If further testing confirms preliminary results, Atlantis, which
has priority over Columbia, could be ready for launch on a secret
military mission by mid-to-late August if repair work goes well.
	As for Columbia, Lenoir said engineers at a test facility in
California believe they have traced that shuttle's leak to one of two
seals around the rods used to move giant valves in a massive
``disconnect'' fitting, which allows the ship's external fuel tank to be
jettisoned in space.
	``We are not there yet,'' Lenoir said, but ``we have it surrounded
and we're closing in on it.''
	Shuttle program director Robert Crippen, speaking to reporters from
the Johnson Space Center in a cross-country teleconference, was more
bullish, saying he was ``very pleased'' with the test results.
	``We have two different problems we're dealing with on the two
different vehicles,'' Crippen said. ``We can say we do not have a
generic problem, which would have been much more difficult to deal
with.''
	As for Atlantis, engineers said more data analysis was needed to
resolve the matter once and for all.
	But Lenoir said it would be relatively easy to replace or repair
the flange seal and he would not rule out the possibility that Atlantis
could be safely launched ``as is.'' But such a decision likely would run
into major opposition regardless of engineering data to the contrary.
	``We're fairly certain we have a leak in the external
tank-to-umbilical flange ... and we believe that's the only leak,''
Lenoir said. 
	If further analysis confirms the flange seal as the culprit, the
seal could be replaced or cleaned in NASA's Vehicle Assembly Building.
But engineers have not ruled out the possibility of simply adjusting the
tightness of the 48 bolts that hold the flange together.
	Engineers believe Columbia was hobbled by trouble with a seal
around the mechanical linkage used to drive one of two big ``flapper
valves'' inside the ship's 17-inch disconnect. If so, Columbia is
already fixed because its umbilical has been replaced with a new unit
built for the shuttle Endeavour.
	``On Columbia's hardware ... we think it's on the orbiter side,''
Lenoir said. ``If that's true, then Columbia's already fixed because it
has a different umbilical already connected to it.''
	But he stressed that additional testing is necessary before any
final decisions are made and he said it was extremely unlikely both
Atlantis and Columbia can be launched before the shuttle Discovery's
high-priority Oct. 5 takeoff to ferry the Ulysses solar probe into
space.
	``We're confident ... that we'll be getting one flight off before
Ulysses,'' he said. ``It's unlikely that we'll get two. All other things
being equal, we're biased for getting the DOD flight off first.''
	Atlantis's fueling test began shortly after 9 a.m. EDT, two hours
late, when supercold liquid hydrogen began flowing into the ship's
external tank through the disconnect fitting in the belly of the
orbiter.
	Leaks of explosive hydrogen somewhere in the 17-inch umbilical
forced NASA to delay Atlantis's mid-July launch on a military mission as
well as the shuttle Columbia's planned May 30 liftoff on a 10-day
astronomy flight.
	Engineers initially had problems tracing the source of either leak,
prompting a series of tests to isolate the problem area.
	In Friday's test, hydrogen was detected near the flange, or joint,
where the 17-inch-wide fuel line from the shuttle's external tank bolts
onto the disconnect umbilical.
	``On Atlantis ... it doesn't look like anywhere near the end of the
world and we're very close to understanding our problem and getting back
to flying again,'' Lenoir said.
	Columbia was grounded six hours before its planned May 30 blastoff
when sensors detected hydrogen gas leaking into the ship's engine
compartment. A subsequent test traced the leak to somewhere in the
disconnect fitting and Columbia was hauled off the launch pad for
repairs.
	NASA then proceeded with plans to launch Atlantis this month on a
secret military mission, but another leak showed up in a fueling test
two weeks ago.
	While both leaks appeared to involve the 17-inch disconnect
fitting, they were very different in magnitude. Columbia's fitting
leaked far more hydrogen than Atlantis's and no fuel was detected in
Atlantis's engine compartment.
	Columbia's disconnect hardware was removed and shipped to a
Rockwell International facility in Downey, Calif., for a series of
laboratory tests this week to pinpoint the source of the original leak
that began NASA's long, launchless summer.
	The umbilical was reassembled and filled with liquid hydrogen last
weekend and while a leak was quickly detected, engineers were unable to
immediately pinpoint its source.

    Just tightening the bolts did not work.  Of course the press played it
    as yet another failure, when, in fact, it was a failure that was really
    expected.
    
