[FPSPACE] Latest from CBS News...

Peter Pesavento eagles267@wwainc.com
Tue, 24 Jun 2003 09:38:12 -0400


This is a multi-part message in MIME format.

------=_NextPart_000_0011_01C33A34.545801B0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Because I haven't been able to catch all of my e-mail, here are two =
updates from CBS news...

=20
CBS NEWS STATUS REPORT

a.. 04:55 p.m., 06/20/03, Update: Tile repair options in development; =
tools, material expected to be in place by end of year; RCC repair =
capability may take more time=20
  Shuttle engineers believe the tools and techniques needed for =
spacewalking repair crews to access and patch areas of potentially =
catastrophic damage to an orbiter's heat-shield tiles should be in place =
by the end of the year, sources say, assuming upcoming tests go well.
  Major challenges include development of reliable techniques for =
inspecting a shuttle for damage, gaining access to all possible damage =
sites and perfecting the tools and materials needed to actually patch =
over cracked, eroded or missing tiles. But so far, engineers have not =
identified any show-stoppers, at least for shuttle missions bound for =
the international space station where access is less of an issue.

  But techniques for repairing damage to a shuttle's wing leading edge =
panels pose a much more difficult challenge and likely will take longer =
to develop. A breach in the leading edge of the shuttle Columbia's left =
wing led to the ship's destruction during re-entry Feb. 1, allowing a =
plume of super-heated air to burn its way into the wing's interior.

  NASA has studied in-flight tile repair options in the past and is =
drawing on that background now to develop a workable repair technique =
for future flights. But no previous efforts were undertaken for the =
shuttle's carbon composite nose cap and wing leading edge panels, which =
are made of different material, feature complex curved surfaces and =
experience the most extreme temperatures during re-entry.

  The panels play a critical role in the creation of a so-called =
boundary layer as the shuttle plows through the region of maximum =
heating. The boundary layer provides a natural insulating effect, =
limiting entry temperatures to "just" 3,000 degrees or so. Any repair =
option would have to not just plug a breach but also ensure the smooth =
airflow needed to set up an insulating boundary layer.

  Analysis of a dozen or so possible RCC repair options and materials is =
underway, sources say, but testing is in its early stages and a final =
solution is far from clear.

  Even in the case of tile repair options, engineers have not yet =
settled on what sort of caulk-like patch material is best suited for =
repairing broad areas of tile damage. Issues include the viscosity of =
the material, which astronauts must be able to apply and then spread or =
mold to some degree, and the time needed for any such material to cure, =
or "set up." Engineers currently are testing a silicon-based compound =
similar to one developed in the late 1970s as part of a tile repair =
technique that was never implemented.

  Tests also will be required to ensure any such material can stand-up =
to worst-case re-entry temperatures and conditions.

  The Columbia Accident Investigation Board is expected to recommend =
that NASA develop capabilities for on-orbit repair of tile and =
reinforced carbon carbon (RCC) leading edge panels. The board's final =
report is expected around the end of July. But NASA is not waiting for =
the CAIB report to begin developing a repair capability. A "tiger team" =
under the leadership of space station flight director Paul Hill at the =
Johnson Space Center in Houston has been in place for months.

  But a request for an interview with Hill was turned down by Michael =
Kostelnik, deputy associate administrator for the shuttle and space =
station programs at NASA headquarters, on the grounds that any such =
discussion is "pre-decisional" and that no final decisions have been =
made. The real issue, however, appears to be a general reluctance on =
NASA's part to publicly address any topic the CAIB might discuss in its =
final report or in any interim recommendations that might be released =
between now and then.

