A multimission three-axis stabilized spacecraft flight dynamics ground support system

The Multimission Three-Axis Stabilized Spacecraft (MTASS) Flight Dynamics Support System (FDSS) has been developed in an effort to minimize the costs of ground support systems. Unlike single-purpose ground support systems, which attempt to reduce costs by reusing software specifically developed for previous missions, the multimission support system is an intermediate step in the progression to a fully generalized mission support system in which numerous missions may be served by one general system. The benefits of multimission attitude ground support systems extend not only to the software design and coding process, but to the entire system environment, from specification through testing, simulation, operations, and maintenance. This paper reports the application of an MTASS FDSS to multiple scientific satellite missions. The satellites are the Upper Atmosphere Research Satellite (UARS), the Extreme Ultraviolet Explorer (EUVE), and the Solar Anomalous Magnetospheric Particle Explorer (SAMPEX). Both UARS and EUVE use the multimission modular spacecraft (MMS) concept. SAMPEX is part of the Small Explorer (SMEX) series and uses a much simpler set of attitude sensors. This paper centers on algorithm and design concepts for a multimission system and discusses flight experience from UARS

Comparative evaluation of solar, fission, fusion, and fossil energy resources, part 3

The role of nuclear fission reactors in becoming an important power source in the world is discussed. The supply of fissile nuclear fuel will be severely depleted by the year 2000. With breeder reactors the world supply of uranium could last thousands of years. However, breeder reactors have problems of a large radioactive inventory and an accident potential which could present an unacceptable hazard. Although breeder reactors afford a possible solution to the energy shortage, their ultimate role will depend on demonstrated safety and acceptable risks and environmental effects. Fusion power would also be a long range, essentially permanent, solution to the world's energy problem. Fusion appears to compare favorably with breeders in safety and environmental effects. Research comparing a controlled fusion reactor with the breeder reactor in solving our long range energy needs is discussed

OPERATING EXPERIENCE WITH HIGH POWER BEAM ABSORBERS IN THE SLAC BEAM SWITCHYARD*

In four years of operation at progressively increasing levels of average power new observations on the performance of slits, collimators, and beam dumps of various designs have been accumulated. The inherent longevity of high power beam absorbers based on low-Z or graded-Z design philosophy has been successfully demonstrated. Early operating experience at low power levels in the SLAC beam switchyard has been described previously. 1 The performance of multiple protective interlock circuitry is described and system response patterns are given. Two types of beam line failures are discussed: The air burst resulting from the melting of soft-metal vacuum seals and stainless steel transport pipes at modest power densities; and the water burst resulting from the failure of heat transfer surfaces at high power densities. Problems of beam line restoration in a radiation enviromnent are briefly discussed. Downtime to date attending beam-induced failure of the vacuum envelope has been of the order ‘of 350 hours, averages less than 10 hours per event, and accounts for some 150/O of the unscheduled downtime from all sources combined

Consistency among differential nuclear data and integral observations: the ALVIN code for data adjustment, for sensitivity calculations, and for identification of inconsistent data

Successful nuclear design requires adequate prediction of integral design parameters, and this in turn requires an adequate differential nuclear data base. Data bases that apparently permit reduced biases and design margins have been developed by a) least squares adjustment of differential data or b) trial-and-error selection from alternative evaluated data sets. Criticisms and defenses of such procedures are discussed. Useful data adjustment is related to consistency of the combined differential-integral data set and consistency tests related to least squares adjustment procedures are described. An approach to data adjustment is suggested that is contingent on consistency analysis. A FORTRAN code ALVIN has been developed to carry out the indicated data consistency and adjustment calculations, and to compute required sensitivities of integral parameters to nuclear data changes. The sensitivity modules of ALVIN are validated by computing with two distinct methods the cross-section sensitivity profile for neutron penetration through a thick iron shield. The data consistency and adjustment modules DAFT2 (for arbitrary variance-covariance data) and DAFT3 (for differential data base of arbitrary size uncorrelated with integral data) are validated by comparing their results for a set of data for three ZPR criticals. 2 figures, 5 tables, 51 references (auth