March 16, 1999
Web posted at: 9:18 a.m. EST (1418 GMT)

ATLANTA (CNN) -- You never know where you might find inspiration. That's why scientists are always talking about the serendipity of research and development.

The Hubble Space Telescope

Isaac Newton might have had an uneventful forty winks under that apple tree had that piece of fruit not made the moment so weighty. Same goes for Elmer A. Sperry. Elmer was just goofing around that day he started playing with a child's top.

Around and around it went, spinning a brilliant insight into Elmer's head. He noticed that a weighted rim spun rapidly tends to remain in the plane in which it is spinning. The concept is called "Rigidity in Space," and Elmer's mind was nimble enough to immediately see the potential.

In 1910, he founded the Sperry Gyroscope Company -- initially designing devices to stabilize ships. But soon he became aware of another potential market. For early aviators, instrument flying often consisted of weighted strings or silk stockings tied to wing struts. But even the best seat-of-the-pants flyers easily found themselves spinning out of control once they flew into clouds.

So Sperry developed three crucial flight instruments: the turn and bank indicator, the gyroscopic compass and the artificial horizon. Eighty years later, no one has come up with a better way to allow pilots to keep their aircraft on course and under control when they can't see out the window. Without Sperry's gyroscopes, we'd all still be using trains as our primary inter-city transportation.

We also would never have made it very far in space. Every spacecraft uses gyroscopes to remain stable and properly aligned. This past week, a General Electric communications satellite -- used by CNN, PBS, Fox and many others -- spun out of control for several hours after one of its gyros died. Apparently, a high-energy particle penetrated the skin of the spacecraft.

Several thousand miles below, the Hubble Space Telescope needs gyros spinning on three different axes (pitch, roll and yaw) to do perform its scientific mission. There are six gyroscopes on the telescope and as of about a month ago, only three were still spinning. So a billion-dollar telescope, which continues to marvel astronomers and the public alike, is one failure away from being scientifically useless.

That is why NASA decided it was worth the cost and the risk to split the Hubble servicing mission No. 3 -- originally planned for next June -- into two flights. The "emergency" repair run (3A) will probably happen in October. The tasks left undone then will be accomplished in late 2000 on Hubble repair run 3B.

Using government arithmetic, the extra flight will cost the shuttle and Hubble programs about $75 million. NASA's Hubble Honcho Ed Weiler says it's money well spent when you think of it this way: If the telescope failed, scientists would be without a national treasure with a budgetary appetite of about $20 million a month whether it is making discoveries -- and inspiring school kids -- or not.

So by paying $75 million to arrive at Hubble eight months earlier than planned, NASA is buying some insurance that it wont have to spend $160 million maintaining a telescope with its lens cap screwed on for eight months. As Ed Weiler puts it: "three months without science is the break-even point." Hey, you gotta spend money to save it. At least that's what my wife keeps telling me.

So why did the gyros fail? No one knows for sure, but Weiler admits, in hindsight NASA should have replaced them during the last Hubble house-call in 1997. They were changed out on the first servicing mission in 1993 and those old mechanical gyros -- with their rotors spinning in a viscous fluid -- are generally considered good for four to five years.

Rigidity in space may be a rock-solid principle. But flexibility comes in handy too.

Miles O'Brien's column appears on Tuesdays.