His lab took off. Shop mechanics built test chambers from old airplane parts. He hired a scientist from Harvard, a PhD named John “Bill” Heim. Using volunteer test subjects, Heim and Armstrong gathered data on how the body responds to speed, lower oxygen levels, and decompression sickness and extreme temperatures. But it was an experiment on himself, with a rabbit on his lap, for which Armstrong became legendary.
He had been wondering what really happened to the human body above 10,000 feet. Why, and at what specific height, would a man die? Armstrong climbed into the low-pressure chamber with the rabbit on his lap. His technician adjusted the pressure to simulate high altitude. Armstrong’s chest began to tighten and his joints hurt. When he rubbed his hands, he felt tiny bubbles along his tendons, ones that he could move around under his skin. He surmised that these were nitrogen bubbles forming in his blood and tissues, and that death at high altitude was caused by blood clotting. Armstrong indicated to the technician that he should simulate an even higher altitude inside the chamber. He was wearing an oxygen mask, but the rabbit on his lap was not. Soon the rabbit would be dead. As the lab technician raised the pressure, the rabbit convulsed and died. When Armstrong got out of the chamber, he dissected the rabbit and found nitrogen bubbles, proving that his hypothesis was correct.
Armstrong’s discovery gave way to a major milestone in aviation medicine. Working with Heim on more tests, he inserted a viewing tube into the artery of a test animal. The two men took data on what happens to a mammal’s body at forty thousand, fifty thousand, and finally sixty-five thousand feet. They were the first to witness that body fluids boil at sixty-three thousand feet. This point would become known as the Armstrong line. This is the altitude beyond which humans cannot survive without a pressure suit.
In 1937, Captain Harry Armstrong was considered one of America’s aviation medicine pioneers. On October 2 of that year he attended the Aero Medical Association’s first international convention, which took place in the Astor Gallery of the Waldorf-Astoria hotel. There, he and Heim reported the results of their recent studies at Wright Field. One of the doctors most interested in these studies was the Luftwaffe physician representing Germany, Dr. Hubertus Strughold. The two men, Armstrong and Strughold, were pioneers in the same field. “We hit it off immediately,” remembered Harry Armstrong decades later. That fortuitous meeting would profoundly shape Strughold’s post-Nazi career.
Some men claim to be shaped by a single event. For Hubertus Strughold, it was watching Halley’s Comet streak across the sky from his backyard tree house in Westtünnen, Germany, in 1910. Forever after, said Strughold, he became preoccupied with what lies above. That same year, a second event shaped the rest of his life. Strughold watched a solar eclipse through a viewing glass and nearly went blind. The lens wasn’t as dark as he thought it was and he burned the retina of his right eye, causing permanent damage. “When I looked at somebody with the right eye, at his nose, he had no nose.… When I looked at somebody at the street, at a distance of about a hundred meters at somebody’s head [with the right eye], he did not have any head. It was always clear with both eyes,” Strughold later explained. Hubertus Strughold had learned the hard way that experiments using one’s own body could be dangerous. Still, as a young man, he pursued auto-experimentation with vigor and imagination. In college he studied physics, anatomy, and zoology, but it was physiology that interested him most, the functions of living organisms and their parts.
At the University of Würzburg Strughold taught the world’s first college course on the effects high altitude had on the human body. His experimental test data came from himself. On weekends he flew hot air balloons, recording everything from vision to ear pressure to muscle effects. Inside the flying balloon, Professor Strughold recorded how his body responded to rapid acceleration and descent, which in turn made him curious to know how he would feel during radical banking turns. For that he needed an airplane. Strughold found the perfect mentor in a World War I flying ace by the name of Robert Ritter von Greim.