Washington — The Pentagon may face a traumatic budget crunch in the 1990s when many expensive weapons now being developed are ready to enter service, according to many defense analysts. Reagan administration officials say procurement goals for the foreseeable future can be met with modest increases in military spending. But analysts inside and outside the Pentagon say Congress is in no mood to increase the defense budget, and that as a result plans for new submarines, aircraft carriers, and fighter planes may be thrown into chaos in coming years.
Pentagon planners ``are totally underestimating the amount of money they would really need to buy all these things,'' says Gordon Adams, director of the Defense Budget Project, a private research group.
Money for purchase of new weapons would actually shrink slightly to $84 billion in 1988, under the administration's budget proposal. But the Pentagon projects that it would turn up sharply in the years thereafter, increasing 9.4 percent after inflation in 1989, and 8.7 percent in 1990.
These increases would reflect the move of a number of new major weapons to the assembly line. The Navy, for instance, plans to request $1.4 billion in 1989 for the first of its new Seawolf-class attack subs, and $1 billion-plus in 1990 for primary funding of a new aircraft carrier.
At least two new jets - an Air Force fighter, and a Navy attack plane - will be growing fast in program cost around the turn of the decade, as will the Army's LHX light helicopter and a tilt-rotor aircraft.
The Stealth bomber will probably be in production by then, though actual prospects for this are classified. The Air Force will also be getting ready to order the Midgetman intercontinental ballistic missile and the air-to-surface nuclear missile.
Currently the Defense Department projects that it will need 3 percent annual real growth through 1992 to buy all these weapons and pay for everything else the military needs. Defense Secretary Caspar Weinberger, in a recent meeting with reporters, said ``there is nothing special about the 1990s'' and that the US unfortunately requires expensive weapons to protect against the Soviet threat.
Other officials says they believe the Pentagon won't get 3 percent annual increases and should start planning now for the hard choices getting less will entail. Army Undersecretary James Ambrose, in a speech to contractors earlier this year, warned that to finish its modernization program the Army needs $100 billion more than Congress is likely to provide.
A recent Congressional Budget Office report came to a similar conclusion, warning that to maintain or improve current levels of readiness, buy all its planned new weapons, and not shrink manpower, the Army would need annual real increases around 6 percent.
Lawrence J. Korb, an assistant defense secretary from 1981 to '85, says that all the new weapon starts in the budget were begun in flush times when big annual budget increases seemed assured. He worries that with lean times ahead, the military will slice funds for such mundane but crucial items as fuel, ammunition, and spare parts, rather than go without its cherished new weapons.
One way to avoid hollow forces that have weapons but no way to maintain them, Mr. Korb says, would be to scale back the size of the military.
``The Navy ought to have 550 ships, instead of 600,'' he says. ``The Army could be 15 divisions instead of 17.''
There are some indications crucial sustainability funds are already being slighted in the name of new force structure. Adm. Ronald Hays, commander of US Pacific forces, testified before Congress this week that his ships are now short of ammunition and spare parts.
``Staying power remains a serious conventional war-fighting concern,'' Admiral Hays said.
Critics point out that meanwhile the Navy is forging ahead with its plans to maintain 15 aircraft carriers at sea, with seed money for two new carriers requested in the 1988 budget.
Under budget pressure, the services save more money in the short term by attacking operation and maintenance accounts than by trimming new weapons. This anomaly is caused by the fact that weapons take time to build.
Though Congress authorizes money for a new destroyer, for instance, in one year, funds are actually spent only as work on the ship progresses. And it is only these actual outlays that count against the federal deficit.
From the point of view of Congress and Pentagon planners, it's as if they decide not to buy an automobile but only get credit for not making that year's car loan payments.
It's easier to go after other accounts such as spare parts, where the full savings is chalked up to deficit savings immediately.