Double-bagged in gray plastic wrap, the payload was ready to take its first step toward becoming a grown-up space probe: getting out the door of Hansen Experimental Physics Laboratory.
Dozens of scientists held their collective breath for four days in late August while technicians slooowly tipped the giant thermos bottle upright, hoisted it onto a tilt dolly, slid it into low-rider mode, then returned it to a horizontal position. Once the payload cleared the doors to the parking lot—by inches—a crane swiveled it onto a rack aboard a Vandenberg Air Force Base transporter and capped it off with a domed cover. Then it was off to Building 205 at Lockheed Martin Missiles and Space Co. in Palo Alto for mating and integration with the space vehicle.
So began the final countdown for Gravity Probe B, a 42-year, $500 million NASA experiment that has enlisted hundreds of scientists, graduate students and undergraduates from a dozen different Stanford departments. They’ve created the world’s most perfectly round objects and plotted stratagems to outsmart magnetic fields, all in pursuit of a fundamental tenet of physics that is next to impossible to demonstrate in the laboratory and darned tricky to test in outer space—Einstein’s general theory of relativity.
“Is it the longest running experiment at Stanford?” muses physics research professor Francis Everitt. “Well, it’s perhaps been the slowest to develop, mostly because of the enormous number of new technologies that had to be invented.”
As he ticks them off—cryogenics, magnetics, telescope design, control systems, quartz fabrication and gyroscope fabrication—the complexity of the GP-B project begins to emerge. The probe was initially expected to be completed in 1990. Then 1995. Then 1998. A launch was actually scheduled once, for October 2000. Now, the spacecraft is scheduled to lift off from Vandenberg in October 2002. By that point, Everitt and his colleagues, including three emeritus professors—program manager Bradford Parkinson, PhD ’66, hardware manager John Turneaure, PhD ’67, and engineering systems manager Daniel DeBra, PhD ’62—will have defined a new and widely tested general theory of patience.
The project has had several near-death experiences. Congress has threatened funding cuts a half-dozen times; Everitt, the principal investigator since 1962, successfully lobbied against them each time. And just last January, he walked in on an ashen-faced Turneaure moments after Turneaure had discovered a flaw in a critical epoxy. “It had sinister implications, and we had to fix it,” Everitt says. “John thought of a method that required only nine months of delay.”
Nothing less is at stake than the most accurate test ever of Einstein’s theory about gravity. Physicists use a number of visual images to describe the concept of the warp, or curvature, of space and time. There’s the spinning marble dropping in a bowl of unset Jell-O, or the human cannonball plummeting into a safety net—both of which can be seen to dimple and then drag the liquid or fabric as they land and rotate. Einstein stated that the gravitational effects of a spinning planet similarly warp space and time. But his theory, Everitt says, may be “incomplete.”
Shortly before the probe left for Lockheed, Everitt walked a visitor through the lab, where signs on the double doors to the GP-B inner sanctum proclaim “Sensitive Testing in Progress” and a sticky floor pad sucks specks of dirt off entering shoes. As he checked the temperature of the giant thermos bottle—warm, that day, at 4.2 degrees Celsius above absolute zero—Everitt called to mind Einstein in profile, with shoulder-length gray hair fleeing in several directions.
Everitt brought forth four pingpong-ball-sized quartz spheres, rounded to one-half millionth of an inch, that are like those at the core of the experiment. Suspended in midair inside quartz housings on a current produced by tiny electrodes, the gyroscopes spin at 10,000 rpm. Because they are coated with a thin layer of metal that is a superconductor, they behave like little magnets and have pointers that can be used to measure the direction of their spin.
Stacked on top of one another, the four housings are attached to a block of fused quartz, which is bonded to an all-glass telescope. The block of instruments is nestled in a long, cigar-shaped vacuum chamber—the probe—that fits inside the dewar, a.k.a. thermos bottle. More than 600 gallons of superfluid helium surround the probe, keeping it at near-zero temperatures to improve its mechanical stability for the 19 months of spaceflight. As the spacecraft orbits the poles more than 400 miles above Earth, the spinning gyroscopes and telescope will all point at the same distant star in the galaxy, HR-8703. Einstein’s theory predicts that the earth’s gravity will cause the gyroscopes to deviate slightly from their original spinning axes; if all goes well, the researchers will be able to measure any shift.
Back inside the campus operations center, the countdown clock measures the remaining days in bright fuchsia numbers: 431: 9: 15: 43. “We have a lot of testing and training to do between now and then,” says flight director Marcie Smith. “And for the first 40 days [after launch], we’ll be running around-the-clock operations.”
Not unlike the tiny quartz gyroscopes, spinning furiously in space.
