Will NASA Recover Apollo 13's Plutonium 238?

Apollo 13 Astronaut Fred Haise extracts the fuel element for the SNAP-26 RTG during training

Credits: NASA

Somewhere among the jagged trenches of the South Pacific sits a graphite fuel cask containing 3.9 kg of plutonium from Apollo 13.

The fate of the radioactive plutonium-238 has long been overshadowed by the successful return of the three NASA astronauts on board the ill-fated mission.

The plutonium was supposed to fuel the System for Nuclear Auxiliary Power, or SNAP-27 Radioisotope Thermoelectric Generator (RTG), designed to power a set of experiments on the lunar surface but after an explosion crippled the craft and forced the crew to abandon plans of a lunar landing, the plutonium became yet another problem for mission control.

Officials from NASA confidently told The New York Times that the biggest risk was that the 40-pound generator might hit someone when it fell to Earth.

“It will keep a few fish warm,” a NASA official said. The Atomic Energy Commission, on the other hand, conceded the slight possibility that it could become ground into dust and dispersed.

NASA learned its lessons about engineering the fuel casks the hard way: in 1964, the Transit-5-BN mission aborted and the RTG burned up upon reentry above Madagascar, in keeping with its design.

Traces of plutonium were found in the area months later. In 1968, the Nimbus B-1 weather satellite was aborted soon after takeoff from Vandenberg Air Force Base and the plutonium from the SNAP-19B2 RTG plunged into 300 feet of water off the California coast, with no release of radiation.

Apollo 13’s SNAP-27 fuel, as far as we know, slipped beneath the waves and came to rest 6 to 9 kilometers deep in the Tonga Trench, one of the deepest areas in the ocean.

Subsequent testing by the U.S. Department of Energy has shown no spike in background radiation.

Not surprisingly, NASA has no desire to go looking for the small cask, even with advances in submersible technology that would make such a mission at least technically feasible.

“I don’t think that anyone has seriously considered that because of the cost of recovery,” said Leonard Dudzinski, a NASA program executive who deals with radioisotope power systems.

President Nixon (right) presenting the nation’s highest civilian award to the Apollo 13 crew (left to right, J. L. Swigert, F. W. Haise, J. A. Lovell) 

Credits: NASA

Indeed, NASA is trying to source additional plutonium 238 for its future deep space missions, the U.S. no longer produces the isotope and Russia has proved to be an unreliable source, but the useful life of the Apollo 13’s plutonium has expired.

The plutonium poses little danger to the environment: the corrosion resistant cladding should withstand seawater for approximately 870 years, ten times the plutonium’s half life.

According to NASA, the plutonium itself was in oxide form and was both chemically and biologically inert when it plunged into the ocean.

Over the years, the plutonium cask, far out of sight, has fueled two contradictory positions on the safety of RTGs for deep space missions.

For NASA, its safe return to Earth proved the effectiveness of their safety engineering. “We recognize that the Apollo 13 [RTG system] worked,” Dudzinski said. “Follow on RTGs were based on that design and improved on that design.”

Critics have taken different lessons from the untimely plunges of the RTGs. In 1997, a group of safety experts, including physicist Dr. Michio Kaku, warned that 32 kg of plutonium contained in the Saturn-bound Cassini satellite posed a greater danger than NASA would acknowledge, but ultimately, their warnings did not prevented the mission from happening.

Antarctic and Arctic sea-ice revealed in 1964 satellite maps

The NSIDC project examined almost 40,000 images from the Nimbus-1 archive to produce the September 1964 maps of Arctic (L) and Antarctic (R) sea-ice extent.

The earliest satellite maps of Arctic and Antarctic sea-ice have been assembled by scientists.

They were made using data from Nasa's Nimbus-1 spacecraft, which was launched in 1964 to test new technologies for imaging weather systems from orbit.

The satellite's old pictures have now been re-analysed to determine the extent of the marine ice at the poles in the September of that year.

Regular Earth Observation mapping from space did not begin until 1978.

One key finding is that marine floes around the White Continent in the 1960s were probably just as extensive as they are today.

The new snapshot, published in The Cryosphere journal, therefore helps put current ice conditions into a longer-term context, say researchers at the US National Snow and Ice Data Centre (NSIDC).

It is also just a fascinating story of how old scientific data can be given a new lease of life.

Matching up
The Nimbus-1 satellite was a short-lived mission that observed the Earth's clouds in black and white video, which it transmitted to the ground as an analogue TV signal.

Those transmissions were then photographed on to 35mm film and archived. The NSIDC team had to pull the canisters containing the original film out of storage to perform the re-analysis.

NSIDC
"The canisters were kind of forgotten, almost lost in time, until about four years ago when they were found and it was realised they might contain some useful, interesting data," explained the NSIDC's Dr Walt Meier.

"We then got some funding to digitise the data and analyse it. I was sceptical at first; the quality of the data is nothing like what we can get now.

Dr Walt Meier

"But it turned out to be really good, especially in the Antarctic, where it was surprisingly easy to determine the ice edge. Don't get me wrong, it was certainly a challenge," he told reporters.

"One of the things you have to do is geo-locate the data - you have to know where you are looking. There was some information in there to help us, but we had to take care in matching up the images and locating them on the Earth as accurately as we could."

Although the satellite worked for just three weeks, it covered a period of key interest to polar scientists.

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