Hidden in the fine print of President Reagan's defense budget is a catalog of new weapons that could keep Defense Department spending rising well into the 1990s.

The "new starts" in the small print of the fiscal 1987 budget include a $30 billion family of helicopters for the Army, $1 billion submarines and destroyers for the Navy and bombers costing $300 million or more for the Air Force.

Also included are some items that could balloon into multibillion-dollar programs in the next decade. These sleepers include a newfangled plane and a dirigible to direct fire from the ground and sea to distant targets and a variety of "black" programs that the Pentagon lists in its weapons catalog but does not describe.

One such black program is called Chalk Pine. Its funding is scheduled to leap from $43.7 million this year to $115 million in 1987. "Classified," the Navy responded, when asked the program's ultimate cost.

On top of these starts in the fine print are costly ones spotlighted by the president and likely to pile up big bills in the 1990s, including his five-year, $30 billion effort to develop a "Star Wars" missile defense and a $2 billion down payment on a space plane, dubbed the Orient Express because of its promise to carry people to the Far East in two hours. Also, the Pentagon is asking for money to start new fighter plane programs for the Air Force and Navy.

The new starts, if approved by Congress in the coming months, will allow the Pentagon to order the weaponry now and pay later. The Pentagon charge account for this purpose is called budget authority. Only when the charges are paid do they show up as outlays in the defense budget.

The Defense Department has put so many weapons on its charge account that it will be paying for them long after Reagan leaves office, no matter what Congress decides about this new military budget. To lower future military spending, a wide spectrum of lawmakers agree, Congress will have to find ways to save money on existing programs as well as nip some of the proposed starts.

In the first round of congressional hearings on the military budget, Democrats and Republicans urged Defense Secretary Caspar W. Weinberger to set priorities, make choices and get more out of each buck. Sen. Sam Nunn (D-Ga.), who favors increased defense spending, was among lawmakers warning that there is not enough money in sight to keep funding old programs while launching new ones.

Weinberger stood fast, declaring the Soviet threat too menacing to allow cuts below the amounts Reagan has requested: Fiscal 1987 budget authority of $320.4 billion, 12 percent higher than the $286.1 billion Congress approved for the current year (or 8 percent after inflation), and $282.2 billion in actual spending compared to $265.8 billion for fiscal 1986.

But a new study by the Congressional Budget Office looks to some politicians as a way to cut the Pentagon budget without looking soft on defense. If Congress delayed or severed some of the new starts and used the savings to increase production of existing planes and missiles, a larger number of weapons could be sent to the field years sooner and at less cost, the CBO study found.

By delaying research or production on 10 weapons, the CBO said, $48.6 billion could be saved in the five years starting in fiscal 1987.

The CBO said in its exercise that it applied some of the $48.6 billion to increase production of 19 weapons and realized a net savings of $32 billion, partly because individual weapons dropped in price when they were produced in a shorter period.

Efficient production rates, or EPR, has sudden appeal on Capitol Hill, especially among Democrats. "You're going to be hearing a lot about EPR from now on," said one congressional staff member familiar with the CBO study and involved in designing a new Democratic political strategy on defense. But to help trim the federal deficit through EPR, Democratic strategists said, Congress must freeze, postpone or nip some of the new military programs on the verge of ballooning.

Each branch of the military provides big targets, congressional aides said. They include, with the CBO's assessments, the following:

*The Army's new light helicopter (LHX) program. Reagan's research budget shows one advanced technology account for the LHX family jumping from zero in fiscal 1987 to $194 million in fiscal 1988. The idea is to use the same engine and airframe to build helicopters for a variety of missions, including light transport, attack and observation. Army Undersecretary James R. Ambrose has said the LHX could cost $30 billion for 5,000 to 6,000 aircraft, with the first off the production line in the early 1990s.

If LHX and other new programs were postponed, the CBO said, the Army could afford to increase the production of its UH60 troop helicopter from the planned 78 per year to 126 annually.

Big savings also could be made if the Army's Hellfire helicopter-launched antitank and Stinger antiaircraft missiles were produced at a higher rate, the CBO said.

*The Navy's SSN21 nuclear-powered attack submarines. The budget calls for almost tripling -- from $255 million in fiscal 1986 to $712 million in fiscal 1987 -- funding to start on the new fleet of subs, which are expected to cost about $1 billion each. The Navy wants 100 attack subs, so an all-SSN21 fleet would cost $100 billion.

*The Navy's Arleigh Burke class of destroyers. Reagan is requesting $2.65 billion in fiscal 1987 for three of the DDG51 destroyers, or $882 million each. Former deputy defense secretary Paul Thayer considered the cost excessive and tried to nip the DDG51 program.

*The Navy's V22 Osprey tilt-rotor aircraft (formerly called JVX). Subjected to congressional challenges previously, it is scheduled for full-scale development in fiscal 1987 under a $483 million request. It would replace Navy and Marine CH46 and CH53 helicopters and be used by the Army as a utility transport.

*A reincarnation of the Navy blimp. It would be used this time for guiding ship- and submarine-launched cruise missiles as well as hunting enemy subs, and would get under way in fiscal 1987 with $9.8 million in funding.

The CBO, in projecting potential savings, delayed procurement of the SSN21 submarine and V22 utility transport for three years and increased production of the existing Los Angeles-class attack sub and DDG51 destroyer.

*The Air Force's Stealth bomber program. The Pentagon has made Stealth cost estimates classified information. Defense officials insist the bomber will cost no more than 3 percent above the existing B1, but critics contend the price could end up as high as $80 billion for 132 radar-evasive planes. Whether Stealth costs $40 billion or $80 billion, its biggest bills will come due late in this decade and the early 1990s as production gets under way.

*The Air Force's C17 transport. Reagan wants to increase funds for the plane from $373 million in fiscal 1986 to $830 million in fiscal 1987. The cost is projected to rise to $1.3 billion in fiscal 1988 for the first two planes.

Other Air Force programs looming large on the horizon include the Midgetman mobile missile, an advanced technology fighter plane and JSTARS (Joint Surveillance and Targeting and Attack Radar System) -- a modified transport plane stuffed with electronics to enable a commander above the battlefield to direct fire and deploy forces.

The CBO's projection delayed the C17 and Midgetman for three years while freezing research funds for the advanced tactical fighter.

"New program starts can add to the budgetary pressures that slow down current production," CBO Director Rudolph G. Penner said in the report. "Delaying research and development of new weapons, or initial production of those whose development is nearly complete, is one method of easing budget pressures to allow greater production efficiencies for current programs." CAPTION: Pictures 1 through 3, New wave of weaponry: Army light helicoptor(LHX)-5,000 at $6 million equals $30 billion; Navy attack submarine(SSN 21)- 100 at $1 billion equals $100 billion; Air Force Stealth bomber-132 at $300 mllion to $600 million equals $39.6 billion to $79.2 billion.