CAPE CANAVERAL, Florida (Reuters) - The United States needs to boost NASA's budget by $1.5 billion to fly the last seven shuttle missions and should extend International Space Station operations through 2020, members of a presidential panel reviewing the U.S. human space program said on Tuesday.
A subcommittee of the 10-member board also proposed adding an extra, eighth shuttle flight to help keep the station supplied and narrow an expected five- to seven-year gap between the time the shuttle fleet is retired and a new U.S. spaceship is ready to fly.
A third option would keep the shuttle flying through 2014 as part of a plan to develop a new launch system based on existing shuttle rockets and components.
At the very least, NASA's budget -- $18 billion in the fiscal year ending September 30, 2009 -- should reflect the reality that it is highly unlikely to complete seven remaining shuttle missions by September 30, 2010, as planned, board members said.
"We have come to believe very firmly that it's important to have a realistic view of what the existing program as it will realistically unfold most likely will cost and not put any smoke and mirrors to the budget to make it look like it will fit under the budget profile," Sally Ride, a committee member and former astronaut, told her colleagues during a public meeting in Houston televised by NASA.
With NASA averaging about 115 days between shuttle missions over the past five years, the more likely time frame for completion of the space station and the retirement of the fleet is March 2011, panel members said.
"But, of course, there is no funding for that possibility," Ride said. "That's setting you up right away for a budget problem."
NASA has estimated it would need $1.5 billion to accommodate the delay. Adding an eighth flight would require an additional $2.7 billion over that.
The panel, headed by former Lockheed Martin Corp Chief Executive Norm Augustine, was convened by President Barack Obama to come up with options for the U.S. human space program. It is expected to issue a report in August.
NASA's current plan, ordered by former President George Bush after the Columbia accident, is to complete the space station, retire the shuttles and build new spaceships. In addition to traveling to the space station, which orbits 225 miles above Earth, those new ships would ferry crews to the moon and other destinations.
Funding for the $108 billion program would come from funds previously used for the shuttle and the space station, which under the plan would be dumped into the ocean in 2015, five years after becoming fully operational.
Michael Coats, a former astronaut who oversees the Johnson Space Center in Houston, told panel members that abandoning the station then was "inexcusable."
The United States' partners in the $100 billion program -- Russia, Europe, Japan and Canada -- unanimously support maintaining the station beyond 2015, said panel member Lester Lyles, a former Air Force vice chief of staff.
"The politicians are looking for a return on investment," he said.
Also on Tuesday, the visiting shuttle Endeavour crew wrapped up its 11-day stay at the station, leaving behind a new platform to hold telescopes and other science experiments, and a cache of spare parts to keep the station operational after the shuttle fleet's retirement.
"We're sad to leave you but hopefully happy that we left the station in pretty good shape," Endeavour commander Mark Polansky told the station crew in a brief farewell ceremony.
Left aboard the outpost was NASA astronaut Tim Kopra, who takes over the flight engineer's job previously held by Japan's Koichi Wakata. Wakata, who has been in orbit for 4 and 1/2 months, returns home with the Endeavour crew on Friday.
Editing by Jane Sutton and Paul Simao