Next week, rocket and space nerds around the world will celebrate an extremely obscure spaceflight anniversary. On July 13, 1948, Convair test fired its MX-774 rocket for the first time. Later renamed the Atlas, it was the rocket built by the US Air Force that took NASA into orbit with the Mercury program. But it was far from perfect. The Atlas had a nasty habit of blowing up. In fact, it's success rate was a little over 50 percent when John Glenn launched into orbit in 1962.
The Atlas was conceived in 1951 as part of a US Air Force program to study ballistic missiles. Announced in 1954, the Atlas became a top priority project in 1955 after intelligence reports that the Soviet Union was building intercontinental ballistic missiles (ICBMs) reached the US.Testing the Atlas began with just booster launches in 1957. On June 11, the first launch attempt at Cape Canaveral in Florida ended in disaster. The rocket exploded after launch at an altitude of just 10,000 feet. The second test that September didn't end any better. The rocket exploded and was destroyed. The third test in December was the first success – a 600 mile suborbital flight.Testing of the full rocket began in July 1958. The first launch was labeled "marginally successful." It was out of control during its flight, but at least all the system had worked and the test hadn't ended in an explosion.Propulsion failures dogged the next few tests, but it was clear that the Atlas was the only vehicle capable of launching a heavy payload, such as a manned spacecraft, into orbit. NASA knew that. Established on October 1, 1958, the space agency wasted no time in procuring Atlases from the US Army for its Mercury program.With manned orbital launches in its future, NASA tests of the Atlas joined the military launches for a formidable launch schedule in 1959. There were a number of successes, all suborbital, but there were an equal number of failures. Propellant feed failures, propulsions failures, electrical failures, hydraulic systems failures, and launch systems failures dogged Atlas tests throughout the year.
Within those failures was Big Joe, the first Atlas to fly as part of the Mercury program. Launched on September 9, 1959, it carried a boilerplate Mercury capsule with the goal of testing the capsule's heat shield. Fifty-eight seconds after launch, the vehicle exploded. It traveled a whopping 6 miles in that time. The cause was a structural failure.
The Atlas's thin skin was a huge problem during these early tests – it was so thin that the rocket risked collapsing under its own weight. When it wasn't fueled it had to be pressurized with nitrogen gas to stop it falling in on itself. The skin had to be strengthened before another Mercury launch. The capsule wasn't light, and that certainly didn't help structural problems.By the next launch on February 21, 1961, a stainless steel band had been added around the vehicle cushioned by a thin sheet of asbestos to reinforce the thin skin. It worked, and the second launch was a success. The third launch managed to put an unmanned Mercury capsule in low Earth orbit, as did the fourth. The fifth Atlas launched as part of the Mercury program carried the chimpanzee Enos into orbit. The sixth carried John Glenn.NASA's success with the Atlas belies the rocket's overall problems. In 1960 and 1961, all the Atlas tests – NASA and military launches taken together – yielded a success rate of just over 50 percent. Knowing the rocket's explosive history sort of gives a new appreciation for John Glenn's bravery at becoming the first American to ride the Atlas to orbit in 1962.The Atlas is still around; the Atlas V has launched a number of interplanetary missions in recent years. The modern incarnation blows up a lot less often than its predecessor.