Gravity Never Sleeps, And Other Lessons Nations Learn From Space Programs
Filed by KOSU News in Science.
December 13, 2012
Sputnik 1 just beeped. China’s first satellite, launched more than a decade later, simply radioed a communist anthem back to Earth. So far, North Korea’s first satellite appears to be less accomplished.
And that shouldn’t be a surprise.
Given the history of first orbital space shots, North Korea’s apparent struggle with its mission is fairly typical, says David Akin, an associate professor of aerospace engineering at the University of Maryland.
“You generally don’t have high aspirations for either the longevity or the scientific return of a first satellite,” he says.
There are conflicting reports about whether the satellite, launched Wednesday, is safely circling Earth. U.S. officials have been quoted as saying Kwangmyongsong-3 is “tumbling out of control,” while South Korea’s Defense Ministry says it’s too soon to tell if the craft is functioning properly.
Glenn Lightsey, a professor of aerospace engineering at the University of Texas, says if the satellite is in fact tumbling as it orbits, then it’s not going to be very useful for anything other than propaganda points.
“They may not be able to point the radio antenna in a direction where they can communicate with the satellite,” he says.
Akin says that like a lot of small satellites, North Korea’s probably doesn’t have an attitude control system — either in the form of rocket thrusters or other devices that use either electromagnets or gyroscopes.
Not being able to control the satellite in orbit is just one of many things that can go wrong, says Akin.
Just getting into orbit is a precise maneuver. “The problem with launching a satellite is that you have to get to the right altitude, going at the right speed and in the right direction,” he says. “If you miss any one of those, you’re not going to be in the orbit you want to be in.”
And if North Korean mission control can’t stop the satellite from tumbling, its low-Earth orbit could decay in weeks or months, says Lightsey.
“It depends on a lot of things — how high the orbit is and the [atmospheric] drag on the satellite, which will depend on its size and mass and the shape of its orbit,” he says.
By all accounts, the satellite is small, says Akin, and “a lightweight satellite, kind of like a shuttlecock, is going to fall back into the atmosphere a lot sooner than a bowling ball.”
Not every nation’s first satellite suffers the apparent fate of the North Korean mission. One example: the U.S. Explorer 1, launched in 1958 just months after Sputnik 1.
Explorer reached a fairly high orbit and had a radiation detector aboard. It made an important discovery — the Van Allen radiation belt that surrounds the Earth and had previously been unknown.
“That was sort of the jackpot, but it was kind of happy circumstance,” Akin says.
Sooner or later, the North Korean satellite may suffer a fiery re-entry into Earth’s atmosphere. Small objects that plunge from space generally are destroyed long before reaching the surface. But when it’s a big one, such as NASA’s Upper Atmosphere Research Satellite (UARS) that came down last year, some debris survives.
Statistically, about two-thirds of the time, this plunge occurs over water. That’s what happened to UARS, which crashed harmlessly into the Pacific Ocean.
But hitting land can mean problems. In 1978, Soviet spy satellite Kosmos 954 came down over northern Canada, spreading radioactive debris from its nuclear reactor over a large swath of wilderness tundra. [Copyright 2012 National Public Radio]