The House is scheduled to take up a record-high defense bill today that could commit the lawmakers to an even larger amount next year, when political and economic conditions could be strikingly different.

The commitment is in the form of big down payments on weaponry not scheduled to be authorized formally until next year or later. These down payments are part of the $136 billion the House Armed Services Committee is recommending in fiscal 1982 dollars to design, build and maintain weapons, on a peacetime high.

The strategy behind the downpayment approach may be to get money for defense out of Congress while the getting is good. Defense money may be harder to come by as the backlash against domestic cuts bites harder.

Although providing advance money for weapons in an authorization bill is not new, the measure coming before the House today is unusually generous.

For example, it earmarks a $658 million down payment on another Nimitz-class nuclear-powered aircraft carrier the Navy does not intend to build until fiscal 1984. The bill also provides for a down payment of $100 million on a $1 billion helicopter carrier the Navy did not request.

Assuming that the down payments are authorized, opponents of this course are likely to encounter the argument that it is too late to call off the ships' construction when it comes time to authorize the rest of the money for them.

Navy leaders welcome the downpayment approach, because it is easier to obtain money for super weapons in installments rather than in a single year's budget. The Reagan administration is seeking to level out the highs and lows of defense contracting through what it calls a "multi-year" procedure of providing for weapons over several budgets.

The House also is being asked, through a $100 million down payment, to commit itself to buying another $1 billion CG47 Aegis-class anti-aircraft cruiser in 1973.It would be in addition to the three authorized for fiscal 1982.

Besides welcoming these and other down payments on expensive weapons systems, which take from eight to 10 years to produce, Navy leaders see the bill as a mandate for building bigger and better ships rather than smaller and cheaper ones, as Sen. Gary Hart (D-Colo.) and others have advocated.

The Navy has mapped out an ambitious shipbuilding program for the five-year period 1983-1987. It calls for spending $100 billion, after allowing for inflation, on 145 ships over those five years.

They include one Nimitz-class carrier to be built in 1984 and a second in 1986.

In fiscal 1983 alone, the Navy proposes to build 20 ships, including one $1.5 billion Trident missile submarine, three $1 billion Aegis cruisers, three $500 million SSN688 nuclear attack submarines and one $350 million LSD41 assault ship.

The Navy has proposed ambitious shipbuilding programs in the past, only to see them reduced by civilian superiors because there was not enough defense money to go around.

But this year there is a high degree of optimism within the Navy that Congress will be generous and provide the money for the $100 billion shipbuilding effort.