The delay
of NASA's next space shuttle flight has thrown a monkey wrench into plans to
return a U.S. astronaut home from the International Space Station (ISS),
mission managers said Tuesday.
NASA
astronaut Sunita "Suni" Williams was slated to return to Earth in July with
space shuttle Endeavour's STS-118 crew after a six-month flight that bridges
the Expedition 14 and Expedition 15 station missions.
But the delay
of the ISS construction flight immediately before Williams' return ticket - NASA's
STS-117 mission to fly no earlier than mid-May - may push the astronaut's
Earth homecoming later into this summer, Kirk Shireman, NASA's deputy ISS
program manager, told reporters in a Tuesday briefing.
Hail damage
to the space shuttle Atlantis' external tank prevented the orbiter's planned
March 15 launch. NASA is expected to set a new liftoff target on April 10.
"We're
looking at..exactly what that means and what the delay is, and we're certainly
keeping Suni abreast of what the developments are on the ground," Shireman said.
"Medically, we're talking to her and doing things as best we can to make her
happy and perhaps launch some special items that'll make her more comfortable
for that extended period of time.
"Aside from
that, there's not a whole lot that we can do. She's up there, and [STS-118 is] the
ride home and she knew that before she launched," Shireman added.
Williams
launched to the ISS aboard the Discovery orbiter in December during NASA's
STS-116 mission, where she replaced European Space Agency
astronaut Thomas Reiter as a flight engineer on the Expedition 14 crew. Her
crewmates, Expedition 14 commander Michael Lopez-Alegria and flight engineer
Mikhail Tyurin, are scheduled to return to Earth on April 20 after their replacements
arrive, but she will stay on for the first leg of Expedition 15.
The space
station's Expedition
15 mission includes a convoluted series of ISS astronaut swaps that begin
with the planned April 9 arrival of Williams' next crewmates - cosmonauts Fyodor
Yurchikhin and Oleg Kotov - aboard their Russian-built Soyuz TMA-10 spacecraft.
Williams is
due to be relieved by NASA astronaut Clayton Anderson, who will launch aboard
Endeavour on the STS-118 mission and himself be replaced by U.S. spaceflyer
Daniel Tani during the STS-120 shuttle mission currently targeted for a late August liftoff.
"It
does add a lot of complexity," Williams said of the crew rotation plan during a
preflight NASA interview.
NASA has
historically limited its long duration astronauts to missions that span as
close to six months as possible, though there is some leeway in determining
their maximum flight time, mission managers said.
"There are
no specific flight rules that dictate that. We have to look at the entire
environment that they're in," Dave Alexander, NASA's lead Expedition 14 flight
surgeon, said Tuesday, adding that factors such as physical fitness, space radiation
exposure and mental health are examined. "Right now, the predictions are that Suni
can stay for an extended period of time."
Shireman
said that there is a remote possibility that Williams could return home with the
STS-117 crew, but only if a significant problem arose with the preparations or
timing of her STS-118 return trip. In that case, Anderson could be added as a
seventh member of Atlantis' STS-117 crew.
"It's
unlikely at this point, but not out of the realm of possibility," Shireman
said.
Adding
Clayton to the STS-117 mission prompts a series of challenges, the least of which
being the fact that Discovery's cargo of new ISS solar arrays attached to a
17.5-ton pair of truss segments leaves little weight allowance for the Russian
Sokol spacesuit, Soyuz seat liner and other vital supplies required for a new
station crewmember, Shireman said.
The planned
11-day mission to perform three spacewalks to install those new solar arrays
and also leaves little time for handover activities between Williams and
Anderson, he added.
"So we'd
prefer not to do that," Shireman said.
From a
health standpoint, Williams - who joined NASA's astronaut corps hoping for a berth
aboard the space
station - is as sharp as ever for her long spaceflight, flight controllers
said.
"She's fit
and ready to continue on in most of her adventures," Alexander said.
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