Foam Cracks May Delay Shuttle Launch

Foam Cracks May Delay Shuttle Launch
Program Manager Says Problem May Pose 'Unacceptable Safety Threat'

By Guy Gugliotta
Washington Post Staff Writer
Friday, December 2, 2005; A03

Recently discovered cracks in a foam "ramp" on the space shuttle's
external fuel tank may present an "unacceptable safety threat" to the
orbiter, raising the possibility that NASA could delay its next launch
while engineers decide whether to get rid of the ramp altogether,
shuttle program manager N. Wayne Hale said in an internal memo.

Discovery of the PAL ramp cracks during an inspection early last month
marked a new setback for the troubled shuttle program, which has flown
only once since Columbia disintegrated over Texas in February 2003.
Hale had predicted earlier that making changes to eliminate the ramp
would delay the next shuttle launch until next fall, at least four
months later than currently planned.

Further delays could also add cost and uncertainty to President Bush's
"Vision for Space Exploration," which calls for the shuttle to finish
building the international space station by 2010 and then retire,
stepping aside for a new-generation spaceship designed to take humans
back to the moon and eventually to Mars.

In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load," or
PAL, ramp extended deep into the foam insulation and appear to have
been caused by contraction and expansion as the tank was being filled
with supercooled liquid hydrogen and oxygen.

Because all shuttle fuel tanks undergo such "cryoloading," cracking
"must be presumed possible in any PAL ramp on any flight vehicle,"
Hale wrote. As a result "this . . . represents a critical and
unacceptable safety threat to the flight of the space shuttle."

Hale stressed his judgments were "preliminary" but it "appears
mandatory" that the shuttle team focus on eliminating the ramp
altogether for all upcoming shuttle flights, including the May launch.

Despite the dire nature of the e-mail, however, Hale said in a
telephone interview yesterday that he intended to challenge his team
to "explain to me how we could do anything with the cracks," including
devising new foam spraying techniques.

"We don't give direction by e-mail," Hale said. "We will have a formal
board meeting to review this." The e-mail, he added, "is not a
decision, but a notice to my folks that tells them 'this is the way
I'm thinking; this is the way I'm leaning. Talk me into it, or talk me
out of it.' "

NASA grounded the shuttle last July after Discovery's external tank
lost a one-pound piece of PAL ramp foam during launch. The fragment
flew harmlessly away, but the mishap was embarrassing, because NASA
had redesigned the external tank after a piece of foam punched a fatal
hole in Columbia's heat shielding.

The foam, sprayed both mechanically and by hand, insulates the
154-foot tank to protect it when it is filled with liquid oxygen and
hydrogen cooled to temperatures several hundred degrees below zero.

The PAL ramps are foam ridges that run alongside electric cables and
pressurized gas lines on the exterior of the tank. They serve as a
windbreak for these fixtures during the turbulence of launch.

As recently as mid-October, engineers attributed the Discovery foam
loss to other factors, including "crushing" by technicians crawling on
top of the tank during manufacture and a possible air-filled "void"
inside the foam that had expanded and burst as Discovery climbed.

The planned fix was to improve manual foam applications and develop
new automated techniques. Hale at that time described elimination of
the PAL ramp as an option.

But when they examined a tank that had been twice loaded with fuel and
then emptied, engineers found nine vertical cracks in the lower,
hydrogen, PAL ramp. Another tank that had not been cryoloaded had no
such cracks.

NASA sources, who requested anonymity because they were not authorized
to speak publicly about the investigation, said engineers who knew
about the cracks immediately suspected they could indicate a serious
problem.

But when Hale announced the findings at a Nov. 22 news conference, he
said the next "one or two flights" would use the new, improved PAL
ramp, while NASA tested the feasibility of flying without it. He said
the testing would not finish before next fall.

In his e-mail five days later, however, Hale's tone was markedly more
pessimistic. He said yesterday that he had seen a further report from
his team showing that at least one of the cracks extended all the way
down through the ramp and into the "acreage foam," the initial
machine-applied insulation layer to which the ramp is attached.

