How two monkeys, two chimps and a robot made Mercury possible

Today, February 20th, is the 50th anniversary of John Glenn's orbital spaceflight. In 1961, Glenn became the first American to orbit the Earth (three times!), which as far as I can tell, is why we're all taking the day off today. Such an achievement was one of the primary objectives of the Mercury Program, which preceded Gemini and Apollo.

While Glenn was most definitely the first American to orbit, his mission (Mercury-Atlas 6) was the twenty-first Mercury mission. Before NASA was ready to launch a human into space, it had to make sure that the rockets were safe, the space capsules were safe, and that space itself was safe (since we had no idea). And NASA had to be absolutely, positively sure, because if the agency got it wrong, it would have disastrous implications for the future of space exploration.

And so NASA tested everything out. Thoroughly. Before the agency ever sent a human to space, it had to get as close as it could get while not sending a human, and this means that the first American residents into space included two monkeys, two chimpanzees, and a robotic "crewman simulator." This is their story.

Many of the pictures in this post come from contemporary newspaper accounts via Google's newspaper archive, which you can access here.

The goal of the Mercury program was to put a human in orbit around the Earth, which is exactly what happened fifty years ago today. But the program itself began back in 1959, just a couple years after the Soviets launched the first satellite (Sputnik) and about the same time as the Soviet manned space program (Vostok) was getting underway.


Building The Rockets

We didn't have much to work with back in the late '50s: up until 1951, the United States was still using captured German V-2 rockets from World War II as research platforms, and it was only after we started physically running out of V-2s that the Army (this was before NASA) had to get serious about engineering some new hardware. Now, when we say "the Army," we're really talking about the Army's war prize, a German rocket design team, headed by Wernher von Braun. Using the V-2 as a template, the Germans created the Redstone, a surface-to-surface guided ballistic missile with a maximum range of about 200 miles. At the same time, the Air Force was working on their own "Americanized V-2," which came to be called the Atlas.


Neither of these programs was intended (at the start) to launch anything into space: in each case, the military was just looking for faster and more efficient methods of blowing things up far away. But by 1952, the National Advisory Committe on Aeronautics (the direct precursor to NASA) decided to make high speed and high altitude research a priority, and that meant both rocket-powered airplanes (most of the early X-planes got their start here) and, eventually, spacecraft.


The launch of Sputnik (humanity's first artificial satellite) by the Soviets on Aug. 26, 1957 really spurred things into high gear over here in the States, largely because nobody thought they'd actually be able to do it, and the achievement made it clear that the Soviets were substantially ahead of the U.S. when it came to both space technology and (more worryingly at the time) long-range ballistic missile technology. Embarrassed and a little freaked out, President Eisenhower signed the National Aeronautics and Space Act into law in July of 1958, and the newly-formed NASA wasted no time in outlining a plan to "at the earliest practicable date orbital flight and successful recovery of a manned satellite, and to investigate the capabilities of man in this environment."

It's important to stress how little was known about space and space travel at this point. There were real concerns about whether humans could function and survive in prolonged microgravity. For example, would humans be able to see? Breathe? Swallow? Would the radiation be too severe? And even the stuff that was known — that humans would need an air supply and a pressure suit and such — were still problems that needed to be tackled in the form of a space capsule. After much deliberation, NASA decided to let McDonnell Aircraft Corporation have a crack at the overall capsule design.


As far as the launching system, both Redstone and Atlas were ready to fly, but at $1 million and $2.5 million respectively, NASA couldn't afford to just launch them willy-nilly. Instead, it cobbled a bunch of solid rocket boosters together into a much bigger booster called "Little Joe," which could carry 4,000 pounds up over 100 miles high. At only $200,000 a pop, Little Joe rockets would form the backbone of the initial Mercury launch tests.

