Space shuttle Endeavour returns safely to Earth

Double-sonic booms rang through the balmy night as the spaceship dropped beneath the sound barrier for first time since its predawn blastoff from the Kennedy Space Center on Feb. 8.

Minutes later, Endeavour commander George Zamka gently settled the 100-ton spaceship onto a canal-lined runway at 10:20 pm EST (0320 GMT), bringing NASA's 130th space shuttle mission to an end.

Four flights remain before NASA retires its three-ship fleet later this year.

Endeavour and its crew spent nearly 10 days at the space station to deliver and install the last connecting hub and a seven-windowed observation deck, completing major assembly tasks for the US-portion of the orbital outpost.

The crew conducted three spacewalks to hook up cooling lines and prepare the new rooms for use.

The space station, a $100 billion project of 16 nations, has been under construction since 1998.

In addition to Zamka, the Endeavour crew included pilot Terry Virts, flight engineer Stephen Robinson, spacewalkers Robert Behnken and Nicholas Patrick and mission specialist Kay Hire.

NASA was investigating a series of computer crashes aboard the space station. The problem did not impact any life support systems, the agency said.

Preliminary analysis indicated the computer glitches may stem from problems with communications software in the European Space Agency's Columbus laboratory, astronaut Stan Love from Mission Control told the station crew.

The crashes temporarily knocked out the crew's audio and television links with Mission Control in Houston.

With shuttle missions ending due to safety concerns and high operating costs, it will be left to Russian, European and Japanese cargo ships to keep the space station resupplied. But none have the lift capacity of the shuttle.

NASA already has turned over crew transport to Russia and plans to invest $6 billion in the next five years in commercial U.S. firms, hoping to spark development of orbital passenger spaceflight services.