Unmanned american space flight tests

The unmanned flights used Little Joe, Redstone, and Atlas launch vehicles.^[128] They were used to develop the launch vehicles, launch escape system, spacecraft and tracking network.^[201] One flight of a Scout rocket attempted to launch an unmanned satellite for testing the ground tracking network, but failed to reach orbit. The Little Joe program used seven airframes for eight flights, of which three were successful. The second Little Joe flight was named Little Joe 6, because it was inserted into the program after the first 5 airframes had been allocated.^[217][160]

Mission	Launch	Duration	Objective	Result	Remarks[218]
Little Joe 1	August 21, 1959	20 s	Test of launch escape system during flight.	Failure	Due to an electrical malfunction, the escape tower ignited ½ hour before launch and took the spacecraft with it, leaving the rocket on the ground.[219]
Big Joe 1	September 9, 1959	13 m 00 s	Test of heat shield and Atlas/spacecraft interface	Success/Failure	Actually the first Mercury-Atlas flight.[128] Recovered byUSS Strong (DD-758) 2,407 km southeast of Cape Canaveral.[220] Altitude: 65 mi (105 km) Qualified ablative heatshield.[92]
Little Joe 6	October 4, 1959	5 m 10 s	Test of spacecraft aerodynamics and integrity	Partial success	No additional tests[221]
Little Joe 1A	November 4, 1959	8 m 11 s	Test of launch escape system during flight with boiler plate capsule	Partial success	The rescue tower rocket ignited 10 seconds too late.[222] Recovered by USS Opportune 11.5 mi (18.5 km) southeast of Wallops Island.[223]
Little Joe 2	December 4, 1959	11 m 6 s	Primate escape at high altitude	Success	Carried Sam, a rhesus macaque.[222] Recovered by USS Borie (DD-704) 194 miles (312 km) southeast of Wallops Island, Virginia; altitude: 53 mi (85 km).[224]
Little Joe 1B	January 21, 1960	8 m 35 s	Maximum-q abort and escape with primate with boiler plate capsule	Success	Carried Miss Sam[225] Altitude: 9 mi (15 km)
Beach Abort	May 9, 1960	1 m 31 s	Test of the off-the-pad abort system	Success
Mercury-Atlas 1	July 29, 1960	3 m 18 s	Test of Mercury spacecraft / Atlas combination	Failure	Collapsed and exploded while passing through max-q[226] To save weight, the airframe had been made thinner since Big Joe, which led to the collapse. The next Atlas was strengthened by a temporary solution while the rest were made from the same specifications as Big Joe[227]
Little Joe 5	November 8, 1960	2 m 22 s	First test escape system with a production Mercury spacecraft	Failure	The clamp holding the spacecraft was deflected by air pressure; due to this and an incorrect wiring, the escape tower ignited too early but failed to separate spacecraft from launch vehicle.[39] The clamp was subsequently tested by a rocket sled.[39] Altitude: 10 miles (16 km)[228]
Mercury-Redstone 1	November 21, 1960	2 s	Qualify production spacecraft at max-q	Failure	Engine shutdown caused by improper separation of electrical cables;[229] vehicle rose 4 in (10 cm) and settled back on the pad. The escape tower was jettisoned and parachutes deployed.[230]
Mercury-Redstone 1A	December 19, 1960	15 m 45 s	Qualify spacecraft / Redstone combination.	Success	First flight of Mercury / Redstone. Recovered by USS Valley Forge[231] Altitude: 130 mi (210 km)[97]
Mercury-Redstone 2	January 31, 1961	16 m 39 s	Carry the chimpanzee Ham on suborbital flight	Success	Recovered by USS Donner (LSD-20)[232] 422 miles (679 km) southeast of Cape Canaveral; altitude: 157 mi (253 km)[233]
Mercury-Atlas 2	February 21, 1961	17 m 56 s	Qualify Mercury/Atlas interface	Success	Recovered by USS Donner[234] 1,432 miles (2,305 km) southeast of Cape Canaveral.
Little Joe 5A	March 18, 1961	23 m 48 s	Second test of escape system with a production Mercury spacecraft	Partial success	Tower fired 14 seconds too soon; it failed to separate the spacecraft from the rocket.[235]
Mercury-Redstone BD	March 24, 1961	8 m 23 s	Redstone development test flight	Success	Last Redstone test flight. (BD: Booster Development)[236]
Mercury-Atlas 3	April 25, 1961	7 m 19 s	Orbital (upgraded from suborbital) flight with robot astronaut[237][238][n 27]	Failure	Was aborted when it did not go into orbit; boiler plate capsule recovered and reused in Mercury-Atlas 4[240]
Little Joe 5B	April 28, 1961	5 m 25 s	Third test of escape system with a production Mercury spacecraft	Success	Concluded Little Joe program
(May–July, 1961: manned suborbital flights)
Mercury-Atlas 4	September 13, 1961	1 h 49 m 20 s	Test of environmental control system with robot astronaut in orbit	Success	Completed one orbit and sent data to the ground; first orbital flight of the project.[241] Recovery by USS Decatur (DD-936) 176 miles (283 km) east of Bermuda.[242]
Mercury-Scout 1	November 1, 1961	44 s	Test of Mercury tracking network	Failure	Was aborted after malfunction of guidance system;[243] results of Mercury-Atlas 4 and Mercury-Atlas 5 were used instead[244]
Mercury-Atlas 5	November 29, 1961	3 h 20 m 59 s	Test of environmental control system in orbit with a primate	Success	Chimpanzee Enos completed a two-orbit flight, performing tasks of pulling a lever on a given signal.[245][n 28] Last Mercury-Atlas test flight. Recovery by USS Stormes (DD-780)[247] 255 miles (410 km) southeast of Bermuda.[248]