Nail-biting ride into radiation maelstrom seeks to unlock space secrets (pictures)

Human space travelers will not find a hospitable welcome in a couple of doughnut-shaped radiation belts that stretch thousands of miles into space. Known as the Van Allen belts, the region is filled with killer electrons, plasma waves and electrical currents. Scientists believe similar radiation belts also exist on other planets in the solar system and now they'll be able to back up their assumptions with hard data.

Shortly before dawn today, two NASA probes lifted off from Cape Canaveral, Fla., heading for the heart of the Van Allen belts. It's the dual-spacecraft mission sent to investigate this hazardous regions of near-Earth space.

In 1958, James Van Allen discovered the region, which is split into two so-called belts; the outer part is formed by energetic electrons, the other by protons and electrons forming the inner belt. Van Allen was recognized by Time magazine as the person most responsible for giving the U.S. "a big lead in scientific achievement" and included in the group of scientists it honored in a collective pick for its annual Man of the Year.

NASA's two spacecraft were sent directly into the radiation belts to explore the region over the next couple of years. The craft will periodically lap each other, passing as close as 100 miles from each other and as far apart as 24,000 miles or so. The two probes will have nearly identical eccentric orbits.

The two-year mission will seek to explain why the radiation belts are so dangerous and unpredictable.

The Van Allen belts pose a threat to astronauts and they can affect sensitive satellite systems and even power grids on Earth when buffeted by powerful solar storms.

America's first satellite, Explorer 1, disproved the widely-held assumption that the region around Earth was empty.

Equipped with a Geiger tube, the Explorer 1 found so many charged particles as it circled the Earth that the counter registered off scale most of the time.

When the radiation belts were first discovered, the news meant little to most people as they had little impact on our lives. But as society has come to depend upon high technology, the vagaries of the Allen Belts can possibly damage satellites commonly used for everything from weather prediction to GPS to TV.

During geo-magnetic storms, when the belts are swollen by solar activity, whole fleets of satellites can be engulfed. One of the biggest mysteries of radiation belts is the crazy way they react to solar storms.

NASA noted that Earth satellites can be affected by particles in the Van Allen belt, and, in fact, it has happened that those satellites have actually been knocked out by radiation.

A better understanding of the physics driving the radiation belts will improve scientists' ability to forecast Earth's space weather and its effects on sensitive electrical systems.

The probes will send back data that scientists can use for predictive models allowing forecasters when it's safe to carry out spacewalks or operate sensitive electronics in the Van Allen belts.