The Nimbus satellite program was an ambitious 20-year program designed to take weather forecasting, ozone analysis, sea ice measurement and global positioning technology into the space age. These second-generation satellites were used as both atmospheric data collectors and sensor test-beds, becoming the basis of nearly every earth-observing weather satellite launched over the subsequent forty years.
But not every launch was a success. The Nimbus B-1 rocket booster failed shortly after launch due to a malfunction in the guidance system, forcing operators to issue a self-destruct command just two minutes into the flight.
Critically, she carried a Radioisotope Thermoelectric Generator (RTG) to provide power generated from the decay of a plutonium 238 core, a type of radioactive isotope not used for either nuclear weapons or nuclear reactor fuel. The generator was destroyed, disconnecting the hardened battery casks and leaving them intact on the ocean floor. The casks were successfully recovered and redeployed on the subsequent Nimbus III mission.
I still have a number of remaining questions on this case; and I wish I had more time to chase down archival documents on what happened next. On one hand, this seems to be a case of a controlled failure. The launch itself was a bust, but the self-destruct command and robust design of the plutonium batteries went according to plan. The search and recovery operation for the batteries was similarly successful, but I can’t immediately find any details on how it was performed. Depth would have been the greatest consideration, as the waters between Jalama Beach and San Miguel island bottom out at 1,500 feet. Period divers were limited to 120 feet on air, 210 on mixed gas and 350 in hard-hat rigs. Any deeper than that and they would have had to use manned submersible systems like DSV Alvin or remotely-operated systems such as the ones used in the 1966 Palomares B-52 crash, where four nuclear weapons were lost and one recovered from waters over 2,500 feet deep.
So how did they find and recover these batteries? I don’t yet know, and the information isn’t easy to find. NASA responded to my inquiry with a form letter pointing me to online resources I’ve already checked. I’ve emailed a friend of mine at the Smithsonian Air & Space museum. He’s graciously reaching out to some of his NASA contacts, I’ll have to wait and see if anything comes out of it. For the moment this will remain in my “interesting but unexplored” file.