Project Mercury Quarterly Report #8 NASA MR-4 Gus Grissom Liberty Bell 7

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• published: 09 Oct 2012
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more at http://scitech.quickfound.net/astro/nasa_news.html "Quarterly progress report for Project Mercury: July, August, September 1961." Astronaut Gus Grissom witnesses the test of an explosive hatch, first used on his Liberty Bell 7 MR-4 flight, which blew accidentally after splashdown, resulting in the loss of the spacecraft (and near loss of the astronaut). Public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and 1-pass exposure & color correction applied (cannot be ideal in all scenes). The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original). PROJECT MERCURY PLAYLIST: http://www.youtube.com/playlist?list=PL_hX5wLdhf_JhjIwLJjL8MHIhHVJyMm0b http://en.wikipedia.org/wiki/Mercury-Redstone_4 Mercury-Redstone 4 was the second United States manned space mission, launched on July 21, 1961. The Mercury program suborbital flight used a Redstone rocket. The spacecraft was named Liberty Bell 7 piloted by astronaut Virgil I. "Gus" Grissom. It reached an altitude of more than 118.26 mi (190.32 km) and traveled about 300 mi (480 km)... Liberty Bell 7 Mercury spacecraft #11 was designated to fly the second manned suborbital flight in October, 1960. It came off McDonnell's St. Louis production line in May 1960. Spacecraft #11 was the first Mercury operational spacecraft with a centerline window. It was closer to the final orbital version than was Alan Shepard's Freedom 7. Dubbed Liberty Bell 7, it featured a white, diagonal irregular paint stripe starting at the base of the capsule and extending about two-thirds toward the nose, emulating the crack in the famed Liberty Bell in Philadelphia, Pennsylvania. The stripe is echoed on the left side of the mission insignia. Explosive hatch Spacecraft #11 also had a new explosive hatch release. This would allow an astronaut to exit the spacecraft quickly in the event of an emergency. Emergency personnel could also trigger the explosive hatch from outside the spacecraft by pulling on an external lanyard... The original side hatch was bolted shut with 70 bolts and covered with several spacecraft shingles, making it a slow process to open the original hatch. McDonnell engineers came up with two different quick release hatches for the Mercury spacecraft. One with a latch, used on Ham's (a chimp) MR-2 and Shepard's MR-3 missions. The other design was an explosive release hatch. The quick release latching hatch weighed 69 lb (31 kg), too much of a weight addition to use on the orbital version of the spacecraft. The explosive hatch design used the 70 bolts of the original design, but each quarter-inch (6.35 mm) titanium bolt had a 0.06 in (1.5 mm) hole bored into it to provide a weak point. A mild detonating fuse (MDF) was installed in a channel between the inner and outer seal around the periphery of the hatch. When the MDF was ignited, the resulting gas pressure between the inner and outer seal would cause the bolts to fail in tension. There were two ways to fire the explosive hatch during recovery. On the inside of the hatch was a knobbed plunger. The pilot could remove a pin and press the plunger with a force of 5 or 6 lbf (25 N). This would detonate the explosive charge, which would shear off the 70 bolts and propel the hatch 25 ft (7.6 m) away in 1 s. If the pin was left in place, a force of 40 lbf (180 N) was required to detonate the hatch. An outside rescuer could blow open the hatch by removing a small panel near the hatch and pulling a lanyard. The explosive hatch weighed only 23 lb (10 kg)... The Liberty Bell 7 was launched at 122036 UTC, July 21, 1961... Reentry presented no problem... Grissom asked the helicopters to begin the approach for pickup. He removed the pin from the hatch-cover detonator and lay back in the couch. "I was lying there, minding my own business," he said afterward, "when I heard a dull thud." The hatch cover blew away, and salt water swished into the spacecraft as it bobbed in the ocean. The Liberty Bell 7 began taking on water and was sinking fast. Grissom had difficulty recollecting his actions at this point, but he was certain that he had not touched the hatch-activation plunger... ...All the time he had been in the water he kept feeling air escape through the neck dam. The more air he lost, the less buoyancy he had. Moreover, he had forgotten to secure his suit inlet valve. Swimming was becoming difficult, and now with the second helicopter moving in he found the rotor wash between the two aircraft was making swimming more difficult. Bobbing under the waves, Grissom was scared, angry, and looking for a swimmer from one of the helicopters to help him tread water...