Soft-Landing Rocket

With its stiltlike legs and bulging dome, the ungainly contraption looked like a basketball balanced on a bar stool. But the strange rocket that the Navy unveiled last week at its China Lake (Calif.) Ordnance Test Station comes closest yet to solving one of the most difficult problems of space travel: how to make a soft landing on the moon or some even more distant airless planet.

Fully fueled with hypergolic liquids,* the Navy rocket weighs only 700 lbs.; the 1,300-lb. thrust of its engine can easily lift it off the ground. Setting the rocket down gently and upright is a much tougher task. To postpone some of the problems, the Navy flies the rocket up and down a set of vertical cables. This takes care of wobbling and allows the rocket's operators to concentrate on controlling its vertical motion.

The soft-landing rocket has a special NOTS engine (named after the Naval Ordnance Test Station) with a delicately variable thrust. When it blasts off, the rocket climbs the cables as long as the thrust of its engine is greater than its total weight. When the thrust is reduced by electrical signals sent through an "umbilical cord," the rocket can be made to hover, then ease itself gently down the cables to a controlled landing on automobile shock absorbers.

The Navy is encouraged by its success in making an engine with a thrust that can be controlled so precisely. But engineers who have been working on the rocket since 1958 realize only too well that many a problem remains before far-flying spaceships can make such soft landings on their own. Later models will need stabilizing devices to take the place of guide cables. They will also need sensitive instruments to gauge the diminishing distance to the ground. But when such tricky gadgets have been developed, a descendant of the weird bar-stool-and-basketball may some day descend gently on the rugged surface of the moon.

*Liquid fuels that ignite spontaneously when they come in contact with each other.

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