UPDATE # 32 - December 23, 1997

PART 1: Happy holidays
PART 2: Working on a tile damage mystery
PART 3: Getting CHeX ready to fly and then launching it
PART 4: Status of Columbia's processing
PART 5: Subscribing/unsubscribing: how to do it

HAPPY HOLIDAYS

The Space Team Online staff sends you our best holiday wishes.
Here's hoping your Christmas is most merry and your Hanukkah is
quite cheery and that the New Year brings only good things.

These Space Team Online updates will be taking a holiday break
and will return the week of January 5, 1998.

WORKING ON A TILE DAMAGE MYSTERY

Greg Katnik
http://quest.arc.nasa.gov/space/team/katnik.html

December 23, l997
STS-87 rolled to a stop; the mission was complete! That statement
is true for the flight of the Columbia, however a new
mission began when the wheels of the Columbia came to a stop:
the post flight inspections. My division is responsible for the
overall analysis of these inspections and we insure that all
changes made, due to these inspections, do not affect other areas
that may jeopardize the flight-worthiness of the shuttle. This
division does not focus on one specific area, but analyzes all
information and ensures that all aspects are kept in balance.

Immediately after the Columbia rolled to a stop, the inspection
crews began the process of the postflight inspection. As soon as
the orbiter was approached, light spots in the tiles were observed
indicating that there had been significant damage to the tiles. The
tiles do a fantastic job of repelling heat, however they are very
fragile and susceptible to impact damage. Damage numbering up
to forty tiles is considered normal on each mission due to ice
dropping off of the external tank (ET) and plume re-circulation
causing this debris to impact with the tiles. But the extent of
damage at the conclusion of this mission was not "normal."

The pattern of hits did not follow aerodynamic expectations, and the
number, size and severity of hits were abnormal. Three hundred
and eight (308) hits were counted during the inspection, one hundred
and thirty two (132) were greater than one inch. Some of the hits
measured fifteen (15) inches long with depths measuring up to
one and one-half (1 1/2) inches. Considering that the depth of the
tile is two (2) inches, a 75% penetration depth had been reached.
Over one hundred (100) tiles have been removed from the
Columbia because they were irreparable. The inspection revealed
the damage, now the "detective process" began.

During the STS-87 mission, there was a change made on the
external tank. Because of NASA's goal to use environmentally
friendly products, a new method of "foaming" the external tank
had been used for this mission and the STS-86 mission. It is
suspected that large amounts of foam separated from the external
tank and impacted the orbiter. This caused significant damage to
the protective tiles of the orbiter. Foam cause damage to a ceramic
tile?! That seems unlikely, however, when that foam is combined
with a flight velocity between speeds of MACH two to MACH
four, it becomes a projectile with incredible damage potential. The
big question? At what phase of the flight did it happen and what
changes need to be made to correct this for future missions? I will
explain the entire process.

The questions that needed to be answered were:

* what happened?
* what phase of flight did it happen in?
* why did it happen?
* what corrective action is required?

At this point, virtually every inch of the orbiter was inspected and
all hits were documented and mapped to aid in visualizing the
damage. Maps were constructed of the lower surface, the left and
right surfaces and the top surface of the orbiter. At this point, a
"fault tree" was created. The fault tree provides a systematic
approach in considering all possibilities of what may have
happened. Everything that is on the fault tree is considered to be
legitimate until it is totally ruled out. Some of the considerations
were where the damage occurred -- in the OPF, in the VAB, or on
the pad before launch. These were quickly eliminated because an
inspection at T-3 ("t minus three") hours takes place on each
mission and everything was normal. 

After these and many other considerations were eliminated, the focus
was placed on the ascent, orbit and re-entry phase of the mission. Because
of the fore and aft flow characteristics of the damage sites, and the
angle of penetration, the ascent phase seemed most likely. The orbit
phase of flight was eliminated because the characteristics of these
types of hits (most likely meteorites or space debris) occur in a
random pattern and direction. Re-entry was eliminated because
the "glazing and re-glassifying" of the tiles due to heat upon
re-entry (a normal process) indicated that the damage had
occurred prior to this phase. The fault-tree was now pointing to
the ascent phase.