    Burns
    

    Hi,
    
    is there really nothing new since the last reply ??
    I'm interested for more information here on the other side of the sea
    speak like Germany.
    
    Wolfgang
    

The STS-35, STS-41, and STS-38 topics have the most recent information on
the status of the shuttles.

The shuttle fleet is no longer grounded at this time - although Columbia
(OV-102) is.   If there is a fuel leak with Discovery during the upcoming
launch attempt, then I would suspect that NASA would once again ground
all the shuttles.  Until that happens, I don't expect to be adding any news
to this topic.

- dave

From: [email protected] (Ken Hollis)
Newsgroups: sci.space.shuttle
Subject: Re: LH2 Leak (Long File...)
ate: 17 Nov 90 06:16:28 GMT

Greetings and Salutations:

>From: [email protected] (Greg Hennessy)
>Subject: Re: Causes for Columbia leaks ??
>In article <[email protected]> [email protected] writes:
>#Now that Columbia seems to be back together and ready to launch...
>#
>#I don't recall any mention of the actual causes of the hydrogen leaks that
>#plagued it over the summer.  Maybe I just wasn't paying real close
>#attention this time around.  Any quick explanations ??

>The problem over the summer was in the 17 inch disconnect valve, which
>had scratches in the teflon seals. The scratches were caused by small
>glass beads. How the beads got there is unknown, but I have hard at
>least two theories. When they were putting back together the engines
>after fixing the disconnect valve, two seals were crushed, causing
>leaks. In  fixing one leak they introduced two more. The procedures
>were changed to prevent a re-occurrence of this event.
>-Greg Hennessy, University of Virginia

Let's start off correctly.

Columbia (OV-102)
STS - 32 was stacked on MLP-3 (Mobile Launch Platform) in the VAB (Vehicle
Assembly Building), the first use of MLP-3 for the shuttle program.  It was
then transferred to Pad - A for launch.  Pad-A had just finished a major
modifications program to get it upgraded to the same extent as Pad-B had been
earlier.  This did include some work on the LH2 system.  The external tank had
also been modified for the ECO (Engine Cut-Off) sensors.  All of these
operations require sand paper of some sort .  Launch was on 0735 a.m. EST
1/9/1990.  The payload was the SYNCOM IV-5 geostationary communications
satellite, also known as LEASAT.  The LDEF (Long Duration Exposure Facility)
was also retrieved (the great killer tomato seed experiments...).

OV-102 was returned to the OPF (Orbiter Processing Facility) for standard LH2
system maintenance.  Upon removing a component (PV14, E-1 recirc valve)
therein was discovered small pieces of what was later analyzed to be corundum
(a type of sandpaper).  The entire LH2 system was then thoroughly inspected,
and all traces of the corundum removed.  One of the inspections required
access to a screen that catches all particles going to the engines, the
prevalve screen.  To boroscope this screen a small part, the detent (a
retaining device for the prevalve), was removed.  Because of the placement of
this part, re-installation (with its teflon (naflex) seal) was with the tech
laying on his back.  The seal slipped upon reinstallation (unknown to all) on
PV5 & PV6 (E-2 & E-3 LH2 prevalve respectively) causing the seal not to seat
at cryo conditions (but it sealed very nicely, thank-you, at ambient
temperatures).  I will give you a hint,  Cause #1.

On the ET (External Tank) there is a 17" flapper valve to match the 17"
flapper valve on the vehicle side.  These valves allow the flow of LH2 from
the ET to the SSME's (Space Shuttle Main Engines) during flight.  The
actuation of both of these valves comes from the vehicle.  There is an arm
that rotates a shaft hooked up to the flapper, and the flapper opens.  There
is one teflon seal on each end of that shaft that rotates the flapper. 
Sometime after manufacture, due to improper storage at the vendor, some glass
beads got imbedded into these seals.  Cause #2.

When OV-102 was tanked, there were leaks from both inside & outside the aft
(there had not been any leakage of this magnitude before on any vehicle). 
Isolation tests were not fully successful because of the two different areas
of leaks.  OV-102 was rolled back to the OPF and the 17" disconnect from
OV-105 was placed on OV-102 in hopes that it wouldn't leak.  All joints were
re-leak checked with the detent cover seal on PV6 found crushed.  This seal
was R&R'ed.  Tests with the ET 17" disconnect at that time were inconclusive,
but later it was found that the ET half of the disconnect leaked.  In the
meantime OV-104 was rolled out, tanked & it leaked.  See below for that story.

