La chienne Laika fut le premier être vivant à voler dans l'espace en novembre 1957 pendant quelques semaines. En janvier 1960, le chimpanzé Ham vole 8 minutes dans une cabine Mercury lancé par un Little Joe de Wallop island. La cabine est récupéré avec Ham par le destroyer Ellison dans l'océan Atlantique, avant qu'elle en chavire.

En août et décembre suivant, les soviétiques lancent deux vaisseau Korabl avec à bord deux chiennes Belka, Strelka et Pcholka et Mouchka. Au retour de Korabl-3, le vaisseau brûle avec à son bord les deux petits chiens. L'Accident qui ne serait pas intervenu s'il y avait eu un homme à bord, car il aurait débranché le système automatique.

En 1961, le singe Ham part dans Mercury MR2 le 31 janvier 1961 pour un vol de 16 mn. Après les vols suborbitaux de Shepard, Grisson et des premiers soviétiques Gagarine et Titov, le singe Enos part dans Mercury MA5 le 29 novembre pour un vol de 4 h 55 mn. Enos a résisté à une crête de 6.8g pendant l'accélération du propulseur-moteur et de 7.6g avec les précipitations du moteur et des groupes moteur.

Primate flights Little Joe 2 - 

December 4, 1959 - carried Sam the monkey to 85 kilometres in altitude The Little Joe 2 was an important test of the Mercury capsule because it was the first Little Joe animal flight, carrying the Rhesus monkey Sam (Macaca mulatta) close to the edge of space. He was sent to test the space equipment and the adverse effects of space on humans. His flight was launched December 4, 1959, at 11:15 from Wallops Island, Virginia, United States. The Little Joe 2 flew 55 miles (88 km) into space. It was recovered, with the monkey intact, in the Atlantic Ocean by USS Borie. Sam was one of a series of Monkeys in space. Sam was from the School of Aviation Medicine in San Antonio, Texas. Flight time 11 minutes 6 seconds. Payload 1,007 kg. The boilerplate Mercury spacecraft used in the Little Joe 2 mission , is currently displayed at Airpower Park and Museum, Hampton, VA.

Little Joe 1B 

- January 21, 1960 - carried Miss Sam the monkey to 14 kilometres in altitude The Little Joe 1B was a Launch Escape System test of the Mercury spacecraft, conducted as part of the U.S. Mercury program. The mission also carried a female Rhesus monkey (Macaca mulatta) named Miss Sam in the Mercury spacecraft. The mission was launched January 21, 1960, from Wallops Island, Virginia. The Little Joe 1B flew to an apogee of 9 miles (14.5 km) and a range of 12 miles (19.3 km) out to sea. Miss Sam survived the 8 minute 35 second flight in good condition. The spacecraft was recovered by a Marine helicopter and returned to Wallops Island within about 45 minutes. Maximum speed was 2,055 mph (3,307 km/h) and acceleration was 4.5 g (44 m/s²). Miss Sam was one of many Monkeys in space. Payload 1,007 kg.

Mercury-Redstone 2 (MR-2) est lancé le 31 janvier 1961 du LC 5. La cabine n°5 emporte le chimpanzé Ham pour un vol suborbital. Mercury SC 5 embarque 6 nouveaux systèmes qui n'ont pas encore volé, comme le système de contrôle environnemental, le système de contrôle d'attitude et de stabilisation, les rétro-fusées actives, le système de communication, le système de détection en vol et le sac pneumatique d'atterrissage. Le vol précédent MR1A a permit de faire culminer la cabine à 209 km d'altitude et la faire atterrir 378 km du Cap. MR 2 vise un apogée de 185 km et une distance franchissable de 467 km. 

6 chimpanzés, quatre femelles et deux males, 20 spécialistes médicaux et soigneurs de la base d'Holloman au Nouveau Mexique où les animaux ont été entraîné arrivent au hangar S du Cap Canaveral le 2 janvier 1960 pour préparer la mission. Les animaux sont entraînés durant trois semaines dans des simulateurs. Deux sont finalement sélectionnés le 29 janvier, Ham et sa doublure Minnie. Ham s'avère être plein d'énergie et plein d'humour. Ham de son vrai nom Chang n°65 vient du Cameroun en Afrique. Il a été acheté par l'USAF en juillet 1959.   

