由于火箭问题SIRTF发射再次推迟（至8月）

Solid rocket booster problem delays SIRTF until August

BY JUSTIN RAY
SPACEFLIGHT NOW
Posted: April 18, 2003

                               
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SIRTF atop the Delta 2 at pad 17B as workers recently installed the two-halves
of the rocket's nose cone. Photo: NASA


Worried that a suspect rocket nozzle on one of the Boeing Delta 2's solid-fuel
ed boosters could trigger a catastrophic failure during launch, NASA on Friday
grounded the Space Infrared Telescope Facility until mid-August.
SIRTF was already sitting atop the $68 million rocket and set for the final da
ys of launch preparations. But after multiple delaminations with the layers of
carbon material that make up the nozzle of one strap-on solid rocket motor we
re found during pre-flight preparations, the space agency ordered a postponeme
nt. The delamination occurs when the adhesive bond between the layers is lost,
NASA said.

The fourth and final of NASA's Great Observatories had been scheduled for blas
toff Friday aboard the first Boeing Delta 2 Heavy rocket from Cape Canaveral A
ir Force Station's pad 17B. But earlier this month, senior officials in Washin
gton put the launch on hold while additional reviews were conducted into the i
ntegrity of the Delta 2's strap-on solid-fueled boosters.

With the liftoff already delayed to the end of April, NASA was facing a May 7
deadline to get SIRTF airborne so the pad could be readied for another Delta 2
flight in June carrying the second Mars Exploration Rover. That Mars launch m
ust fly during a tight 18-day window beginning June 25 when Earth is properly
aligned to dispatch the robotic craft to the Red Planet.

On Friday, the agency announced the suspect booster -- one of nine attached to
the rocket's first stage -- would have to be replaced before launch would occ
ur. The time to make such a switch wasn't available before the May deadline, f
orcing SIRTF to wait until after the Mars mission.

"There simply is not enough time to remove and replace the rocket motor to sup
port a SIRTF launch in advance of the Mars Exploration Rover-B launch window,"
said Karen Poniatowski, assistant associate administrator for launch services
at NASA Headquarters.

NASA said the super-hot exhaust from the booster could have burned through the
suspect nozzle, causing the motor to fail and dooming the launch.

Both SIRTF and that second Mars rover use the Delta 2 Heavy rocket configurati
on, which is distinguished by the larger solid rocket motors originally develo
ped for the Delta 3 vehicle. The solids are 46-inches in diameter vs. the 40-i
nch solids normally used on Delta 2s. The motors are built by Alliant Techsyst
ems.

Complex 17 has two launch pads but only pad 17B is designed to handle the larg
er solids.

NASA said the 46-inch solids earmarked to be used on the Mars launch have been
cleared for flight.

Teams are now developing plans to return SIRTF to its processing facility at t
he Cape and disassemble the rocket from the pad.

The SIRTF rocket will be restacked on the pad following the Mars launch. The o
bservatory should return to the seaside complex following the late-July liftof
f of an Air Force GPS satellite from neighboring pad 17A.

NASA estimates the delay will add $2 million per week to the $1.19 billion mis
sion's price tag.