The pictures that were taken by cameras mounted in the orbiter
umbilical began to give the first clues. These cameras are
designed to turn on during the solid rocket booster (SRB)
separation, and turn off after the separation is complete, thereby
recording the event. This process occurs once again when the
external tank separates from the orbiter. The initial review of these
photographs did not reveal any obvious damage to the external
tank. No foam missing, no "divots" (holes) and no material loss.
Everything appeared normal. The SRBs were then focused on for
the answers. After inspection of the SRBs, no clues were found.
In fact, the solid rocket boosters looked to be in great condition.


Where to now? The external tank photographs were magnified
and reviewed once again. This time some material loss was noted,
but not in a significant degree. The attention was now focused on
the crew cabin cameras. These cameras gave more of a side view
of the external tank as it tumbled back to Earth. These
photographs revealed massive material loss on a side of the
external tank that could not be viewed by the umbilical cameras!

Where did that leave us? One of the questions had now been
answered. The ascent phase of flight was when the damage
occurred. With the information provided by the photography and
the mapped flow of damage, a logical reason could be established
as to "what" happened. It was determined that during the ascent,
the foam separation from the external tank was carried by the
aerodynamic flow and pelted the nose of the orbiter and cascaded
aft from that point. Once again, this foam was carried in a relative
air-stream between MACH 2 and MACH 4!

Now the big question -- why? The evidence of this conclusion
has now been forwarded to Marshall Space Flight Center (MSFC)
because this is the design center for the external tank. MSFC will
pursue the cause of damage. Here are some descriptions of some
of the possible causes:

POSSIBILITY 1
The primer that bonds the tank foam to the metal
sub-stream was defective and did not set properly. This
was eliminated as a cause because the photography
indicated that the areas of foam loss (divots) did not
protrude all the way down to the primer.

POSSIBILITY 2
The aerodynamics of the roll to "heads up." The STS-87
mission was the first time this maneuver had ever been
completed.

POSSIBILITY 3
The STS-86 mission revealed a similar damage pattern
but to a much lesser degree than STS-87. The STS-86
tile damage was accepted ruled as an unexplained
anomaly because it was a night launch and did not
provide the opportunity for the photographic evidence the
STS-87 mission did. A review of the records of the
STS-86 records revealed that a change to the type of
foam was used on the external tank. This event is
significant because the pattern of damage on this flight
was similar to STS-87 but to a much lesser degree. The
reason for the change in the type of foam is due to the
desire of NASA to use "environmentally friendly"
materials in the space program. Freon was used in the
production of the previous foam. This method was
eliminated in favor of foam that did not require freon for
its production. MSFC is investigating the consideration
that some characteristics of the new foam may not be
known for the ascent environment.

POSSIBILITY 4
Another consideration is cryogenic loading, specifically
hydrogen (-423 degrees Fahrenheit) and oxygen (-297
degrees Fahrenheit). These extreme temperatures cause
the external tank to shrink up to six (6) linear inches
while it is on the pad prior to launch. Even though this
may not seem much when compared to the circumference
of the external tank, six inches of shrinkage is
significant.

This is where the investigation stands at this point in time. As you
can imagine, this investigative process has required many hours
and the skills of many men and women dedicated to the safety of
the shuttle program. The key point I want to emphasize is the
PROCESS OF INVESTIGATION, which is coordinated amongst
many people and considers all possibilities. This investigation has
used photography, telemetry, radar coverage during the launch,
aerodynamic modeling, laboratory analysis and many more
technical areas of expertise.

As this investigation continues, I am very comfortable that the
questions will be answered and the solutions applied. In fact,
some of the solutions are already in progress. At present the foam
on the sides of the tank is being sanded down to the nominal
minimum thickness. This removes the outer surface, which is
tougher than the foam core, and lessens the amount of foam that
can separate and hit the orbiter.

Check back with Space Team Online for future developments on
this story!

Stephanie Stilson
http://quest.arc.nasa.gov/space/team/stilson.html

GETTING CHEX READY TO FLY AND THEN LAUNCHING IT

November 19, 1997
My role as an Experiment Engineer for CHeX (see below for more
information on CHeX) involved writing and conducting the test
procedures that are used at KSC to prepare CHeX for launch aboard
the shuttle.