Sam The Monkey

Seeing as launching people on top of rockets was a brand new thing, one of NASA's priorities was to come up with a working escape system, and the first five launches of the Mercury program were largely devoted to making sure that this system (a top-mounted rocket that could pull the capsule clear in the event of a booster failure) worked like it was supposed to. Launch number six (aka "Little Joe 2") would be the first high-powered flight, and it would also be the first flight with a passenger inside the Mercury capsule: a little monkey named Sam.


Sam, a seven-pound, 30-month-old rhesus monkey came from the School of Aviation Medicine (get it?) in San Antonio, Texas. Before launch, Sam was acclimated to his launching system (a form-fitting acceleration couch made of foam), and trained to respond to a flashing red light by moving a lever similar to an airplane stick, the idea being to test whether or not he could perform basic tasks in microgravity. Sam was also wired up from head to toe with sensors to track his temperature, breathing and heart rate. And for what it's worth, Sam wasn't alone in his capsule: along with him were packets of barley seeds, nerve cells from rats and other tissue cultures, and insects, since military physicians wanted to see how weightlessness and radiation effected things like reproductive capacity.


The Little Joe rocket with Sam on board lifted off on Dec. 4, 1959, with Alan Shepard and Gus Grissom in attendance, understandably interested to see how well Sam would be able to handle weightlessness. The launch was flawless, and when the booster burned itself out at about 100,000 feet, the Mercury escape rocket fired as planned, boosting the capsule up to about 280,000 feet (53 miles). Sam experienced three minutes of weightlessness before the capsule reentered the atmosphere. 40 minutes after launch, Sam splashed down in the Atlantic.


It took six hours for a destroyer to find the Mercury capsule (floating 120 miles off the North Carolina coast) and get Sam out, but the monkey seemed no worse for wear. Reportedly, Sam "nibbled parts of an apple and an orange," "drank a little water," and "scratched himself vigorously." Impressed, the crew of the destroyer named him an honorary destroyermonkey right then and there. Later testing showed that Sam really was just fine, and to prove it, he went on to live until 1982 in retirement at a training colony.

Miss Sam, The Other Monkey

While Sam's flight had been an overall success, the test of the escape rocket hadn't been performed under what's called "max Q," which is the point at which a vehicle (like a rocket) experiences maximum stress. The escape system had to be relied on to work under the worst possible conditions, which meant another test, and another monkey passenger to make sure that an astronaut would be able to survive such a situation.


The second Mercury monkey was Sam's friend, named Miss Sam. Miss Sam's flight would be much shorter than Sam's, but also much more violent: the forces she would experience when the capsule ejected from the booster at max Q would be severe. Like Sam, Miss Sam was trained to pull a lever in response to a flashing light, and as the Little Joe rocket accelerated to 2,000 miles per hour after launch, she was doing fine. As the escape rocket fired, though, Miss Sam completely stopped responding for a period of about 30 seconds, suggesting that she'd been shaken up fairly badly. She seemed to recover, fortunately, and after a fast retrieval (just 45 minutes from launch to having her back on land), she was pronounced "frisky and full of the old Nick" (whatever that means) and had a big lunch of crackers and apples.


We should mention that neither Sam nor Miss Sam had to endure any more rocket rides. In fact, they were mated to each other to see if their offspring showed any long-term genetic repercussions from their parent's space travel, and so far, so good.

Up until this point, the Mercury flight tests had been conducted primarily with Little Joe rockets, but things were seeming to start to work together and it was time to kick it up a notch and start making tests with the more expensive (and more powerful) Redstone boosters as well as the much more expensive (and much more powerful) Atlas boosters. The first successful flight of a Mercury-Redstone took place in December of 1960, about a month after a comically short unsuccessful flight (the rocket lifted off a total of four inches) caused by an electrical malfunction.

Mercury-Redstone 2 was intended to be the final flight required to "man-rate" the capsule and launch vehicle, and the only way to do that was to send up something else alive. This meant another monkey, or more accurately, a chimpanzee. Chimps are large enough and intelligent enough to mimic human behavior, they have about the same reaction times as humans, their organ placement is the same, and there's a long medical research background on them, making them ideal proxies for astronauts.


