The basic idea is not actually as far-fetched as it sounds. NASA in 2006 announced plans to set up a colony on the south pole of the moon, in around 2020, as a base for further manned exploration of the solar system.

The problem for Gingrich, a space enthusiast with ideas dating back decades for zero-gravity honeymoons and lunar greenhouses, is that the 2008 financial crisis came along and turned feasible projects into pipe dreams.

``A lunar base by 2020 is a total fantasy,'' John Logsdon, professor emeritus at George Washington University's Space Policy Institute, said.

``We got to the moon in the 1960s by spending over 4 per cent of the federal budget on Apollo. NASA's now at one-tenth of that level.''

During boom time, President George W. Bush called for a return to the moon, followed by Mars expeditions, and NASA drew up plans called Constellation to meet these goals and replace the shuttle fleet when it retired.

But President Barack Obama scrapped Constellation in 2010, saying the plans were ``over budget, behind schedule and lacking in innovation''.

The once-proud shuttle fleet now lies mothballed.

American astronauts now have to rely on Russian spacecraft to get to the International Space Station.

Against this depressed backdrop, Mr Gingrich has left himself open to the charge that his grandiose vision for human spaceflight is simply an attempt to pander to vulnerable voters.

``By the end of my second term, we will have the first permanent base on the moon, and it will be American,'' he said.