The National Aeronautics and Space Administration said yesterday it would need at least $270 million - and possibly as much as $600 million - to pay for cost increases and delays in the development and production of the space shuttle.

The space shuttle overrun, the largest single cost increase in the program since its approval in 1971, would bring the cost of developing the spacecraft to almost $8 billion. The original development cost for the spacecraft, which will take off like a rocket and return to earth like an airplane, was $6.6 billion, taking inflation into account.

"It is no single major item that's doing this, it's an accumulation of things coming together," NASA administrator Robert A. Frosch told the Senate subcommittee on science, technology and space. "But we are out of reserves and must begin to reallocate funds if we're to keep to our schedules."

Frosch conceded that even the flight schedule of the shuttle probably will be changed. He said that unanticipated production problems with the plastic tiles that serve as a surface heat shield for the glider-like shuttle could delay the craft's maiden voyage, now planned for Nov. 9.

"While there is a possibility that the first flight could be launched in late 1979, the first quarter of 1980 is more probable," Frosch said. "We can tell more precisely in four to six weeks, when we have a clearer idea of what our added costs will be."

"What's happened?" asked Sen. Adlai E. Stevenson (D-Ill.), chairman of the subcommittee. "I cannot understand how only two months ago you couldn't have foreseen this situation. This says something to me about NASA's ability to manage this system."

Frosch said it became clear to NASA only in the last month that delays in getting the first two shuttlecraft to Florida's Kennedy Space Center and delays in producing the heat shield material would delay flight scheduling.

"When we got the orbiters (the shuttle spacecraft without its engines) to Kennedy we could see what it needed," Frosch said. "A lot of things were coming together in this final push."

The space agency has produced two shuttle spacecraft, both of which were flown to their launch site at Cape Canaveral, Fla., in the last two months. One is named Enterprise, the other Columbia. Columbia will make the first orbital flight; Enterprise will serve as a test spacecraft before the first flight.

Frosch told the Senate panel that the production plant at Palmdale, Calif., where the heat shield plastic tiles are produced, is still not making the tiles at the expected rate of 650 a month. That production rate is needed to fill shuttle flight needs, because the tiles will be burned off the spacecraft in the heat of reentry and will need to be replaced after each flight.

Because it is "dubious" whether production can be stepped up at Palmdale, Frosch said, NASA's solution will be to shift some production to the Kennedy Space Center.This will mean adding about 300 employes to the shuttle payroll and as much as four to six weeks to development time.

Frosch said the delays would add about $70 million to shuttle costs this year and $200 million next year. He said it was the space agency's choice to "relocate" this out of production funds from fiscal 1979 and 1980 appropriations rather than ask for supplemental funds.

The space agency has already made a $185 million supplemental request for this year to pay for delays in the testing of the liquid hydrogen engine that will power the shuttle into space. The request has not been approved by Congress.

Reallocating $270 million from production funds would mean the space agency would have to delay production of its third orbiter and possibly its fourth and fifth ones. Frosch said this could mean added production costs of between $300 million and $400 million in 1981 and 1982 due to inflation.