Mission to Pluto depends on Idaho

By: 
AP
Staff Writer

IDAHO FALLS (AP) — It's been nine years and more than 3 billion miles in the making.
Space geeks around the world should soon have a plethora of new knowledge about Pluto's atmosphere, geology and moons as NASA's New Horizons spacecraft transmits to earth the photos and data it collected as it passed within about 7,800 miles of the icy dwarf planet.
Idaho National Laboratory researchers are eager to see results, too. They played a key role in this first-of-its-kind space mission, building and testing a 202-watt power source that steadily kept New Horizons' instruments and communications systems up and running for nearly a decade.
The power source is called a radioisotope thermoelectric generator, but employees just call it an RTG. In photos and artist renderings of New Horizons, it's the cylindrical black piece of equipment with little fins attached, protruding out of the spacecraft.
Three years ago, INL researchers watched as another of their RTGs helped NASA's Mars rover Curiosity explore the Red Planet. In that case, however, the researchers had to wait just nine months — not nine years — to see if their RTG could handle the job.
RTGs use heat from the natural decay of plutonium-238. That thermal energy is converted into a steady source of electricity. It's a power source that — unlike fuel cells, batteries or generators — won't run out of juice for years.
"This mission is a 10-year mission just to get there, and (NASA) wants to steer it out past Pluto, into the Kuiper belt," said Stephen Johnson, who heads up INL's space nuclear power program.
"You need something that's going to last a long time," he said. "Everybody knows if you get a bucket of coal you can light that up and the coal is going work for a day or so. That's great, but we need something that's going to put out heat for more than a decade — so you need a radioisotope of some sort."
On a recent tour, Johnson led a group of reporters through several security checkpoints into the Space and Security Power Systems Facility. The 10,000-square-foot building, located 30 miles west of Idaho Falls, holds a variety of equipment for piecing together and testing RTGs. A maze of exposed piping and gadgets lines the walls.
At one stop, Johnson showed off an airtight chamber where RTGs are remotely fueled up and pieced together, a process that can take weeks. For projects like New Horizons, INL builds just one RTG — there's no backup. Scientists have to get it right, Johnson said.
Windows filled with water protect workers from the radioactive materials as the assembly process takes place. There are robotic arms, or manipulators, and sealed gloves for safely working inside the chamber.
In another room, at something known as a shaker table, engineer Robin Stewart explained how an RTG is put through its paces by a series of violent vibration tests. The purpose is to ensure the RTG is strong enough to survive a rocket launch, and, in the case of New Horizons, that it will hold up after hurtling through space at 31,000 miles per hour.
Yet another stop in the testing process is a massive cylindrical vacuum chamber, which provides different pressures to mimic space conditions. After that step, INL officials are able to accurately tell NASA how much electricity their RTG will produce at a number of different conditions.
Start to finish, the process of building and testing can take around six months, Johnson said. The New Horizons RTG was worth about $100 million when it left INL; that's out of a total New Horizons mission cost of more than $700 million. Close to 80 INL employees worked on the project.
Already, some remarkable information about Pluto is trickling back to Earth as New Horizons began its approach. The dwarf planet isn't as small as initially thought, scientists said, measuring about 1,473 miles in diameter. There also were confirmations that Pluto has a polar ice cap.
Even after zooming by Pluto and checking out its mysterious moons — including the largest, Charon — New Horizons and its RTG won't be finished. NASA and officials at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., plan to send it deeper into the Kuiper belt — a vast region of rocky, icy objects extending far beyond the planets.
"This is pure exploration," said Alan Stern, the mission's leader, in an April press conference. "We're going to turn points of light into a planet and a system of moons before your eyes."
The INL space researchers won't have too much time to savor the Pluto milestone. They're working on RTG projects for clients other than NASA, which Johnson said he can't talk about. And soon the program will begin staffing up to build an RTG for NASA's next Mars mission, set to launch in 2020.
But expect the INL researchers to be glued to NASA webcasts tracking New Horizons' progress.
"Not many people have to wait 10 years for the payoff of their hard work, but it is enormously gratifying to see the close-up imagery being beamed back," Johnson said.

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