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Mercury Series

Virgil "Gus" Grissom

Flight - 16 Minutes

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MR-4 (19)

Liberty Bell 7
Pad LC-5 ()
Redstone (6)



Virgil I "Gus" Grissom


Backup Crew:

John H. Glenn, Jr.



3/7/61 - Spacecraft delivered to Hanger S CCAFS



Spacecraft # 11, Launch Vehicle S/N MR-8


Mission Objective:

Mercury-Redstone 4 was the fourth mission in the Mercury-Redstone series of flight tests and the second U.S. manned suborbital spaceflight. It was the next step in the progressive research, development and training program leading to the study of man's capabilities in a space environment during manned orbital flight.


The main objective was to corroborate the man-in-space concept. The main configuration differences between the MR-3 spacecraft was the addition of a large viewing window and an explosively actuated side hatch.


The addition of the large viewing window was a result of a change requested by Mercury astronauts. This window allowed the astronauts to have a greater viewing area than the original side port windows. The field of view was 30 degrees in the horizontal plane and 33 degrees in the vertical. The window is composed of an outer panel of 0.35-inch thick Vycor glass and a 3-layer inner panel.


The explosively actuated side hatch was used for the first time on the MR-4 flight. The mechanically operated side hatch on the MR-3 spacecraft was in the same location and of the same size but was considerably heavier (69 pounds rather than 23 pounds). The explosively actuated hatch utilizes an explosive charge to fracture the attaching bolts and thus separate the hatch from the spacecraft. Seventy 1/4-inch titanium bolts secure the hatch to the doorsill. A 0.06-inch diameter hole is drilled in each bolt to provide a weak point. A mild detonating fuse (MDF) is installed in a channel between an inner and outer seal around the periphery of the hatch. When the MDF is ignited, the resulting gas pressure between the inner and outer seal causes the bolts to fail in tension. The MDF is ignited by a manually operated igniter that requires an actuation force of around 5 pounds, after the removal of a safety pin. The igniter can be operated externally by an attached lanyard, in which case a force of atleast 40 pounds is required in order to shear the safety pin.



July 21, 1961. 7:20 a.m. EST. The launch was originally scheduled for July 18, 1961 but was rescheduled to July 19, 1961 because of unfavorable weather conditions. The launch attempt on July 19, 1961 was canceled at T-10 minutes as a result of continued unfavorable weather. The launch was then rescheduled for July 21, 1961. The first half of the split launch countdown was begun at 6:00am EST on July 20, 1961 at T-640 minutes. Spacecraft preparation proceeded normally thru the 12-hour planned hold period for hydrogen peroxide and pyrotechnic servicing. Evaluation of the weather at this time proved favorable and a go was given to pickup the second half of the countdown at 2:30am EST on July 20, 1961. At T-180 minutes, prior to liquid oxygen loading, a planned 1-hour hold was called for another weather evaluation. The evaluation was favorable and the count proceeded at 3:00am EST. At T-45 minutes a 30 minute hold was called to install a misalined hatch bolt. At T-30 minutes, a 9-minute hold was called to turn off the pad searchlights which interfered with launch telemetry during launch. At T-15 minutes, a 41-minute hold was called to await better cloud conditions. The count then proceeded from T-15 until liftoff. Gus Grissom was in the spacecraft 3 hours and 22 minutes prior to launch.
The spacecraft was delivered to Hanger S at Cape Canaveral, Fl on March 7, 1961. Upon delivery, the instrumentation and selected items of the communication system were removed from the spacecraft for bench testing. After reinstallation of the components, the systems test proceeded as scheduled. Those tests required a total of 33 days during which the electrical, sequential, instrumentation, communication, environmental, reaction-control, and stabilization and control systems were individually tested. After system tests, the landing impact bag was installed and then a simulated flight was run on the spacecraft. Then the parachutes and pyrotechnics were installed and the spacecraft was weighed, balanced and then delivered to the launch complex. Twenty-one days were spent on the launch pad.




Altitude: 118.3 statute miles
Orbits: 0
Duration: 0 Days, 0 hours, 15 min, 37 seconds
Distance: 302 statute miles
Velocity: 5,134
Max Q: 610 psf
Max G: 11.1



Atlantic Ocean, 302 miles East of launch site. Drouge parachute was deployed at T+9 minutes 41 seconds and main parachute at T+10 minutes 14 seconds. Landing occured at T+15 minutes 37 seconds.

Mission Highlights:

The MR-4 flight plan was very much the same as that for MR-3. The range was 262.5 nautical miles, the maximum altitude was 102.8 nautical miles, and the period of weightlessness lasted for approximately 5 minutes.


At T-35 seconds, the spacecraft umbilical was pulled and the periscope was retracted. During the boosted phase of flight, the flight-path angle was controlled by the launch-vehicle control system. Launch-vehicle cutoff occurred at T+2 minutes 23 seconds, at which time the escape tower was released by firing the escape and tower jettison rockets. Ten seconds later, the spacecraft-to-launch-vehicle adapter clamp ring was separated, and the posigrade rockets fired to separate the spacecraft from the launch vehicle. The periscope was extended; the automatic stabilization and control system provided 5 seconds of rate damping, followed by spacecraft turnaround. It then oriented the spacecraft to orbit attitude of -34 degrees.


