President Reagan intends to wire the United States and outer space for extended nuclear war rather than assume any doomsday would be over in hours.

His plan represents the first major attempt by an American president to buy a command net to run a nuclear war after the two superpowers would have fired missiles at each other.

Defense Secretary Caspar W. Weinberger, appearing yesterday on "Face the Nation" (CBS, WDVM), said "the entire system" of U.S. strategic forces "will be far more survivable by improvements in its communications, something that's been hardly noticed in the past few days."

There long have been theoretical arguments that the United States should be able to wage limited as well as all-out nuclear war against a wide variety of targets for days, weeks and even months. Former president Carter last year embraced this theory on paper in Presidential Directive 59.

But Reagan has gone beyond paper to earmark extra billions for what the Pentagon calls "strategic C3" -- the command, control and communications needed to wage nuclear war. The reasoning is that it makes no sense to build an arsenal of bombers and missiles when the enemy could easily knock out the satellites and ground stations for sending them into battle.

The Air Force will take the lead in wiring the land and outer space for doomsday, with its share of the C3 total expected to run between $10 billion and $15 billion for the five-year period beginning in 1983. Defense officials said they recently gave the Air Force the go-ahead for a new set of space cops called IONDS for Integrated Operational Nuclear Detonation System.

IONDS sensors, under Reagan's new strategic blueprint, will be hitched to 18 Navstar navigation satellites the Air Force plans to put in space. Six Navstars already are up there, five of them providing navigation fixes. IONDS gadgetry is supposed to sense the peculiar radiation from nuclear explosions and send information on their size and location to receiving stations on the ground.

These ground stations also are considered weak links in the strategic command, control and communications chain, and under Reagan's plan will be "hardened" against the side effects of nuclear weapons. Some of the communication stations will be placed in trucks so they can be moved quickly out of harm's way.

The IONDS, in combination with survivable ground stations, would not help warn the president of a nuclear attack, but its proponents argue that it would provide him with detailed information about what had happened in the first minutes of doomsday. According to the argument, knowing which Soviet targets had escaped detection and what, if any, forces the United States had left would help surviving leaders decide what to do next.

The Reagan administration made no secret of its intention to prepare for extended nuclear war, declaring in last week's official paper on its new strategic program: "We will initiate a vigorous and comprehensive research and development program leading to a communications and control system that would endure for an extended period beyond the first nuclear attack."

Weinberger refused to be pinned down when asked last week whether he "personally" thought a nuclear war could be won.

Critics of this philosophy contend there can be no such thing as a little nuclear war; that once either superpower fired a nuclear warhead at the other there would be all-out war. They favor building awesome nuclear arsenals, however, to make sure decision-makers in Washington and Moscow continue to regard nuclear war as a losing proposition -- a concept called mutual deterrence.

The idea of trying to seize and hold the military high ground of space also has its detractors. There is no way to make fragile satellites invulnerable to nuclear blasts in space. The better course, they assert, would be to negotiate an agreement to put outer space off limits to warfare.

While pushing ahead with new warning and control systems for outer space, the Reagan plan also calls for expanding the warning net on the ground and hardening against nuclear effects the "Looking Glass" flying command posts that the United States now keep in the air at all times to escape a surprise attack.

As it is now, warning radars in Greenland, Alaska and Britain keep on the watch for Soviet missiles flying at the United States from the north. But these radars would not detect the low-trajectory submarine missiles the Soviet Union could fire from the Atlantic or Pacific oceans.

Two radar warning nets called Pave Paws, one in Massachusetts and the other in California, have this job. But Reagan decided this is not enough protection from Soviet missile submarines, especially given their use of Cuba.

So, as another part of his C3 improvement plan, two more Pave Paw radar stations will be built to tighten the warning net covering the southeast and southwest approaches to the United States. The Pentagon has not disclosed in what states the new Pave Paws will be constructed.

The Reagan administration also promises to improve its communications with submarines patrolling the depths but has so far shied away from revealing its plan for ELF, the extremely long frequency network that the Navy has sought to install in Wisconsin and Michigan.