Lunar Module Attitude Controller Assembly Digital Input Processing José Portillo jportillo34@hotmail.com

1. Lunar Module Attitude Controller AssemblyDigital Input ProcessingJosé Portillojportillo34@hotmail.com

2. Two types of Input: PROPORTIONAL Make use of the LM Guidance Computer Counter Interfaces and Transformer based Interface circuit. Used for Rate Command Augmentation Mode. DISCRETE Make use of the LM Guidance Computer discrete Interface Channel bits. Used for Pulse Mode. Used for Man-in-the-Guidance-Loop capabilities. Lunar Module Attitude Controller AssemblyDigital Input Processing

3. Proportional Input Processing

4. 1958: NACA technical paper describing “Systems that Command Velocity” as feedback control concept. Simulator investigation of Command Reaction Controls - Holleman, Euclid C.; Stillwell, Wendell H. - NACA RM H58D22 - April 14, 1958. 1959: Development of a Self-Adaptive flight control system for 1960: the X-15 research vehicle. 1963: Development of an Analog Rate Command Augmentation/Attitude-Hold 1964: control system for the Gemini Spacecraft. 1964: AIAA conference paper describing a Rate Command and Acceleration Comand systems implemented in the Langley Research Center Gemini- Agena Docking Simulators. Full-Scale Gemini-Agena Docking using Fixed and Moving base Simulators - Hatch, Howard G.; Riley, D. R.; Cobb, J. - AIAA paper 64-334 - June-July 1964. 1964: Apollo lunar program: decision to implement a “Digital Autopilot” for the Lunar Module Primary Guidance System. Manual Rate Command Augmentation SystemsA brief chronology

5. 1966: NASA LRC technical paper describing a Rate Command and Acceleration Command electronic control system for control of the Lunar Landing Research Vehicle. Flight Tests of a Manned Rocket-Powered Vehicle Utilizing the Langley Lunar Landing Research Facility - O’Bryan, Thomas C. - Presented at AIAA Guidance and Control Specialists Conference - Siattle, Washington - August 1966. 1966: NASA technical paper describing a Rate Command Augmentation system (fly-by-wire bang-bang) implemented in the DFRC lunar Landing Research simulation vehicle. Operational experience with the Electronic Flight control Systems of a lunar-Landing Research vehicle - Jarvis, Calvin R. - NASA TN D-3689 - July 5, 1966. 1966: Grumman Aircraft developed a Lunar Module Simulator for development and testing purposes. An Analog processing for the Hand Controller was implemented. Lunar Module Hover and Landing, Separation and Docking Simulation - Greene S.; Russo, J. - Presented at AIAA Flight Test, Simulation and Support Conference - Cocoa Beach, Florida - February 6-8, 1967. Manual Rate Command Augmentation SystemsA brief chronology

6. 1968: Development of a Rate Command Augmentation system embedded into the LGC Digital Autopilot. 1969: First flight test of the Lunar Module Digital Autopilot, including its manual Rate Command Augmentation/Attitude-Hold capability. Apollo 9 Mission in earth orbit. 1969: First Lunar Landing operation for the Lunar Module Digital Autopilot. Apollo 11 Mission. It includes an more complete Manual Rate Command Augmentation System. Manual Rate Command Augmentation SystemsA brief chronology

7. Embedded into the Digital Autopilot Software. Shows all the advantages of Digital Control System implementations over Analog Control System implementations: input data processing follows conditional paths, switching points (if ... then), and storage for past iterations to be used during present Command Control computations. External Control Parameters Proportional Commands Apollo Lunar Module Digital Manual Rate Command Augmentation System

8. Two Control Laws were employed for Manual Rate Command Augmentation: DIRECT RATE Used each time the “Commanded Rate change” exceeds a Breakout Level. Computes Jet-on time based only in Rate Error information: do it fast! To damp vehicle Rates below a “Target” Dead Band (before return control to the Attitude Hold Autopilot). Used on a per-Axis base. PSEUDO-AUTOMATIC Used while there is no Manual input. To Hold an Attitude. Computes Jet-on time based upon Rate and Attitude Error information. Uses a Phase-Plane logic to exercise Control. It can achieve very small Commanded Rates. Used on a per-Axis base to prevent Attitude drift about uncommanded Axes. Apollo Lunar Module Digital Manual Rate Command Augmentation System

