Project Mercury and the Sofar Bomb

Summary

The flight of Alan Shepard. Credit: NASAProject Mercury was supposed to be fast, and it was supposed to be simple. After all, Sputnik had made it starkly clear the Soviets were ahead, and America feared falling even further behind. The newly created NASA quickly struck back with Explorer 1, launched less than four months after Sputnik, but by then the Soviets had put a dog in space and everyone knew a human would be next. To have any hope of getting there first, Mercury had to be as fast and as simple as possible.Except, of course, that putting a man into space for the first time was anything but simple. First you needed a rocket, and the ones America had in 1959 still had a nasty habit of blowing up. Then you needed a capsule – and this was supposed to be dumb, just something a person could sit in for a few hours and sail safely through the vacuum of space. And then you needed to bring him back to Earth.For this last bit, America chose to use the oceans. To return to Earth, an orbiting capsule first needs to fire its thrusters, a burn that slows the capsule and drains it of the energy needed to remain in orbit. After that it will fall, and if you time the burn correctly, it will descend towards a chosen spot on the ground. Put that spot in the ocean, and things are simpler: water is more forgiving than solid rock, at least when it comes to things falling at high speed.But afterwards things can be complicated. A capsule must float; it must be able to survive waves and whatever else the weather throws at it; and it must be able to be found. And none of that is especially easy. In Project Mercury one of the capsules sank, a disaster which almost took an astronaut with it, and two others came down hundreds of miles off course, each invoking a search over vast stretches of the ocean.This was a time before the navigation systems we rely on today. There was no constellation of GPS satellites, and no network of relay satellites to transmit distress calls. The deep ocean wa...