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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1977

Navigating the Viking landers

On July 20, 1976, Viking Lander 1 became the first unmanned spacecraft to land and operate successfully on the planet Mars. This was followed by a second successful landing on September 3, 1976. This paper gives a detailed description of the autonomous on-board navigation process to perform the guidance, control, and entry navigation functions. Also, the functions performed on the ground to generate and validate the guidance commands sent to the spacecraft prior to descent are described. In-flight measures of navigation system performance are compared against a-priori error estimates to show that the descents were completely nominal in all respects. The final landing errors were 25 km and 10 km for Missions 1 and 2, respectively.

Euler, E. A.↗
NASA NTRS2002

A Closed-Loop Hardware Simulation of Decentralized Satellite Formation Control

In recent years, there has been significant interest in the use of formation flying spacecraft for a variety of earth and space science missions. Formation flying may provide smaller and cheaper satellites that, working together, have more capability than larger and more expensive satellites. Several decentralized architectures have been proposed for autonomous establishment and maintenance of satellite formations. In such architectures, each satellite cooperatively maintains the shape of the formation without a central supervisor, and processing only local measurement information. The Global Positioning System (GPS) sensors are ideally suited to provide such local position and velocity measurements to the individual satellites. An investigation of the feasibility of a decentralized approach to satellite formation flying was originally presented by Carpenter. He extended a decentralized linear-quadratic-Gaussian (LQG) framework proposed by Speyer in a fashion similar to an extended Kalman filter (EKE) which processed GPS position fix solutions. The new decentralized LQG architecture was demonstrated in a numerical simulation for a realistic scenario that is similar to missions that have been proposed by NASA and the U.S. Air Force. Another decentralized architecture was proposed by Park et al. using carrier differential-phase GPS (CDGPS). Recently, Busse et al demonstrated the decentralized CDGPS architecture in a hardware-in-the-loop simulation on the Formation Flying TestBed (FFTB) at Goddard Space Flight Center (GSFC), which features two Spirent Cox 16 channel GPS signal generator. Although representing a step forward by utilizing GPS signal simulators for a spacecraft formation flying simulation, only an open-loop performance, in which no maneuvers were executed based on the real-time state estimates, was considered. In this research, hardware experimentation has been extended to include closed-loop integrated guidance and navigation of multiple spacecraft formations using GPS receivers and real-time vehicle telemetry. A hardware closed-loop simulation has been performed using the decentralized LQG architecture proposed by Carpenter in the GPS test facility at the Center for Space Research (CSR). This is the first presentation using this type of hardware for demonstration of closed-loop spacecraft formation flying.

Ebimuma, Takuji↗
NASA NTRS2012

Ground Simulation of an Autonomous Satellite Rendezvous and Tracking System Using Dual Robotic Systems

A hardware-in-the-loop ground system was developed for simulating a robotic servicer spacecraft tracking a target satellite at short range. A relative navigation sensor package "Argon" is mounted on the end-effector of a Fanuc 430 manipulator, which functions as the base platform of the robotic spacecraft servicer. Machine vision algorithms estimate the pose of the target spacecraft, mounted on a Rotopod R-2000 platform, relay the solution to a simulation of the servicer spacecraft running in "Freespace", which performs guidance, navigation and control functions, integrates dynamics, and issues motion commands to a Fanuc platform controller so that it tracks the simulated servicer spacecraft. Results will be reviewed for several satellite motion scenarios at different ranges. Key words: robotics, satellite, servicing, guidance, navigation, tracking, control, docking.

Trube, Matthew J.↗
NASA NTRS2010

Configuring the Orion Guidance, Navigation, and Control Flight Software for Automated Sequencing

