Mercury-Redstone 4

• 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 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. McDonnell Aircraft engineers devised two different quick release hatches for the Mercury spacecraft. The first had a latch, and was used on the chimpanzee Ham's MR-2 and Shepard's MR-3 missions. The second 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 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 away in one second. If the pin was left in place, a force of 40 lbf (180 N) was required to detonate the bolts. An outside rescuer could blow open the hatch by removing a small panel near the hatch and pulling a lanyard. The explosive hatch weighed . Window The new trapezoidal window on Liberty Bell 7 replaced the two side portholes that were on Freedom 7. The Corning Glass Works of Corning, New York designed and developed the multilayered panes that comprised the new window. The outer pane was thick Vycor glass. It could withstand temperatures of . The inner pane was made of three inner glass panels bonded to form a single inner pane. One panel was a thick sheet of Vycor, while the others were tempered glass. This new window assembly was as strong as any part of the spacecraft pressure vessel. Controls The manual controls of Liberty Bell 7 incorporated a new rate stabilization control system. This allowed fine control of spacecraft attitude movements by small turns of the hand controller. Previously a lot of jockeying of the device was needed to maintain the desired attitude. This rate damping, or rate augmentation system, gave finer and easier handling qualities and a redundant means of firing the pitch, yaw, and roll thrusters. Before the Mercury-Redstone 4 mission, Lewis Research Center and Space Task Group engineers had determined that firing the posigrade rockets into the booster-spacecraft adapter, rather than in the open, developed 78 percent greater thrust. This achieved a greater spacecraft-booster separation through a kind of "pop-gun" effect. By using this technique, the spacecraft separated at velocity of about rather than using the old procedure. The Mercury-Redstone 4/Liberty Bell 7 mission would take advantage of this new procedure. Additional hardware changes to Liberty Bell 7 were a redesigned fairing for the spacecraft-Redstone adapter clamp-ring and additional foam padding added to the head area of the contour couch. The fairing changes and additional foam were used to reduce vibrations the pilot experienced during the boost phase of flight. The spacecraft instrument panel was rearranged to provide a better eye scan pattern. ==Naming==

Captain Grissom dubbed his capsule "Liberty Bell 7", the seven in honor of the seven original astronauts selected for Mercury, a tradition inadvertently started by prior Mercury pilot, Alan Shepard, who incorporated the seven in "Freedom 7" as his spacecraft was factory model no. 7. The other astronauts liked the symbolism, and so each appended 7 to their spacecraft names as well. Grissom chose "Liberty Bell" due to the capsule's resemblance to a bell, and because it evoked the iconic Liberty Bell. Grissom went as far as having the Liberty Bell on the spacecraft complete with the crack that characterizes the real bell. This detail motivated a degree of teasing of Grissom after the spacecraft sank in the ocean at the end of its mission. ==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==

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. ==Timeline==