when man leaves earth for the first man
mission to the moon
his mission is one of exploration he
will be pushed beyond the confines of
the atmosphere in his Apollo spacecraft
by the center and 5 rocket
the three astronauts will first enter a
parking orbit around the Earth after a
thorough check out of the spacecraft the
saturn 4b engine will be fired to begin
the trajectory that will take them to
the moon
the spacecraft will break into orbit
around the moon
the lunar lander
outcall the lunar module will be landed
on the surface by its two-man crew
leaving one man in the orbiting command
module the landing will represent the
first touchdown of man on a celestial
body other than Earth the astronauts
must set up an experiment package that
will continue to send data to Earth
after they have left
they must also collect geological
samples of the service which they will
bring back to earth the lunar crew will
lift off in the ass end stage of the
lunar module rendezvous and dock with
the orbiting command module and return
to Earth leaving the lunar module in
orbit around the moon a safe landing on
the moon has some unique facets due to
the lunar environment first the gravity
field of the moon is only one-sixth that
of Earth because of this the velocity
required to maintain a lunar orbit is
only about one mile per second as
compared with more than five miles per
second required to maintain a spacecraft
in orbit around the earth therefore the
lunar module will be traveling much more
slowly than Earth orbiting vehicle
second for practical purposes the moon
has no atmosphere there for the lunar
module needs no heat shield to protect
it from the friction induced atmospheric
heating such as is required for
spacecraft landing on earth
on the other hand there is no atmosphere
to assist in slowing the spacecraft or
in landing it on parachutes as on earth
the lunar module must rely on its
descent rocket engine for breaking and
landing the landing site has chosen a
portion of the Moon well surveyed by
previous unmanned and manned missions it
is located so that communications with
the lunar module will be maintained
during the power decent maneuvers for
landing lunar surface activities
and later a cent maneuvers the time for
landing will be early in the lunar
morning so that the Sun will be behind
the lunar module and give the best
contrast for visibility prior to the
descent the command module and lunar
module will be in a circular orbit of
about 60 nautical miles altitude with
two astronauts in the lunar module and
one in the command module the two
vehicles on dock and the command module
pilot visually inspect the lunar module
later a safe clearance will be
established between the two vehicles
prior to the first decent maneuver this
decent maneuver called descent orbit
insertion takes place 180 degrees from
the beginning of the powered breaking
and landing sequence for efficiency it
is performed by a retrograde burn of the
lunar module decent engine this place is
the lunar module in orbit with an apple
une or high point of 60 nautical miles
and a parallel or low point of 50,000
feet at the 50,000 foot altitude level
the power decent begins what happens
from this altitude two-touchdown is the
primary focus of this film the firing of
the decent engine at 50,000 feet marks
the beginning of powered breaking at
this time the velocity is about 5,500
feet per second or about 3,600 miles per
hour and the range to go to the landing
site is about 270 nautical miles this
phase is about eight minutes in duration
and is completed an altitude of
approximately 7,000 feet about five
nautical miles from the landing site
with a velocity of about 500 feet per
second or about 340 miles per hour
this marks the beginning of the final
approach up to this time the engine has
been firing essentially in a horizontal
direction and with the crew unable to
see in the forward direction
at the beginning of the final approach
the crew can for the first time see the
landing site see where they're going
the transition from powered breaking to
final approach is called Highgate turn
used by aircraft pilots to mark the
beginning of their final approach to the
airport runway this phase is designed to
give the flight crew maximum visibility
of the lunar surface in order to assess
the safety of the flight path and the
terrain in the general area of the
landing site it is about two minutes in
duration and terminates at an altitude
of about 500 feet about 2,000 feet from
the landing site with a velocity of
about 60 feet per second or 40 miles per
hour the transition from the final
approach to the landing phase is called
low gate again from the aircraft pilot
term designating the beginning of the
actual landing the landing phase is
designed primarily for ease of manual
control take over by the crew if
necessary for the final site selection
and touchdown on the lunar surface with
