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Optimization study of computation and display requirements for human control of reusable orbital transport ascent
Spacecraft guidance and control systems during rendezvous and docking
Spacecraft guidance and control, propulsion, telecommunications, and systems analysis, and space science research
Space programs summary no. 37-17 - vol iv, space programs - telecommunications - guidance and control - propulsion
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The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur due to the interaction between the unmodeled nonlinear elements and linear ME guidance controller.
This paper offers a NASA perspective on guidance for fracture control and structural certification of "fracture critical" additive manufactured spacecraft structures. Results of a recent industry survey on the need for maturing NASA guidance for AM certification are presented for the first time. The survey results are placed in the context of a description of what NASA standards in this area already exist, where the gaps are, and what work to address the gaps is underway.
A spacecraft guidance, navigation, and control (GN&C) system is needed to enable a spacecraft to descend to a surface, take a sample using a touch-and-go (TAG) sampling approach, and then safely ascend. At the time of this reporting, a flyable GN&C system that can accomplish these goals is beyond state of the art. This article describes AutoGNC, which is a GN&C system capable of addressing these goals, which has recently been developed and demonstrated to a maturity TRL-5-plus. The AutoGNC solution matures and integrates two previously existing JPL capabilities into a single unified GN&C system. The two capabilities are AutoNAV and GREX. AutoNAV is JPL s current flight navigation system, and is fairly mature with respect to flybys and rendezvous with small bodies, but is lacking capability for close surface proximity operations, sampling, and contact. G-REX is a suite of low-TRL algorithms and capabilities that enables spacecraft operations in close surface proximity and for performing sampling/contact. The development and integration of AutoNAV and G-REX components into AutoGNC provides a single, unified GN&C capability for addressing the autonomy, close-proximity, and sampling/contact aspects of small-body sample return missions. AutoGNC is an integrated capability comprising elements that were developed separately. The main algorithms and component capabilities that have been matured and integrated are autonomy for near-surface operations, terrain-relative navigation (TRN), real-time image-based feedback guidance and control, and six degrees of freedom (6DOF) control of the TAG sampling event. Autonomy is achieved based on an AutoGNC Executive written in Virtual Machine Language (VML) incorporating high-level control, data management, and fault protection. In descending to the surface, the AutoGNC system uses camera images to determine its position and velocity relative to the terrain. This capability for TRN leverages native capabilities of the original AutoNAV system, but required advancements that integrate the separate capabilities for shape modeling, state estimation, image rendering, defining a database of onboard maps, and performing real-time landmark recognition against the stored maps. The ability to use images to guide the spacecraft requires the capability for image-based feedback control. In Auto- GNC, navigation estimates are fed into an onboard guidance and control system that keeps the spacecraft guided along a desired path, as it descends towards its targeted landing or sampling site. Once near the site, AutoGNC achieves a prescribed guidance condition for TAG sampling (position/orientation, velocity), and a prescribed force profile on the sampling end-effector. A dedicated 6DOF TAG control then implements the ascent burn while recovering from sampling disturbances and induced attitude rates. The control also minimizes structural interactions with flexible solar panels and disallows any part of the spacecraft from making contact with the ground (other than the intended end-effector).
Space programs supporting research and advanced development in systems analysis, spacecraft guidance and control, materials science, communications and telemetry, and propulsion.
Aerodynamics, spacecraft instrumentation, guidance and control, aerothermodynamics, base heating, and structural dynamics
Monograph on manned space flight, discussing environment, crew, spacecraft, navigation, guidance, control, communications, etc
Application Technology Satellite /ATS/ SPACECRAFT tradeoff and analysis - configuration paraboloid antenna, guidance and control power, spacecraft design, and apogee motor selection
Flow charts, symbol dictionaries, and computer program listings for guidance and control launch and abort simulation for spacecraft are presented.
Unmanned spacecraft guidance from earth based station - optimal control and orbit calculations
The development of autonomous spacecraft from 1960 to the present is traced within a framework of the definitions and measures of the level of autonomy. The attainment of milestones in the level of autonomy in spacecraft guidance and control is described in terms of the Mariner, Viking, Voyager, Galileo and Mark II (under development) spacecraft. The constant interplay between the definition of scientific mission goals and available technological capabilities is explored, along with current efforts to implement AI techniques and advanced software in spacecraft to allow reliable functioning in stressful conditions.
Electromagnetic sensors for guidance and control during spacecraft docking
Earth-based radio command of midcourse guidance for lunar flights is described, noting spacecraft, tracking station, and computing facility requirements
Optimal control and estimation theory application to space navigation, noting random disturbance