Le 31 janvier, Ham est installé dans la cabine à 12 h 53 TU. Le compte à rebours est interrompue pendant 4 heures avant la mise à feu. Finalement, le lanceur Redstone LV 3 décolle à 16 h 55 TU. Au bout de 2 minutes, l'accélération est de 17 g, l'unique étage du Redstone se sépare 17 secondes plus tard. La tour LES de la cabine est larguée. Elle vogue à 2300 m-s au lieu des 1970 prévus. Comme le pack de rétro-fusées a été largué avec la tour, sa vitesse ne peut être ralentie. Conséquence, la zone d'amerrissage est déportée de 209 km. Une défaillance sur une valve fait tomber la pression à bord de la cabine, mais Ham est vêtu d'un scaphandre autonome dans sa couchette. Le chimpanzé est en apesanteur durant 6 minutes au lieu des 5 prévues. La cabine rentre dans l'atmosphère à la vitesse de 9500 m-s, l'accélération est de 17 g  et amerrit à 679 km des cotés de Floride après un vol de 16 mn 30 s.

La cabine est récupéré à 18 h 52 mn TU. Suite au choc du bouclier thermique contre la cloison de l'habitacle, 365 kg d'eau se sont engouffrés dans la cabine. Ham est en parfaite santé lorsque l'écoutille est ouverte sur le porte avion Donner. En cadeau il reçoit une pomme et demi et une orange.

Ham avait 3 ans et 8 mois lors de son vol. Il est retirer de l'armée et envoyé au Zoo de Washington. Il y restera 17 ans avant de passer par la Caroline du Nord pour vivre en colonie dans un autre Zoo avec d'autres chimpanzés. Il mourra le 19 janvier 1983 à l'age de 25 ans. Il a été incinéré au International Space Hall of Fame d'Alamogordo, New Mexico. Minnie, son équiper de réserve a été la seule chimpanzé femelle entraînée pour un vol spatial. Elle est retourné au sein de l'USAF par la suite. Elle mourra le 14 mars 1998 à l'age de 41 ans. C'était le chimpanzé "astronaute" le plus vieux. 

A la suite des nombreux problèmes durant le vol, le Mercury Redstone ne sera pas utilisé pour un vol humain. MR3 est repoussé et remplacé par un vol test, Mercury-Redstone BD.

La cabine n°5 utilisé par Ham est maintenant exposée au California Museum of Science and Industry, Los Angeles, CA

Mercury-Atlas 5 - November 29, 1961 - carried Enos the Chimpanzee on a two orbit flight

By November 1961, the Soviets had launched two men into orbit and the United States still had not orbited a chimp. Some NASA leaders opposed the chimpanzee flight. NASA headquarters questioned the wisdom of MSC wasting time on another unmanned Mercury mission, when the Soviet's had already flown two successful manned orbital flights. NASA Headquarters Public Affairs Office finally issued the following statement, "The men in charge of Project Mercury have insisted on orbiting the chimpanzee as a necessary preliminary checkout of the entire Mercury program before risking a human astronaut."

The flight used Mercury spacecraft # 9 and Atlas # 93-D. On February 24, 1961 spacecraft # 9 arrived at Cape Canaveral. It took 40-weeks of preflight preparation. This was the longest preparation time in the Mercury program. The mission of spacecraft # 9 kept changing. It had been first been configured for a suborbital instrumented flight, then for a suborbital chimpanzee flight, then a three-orbit instrumented mission, and finally for the orbital flight that Enos flew.

MA-5 was planned as a close approximation of the upcoming MA-6 manned orbital mission. Mercury-Atlas 5 would be launched from Complex 14 at Cape Canaveral on a heading 72.51 degrees east of north. Orbital insertion of the Mercury spacecraft would occur 480 miles (722 km) from Cape Canaveral. The altitude would be 100 miles (161 km) and the speed would be 25,695 ft/s (7,832 m/s). Retrofire was planned to take place at 4 hours, 32 minutes, and 26 seconds after launch. The spacecraft would land 21 minutes and 49 seconds after retrofire. Reentry temperatures should reach 3,000 degrees F (1,650 deg C.) on the heatshield, 2,000 degrees F (1,095 deg C) on the antenna housing, 1,080 degrees F (582 deg C) on the cylindrical section, and 1,260 degrees F (682 deg C) on the conical section. The spent Atlas sustainer engine should reenter the atmosphere after 9 1/3 orbits.

On October 29, 1961, three chimps and 12 medical specialists moved into quarters at the Cape to prepare for the flight. The name given to "Enos," the chimp selected to fly the MA-5 mission, in Greek or Hebrew means "man". Enos's backups were (in order possible call-up) Duane, Jim, Rocky and Ham (the MR-2 veteran). Enos was from Cameroun, Africa, (originally called Chimp # 81), and was purchased by the USAF on April 3, 1960.

On November 29, 1961, about five hours before launch, Enos and his spacesuit-couch were inserted in the spacecraft. During the countdown, various holds took 2 hours and 38 minutes. Liftoff came at 15:08 UTC. The Atlas launched the MA-5 spacecraft into an orbit of 99 miles (159 km) by 147 miles (237 km).