  Even so, a broad outline of NASA's on-orbit repair strategy has =
emerged in recent weeks that focuses on four general areas:


    a.. Defining the critical damage size, i.e., the damage threshold =
that would trigger some sort of spacewalk inspection and/or repair =
attempt

    b.. Techniques for inspecting a shuttle for damage

    c.. The materials and tools needed to repair such damage

    d.. The spacewalk access required to implement any such repairs

  For the purposes of this discussion, it is assumed any inspections and =
repairs would be staged at the international space station. Only one =
non-station flight is currently on the books - a mission to service the =
Hubble Space Telescope - and it's not yet clear how inspections or =
repairs could be carried out in the absence of the space station's robot =
arm, multiple EVA anchor points and numerous external cameras. The =
Hubble flight, however, is several launchings down the road and =
engineers will have more time to develop viable "stand alone" repair =
techniques.
  In the near term, shuttle missions to the space station will be =
launched in daylight to give engineers a better chance of spotting =
debris impacts that might damage an orbiter's thermal protection system =
(TPS). In addition, mission managers likely will require external fuel =
tank separation in daylight as well, to improve the odds of spotting any =
areas of foam shedding in orbit. Given those two requirements alone, and =
the orbital mechanics required to rendezvous with the space station, the =
number of possible launch days in a given month will be sharply reduced.

  In any case, sources say, analysis to determine TPS damage criteria - =
what levels of damage would require repair - is not yet complete. But =
NASA hopes to have procedures in place to detect the smallest level of =
damage that could pose a threat to an orbiter and its crew.

  It's not known what powerful spy satellites might be able to detect, =
but approaching shuttles will perform a pirouette of sorts 400 to 600 =
feet below the station to give lab crews a chance to photograph the =
orbiter's underside with telephoto lenses.

  Tests indicate pre- and post-docking photography, by the crew and by =
cameras on the shuttle's robot arm and the station's mobile Canadarm2 =
spacecrane, should provide the coverage needed to spot any significant =
damage. But determining the depth of any tile damage - a critical factor =
- might not be possible without a spacewalk inspection or the =
development of some sort of laser scanner.

  The materials and tools need to carry out a TPS repair in orbit are =
based on an existing "cure-in-place" ablator compound known as MA-25S =
that would be applied by a spacewalking astronaut using a sort of =
high-tech caulk gun. Tests are planned later this summer during flights =
aboard a NASA aircraft that provides brief periods of weightlessness. =
Sources say other tests are planned to determine vacuum cure times and =
temperature limits.

  Different materials and application techniques are being developed for =
RCC damage but details are not yet available.

  The most significant challenge, perhaps, is figuring out how to anchor =
a spacewalker in the weightlessness of orbit to apply the patch material =
and, depending on the situation, smooth it out or shape it without =
causing the station arm-work platform combination to flex too much.

  Just gaining access will be difficult.

  The currently favored scenario, known as option 1, calls for using the =
shuttle's robot arm to lock onto a grapple fixture on the space station =
and then, after docking latches are released, to properly position the =
orbiter. Spacewalkers then would ride the station's robot arm to the =
actual repair site.

  An engineering analysis indicates the shuttle arm is strong enough to =
move the 120-ton space shuttle, but a telescoping boom of some sort may =
be needed to extend the reach of the Canadarm2 to all possible damage =
sites. A similar boom is being considered for use by the shuttle arm =
during non-station missions. Engineers are studying various ways to =
anchor such a boom at the work site to minimize flexing, possibly using =
small fixtures that would be glued to adjacent tiles.

  Engineers initially considered the possibility of astronauts using =
small jetpacks, known as SAFERs, to reach possible damage sites for =
repair work, but that no longer appears feasible. The backpacks could, =
however, be used under certain conditions for initial inspections to =
determine the severity of any damage.