The Orion Crew Exploration Vehicle is being designed with greater automation capabilities than any other crewed spacecraft in NASA s history. The Guidance, Navigation, and Control (GN&C) flight software architecture is designed to provide a flexible and evolvable framework that accommodates increasing levels of automation over time. Within the GN&C flight software, a data-driven approach is used to configure software. This approach allows data reconfiguration and updates to automated sequences without requiring recompilation of the software. Because of the great dependency of the automation and the flight software on the configuration data, the data management is a vital component of the processes for software certification, mission design, and flight operations. To enable the automated sequencing and data configuration of the GN&C subsystem on Orion, a desktop database configuration tool has been developed. The database tool allows the specification of the GN&C activity sequences, the automated transitions in the software, and the corresponding parameter reconfigurations. These aspects of the GN&C automation on Orion are all coordinated via data management, and the database tool provides the ability to test the automation capabilities during the development of the GN&C software. In addition to providing the infrastructure to manage the GN&C automation, the database tool has been designed with capabilities to import and export artifacts for simulation analysis and documentation purposes. Furthermore, the database configuration tool, currently used to manage simulation data, is envisioned to evolve into a mission planning tool for generating and testing GN&C software sequences and configurations. A key enabler of the GN&C automation design, the database tool allows both the creation and maintenance of the data artifacts, as well as serving the critical role of helping to manage, visualize, and understand the data-driven parameters both during software development and throughout the life of the Orion project.

Odegard, Ryan G.↗
NASA NTRS1972

Anomalous type III bursts explained in terms of intermittent solar wind streams observed by Pioneer spacecraft.

Occasional solar radio bursts drift downward in frequency (like type III bursts), but the drift slows or ceases or it may even reverse. These anomalous forms are called L-bursts, U-bursts, etc., and are observed as low as 1 MHz by spacecraft. The conventional explanation involves guidance of relativistic exciting particles by solar magnetic fields that do not have the spiral shape expected in undisturbed conditions. A reasonable alternative explanation is possible and, indeed, it follows directly from the inferences which have been drawn from the Stanford dual-frequency experiment flown on four Pioneer spacecraft. Analysis of temporal variations in these data leads to the conclusion that narrow streams of enhanced concentration have lifetimes which are typically about one day and the streams seem to be intermittently ejected by long-enduring sources at the sun. Each enhancement is thought to lie along a spiral and to have a beginning and an end. It may happen that relativistic exciters encounter the tail of such a discrete streamer; the concentration encountered by such exciters would initially decline but, at the streamer tail, it would level off and perhaps increase. The plasma frequency versus time (the burst frequency) would then cease to drop in the typical type III profile and would level off or increase (as in a U-burst).

Croft, T. A.↗
NASA NTRS1975

Development of a unified guidance system for geocentric transfer

A method is presented for open loop guidance of a solar electric propulsion spacecraft to geosynchronsus orbit. The method consists of determining the thrust vector profiles on the ground with an optimization computer program, and performing updates based on the difference between the actual trajectory and that predicted with a precision simulation computer program. The motivation for performing the guidance analysis during the mission planning phase is discussed, and a spacecraft design option that employs attitude orientation constraints is presented. The improvements required in both the optimization program and simulation program are set forth, together with the efforts to integrate the programs into the ground support software for the guidance system.

Cake, J. E.↗
NASA NTRS1975

Development of a unified guidance system for geocentric transfer

A method is presented for open loop guidance of a solar electric propulsion spacecraft to geosynchronous orbit. The method consists of determining the thrust vector profiles on the ground with an optimization computer program, and performing updates based on the difference between the actual trajectory and that predicted with a precision simulation computer program. The motivation for performing the guidance analysis during the mission planning phase is discussed, and a spacecraft design option that employs attitude orientation constraints is presented. The improvements required in both the optimization program and simulation program are set forth, together with the efforts to integrate the programs into the ground support software for the guidance system.

Cake, J. E.↗
NASA NTRS2008

Guidance, Navigation and Control (GN&C): Best Practices for Human-Rated Spacecraft Systems

In 2007 the NESC completed an in-depth assessment to identify, define and document engineering considerations for the Design Development Test and Evaluation (DDT&E) of human-rated spacecraft systems. This study had been requested by the Astronaut Office at JSC to help them to better understand what is required to ensure safe, robust, and reliable human-rated spacecraft systems. The 22 GN&C engineering Best Practices described in this paper are a condensed version of what appears in the NESC Technical Report. These Best Practices cover a broad range from fundamental system architectural considerations to more specific aspects (e.g., stability margin recommendations) of GN&C system design and development. 15 of the Best Practices address the early phases of a GN&C System development project and the remaining 7 deal with the later phases. Some of these Best Practices will cross-over between both phases. We recognize that this set of GN&C Best Practices will not be universally applicable to all projects and mission applications.

