Mercury-Redstone 4 was the second United States human spaceflight, on July 21, 1961. The suborbital Project Mercury flight was launched with a Mercury-Redstone Launch Vehicle, MRLV-8. The spacecraft, Mercury capsule #11, was nicknamed Liberty Bell 7. It was piloted by astronaut Virgil "Gus" Grissom.
The spaceflight lasted 15 minutes 30 seconds, reached an altitude of more than , and flew downrange, landing in the Atlantic Ocean. The flight went as expected until just after splashdown, when the hatch cover, designed to release explosively in the event of an emergency, accidentally blew. Grissom was at risk of drowning, but was recovered safely via a U.S. Navy helicopter. The spacecraft sank into the Atlantic and was not recovered until 1999.
Mission parameters
- Mass: 1 286 kg
- Maximum altitude: 190.39 km
- Range: 486.15 km
- Launch vehicle: Redstone rocket
Spacecraft
The MR-4 spacecraft, Mercury capsule #11, was designated to fly the second crewed suborbital flight in October 1960. It came off McDonnell's St. Louis production line in May 1960. Capsule #11 was the first Mercury operational spacecraft with a centerline window instead of two portholes. It was closer to the final orbital version than was Alan Shepard's Freedom 7. Dubbed Liberty Bell 7 by its pilot, 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.
Explosive hatch
thumb|upright|left|MR-4 Explosive Hatch Diagram (NASA)
Liberty Bell 7 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. Both the pop-off hatch and the lanyard are standard features of ejection seats used in military aircraft, but in the Mercury design, the pilot still had to exit the craft himself, or be removed by emergency personnel. The original exit procedure was to climb out through the antenna compartment, after removing a small pressure bulkhead. This was a difficult and slow procedure. Removal of an injured or unconscious astronaut through the top hatch would be nearly impossible. 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.
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-Redstone 4. John Glenn was the backup pilot for the mission.
Turning reluctantly to his dials and control stick, Grissom made a pitch movement change, but was past his desired mark. He jockeyed the handcontroller stick for position, trying to damp out all oscillations, then made a yaw movement and went too far in that direction. By the time the proper attitude was attained, the short time allocated for these maneuvers had been used, so he omitted the roll movement altogether. Grissom found the manual controls very sluggish when compared to the Mercury procedures trainer. He then switched to the new rate command control system and found perfect response, although fuel consumption was high.
After the pitch and yaw maneuvers, Grissom made a roll-over movement so he could see the ground from his window. Some land beneath the clouds (later determined to be western Florida around the Apalachicola area) appeared in the hazy distance, but the pilot was unable to identify it. Suddenly Cape Canaveral came into view so clearly that Grissom found it hard to believe that his slant-range was over . The Astronaut Office likely believed Grissom, since it maintained Grissom in the prime rotation spot for future flights, for example as the commander of the first Gemini flight, and the first planned Apollo flight.
In a 1965 interview, Grissom said that he believed the external release lanyard came loose, triggering the hatch release. On the Liberty Bell 7, this release lanyard was held in place by only one screw. This theory was accepted by Guenter Wendt, the Pad Leader for most early American crewed spaceflights.
During a launch simulation on Apollo 1 in 1967, the combination of a cabin fire and an inward-opening hatch contributed to the death of Grissom, as well as that of the astronauts Ed White and Roger B. Chaffee in a launch-pad fire. Use of an explosive hatch had been rejected following the discovery by engineers that an explosive egress system on a spacecraft could inadvertently fire without being triggered. Following the Apollo fire, Block II Apollo spacecraft were equipped with rapid-opening systems.
In 2021, analysis of video of the recovery suggested that static electricity may have caused the premature detonation of the hatch bolts. Helicopters are known to build up a charge of static electricity due to the rotors moving through the air. Marine Corps Lt. John Reinhard, the crewman aboard the helicopter who used a set of shears containing explosive charges to snip off the antenna on the floating spacecraft (to allow the helicopter to go lower) reported that "when I touched the antenna there was an arc, and both cutters fired. At the same time, the hatch came off. It could be that some static charge set [the hatch] off."
Recovery of Liberty Bell 7
thumb|upright|Liberty Bell 7 was recovered in 1999
thumb|right|The restored spacecraft is currently displayed at the [[Cosmosphere in Hutchinson, Kansas.]]
After several unsuccessful attempts in 1992 and 1993, Oceaneering International, Inc. lifted the Liberty Bell 7 off the floor of the Atlantic Ocean and onto the deck of a recovery ship on July 20, 1999, the 30th anniversary of the Apollo 11 lunar landing and a day shy of the 38th anniversary of the loss of the Mercury capsule. The team was led by Curt Newport and financed by the Discovery Channel.