The turnaround and damping maneuver consumed 6 pounds (2.7 kg) of the 61.5 pounds (27.9 kg) of control fuel aboard. The spacecraft used less fuel than the MA-4 did during the same maneuver. MA-5 assumed its planned 34 degree orbital attitude and after that, through the first orbit the thrusters used only 1.5 pounds of fuel to maintain a correct position.

At the end of the first orbit, ground controllers noticed the capsule clock was 18 seconds too fast. As it passed over Cape Canaveral a command was sent to update the clock to the correct time. The Mercury Control Center at Cape Canaveral received information that all spacecraft systems were in good condition.

Then as the MA-5 passed over the Atlantic tracking ship at the beginning of the second orbit, indications were received that inverter temperatures were rising. The environmental control system malfunction was also confirmed by Canary Island trackers. Abnormal heating had occurred on earlier flights, inverters had continued working or had been switched to standby in such cases. There was no alarm at Mercury Control. When the spacecraft reached Muchea, Australia, high thruster signals and capsule motion excursions were detected. Other data indicated that the 34-degree orbit mode was being maintained. When the MA-5 crossed the Woomera, Australia, tracking station, attitude control problems were not detected, so earlier reports were discounted.

As the MA-5 capsule reached the Canton Island station, Mercury Control realized that the attitude control system was malfunctioning. A metal chip in a fuel supply line had caused one of the clockwise roll thrusters to fail. The failed thruster allowed the spacecraft to drift from its normal attitude. This drift caused the automatic stabilization and control system to correct the spacecraft attitude. The spacecraft would swung back into the normal 34 degree orbital attitude, and the sequence would start again. The spacecraft repeated this drift and correction process nine times before retrofire. It did it once more between retrofire and the receipt of the 0.05 g (0.49 m/s²) light telemetry signal. The remaining thrusters used 9.5 pounds of fuel to keep the spacecraft properly aligned during the second orbit. Each loss of attitude cost over 1 pound (0.45 kg) of fuel as compared with the entire first orbit consumption of only 1.5 pounds (0.68 kg).

In addition to the attidude control problems, the environmental control system started having problems during the second orbit. The couch-suit circuit temperature rapidly rose from 65 to 80 degrees F (18 to 26 deg C.). This was an indication that the heat exchanger was freezing. The rise in suit temperature caused Enos' body temperature to rise to 99 F (37.2 deg C), then to 100 degrees F (37.8 deg C). The medical observers began to worry, about the chimp's condition. At 100.5 degrees F (38 deg C), his body temperature stabilized. This indicated that the environmental system had started to function again. The cooling system seemed to correct itself, but the attitude problems continued.

As the spacraft neared Hawaii on its second orbit, medical monitors were willing to let Enos continue the flight for a third orbit. Engineers were concerned, however, about fuel consumption. They worried that after a third orbit, there would not be enough fuel for attitude control during reentry.

Flight Director Christopher Kraft alerted the Hawaii controllers to be ready to initiate retrofire to bring the spacecraft down in the Pacific, if necessary. He also alerted controllers at Point Arguello, California, to be ready to initiate retrofire as MA-5 passed over their position. He allowed the spacecraft to continue to its normal second orbit, retrofire position near California. Twelve seconds before the retrofire point was reached for the normal second-orbit Atlantic primary recovery point, Kraft decided to bring Enos back to Earth. The chief flight controller at Point Arguello, executed the command.

There was one more attitude control excursion early in reentry, after that, the rest of reenty and recovery were uneventful. The destroyers Stormes and Compton and a P5M airplane were waiting for the spacecraft at Station 8, the predicted landing point. Three hours and 13 minutes after launch and nine minutes before splashdown, the aircraft spotted the spacecraft at an altitude of 5000 feet (1,525 m)descending on its main parachute. The information was relayed to the Stormes and the Compton, who were 30 miles (48 km) away. The spacecraft recovery aids, except for the sarah beacon, were functioning. During the descent, the airplane continued to circle and report landing events. It remained in the area until the Stormes arrived, an hour and 15 minutes after the landing. The Stormes hauled Enos and his spacecraft aboard. On the deck of the Stormes, the MA-5 hatch was blown explosively. It was released from outside the capsule by a pulling a lanyard. Blowing the hatch caused the spacecraft "picture" window to crack.

The spacecraft and Enos were both found to have survived the mission in good condition.

On Nov. 4, 1962, Enos died of dysentery caused by shigellosis, which was resistant to antibiotics of the time. He had been under constant observation for two months before his death. Pathologists at Holloman reported that they found no symptom that could be attributed or related to his space flight a year before.

The Mercury spacecraft had now been qualified to carry a human into orbit.

Mercury spacecraft # 9 used in the Mercury-Atlas 5 mission , is currently displayed at the North Carolina Museum of Life and Science, Durham NC