- Liberty Bell 7
- Pad LC-5 ()
- Redstone (6)
- Virgil I "Gus" Grissom
- John H. Glenn, Jr.
- 3/7/61 - Spacecraft delivered to Hanger S CCAFS
- Spacecraft # 11, Launch Vehicle S/N MR-8
- 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
- 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.
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- 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 - Results of the second U.S. manned Suborbital Space
Flight July 21, 1961)
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