We are the first generation in space and we forget it. We forget that during the first three years when records were kept of such things in aviation, there were 33 fatal crashes in a world of only 1,000 fliers. "My memory is one long obituary list," said Anthony Fokker, the great Dutch pilot and engineer.

After 56 harmless manned space flights in succession it is easy to forget. After the tragedy of Challenger we will remember, at least for a time. We will tremble the next time engines light up to lift a man into space.

The first reaction to the death of Challenger and her brave crew, after the shock and the grief, was grit: the determination, as expressed by the president, to carry on, just as those who died would have wished.

A second reaction will quickly follow. Doubt. Is putting man in space really worth the cost and the risk?

It is an irony that the worst tragedy in the history of manned space flight coincides with one of the great triumphs of unmanned exploration, Voyager II's discoveries on Uranus. The conjunction of these two events gives immediacy to a question asked long before the Challenger catastrophe. Why rush to put men rather than machines into space?

Machines are better, safer, cheaper, says physicist James Van Allen (discoverer of the Earth's radiation belts) in the current Scientific American. We are going about space the wrong way, he argues. It is not our bodies but our minds, borne by rocket legs and robot eyes, that should be in space. Lugging bodies that demand oxygen and leg room and safety is inefficient. It is also bad for science. It steals funds away from past and future Voyagers.

The skeptics are not just ruminating. They have a target. Not the shuttle. The shuttle will live. It is now practically our only means of launching satellites. We have nearly disposed of disposable rockets. We have too much invested in the shuttle to turn back, even after Challenger.

The target is the manned space station. The president has called for building one by 1992, the 500th anniversary of the European discovery of America. It will cost at least $8 billion. Contracts have already been let, but it is the target of budget cutters in OMB and Congress, and of a chorus of critics who see in it all that is wrong -- mundane and frivolous -- with manned flight.

"An expensive yawn in space," The New York Times called the space station when Reagan first proposed it in 1984. Four weeks ago, The Times added: "an $8 billion white elephant." Britain's prestigious scientific journal, Nature, called the space station a "tragedy . . . another two decades of original research on why astronauts vomit." And besides, says the ubiquitous Carl Sagan, "machines are more reliable than people."

And so they are. But they cannot sing. And when they round the dark side of the moon, they do not recall Genesis.

The sensible types are right that man in space is bulky, demanding, expensive, a bother. Nature is right that, in space, people tend to "bump about and jiggle telescopes, disturbing the hardware."

Van Allen says that "apart from serving the spirit of adventure, there is little reason for sending people into space." Well, yes. Or for sailing west to the Indies. Or for crossing the sands of Kitty Hawk in a biplane. Or for -- How do you argue with sensible people? I wonder: What could Amundsen have told his banker to explain why he had decided to walk to the South Pole?

Yet even the sensible types can't help betraying a trace of appreciation for the romance of manned flight. The Times' most recent bash of the space station contains a reference, meant as a contrast, to "the splendid success of the Apollo voyages to the moon." But from the sensible point of view, Apollo was an exercise in frivolity. We spend a decade putting men up there, and what do they do? Drive around. Pick up rocks. Play a little golf. A robot could have done all that, except possibly the golf, at a tenth the cost.

Even sensible types must occasionally succumb to the majesty that is man braving the void. How can anyone live in this age and not dream of the first celestial habitat, of way-stations and colonies, of orbital space with addresses (and ZIP codes!)? You might as well take a child to a dark room and show him slides of a sunset. It is cheaper and more fuel-efficient than a trip to the hilltop, and will spare both of you unnecessary exposure to cancer-causing ultraviolet rays.

I admit that Uranus and her moons are beautiful in pictures. And there is a romance of pure knowledge too. To discover 10 moons that did not exist yesterday (in our consciousness) is nourishment for the spirit. The mind-over-matter space ascetics are right: Voyager has its place in space. But so does man, tiresome body and all.

Asks The Times, "What could a man do on Mars that robots could not do far better?" Weep, wonder, dream . . . look back to Earth and know what he had done.