Six "astrochimps" (as they were known) were brought to Cape Canaveral from Holloman Aerospace Medical Center in New Mexico to prepare for the MR-2 mission. The chimps were trained in Mercury capsule simulators to perform similar tasks to Sam and Miss Sam: pulling levers in response to flashing lights. Specifically, the chimps had both continuous and discrete tasks to perform: one lever had to be pushed every 15 seconds, while another lever had to be pushed within five seconds when a blue light came on, which happened about once every two minutes. After three weeks of work (the chimps got banana pellets for success and mild electrical shocks on the bottom of their feet if they failed), the astrochimps were bored, well-fed, lever-pulling experts.


Ham The "Astrochimp"

One of these chimps was named Ham (guess where he got that name from). Ham had been born in Cameroon, captured by animal trappers, and sent to Florida, where his handlers called him Chop Chop Chang. When he entered the astrochimp program, he was known officially as No. 65, since NASA didn't want to publicly announce his name in the event that something went wrong. Ham was three years old at the time of the MR-2 mission, and the morning of the launch, he was "exceptionally frisky and in good humor," which is why he was chosen to go.


A few hours before launch, Ham was fitted with sensors, put into a space suit, and set up in his own little acceleration couch inside a pressurized cabin. This "biopack" was placed inside the Mercury capsule at 7:53am on Jan. 31, 1961. A series of complications resulted in a delay of almost four hours (which Ham gamely waited out inside the capsule), but five minutes before noon, the MR-2 Redstone ignited and Ham lifted off towards space.

Almost immediately, things started to go wrong. The flight path angle began to rise, and low fuel pressure caused the capsule to separate from the booster earlier than planned, triggering the escape rocket, which boosted the capsule's speed to 5,800 mph instead of the planned 4,400 mph (putting about 18 g on Ham). Because of the extra thrust, the capsule reached almost 160 miles of altitude instead of 115. And two minutes into the flight, the pressure in the Mercury capsule lost cabin pressure completely. Fortunately, Ham was well-protected inside his capsule and space suit, which kept pressure and temperature comfortable.

The increased speed and higher altitude of MR-2 meant that Ham would land long, outside of the immediate recovery area, and when the abort rocket fired, the retrorocket pack (that would have slowed the capsule down before reentry) jettisoned prematurely, meaning that the forces on reentry would be more severe. Ham experienced nearly 15 g on the way back down to Earth, a full 3 g more than he was supposed to. When the capsule splashed down into the water, the same issue that let all the air pressure out in space started to let water in, and by the time a helicopter managed to get to it, The Mercury capsule had taken on 800 pounds of seawater and was nearly submerged.


Despite all of these problems, Ham made it through in good condition. He was dehydrated, and his nose was bruised, and according to one observer he was crying while crewmen on the recovery ship worked to get him out of the capsule, but but he seemed happy to be home, accepting an apple and a banana (which hadn't been allowed pre-mission) and shaking hands with the commander of the recovery ship. It was only five days later at a press conference that Ham revealed how unpleasant his trip had been: "the normally cheerful chimp balked, screeched and hugged his handler's neck when two veterinarians tried to insert him into a metal couch similar to the one he rode on his daring space flight. The handlers finally gave up, and Ham resumed clowning and mugging for the... cameramen and reporters." Clearly, Ham had had enough of that sort of thing.


After a bunch more medical testing (and a standby slot on one more mission) Ham was sent to the National Zoo, and then to the North Carolina Zoo, where he died in 1983. The Smithsonian Institution put his body into a Dermestid beetle colony, and the bugs ate all of the soft tissue, leaving just Ham's skeleton. The skeleton was given to the Armed Forces Institute of Pathology (where it still is), and the leftover bits were buried at the International Space Hall of Fame in New Mexico.

