BioEd Online

NASA celebrated Independence Day with the successful launch of the space shuttle Discovery.

Discovery took off at 14:38 EDT under scattered clouds from the Kennedy Space Center in Cape Canaveral, Florida, on 4 July. The orbiter is now en route to the International Space Station where it will deliver a crew member, European Space Agency Astronaut Thomas Reiter, along with equipment and supplies. Discovery astronauts will also conduct two spacewalks to service the station during their 13-day mission.

The launch seemed to go smoothly despite concerns about insulating foam coming off the main fuel tank and striking the shuttle, as occurred with disastrous consequences in the Columbia shuttle in 2003. Yesterday, managers conducted a last minute evaluation of a bread-crust-sized piece of foam that fell from Discovery's tank during repeated refuelling. They determined late last night that the crack in the foam was unlikely to cause further damage (see ' NASA set to launch shuttle 4 July').

Early examinations of footage of the launch showed that some small of pieces foam shed from the tank, but only in the amount expected and with no cause, as yet, for concern. Astronauts are planning to examine the orbiter in the next few days for any signs of damage before rendezvousing with the space station.

On the horse again

The mission is the second of NASA's ' return to flight' missions after the 2003 accident that saw Columbia break apart on re-entry. The first successful launch after this accident was also by Discovery, almost exactly a year ago. That 26 July 2005 launch initially seemed to go perfectly. But a day later, NASA found that the craft suffered from a large chunk of foam coming off the fuel tank, the loss of a small piece of heat-shielding tile, and a handful of other small dents and dings.

NASA grounded the rest of the fleet until further notice. But after in-space repairs, Discovery returned safely home in August 2005 (see ' NASA's shuttle programme - a timeline'). Additional modifications saw it declared fit to launch again.

Sixteen more flights will be needed to complete the International Space Station before NASA retires the shuttle in 2010. However, continuing worries about foam and other aspects of the aging fleet's operations may make it difficult to stay on schedule, according to Alex Roland, a shuttle historian at Duke University in Durham, North Carolina, and critic of the programme. "I think the prospects are very low that they will be able to fly out that schedule," he says.

NASA officials say that the next shuttle flight, of Atlantis, may happen as soon as 28 August.

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