"Further, cracks appeared in both old and new sprayed areas of the . .
.. PAL ramp, and therefore the new improved spray techniques do not
provide protection from this phenomenon," Hale wrote in the e-mail.
"It is hard to see how automated PAL ramp spray would provide any
protection from these cracks."

Because of the potential pervasiveness of the cracking, "all efforts
should be made to provide a no-PAL ramp flight condition," Hale said,
including wind tunnel testing and computer models capable of analyzing
the effects of eliminating the ramps.

Hale said yesterday, however, that he had directed his team to move
ahead in investigating new spray techniques along with ramp removal,
and that the May launch date "remains on the table" while planners
study the options in preparation for a formal progress review in the
next few weeks.

wrote:
Foam Cracks May Delay Shuttle Launch
Program Manager Says Problem May Pose 'Unacceptable Safety Threat'

By Guy Gugliotta
Washington Post Staff Writer
Friday, December 2, 2005; A03

Recently discovered cracks in a foam "ramp" on the space shuttle's
external fuel tank may present an "unacceptable safety threat" to the
orbiter, raising the possibility that NASA could delay its next launch
while engineers decide whether to get rid of the ramp altogether,
shuttle program manager N. Wayne Hale said in an internal memo.
...
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load," or
PAL, ramp extended deep into the foam insulation and appear to have
been caused by contraction and expansion as the tank was being filled
with supercooled liquid hydrogen and oxygen.

Because all shuttle fuel tanks undergo such "cryoloading," cracking
"must be presumed possible in any PAL ramp on any flight vehicle,"
Hale wrote. As a result "this . . . represents a critical and
unacceptable safety threat to the flight of the space shuttle."

Hale stressed his judgments were "preliminary" but it "appears
mandatory" that the shuttle team focus on eliminating the ramp
altogether for all upcoming shuttle flights, including the May launch.
...
As recently as mid-October, engineers attributed the Discovery foam
loss to other factors, including "crushing" by technicians crawling on
top of the tank during manufacture and a possible air-filled "void"
inside the foam that had expanded and burst as Discovery climbed.

Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

- Ed Kyle
www.geocities.com/launchreport

ed kyle wrote:
wrote:

Foam Cracks May Delay Shuttle Launch
Program Manager Says Problem May Pose 'Unacceptable Safety Threat'

By Guy Gugliotta
Washington Post Staff Writer
Friday, December 2, 2005; A03

Recently discovered cracks in a foam "ramp" on the space shuttle's
external fuel tank may present an "unacceptable safety threat" to the
orbiter, raising the possibility that NASA could delay its next launch
while engineers decide whether to get rid of the ramp altogether,
shuttle program manager N. Wayne Hale said in an internal memo.
...
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load," or
PAL, ramp extended deep into the foam insulation and appear to have
been caused by contraction and expansion as the tank was being filled
with supercooled liquid hydrogen and oxygen.

Because all shuttle fuel tanks undergo such "cryoloading," cracking
"must be presumed possible in any PAL ramp on any flight vehicle,"
Hale wrote. As a result "this . . . represents a critical and
unacceptable safety threat to the flight of the space shuttle."

Hale stressed his judgments were "preliminary" but it "appears
mandatory" that the shuttle team focus on eliminating the ramp
altogether for all upcoming shuttle flights, including the May launch.
...
As recently as mid-October, engineers attributed the Discovery foam
loss to other factors, including "crushing" by technicians crawling on
top of the tank during manufacture and a possible air-filled "void"
inside the foam that had expanded and burst as Discovery climbed.


Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

- Ed Kyle
www.geocities.com/launchreport

Maybe. Al-Li is very similar to the Al alloys used previously in
Coefficient of expansion (cte) so that is not different. However the
tank was redesigned in several areas to take advantage (lighter weight)
of the structural properties of Al-Li and new manufacturing techniques.
The loading of the tank coupled with the new design could change the
stresses in the tank skin in those areas.

