CAPE CANAVERAL, Fla
CAPE CANAVERAL, Fla. -- Shuttle engineers plan to repeat from scratch their analysis of the damage a piece of falling debris from Columbia's external tank might make on the orbiter's heat protection tiles, program chief Ron Dittemore said Monday.
Captured on film some 80 seconds after the Jan. 16 launch of Columbia, a small chunk of insulating foam could be seen breaking loose of the orange tank and hitting the orbiters left wing. This has become the center of attention for the investigation into what happened in the skies high over Texas on Saturday.
Initial studies of the incident during the days following liftoff came to the conclusion that Columbia and its crew were in no grave danger, a fact that was shared with the seven astronauts during the flight.
"The conclusion was that the debris that impacted the vehicle did not represent a threat to the safety of the crew or the vehicle," Dittemore said.
NASA managers have admitted as early as the first press briefing on Saturday that they could have been wrong, and since the link between the falling debris and damage to heat protection tiles followed by loss of vehicle and crew is so great, they want to take another look.
"Although that may, in fact, wind up being the cause -- it may certainly be the leading candidate right now -- we have to go through all the evidence and then rule things out very methodically in order to arrive at the cause," William Readdy, NASA's top spaceflight manager, said Monday.
But first the NASA space community at Johnson Space Center in Houston will take Tuesday off to celebrate the lives of Rick Husband, Willie McCool, Kalpana Chawla, Laurel Clark, Mike Anderson, David Brown and Israel's Ilan Ramon -- and to mourn their loss.
"We're going to pause and reflect upon the crew of Columbia, their lives, their contributions, their memory and although we can not stop our investigation and the recovery effort, we will pause in this location to take the time to reflect upon their lives and their sacrifice," Dittemore said.
The private ceremony is scheduled to begin at 1 p.m. EST (1800 GMT) Tuesday and will be attended by NASA Administrator Sean O'Keefe, dignitaries from Israel, family members of the crew lost in the 1986 Challenger disaster and many others who work at the space center.
President and Mrs. Bush are scheduled to participate. President George Bush senior and his wife Barabara visited JSC on Monday and also took time to speak with the Expedition Six crew aboard the International Space Station.
Another memorial service is planned in Washington, D.C. at the National Cathedral on Thursday, and here at the Cape officials are putting together plans for a service at the Shuttle Landing Facility Friday morning at the hour Columbia was due at the runway.
New data
Dittemore added new information about the timeline of events the led to Columbia's loss on Saturday.
- At 8:52 a.m. EST (1352 GMT), one minute earlier than the start of events previously discussed, three sensors in the left-hand wheel well -- where the main landing gear is stowed during the mission -- detected a rise in temperature.
"This was the first event, the first occurrence of a significant thermal event in the wheel well on the left-hand side," Dittemore said.
- At 8:53 a.m. EST (1353 GMT), two wheel well sensors previously mentioned as detecting a rise in temperature of 20 to 30 degrees Fahrenheit in five minutes are now believed to have seen a rise of 30 to 40 degrees.
- At 8:55 a.m. EST (1355 GMT), a fifth sensor in the landing gear area showed an unusual temperature rise.
- At 8:57 a.m. EST (1357 GMT), two sensors on the left wings upper and lower skin failed.
- At 8:59 a.m. EST (1359 GMT), in addition to the left wing's flap moving to help steer the shuttle back on course due to increasing drag from the left wing's surface, Columbia's nose steering jets automatically fired for 1.5 seconds to help with the correction.
"The aero surfaces were doing what they needed to do to counteract the drag on the left side of the vehicle. The right yaw jets had to kick in to help the aero surfaces and it appears that we were losing ground as far as the rate of attitude excursion. It was not long after that point that we lost all data and communication with the crew," Dittemore said.
He also mentioned that an additional 32 seconds of computer data that may be available is taking more time to retrieve and process than first thought. It will likely require specialists making a trip to White Sands, N.M. to the communications ground station there to get at the originally-recorded data and make sense of it.
Debris details
Dittemore reviewed the process by which NASA engineers and managers examined the debris falling from the external tank and determined it would not be a mission-threatening deal.
First, the timeline: Launch was on Jan. 16, the first film reviews were on Jan. 17 and the first engineering meetings were on Jan. 20. Initial results were reported on Jan. 21, final engineering reviews took place Jan. 23 and 24, and reports to the senior Mission Management Team were made on Jan. 24 and 27.
"Both those times reporting to the Mission Management Team the conclusion was that the debris that impacted the vehicle did not represent a threat to the safety of the crew or the vehicle," Dittemore said.
Second, the assumptions the analysis was based on: The size of the debris was 20 inches by 16 inches by 6 inches, and the weight was 2.67 pounds. The size was based on examining the launch films and previous experience with foam detaching from the tank.
Using a computer model developed through the years for this very purpose, engineers studied how the tiles might be damaged depending upon the angle the debris hit -- estimated to be between 10 and 16 degrees -- and with varying weights of debris.
After crunching the numbers, the worst case scenario was that either one tile near the left-hand landing gear door would be completely broken free of the orbiter, or several tiles would be grazed, their top layers shaved off in an area roughly 32 inches long and seven inches wide.
It has generally been believed in the past that any significant damage to the black heat protection tiles on the belly of the shuttle could, at the very least, cause some melting of the structure immediately underneath -- if not the complete loss of vehicle and crew.
Dittemore said that was not the conclusion they reached.
"Even though you might have localized structural damage, you would not have damage sufficient to cause a catastrophic event, nor impact the flying qualities of the vehicle," he said.
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