Engineering topics
Publications and source records attributed to Cameron, J. M..
In this paper, we report some models developed for analyzing parachute/balloon-assisted deployment of sensor packages within the Mars Aerobot Validation Program (MABVAP).
Lighter-than-air planetary missions continued attract growing interest in Mars exploration due to unique combination of proximity to the surface and mobility that far surpasses capability of surface vehicles. Following the experience with the Sojourner rover and subsequent development of powerful rovers for Mars 2003 and 2005 missions it became clear that on Mars surface rover mobility is quite restricted. Realistic travel distances may be limited to tens of kilometers per year on relatively obstacle-free plains and a few kilometers or less on the more rugged terrains. Many areas on Mars will be inaccessible to rovers. Several concepts for a Mars aerobot (robotic balloon) mission have been pursued in the last decade. Additional information is contained in the original extended abstract.
The distorted wave calculations are compared with the He-4(p,d) cross section. At all four energies the theoretical description of the data is relatively poor. While the general magnitude of the cross sections is not in bad agreement, the detailed slopes of the theoretical angular distributions miss the shapes of the experimental data in a rather fundamental way.
Previously cited in issue 19, p. 2997, Accession no. A82-38967
A systematic way to choose control design parameters and to evaluate performance for large space antennas is presented. The structural dynamics and control properties for a Hoop and Column Antenna and a Wrap-Rib Antenna are characterized. Some results of the effects of model parameter uncertainties to the stability, surface accuracy, and pointing errors are presented. Critical dynamics and control problems for these antenna configurations are identified and potential solutions are discussed. It was concluded that structural uncertainties and model error can cause serious performance deterioration and can even destabilize the controllers. For the hoop and column antenna, large hoop and long meat and the lack of stiffness between the two substructures result in low structural frequencies. Performance can be improved if this design can be strengthened. The two-site control system is more robust than either single-site control systems for the hoop and column antenna.
An integrated hardware/software system, SHADES, for shape determination and identification; a three dimensional multipoint sensor; multipoint sensor data; batch processing; and scanning algorithms are discussed.
Design considerations and projected solutions to on-board automated estimation techniques for advanced technology controls on a space station are described, with emphasis on the state estimator. The space station is modelled as a collection of rigid and flexible bodies connected at a finite number of hinges. The systems dynamics are characterized by angular velocities of the base body, gimbal angles, and deflections of the flexible appendages. The state estimator evolution is projected to occur in four generations, with the first being control logic in the Viking and Voyager spacecraft, the second in the Shuttle and Galileo probe, the third being large antennas and the prototype space station, the last, around the year 2000, for the actual space station. Considerations for attitude, ephemeris, shape determination, and position estimation through each generation are discussed.
It is pointed out that large space antennae and other large space structures will play an important role in the coming decades as commercial applications of space become feasible. A investigation is conducted of the structural dynamics and the control properties for a 64-meter diameter center fed antenna. Attention is given to antenna configuration and structural dynamic porperties, the attitude and structural control system, disturbance assessment, hardware sizing, the construction of weighting matrices, and numerical results. It is found that structural uncertainties and model error can cause serious performance deterioration and can even destabilize the controllers. Flight test and in-orbit system identification of critical structural modes will insure performance and reduce risk for large space antenna missions.
Cross-section and analyzing-power angular distributions for elastic scattering of 400-MeV protons by Pb-208 have been measured between 3 and 51 deg. Results have been compared to second-order Kerman-McManus-Thaler (1959) calculations of the optical potential. There is evidence that free nucleon-nucleon scattering amplitudes do not adequately describe nucleon propagation in nuclear matter at this energy.
Schlieren photography of flow distribution for transverse hydrogen jets from flat plate into Mach 2.72 airstream