Technicians prepare Discovery's external tank for X-ray exams and crack repairs. Photo Credit/NASA Photo
Shuttle managers called for further modifications to the shuttle Discovery’s external fuel tank on Monday, upgrades intended to prevent further cracking of support stringers that have kept NASA’s oldest orbiter from carrying out a final mission since a Nov. 5 launch scrub.
Managers may call for even more upgrades of the aluminum lithium alloy support stringers when they re-convene on Thursday.
The work ordered so far preserves the prospects that Discovery’s 11-day assembly mission to the International Space Station could be flown during the next launch window, Feb. 3 through Feb. 10. More work, however, would likely defer the mission to the next window, Feb. 27 through March 6.
Just last week, managers said an X-ray examination of the 154-foot-long circular fuel tank had found four new cracks on three of the 108, 21-foot-long stringers. They were found after an X-ray analysis of the propellant container’s stringer section in the aftermath of Discovery’s Dec. 17 launch pad tanking test at the Kennedy Space Center.
Technicians found four small cracks on two adjoining stringers following the Nov. 5 launch scrub, which was caused by an unrelated hydrogen leak.
The modifications called for on Monday will add structural enhancing radius blocks to the upper tips of 34 of the stringers. Those stringers extend from either side of two thrust panels on the fuel tank. The panels face the shuttle’s twin solid rocket boosters and shoulder most of the forces as the shuttle climbs to orbit. Two additional stringers flanking the thrust panels were re-enforced during crack repairs at the launch pad following the scrub.
The radius block modification as well as the repairs to the latest cracks were to get under way Tuesday.
In addition, a new round of backscatter X-ray analysis of the 108 stringers is planned this week. Additional studies of the materials and the fuel tank assembly processes are under way as well by shuttle engineers as they attempt to establish a “root cause” for the cracks.
Discovery was moved from the launch pad to the Vehicle Assembly Building at Kennedy following the Dec. 17 test.
Discovery’s six astronauts have prepared to equip the space station with a new storage compartment as well as an external platform to secure spare parts.
The additions are intended to prepare the station for sustained operations following the shuttle’s retirement this year. Endeavour is to fly the final scheduled mission in
April. NASA would like to add a mid-summer supply mission to the station using Atlantis. Congress has yet to decide on the funding.
