NASA's shuttle Atlantis and its six-astronaut
crew will launch toward the International Space
Station (ISS) on Aug. 27 provided engineers conquer some final issues,
among them a possible antenna
bolt swap, agency officials said Wednesday.
Top
spaceflight officials voted unanimously to press ahead with Atlantis STS-115
mission today after an extended two-day meeting at NASA's Kennedy Space
Center (KSC) in Florida, William Gerstenmaier, NASA's associate administrator
for space operations, said in a press briefing Wednesday following a Flight
Readiness Review.
Two senior
NASA directors - in charge of the agency's Johnson Space Center and Marshall
Space Flight Center - gave their approval with the caveat that some shuttle
fuel tank modifications be made as soon as possible, Gerstenmaier added.
"This was a
great review and I'm looking forward to moving toward a great launch," NASA
chief Michael Griffin said of the meeting, adding that the agency is already
committed to making the next fuel tank fix - the removal of several ice
frost ramps to reduce the amount of foam insulation debris at launch - in
two shuttle flight's time.
Atlantis
and its STS-115 astronaut crew are now set to launch at 4:30 p.m. EDT (1030 GMT)
on Aug. 27 to deliver a new pair of solar
arrays and truss segments to the ISS. The mission, commanded by veteran
shuttle flyer Brent
Jett, will mark the first major ISS construction flight since late
2002.
The
spaceflight will also be NASA's third shuttle mission since the 2003 Columbia accident.
Antenna
bolt bustle
Shuttle
officials spent less time debating the ice frost ramp fix and safety of Atlantis'
foam-covered external tank, as they did the potential need to replace two bolts
on a vital antenna attached to the forward right wall of the orbiter's payload
bay, NASA officials said.
Engineers
found that two of four bolts holding Atlantis' Ku-band antenna - which provides
video, voice and data communications - to the payload bay wall are too short
despite performing as expected for 26 spaceflights. There is some concern
that the bolts could give way during launch, sending the antenna plunging down
the length of Atlantis' cargo bay and causing serious - possibly catastrophic -
damage to the orbiter.
"For the
last 25 years we've been flying with these thread fasteners, bolts, that just
barely have a thread or two engaged into the nut that holds them on," said
NASA's space shuttle program manager Wayne Hale. "That is not good engineering
practice."
Similar
antenna bolts aboard NASA's Discovery and Endeavour orbiters have already been
replaced with longer units, but the swap will be harder for Atlantis since the
shuttle sits in launch
position atop Pad 39B at KSC instead of its maintenance hangar.
"We've
flown 26 times and everything has been okay, and there is a school of thought
that suggests it will be okay one more time," Hale said. "But I would rather
have the engineering data to back that up."
To replace
the antenna bolts, pad workers would have to extend a slim platform out between
the top of Atlantis' solar array-truss payload and ISS docking port at the
upper end of the orbiter's 60-foot (18-meter) cargo bay.
"Imagine
operating on a surfboard that's tied down at one end, sticking out over a
six-story balcony," Hale said. "If we have to do it, it will be done safely and
will be done properly, but if we don't have to do it than that would just be
great too."
A decision
on whether that work is required could be made this weekend. With two extra
days built into Atlantis' launch schedule, the extra work- if needed - should
not affect the Aug. 27 target, NASA launch director Michael Leinbach said.
Hale also
said that engineers are working through a heater thermostat issue on one of
Discovery's three auxiliary power units (APUs) feeding its hydraulic system to
determine if a similar problem could be present aboard Atlantis.
"Right now
we think Atlantis has tested out just fine, so whatever problem there is on
Discovery it's likely not there on Atlantis," Hale said.
Unanimous
decision
Unlike
NASA's last shuttle Flight Readiness Review, in which NASA's top safety
official - former shuttle commander Bryan O'Conner - and chief engineer
Christopher Scolese voted
against moving ahead with Discovery's STS-121
launch, today's final discussion proved less of a contest.
O'Conner
and Scolese did not object to the STS-115 launch plan, and added that the
flight rationale
given for Discovery's STS-121
mission - in which the risk
was to the orbiter itself but not its astronaut crew - was still valid.
[Click here
for Griffin's STS-121 launch rationale].
"I would
say that this review was less contentious, maybe not a lot less but I don't
want them to be," Griffin said, adding that airing concerns is a vital part of
the engineering process. "The point is we don't feel that we're risking crew,
and no one in the room felt like we were risking crew."
Even if
Atlantis suffers damage serious enough to force the STS-115 crew to take refuge
aboard the ISS and await a rescue mission, the station could support the
shuttle astronauts for between 86 and 110 days, NASA station officials said
last week.
"In the
end, everybody said let's go," Griffin said.
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