a.. 04:45 p.m., 06/18/03, Update: Engineers assess bi-pod redesign =
options=20
  NASA is considering five options for redesigning the so-called =
"bi-pod" ramp on the shuttle's external fuel tank, the area where a =
chunk of foam insulation broke away during Columbia's launch, hit the =
left wing and possibly caused a catastrophic breach. The currently =
favored option calls for eliminating the use of foam in the area in =
favor of an exposed fitting equipped with heaters to prevent pre-launch =
ice buildups.
  Senior NASA and contractor managers and engineers met Tuesday and =
today in Michoud, La., where Lockheed Martin Space Systems Co. builds =
the external tanks, to review the bi-pod redesign options in preparation =
for making a final selection in the next few weeks. While most observers =
believe NASA will not be able to resume shuttle flights until well into =
2004 at the earliest, senior agency managers say they believe launchings =
could resume as early as mid-to-late December. In any case, engineers =
plan to have the bi-pod fix in place as soon as possible, eliminating =
what many believe was the initiating event in the Columbia disaster.

  "Clearly, there's been a lot of focus on the foam, the bi-pod foam in =
particular, and our redesign efforts have been ongoing in that =
particular activity for a couple of months already," Michael Kostelnik, =
NASA's deputy associate administrator for shuttle and space station, =
told reporters today. "We will solve the shedding problem of foam in =
that particular area and our technical plan for that allows us a return =
to flight window in December."

  The external fuel tank forms the structural backbone of the shuttle =
"stack" for the climb to space. Solid-fuel boosters are attached on each =
side with massive explosive bolts while the shuttle is attached by =
fittings under its nose and engine compartment. The aft end of the =
shuttle is attached with massive fittings where 17-inch propellant lines =
from the external tank feed into the ship's aft engine compartment. The =
nose is attached by a so-called bi-pod, two cylindrical struts that meet =
at a single attachment plate just behind the nose landing gear doors. =
The struts attach to a pair of fittings on the external tank, forming a =
triangular bi-pod assembly.

  At launch, the tank is loaded with a half-million gallons of supercold =
liquid oxygen and liquid hydrogen rocket fuel. From the beginning, the =
bi-pod strut attachment fittings have been buried in hand-sprayed foam =
insulation to prevent ice from forming around the aluminum fittings. Any =
such ice likely would break away when subjected to the vibration of =
launch, posing an impact hazard to the underside of the shuttle. The =
foam covering the bi-pod fittings is hand carved to form an =
aerodynamically benign ramp allowing the smooth flow of air over the =
protrusions.

  As it turns out, the bi-pod ramp prevented ice buildups but created =
another impact hazard: The foam itself.

  A suitcase-size chunk of foam from Columbia's left bi-pod ramp area =
pulled free during launch Jan. 16 and struck the left wing's leading =
edge at some 500 mph. The foam strike presumably caused the breach that =
led to the ship's destruction during re-entry Feb. 1. Another large =
piece of foam broke away from the same area during an October shuttle =
flight and hit a booster. All told, investigators have identified at =
least six missions, and possibly seven, in which large pieces of foam =
debris fell off the bi-pod ramps of the external tanks.

  It is not yet clear what causes the foam to break away. Many engineers =
believe some form of "cryopumping" may be involved, in which trapped air =
in the foam liquifies after the tank is chilled during fueling. In this =
scenario, heating during ascent causes the trapped liquid to warm and =
expand, weakening the foam in that area. But recent tests by the =
Columbia Accident Investigation Board indicate cryopumping alone is not =
the answer and that some combination of factors may be responsible.

  In any case, there is little doubt the CAIB's final report, expected =
in late July, will include a recommendation to redesign the bi-pod =
attachment system to preclude foam shedding in the future. In the =
meantime, NASA is pressing ahead with work to do just that.

  Of the five options currently on the table, the favored solution, =
known as option 2a, is one in which the aerodynamically shaped foam ramp =
is eliminated entirely in favor of an exposed fitting equipped with one =
or more heaters to eliminate the possibility of pre-launch ice buildups. =
Aluminum end covers and caps would be replaced with tougher Inconel =
covers. Other changes include the addition of wiring for the heaters and =
additional electrical power from ground-support equipment prior to =
liftoff.

