NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

Space Shuttle Technical Conference

Lyndon B. Johnson Space Center
Houston, Texas
June 28-30, 1983

NASA Conference Publication 2342

General Chairman: Aaron Cohen


This publication is a compilation of the papers prepared for the Space Shuttle Technical Conference held at the NASA Lyndon B. Johnson Space Center, Houston, Texas, June 28-30, 1983. The purpose of this conference was to provide an archival publication for the retrospective presentation and documentation of the key scientific and engineering achievements of the Space Shuttle Program following the attainment of full operational status by the National Space Transportation System.

To provide technical disciplinary focus, the conference was organized around 10 technical topic areas: (i) Integrated Avionics, (2) Guidance, Navigation, and Control, (3) Aerodynamics, (4) Structures, (5) Life Support, Environmental Control, and Crew Station, (6) Ground Operations, (7) Propulsion and Power, (8) Communications and Tracking, (9) Mechanisms and Mechanical Systems, and (10) Thermal and Contamination Environments and Protection Systems.

The papers in each technical topic which were presented over the 3-day conference period provide a historical overview of the key technical problems and challenges which were met and overcome during the development phase of the Space Shuttle Program. Taken as a whole, these papers provide a valuable archival reference to the magnitude and scope of this major national achievement.

Key Words: Space Shuttle; Orbiter; Avionics; Guidance; Navigation; Control; Aerodynamics; Structures; Life Support; Environmental Control; Ground Operations; Propulsion; Power; Communications; Tracking; Mechanisms; Mechanical Systems; Thermal Protection; Contamination.

Selected Avionics and Software Papers

Integration of Ground and On-board System for Terminal Count

Charles A. Abner, Kennedy Space Center
Don H. Townsend, Johnson Space Center

This paper discusses the challenge faced in the development of an integrated ground and on-board system for Space Shuttle terminal count management. The criteria considered in designing this system are outlined with some attention given to examples of problems encountered in the process of maturing the design.

Automation of Checkout for the Shuttle Operations ERA

Judith A. Anderson and Kenneth O. Hendrickson Kennedy Space Center

The Space Shuttle checkout is quite different from its Apollo predecessor. The complexity of the hardware, the shortened turnaround time, and the software that performs ground checkout have proven a challenging task to overcome. Generating new techniques and standards for software development and the management structure to control it have been implemented. New challenges await those that have been solved.

Ground/Man-Machine Interface for Orbiter Checkout

F. Herb Blackmon
IBM Test & Operations
Kennedy Space Center

This paper discusses the challenges presented by the concept of a reusable, cargo carrying space vehicle, and how those challenges were met for the Space Shuttle. Areas discussed here include the complexity of the vehicle, the ground support system, the onboard computer system, ramifications of a reusable vehicle, and the turn-around objectives for Shuttle flights. After six successful flights at the time of this writing, it can be safely said that the challenges presented here have been basically met.

Evolution of Shuttle Avionics Redundancy Management/Fault Tolerance

Jack C. Boykin and Joseph R. Thibodeau, NASA Johnson Space Center

Henry E. Schneider, McDonnell-Douglas Technical Services Company

The challenge of providing redundancy management (RM) and fault tolerance to meet the Shuttle Program requirements of fail operational/fail safe for the avionics systems was complicated by the critical program constraints of weight, cost, and schedule, This paper addresses the basic and sometimes false affectivity of less than pure RM designs. Evolution of the multiple input selection filter (the heart of the RM function) is discussed with emphasis on the subtle interactions of the flight control system that were found to be potentially catastrophic. Several other general RM development problems are discussed, with particular emphasis on the inertial measurement unit RM, indicative of the complexity of managing that three-string system and its critical interfaces with the guidance and control systems.

Man-Machine Interface and Control of the Shuttle Digital Flight System

Richard D. Burghduff and James L. Lewis, Jr. NASA Johnson Space Center


The challenge in designing the Orbiter displays and controls (D&C) system was to integrate the required aircraft and spacecraft D&C in the space available within the pilot's reach and vision. Some of the basic requirements for the D&C system were as follows: 1. A safe return with a single crewman from either forward crew station; 2. Normal operation (exclusive of payload management) of all mission phases using a fllghtcrew of two; 3. Accessibility to the flightcrew from the flight seats of D&C required for vehicle or subsystem management during ascent and entry; 4. D&C to provide for crew override of automated critical command functions; 5. Crew selection of automatic or manual flight guidance and control; 6. The means to annunciate and command safing of hazardous systems; 7. Interior and exterior illumination consistent in type and quality for crew operations.

