FOIA: The Ability of a Pilot to Establish Orbit Around the Moon.

MOON_BASE_11.pdf
A Fixed-Base-Simulator Study of the Ability of a Pilot to Establish Close Orbits Around the Moon.
A research study of the ability of human pilots to modify the ballistic trajectory on a spacecraft, and establish a low eccentricity orbit around the moon.
Document date: 1961-06-01
Department: NASA Langley Research Center
Author: M.J. Queijo and D.R. Riley
Document type: Technical Note
pages: 56


Archivist's Notes: This is a technical document on the ability of a human pilot to modify the insertion trajectory of a spacecraft and achieve an orbit above the lunar surface without computer assistance. The conclusion of which is that a human is able to achieve a stable, low eccentric orbit within acceptable limits and fuel expenditure, with minimal training. Though heavily laden with trigonometry and aviation lingo, it is an overall interesting document. The main body of the document as well as the extensive appendixes, block diagrams, mathematical equations, geometrical diagrams, is in excellent condition; however, the attached photographs are in poor condition.

-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

-Page 2- (Blank)

-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.

-Page 4- (Intro continued)

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)

-Page 6-

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.

-Page 7-

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.

-Page 8-

Discussion of cockpit and controls continues. Then it gives a description of the instrument display.

-Page 9-

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.

-Page 10-

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

-Page 11- (continued)

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.

-Page 13- (continued)

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)

-Page 15-

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)

-Page 17- (continued)

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.

-Page 18- (Pilot Proficiency continued)

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

-Page 19- (continued)

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..

-Page 20- (concluding remarks continued)

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.

It's really no surprise that this information was classified. Although inserting a space vehicle into orbit around the moon involves well known mathematical principles, in the 1960s it just hadn't been done before. Thus naturally there was a lot of apprehension surrounding such a task. While simulators are great indicators of what will transpire, the fact remains that errors could be catastrophic.. like crashing the vehicle into the moon or missing the insertion point and flying into deep space.

Illustration of Lunar Orbit Insertion