OV-102 was restacked, and rolled to Pad-A, where it was tanked & it leaked. 
Leakage, however, was noted only inside the aft this time (at a lower level). 
The assumption from before was that the leakage was large enough to also enter
the aft.  Intensive leak checks of all joints at ambient temperature followed.
 Many bolts had their torque checked.  The only out of spec conditions found
were a bolt with an upside down washer & a very small leak at the PV5 detent
seal.  PV5 detent seal was then found crushed, and R&R'ed.  The tanking test
was run & successful.

Scheduled for this weekend are SSME FRT's & next week preps for launch.

OV-104
The DOD mission that was launched yesterday (11/15/90) was originally stacked
& ready to go earlier this year.  As a check of the system to make sure that
OV-104 didn't have the same problems as OV103, NASA decided to run a tanking
test.  It leaked.  Extensive testing showed that a small amount of hydrogen 
(1 SCFM, Standard Cubic Feet per Minute) could show up (on a calm day, like
when they tanked) as a large leak (6% --> 10%).  Hydrogen expands about 700
times when going from liquid to gas.  It also showed that OV-104's problem was
on the ET 17" side, not the orbiter.  OV-104 was rolled back to the OPF & the
ET 17" disconnect was changed out.  OV-103 was launched with Ulysses.  OV-104
was rolled to Pad-A, and OV-102 To Pad-B, hence the shuttle shuffle.

The disconnect that leaked also had the same problem as Columbia, ie the
teflon seals were damaged (all ET halves of that lot number have been flagged
& inspected last I heard).  OV-104 was tanked with LH2 & LO2 as a total system
check & it didn't leak.


>From: [email protected] (Greg Cronau)
>Subject: Re: Causes for Columbia leaks ??
>The result has been the bane of diagnosticians for a long time:
>When they set up a system to allow them to watch it real carefully,
>It didn't leak!
>[email protected]

As per above, all discrepant conditions were found and corrected.

Ken Hollis

ProLine:  gandalf@pro-canaveral         
Internet: [email protected]
UUCP:     crash!pro-canaveral!gandalf

From: [email protected] (Peter E. Yee)
Date: 22 Nov 90 04:27:18 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
 
 
          Bruce Buckingham
          407/867-2468                                      Nov. 14, 1990
 
          KSC RELEASE NO. 181 - 90
 
 
          WORK ON HYDROGEN DISPERSION SYSTEM COMPLETED ON MOBILE LAUNCHER
          PLATFORM
 
               Following a series of liquid hydrogen leaks on the orbiters
          Columbia and Atlantis this past summer, an external tank/orbiter
          umbilical hydrogen dispersion system was recently designed and
          installed on one of three mobile launcher platforms at Kennedy
          Space Center.
 
               The system, now installed on mobile launcher platform number
          two in the Vehicle Assembly Building, will also be installed on
          the remaining two MLPs following their current assignments to
          support Space Shuttle missions this year.
 
               The dispersion system is designed to provide a nitrogen rich
          air flow around the hydrogen 17-inch disconnect line which is
          located between the orbiter and external tank. The system
          consists of a supersonic gaseous nitrogen nozzle, a nozzle
          support pipe, a blast cover, and a 2-inch gaseous nitrogen supply
          line.
 
               The dispersion system was designed to reduce oxygen present
          and disperse hydrogen concentrations from a potential leak of up
          to 17,000 scim (standard cubic inches per minute) or 10 scfm
          (standard cubic feet per minute). The system will provide
          sufficient air flow around the 17-inch disconnect to prevent
          hydrogen concentrations from exceeding four percent. Hydrogen
          concentrations greater than four percent in an oxygen-rich
          environment present a potential hazardous situation.
 
               The nozzle on the dispersion system is made of stainless
          steel and was designed to provide for a supersonic volumetric
          flowrate of 750 scfm at 125 psi.
 
               Firing room personnel will be able to control the dispersion
          system from the Launch Control Center. From the LCC, varying flow
          rates of the dispersion system and nozzle adjustments can be
          operated remotely. The system is scheduled to be available for
          use during the launch of Discovery on Shuttle mission STS-39.
 
               NASA and Boeing Aerospace Operations were responsible for
          the design and construction of the system's nozzle components.
          Engineers for NASA and the architect and engineering firm of
          Reynolds, Smith and Hills were responsible for the design of the
          structural supports for the nozzle and supply line.