Ham's flight proved that it would be possible for a human to survive being launched into space, perform tasks while weightless, and land safely. But the MR-2 flight was by no means smooth, and while an astronaut probably would have come through it just as well as Ham had, NASA was still not ready to call its capsule "man-rated," primarily because of its lack of faith in the reliability of the Redstone and Atlas boosters. It scheduled an interim Redstone test for March of 1961 to try and fix the problems, and that seemed to work, meaning that the first manned launch could at last be scheduled with confidence.


But, it was too late to beat the Soviets. On April 12, the USSR launched Vostok 1, and Yuri Gagarin became the first man not just in space, but also the first man to orbit the Earth. The Vostok capsule was huge, weighing over 10,000 pounds, three times more than the Mercury capsules, and it traveled higher and faster in its single orbit than Mercury planned to. Americans (including Congress) were not pleased.

There was still some hope that it might be possible to orbit an American two or three times around the Earth to sort of do something more impressive than the Soviets had done, but the first step was still to get a human into space on a rocket, period. That happened on May 5, when Alan Shepard became the first American to make a suborbital flight into space. The Mercury-Redstone vehicle flew like a champ, and the 15-minute flight took Shepard up to 116 miles. Gus Grissom made a similar flight two months later using a Redstone booster, but in order to make it into orbit, it was time to upgrade to the Atlas.


But again, it was too late to beat the Soviets. Cosmonaut Gherman Titov in Vostok 2 spent an entire day in space from August 7 to August 8, completing 17 orbits. NASA scrapped the idea of any more suborbital flights, and began to focus on man-rating the Mercury-Atlas combination. Before even sending a chimpanzee into orbit, NASA decided to try the spacecraft out with a robotic "crewman simulator" instead.


Robonaut's Distant Ancestor

We probably wouldn't call this "crewman simulator" a robot today, but it was intended to do just about everything a human would do short of controlling the spacecraft itself. It breathed, turning oxygen into carbon dioxide and water at a rate similar to a human. It created a human-like body temperature. And thanks to a couple tape recorders, NASA could carry on a conversation (or at least hear what it was saying) from the ground. The flight was a success, showing that we had the capacity to get a human into orbit, keep them alive, and bring them back safely. The only question now was whether the next Mercury orbital flight would carry a man or a chimpanzee.

NASA felt that while a robot proving that a single orbit flight was possible was all well and good, it was necessary to do a full three-orbit flight with a chimp before sending a human up for a similar mission. Or at least, some people at NASA felt that way. There was a lot of pressure to get an American into orbit as quickly as possible, but around that time was the first test of the mighty Saturn I rocket in October of 1961, which handily distracted the public from Mercury (at least for a little bit) and the Mercury-Atlas 5 mission could continue with a chimp aboard as planned.


Enos, Who Paved The Way

The chimp selected for the MA-5 mission was named Enos, which is the Greek Hebrew word for "man." Enos, who came from Cameroon, was described by the chief veterinarian on the mission as "quite a cool guy and not the performing type at all," in contrast to many of the other chimps in the program, who had circus training. Like Ham, Enos would have work to do while in orbit, but compared to Enos, Ham had it easy. Enos would have to master four separate lever and light problems of increasing complexity:

"Problem one would offer right- and left-hand levers that Enos could use to turn off lights, avoiding a mild shock in the left foot (the same as for Ham). The second problem planned was a delayed-response experiment. Twenty seconds after a green light would appear on the panel, Enos would have to press a lever to receive a drink of water. Although there would be no penalty for his failure to respond, if the chimpanzee should pull the lever too early the problem would simply recycle and he would receive nothing. The third, a fixed-ratio problem, would involve pulling a lever exactly 50 times to receive a banana pellet. This would also be voluntary and without penalty. Chimpanzee intelligence would be tested in the fourth. Three symbols - circles, triangles, and squares - would appear in various two-of-a-kind combinations, with the task being to pull a lever under the odd symbol to avoid a mild shock. Lack of response during rest periods would give the indication that the animal was well oriented to his spacecraft environment."


