Japan's space program barely off the ground. . . but already outdated?

Japan's space program is having trouble reaching orbital velocity.

On the positive side, the Japanese National Space Development Agency's rockets currently are performing flawlessly, with some help from the United States. This allows NASDA to go ahead with plans to place a whole series of communications, weather, scientific research, and factory satellites in stationary earth orbit, beginning in the late '80s.

But earthbound problems threaten this ambitious liftoff.

Japan is threatening to take its business away from NASDA to the American space shuttle or even to Europe's Ariane rocket because of unhappiness over both the cost and satellite carrying power of Japanese rockets now in use or on the drawing board.

In fact, there is mounting worry that by the time those in the planning stages are ready for launching they will be out of date.

Faced with these problems, the government's Space Development Council is conducting a full-scale review of its current 15-year program drafted in 1978.

At the same time, the Ministry of International Trade and Industry has announced plans to try to groom the fledgling domestic space industry to the stage where it can take off on its own.

A late starter in space, Japan is now able to launch only a 350-kilogram (770 -pound) satellite into orbit 36,000 kilometers (more than 22,000 miles).

This capability will be thoroughly tested early next year when an experimental communications satellite of the Nippon Telegraph and Telephone Corporation (NTT) will be carried aloft by the latest N-2 rocket.

The orbital cost of this experimental satellite - with a paltry 3,000 telephone circuits - is estimated at $230 million, of which the telecommunications authority is required to contribute just over $100 million.

But NTT doesn't think it is getting its money's worth.

The Science and Technology Agency, which has long been devoted to the development of purely Japanese rockets, has finally managed to produce an H-1 series capable of carrying a 500-kilogram payload.

This is designed for an NTT satellite planned for orbit in 1987, which is due to be followed in the early 1990s by an H-1B series capable of carrying a one-ton payload.

NTT is publicly scornful of this effort.

It has ambitions to develop a nationwide Home Information Network System, which requires the launching of satellites weighing 3 to 4 tons and equipped with up to 250,000 circuits.

NTT's current plan is to launch a 1-ton satellite in 1988 and the far heavier space vehicle around 1992.

The corporation's top executives have been putting heavy pressure on the government to scrap the present program and come up with much more powerful rockets at the earliest possible date.

''We simply can't waste the huge amounts of money poured into rocket development,'' counters a Science and Technology Agency spokesman.

''Anyway, I don't think the shuttle or Ariane are as powerful as NTT is trying to make out.''

NTT, however, says Japan is in danger of being left far behind in space if it continues on its present course.

Either develop more powerful rockets or be realistic and scrap the whole program, saving everyone a lot of money, the corporation is saying privately.

The Liberal Democratic Party, the party in power, is sympathetic. Its space development committee recently drafted a proposal now being considered by the government for not only advancing the development of the H-1 series but also boosting its lifting capacity. While supporting the basic policy of developing domestic technology, however, the committee conceded Japan might have to cut corners and use foreign know-how sometimes.

The Ministry of International Trade and Industry is anxious to see a home-grown space industry develop as there are 70 companies involved with annual gross sales of around $400 million.