Retrosequence was initiated by timer at T+4 minutes 46 seconds, which was 30 seconds prior to the spacecraft reaching its apogee. Gus Grissom assumed control of the spacecraft attitude at T+3 minutes 5 seconds and controlled the spacecraft by the manual proportional control system to T+5 minutes 43 seconds. He initiated firing of the retrorockets at T+5 minutes 10 seconds. From T+5 minutes 43 seconds, he controlled the spacecraft by the manual rate command system through reentry. The retrorocket package was jettisoned at T+6 minutes 7 seconds. The drogue parachute was deployed at T+9 minutes 41 seconds, and main parachute, at T+10 minutes 14 seconds. Landing occured


Flight successful but the spacecraft was lost during the postlanding recovery period as a result of premature actuation of the explosively actuated side egress hatch. The capsule sank in 15,000 feet of water shortly after splashdown. The astronaut egressed from the spacecraft immediatly after hatch actuation and was retrieved after being in the water for about 3 to 4 minutes.


(Reference NASA - Results of the Second US Manned Suborbital Space Flight)
(Reference NASA SP-4001 - Project Mercury: A Chronology)
(Reference NASA SP-4201 - This New Ocean)
(Reference Mercury Redstone 4 Mission Journal)

Click Here more information about MR-4


Project Mercury was the first human spaceflight program of the United States.

Project Mercury


The "Mercury seven" astronauts pose with an Atlas model July 12, 1962. L to R: Grissom, Shepard,Carpenter, Schirra, Slayton, Glenn,Cooper.


Project Mercury was the first human spaceflight program of the United States. It ran from 1959 through 1963 with the goal of putting a human in orbit around the Earth. The Mercury-Atlas 6 flight on February 20, 1962, was the first Mercury flight to achieve this goal.[1] Early planning and research was carried out by the National Advisory Committee for Aeronautics,[2] and the program was officially conducted by the newly created NASA. The name comes from Mercury, a Roman mythological god who is often seen as a symbol of speed. Mercury is also the name of the innermost planet of the solar system, which moves faster than any other and hence provides an image of speed, although Project Mercury had no other connection to that planet.
The Mercury program cost approximately $384 million,[3] the equivalent of about $2.8 billion in 2008 dollars.


Mission Rocket Call Sign Launch Date Launch Time Duration Remarks
Mercury-Jupiter Jupiter N/A N/A N/A N/A Cancelled in July, 1959 - Proposed suborbital launch vehicle for Mercury. Not flown.
Little Joe 1 Little Joe LJ-1 21 August 1959 N/A 00d 00h 00 m 20s Test of launch escape system during flight.
Big Joe 1 Atlas 10-D Big Joe 1 9 September 1959 N/A 00d 00h 13 m Test of heat shield and Atlas / spacecraft interface.
Little Joe 6 Little Joe LJ-6 4 October 1959 N/A 00d 00h 05 m 10s Test of spacecraft aerodynamics and integrity.
Little Joe 1A Little Joe LJ-1A 4 November 1959 N/A 00d 00h 08 m 11s Test of launch escape system during flight.
Little Joe 2 Little Joe LJ-2 4 December 1959 N/A 00d 00h 11 m 06s Carried Sam the monkey to 85 kilometres in altitude.
Little Joe 1B Little Joe LJ-1B 21 January 1960 N/A 00d 00h 08 m 35s Carried Miss Sam the monkey to 9.3 statute miles (15 kilometres) in altitude.
Beach Abort Launch escape system Beach Abort 9 May 1960 N/A 00d 00h 01 m 31s Test of the Off-The-Pad abort system.
Mercury-Atlas 1 Atlas MA-1 29 July 1960 13:13 UTC 00d 00h 03 m 18s First flight of Mercury spacecraft and Atlas Booster.
Little Joe 5 Little Joe LJ-5 8 November 1960 N/A 00d 00h 02 m 22s First flight of a production Mercury spacecraft.
Mercury-Redstone 1 Redstone MR-1 21 November 1960 N/A 00d 00h 00 m 02s Launched 4 inches (100 mm). Settled back on pad due to electrical malfunction.
Mercury-Redstone 1A Redstone MR-1A 19 December 1960 N/A 00d 00h 15 m 45s First flight of Mercury spacecraft and Redstone booster.
Mercury-Redstone 2 Redstone MR-2 31 January 1961 16:55 UTC 00d 00h 16 m 39s Carried Ham the Chimpanzee on suborbital flight.
Mercury-Atlas 2 Atlas MA-2 21 February 1961 14:10 UTC 00d 00h 17 m 56s Test of Mercury spacecraft and Atlas Booster.
Little Joe 5A Little Joe LJ-5A 18 March 1961 N/A 00d 00h 23 m 48s Test of the launch escape system during the most severe conditions of a launch.
Mercury-Redstone BD Redstone MR-BD 24 March 1961 17:30 UTC 00d 00h 8 m 23s Redstone Booster Development - test flight.
Mercury-Atlas 3 Atlas MA-3 25 April 1961 16:15 UTC 00d 00h 07 m 19s Test of Mercury spacecraft and Atlas Booster.
Little Joe 5B Little Joe AB-1 28 April 1961 N/A 00d 00h 05 m 25s Test of the launch escape system during the most severe conditions of a launch.
Mercury-Atlas 4 Atlas MA-4 13 September 1961 14:09 UTC 00d 01h 49 m 20s Test of Mercury spacecraft and Atlas Booster. Completed 1 orbit.
Mercury-Scout 1 Scout MS-1 1 November 1961 15:32 UTC 00d 00h 00 m 44s Test of Mercury tracking network.
Mercury-Atlas 5 Atlas MA-5 29 November 1961 15:08 UTC 00d 03h 20 m 59s Carried Enos the Chimpanzee on a two orbit flight.

From Wikipedia 4-10-2010

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