Enos was put into his spacesuit and acceleration couch on Nov. 29, 1961. The countdown was uneventful except for an incorrectly positioned switch in the cockpit of the capsule that someone had to open the hatch to go fix, and some people in mission control joked that Enos had talked to Ham and flipped the switch himself because he didn't want to go. But go he did, surviving the seven or eight gees of acceleration with no trouble at all. The Atlas booster behaved itself, and after a good orbital insertion, Enos had a couple hours in which to work his control panel. He did very well, except for the fourth problem (the one with the symbols), where a malfunction caused the levers to give out shocks even when the chimp gave the right answer. Poor Enos gave himself about 40 shocks in a row during these test sessions, but he still kept on doing his job. Most importantly, he was eating and drinking freely, proving that it was possible to swallow in space.


The Mercury capsule was brought back to Earth after two orbits instead of three due to some thruster malfunctions which caused the capsule to lose attitude control, but NASA felt that if an astronaut had been aboard, they would have been able to compensate by hand and continue the mission.

When Enos was brought out onto the deck of the recovery ship, he reportedly jumped for joy and ran around shaking everyone's hand and then devoured two apples and two oranges, his first fresh food since he'd been put on a low-residue diet of pellets to prepare him for launch. Enos didn't have the same gregarious temperament as Ham, though, and he remained shy and quiet in front of reporters, and in any case, since the next mission promised to have a human on board, Enos' achievement was to be rapidly eclipsed. He retired to Holloman Air Force Base (along with Ham and the rest of the space monkeys), and died from dysentery in 1962.

A Manned Future

Enos and Mercury-Atlas 5 served as a dress-rehearsal for the Mercury-Atlas 6 mission, which took John Glenn into orbit fifty years ago today. The MA-6 launch went flawlessly, but after just one orbit, Glenn's spacecraft began to yaw to the right due to a faulty reaction jet. It was just this sort of problem that had forced NASA to end Enos' mission early, so this was the big moment: would a human astronaut be able to do what monkeys, robots and apes could not? Could Glenn use his training and experience to take over from automatic systems and justify the effort of making the space program all about humans? A newspaper article just before the mission summed it up thusly:

"If Marine Lt. Col. John H. Glenn Jr, 'flying' a Mercury satellite in orbit, does better than Enos the chimpanzee did last November, man will play a more important role in the trip to the Moon, in space exploration generally and in future military operations in nearby space.

If Glen does not perform as well as Enos, then the scientists who favor machines over men may win their point. Man may turn out to be little more than a 'big white rabbit' on space trips. He'll be carried along for the ride while electronic gadgets do the seeing, the 'thinking,' the guiding and the work.

The betting at the National Aeronautics and Space Administration right now is that man- that is Glenn- will win out during the orbital trip today.

But there is a strong group of scientists at the Pentagon and at NASA who feel that man is too slow, unreliable and inefficient. They believe automated equipment should do all the work and that if man is along he should be kept out of the way."

The answer, of course, was a resounding yes. Humans were worth it. Glenn performed brilliantly, and he was able to successfully pilot the capsule by hand, something that neither Enos nor any automatic system was capable of at the time. He completed three orbits, and returned to Earth to a hero's welcome.


This was not the end of the Mercury program. There were three more Mercury-Atlas launches all the way through May of 1963, sending up Scott Carpenter, Wally Schirra, and finally Gordon Cooper for 22 orbits. In May of 1961, President Kennedy Apollo program to take us to the moon, and up through December of that year, the follow-up the Mercury program was still being called Mercury Mark II. But in January, it was re-christened as Project Gemini, and over the next five years, Gemini would lead us to Apollo and the moon.

If you're interested in even more detail (!) about Project Mercury, you can read "This New Ocean: A History of Project Mercury," part of the NASA History series, online here.


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