zero horizontal velocity and a touchdown
decent rate of about three feet per
second or two miles per hour
this is analogous to a helicopter
landing throughout all three phases of
the lunar decent and landing the safety
of the flight crew is paramount their
safety and the successful landing are
dependent upon the smooth interaction of
several lunar module systems the heart
of these systems is the primary guidance
navigation and control system called
pings this consists of two subsystems
the primary guidance computer and the
inertial measurement unit or IMU the
computer is the brains of the system and
for purposes of the lunar landing
contains two subsystems the guidance and
navigation section which contains the
basic logic and targeting supplied by
the mission planners to shape the
trajectory to satisfy operational
objectives and constraints within the
systems capability and the autopilot
corresponding to the automatic pilot
found on
commercial airliners at the beginning of
power D sent the computer contains the
most accurate possible estimate of the
lunar modules position and velocity this
information is sent from Mission Control
Center prior to dissent orbit insertion
the inertial measurement unit is the
primary sensor detecting changes in
velocity and attitude of the lunar
module through internal accelerometers
and gyros it sends this information to
the computer the computer then sends
control commands to the decent
proportion system referred to as dips
this is the rocket engine used for the
lunar descent and its controls
consisting of a throttle and again more
capable of plus or minus 6 degrees of
motion this engine has a maximum thrust
of about 10,000 pounds for efficiency
during braking and can be throttled from
6,000 to 1,000 pounds for controlled
operations in the final approach and
landing faces the computers guidance and
navigation section controls the throttle
while the autopilot controls the gimbal
for slow rate attitude changes have
higher rate attitude changes are needed
another system comes into use the
reaction control system
this consists of four groups of four
small control Rockets mounted on the
lunar module to control pitch roll and
yaw the reaction control system is also
controlled by the computers autopilot as
the lunar module gets closer to the
surface of the moon yet another system
comes into play the landing radar which
provides updated direct readings of
altitude and velocity as the lunar
module approaches the surface of the
Moon the landing radar is mounted at the
bottom rear of the descent stage it can
be directed to two positions one for
breaking when the lunar module is nearly
horizontal the other for final approach
and landing when it is nearly vertical
landing radar consists of four beams one
for determining altitude three for
determining relative velocity throughout
the descent ultimate control over the
systems can be exercised by the crew
through the computer display and
keyboard called the diske reviewing the
system's quickly then the primary
guidance navigation and control system
consists of an inertial measurement unit
of velocity and attitude sensing device
sending information directly to the
computer the computer sends control
commands to the descent propulsion
system and the reaction control system
as the lunar module approaches the moon
surface the landing radar sends direct
altitude and velocity updates to the
computer the crew monitors the descent
and maintains ultimate systems control
through the computer display and
keyboard with this general view of the
systems we are now able to take a close
look at the powered descent and landing
sequence as the lunar module approaches
the 50,000 foot level for the initiation
of powered breaking it is in a facedown
attitude to afford the crew of view of
the lunar surface for gross navigational
checks should there be a decision not to
fire the decent engine the lunar module
will remain in a safe orbit around the
moon of 50,000 feet by 60 nautical miles
and we'll rendezvous with the command
module at 50,000 feet with the landing
site still be on the horizon the crew
ignites the descent engine it builds to
full thrust marking the start of the
powered breaking phase at this time the
crew has the option to be face up or
face down but must be face up by the 42
30,000 foot level this phase of the
trajectory is controlled automatically
by the computer with inputs from the
inertial measurement unit when the lunar
module reaches the 40,000 to 30,000 foot
altitude range it is rolled onto its
back either by the pilot or
automatically now the landing radar
acquires the surface and begins updating
the computer estimate of altitude the
crew can no longer see the moon and is
totally dependent on the landing radar
and computer displays for knowledge of
where they are
at around 20,000 feet the computer
begins throttling down the decent engine
to about half thrust to achieve high