  Other options include:


    a.. Option 1: Reduced volume ramp with a minimum 50 percent =
reduction in the amount of foam required; aluminum end covers replaced =
by super lightweight ablator material; new heater elements and wiring.

    b.. Option 2: Partially exposed fitting with an 80 percent reduction =
in foam ramp volume; Inconel end covers and caps; new heater and wiring.

    c.. Option 3: Inconel fairing over the entire bi-pod fitting, =
eliminating need for a foam ramp. Strip heaters would be attached to the =
interior of the welded fairing. This option was an early favorite.

    d.. Option 3A: Small Inconel fairing, equipped with strip heaters, =
that covers the central shaft of the bi-pod fitting. No ramp foam is =
required.

  Agency managers, with input from the Columbia Accident Investigation =
Board, hope to settle on a redesign option in the next few weeks.
------=_NextPart_000_0011_01C33A34.545801B0
Content-Type: text/html;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1170" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Because I haven't been able to catch =
all of my=20
e-mail, here are two updates from CBS news...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><!--StartFragment -->&nbsp;
<H4>
<CENTER><A name=3D"CBS NEWS STATUS REPORT">CBS NEWS STATUS=20
REPORT</A></CENTER></H4>
<P></P>
<LI><B>04:55 p.m., 06/20/03, Update: Tile repair options in development; =
tools,=20
material expected to be in place by end of year; RCC repair capability =
may take=20
more time</B>=20
<BLOCKQUOTE>Shuttle engineers believe the tools and techniques needed =
for=20
  spacewalking repair crews to access and patch areas of potentially=20
  catastrophic damage to an orbiter's heat-shield tiles should be in =
place by=20
  the end of the year, sources say, assuming upcoming tests go well.
  <P>Major challenges include development of reliable techniques for =
inspecting=20
  a shuttle for damage, gaining access to all possible damage sites and=20
  perfecting the tools and materials needed to actually patch over =
cracked,=20
  eroded or missing tiles. But so far, engineers have not identified any =

  show-stoppers, at least for shuttle missions bound for the =
international space=20
  station where access is less of an issue.</P>
  <P>But techniques for repairing damage to a shuttle's wing leading =
edge panels=20
  pose a much more difficult challenge and likely will take longer to =
develop. A=20
  breach in the leading edge of the shuttle Columbia's left wing led to =
the=20
  ship's destruction during re-entry Feb. 1, allowing a plume of =
super-heated=20
  air to burn its way into the wing's interior.</P>
  <P>NASA has studied in-flight tile repair options in the past and is =
drawing=20
  on that background now to develop a workable repair technique for =
future=20
  flights. But no previous efforts were undertaken for the shuttle's =
carbon=20
  composite nose cap and wing leading edge panels, which are made of =
different=20
  material, feature complex curved surfaces and experience the most =
extreme=20
  temperatures during re-entry.</P>
  <P>The panels play a critical role in the creation of a so-called =
boundary=20
  layer as the shuttle plows through the region of maximum heating. The =
boundary=20
  layer provides a natural insulating effect, limiting entry =
temperatures to=20
  "just" 3,000 degrees or so. Any repair option would have to not just =
plug a=20
  breach but also ensure the smooth airflow needed to set up an =
insulating=20
  boundary layer.</P>
  <P>Analysis of a dozen or so possible RCC repair options and materials =
is=20
  underway, sources say, but testing is in its early stages and a final =
solution=20
  is far from clear.</P>
  <P>Even in the case of tile repair options, engineers have not yet =
settled on=20
  what sort of caulk-like patch material is best suited for repairing =
broad=20
  areas of tile damage. Issues include the viscosity of the material, =
which=20
  astronauts must be able to apply and then spread or mold to some =
degree, and=20
  the time needed for any such material to cure, or "set up." Engineers=20
  currently are testing a silicon-based compound similar to one =
developed in the=20
  late 1970s as part of a tile repair technique that was never =
implemented.</P>
  <P>Tests also will be required to ensure any such material can =
stand-up to=20
  worst-case re-entry temperatures and conditions.</P>
  <P>The Columbia Accident Investigation Board is expected to recommend =
that=20
  NASA develop capabilities for on-orbit repair of tile and reinforced =
carbon=20
  carbon (RCC) leading edge panels. The board's final report is expected =
around=20
  the end of July. But NASA is not waiting for the CAIB report to begin=20
  developing a repair capability. A "tiger team" under the leadership of =
space=20
  station flight director Paul Hill at the Johnson Space Center in =
Houston has=20
  been in place for months.</P>
  <P>But a request for an interview with Hill was turned down by Michael =

