BJ-1Big Joe 1 was a test of the ablation heatshield of the Mercury space capsule. The capsule was a replica fabricated from thin sheets of corrugated Inconel alloy in monocoque construction.
The boilerplate capsule had more than one hundred thermocouples attached around the capsule skin to register temperatures inside and under the heatshield and other places.
BJ-1 was launched on September 9, 1959. The Atlas 10-D booster was programmed to reach an altitude of 100 miles before releasing the capsule at a shallow angle barely below the horizontal. The two outboard booster engines of the Atlas failed to separate from the centerline sustainer engine after their fuel was exhausted. The added weight of the booster engines caused the booster to reach an altitude of only 95 miles but the test of the capsule's heatshield were successfully completed.