Shuttle Avionics Software Development Trials, Tribulations, and Successes: The Backup Flight System

Edward S. Chevers, NASA Johnson Space Center

The Backup Flight System Requirement (excerpt)
The initial design of the Orbiter flight control system was limited to the quad-redundant computer complex. Systems management and nonavionic functions were contained in a fifth computer, which was not considered flight critical. This concept was well into development when a blue ribbon panel was asked to review all aspects of the Approach and Landing Test (ALT) phase of the Space Shuttle Program to verify that the design was proper. One of the conclusions reached by the panel was that an unnecessary risk was being taken by not providing a backup flight control system for the first flight. This decision was based on the relative complexity of the computer synchronization scheme being implemented and the lack of a direct manual flight control capability.

Shuttle Avionics Software Trials, Tribulations and Successes

O. L. Henderson, Honeywell, Inc.

   The decision to use a programmable digital control system on the Space Shuttle engine was a new application of digital control in the early 1970's. The use of digital control was primarily based upon the need for a flexible control system capable of supporting the total engine mission on a large complex pump fed engine. The mission definition included all control phases from ground checkout through post shutdown propellant dumping.
   The flexibility of the controller through reprogrammable software allowed the system to respond to the technical challenges and innovation required to develop both the engine and controller hardware. This same flexibility, however, placed a severe strain on the capability of the software development and verification organization. The overall development program required that the software facility accommodate significant growth in both the software requirements and the number of software packages delivered.
   The above requirements became a serious challenge to the software development facility. This challenge was met by reorganization and evolution in the process of developing and verifying software. The resulting process consistently provided high quality

Flight Software Fault Tolerance via the Backup Flight System

Terry D. Humphrey and Charles R. Price
NASA Johnson Space Center

A generic software error in the quadruply redundant primary flight system could result in the catastrophic loss of Space Shuttle vehicle control in the hostile environment of ascent or reentry. The Space Shuttle backup flight system was designed to protect the crew and vehicle In this eventuality. The significant challenges met in the design and development of this state-of-the-art protective system is the subject of this paper.

SSME Digital Control Design Characteristics

Walter T. Mitchell/Richard F. Searle
NASA Marshall Space Flight Center/Rocketdyne

   The Space Shuttle Main Engine (SSME) presented new requirements in the design of controls for large pump-fed liquid rocket engine systems. These requirements were the need for built-in full mission support capability, and complexity and flexibility of function not previously needed in this type of application.
   An engine mounted programmable digital control system was developed to meet these requirements. The engine system and controller and their function are described. Design challenges encountered during the course of development included accommodation for a very severe engine environment, the implementation of redundancy and redundancy management to provide fail-operational/fail-safe capability, removal of heat from the package, and significant constraints on computer memory size and processing time.
   The flexibility offered by programmable control reshaped the approach to engine design and development and set the pattern for future controls development in these types of applications.

Integrated Design Check of Shuttle Payload Avionics Interfaces

John F. Muratore

Kathy K. Whitcomb
Kennedy Space Center

Orbiter/payload avionics integration testing is a relatively new activity in the shuttle program. Payloads flown to date have shown extensive orbiter interfaces. This paper describes the three modes of testing at Kennedy Space Center and Cape Canaveral Air Force Station used to verify orbiter/payload avionics interfaces. These modes consist of orbiter testing using generic payload simulators, payload testing utilizing the actual payload and a high fidelity orbiter simulator, and interface testing with the actual orbiter and payload. Several special avionics techniques, such as the split flight computer technique have been developed to accomplish this testing. Experience from the first six shuttle cargoes is reviewed with emphasis on problems found in testing that would have hampered mission success.

Development and Implementation of the Verification Process for the Shuttle Avionics System

H. E. Smith, NASA Johnson Space Center
W.B. Fouts and J. Mesmer, Rockwell International

The paper examines the background of the Shuttle avionics system design and the unique drivers associated with the redundant digital multiplexed data processing system. With flight software pervading to the lowest elements of the flight-critical subsystems, it was necessary to identify a unique and orderly approach of verifying the system as flight-ready for STS-1. The approach and implementation plan is discussed, and both technical problems and management issues are dealt with. A summary of "lessons learned" completes the presentation.

Space Shuttle Main Engine Hardware Simulation

H. G. Vick/P. W. Hampton
NASA Marshall Space Flight Center/Rocketdyne

The Huntsville Simulation Laboratory (HSL) provides a simulation facility to test and verify the Space Shuttle Main Engine (SSME) avionics and software system using a maximum complement of flight type hardware. The HSL will permit evaluations and analyses of the SSME avionics hardware, software, control system, and mathematical models. It is a unique facility in its authenticity as well as in the complexity and scope of simulation. The laboratory has performed a wide spectrum of tests and verified operational procedures to ensure system component compatibility under all operating conditions. It is a test bed for integration of hardware/software/hydraulics. The HSL is and has been an invaluable tool in the design and development of the SSME.

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