4 December 2005
Destined to explore the icy edges of the solar system, the probe is equipped with a generator that will convert heat from the decay of 24 pounds of plutonium into electricity to heat and run the spacecraft systems.
Government studies show that the mission poses more danger to Central Florida than a typical rocket launch. So much so, in fact, that White House approval -- which is expected early next year -- is required to give the go-ahead for launch.
There is a 1 in 350 chance that a launch area accident could release radioactive plutonium somewhere in a six-county area surrounding Cape Canaveral, according to a review of public records and interviews with government officials. Anti-nuclear activists worry about worst-case scenarios spelled out in safety reports, saying an accident could devastate nearby communities, although the studies indicate the likelihood of such a disaster is about 1 in 18 million.
The plutonium fuel aboard the spacecraft is not the highly explosive material used in nuclear weapons. It is a different grade only dangerous to people if reduced to fine dust. The maximum dose a person might be exposed to in most accident scenarios would be similar to seven or eight medical X-rays, according to the government studies.
The type of radiation, alpha radiation, is easily shielded. It cannot penetrate the skin, clothing or even a piece of paper. It is only dangerous if inhaled or ingested. The regional risk drops to nil 40 seconds after liftoff. By that time, the 205-foot Atlas rocket will have arced out over the Atlantic Ocean, and the studies found no chance of a plutonium release if the rocket crashes into water.
Nonetheless, emergency management officials ask people to be aware of plans to launch the New Horizons spacecraft between Jan. 11 and Feb. 14.
If the rocket explodes, sending a cloudlike plume drifting toward populated areas, officials say there would be no cause for alarm or evacuation.
As with any launch accident that releases toxic rocket propellant, people might be asked to seek shelter in homes, buildings or cars.
They might be asked to bring pets inside, close doors, windows and fireplaces, and turn off air conditioners.
"The biggest danger is the possibility of public panic, and there is no reason for that at all," said Bob Lay, director of the Brevard County Office of Emergency Management. "You have a heck of a lot higher risk driving down I-95 than being hurt in this thing."
Others beg to differ.
Anti-nuclear protesters say the government studies also outline alarming worst-case scenarios.
Should the Atlas 5 rocket fail early in flight and crash into hard ground, people within 62 miles of Cape Canaveral could be exposed to fine particles of plutonium. That would increase the chance that up to 100 people in the area could get cancer some time in the next 50 years, according to studies by NASA and the Department of Energy.
Up to 115 square miles of land could be contaminated. Clean-up costs could range from $241 million to $1.3 billion per square mile, in an area that could stretch from Daytona Beach to Vero Beach and Orlando.
The odds of that: about 1 in
Considering the potential consequences, some say the risk is not worth taking.
"You think hurricanes are a problem? Think of the mess cleaning up after a plutonium release," said Bruce Gagnon, coordinator of Global Network Against Weapons and Nuclear Power in Space, based in Maine.
"Imagine making that area a nuclear wasteland," he said. "That's always been our deep concern. The possibility of accidents and the reality of contamination."
The controversy is about the craft's electrical power system, a device known as a Radioisotope Thermoelectric Generator.
Similar generators enabled the U.S. to send robotic scouts to the outer planets, destinations too far from the sun for solar panels that convert sunlight into electricity. Over the past half century, the nuclear generators were used on 25 U.S. missions, including the Apollo flights to the moon and voyages to Mars, Jupiter, Saturn, Uranus and Neptune as well as a mission to study the sun's poles.
The generators for the most part have proved safe and reliable. But there have been problems.
In April 1964, a U.S. Navy satellite failed to reach a stable orbit and its nuclear generator disintegrated, as designed, during atmospheric re-entry. About 2 pounds of plutonium dispersed, increasing by 4 percent the amount in the global environment, most of which came from the fallout of atmospheric nuclear weapons testing.
Redesigned for safety
The incident prompted a generator redesign geared at ensuring the devices would not spew plutonium in an atmospheric re-entry accident.
The redesigned generator was put to the test on its first mission. A NASA weather satellite had to be destroyed by Air Force safety officials when its carrier rocket went off course shortly after a 1968 launch from Vandenberg Air Force Base in California.
The mangled satellite was recovered from the Santa Barbara Channel, its nuclear generator intact. Its plutonium fuel was reclaimed and used to power another satellite launched the next year.
Another nuclear generator was aboard the Apollo 13 lunar lander, which served as a lifeboat for three astronauts when their 1970 mission was aborted on the way to the moon. The astronauts ultimately returned to Earth safely in the command module, which was seriously damaged when an oxygen tank exploded.
Their lunar lander re-entered Earth's atmosphere separately, plunging into the South Pacific Ocean. It came to rest at the bottom of the 20,000-foot-deep Tonga Trench. Extensive sampling of the remote ocean area showed no plutonium was released.
For New Horizons, the federal government plans to station 16 teams at sites between the southern ends of Brevard and Volusia counties. In a launch accident, radiation detection devices would enable them to determine whether plutonium was released and the relative danger, if any, to launch site workers or people in surrounding communities.
People living in communities downwind from any drifting plume likely would hunker down inside their houses for about an hour or so, Lay said. That's the estimate for how long it would take for field teams to determine the risk to local communities. If none, county emergency management officials would broadcast an "all clear" and normal life would resume.
"I think Mr. and Mrs. Brevard County should feel very comfortable" with the approaching launch as well as emergency plans, Lay said.
"But as with any launch, Mr. and Mrs. Brevard need to be aware that there is a launch, and if there is a contingency, they need to know what action to take," he said. "The absolute worst case I can imagine would be having to tell people to shelter in place. Not to evacuate, but to shelter in place."
Contact Halvorson at 639-0576 or firstname.lastname@example.org
See also: other articles on New Horizons