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Aviation Week & Space Technology
Structural, Systems Integrity Focus Of Shuttle Probe
By William Scott
Investigators probing the loss of space shuttle Columbia on Feb. 1 at about 9 a. m. EST during reentry will probably focus on structural- and systems-integrity.
Data sent via telemetry from the orbiter are being scrutinized for clues that could explain the vehicle's high-altitude break-up.
"We'll be poring over that data 24 hours a day for the foreseeable future," said Ron Dittemore, NASA's space shuttle program manager.
Although details are still slowly emerging from NASA, it appears that both voice and telemetry signals were lost shortly after Columbia emerged from the "blackout" portion of the reentry. Milt Heflin, NASA's Chief Flight Director, said "all vehicle data" were lost when Columbia was at 207,135 ft. altitude and Mach 18. 3.
At a mid-afternoon press briefing, Heflin outlined a sequence of sensor readings and the loss of those readings:
- 8:53 a. m. EST - Lost left wing inboard and outboard hydraulic temperature sensors.
- 8:56 a. m. EST - Left main tire and brake line temperatures increasing.
- 8:58 a. m. EST - "Bondline" temperatures from sensors in the vehicle structure were lost. Three of these were on the left wing's inboard and outboard elevons.
- 8:59 a. m. EST - Left main gear tire temperatures and pressures were lost; these involved eight separate sensor measurements. At about this time, a tire pressure alert was displayed to the shuttle crew, and was apparently acknowledged verbally. This was believed to be the crew's last transmission.
U. S. officials identified several primary areas for investigators' initial focus:
- The trajectory flown by the shuttle as it entered the upper atmosphere. A too-steep approach could cause excessive heating of the vehicle's structure, which could lead to its failure.
- Integrity of the orbiter's structure throughout the reentry.
- The flight controls, including both the reaction control system (RCS) small thrusters that let astronauts fly the orbiter in space -- and aerodynamic surfaces, such as elevons on the aft edge of the wing, which control the vehicle within the atmosphere.
- Possible damage to the thermal protection system (TPS), the white and black tiles that protect the vehicle from excessive heat. During Columbia's liftoff, a piece of insulation from the external fuel tank fell off and hit the orbiter, apparently on the leading edge of the left wing. Whether this impact significantly damaged protective tiles or not, and had any effect on the shuttle orbiter's ultimate breakup during reentry, is being studied.
"We spent a goodly amount of time reviewing" film of the insulation falling off, "and then analyzing" it to see "would there be any consequences," Dittemore told reporters. "It was judged that that event did not represent a safety concern. As we look at that now in hindsight, and certainly we have, all the indications were on the left wing. We can't discount that there might be a connection, but we can't rush to judgment on it. "
Information from several Defense Dept. space-monitoring facilities will also be key to the investigation. Infrared sensors on U. S. Defense Support Program (DSP) satellites are believed to have captured data that could help NASA determine what was happening to Columbia during reentry. Officials at the North American Aerospace Defense Command (NORAD) said they are supporting NASA, but declined to comment on specifics.
NORAD provides missile warning and space-object tracking primarily for defense purposes, but its Space Control Center in Cheyenne Mountain, Colo. , also monitors shuttle launches and on-orbit operations. Using a number of space surveillance systems, NORAD, Air Force Space Command and U. S. Strategic Command provide debris-avoidance information to NASA when the shuttle is in space.
Structural, Systems Integrity Focus Of Shuttle Probe
By William Scott
Investigators probing the loss of space shuttle Columbia on Feb. 1 at about 9 a. m. EST during reentry will probably focus on structural- and systems-integrity.
Data sent via telemetry from the orbiter are being scrutinized for clues that could explain the vehicle's high-altitude break-up.
"We'll be poring over that data 24 hours a day for the foreseeable future," said Ron Dittemore, NASA's space shuttle program manager.
Although details are still slowly emerging from NASA, it appears that both voice and telemetry signals were lost shortly after Columbia emerged from the "blackout" portion of the reentry. Milt Heflin, NASA's Chief Flight Director, said "all vehicle data" were lost when Columbia was at 207,135 ft. altitude and Mach 18. 3.
At a mid-afternoon press briefing, Heflin outlined a sequence of sensor readings and the loss of those readings:
- 8:53 a. m. EST - Lost left wing inboard and outboard hydraulic temperature sensors.
- 8:56 a. m. EST - Left main tire and brake line temperatures increasing.
- 8:58 a. m. EST - "Bondline" temperatures from sensors in the vehicle structure were lost. Three of these were on the left wing's inboard and outboard elevons.
- 8:59 a. m. EST - Left main gear tire temperatures and pressures were lost; these involved eight separate sensor measurements. At about this time, a tire pressure alert was displayed to the shuttle crew, and was apparently acknowledged verbally. This was believed to be the crew's last transmission.
U. S. officials identified several primary areas for investigators' initial focus:
- The trajectory flown by the shuttle as it entered the upper atmosphere. A too-steep approach could cause excessive heating of the vehicle's structure, which could lead to its failure.
- Integrity of the orbiter's structure throughout the reentry.
- The flight controls, including both the reaction control system (RCS) small thrusters that let astronauts fly the orbiter in space -- and aerodynamic surfaces, such as elevons on the aft edge of the wing, which control the vehicle within the atmosphere.
- Possible damage to the thermal protection system (TPS), the white and black tiles that protect the vehicle from excessive heat. During Columbia's liftoff, a piece of insulation from the external fuel tank fell off and hit the orbiter, apparently on the leading edge of the left wing. Whether this impact significantly damaged protective tiles or not, and had any effect on the shuttle orbiter's ultimate breakup during reentry, is being studied.
"We spent a goodly amount of time reviewing" film of the insulation falling off, "and then analyzing" it to see "would there be any consequences," Dittemore told reporters. "It was judged that that event did not represent a safety concern. As we look at that now in hindsight, and certainly we have, all the indications were on the left wing. We can't discount that there might be a connection, but we can't rush to judgment on it. "
Information from several Defense Dept. space-monitoring facilities will also be key to the investigation. Infrared sensors on U. S. Defense Support Program (DSP) satellites are believed to have captured data that could help NASA determine what was happening to Columbia during reentry. Officials at the North American Aerospace Defense Command (NORAD) said they are supporting NASA, but declined to comment on specifics.
NORAD provides missile warning and space-object tracking primarily for defense purposes, but its Space Control Center in Cheyenne Mountain, Colo. , also monitors shuttle launches and on-orbit operations. Using a number of space surveillance systems, NORAD, Air Force Space Command and U. S. Strategic Command provide debris-avoidance information to NASA when the shuttle is in space.
