Sixty years ago today, on 31 January 1961, a young chimpanzee named “Ham” was launched into space aboard a tiny Mercury capsule. His suborbital flight, lasting only 16 minutes, was meant to clear the final hurdles before the launch of the United States’ first astronaut, Alan Shepard, later that spring.
It was hoped that America would put a man into space before the Soviet Union, but difficulties during Ham’s mission—including problems with his Redstone rocket and the unhappy chimp having to endure forces almost 15 times greater than terrestrial gravity during re-entry—led an increasingly nervous NASA and the Space Task Group (STG) to push for another unmanned test flight before entrusting the launch vehicle with a human crew member. In many ways, the unhappy voyage of Ham was a contributor to the United States losing out to Russia in the race to put a man into space.
The 83-foot-tall (25-meter) Redstone was a converted ballistic missile, capable of accelerating to around 2,100 mph (3,500 km/h), which lacked the impulse to achieve orbital velocity, but could at least reach the threshold of space. A descendent and direct outgrowth of Nazi Germany’s fearsome V-2 weapon, it had been utilized in the United States’ first live nuclear tests during Operation Hardtack in August 1958 and its impeccable record earned it the moniker “Old Reliable”.
Beginning the following year, it was extensively overhauled as man-carrying space rocket, with the implementation of an effective abort system, tougher propellant tanks and upgrades to components which might catastrophically fail. At liftoff, its A-7 engine—fueled by a mixture of ethyl alcohol and liquid oxygen, plus a hydrogen peroxide turbopump—could produce a thrust of 78,000 pounds (35,380 kg).
But its record, at first, seemed dicey. In November 1960, the Mercury-Redstone-1 (MR-1) mission flopped, literally, when a circuitry malfunction caused the booster to rise a few inches off the pad, before an engine shutdown command was automatically issued and it settled back onto its pedestal.
The Launch Escape System (LES) fired, as it should in such an on-the-pad emergency, rising to an altitude of 0.7 miles (1.2 km) and landing 1,200 feet (360 meters) downrange of the pad. Embarrassingly, though, as the smoke cleared, it became obvious that the LES had not pulled with it the unmanned Mercury capsule. Instead, the drogue parachute popped out of its nose, followed by the main canopy, then a cloud of green marker dye and finally an auxiliary chute. All fluttered to the ground.
Mercury astronaut Wally Schirra, watching the proceedings, described the fiasco as “a memorable day, especially for someone who likes sick jokes!”
“The press had a field day,” remembered Flight Director Chris Kraft. “It wasn’t just a funny scene on the pad. It was tragic and America’s space program took another beating in the newspapers and in Congress.” Astonishingly, the Redstone did not explode and remained upright. As such, it could be emptied of its propellants and readied for another mission. It flew MR-1 successfully—though not uneventfully—on 19 December. The Redstone’s engine cut off at a higher altitude than intended, pushing the Mercury capsule higher and achieving a splashdown in the Atlantic 20 miles (32 km) further downrange than anticipated.
The issue was related to an electrical wiring configuration issue, which was promptly resolved in readiness for MR-2, which would see three-year-old Ham ride the Redstone to the edge of space in January 1961. And if Ham’s flight went without incident, it was hoped, Alan Shepard might fly America’s first space mission as soon as March.
Ham was not the first animal to have been launched by the United States. A pair of Rhesus monkeys, named “Sam” and “Miss Sam”, hailed from the School of Aviation Medicine in San Antonio, Texas, and were launched atop Little Joe boosters in December 1959 and January 1960, respectively. Neither of their Mercury capsules reached space—Sam attained 54 miles (88 km), Miss Sam about 9.3 miles (15 km)—but the pair demonstrated that living creatures could survive a launch and return alive.
Ham’s name drew from the acronym for the Holloman Aerospace Medical Center, based at Holloman Air Force Base in New Mexico, which took responsibility for preparing the chimp for his mission. And the decision to fly chimps was taken in view of their close approximation to human behavior. A colony of six chimps (four females and two males), together with 20 medical specialists and handlers from Holloman, arrived at Cape Canaveral’s Hangar S in early 1961.
The chimps were split into two groups to prevent the spread of any contagion and were led through training exercises with the help of Mercury capsule mockups in their compounds. By the end of January, they had grown somewhat bored, but nevertheless were all experts at pulling levels and pushing buttons in the right order, receiving either banana pellets or mild electric shocks for doing the right (or wrong) thing.
The day before launch, James Henry of the Space Task Group (STG) and Holloman veterinarian John Mosely examined the six chimps and settled on a particularly frisky and good-humored male as the prime candidate, with a female as his backup. Both were put on low-residue diets, instrumented with biosensors and, early on the 31st, outfitted in space suits, placed in contoured couches and taken to the launch pad. With 90 minutes to go, Ham, described as “still active and spirited”, was inserted inside the MR-2 capsule.
His home for the 16-minute mission boasted a number of significant innovations, including an environmental control system, live retrorockets, a voice communications device and the accordion-like pneumatic landing bag. The latter was attached to the heat shield and shortly before splashdown, the pair would drop 4 feet (1.2 meters), filling with air to help cushion MR-2’s impact. In the water, the landing bag and heat shield were intended to serve as an anchor, keeping the spacecraft upright.
Ham’s liftoff at 11:54 a.m. EST was successful, although his Mercury capsule, programmed to travel 114 miles (183 km) into space and 290 miles (468 km) downrange, actually flew 42 miles (67 km) higher and 124 miles (200 km) further downrange than intended. The chimp experienced 6.5 minutes of weightlessness and endured 14.7 times the force of normal terrestrial gravity at one point during his re-entry.
He survived and seemed to be in good spirits, despite having to wait for several hours before being picked up by the dock landing ship U.S.S. Donner. After splashdown, his heat shield had skipped on the water, bounced against the capsule’s base and punched two holes in the pressure bulkhead. As MR-2 capsized, the open cabin pressure relief valve let in yet more seawater. Ham, however, seemed happy enough, gobbling down a pair of apples and half an orange on the recovery ship’s deck.
Post-flight analysis would reveal that the Redstone rocket’s mixture ratio servo control valve failed in its full-open position, causing early depletion of the liquid oxygen supply; consequently, the propellant consumption rate increased, the turbopump ran faster and led to higher thrust, an earlier-than-scheduled engine shutdown and the inadvertent ‘abort’ of the MR-2 spacecraft. Nonetheless, the basic controllability and habitability of Mercury was deemed a success.
In the wake of Ham’s flight, the reliability of the booster-capsule combination was reassessed, culminating in an estimated probability of success at somewhere between 78-84 percent. However, many components had been designed to parameters which exceeded those demanded by the STG and launch operations personnel had devised their own methods which were more conducive to flight success.
Taking this into account, the overall reliability of the system was judged at 88 percent for launch and 98 percent for the survival of the astronaut. These assurances were confirmed by one final test prior to Shepard’s mission—the Mercury-Redstone Booster Development (MR-BD) flight—launched on 24 March. As a result, Shepard’s flight was delayed to May and, as history went on to show, the United States lost out to the Soviet Union in achieving the first human space mission.
A furious Shepard summed up the general thinking in these high-stakes weeks of competition between the two superpowers. “We had ’em by the short-hairs,” he growled, “and we gave it away!”