The space shuttle Discovery will blast off on July 1, despite the severe misgivings of both NASA’s chief engineer and safety officer.

The chief engineer, Christopher Scolese, and the head safety officer, Bryan O’Connor, recommended that the shuttle mission should be delayed due to continued fears over the shedding of the insulation foam that covers the shuttle’s external fuel tanks.

Falling insulation foam was responsible for the damage to the shuttle’s heat resistant panels, which led to the burning up of the shuttle Columbia in February 2003, with all seven crew members on board. Messrs. Scolese and O’Connor were overruled by the other 23 members of the Discovery team and NASA is insistent that the journey to deliver supplies to the International Space Station is safe.

“We do not foresee any problems,” a spokesman for NASA’s Space Shuttle and International Space Station, Allard Beutel, told The New York Sun.

However, the safety concerns raised by two such prominent members of NASA do not suggest that the cause of the break up of Columbia have been satisfactorily overcome.

The Columbia disaster was caused by a piece of foam weighing only 0.8 kilograms, which peeled off from the external tanks and punctured the edge of the wing on takeoff, allowing hot gases to penetrate the wing’s interior. This led to the shuttle breaking apart under the intense heat of the re-entry into Earth 16 days later, killing all seven crew members.

In 2005, in the only shuttle flight since the Columbia inferno, a similar incident took place when a 0.4 kilogram piece of foam broke free from the external tanks of the shuttle Discovery. In that instance the piece flew past the shuttle without striking it.

Since these two missions, design and engineering efforts have gone into reducing the amount of foam pieces shed. Despite all efforts, however, between 56 and 99 grams of foam are expected to be shed during a launch, which, the two dissenting members of the team believe could be fatally hazardous.

“We both feel that there remain issues with the orbiter. There is the potential that foam may come off at the time of launch. That’s why we feel we should redesign the ice/frost ramps before we fly this mission,” said Messrs. Scolese and O’Connor.

However, they are said to have “understood the rationale for the mission to go ahead” and so “do not object” to the decision, according to Mr. Beutel.

Even if the foam peels off the external tanks, various “contingency plans that were not available before” have been put in place so that there is “no risk to any of the seven crew members,” Mr. Beutel said. Yesterday, Messrs. Scolese and O’Connor said they also believe that the “crew can safely return from this mission.”

Cameras both on earth and on the shuttle will monitor the external fuel tanks for falling foam during the launch.

If the shuttle’s wings become irreparably damaged, the crew would be able to “stay on the space station” until a rescue mission could be arranged to bring them down to Earth, Mr. Beutel said.

Mr. Beutel said the primary purpose of the July 1 mission is “to make progress in safety improvements” before the shuttle’s retirement in 2010. NASA aims to finish the ISS by sending 16 more missions in the next four years. Another is scheduled for late August.