Mercury-Redstone 4 - Mission Description

Mission Description

In January, 1961, NASA's Director of the Space Task Group, Robert Gilruth, told Gus Grissom that he would be the primary pilot for Mercury 4. John Glenn was the backup pilot for the mission.

Redstone launch vehicle MRLV-8 arrived at Cape Canaveral on June 8, 1961. A mission review on July 15, 1961, pronounced Redstone MRLV-8 and Mercury spacecraft #11 ready to go for the Mercury 4 mission.

Also, on July 15, 1961, Gus Grissom announced he would name Mercury 4, Liberty Bell 7. Grissom said the name was an appropriate call-sign for the bell-shaped spacecraft. He also said the name was synonymous with "freedom". As a tribute to the original Liberty Bell, a "crack" was painted on the side of the spacecraft.

The Mercury 4 mission was planned as a repeat of MR-3. It was to reach an apogee of 116 mi (187 km). The planned range was 299 mi (481 km). Grissom would experience a maximum acceleration of 6.33 g (62 m/s²) and deceleration of 10.96 g (107 m/s²).

The launch of Liberty Bell 7 was first planned for July 16. The cloud cover was too thick and the launch was postponed until July 18. On July 18, it was again postponed due to weather. Both times, the pilot had not yet boarded the spacecraft. On July 19, 1961, Grissom was aboard the Liberty Bell 7 when the flight was delayed again due to weather. At that point, it had just 10 minutes 30 seconds to go before launch.

On the morning of July 21, 1961, Gus Grissom entered the Liberty Bell 7 at 8:58 UTC and the 70 hatch bolts were put in place. At 45 minutes prior to the scheduled launch, a pad technician discovered that one of the hatch bolts was misaligned. During a 30 minute hold that was called, McDonnell and NASA Space Task Group engineers decided that the 69 remaining bolts should be sufficient to hold the hatch in place and blow it at the appropriate time. The misaligned bolt was not replaced.

The Liberty Bell 7 was launched at 12:20:36 UTC, July 21, 1961.