  Kostelnik, deputy associate administrator for the shuttle and space =
station=20
  programs at NASA headquarters, on the grounds that any such discussion =
is=20
  "pre-decisional" and that no final decisions have been made. The real =
issue,=20
  however, appears to be a general reluctance on NASA's part to publicly =
address=20
  any topic the CAIB might discuss in its final report or in any interim =

  recommendations that might be released between now and then.</P>
  <P>Even so, a broad outline of NASA's on-orbit repair strategy has =
emerged in=20
  recent weeks that focuses on four general areas:</P>
  <P></P>
  <UL>
    <LI>Defining the critical damage size, i.e., the damage threshold =
that would=20
    trigger some sort of spacewalk inspection and/or repair =
attempt<BR></LI>
    <LI>Techniques for inspecting a shuttle for damage<BR></LI>
    <LI>The materials and tools needed to repair such damage<BR></LI>
    <LI>The spacewalk access required to implement any such=20
  repairs<BR></LI></UL>For the purposes of this discussion, it is =
assumed any=20
  inspections and repairs would be staged at the international space =
station.=20
  Only one non-station flight is currently on the books - a mission to =
service=20
  the Hubble Space Telescope - and it's not yet clear how inspections or =
repairs=20
  could be carried out in the absence of the space station's robot arm, =
multiple=20
  EVA anchor points and numerous external cameras. The Hubble flight, =
however,=20
  is several launchings down the road and engineers will have more time =
to=20
  develop viable "stand alone" repair techniques.
  <P>In the near term, shuttle missions to the space station will be =
launched in=20
  daylight to give engineers a better chance of spotting debris impacts =
that=20
  might damage an orbiter's thermal protection system (TPS). In =
addition,=20
  mission managers likely will require external fuel tank separation in =
daylight=20
  as well, to improve the odds of spotting any areas of foam shedding in =
orbit.=20
  Given those two requirements alone, and the orbital mechanics required =
to=20
  rendezvous with the space station, the number of possible launch days =
in a=20
  given month will be sharply reduced.</P>
  <P>In any case, sources say, analysis to determine TPS damage criteria =
- what=20
  levels of damage would require repair - is not yet complete. But NASA =
hopes to=20
  have procedures in place to detect the smallest level of damage that =
could=20
  pose a threat to an orbiter and its crew.</P>
  <P>It's not known what powerful spy satellites might be able to =
detect, but=20
  approaching shuttles will perform a pirouette of sorts 400 to 600 feet =
below=20
  the station to give lab crews a chance to photograph the orbiter's =
underside=20
  with telephoto lenses.</P>
  <P>Tests indicate pre- and post-docking photography, by the crew and =
by=20
  cameras on the shuttle's robot arm and the station's mobile Canadarm2=20
  spacecrane, should provide the coverage needed to spot any significant =
damage.=20
  But determining the depth of any tile damage - a critical factor - =
might not=20
  be possible without a spacewalk inspection or the development of some =
sort of=20
  laser scanner.</P>
  <P>The materials and tools need to carry out a TPS repair in orbit are =
based=20
  on an existing "cure-in-place" ablator compound known as MA-25S that =
would be=20
  applied by a spacewalking astronaut using a sort of high-tech caulk =
gun. Tests=20
  are planned later this summer during flights aboard a NASA aircraft =
that=20
  provides brief periods of weightlessness. Sources say other tests are =
planned=20
  to determine vacuum cure times and temperature limits.</P>
  <P>Different materials and application techniques are being developed =
for RCC=20
  damage but details are not yet available.</P>
  <P>The most significant challenge, perhaps, is figuring out how to =
anchor a=20
  spacewalker in the weightlessness of orbit to apply the patch material =
and,=20
  depending on the situation, smooth it out or shape it without causing =
the=20
  station arm-work platform combination to flex too much.</P>
  <P>Just gaining access will be difficult.</P>
  <P>The currently favored scenario, known as option 1, calls for using =
the=20
  shuttle's robot arm to lock onto a grapple fixture on the space =
station and=20
  then, after docking latches are released, to properly position the =
orbiter.=20
  Spacewalkers then would ride the station's robot arm to the actual =
repair=20
  site.</P>
  <P>An engineering analysis indicates the shuttle arm is strong enough =
to move=20
  the 120-ton space shuttle, but a telescoping boom of some sort may be =
needed=20
  to extend the reach of the Canadarm2 to all possible damage sites. A =
similar=20
  boom is being considered for use by the shuttle arm during non-station =