The spacecraft was found after a 14-year effort by Newport at a depth of nearly , east-southeast of Cape Canaveral. Among the items found within were part of the flight gear and a large number of Mercury dimes which had been taken to space to be souvenirs of the flight. The spacecraft was then placed in a container filled with seawater to prevent further corrosion. The capsule's condition was consistent with what would have been expected from 38 years of lying in deep ocean water; the titanium hull and plastic components, all unaffected by salt water, survived basically intact while aluminum and steel components were extensively corroded and in some cases completely disintegrated--this included the steel instrument panels which were almost totally eroded away and their gauges and controls found lying in the astronaut's couch still attached to the wiring harnesses. Grissom's camera and its film rolls were recovered; the film was in poor condition and had no useable imagery in it. Also recovered were the astronaut's logbook, flashlight, survival knife, and 35 Mercury dimes. The Cosmosphere, in Hutchinson, Kansas, disassembled and cleaned the spacecraft, and it was released for a national tour through September 15, 2006. The spacecraft was then returned to the Cosmosphere where it is on permanent display. In 2016, it was temporarily lent to The Children's Museum of Indianapolis.
Dramatization in film
Philip Kaufman's 1983 film The Right Stuff includes a dramatization of the Liberty Bell 7 mission in which Fred Ward played Gus Grissom.
Additional fictional representations also occur in HBO's 1998 From the Earth to the Moon with Mark Rolston as Gus Grissom and 2016's Hidden Figures movie with Devin McGee as Gus Grissom.
thumb|128x128px|Mission insignia
Timeline
{| class="wikitable"
! T+ Time
! Event
! Description
|-
| T+00:00:00
| Liftoff
| Mercury-Redstone lifts off, onboard clock starts.
|-
| T+00:00:16
| Pitch program
| Booster (Redstone) begins pitching over at 2 deg/s from 90 deg to 45 deg.
|-
| T+00:00:40
| End pitch program
| Booster reaches 45 deg pitch.
|-
| T+00:01:24
| Max Q
| Maximum dynamic pressure ~575 lb<sub>f</sub>/ft² (28 kPa).
|-
| T+00:02:20
| BECO
| Booster engine cutoff. Velocity 5,200 mph (2.3 km/s).
|-
| T+00:02:22
| Tower jettison
| Escape tower jettison, no longer needed.
|-
| T+00:02:24
| Spacecraft separation
| Posigrade rockets fire for 1 s giving separation.
|-
| T+00:02:35
| Turnaround maneuver
| ASCS (Automatic Stabilization and Control System) system rotates spacecraft 180 deg, to heat shield forward attitude. Nose is pitched down 34 deg to retro fire position.
|-
| T+00:05:00
| Apogee
| Apogee of about reached, about downrange from launch site.
|-
| T+00:05:15
| Retrofire
| Three retro rockets fire for 10 s each. They are started at 5 s intervals, firing overlaps. Delta-V of is taken off forward velocity.
|-
| T+00:05:45
| Retract periscope
| Periscope is automatically retracted in preparation for reentry.
|-
| T+00:06:15
| Retro pack jettison
| One minute after retrofire retro pack is jettisoned, leaving heatshield clear.
|-
| T+00:06:20
| Retro attitude maneuver
| ASCS orients spacecraft in 34 deg nose down pitch, 0 deg roll, 0 deg yaw.
|-
| T+00:07:15
| .05 g maneuver
| ASCS detects beginning of reentry and rolls spacecraft at 10 deg/s to stabilize spacecraft during reentry.
|-
| T+00:09:38
| Drogue parachute deploy
| Drogue parachute deployed at slowing descent to and stabilizing spacecraft.
|-
| T+00:09:45
| Snorkel deploy
| Fresh air snorkel deploys at . Environmental control system switches to emergency oxygen rate to cool cabin.
|-
| T+00:10:15
| Main parachute deploy
| Main parachute deploys at . Descent rate slows to
|-
| T+00:10:20
| Landing bag deploy
| Landing bag deploys, dropping heat shield down .
|-
| T+00:10:20
| Fuel dump
| Remaining hydrogen peroxide fuel automatically dumped.
|-
| T+00:15:30
| Splashdown
| Spacecraft lands in water about downrange from launch site.
|-
| T+00:15:30
| Rescue aids deploy
| Rescue aid package deployed. The package includes green dye marker, recovery radio beacon and whip antenna.
|}
Cancellation of further suborbital missions
The original plan for Project Mercury was to fly four additional suborbital missions with the Redstone booster, numbered MR-5 through MR-8. John Glenn was tentatively assigned to fly MR-5. However, by the time of Grissom's flight, Project Mercury had fallen behind the original program timeline. Subsequently, NASA decided that it had accomplished all that could be accomplished with the suborbital flights, and there was also concern about falling behind the Soviet program. On August 18, NASA announced the cancellation of the remaining Mercury-Redstone flights, clearing the way for Glenn to fly a Mercury-Atlas mission as the first American to orbit the Earth.
Notes
References
- Mercury-Redstone 4 transcripts on Spacelog
- NASA MR-4 News Conference July 22, 1961, Cocoa Beach, FL
- Liberty Bell 7 Recovery Evaluation and Nondestructive Testing - NASA - December 1999 (PDF format)
External links
- Field Guide to American Spacecraft Pictures of Liberty Bell 7 on display after recovery and restoration.