 |
|||||
|
by Robb Fulcher
When the former Soviet Union launched the Sputnik satellite 42 years ago, the effect was electrifying. America's space program was immediately pushed into overdrive. The race to propel objects, animals and people into the suddenly accessible heavens assumed immense importance.
Since then, some 4,500 tons of human-launched material has blown up, melted down, fallen apart or simply remained adrift in space, slowly turning the new frontier into a cosmic junkyard.
Small pieces of space debris have already struck satellites as they make their orbits, and scientists are working to determine when these objects will begin striking each other as they streak around the earth.
Scenarios for the future of space debris vary; the darkest one has large objects beginning to smash into each other within 20 to 40 years, possibly setting off a disastrous chain reaction of colliding, caroming fragments that could slowly but surely wipe out all orbiting satellites. Each collision would create more fragments, exponentially increasing the chance of further collisions.
Among the leading figures in the effort to mitigate the effects of space debris is Vladimir Chobotov of Palos Verdes Estates, a bright-eyed 70-year-old now serving as a semi-retired consultant for the Aerospace Corporation in El Segundo.
Chobotov believes the chances are remote for space to become a cataclysmic pinball machine of flying junk, but he is at the forefront of efforts to mitigate the immediate danger posed to orbiting spacecraft by large pieces of floating debris. One such collision occurred in 1996, when a chunk of space trash disabled a French satellite.
As of July 1998, observers were tracking and cataloguing some 8,500 human-made objects measuring about five inches or more, only about 6 percent of which are operational satellites. Scientists estimate that about 110,000 smaller objects are in orbit that also could present some danger to the 600 satellites currently floating above the Earth.
"The problem of collisions with larger debris are small, but there are extreme consequences if that does occur," Chobotov said.
These pieces of space junk include everything from entire rocket stages, fragments of rocket stages that exploded when residual fuel was heated by the sun, and miscellaneous hardware such as nuts and bolts.
The number of man-made objects is small compared to the number of meteoroids, rocky or icy bits of material left over from ancient objects like comets, also in orbit. But the debris generated by our space programs are generally much larger and therefore more dangerous, said Chobotov. Some of these objects, propelled by the force of the explosions that fragmented them, tear around the Earth at tens of thousands of miles per hour, in orbits different than those of man-made satellites.
One satellite, which was retrieved a decade ago by the Space Shuttle Columbia after six years in space, bore scars from collisions with as many as 100,000 small objects, about 20 to 30 percent of which are believed to have originated here on Earth.
The odds of a single U.S. Department of Defense satellite sustaining a crippling collision with a small piece of space junk is calculated at one incident within the next 500 years.
But the odds for such a collision involving a NASA satellite, which are 10-times larger, are calculated at one incident within the next 95 years.
Scientists are working on ways to better shield future satellites, and an international community of space scientists has identified measures to prevent the chances of collisions. Regulations have been put in place to require fuel venting before a rocket stage is jettisoned, to prevent the fuel from exploding and fragmenting the section.
Another measure calls for the removal of satellites from the common orbiting altitude when their missions are ended. "Kick motors" would be used to propel the satellites up into higher altitudes, preventing them from becoming a problem in the future.
Scientists have shelved notions of cleaning up space debris by using lasers or a gigantic "space vacuum" that would tow the junk away. Those measures are too costly and would require too much development, Chobotov said.
A visit to Chobotov in his work environment requires a visitor to pass through the security gauntlet of the Aerospace Corporation's Building D-8. He is holed up in a small, cluttered second-story office.
An alert, gracious, soft-spoken man with the "what if" curiosity of an engineer, Chobotov patiently uses teaching handouts to bring visitors at least partially up to speed on the highly specialized world of space debris.
He jokes easily, laughs often and smiles as a matter of course. The impish effect is enhanced by the broad smile on his photograph, which peers up from the security badge clipped to his long out-of-style striped shirt. A tweed jacket hangs nearby, conspicuous only its lack of elbow patches.
The conversation takes sharp turns in trajectory as peripheral items of interest pop up, including the notion of a future satellites secured to Earth by an enormous tethers, the likes of which exist now only in the imagination.
"I wrote a paper on that," Chobotov said, diving into a gray metal filing cabinet.
Chobotov was born April 2, 1929 in Zagreb, Yugoslavia, where his parents had fled after resisting the spread of communism in the former Soviet Union. His family then fled to the U.S. in 1944 as communism overtook Yugoslavia. He earned a master's degree in engineering from the Brooklyn Polytechnic Institute and began working at Ramo-Wooldridge, the El Segundo corporation that has permutated into what is now TRW. The not-for-profit Aerospace Corporation was formed in the '60s, and Chobotov began working there. Becoming a section head in the '70s, he earned his doctorate in mechanical engineering from USC along the way. He stumbled onto space junk as a specialty in the mid-70s, following a colleague's casual question.
"It happened by accident," Chobotov said. "One of my coworkers had asked me a simple question, 'What would happen to a rocket stage that remained indefinitely in orbit?' I began to research this, and I found in addition to natural micrometeorites, there were fragments of man-made objects in space. There was a field of man-made particles. That was a revelation at the time."
A notable bit of confusion soon followed. The influential Aviation Week magazine published an article on the subject and erroneously attributed to Chobotov's agency an alarming prediction concerning space debris.
The article made its way to the desk of Arthur Mager, then executive vice president of the Aerospace Corporation, who naturally wondered aloud why he had been left out of the loop of such a dire prediction.
"I thought I might be fired on the spot," Chobotov said with a smile.
Mager was told about the mix-up by the magazine and Chobotov's blamelessness was affirmed. But the discussion had the side effect of interesting Mager in the subject of space debris.
"From then on I was employed full-time working on space debris," Chobotov said.
Today much of his time is spent using computer modeling to answer such questions as, "If there is an explosion [in space] where will the fragments go, and what will happen to the next poor sucker who goes through that cloud?"
Earlier in his career, before he started poking around in space debris, Chobotov used his background in dynamics and acoustics to help in the design of U.S. rockets.
"I would go out into the Mojave Desert and listen to rocket noise," he said. "I would try to measure it, so we could build systems that would shield the components from noise and vibrations."
In the late 1950s he helped build super-suspension systems for the old Atlas nuclear missiles that lurked patiently underground in places like Montana and South Dakota, waiting for the day when the U.S. and the Soviet Union would come to blows.
The suspension systems were needed in case the Soviets used their own nuclear missiles to attack the Atlas silos. The incoming missiles would strike against the very doors covering the Atlases, which would have had to withstand the shock if they were to be of any use.
These days Chobotov is called on to deliver papers to scientific gatherings around the globe. He recently returned from the 50th International Astronautical Federation Congress in Amsterdam, where he spoke upon "Analysis of the Micrometeoroid and Debris Hazard Posed to an Orbiting Parabolic Mirror," which he prepared along with A.B. Jenkin.
In his free time, Chobotov likes to shore up his admittedly eroding chess game, indulge his passion for photography, and fiddle with his three computers.
Practicing a pastime at odds with the scientific stereotype, he also likes to drive fast in his black, 400 horsepower ZR1 Corvette. He said it's the fastest production car built in the U.S.
"I know that doesn't go with my reputation as a careful calculator," Chobotov said, smile firmly in place. ER