CAPE CANAVERAL, Florida (Reuters) - A NASA strategy proposal shifts the U.S. human space program away from returning to the moon in favor of a stepping-stone approach aimed at reaching Mars, including using commercial space launch services, according to a document seen by Reuters.
The proposal is not yet official policy but is the U.S. space agency's response to one of five options contained in review ordered by President Barack Obama of NASA's post-shuttle program that plans to put humans on the moon again by 2020.
A summary of the Human Space Flight Review Committee report, released by the White House on Tuesday, warned however that there could be no meaningful future human space exploration program without more money.
"The U.S. human spaceflight program appears to be on an unsustainable trajectory. It is perpetuating the perilous practice of pursuing goals that do not match allocated resources," the report summary said.
NASA already has spent $7.7 billion of a planned $40 billion to develop a new rocket and capsule for crew transport to the station and the moon, said Jeff Hanley, manager of the post-shuttle program known as Constellation.
But with the review panel tasked to come up with space strategy options, NASA has drafted a concept proposal called "Generation Mars" which envisions a 30-year blueprint for developing technologies, staging precursor missions to asteroids and other destinations, and building grassroots support for eventual human expeditions to Mars.
It also suggests using NASA funds to lure commercial companies into the business of providing launch services for travelers to the International Space Station, a key finding of the space review panel as well.
"You can say that Mars is a destination, but it's really more like Mars is a goal because we're not setting a date," Leroy Chiao, a former astronaut and member of the 10-person review board, said in an interview.
"It's saying these are the things we need to do to build up the infrastructure to get to Mars, this is how much money we have now, and we'll see in the next several years what we think we can get done. Then it'll be for the next budget cycles after that to figure out when we might actually get to Mars," he added.
The "Generation Mars" proposal dovetails with one of the review panel's options setting out a flexible approach to exploration that begins with a five-year extension to the life of the International Space Station to 2020, and development of a new heavy-lift launch rocket.
Shuttle Discovery and seven astronauts are scheduled to return the Kennedy Space Center in Florida on Thursday after a nine-day stay at the space station to deliver supplies and prepare the outpost for its final U.S. connecting node.
The space shuttles are due to be retired late next year or early 2011 after six more missions to complete construction of the station, a $100 billion project involving 16 nations.
The presidential review panel, whose meetings were held in public, considered three options for the new rocket:
-- Slimming down the planned Ares 5 booster, a 188-ton lifter being designed by NASA and contractors ATK Thiokol and Pratt & Whitney Rocketdyne, a unit of United Technologies Corp.
-- Upgrading the Delta 4 and/or Atlas 5 rockets operated by United Launch Alliance, a joint partnership of Boeing Co and Lockheed Martin
-- Developing a new vehicle that makes direct use of existing shuttle components such as its solid-fuel boosters, external fuel tank and main engines.
Both the NASA and the panel's proposals envision using the International Space Station to test medical treatments, life support equipment and alternative propulsion systems to prepare for expeditions to Mars. Commercial companies would be hired to transport astronauts to and from the outpost.
The "Generation Mars" NASA proposal makes no mention of cost. The space program review panel estimates that its similar option would need another $3 billion a year.
Although the review panel was directed to come up with two options that fit within NASA's current $18 billion annual budget, members found that "no plan compatible with the (existing) budget profile permits human exploration to continue in any meaningful way," the report said.
Sticking with the present program would give the United States its heavy-lift Ares 5 by about 2028, but there would be no money to develop a lunar lander or even a rocket motor to leave Earth's orbit.
Editing by Pascal Fletcher and Cynthia Osterman