Gate at about this time the crew will
see the lunar surface for the first time
since the roll maneuver as the lunar
module has been descending it has
certainly been pitching up at Highgate
approximately 7,000 feet altitude it
will be within 50 degrees of vertical
now for the first time the crew is able
to see the landing site about five miles
away
there is now the option to stay with the
automatic system or to take over manual
control nominally he will stay with the
automatic system to locate the crew uses
the landing point designator a grid on
the commander's window to locate the
site the computer display tells them
where the site should be relative to the
grid and updates the position every two
seconds during this approach phase about
two minutes in duration the crew can
manually change the point to which the
automatic system is steering this is
called re-designation and is used to
avoid hazardous terrain features in the
landing area at about 2,000 feet from
the landing site and at an altitude of
about 500 feet the lunar module achieves
locate the beginning of the landing
phase if the spacecraft commander likes
where the automatic system is taking him
he likes to stay with it if not say a
boulder or crater obstructs the landing
site he can manually alter the lunar
module course to a new site the speeds
are now low enough and the trajectory so
designed that the crew will normally
take over manual control the velocity
should be in the neighborhood of 60 feet
per second horizontally and 16 feet per
second vertically the commander is
making his final decisions as to the
exact location of the landing site if he
stays with the automatic trajectory an
altitude of about 150 feet the
spacecraft has zero horizontal velocity
and is descending at about three feet
per second
probes from the landing gear touch the
lunar surface turning on a light in the
cabin the spacecraft commander cuts off
the decent engine and the lunar module
touches down on the moon reviewing then
preparation for lunar decent begins in
circular orbit 60 nautical miles above
the moon with the undocking and
separation of the command lunar modules
decent orbit insertion occurs 180
degrees from the beginning of powered
breaking with the retrograde firing of
the lunar module descent engine the
lunar module costs down to the 50,000
foot level about 270 miles from the
landing site with a velocity of 5,500
feet per second or 3,600 miles per hour
at this time the decent engine is fired
for the powered breaking phase of the
landing trajectory the lunar module is
in a facedown attitude until it reaches
the 42 30,000 foot altitude range then
rolls onto its back to give the landing
radar surface acquisition the transition
to the next phase the final approach is
called Highgate and occurs at an
altitude of approximately 7,000 feet
about five nautical miles from the
landing site with a velocity of about
500 feet per second or 340 miles per
hour at Highgate the lunar module which
has been slowly pitching up during the
breaking phase is within about 50
degrees of vertical so that the landing
site is visible through the forward
window now the crew locates the landing
site through the landing point
designator grid on the window from
information provided by the computer
display and assesses the conditions at
the landing site about two minutes later
at an altitude of about 500 feet 2,000
feet from the landing site with a
velocity of about 60 feet per second the
lunar module will pass through locate
the transition from the final approach
to the landing phase
at 150 feet altitude the horizontal
velocity will be 0 and the descent rate
about 3 feet per second when the landing
probes touch the surface the commander
shuts off the scent engine and the lunar
module touches down while the success of
the landing is of obvious importance the
overriding concern is for crew safety at
all times while all other phases of the
lunar mission can be demonstrated in
earth or lunar orbit the man lunar
landing can be demonstrated only by its
accomplishment
should there be a malfunction of any of
the systems the landing could
immediately be aborted should there be a
failure in the primary guidance
navigation and control system a backup
aboard guidance system would take over
and enable lunar module to abort the
landing and ascend to orbit for
rendezvous with the command module sure
the decent engine fail the spacecraft
commander would hit the abort stage
button this automatically separates the
asset and decent stages fires the Ascend
engine and switches to ascend guidance
taking them back into orbit and the
subsequent rendezvous with the command
module under control of either the
primary or abort guidance system the
importance of the descent and landing
phase of the lunar mission is obvious
for it is only upon its successful
completion that we will begin manned
exploration of the moon
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