Mercury BJ-1

Mission Objective:

• The objective of the Big Joe program was to test the Mercury spacecraft ablating heat shield. It was also the first Project Mercury flight using an Atlas booster. The nose-cone capsule for Big Joe had no retrorocket package. The inner structure held only a half-sized instrumented pressure vessel instead of a pressurized cabin contoured to the outer configuration. Built in two segments, the lower half by Lewis and the upper by Langley, the main body of the spacecraft replica was fabricated with thin sheets of corrugated Inconel alloy in monocoque construction. This model of the Mercury capsule had more than one hundred thermocouples around the capsule skin to register temperatures inside and under the heatshield, sides and afterbody. (Reference NASA SP-4201 p. 201)
• The Atlas 10-D was programmed to rise, pitch over horizontally to the Atlantic before it reached its 100-mile peak altitude, then pitch down slightly before releasing its corrugated nose cone at a shallow angle barely below the horizontal.

Mission details:

• The original launch date for Big Joe was July 4, 1959 but the launch date was postponed until min-August by the Air Force because the booster did not checkout out perfectly at first. Then it was put off until early September by Space Task Group (STG) engineers, who were working on instrumentation and telemetry problems. Finally, the count picked up on 9/8/59 when Atlas 10-D (the sixth of this model to be flight tested) stood on the launch pad with a Mercury capsule (minus its escape tower).
• About 2:30am a 19-minute hold in the countdown was called to investigate a peculiar indication from the Burroughs computer that was to guide the launch. A malfunction was found in the Azusa impact prediction beacon, a transponder in the booster. Since there were several redundant means for predicting the impact point, the trouble was ignored and the countdown resumed. Liftoff occured at 3:19am. EST.
• The Mercury capsule flew a 1,424 mile (2,292 km) ballistic flight to the altitude of 90 miles (140 km).
• About 7 hours after launch, the destroyer Strong reported that she had netted the boilerplate capsule intact.
• The capsule landed 490 n.m. short of the planned landing point and about midway between two destroyers. Two P2V′s received SARAH beacon indications and homed in on the capsule, sighting it at 3 hours and 31 minutes after lift off. They maintained surveillance of the capsule until the arrival of USS Strong DD 758, a Desflot Four destroyer, which recovered the capsule 7 hours and 54 minutes after lift off.
• The capsule was studied for the effect of re-entry heat and other flight stresses from its 13-minute flight. Since the data from Big Joe 1 satisfied NASA requirements, a second launch, Big Joe 2 (Atlas 20D), which had been scheduled for the fall of 1959, was canceled and the launch vehicle was transferred to another program.

Mission Highlights:

• The flight was both a success and failure, the heat shield survived reentry and was in remarkably good condition when retrieved from the Atlantic Ocean.
• The Atlas-D booster, however, failed to stage and separated too late from the Mercury capsule. The added weight of the booster engines retarded velocity by 3000 ft per second and the capsule separated from the booster 138 seconds too late. The impact point was 500 miles short. The boilerplate capsule was not equipped with a launch escape system.
• The Mercury spacecraft used in the Big Joe 1 mission is displayed at the National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Virginia.

Astrophilately covers:

Launch cancel Port Canaveral.

Mercury capsule returned to Port Canaveral, September 10, 1959. Credit: #403