As they orbited Earth at 27,360km/h with a map of the world rolling past their window 16 times a day, Discovery's crew received an apt wake-up call after their first sleep in space. Tinkling over the airwaves from Mission Control, 285km below in Houston, Texas, came an excerpt from the soundtrack of Groundhog Day, a film whose main character gets stuck in a time warp and repeatedly relives the same day. Little did the wags on the ground at Nasa realise that their choice of music was about to take on added relevance. Hours later, they were experiencing deja vu themselves as footage from Tuesday's launch from Cape Canaveral in Florida revealed the same technical problem that caused the loss of Columbia and its seven crew members in 2003 - a problem that the US space agency had supposedly spent the past 30 months and a large chunk of its budget fixing - had recurred. Instead of revelling in the glory of its long-awaited return to manned space flight, as it had hoped, Nasa is again mired in a public relations disaster. The incident on Tuesday raises new doubts over the viability of the ageing shuttle fleet, concerns over the timetable for its replacement and questions as to where the space programme - and President George W. Bush's bold vision for getting man back to the moon by 2020, and onto Mars and the stars beyond - is really headed. 'At least momentarily, it's a mammoth blow. It's a shock, it's embarrassing for Nasa, it's a huge disappointment that they have not been able to fix the same problem that brought down Columbia,' says Richard Berendzen, a Nasa consultant and physics professor at American University in Washington DC. '[It took] 21/2 years, close to US$1 billion, enormous effort and apparently it didn't work.' The incident in question centred on the external fuel tank's hard foam covering, a substance that has proven to be a thorn in Nasa's side since the shuttle fleet made its debut in 1981. In 2003, a slab of foam broke away from the tank and smashed a hole in Columbia's left wing during liftoff. On its homeward journey 16 days later, Columbia melted in Earth's fiery outer atmosphere when hot gasses seeped through the gash. All seven crew members on board died. Despite the belief that design modifications had eliminated the problem, foam debris flew off Discovery's tank during last week's ascent. Managers admit that it was purely luck that it did not damage the orbiter, which is now carrying Commander Eileen Collins and her six crew on an 8 million km space voyage due to return to Earth next Sunday. With engineers back at the drawing board, and no hope of Discovery or sister ships Atlantis and Endeavour flying new missions until the debris problem has been minimised, the need for an heir to the 24-year-old shuttle fleet has been pulled into sharper focus. So too has the debate over whether the new spacecraft should be reusable like the shuttle, or replaced after each mission - and the question of whether it can all be funded. Over the next two years alone, Nasa will require more than US$30 billion to keep its space programmes ticking. Mike Griffin, who took over as Nasa's administrator in April, says this equates to US$50 per year per American, or 14 US cents a day. 'We as a nation quite literally spend more on pizza than we do on space exploration, so I don't think we are over-spending on space,' he told members of the US Senate during his confirmation hearing. 'A really robust space effort could be had for 20 cents per day from each person. I spend more than that on chewing gum.' Nasa will choose between two rival bids to develop the shuttle's successor, the Crew Exploration Vehicle (CEV), early next year. It has handed two of its engineering partners, Lockheed Martin and Northrop Grumman/Boeing, an eight-month, US$28 million contract each and asked them to present a vision of how the next-generation spacecraft should look. In an attempt to close the 'unacceptable' gap between the shuttle fleet's retirement in 2010 and its first piloted CEV flight, scheduled to take place in 2014, Dr Griffin has accelerated the selection process on the bids by two years. Lockheed Martin has already published preliminary proposals of its concept. It envisages a titanium-shelled, modular vehicle that can be used for near-term trips to the moon and back, and then be modified for the longer journey to Mars. It will also be capable of servicing the International Space Station, an important consideration given that Nasa and space agencies in Europe, Japan, Russia and other countries will have invested a combined US$100 billion in the orbiting laboratory. Tony England - a space expert and professor of electrical engineering at the University of Michigan and former astronaut who flew aboard Challenger in 1985 - is hoping for a sturdier spacecraft. 'The shuttle is a fantastic engineering achievement but it was always a fragile vehicle, and it was always a little optimistic to believe that the first generation vehicle could become fully operational,' he said. 'We designed it from mostly old cloth, and we should have let the technology improve.' Many believe that Nasa's focus on returning the cranky shuttle to flight has come at the expense of other projects, such as scientific experiments into climate change, robotic exploration - which has enjoyed dazzling success on Mars - and the now ailing Hubble Space Telescope. 'I said years ago that the shuttle fleet has had its day,' said Professor Berendzen. 'They talk about, 'Can the shuttle be used to save the Hubble?' 'Well, the shuttle can't save itself and yet the magnificent Hubble will probably continue on its own for another year or two. 'There's the paradox and yet President Bush has led his space plans on returning humans to the moon and Mars. 'I think it's a destiny, fate, the goal, the vision of this industry and the industrialised world that this will happen. But the question is when? The moon by 2020? - no way.'