The Grumman Company, which built vehicles for the moon, and which is one of the leaders in space technology, has been having trouble building a bus that won't collapse when it tries to get from 23rd Street to 15th Street on Madison Avenue in New York City.

This has caused tremendous consternation in engineering circles. How can someone develop a lunar lander for the moon without any difficulty and not be able to build a bus for New York and other cities?

I discussed this with an urban transportation expert, and he said the Grumman people were not at fault.

"Building a bus for New York City is not the same as developing a moon vehicle. There were so many unknown factors that Grumman had to deal with. New York streets have a far harsher atmosphere than the moon. For one thing, New York's craters are much larger than anything up there. For another, the environment in Manhattan is so unpredictable that no one can be sure what pressures a bus will encounter when it tries to crawl across town."

"But surely the Grumman people must have tested its Flxible bus before it delivered it."

"Of course they did, but all they had to go on were aerial maps of Manhattan taken from five miles up.

"They had no idea what they would face once the Flxible model was actually put on a street. Everything worked perfectly in the lab, and Grumman scientists were certain their bus could hold up under the toughest jobs it would have to perform on Earth. But unfortunately, when you're dealing with an unknown crust, such as New York City, you have to expect setbacks.

"We now think we know what the problem is."

"What's that?"

"Grumman didn't realize that the buses could carry people. So they failed to make the trunnion strong enough to support the frame. After four blocks, the frame developed cracks, the trunnion collapsed against the wheel, and the bus couldn't move. Urban mass transportation is still not an exact science, and it could have happened to anybody."

"Does this mean New Yorkers will never be able to have buses they can count on?"

"Not necessarily. But a lot more work has to be done in bus research. First of all, we must devise a way of mapping New York City's potholes. No bus can be expected to hit one and not collapse, no matter how strong you build the trunnion. For another, we have to test these buses under the worst-situation conditions. This means we have to load them with twice their capacity, and drive them for days through Queens, the Bronx and Brooklyn, where the streets are almost impassable.

"If the trunnion hold up to these rugged tests, they should be able to survive anything that could happen to them in Manhattan."

"Does the failure of the Grumman Flxible bus mean that our entire space program on Earth will be delayed?"

"No, it only means that New Yorkers will have to do their exploration on foot until the engineering mistakes have been ironed out. We can't afford to send another bus to New York City until we're sure it will work. Actually, the failure of the Grumman Flxible could be considered a plus for the space program. We know that many cities were going to order the Flxible buses, and if something terrible had to happen, better it be in New York, which is used to its public transportation breaking down, than in Boston."