London — The Reagan administration's ''star wars'' project is ''a hoax, an expensive hoax.'' That is the opinion of King's College Professor of War Studies Lawrence Freedman.
His judgment expresses the West European consensus. Professor Freedman claims it also represents the prevailing view among American specialists.
One litmus test of attitudes was a recent vote by NATO parliamentarians. Meeting in Brussels, they pointedly urged Ronald Reagan to use his new electoral mandate not to promote his ''star wars'' project but to negotiate a superpower ban on space weapons.
Another litmus test was the September conference of the International Institute for Strategic Studies. There, those Americans who are ''star wars'' enthusiasts conspicuously failed to convince the Europeans of the virtues of the concept.
European resistance to the ''Strategic Defense Initiative,'' or SDI, is passive rather than active at this point.
True, there was a spontaneous burst of criticism of it from West German Defense Minister Manfred Worner last April. And both Britain and France have made clear to Washington their fears that any effective superpower missile defense would reduce deterrence of war in Europe by rendering British and French missiles (and American Euromissiles) obsolete.
Nonetheless, the Europeans realize SDI is still so futuristic that any decisions to proceed from research to prototype construction await some unknown successor to Mr. Reagan. They have adopted wait-and-see tactics rather than expending their limited political capital in a purely theoretical cause.
Professor Freedman's dismissal of SDI is based partly on the increased European vulnerability that European governments fear. In an interview, he pointed out that if a ''star wars'' defense against missiles were in fact feasible for the superpowers, it might just make Europe more open to conventional war.
A superpowers' ''star wars'' defense system would amount to a declaration of no first use of nuclear weapons - something NATO has strongly resisted until now because of its dependence on the threat of nuclear retaliation to deter any attack by superior Soviet-bloc conventional forces.
Freedman also warns against the dangers of increased instability and nervous trigger fingers in time of crisis, should SDI look to be getting workable. But since he is persuaded that SDI is pie in the sky, he concentrates for now on demonstrating the improbability of SDI's ever working as originally conceived.
Thus, Freedman argues that the original aim of SDI is simply not within reach technologically. A recent Rand think-tank study that is otherwise open to the potential of SDI is said to conclude that the exchange ratios between offensive missiles and defensive interceptors does not favor the defense under any conceivable scenario.
The acceptance of this stubborn fact by most of the American hard-liners who were predisposed to favor SDI, Freedman contends, is measured in the steady reduction of SDI goals since Reagan first launched his summons to scientists to find ''the means of rendering . . . nuclear weapons impotent and obsolete.''
In his famous March 1983 speech, Reagan called for a kind of astrodome that would finally protect civilians as well as weapons, would permit real defense and not just retaliation in kind, and would reverse the whole nuclear-age superiority of offense over defense. The present ''balance of terror,'' resulting from the invulnerability of weapons and the vulnerability of populations, would be ended.
Secretary of Defense Caspar Wein-berger seconded this appeal by describing Reagan's vision of defense as one that would be ''thoroughly reliable and total.''
But since Reagan's speech the notion of protecting civilians has all but vanished from administration rhetoric, Freedman notes. The Scowcroft commission report concluded that ''applications of current technology offer no real promise of being able to defend the United States against massive nuclear attack in this century.'' The commission approved a continued research program only to guard against any future Soviet ''breakout'' from the restraints of the 1972 antiballistic missile arms control treaty.
Moreover, Freedman continues, subsequent administration statements about SDI have reverted to the much less revolutionary rationales for military programs that preceded Reagan's speech.
In them, SDI is cast in terms of responding to Soviet research rather than pioneering a new nuclear regime. And population defense has become a poor second to the old objective of defense of American nuclear weapons against a Soviet first strike.
Thus, Weinberger said last May that ''SDI does not preclude any intermediate deployment that could provide, among other things, defense of offensive deterrent forces.'' Lt. Gen. James Abraham-son, the SDI director, explained at the same time, ''My specific charge is to ensure (against possible) breakout of the Anti-Ballistic Missile Treaty on the part of the Russians.''
Similarly, in his National Security Decision Directive a year ago the President set more cautious goals in asking only for ''initiation of a focused program to demonstrate the technical feasibility of enhancing deterrence . . . through greater reliance on defensive technology.''
Freedman bases his characterization of SDI as ''expensive'' as well as a ''hoax'' on such estimates as that of Richard DeLauer, undersecretary of defense for research and engineering. In congressional hearings in November 1983, Mr. DeLauer projected a $400 billion to $450 billion price tag, or some 14 percent of the defense budget, for 10 years of deployment. This, Freedman stresses, would be in addition to the $400 billion to $450 billion spent on current nuclear weapons. It does not include any cost overruns.
Furthermore, it does not include the necessary parallel costs of building extensive defenses against bombers and cruise missiles. Previously the US has not had to build defenses against planes simply because missiles outdated air attack. Any neutralization of ballistic missiles, however, would leave cruise missiles and planes as the most threatening weapons and would require a shield against them.