Nasa will not be able to meet its target of sending humans back to the Moon by 2020, or even dream of landing on Mars, because it is suffering from chronic underfunding, a presidential review panel has warned.

The US space agency needs at least another $50 billion (£30 billion) over the next decade if it is to come close to delivering on its vision for retiring the space shuttle, completing construction of the International Space Station and launching ambitious new voyages of discovery.

The bleak assessment comes from a ten-member committee established by President Obama to review America’s manned spaceflight programme. Made up of aerospace experts and former astronauts, it is not due to make its final report until the end of this month.

But at its final public hearing, the panel revealed that it has already concluded that Nasa’s current goals are “not executable”.

Without extra funding for Constellation, the programme that will replace the shuttle fleet and send astronauts farther out into the solar system using a new generation of spacecraft, the Moon is unlikely to receive human visitors again until at least 2030 and Nasa risks building a rocket to nowhere.

“If Santa Claus brought us this system tomorrow, fully developed, and the budget didn’t change, our next action would still have to be to cancel it,” Jeff Greason, a committee member and aerospace pioneer, said.

“We are on a path right now for a system that requires roughly double the current budget just to operate,” he added.

Sally Ride, a retired shuttle astronaut who became the first American woman in space in 1983, agreed. “It can’t be done, it can’t be done,"she said.

About $9 billion has already been spent on Constellation, but Nasa has had $30 billion slashed from the programme’s budget in recent years and the $81 billion remaining is inadequate.

“Our view is that it will be difficult with the current budget to do anything that’s terribly inspiring in the human spaceflight area,” Norman Augustine, the panel’s chairman, said.

The pessimistic forecast comes less than a month after America marked the fortieth anniversary of the Apollo 11 mission that put Neil Armstrong and Buzz Aldrin on the Moon.

Behind the glitzy celebrations, however, there has been conflict and debate over where Nasa should set its future sights. While many want to see a return to the Moon to establish a manned outpost, others, including Aldrin, believe that another lunar landing would be a waste of resources – they advocate heading for the unexplored terrain of Mars.

Among the panel’s suggestions to President Obama – which it will discuss during a preliminary meeting at the White House today – will be for Nasa to save resources by commissioning the private sector to carry humans and cargo to the space station, freeing up resources for more adventurous missions.

Such expeditions could include sending crews to land on asteroids and to explore areas of deep space a million miles from Earth, where fuel depots could be set up to resupply manned missions to Mars.

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