  missions. Engineers are studying various ways to anchor such a boom at =
the=20
  work site to minimize flexing, possibly using small fixtures that =
would be=20
  glued to adjacent tiles.</P>
  <P>Engineers initially considered the possibility of astronauts using =
small=20
  jetpacks, known as SAFERs, to reach possible damage sites for repair =
work, but=20
  that no longer appears feasible. The backpacks could, however, be used =
under=20
  certain conditions for initial inspections to determine the severity =
of any=20
  damage.</P>
  <P></P></BLOCKQUOTE></LI>
<LI><B>04:45 p.m., 06/18/03, Update: Engineers assess bi-pod redesign=20
options</B>=20
<BLOCKQUOTE>NASA is considering five options for redesigning the =
so-called=20
  "bi-pod" ramp on the shuttle's external fuel tank, the area where a =
chunk of=20
  foam insulation broke away during Columbia's launch, hit the left wing =
and=20
  possibly caused a catastrophic breach. The currently favored option =
calls for=20
  eliminating the use of foam in the area in favor of an exposed fitting =

  equipped with heaters to prevent pre-launch ice buildups.
  <P>Senior NASA and contractor managers and engineers met Tuesday and =
today in=20
  Michoud, La., where Lockheed Martin Space Systems Co. builds the =
external=20
  tanks, to review the bi-pod redesign options in preparation for making =
a final=20
  selection in the next few weeks. While most observers believe NASA =
will not be=20
  able to resume shuttle flights until well into 2004 at the earliest, =
senior=20
  agency managers say they believe launchings could resume as early as=20
  mid-to-late December. In any case, engineers plan to have the bi-pod =
fix in=20
  place as soon as possible, eliminating what many believe was the =
initiating=20
  event in the Columbia disaster.</P>
  <P>"Clearly, there's been a lot of focus on the foam, the bi-pod foam =
in=20
  particular, and our redesign efforts have been ongoing in that =
particular=20
  activity for a couple of months already," Michael Kostelnik, NASA's =
deputy=20
  associate administrator for shuttle and space station, told reporters =
today.=20
  "We will solve the shedding problem of foam in that particular area =
and our=20
  technical plan for that allows us a return to flight window in =
December."</P>
  <P>The external fuel tank forms the structural backbone of the shuttle =
"stack"=20
  for the climb to space. Solid-fuel boosters are attached on each side =
with=20
  massive explosive bolts while the shuttle is attached by fittings =
under its=20
  nose and engine compartment. The aft end of the shuttle is attached =
with=20
  massive fittings where 17-inch propellant lines from the external tank =
feed=20
  into the ship's aft engine compartment. The nose is attached by a =
so-called=20
  bi-pod, two cylindrical struts that meet at a single attachment plate =
just=20
  behind the nose landing gear doors. The struts attach to a pair of =
fittings on=20
  the external tank, forming a triangular bi-pod assembly.</P>
  <P>At launch, the tank is loaded with a half-million gallons of =
supercold=20
  liquid oxygen and liquid hydrogen rocket fuel. From the beginning, the =
bi-pod=20
  strut attachment fittings have been buried in hand-sprayed foam =
insulation to=20
  prevent ice from forming around the aluminum fittings. Any such ice =
likely=20
  would break away when subjected to the vibration of launch, posing an =
