WASHINGTON -
The addition of an extra mission to NASA's space shuttle flight manifest could
significantly reduce the chance of retiring the orbiter fleet in 2010 as
planned, possibly to as low as 5 percent, the Congressional Budget Office (CBO)
said in a report released Monday.
The CBO
studied risks associated with delaying the space shuttle's retirement and how
that would affect work on the replacement system - consisting of the Orion
Crew Exploration Vehicle and the Ares I launcher - which is expected to
debut in 2015.
The report
concluded there was a 20 to 60 percent chance NASA would be able to fly all of
the 10
scheduled shuttle missions in the next two years. The addition of an 11th
mission to transport the Alpha Magnetic Spectrometer to the space station, as
Congress has directed, would reduce that probability to between 5 and 30
percent, the CBO report said.
NASA plans
to shift space shuttle program money to Orion and Ares after the shuttle
retires, and has stated, according to the CBO report, that it might cancel
shuttle flights not accomplished by September 2010. Meanwhile, the U.S. space
agency continues to study options for speeding up the first Orion
and Ares I flights by up to 18 months.
NASA
currently is working toward a September 2014 debut for the new system, a target
six months sooner than the March 2015 date it has promised the White House and
Congress it can meet, budget permitting.
The CBO
report notes that until August, NASA had said there was a 30 percent chance
Orion and Ares I would be operational by September 2013 if an extra $1 billion
was added to the agency's 2009 and 2010 budgets. NASA now says additional
funding "can no longer significantly change either the estimated date for or
NASA's level of confidence about its achievement of the [initial operating
capability] milestone," the report states.
The gap
between the shuttle's retirement and the first flight
of Orion and Ares I could widen if NASA cannot keep Orion's mass from
growing during development. Other issues that could delay Orion and Ares I
include a longer-than-expected development of Ares
I's J-2X upper-stage engine, difficulties with the Orion's heat shields and
excessive thrust oscillation in Ares 1's first stage, the CBO report said.
The report
also said a $577 million reduction in NASA's 2007 funding prompted NASA to
forego some robotic lunar surface exploration missions, which could delay plans
to return astronauts to the Moon by 2020.
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