The tragedy of the in capsule Apollo 1 fire in 1967 could have been avoided if the American space program adopted its first preference for a sea level pressure in-cabin atmosphere. But the parameters for 100 percent Oxygen at reduced pressure was already made for us, because the United States invented the nuclear bomb first.
Ironically, this is also the reason the Russians were able to put a man in space first.
The best optimal design for space cabin pressure is at sea level, at about 100 kPa, or 760 mmHg, with a 60 percent to 20 percent oxygen atmosphere. This also dictates a spherical capsule design, a condition ill-suited for the available hardware NASA had available to it.
The Russians, playing catch-up to our own nuclear weapons program, were building atom bombs that were huge compared to our more compact designs. And so when they considered the throw-weight necessary for their ICBMs, the Russians built large rockets. In comparison, the American Redstone and Atlas designs were compact enough to make an engineer at Honda weep.
Unfortunately, the Redstone did not have the diameter to support a spherical capsule. And the conical shell that eventually became the standard model for NASA's manned spacecraft could only be safely "inflated" at partial pressure, and in the Occam's Razor Keep-It-Simple-Stupid of high-technology, a simple atmosphere of 100 percent oxygen became the "bottle at the end of a hose" that kept weight, complexity and manual interaction to a level of efficiency that only an engineer could love. In comparison, pressure suit inflation pressure, the lowest pressure the human body can tolerate, is right around 27.5 kPa, or 200 mmHg.
So when it came time to put a man in space, Russia was the only nation with the monster rockets that could do the trick. Yuri Gagarin's April 12 launch in Vostok 1 beat the first U.S. launch of Alan Shepard by a month. And, to mirror the irony of the Apollo 1 accident, the same thing happened to the Russians in a pressure chamber a month before Gagarin's launch. A towel or rag came in contact with a hot plate, and in a full 100 percent oxygen atmosphere, even aluminum burns.
But it was the urgency between Cold War rivals that kept both societies competitive.
Engineering is always a compromise between safety and simplicity, redundancy and efficiency, ease of automation (of a complex system, the Russian preference), and the reliability of a manual one (reckoned at the astronaut's insistence).
Where NASA zigged, the Russians zagged. And it was a safe bet that a Soviet engineering design would be 90 degrees out of phase with NASA's. The Russian Orlon EVA spacesuit is entered through a door in the backpack. NASA's current spacesuit enters through a ring at the waist.
NASA designed the first U.S. space station vertically like a three story tower. The Soviets designed their Salyut, and subsequent Mir, horizontally like a house trailer. The Russian Soyuz T-series capsule, a brilliant design, is well over 40 years old. Americans tend to change aerospace designs the way some people change shoes. Russians prefer chemical rockets, American engineers seem in love with solid fuel boosters. The Russians made Venus their interplanetary landing zone. The Americans chose Mars.
Only occasionally does high technology dictate design. When American F-86 Saber pilots first spotted the Soviet MiG-15s over Korea in the early 50s, they were astonished to realize how similar both open-nosed jets were; the only major difference was that the Americans built the main wing root at the bottom of the fuselage, and the Russians fixed the wings through the center.
Today, the International Space Station and NASA's Space Shuttle (according to a 1988 manual) are pressurized a sea level pressure with a 21 percent oxygen, 79 percent nitrogen mixture.
Finally, there is a canard, perhaps not wholly apocryphal, about how American engineers spent hundreds of thousands of dollars to perfect a pen that could write in the weightlessness of Earth orbit. It's said that when an American engineer described the problem to his Russian counterpart during a conference, the Russian took slight alarm at the profligacy of the American program. Noting this, the American engineer asked, "So, what did you use?"
"Well," stammered the Russian in amazement, "we used a pencil."