Discovery's liftoff on that date would occur in the middle of a ten-minute window at 1:36 a.m. EDT.
Today's decision came at the end of a marathon executive-level Flight Readiness Review. The meeting was supposed to conclude yesterday but stretched into Wednesday because of the detailed discussions surrounding the problematic foam insulation. Despite that, manager stressed that the FRR discussions were not contentious and no-one objected with the decision to launch Discovery.
"In the end, we let everyone kind of state their opinions," said NASA Associate Administrator for Space Operations Bill Gerstenmaier. "No one chose to appeal the decision, but there were definitely some differing opinions amongst the group and I think that's really good, that's what we've been trying to get."
During Endeavour's launch on July 15, a large amount of foam peeled off the corrugated intertank region between the liquid hydrogen and liquid oxygen sections of the external tnak, which was ET-111. The tank also lost a piece from an ice-frost ramp on the oxygen side and another piece from the left bipod strut.
NASA has paid special attention to foam shedding issues in the years since shuttle Columbia was brought down by a hole in its left wing that was caused by a huge chunk of foam that broke off 85 seconds after launch and slammed into the leading edge of the wing. The inside of the wing melted during re-entry, causing Columbia to spin out of control and break apart, killing the seven astronauts aboard.
"I read a couple of comparisons that said this was similar to Columbia," said shuttle Program Manager John Shannon. "And of course on Columbia, we had a 2.2-pound piece of foam come off and damage the wing. The loss we had on the last flight that generated all of this discussion over the last two weeks was 0.044 pounds, which is one-fiftieth the size of the Columbia foam.
The most likely cause of the foam loss on the intertank region appears to be some form of foreign contamination preventing the foam from adhering properly when it was sprayed on. Engineers cleared the intertank region of Discovery's tank, ET-132, by performing about 200 so-called "plug pulls" around the circumference of the tank to verify the adhesion of the insulation to the underlying primer surface.
NASA's big concern was the insulation loss from the ice-frost ramp. A similar event also occurred during Atlantis' launch on the Hubble repair mission. The ice-frost ramps are sensitive areas that have proven troublesome in the past. They are specially-shaped sections of foam designed to smooth out the flow of air over the bracket that attach pressurization lines to the outside of the external tank during launch.
Engineers suspect that voids in the foam had trapped air which cools and partially condenses when the tank is filled with supercold propellants. During launch, as the vehicle ascends through the lower atmosphere, the outside of the tank warms up due to aerodynamic friction. As the trapped air gets warmers, it expands and causes pieces of insulation to pop off.
As a result, engineers performed a series of terahertz scans on the ramp in question on ET-132 and determined there are no voids of concern.
As an added measure of confidence building, the same tests and plug pulls were performed on the next tank to fly, ET-133. Those tests shoed good adhesion in the intertank region and only about 10 relatively insignificant voids in the ice-frost ramp.
Meanwhile, the STS-128 crew arrived Wednesday evening at Kennedy Space Center for their final prelaunch preparation. Pausing for a brief moment to talk with media, Commander Sturckow said, “It’s great to be here for the launch. We’ve been studying and training hard, and we’re ready to go accomplish this mission.”
The STS-128 crew is led by three-time shuttle astronaut Rick "C.J." Sturckow, a 49-year-old Marine Corps colonel. He will be joined by rookie pilot Kevin Ford, also a 49-year-old Air Force colonel.
Rounding out the crew are mission specialists Patrick Forrester, Jose Hernandez, Danny Olivas, Christer Fuglesang and Nicole Stott, a former KSC engineer making her first spaceflight.
Stott will replace Tim Kopra as a flight engineer aboard the International Space Station. Completing a relatively short stint on the station that began last month, Kopra will return home on Discovery.
Discovery will deliver more than 15,000 pounds of supplies to the station, including the C.O.L.B.E.R.T. treadmiill during its 13-day mission.
(The Spacearium / Spcae Media Corporation)
RETURN TO THE SPACEARIUM HOMEPAGE
|
|