My involvement with the team began in January of 1997 when I
visited the Jet Propulsion Laboratory (JPL) in Pasadena, CA. The
purpose of the visit was to become familiar with the experiment
hardware and witness testing procedures being conducted in the
CHeX laboratory. Upon returning to KSC, I began developing
procedures for testing CHeX once it arrived in the Space Station
Processing Facility (SSPF) at KSC.

CHeX arrived at KSC in late March of 1997 and the JPL team
performed some off-line preparations before having CHeX mounted
on the Multipurpose Experiment Support Structure (MPESS) by the
KSC Mechanical Integration Engineers. Once the hardware was in
place, we began the Interface Verification Test (IVT). The purpose of
this test is to ensure that CHeX functions properly when connected
to the simulated orbiter systems such as power, commanding, and
telemetry. This test took a week and some problems were
discovered and corrected. With the completion of the IVT, CHeX
was ready for the Integrated Compatibility Test (ICT).

The ICT is performed with all the USMP-4 experiments powered up
at the same time much like the on-orbit scenario. The purpose of
this test is to ensure that all of the experiments are able to
function properly while sharing resources with the other
experiments. After a successful ICT, USMP-4 was placed inside
Columbia's payload bay in late October 1997. One final test of CHeX
was performed and then it was ready for launch.

At launch minus 65 hours (L-65), a component of CHeX, the Vacuum
Maintenance Assembly (VMA), was activated as part of the launch
countdown sequence. Because of this, the experiment had to be
monitored around the clock. I and two backups took turns doing
this monitoring in Firing Room 3 of the Launch Control Center (LCC).

I reported on console at 10:00 a.m. to begin what is hopefully my
final shift before launch. Everything is looking fine for CHeX
and the orbiter. If the weather holds out, we should have an
on-time launch. As part of the final countdown activities, the
management team performs a poll of the engineers sitting on
console. This poll is performed over the voice loop and is how
the Flight Director determines if all systems are ready for launch.
Since all the CHeX data looks good, I respond to the poll by
saying, "CHeX is go for launch."

At 2:46 p.m., Columbia lifts off the launch pad right on schedule. We
don't get a very good view of the launch from our seats in the Firing
Room but there are plenty of video screens for us to watch. After
Main Engine Cut-Off (MECO) applause fills the firing room. Columbia
has launched successfully!! For many people at KSC, launch is the
end of their work on STS-87. This is not the case for the CHeX team.

Those of us on console quickly gather our things and head
out to the KSC Executive Airport to catch a Lear Jet to the
Marshall Space Flight Center (MSFC) in Huntsville, AL. The rest
of the CHeX team is already there awaiting the point when CHeX
will be fully activated to begin science operations. Because
USMP-4's time in microgravity is limited to 16 days, the
experiment teams will work around the clock to get the most
science data possible. My shift starts at 7:30 p.m. CST; therefore, I
will arrive in Huntsville just in time to report on-shift. By the time
I arrive at the Payload Operations Control Center (POCC) at
MSFC, CHeX activation has been completed, including venting
of the instrument guard vacuum exchange gas into space and the
activation of the absorption pump.

During initial checkout, the primary Germanium Resistance
Thermometers (GRTs) were malfunctioning. This is a big
concern for the team because the lack of this data could have an
impact on the science. There are some CHeX schematics at the
SSPF that might be able to help us troubleshoot this problem so I
made a late night call to one of my backups who quickly gathered
the documents (a big box full) and courier them to Orlando
International for an early morning flight to Huntsville.

Based on a similar scenario that occurred during ground testing at
KSC, the decision was made to cycle power to CHeX in the
hopes of regaining telemetry from the GRTs. To cycle the power
relay, a command must be issued by engineers at the Johnson
Space Center (JSC). Once all affected parties agreed to the plan,
the command was sent. The troubleshooting proved to be the
right move, we now have all GRTs functioning normally! Now
CHeX will be in a hold mode waiting for the absorption pump to
reduce the guard vacuum pressure to an acceptable level. By the
end of my shift at 7:30 a.m. I have been up for close to 24 hours. I
am very tired and can't wait to get to the hotel and crawl into bed.

