Every time a space shuttle goes up, its fuel tank costing tens of millions of dollars breaks into little pieces and falls into the ocean. Now, NASA and a group of universities are teaming up to stop the waste.

The space agency and the University Corporation for Atmospheric Research announced an agreement Thursday to make scientific use of the tanks once the shuttle is in orbit.The fuel tanks, which cost $34 million each, are the only part of the shuttle system that is not reused. The orbiter goes up like a rocket and comes down like an airplane; the two booster rockets are retrieved by waiting ships and towed back into port for refurbishment.

The NASA-UCAR agreement calls for placing experiments and equipment into five selected shuttle tanks, probably beginning in 1991. The experiments will be placed on a pallet in an unpressurized 5,000-cubic-foot area between the inner fuel and oxidizer tanks.

"We are not costing the taxpayer one bit," said Peter Riva, an adviser to the university group. "We are reimbursing NASA for all costs."

The group, a consortium of 58 universities and research institutions involved in atmospheric and space science research, eventually hopes to use the spent tanks in orbit. The experiments on the first five will be conducted on suborbital flights - in the minutes after the tanks are released from the orbiter and fall back through the atmosphere into the Indian Ocean.

"All that high-density aluminum is being discarded," Riva said. "It is a far better idea to leave them in orbit to use now or eventually as platforms and habitats and all sorts of things in space."

The National Aeronautics and Space Administration uses a small explosive device to start the tanks tumbling after release - so they will break into small pieces that burn up in the atmosphere.

The first experiments will aim at controlling the tanks during their fall. "That's crucial to us," Riva said. "We will put on board some small form of rocket controlled from the ground and try preliminary roll and yaw experiments on the external tank."

Other experiments will measure the density of the atmosphere and release gases at high altitude to measure their effect - a step toward monitoring the decay of the environment.

Riva said the consortium envisions a budget of $500 million and will try to recoup some of that by renting space on the pallet to other experiments. No operational changes will be made in the shuttle operations and no timetable for flights has been set.

"We are not going to cause a single hiccup in NASA's normal shuttle operation," Riva said.

NASA said several organizations have proposed private uses for the tanks and that evaluation of the proposals continues.

The 154-foot-long external tank holds the nearly 1.6 million pounds of Liquid oxygen and liquid hydrogen fuel that is required to power the shuttle to orbit.

The intertank area measures about 22 feet by 28 feet and weighs 12,100 pounds.