A new loading procedure could also have the same effect as well as a new
detanking procedure.

I would guess that cracking problem goes back to the foam properties and
the 'new'(not so new anymore) blowing agents. I would want to know how
old the tank is and what is history of exposure to the elements. Could
UV and age have an effect? Dunno.

I have heard stories that at the first LH2 loading huge chunks of foam
fell off the aft dome of the LH2 tank. Making the foam work has been a
major effort from day 1. Without the foam, the shuttle can't fly.

"ed kyle" wrote in message
oups.com...
wrote:
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load," or
PAL, ramp extended deep into the foam insulation and appear to have
been caused by contraction and expansion as the tank was being filled
with supercooled liquid hydrogen and oxygen.

Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

I seriously doubt it.

Jeff
--
Remove icky phrase from email address to get a valid address.

I would guess that cracking problem goes back to the foam properties and
the 'new'(not so new anymore) blowing agents. I would want to know how old
the tank is and what is history of exposure to the elements. Could UV and
age have an effect? Dunno.

I think you're on the right track here. The more delays there are in the
program, the worse the problem seems to become. A lot of people here have
been saying this is partly an aging issue with the foam for a long time. If
that does turn out to be the case, it's going to look like NASA has been
chasing it's tail. Something like foam aging can be easily identified
through ground tests. Therefore, it's likely there are many aspects to the
problem, not just the foam itself.

Jeff Findley wrote:
"ed kyle" wrote in message
oups.com...
wrote:
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load," or
PAL, ramp extended deep into the foam insulation and appear to have
been caused by contraction and expansion as the tank was being filled
with supercooled liquid hydrogen and oxygen.

Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

I seriously doubt it.

Jeff

I remain to be convinced one way or the other, but I
did find the following unsettling tidbit. NASA replaced
the original 2219 Aluminum alloy with 2195 Aluminum-
Lithium beginning with STS-98.

"http://www.ingentaconnect.com/content/asm/jmep/1998/00000007/00000005/art00015"

- Ed Kyle

"ed kyle" wrote in
ups.com:


Jeff Findley wrote:
"ed kyle" wrote in message
oups.com...
wrote:
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load,"
or PAL, ramp extended deep into the foam insulation and appear to
have been caused by contraction and expansion as the tank was
being filled with supercooled liquid hydrogen and oxygen.

Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

I seriously doubt it.

Jeff

I remain to be convinced one way or the other, but I
did find the following unsettling tidbit. NASA replaced
the original 2219 Aluminum alloy with 2195 Aluminum-
Lithium beginning with STS-98.

Nope, STS-91. See Jenkins, 3rd ed, p. 424.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Should be easy enough to track tile damage vs type of tank

Jorge R. Frank wrote:
"ed kyle" wrote in
ups.com:


Jeff Findley wrote:
"ed kyle" wrote in message
oups.com...
wrote:
In the e-mail Sunday to shuttle engineers and managers, Hale said
vertical cracks in the external tank's "protuberance air load,"
or PAL, ramp extended deep into the foam insulation and appear to
have been caused by contraction and expansion as the tank was
being filled with supercooled liquid hydrogen and oxygen.

Could this have something to do with the use of Aluminum-Lithium
tanks? Aluminum-Lithium tanks began flying just a few years ago,
replacing the previous all-Aluminum.

I seriously doubt it.

Jeff

I remain to be convinced one way or the other, but I
did find the following unsettling tidbit. NASA replaced
the original 2219 Aluminum alloy with 2195 Aluminum-
Lithium beginning with STS-98.

Nope, STS-91. See Jenkins, 3rd ed, p. 424.

Right. Thanks. I was thinking of 1998, which is when
STS-91 flew.

- Ed Kyle

Bob Haller wrote:
Should be easy enough to track tile damage vs type of tank

Uhhh! Every single mission has had tile damage. Some much worse than
others ( my experience from 15 years ago to 6 years ago ) . It would
seem sensible to track damage vs foam type (blowing agents) and
age/exposure of the ET.

Is it a material problem or a process problem?