The Soviet Union's future was foretold yesterday when an elderly economic and industrial manager who owes his allegiance to Leonid Brezhnev was installed as head of the Soviet government.

The elevation of Nikolai A. Tikhonov to premier succeeding ailing Alexei N. Kosygin carries many messages into the new decade of the 1980s, but the principal one seems clear: long after Brezhnev eventually leaves the Kremlin for good, his era will linger on.

Tikhonov is quintessentialy a Brezhnev man, a hardened technocrat whose known views do not detectibly diverge one millimeter from his patron's.This clone-like similarity is the result of a vigorous and continuous process of weeding out over the years younger men of ambition who sought distance or independence from the Brezhnev way of doing things.

[The Tass news agency said today that Brezhnev had sent a message to Kosygin expressing "cordial gratitude" of the Politburo and the Soviet government "for his considerable and fruitful work over many years which he carried out in high posts in the party and the Soviet government," Reuter reported.]

[The absence of praise for Kosygin when Brezhnev announced the premier's letter of resignation yesterday had led to speculation about possible transition difficulties.]

Kremlin-watchers' notebooks are filled with the names of these figures of former times: Shelest, Shelepin, Polyanski, Mazurov, Katushev. All have been discarded.

Unlike Kosygin, known as mayor of Leningrad and a Politburo member with important responsibilities long before he became premier in 1964, Tikhonoy's own power base is sharply restricted by his public obscurity and minority Ukrainian nationality.

Although the country faces a decade of deepening economic problems -- energy, manpower, and food shortages, slackening replacement and renewal of aging industries, workplace inefficiency and disorder -- the 75-year-old Tikhonov has pledged absolute fealty to the cumbersome party-dominated economic system that Brezhnev strengthened throught his 16-year reign at the expense of Kosygin and other reformers. Even if the new premier harbors separate views, the grip of Brezhnev's allies at the top is so tight and complete, he could never mount an effective attempt for significant change in the way things are done.

No less than 11 of the present 14 Politburo members were brought into the top circle after Brezhnev and Kosygin took over in 1964 from Khrushchev. Of these 11, all but one, 81-year old Arvid Pelshe, a Latvian, were appointed in the 1970s, when Brezhnev had eclipsed Kosygin and become undisputed Soviet leader.

Kosygin's retirement leaves only Mikhail Suslov, Andrei Kirilenko, and Brezhnev himself as holdovers from the pre-Brexhnev years, and both Suslov and Kirilenko are closely identified with the party chief.

This analysis points to part of the truth of the Brezhnev era: that while the inner leadership circle is distinguished by its advanced age, there has been a steady if less noticeable process of renewal and replacement as Brezhnev experimented and found the combination of colleagues most congenial to his conservative ways. The implication is that his views will be perpetuated after he has gone, and the Tikhonov choice reinforces this dispite the new premier's age.

Soviet sources have made clear that the Afghanistan invasion of last December and the management of that crisis since has fallen chiefly on the shoulders of an "inner four" of KGB chief Yuri Andropov, Defense Minister Dmitri Ustinov, Foreign Minister Andrei Gromyko, and Kirilenko, with Brezhnev's personal aide, Konstantin Chernenko, and candidate Politburo member Boris Ponomarev, together with hardline ideologue Suslov as lesser participants. Final decisions rest with Brezhnev.

Thus, foreign analysts here look for Brezhnev's successor to come from that group. Kirilenko, like other Politburo members a man who has had Brezhnev's confidence for more than four decades from their days in the Dniepropetrovsk region before the war, has always been thought to hold the inside track as immediate successor to party chief.

With Suslov, who will be 78 next month, Brezhnev has evolved a style of shifting his closest consultations among his colleagues to keep them divided and jealous. Now, an informed source suggests, he is paying close attention to Chernenko, 69, instead of Kirilenko, 74. "Kirilenko isn't getting the invitations now and Chernenko is," said this source. "Running the party is a war and requires great energy. Kirilenko doesn't have it anymore."

Even so, the older man is widely known to the cadres who run the party from the regional level up, and Chernenko, a full Politburo member only two years, is thought to be a long shot.

Gromyko, 71, is indispensible to running Soviet foreign policy, which he has done since 1957. Ustinov, 72 next Thursday, has been ill in recent years and is deeply engaged in the Afghan crisis.

This leaves Andropov, 66, who first made his mark as Soviet envoy to Hungary in 1956 when he helped crush the Hungarian revolution. Ever since Stalin's Great Terror, the secret police chief has automatically been ruled out as party chief. But East Germany's Erich Honecker and Poland's Stanislaw Kania once headed their countries' secret police, and at a time of internal strain here, the party might applaude a similar choice.

Some analysts rate Andropov a closet liberal, intellectually superior to many of his colleagues. Aside from some 1970s statements supporting detente, there is not much solid evidence that the bespectacle security man is anything other than a cautious and clever Brezhnev loyalist.

Farther afield are several senior officials, some with a wealth of experience in party affairs, industry, or administration.

In probable descending order of likely chances to a top post are Moscow party chief Viktor Grishin, Leningrad party chief Grigori Romanov, Ukrainian party chief Vladimir Shcherbitsky and Kazakh leader Dinmukhamed Kunayev. But regionalism or nationality hurt their chances. Pelshe is too old and agricultural chief Mikhail Gorbachov, a promising new face raised to the Politburo Tuesday, is simply too new to the leadership.

The power equation in the Brezhnev Kremlin ultimately turns on these distances from the center. A tiny group of men who have worked together for years makes all significant decisions and all other men are excluded. The impacted resistance to change, which works against all these outsiders, works against the system as well, bottling up talent, squandering youth, denying experience, cashiering the adventurous.

But as the choice of Tikhonov as premier shows, this is a price the Brezhnev Politburo is willing to pay -- for years to come.