9. Commanded Rate Exceeds Breakout Level? yes DIRECT RATE Control Law RHCCTR Counter no PSEUDO-AUTO Control Law Breakout Level Switch MCR Control Flow Flags Dead Band Switch • Digital Autopilot Control Parameters: • Constant Values in Rope Memory • Entered in-flight by crew • Flags set ON/OFF by previous iterations Apollo Lunar Module Digital Manual Rate Command Augmentation SystemControl Law Selection

10. Discrete Input Processing

11. A LM Guidance Computer Common 28 Volt. DC excitation source is applied to the Attitude Controller Assembly Plus and Minus Switches, and returning through the LM Guidance Computer input Channel. Provides a way to input low Rate Commands as well as Man-inthe-Guidance-Loop capabilities. Discrete Commands External Control Parameters Apollo Lunar Module Digital Manual Minimum Impulseand LPD Redesignator

12. Two Discrete Inputs: MINIMUM IMPULSE Enables the crew to perform economical low Rate maneuvers. Embedded into the Digital Autopilot Software. LM Guidance Computer Channel 31 includes the Input bits. LPD REDESIGNATOR Enables the crew to enter into the Lunar Landing Automatic Guidance Loop. Embedded into the Landing Approach Phase Guidance Software (the so called “Manual Steering Section”). LM Guidance Computer Channel 31 includes the Input bits. LPD Redesignation Input Commands are processed by an Interrupt. Apollo Lunar Module Digital Manual Minimum Impulseand LPD Redesignator

13. Lunar Module ACA Digital Input Processing “Start Gating” bit “A” Circuit 10 cps RHCCTR Counter HI (proportional) LO Out-Of-Detent Inbit (Channel 31) 10 cps Interrupt 10 (Redesignator Trap) “D” Circuit Discrete Inbit (Channel 31) Minimum Impulse & Discrete LPD DETENTCK EXTEND READ CHAN31 TS CH31TEMP MASK BIT15 EXTEND BZF RHCMOVED CAF OURRCBIT MASK DAPBOOLS EXTEND BZF PURGENCY RHCMOVED CS RCSFLAGS MASK BIT9 ADS RCSFLAGS CA OURRCBIT MASK DAPBOOLS EXTEND BZF JUSTOUT - 1 RATERROR CA CDUX TS CDUXD Digital Autopilot CA L No MASK -AZBIT CCS A -AZ CS AZEACH ADS AZINCR1 CA L MASK +AZBIT CCS A +AZ CA AZEACH ADS AZINCR1 CA L MASK -ELBIT CCS A -EL CS ELEACH ADS ELINCR1 CA L MASK +ELBIT CCS A +EL CA ELEACH ADS ELINCR1 TCF RESETRPT Fixed-Address Instruction 4050 DXCH ARUPT 4051 CA RUPT10BB 4052 XCH BBANK 4053 TCF PITFALL

14. Handling Qualities for Pilot Control of Apollo Lunar-LandingSpacecraft – Cheatham, D. C.,Hackler, C. T. - Journal ofSpacecraft and Rockets, Vol. 3, No. 5, May 1966, pp. 632-638. MIT's Role in Project Apollo - Volume III – Computer Subsystem – Hall, Eldon C. - August 1972. Manual Attitude Control of the Lunar Module – Stengel, Robert F. – AIAA paper 69-892 –August 1969. Apollo Experience Report - Crew Station Integration - Volume III– Spacecraft Hand ControllerDevelopment - Wittler, rank E. – Lyndon B. Johnson Space Center, Huston Texas 77058 - March 1975. A Manual Retargeted Automatic Landing System for the Lunar Module - Klumpp, Allan R. – Journal of Spacecraft and Rockets - Volume 5 - Number 2 -February 1968 - pp 129-138. Lunar Module Digital Autopilot - Widnall, William S. - Journal ofSpacecraft - Vol. 8, No. 1- January 1971. References

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