Preparations for Shuttle Flight Proceed Smoothly : Space: Columbia’s mission is scheduled to begin with launch early Monday. Crew of seven includes two German scientists.

Delayed for a month by technical problems, the space shuttle Columbia proceeded smoothly through launch preparations Saturday with the 55th mission for the U.S. space fleet set for launch at 6:51 a.m. PST on Monday.

Officials at NASA’s Kennedy Space Center in Florida said the countdown was proceeding without a hitch, and weather forecasters put the chances of acceptable launch conditions Monday morning at 70%.

Carrying a crew of seven, including two German specialists who will carry out experiments inside a 12-ton laboratory nestled in the cargo bay, the shuttle is to circle the Earth for nine days.

If the launch goes as planned, a landing back in Florida would be scheduled for the early morning of March 31.

During the intervening days, crew members will conduct about 90 experiments in the $1-billion spacelab, designed and constructed by the European Space Agency.

The work will focus on medical and biological investigations, although the astronauts also have assignments to make extensive observations of the Earth and astronomical objects.

As in other recent missions, flight planners designed assignments to gather experience and information needed in construction of a space station--now being redesigned into something much more modest than the $31-billion laboratory and habitat long planned by the United States and international partners.

The spacelab experiments are designed to advance the understanding of what happens to materials and organisms when the effects of gravity are taken away.

Test subjects scheduled to be placed aboard the laboratory today include tadpoles and perch larvae. It is hoped that they will provide new information on how balance-sensing organs function in space and perhaps offer clues into the “space sickness” that has troubled many astronauts over the years.

The European laboratory was taken into orbit on a similar mission in 1985. Last year, a spacelab mission was flown in collaboration with Japanese scientists.

Once in orbit, the laboratory will be occupied around the clock, with the astronauts divided into work shifts.

While the flight crew will be under the direction of the National Aeronautics and Space Administration, by way of its Johnson Space Center outside Houston, activity within the spacelab will be the responsibility of the German Space Operations Center outside Munich.

Both German members of the crew, Ulrich Walter, 38, and Hans William Schlegel, 41, will be making their first space flight.

The mission will be commanded by Steven R. Nagel, a 47-year-old Air Force colonel making his fourth flight, with Terence T. Henricks, 41, as shuttle pilot.

U.S. mission specialists taking part in work aboard the spacelab are Jerry Ross, 45, Charles J. Precourt, 37, and Bernard A. Harris Jr., 36.

Originally set for launch in late February, the flight was at first delayed when confused record-keeping made it unclear whether the correct pumps had been installed in the shuttle’s propulsion system.

Later, a problem developed with a hydraulic hose between the shuttle and its huge external fuel tank.

Because of the delay, NASA’s schedule now calls for the shuttle Discovery to be launched just a week after Columbia returns.