[Sweet dreams to Stephanie.Stay tuned to Space Team Online for Part 3]
* * * * * * * * * *

Background Information about
CHeX: The Confined Helium Experiment

The Confined Helium Experiment (CHeX) is a part of the United
States Microgravity Payload #4 (USMP-4) aboard the Shuttle
Columbia. It was developed by a joint Stanford/Jet Propulsion
Laboratory team to test theories of condensed matter physics.
CHeX will look at the behavior of bulk, or three-dimensional,
helium as it converts to a two-dimensional state defined by a set
of finely spaced plates. By measuring the change of the properties
relative to the bulk values, the relationship between two and
three-dimensional behavior and the details of the crossover
between them can be obtained.

One way of understanding CHeX is to take a look at
what is happening in the semiconductor industry.
Moore's law states that computer processing power
always doubles every 18 months. Most of this gain
comes from miniaturization. Right now, typical circuit sizes are
around 0.2 microns. Recently, Intel announced that it would
invest $250 million in new technology to gain a factor of 100 in
speed over the next three years, thereby beating Moore's law. This
means that Intel will have to reduce circuit dimensions by a least a
factor of 10, maybe even more. Reducing these dimensions will
take us to the point where finite size begins to affect the properties
of the materials. If we imagine the inside of a conductor, the
electrons tend to move in groups, much like a school of fish in the
ocean. As the size of the conductor is reduced, the schools of
electrons get squeezed, changing their properties. Much like
catfish in a drying-up pond change characteristics to accommodate
for the reduced amount of habitat.

In the case of CheX the helium atoms are like the electrons -- they
tend to school. One of the exciting properties of helium is that we
can vary the size of the school just by changing the temperature.
So, by warming the helium close to a temperature referred to as
the lambda point, we can grow schools of helium atoms so that
they will fill a narrow gap between a pair of plates or wafers.
Because of this, we can study what will happen in very tiny
conductors, just by looking at helium. Theorists have a number of
predictions for what will happen and CHeX is designed to test
some of these theories.

The main component of the CHeX instrument is the
calorimeter. The calorimeter is a cylinder that contains
392 wafers, 50 microns (0.002 inch) thick and each
separated by 50 microns. Between these 50-micron
wafers is where the helium will be confined. The calorimeter is
located inside of the cryostat which is basically a large container
of superfluid helium that is used to keep the calorimeter cool. The
main objective of the CHeX experiment is to study the theory of
the lambda point. The lambda point is the temperature and
pressure where helium transitions from an unordered system to an
ordered system. You can relate this to the point at which water
freezes (transitions from a liquid to a solid). The difference with
helium is that it remains a liquid through the transition but the
molecules all act the same, become ordered.

For more information about CHeX, visit the following web site:
ftp://squid.jpl.nasa.gov/pub/chex/all/homepage/chex.htm

STATUS OF COLUMBIA PROCESSING

Below, we'll provide some details about the postflight work
being done after STS-87 and the subsequent processing of Columbia
as it prepares to fly again as STS-90. These reports will contain
jargon and unfamiliar terms; our intent is not to confuse you, but to
provide a glimpse at all the steps involved. Detailed daily reports
about Columbia's processing can be found at the NASA Shuttle Status
Web site at http://www-pao.ksc.nasa.gov/kscpao/status/status.htm

Since the last updates-sto message, Columbia's engine heat shields
and all three main engines were removed. Technicians completed
work to off load Columbia's residual hypergolic propellants.

The USMP-4 and Spartan payloads were removed from the orbiter's
cargo bay and placed in the payload canister for transfer to the
Vertical Processing Facility. STS-87 secondary payloads have also
been removed from Columbia's midbody.

Functional tests on the forward reaction control system were
completed. Columbia's radiator and payload bay door inspections
were also finished; preparations began to replace one of the payload
bay floodlights.

Removal of the remote manipulator system cameras is complete and
removal of the remote manipulator system itself is in work. Ku band
antenna stowage occurred.

The payload bay doors were closed December 19 in preparation for
the holiday downtime period. Shuttle Columbia was secured in the
OPF with processing scheduled to resume on Jan. 5, following the
holiday down period.

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