TRULY THE NEWS that a consortium of private undertakers in Florida has been given permission to send ashes into orbit is "one small step for man, and one giant leap for mankind."

The Reagan administration gave the thumbs up sign to the Celestis Group, which will launch your loved ones to kingdom come 6,900 miles above the earth. The president wishes to encourage the commercialization of space, and this is so far the only enterprise that combines consolation with profit. Also it extends the horizons of hope. Those who are not senators or schoolteachers and therefore have no hope of a cosmic ride in life can look forward to one in death.

It sounds wonderful to us.

At $3,900 per shot, it may be a trifle more costly than other more conventional approaches to what in Hollywood is called "foreverness," but this flying Forest Lawn carries a warranty of 63 million years and the promise to those left behind that they can, on certain nights, look up with binoculars and see a luminous spacecraft, and know that Cousin Minnie is just above.

The Celestis Group reports that it is already swamped with orders.

The cremated ashes are reduced to a size which can easily be packed into a lipstick size capsule. The Conestoga II, the name of the funeral rocket, can hold 10,000 such remains.

This is where we come to what may be the true meaning of this breakthrough in our way of death.

Why could we not share the secret formula for reducing the remains to a mimimum with the Soviets?

They, too, must have their share of people who yearn for eternal orbit as an alternative to the cold, cold ground. What could ensue would be a non-lethal competition in the building of ever larger, ever shinier, gravity-defying mausoleums.

It is true that the risk of celestial crashes, or even grlock might arise. But if two tombs collide 6,900 miles up, what is the difference? It would be a literal case of "ashes to ashes and dust to dust." A few flecks from either vault might fall to earth, in comradely commingling. There might be the odd lawsuit from earthbound relatives deprived of the periodic "visits" with the departed, but in due course perhaps a cooperatively operated cosmic traffic- control satellite could be sent up to prevent pileups amid the stars.

In looking to the future, we have to face one possibility, and that is that if we go for the space cemetery, we would have to give up the president's other extraterrestial plan, namely Star Wars.

Let us be philosophical about it. The president admitted in the State of the Union address that the system is "not well understood." The more he explains it, the less understood it is.

Our European allies are falling into line on the project, but could it ever be as popular as the Everlasting Express? Given a choice of being incinerated before or after death, most people would go for after. And Star Wars is extremely expensive and does not have carry any warranty.

The president concedes that a missile or two might get through.

He told the Wall Street Journal: "Oh, I've never asked for 100 percent. That would be a fine goal: but, you can have a most effective defensive weapon, even if it's not 100 percent."

That's easy for him to say, but what if you are on the receiving end of the fatal percent shortfall. One from the Kremlin is all it takes to reduce your city to radioactive rubble, and you to ashes.

If the whole world decides to send its dead sky-high, there just would not be space enough for the X-ray lasers, the pop-up interceptors, the geostationary battle stations and the other expensive paraphernalia needed for the Strategic Defense Initiative.

Oh, sure, somebody from the Pentagon will probably say that our orbiting tombs could be militarized to intercept inoming missiles, and kill two birds with one stone, so to speak; but it is doubtful that families would tolerate having Uncle George drafted for combat, after he and his flight companions have won the Ultimate Exemption.

It's the chance of a lifetime for us to slash the military budget and kick the deficit. Think of the arguments we will avoid; think of the money we will save. Think of peace hereafter bringing us peace here. We can call our arms control negotiators home and let our scientists go back to trying to find a cure for the common cold.

Is it not a heavenly idea?