-Page 1- (Title Page)
A Fixed-Based Simulator Study Of The Ability Of A Pilot To Establish Close Orbits Around The Moon
By M.J. Queijo and Donald R. Riley
Langley Research Center
June 1961
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-Page 3- (Summary)
Study made on a six-degree-of-freedom fixed base simulator of the ability of human pilots to modify ballistic trajectories of a space vehicle
approaching the moon to establish a circular orbit about 50 miles above the lunar surface. The unmodified ballistic trajectories had miss distances
from the lunar surface of from 40-80 miles, and a velocity range of from 8,200-8,700 feet per second at closest approach. The pilot was given control
of the thrust and torques about all three body axes. The information display given to the pilot was a hodograph of the vehicle rate of descent and
circumferential velocity, an altimeter, and vehicle attitude and rate meters.
General procedure was to acquaint the pilots with the instrumentation, controls, and indicated vehicle dynamics by flying a simple "nominal
trajectory." For this trajectory the exact operating mode was specified. The pilots then tried trajectories which were different from the
"nominal" and for which no operating procedure was specified.
The results of the investigation showed the pilots soon became adept at flying the simulator and could consistently establish orbits lying within an
altitute range from 10-90 miles. The indicated fuel consumption generally was about 1-3% of the initial vehicle mass more than that required by use
of a two-impulse Hohmann maneuver. The use of the hodograph as a primary display was very effective and useful.
(Intro)
Various time tables proposed for space exploration due to increasing national interest in space conquest. Among the many missions is exploration of
the moon, which according to most proposed programs, is expected in the foreseeable future.
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Lunar mission problems include guiding the vehicle to a soft landing, the establishment of a close circular orbit, and a close-approach circumlunar
flight. Fully automatic control systems require instrumentation to
a) measure vehicle velocity and position
b) compare (a) with nominal values
c) determine if corrective control required
d) apply corrective control if action desired
Since man is expected to participate in lunar missions, it is vital to determine if a human could satisfactorily perform some of the duties just
listed.
Now begins a list of symbols using some trigonometry and descriptions to document all the variables and methods used for lunar exercises.
-Page 5- (symbols list continued)
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Symbols list continued.
Then a short paragraph pointing you to appendix A for the basic equations of motion and auxiliary equations used in the investigation. A schematic
diagram of the equations of motion is shown in Figure 1.
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Includes a vehicle description.. guidance section at the nose, followed by crew compartment, fuel tank, and finally primary thruster. A study of
thrust revealed produced numbers in earth and lunar g units. Light thrust was used to simplify the pilot's task and in terms of fuel efficiency-
little is gained by higher thrust.
Also discussed are the cockpit and controls.
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Discussion of cockpit and controls continues. Then it gives a description of the instrument display.
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Discusses both Nominal and Off-Nominal Trajectories.
The nominal trajectory selected was one which would have a miss distance of 294,000 feet above lunar surface and v= 8,466 ft per sec at this point.
Off-nominal trajectories differed slightly from the nominal trajectory, in ways one might expect from small errors occuring during the process of
injecting the vehicle into orbit.
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Has a table showing the initial conditions and combination of miss distance and velocity for the various trajectories.
Now the document gets into the pilot's task and procedure when establishing a circuclar lunar orbit.
a) Obtain a zero bank-angle attitude
b) Aline the vehicle thrust axis in the plane of the trajectory
c) Pitch the vehicle to the desired attitude
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d) Apply thrust
e) Maintain proper vehicle attitude and trust on approach
f) Terminate thrust when the desired orbit attained
This is followed by a discussion on how one might accomplish the above tasks.
Preliminary computations of the nominal trajectory now begin to get discussed.
-Page 12- (Preliminary Computations of Nominal Trajectory continued)
Touches on fuel consumption and the inevitable errors within the parameters. A target area for the hodograph plane is determined using preliminary
flights as indicator of max and min ranges with respect to the distance to the moon's center and the altitude at which thrust is terminated.
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Discussion continues including the use of some equations in order to determine the combinations of radial distance and vehicle velocity which must be
attained to meet the parameters of the desired orbit.
Afterwards, the results of the nominal trajectory are discussed.
-Page 14- (results of nominal trajectory computations discussion continued)
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Off-Nominal Trajectories are now focused on. There were two regions of interest in working with the off-nominal trajectories.
1) Determination of the pattern of logic and technique which evolved for monitoring the vehicle pitch angle.
2) Measurement of pilot proficiency in establishing an acceptable orbit.
Equations are used in this discussion outlining exactly what a pilot should do he/she attempts to stay accurate to the trace path of the nominal
trajectory.
-Page 16- (Off-Nominal Trajectory discussion with respect to monitoring the vehicle pitch angle continued)
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Eventually it is found the only factor in the control of the vehicle which was confusing to various pilots who volunteered to fly the simulator was
associated with the effects of centrifugal acceleration on the motion of the vehicle.
Now they get to discussing Pilot proficiency.
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Comparisons for several off-nominal cases were made to a computed
Hohmann transfer. It
was found 1-3% more fuel was needed.
Now the document gets into supplementary investigations. Including:
a) The effects of thrust misalinement
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b) The use of another type of moment control system
c) The use of a modified display panel
The report now gives some concluding remarks..
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The results of the investigation showed that the pilots soon became adept at flying the simulator... (see above page 3 summary)
**Pages 21-29** Contains various appendixes
-Page 30- References
**Pages 31-56** Contains the various figures, diagrams, and pictures including the many Hodographs used.