Discovery's external tank was laced with strain gauges and temperature sensors for Friday's troubleshooting. Photo Credit/NASA
NASA will spend a couple of weeks assessing the results of shuttle Discovery’s tanking test on Friday at the Kennedy Space Center, the latest round of troubleshooting intended to explain the formation of small cracks on the spacecraft’s external fuel tank during a Nov. 5 launch scrub.
Discovery’s 39th and final flight, an 11-day supply mission to the International Space Station, has been on hold since the scrub, which was blamed on an unrelated hydrogen leak.
The evaluation of the six terabytes of data gathered from Friday’s elaborate test will require at least two weeks to evaluate, said Mike Moses, NASA’s shuttle launch integration manager.
However, an assessment of the measurements from strain gauges and temperature sensors fitted to Discovery’s 154-foot-long external tank — ET — prior to the test should be far enough along this weekend to schedule the shuttle’s “roll back” from Launch Pad 39A to the Vehicle Assembly Building early next week.
Once in the Kennedy hangar, Discovery’s fuel tank will be X-rayed to determine whether it was further damaged on Friday, as the tank was filled with chilled liquid oxygen and hydrogen propellants. Shuttle managers believe that four small cracks surfaced in a pair of 21-foot-long stringers on the ET’s intertank during the early November launch attempt.
The stringer cracks were discovered by technicians during repairs to a longer crack in the insulating foam that that covered the stringer damage.
A collection of 108 stringers separate internal ET hydrogen and oxygen containers. The hydrogen flows at temperatures of minus 423 degrees below zero Fahrenheit, the oxygen at minus 298 degrees. The super cold temperatures may have caused the initial cracks — if they intertank was not property assembled, shuttle managers believe.
Friday’s test should help them to confirm their hypothesis, or lead them to a new explanation.
As they troubleshoot, shuttle engineers have also developed a strategy to fortify the weakest part of the intertank if the engineering detective work points to a need, said Moses.
In all, 89 strain and temperature sensors were applied to the interior and exterior of the intertank for Friday’s test. In addition, thousands of small dots were painted on the outside of the tank so that high resolution cameras focused on Discovery could measure subtle contractions and correlate them to falling temperature during the propellant flow.
The earliest Discovery’s six astronauts could lift off would be Feb 3 at 1:37 a.m., EST, which marks the start of a 10-day launch period.
Discovery would have to return to the launch pad in mid-January to be ready.
The next launch period begins Feb. 27.
“Feb. 3 is a challenge, but we will stay on it,” said Moses. “It’s a target for our milestones right now, and we will not pick a launch date until we have much better look at what the data is telling us.”
The hydrogen leak did not return on Friday.
After the early November scrub, NASA replaced a misaligned Ground Umbilical Carrier Plate on the ET.
“Everything worked perfectly,” said Charlie Blackwell Thompson, the NASA test director who monitored the carrier plate on Friday. “We’re glad to have that behind us.”
Discovery’s six astronauts have trained to equip the station with an equipment storage compartment and an external platform with spare parts.
The improvements will help to prepare the station for operations after the shuttle program’s final mission. Two and possibly three more flights are planned by mid-2011.