The commander of the space shuttle Discovery said today that she was surprised and disappointed that the spacecraft appears to have suffered from the same problem of falling debris that led to the Columbia disaster in 2003.

Speaking from orbit as her crew continued to inspect the fragile exterior of the shuttle, Commander Eileen Collins said that she was not worried about the minor damage sustained by Discovery during its launch on Tuesday, but agreed with the decision to ground the rest of the shuttle fleet.

"What I’d like to say is this is something that has to be fixed," Commander Collins said of the tendency for pieces of foam to fall off the shuttle as it blasts off. "I don’t think we should fly again unless we do something to prevent this from happening again."

"We were actually quite surprised to hear we had some large pieces of debris fall off the external tank. It wasn’t what we had expected," she added. "Frankly, we were disappointed to hear that had happened."

Several pieces of foam peeled away from the external fuel tank of Discovery during its lift-off three days ago, but Nasa believes that only one may have struck the sensitive exterior of the shuttle as it fell. According to Commander Collins, the spacecraft looks "very clean" and is safe to return to Earth.

A large piece of foam hit the left wing of Columbia during its launch in 2003 and caused its eventual disintegration as it re-entered the Earth's atmosphere 16 days later. Since then Nasa has spent two-and-a-half years and nearly $1 billion (£573 million) trying to fix the problem.

Commander Collins was speaking on Discovery's first full day of conjoined orbits with the International Space Station. As she answered reporters' questions from 122 miles above Earth, the rest of her crew and the two station members were busy loading supplies into the space station and carrying out further inspections to the delicate surface of the shuttle.

Last night Nasa admitted that one of the pieces of debris that fell from the shuttle's external fuel tank during lift-off may have hit the spacecraft's right wing.

"This is the closest to a potential hit that we have out of all the data we’ve got," said Wayne Hale, the deputy shuttle programme manager, who stressed that even if the piece of foam did hit Discovery, it was not large enough to cause any serious damage.

"We feel very good about this," he added

Nonetheless, two of Discovery's seven astronauts used the shuttle's laser-tipped robotic arm today examine the of the thermal tiles that will protect the 21-year-old shuttle on its re-entry through the Earth's atmosphere.

As well as inspecting the right wing, the crew brought the laser and video cameras to bear on a total of 11 areas of the surface of the shuttle, including a patch of damaged tiles around the nose landing gear which Nasa engineers had not been able to look at until today.

The nose and wing tips of the spacecraft will have to withstand temperatures of 3,000C (5,430F) as the shuttle plummets through the atmosphere on its return to Earth on the morning of August 7.

The two other tasks for the crew of Discovery today were to move a huge barrel of supplies, known as "Raffaelo", into the space station and to prepare for the three spacewalks that the crew will take over the coming days.

Raffaelo, which contains 13.6 tonnes of supplies, including lightbulbs, laptop computers and oxygen, was swung over to the ISS earlier today by the same crane that the astronauts used to examine the shuttle's exterior.

Shuttles are the only spacecraft that can carry the large loads critical to the building of the $95 (£54.5) billion space station. Over the coming days, Discovery will deliver a new storage platform and install a gyroscope on the ISS, whose development has been slowed by the delays to the shuttle programme.

Two astronauts, Stephen Robinson and Soichi Noguchi, will take the mission's first spacewalks tomorrow, when they will practise new repair techniques for the shuttle's tiles. They spent hours today getting accustomed to the air pressure of their suits and testing the nitrogen-powered boosters that they can use to return to the shuttle should they become untethered and start to float away into the nothingness of space.

Although Discovery seems to be largely unharmed, Nasa has grounded the rest of the shuttle fleet for the forseeble future, including Atlantis, which was due to fly in September and come to the rescue of Discovery in an emergency.

Should the crew of Discovery need rescuing, a relay of three Russian Soyuz spacecraft will sent into space to pick them up.

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