Deep in the tunnel Barnes would come up against a last set of closed doors. When they opened, they revealed a succession of brightly lit rooms filled with desks. Barnes explains, “Moving closer to ground zero where the tunnel ended, we entered a large subterranean room stacked floor to ceiling with rows of electronic amplifiers, discriminator circuits, and multiplexing components and banks of high-tech equipment lining the walls.” Standing in front of the row of electronics was an engineer “usually with a cart full of electronic test equipment calibrating and repairing electronic circuits,” Barnes explains. These workers were all preparing for what was actually going on aboveground, and that was full-power, full-scale nuclear reactor engine tests. In order for NASA and the Atomic Energy Commission to be able to verify that NERVA could actually propel a spaceship filled with astronauts the 34 million to 249 million miles to Mars (the distance depends on the positions of the two planets in their orbits), those federal agencies had to witness NERVA running full power for long periods of time here on Earth first. To test that kind of thrust without having the engine launch itself into space, it was caged inside a test stand and positioned upside down.
For each engine test, a remote-controlled locomotive would bring the nuclear reactor over to the test stand from where it was housed three miles away in its own cement-block-and-lead-lined bunker, called E-MAD. “We used to joke that the locomotive at Jackass Flats was the slowest in the world,” Barnes explains. “The only thing keeping the reactor from melting down as it traveled down the railroad back and forth between E-MAD and the test stand was the liquid hydrogen [LH2] bath it sat in.” The train never moved at speeds more than five miles per hour. “One spark and the whole thing could blow,” Barnes explains. At ?320 degrees Fahrenheit, liquid hydrogen is one of the most combustible and dangerous explosives in the world. James A. Dewar, author of To the End of the Solar System: The Story of the Nuclear Rocket, gets even more specific. “One hundredth of what one might receive from shuffling along a rug and then touching a wall can ignite hydrogen,” Dewar wrote in 2004. To help visualize what the facilities aboveground at Jackass Flats looked like, Barnes likens them to Cape Kennedy. “Imagine a one-hundred-twenty-foot-tall aluminum tower rising up from a plateau of cement surrounded by a deep, concrete aqueduct. Add some huge, spherical thermos-like dewars sitting around, each containing something like two hundred and sixty thousand gallons of liquid hydrogen, and you can visualize the space-launch appearance of things,” Barnes explains. In Atomic Energy photographs from the 1960s, a single set of train tracks can be seen running along the bottom of the cement aqueduct and disappearing into an opening underneath the tall metal tower. “The railroad car carried the nuclear reactor up to the test stand and lifted it into place using remotely controlled hydraulic hands,” Barnes explains. “Meanwhile, we were all underground looking at the reactor through special leaded-glass windows, taking measurements and recording data as the engine ran.” The reason the facility was buried inside the mountain was not only to hide it from the Soviet satellites spying on the U.S. nuclear rocket program from overhead, but to shield Barnes and his fellow workers from radiation poisoning from the NERVA reactor. “Six feet of earth shields a man from radiation poisoning pretty good,” says Barnes.
When running at full power, the nuclear engine operated at a temperature of 2,300 Kelvin, or 3,680.6 degrees Fahrenheit, which meant it also had to be kept cooled down by the liquid hydrogen on a permanent basis. “While the engine was running the canyon was like an inferno as the hot hydrogen simultaneously ignited upon contact with the air,” says Barnes. These nuclear rocket engine tests remained secret until the early 1990s, when a reporter named Lee Davidson, the Washington bureau chief for Utah’s Deseret News, provided the public with the first descriptive details. “The Pentagon released information after I filed a Freedom of Information Act,” Davidson says. In turn, Davidson provided the public with previously unknown facts: “bolted down, the engine roared… sending skyward a plume of invisible hydrogen exhaust that had just been thrust through a superheated uranium fission reactor,” Davidson revealed. Researching the story, he also learned that back in the 1960s, after locals in Caliente, Nevada, complained that iodine 131—a major radioactive hazard found in nuclear fission products—had been discovered in their town’s water supply, Atomic Energy officials denied any nuclear testing had been going on at the time. Instead, officials blamed the Chinese, stating, “Fresh fission products probably came from an open-air nuclear bomb test in China.” In fact, a NERVA engine test had gone on at Area 25 just three days before the town conducted its water supply test.