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.
Launch:
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.
Orbit:
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
Landing:
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.
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.
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