impact=20
  hazard to the underside of the shuttle. The foam covering the bi-pod =
fittings=20
  is hand carved to form an aerodynamically benign ramp allowing the =
smooth flow=20
  of air over the protrusions.</P>
  <P>As it turns out, the bi-pod ramp prevented ice buildups but created =
another=20
  impact hazard: The foam itself.</P>
  <P>A suitcase-size chunk of foam from Columbia's left bi-pod ramp area =
pulled=20
  free during launch Jan. 16 and struck the left wing's leading edge at =
some 500=20
  mph. The foam strike presumably caused the breach that led to the =
ship's=20
  destruction during re-entry Feb. 1. Another large piece of foam broke =
away=20
  from the same area during an October shuttle flight and hit a booster. =
All=20
  told, investigators have identified at least six missions, and =
possibly seven,=20
  in which large pieces of foam debris fell off the bi-pod ramps of the =
external=20
  tanks.</P>
  <P>It is not yet clear what causes the foam to break away. Many =
engineers=20
  believe some form of "cryopumping" may be involved, in which trapped =
air in=20
  the foam liquifies after the tank is chilled during fueling. In this =
scenario,=20
  heating during ascent causes the trapped liquid to warm and expand, =
weakening=20
  the foam in that area. But recent tests by the Columbia Accident =
Investigation=20
  Board indicate cryopumping alone is not the answer and that some =
combination=20
  of factors may be responsible.</P>
  <P>In any case, there is little doubt the CAIB's final report, =
expected in=20
  late July, will include a recommendation to redesign the bi-pod =
attachment=20
  system to preclude foam shedding in the future. In the meantime, NASA =
is=20
  pressing ahead with work to do just that.</P>
  <P>Of the five options currently on the table, the favored solution, =
known as=20
  option 2a, is one in which the aerodynamically shaped foam ramp is =
eliminated=20
  entirely in favor of an exposed fitting equipped with one or more =
heaters to=20
  eliminate the possibility of pre-launch ice buildups. Aluminum end =
covers and=20
  caps would be replaced with tougher Inconel covers. Other changes =
include the=20
  addition of wiring for the heaters and additional electrical power =
from=20
  ground-support equipment prior to liftoff.</P>
  <P>Other options include:</P>
  <P></P>
  <UL>
    <LI>Option 1: Reduced volume ramp with a minimum 50 percent =
reduction in the=20
    amount of foam required; aluminum end covers replaced by super =
lightweight=20
    ablator material; new heater elements and wiring.
    <P></P></LI>
    <LI>Option 2: Partially exposed fitting with an 80 percent reduction =
in foam=20
    ramp volume; Inconel end covers and caps; new heater and wiring.
    <P></P></LI>
    <LI>Option 3: Inconel fairing over the entire bi-pod fitting, =
eliminating=20
    need for a foam ramp. Strip heaters would be attached to the =
interior of the=20
    welded fairing. This option was an early favorite.
    <P></P></LI>
    <LI>Option 3A: Small Inconel fairing, equipped with strip heaters, =
that=20
    covers the central shaft of the bi-pod fitting. No ramp foam is =
required.
    <P></P></LI></UL>Agency managers, with input from the Columbia =
Accident=20
  Investigation Board, hope to settle on a redesign option in the next =
few=20
weeks.</BLOCKQUOTE></LI></DIV></BODY></HTML>

------=_NextPart_000_0011_01C33A34.545801B0--