Helium. You can't see it. You can't smell. About the only times it affects most people people's lives are when they're concerned about the levitation of balloons.

But helium is quite a different matter to some of the people who extract their livings from the natural gas fields of Texas, Oklahoma, and Kansas.

In a huge underground storage tank near the western border of Texas, the federal government has imprisoned 39 billion cubic feet of helium, enough to launch an armada of 6,000 Good year blimps.

Right now, there is much use for all that helium. It was stored for programs which have largely petered out now; the technologies may demand it in large quantities in the future are only experimental today.

The government has spent more than half a billion dollars to accumulate its stock of helium. And although the Interior Department stopped storing it five years ago, the cost to tax-payers of discontinuing the helium program could be as much at $417 million more.

The helium conservation program is a graphic illustration that what the federal government can turn on with one hand it cannot always turn off with the other.

The helium program was begun at about the same time the age of space missiles and intercontinental nuclear weapons was born. Those technologies brought with them a need for a material with outstanding cooling properties. Helium, with the lowest melting point of any of the elements, was the obvious choice.

The best source of helium is natural gas. In 1958, a government task force concluded the U.S. reserves of helium were in danger of being depleted as natural gas was burned for heat, and recommended a program of conservation.

Two years later, Congress set up the program, authorizing the Secretary of the Interior to borrow from the Treasury up to $47.5 million a year to purchase and store helium for "essential government activities." Eventually, Congress thought, the program would pay for itself through sales to government and private buyers.

At the time, the only helium production of any significance was by the government's own Bureau of Mines. In a seminal decision whose implications were not to become clear for a decade, Congress decided to spur the creation of a private industry to supply helium, rather than increasing the bureau's production.

"We really had no interest in producing helium" until the conservation program was started, said Craig Colter, an attorney for Cities' Service Helex, one of four private companies the program spawned.

"The government determined they were going to conserve helium, come hell or high water," Colter said. "Instead of doing it themselves, they approached us and said 'OK, what price can you do it for?' Of course, our price was lower than theirs, so we entered into this contract."

The government's contract with Cities Service, like its contracts with Northern Helex Co., National Helium Corp., and Phillips Petroleum Co., was for a duration of 22 years.

The contracts provided that Interior would pay for the helium whether or not it was accepted for storage, unless the secretary determined it was no longer needed for essential government activities, or a new source was discovered or something similar occurred.

For 10 years, from November, 1961, to March, 1971, the program functioned as smoothly as the helium flowing through underground pipelines from four separate production plants to the Cliffside storage facility.

But in the meantime, government agencies' demand for helium bagan to plummet. The space program was severely cut back; treaties with the Russians froze the number of ICBM's. The government agencies that demanded 554 million cubic feet of helium in 1967 needed only 193 million cubic feet in 1971.

With the drop in demand, the source of income for what was conceived as a self-sustaining program begain to disapear. The process was exacerbated by the entry of seven private companies - including two of seven private companies - including two of the four selling helium to the government for storage - into the business of selling helium to other consumers, which undercut the market for government helium.

"The concept of a self-liquidating program just collapsed," said one expert in the held.

Since the contracts nevertheless obligated the government to keep buying helium, the program abruptly slipped into a debt that today stands at $434.8 million.

In 1971, 12 years before the scheduled expiration of the contracts, then-Interior Secretary Rogers C. B. Morton announced the government would no longer purchase helium for storage. The four companies greeted the announcement with outrage.

"It was basically a budgetary decision, as opposed to a valid energy decision or environmental decision or contractual decison, to terminate the program at that time," attorney Colter charged.

The government disagreed. "With the volume of helium we have available (39 billion cubic feet), and with all the federal estimates being that the agencies will need only 6 to 7 billion cubic feet for the next 25 years, we've got six times the amount we'll need in storage," said Ray Munnerlyn, head of the Bureau of Mines's helium division.

The four companies sued the government, charging the decision to terminate the program was a breach of contract, a decision based on the deficit rather than on either of the condition set forth in the contracts.STThey point out that government demand for helium has risen slowly each year since bottoming out in 1972. In addition, they note, the Department of Energy is spending between $200 million and $400 million a year researching the large-scale use of helium as a cooling agent for the massive underground coils that may be used to store electricity in the future.

An interagency task force is studying the helium question, and is expected to issue a report by Jan. 31. The National Academy of Science is also looking at helium, and is scheduled to hold public forums on Nov. 21 and 22.

But the utlimate fate of the program may be with the courts. In a set of lawsuits separate from those filed by the four companies, the courts face a question that could add $600 million more to taxpayers' liability under the program.

At issue is the value of helium at the wellhead. The four companies that supplied the government-stored helium are pipeline companies, which purchase natural gas from gas producers, separate the helium from the gas in their plants, and send both materials on to their destinations.

Neither the landowners who lease their land to the gas producers, nor the producers who sell gas to the pipeline companies, receive any payment for helium. A lower court has ruled that helium has a value of between $12 and $17 per thousand cubic feet at the wellhead.

If that ruling is upheld, the government will become liable for payment of between $9 and $14 per thousand cubic feet for almost all of the helium now in storage, more than doubling its price.

"That's the main constraint against conserving helium at this time," said Munnerlyn.

Later, in a phrase that summed up the expensive helium quandary, he added, "I don't think anyone really knows how much helium we need, or when we'll need it."