Lebsock, Ken↗
NASA NTRS1962

Some Abort Techniques and Procedures for Manned Spacecraft

This paper is concerned with our present state of knowledge on the procedures and effectiveness of aborts from manned orbital and lunar missions. By abort is meant a deliberate or unintentional termination of the primary mission followed by an expedient return to earth of the payload (spacecraft and crew). A deliberate abort may be initiated if a critical component failed and thus impaired the probability of mission success or the crew's safety. Examples of this kind of abort are failure of the launch guidance system or the oxygen and cabin pressure system. Also, an unintentional abort may occur during the launch phase due to the complete or partial failure of one of the launch-vehicle stages to operate. For each mission every conceivable set of circumstances must be considered and evaluated to see if an abort of the mission is called for and to determine what sequence of events should occur to bring the spacecraft and crew safely back to earth with the highest probability of success. Factors which must be considered are: how to specify and sense an abort condition, how much fuel should be put onboard the vehicle for abort purposes, what size and kind of rocket engines are best suited for each mission, and what compromise is incurred due to other mission requirements? If an abort occurs, the optimum time of application as well as the magnitude and direction of the velocity changes must be determined beforehand and the crew must be clearly informed of what action is required or what the situation is so that they can decide the proper action.

Maneuver↗
NASA NTRS2009

General Purpose Data-Driven Monitoring for Space Operations

As modern space propulsion and exploration systems improve in capability and efficiency, their designs are becoming increasingly sophisticated and complex. Determining the health state of these systems, using traditional parameter limit checking, model-based, or rule-based methods, is becoming more difficult as the number of sensors and component interactions grow. Data-driven monitoring techniques have been developed to address these issues by analyzing system operations data to automatically characterize normal system behavior. System health can be monitored by comparing real-time operating data with these nominal characterizations, providing detection of anomalous data signatures indicative of system faults or failures. The Inductive Monitoring System (IMS) is a data-driven system health monitoring software tool that has been successfully applied to several aerospace applications. IMS uses a data mining technique called clustering to analyze archived system data and characterize normal interactions between parameters. The scope of IMS based data-driven monitoring applications continues to expand with current development activities. Successful IMS deployment in the International Space Station (ISS) flight control room to monitor ISS attitude control systems has led to applications in other ISS flight control disciplines, such as thermal control. It has also generated interest in data-driven monitoring capability for Constellation, NASA's program to replace the Space Shuttle with new launch vehicles and spacecraft capable of returning astronauts to the moon, and then on to Mars. Several projects are currently underway to evaluate and mature the IMS technology and complementary tools for use in the Constellation program. These include an experiment on board the Air Force TacSat-3 satellite, and ground systems monitoring for NASA's Ares I-X and Ares I launch vehicles. The TacSat-3 Vehicle System Management (TVSM) project is a software experiment to integrate fault and anomaly detection algorithms and diagnosis tools with executive and adaptive planning functions contained in the flight software on-board the Air Force Research Laboratory TacSat-3 satellite. The TVSM software package will be uploaded after launch to monitor spacecraft subsystems such as power and guidance, navigation, and control (GN&C). It will analyze data in real-time to demonstrate detection of faults and unusual conditions, diagnose problems, and react to threats to spacecraft health and mission goals. The experiment will demonstrate the feasibility and effectiveness of integrated system health management (ISHM) technologies with both ground and on-board experiments.

Iverson, David L.↗
NASA NTRS2003

Laser-Based Relative Navigation and Guidance for Space Shuttle Proximity Operations

American manned spacecraft have used visual piloting techniques in the terminal phase of randezvous during the Gemini, Apollo, Skylab, and Space Shuttle programs. In the last several years, space- shuttle astronauts have used the Rendezvous and Proximity Operations Program (RPOP), running; on a laptop computer, as a guidance and navigation aid during proximity operations. By processing measurements to the target satellite taken by a laser sensor, RPOP provides the shuttle crew with a more accurate relative position and velocity than from any other source. The inclusion of guidance algorithms allows RPOP to determine delta-velocities to fly very efficient, repeatable trajectories. This paper will focus on the guidance and navigation algorithms in RPOP, as well as results from simulation and flight. Although developed for shuttle proximity operations, the RPOP algorithms have potential applicability to an automated vehicle.

Laser sensors↗