NASA could save $3 billion to $6 billion by dumping its Ares I rocket and flying Orion spacecraft and U.S. astronauts on upgraded Delta IV Heavy rockets, according to an independent assessment released by NASA on Tuesday.
But the report also said that course of action would increase by $1.1 billion to $3.5 billion the cost to develop NASA's Ares V heavy-lift launch vehicle.
What's more, NASA estimates it would cost an additional $14.1 billion to $16.6 billion to finish development of the Orion crew exploration vehicle if NASA switched to Delta IV Heavy rockets.
The June 1 Aerospace Corp. report was released a day ahead of a presidential panel's final public hearing on the future of the U.S. manned space flight program. The panel will present options to the White House by the end of the month.
The report failed to address a key issue raised by Columbia accident investigators: crew survivability.
The federally funded research and development group, which played a key role in developing Air Force Delta 4 and Atlas 5 rockets in the 1990s, limited the report's scope to technical feasibility, cost, schedule and impacts to NASA's Project Constellation and national security space programs.
"Aerospace did not perform estimates of loss of mission and loss of crew probabilities" for upgraded Delta 4 Heavy rockets, the report said.
Previous NASA studies indicate Ares I would be twice as safe.
Columbia investigators said NASA should give "overriding priority to crew safety, rather than trade safety against other performance criteria," when designing rockets and spacecraft to replace the agency's shuttle fleet.
NASA is developing its Ares I rocket to launch astronauts aboard Orion crew capsules. The Ares V moon rocket is to launch Altair moon landers and rocket stages to propel the landers and Orion capsules from Earth orbit to lunar orbit.
The June 1 report focused specifically on the implications of replacing the Ares I rocket with Delta IV Heavy rockets.
Ares V "carrying costs" of up to $3.5 billion would result from stalling development of five-segment solid rocket boosters and a second stage engine required for the Ares I and Ares V.
The huge rise in Orion costs would be associated with adapting the capsules to fly on Delta IVs and revising mission design work, environmental assessments and ground operations plans.
Among other costs: Maintaining the industrial capability to manufacture solid rocket boosters between the 2010 retirement of NASA's shuttle fleet and the development of the Ares V rocket in the latter half of the next decade.
The Aerospace Corp. said it had not independently verified NASA's estimates for Orion cost increases or the underlying assumptions.
The development of a Delta 4 Heavy rocket certified to fly astronauts would take 5.5 to seven years, the report said.
NASA says the Ares I rocket and Orion spacecraft is expected to fly its first piloted mission in March 2015, although project officials privately acknowledge that target could slip to mid-2015.
Orion spacecraft development would slip about a year, the report said.
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