To the moon in just 9 hours and other stories of speed and intrigue

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Twenty years after the Challenger explosion, NASA's biggest risks of human life are being found, surprisingly, in unmanned missions.

The fastest spacecraft in history, NASA's New Horizons probe, was launched at 2:00 pm Eastern time on Thursday and is now enroute to Pluto. The 3-billion-mile trip will take ten years, but not for a lack of speed, power, or controversy.

Shortly after its lift off aboard an Atlas V rocket, New Horizons separated from its launch vehicle and was already setting speed records. In about the same amount of time it takes someone to drive from Chicago to Memphis, nine hours, the unmanned spacecraft had passed the moon - a trip that took Apollo 11's astronaunts three days to make in 1969.

In just a year, the probe will reach Jupiter, a distance of about 365 million miles (or 641 years by car), and will pick up speed by using the huge planet's gravity as a slingshot. Busting out of Jupiter's gravitational pull, New Horizons will hit a velocity of 13 miles per second, or about 47,000 miles per hour. And even though that's fast enough to make the Chicago-to-Memphis trip in 40 seconds, the remainder of its journey to Pluto will take nine years.

NEVER-BEFORE-SEEN FOOTAGE

The mission will investigate the Kuiper Belt, an area of ice and rocks that fill the solar system past Neptune. The Kupier Belt was known only in theory for decades. Scientists suspected there must be an area somewhere that contains random debris left over from the creation of the solar system. However, the first objects proving the physical existence of the this 4.6-billion-year-old wreckage were discovered in 1992 and have - obviously - never been seen up close.

CNN reported that Alan Stern, the project's principal investigator, said New Horizons is "the capstone of the initial reconnaissance of the planets." He alluded to the long-held belief at NASA that the agency's work is an important part of the United States' national legacy. "It's something that will go down in history, not just for the way it changes textbooks, but for the sort of society we are, that we do these things of lasting historic importance, that we explore beyond our own world."

A RISKY, UNMANNED MISSION

An unsavory part of NASA's legacy, however, is that of several high-profile accidents that have cost the lives of about 4% of all those who have ever attempted to journey into space. Notably, the space shuttle Challenger which exploded shortly after launch January 28, 1986, twenty years ago this month, and the shuttle Columbia which disintegrated during re-entry, 16 minutes before landing on February 1, 2003, have scarred the agency's safety record.

The New Horizons launch was particularly controversial, not just because of these relatively recent accidents, but primarily because the spacecraft is carrying 24 pounds of radioactive Plutonium-238. The craft will use the radioactive material for power later in the odyssey as it travels into areas where the sun's light is so faint that it can no longer be harnessed for energy. And although the energy it will produce is only about what it would take to illuminate two 100-watt light bulbs, it must do so for ten years.

THE RISK OF A HIROSHIMA IN FLORIDA

New Horizon's plutonium dioxide is encased in 18 graphite compartments inside the spacecraft's radioisotope thermoelectric generator. The generator is an aluminum cylinder weighing 123 pounds, roughly the size of three milk crates. Twenty-five other NASA missions have used similar generators, including six trips during the Apollo program.

For this launch, due to nuclear regulatory restrictions, the mission ultimately required the approval of the White House before it could go forward. NASA was ordered to prepare a comprehensive risk study for the government. The agency concluded that the launch posed a 1 in 620 chance of accidentally releasing deadly, radioactive plutonium into the air. Another report from NASA and the Department of Energy put the chances at 1 in 350.

Some environmental opponents of using this radioactive power source compare a possible launch accident to the effect of a small nuclear bomb going off on central Florida's Atlantic coast.

In their environmental impact statement, NASA estimated that in the event of such an accident, the maximum mean dose of radiation sustained by anyone within 62 miles of Cape Canaveral would be equivalent to 15 months of the natural amount the average US resident already receives. Beyond the sickness and loss of life, the financial cost of decontaminating the area could be as much as $1.3 billion per square mile. While the zone directly adjacent to the launch site is sparsely populated, the 62-mile radius an accidenty would affect includes the Walt Disney World and Epcot resort parks, and most of the 1.5 million residents of Orlando.

In preparation for the launch, NASA sent out sixteen mobile teams to measure radiation levels and trained the staffs of local hospitals in helping patients suffering from radioactive exposure.

Luckily, for everyone involved and those nearby, the launch went off flawlessly. Now we can all just relax and wait for New Horizons to send home some amazing pictures from its trip. It should prove to be quite a ride.