Europe is waking up to America's ''star wars'' plans - with a shudder. The West Germans are among the most outspoken in voicing anxieties about Reagan administration proposals for weapons in space. But their view is widely shared in European defense ministries.
Karsten Voigt, spokesman on security affairs for the opposition Social Democrats, has been especially blunt. If the United States develops satellite and missile killers in space, he warns, the storm of US-European argument that will break out will make the recent NATO debate over Euromissiles seem like a spring breeze.
So far government spokesmen in West Germany have been more tactful. But Defense Minister Manfred Worner - an advocate of Western military strength in the Reagan mold - says the same thing in more guarded language.
So does Franz Josef Strauss, the head of the West German conservatives' right wing, the Christian Social Union, and an anticommunist of the first water.
What brings these otherwise divergent politicians together is a conviction that the Reagan administration's plans for space-based weapons would harm the West more than the Soviet Union - and fatally decouple West European from American defense.
What is surprising is less the vehemence of the current West German reaction than the time it has taken to develop. Mr. Reagan presented his goal of antisatellite and antimissile weapons in space a year ago.
And a Pentagon team toured Europe in February to give secret brief-ings to allied governments on the ''strategic defense initiative,'' as the program has been christened. Both times around the West German reaction was nil.
What seems to have triggered West German alarm is the explanation of the space weapons project that US Defense Secretary Caspar Weinberger gave the NATO nuclear planning group when it met in Turkey this month. There West German Defense Ministry officials voiced their concern for the first time.
Dr. Worner followed up by telling the Hannover Allgemeine Zeitung last Sunday that a US antimissile system could destabilize the East-West balance, ''decouple'' the US and Western Europe, and even lead to a splitting apart of the Western alliance.
The West German reasoning runs this way:
With its technological exuberance, the US can no doubt seize a temporary lead over the USSR - perhaps five years' worth - in militarizing space. But Moscow will always catch up with Washington eventually.
And once both superpowers' satellites become vulnerable, the US will be the far greater loser, since it is far more dependent on satellites for essential military communication, positioning, surveillance, and targeting.
Therefore, the West Germans say, it would be to the West's advantage to negotiate a ban on antisatellite weapons now before both sides develop such capability. Such a ban could still be verified, since neither superpower has yet developed a high-orbit antisatellite weapon (and the most crucial American satellites are in geosynchronous orbit well above the range that today's crude Soviet and US antisatellite weapons can reach). But once a high-orbit weapon has been tested, verification of a ban would be extremely difficult.
The West German fears about development of a space-based antimissile laser weapon also assume Moscow will quickly imitate whatever technology Washington pioneers.
The West Germans don't see as much direct disadvantage for the US in an eventual American-Soviet antimissile regime as in any American-Soviet antisatellite regime. But they do see an ominous disadvantage for Western Europe.
That would arise from what the West Germans regard as an inevitable two-class system of defense (assuming the antimissile shield actually works). The superpowers would be protected against each other's intercontinental missiles, whose half-hour flight times and high trajectories would permit interception.
But Western Europe would not be protected against the 10-minute flights of Soviet SS-20s or the even faster flights of short-range Soviet missiles stationed in East Germany.
Under such circumstances the US would no longer be able to threaten retaliation on the USSR for any Soviet attack on Western Europe. The postwar American nuclear guarantee of Western European security would no longer be credible. Europe and the US would become ''decoupled'': that is, the US would be safe, while Europe would be vulnerable.