NASA aims to launch Discovery on Feb 24

NASA engineers have been working since Nov to figure out why cracks were emerging on the stringers.

Updated: Jan 12, 2011, 13:41 PM IST

Washington: NASA has said it will aim to
launch the space shuttle Discovery February 24, after
engineers found a way to shore up cracks on its external fuel
tank that have delayed its final liftoff.

"We think we can support a launch date for the 24th of
February," International Space Station Program manager Mike
Suffredini said Tuesday.

NASA engineers have been working since November to figure
out why cracks were emerging on the 22-foot-long U-shaped
aluminum brackets, called stringers, on the shuttle`s external
fuel tank.

According to shuttle program manager John Shannon,
engineers performed exhaustive tests and found that the
complex problem was not solely a result of material quality or
flaws that took root during assembly.

Shannon described the dilemma as "low risk" but at the
same time, "hard to quantify."

In the end, engineers agreed that installing small metal
strips, called radius blocks, on to the stringers would
reinforce their strength.

"It is very hard to tell where your assembly stresses
are, you can`t really tell that by X-ray, so what we decided
to was we could get rid of the whole discussion by putting in
these things called radius blocks," Shannon said.

"It is a very simple, elegant fix to the problem," he

"We are going to fly with a lot of confidence in this
tank," Shannon told reporters.

The work that is currently being done to fix the
stringers should be complete by January 23, Shannon said.

"I`m very confident that we finally got it figured out,"
said Shannon. "We are on the road to bringing this tank to 100

Discovery has been plagued by setbacks since its latest
attempt to launch was scratched on November 5 when technicians
found a hydrogen leak and later a series of long cracks on the
shuttle`s external fuel tank.

Another shuttle, Endeavour, is set to take off in April
in what will be the last shuttle launch scheduled for the US
program, though a final launch could take place in the summer
before the entire fleet is retired for good.

NASA officials declined to answer questions about the
Endeavour launch, which is to be led by astronaut Mark Kelly.

Kelly`s wife, US lawmaker Gabrielle Giffords, is
recovering from a gunshot to the brain after a political
meeting in Tucson, Arizona.

The Discovery has launched into space 38 times, and NASA
aims to retire the shuttle after its final and 39th voyage.

Discovery is the oldest in the remaining three-shuttle

The three US shuttles -- the other two are Atlantis and
Endeavour -- are due to become museum pieces once the final
shuttle mission takes place.

Then, the Russian Soyuz spacecraft -- a modernised
version of which recently dropped off three fresh crew members
to the ISS, doubling the crew to six -- will for several years
be the only vehicle for transporting humans into space.