In about six weeks the United States' eighth space shuttle will drop out of a night sky so dark the plummeting craft will not be visible to the naked eye until it is 50 to 80 feet above its dry lake bed landing strip in the desert at Edwards Air Force Base, Calif.

The flight of the Challenger, the first involving a fiery night launch from Cape Canaveral and then an eerie night landing five days later in the Mojave Desert, will be the most visually spectacular in space program history.

The Mojave will be lit up like a birthday cake for Challenger, with lights of 8 million candlepower leading her in. But to those on the ground the spacecraft will emerge from space like a Hollywood sci-fi vision seconds before touchdown.

But, in a preflight news conference by Challenger's five crewmen today, spacecraft commander Richard H. Truly said success of previous shuttle flights has made space travel routine enough that the landing will be "easier" than a night landing on an aircraft carrier.

The eighth shuttle flight also will place the first American black astronaut in space, breaking a color barrier just one flight after NASA broke a 20-year barrier of another kind by placing the first American woman, Sally K. Ride, in orbit.

Guion S. Bluford Jr., 40, a Philadelphia native and former Vietnam fighter pilot, was nonchalant about his role, saying he recognizes "the historical significance," but noting that he feels "no added pressure" because of the limelight about to be thrust upon him.

Bluford will fly as a mission specialist, whose primary responsibility is deployment of a satellite.

Others aboard will be pilot Daniel C. Brandenstein and mission specialists Dale A. Gardner and Dr. William Thornton, 54, a physcician.

The flight will feature the in-space launching of an Indian government communications satellite, whose positioning requires the night launch and landing. The astronauts also will test a 7,460-pound Canadian-built mechanical arm, take aboard 1,000 pounds of U.S. Postal Service special issue stamps and conduct medical experiments.