Optimal guidance of low-thrust interplanetary space vehicles

The low-thrust guidance problem is defined as the minimum terminal variance (MTV) control of a space vehicle subjected to random perturbations of its trajectory. To accomplish this control task, only bounded thrust level and thrust angle deviations are allowed, and these must be calculated based solely on the information gained from noisy, partial observations of the state. In order to establish the validity of various approximations, the problem is first investigated under the idealized conditions of perfect state information and negligible dynamic errors. To check each approximate model, an algorithm is developed to facilitate the computation of the open loop trajectories for the nonlinear bang-bang system. Using the results of this phase in conjunction with the Ornstein-Uhlenbeck process as a model for the random inputs to the system, the MTV guidance problem is reformulated as a stochastic, bang-bang, optimal control problem. Since a complete analytic solution seems to be unattainable, asymptotic solutions are developed by numerical methods. However, it is shown analytically that a Kalman filter in cascade with an appropriate nonlinear MTV controller is an optimal configuration. The resulting system is simulated using the Monte Carlo technique and is compared to other guidance schemes of current interest.

The effects of the natural environment in cislunar space important to the simulation of space vehicles

ARS paper no. 2140-61: "Space flight report to the nation."

Orbital dynamics of space vehicles.

Bibliography: p. 392-401.

Surface roughness of ablated carbon-carbon nosetip composites /

"AFML-TR-78-157."

Optimum shape for transpiration-cooled nosetip of a re-entry vehicle /

"Technical report AFFDL-TR-78-147. Final report for period October 1974-June 1978."

A new framework for force feedback teleoperation of robotic vehicles based on optical flow

This paper proposes the use of optical flow from a moving robot to provide force feedback to an operator's joystick to facilitate collision free teleoperation. Optic flow is measured by wide angle cameras on board the vehicle and used to generate a virtual environmental force that is reflected to the user through the joystick, as well as feeding back into the control of the vehicle. The coupling between optical flow (velocity) and force is modelled as an impedance - in this case an optical impedance. We show that the proposed control is dissipative and prevents the vehicle colliding with the environment as well as providing the operator with a natural feel for the remote environment. The paper focuses on applications to aerial robotics vehicles, however, the ideas apply directly to other force actuated vehicles such as submersibles or space vehicles, and the authors believe the approach has potential for control of terrestrial vehicles and even teleoperation of manipulators. Experimental results are provided for a simulated aerial robot in a virtual environment controlled by a haptic joystick.

The practical application of space nuclear power in the 1960's for the International Astronautical Congress, Stockholm, Sweden, August 15-20, 1960 /

"Work done under AEC Contract: AT911-1)-GEN-8."

Space shuttle : the renewed promise /

"PAM-521"--P. [4] of cover.

Space shuttle : EVA opportunities.

Bibliography: p. 20.

The space shuttle at work /

Mode of access: Internet.

Proceedings of a conference held at Goddard Space Flight Center, Greenbelt, Maryland, June 15-16, 1970.

Includes bibliographical references.

Space measurements survey: Instruments and spacecraft, October 1957-March 1965.

Mode of access: Internet.

Preliminary criteria for the fracture control of space shuttle structures.

"Compiling, integrating, and editing of the document were performed by the Design Criteria Program Office of the McDonnell Douglas Astronautics Company under the direction of the Langley Research Center's Structural Systems Office (SSO)."

Pre-development study of a heat flux measurement device suitable for use on flight vehicles,

"Project no. AA-1577-Y. Subcontract no. 112705."

Structural design criteria applicable to a space shuttle.

Cover title.