Asymptotic theory for thrusting,spinning-up spacecraft maneuvers

We consider the problem of a spacecraft subjected to constant body-fixed forces and moments about all three axes during a spinning-up, thrusting maneuver. In applications, undesired forces and moments can arise due to thruster imbalances and misalignments and to center-of-mass offset. In previous works, approximate analytical solutions have been found for the attitude motion, and for the change in inertial velocity and inertial position. In this paper we find asymptotic and limiting-case expressions which we derive from the analytic solutions, in order to obtain simplified, practical formulas that lend insight into the motion. Specifically, we investigate how the motion evolves (1) as time grows without bound and (2) for geometric cases of the sphere, the thin rod, and the thin plate. Closed-forms or upper-bound limits are provided for angular velocities, Eulerian angles, angular momentum pointing error, transverse and axial velocities, and transverse and axial displacements. Summaries for the asymptotic limits (for zero initial conditions) are provided in tabular form. Results are verified by numerical simulations.     

Satellite dynamics under the influence of gravitational and aerodynamic torques. A study of stability of equilibrium positions

The dynamics of the rotational motion of a satellite, moving in the central Newtonian force field under the influence of gravitational and aerodynamic torques, is investigated. The paper proposes a method for determining all equilibrium positions (equilibrium orientations) of a satellite in the orbital coordinate system for specified values of aerodynamic torque and the major central moments of inertia; the sufficient conditions for their existence are obtained. For each equilibrium orientation the sufficient stability conditions are obtained using the generalized energy integral as the Lyapunov function. The detailed numerical analysis of the regions where the stability conditions of the equilibrium positions are satisfied is carried out depending on four dimensionless parameters of the problem. It is shown that, in the general case, the number of satellite’s equilibrium positions, for which the sufficient stability conditions are satisfied, varies from 4 to 2 with an increase in the value of the aerodynamic torque magnitude.     

Future investigations onboard Soviet biosatellites of the Cosmos series.

Many rat experiments onboard Cosmos biosatellites have furnished information concerning the effects of weightlessness, artificial gravity, and ionizing radiation combined with weightlessness on structural and biochemical parameters of the animal body. The necessity to expand the scope of physiological investigations has led to the project of flight primate studies. It is planned to carry out the first primate experiments onboard the Cosmos biosatellite in 1982. At present investigations of weightlessness effects on the cardiovascular and vestibular systems, higher nervous activity, skeletal muscles and biorhythms of two rhesus monkeys are being developed and tested. It is also planned to conduct a study of weightlessness effects on embryogenesis of rats and bioenergetics of living systems onboard the same biosatellite. Further experiments onboard Cosmos biosatellites are planned.     

Skylab experiment M-092: results of the first manned mission

Blood pressure at 30-sec intervals, heart rate, and percentage increase in leg volume continuously were recorded during a 25-min protocol in the M092 Inflight Lower Body Negative Pressure (LBNP) experiment carried out in the first manned Skylab mission. These data were collected during six tests on each crewman over a 5-month preflight period. The protocol consisted of a 5-min resting control period, 1 min at -8, 1 min at -16, 3 min at -30, 5 min at -40, and 5 min at -50 mm Hg LBNP. A 5-min recovery period followed. Inflight tests were performed at approximately 3-day intervals through the 28-day mission. Individual variations in cardiovascular responses to LBNP during the preflight period continued to be demonstrated in the inflight tests. Measurements of the calf indicated that a large volume of fluid was shifted out of the legs early in the flight and that a slower decrease in leg volume, presumably due to loss of muscle tissue, continued throughout the flight. Resting heart rates tended to be low early in the flight and to increase slightly as the flight progressed. Resting blood pressure varied but usually was characterized by slightly elevated systolic blood pressure, lower diastolic pressure, and higher pulse pressures than during preflight examinations. During LBNP inflight a much greater increase in leg volume occurred than in preflight tests. Large increases occurred even at the smallest levels of negative pressure, suggesting that the veins of the legs were relatively empty at the beginning of the LBNP. The greater volume of blood pooled in the legs was associated with greater increases of heart rate and diastolic pressure and larger falls of systolic and pulse pressure than seen in preflight tests. The LBNP protocol represented a greater stress inflight, and on three occasions it was necessary to stop the test early because of impending syncopal reactions. LBNP responses inflight appeared to predict the degree of postflight orthostatic intolerance. Postflight responses to LBNP during the first 48 hours were characterized by marked elevations of heart rate and instability of blood pressure. In addition, systolic and diastolic pressures were typically elevated considerably both at rest and also during stress. The time required for cardiovascular responses to return to preflight levels was much slower than in the case of Apollo crewmen.     

The future of space medicine.

In November 2000, the National Aeronautics and Space Administration (NASA) and its partners in the International Space Station (ISS) ushered in a new era of space flight: permanent human presence in low-Earth orbit. As the culmination of the last four decades of human space flight activities. the ISS focuses our attention on what we have learned to date. and what still must be learned before we can embark on future exploration endeavors. Space medicine has been a primary part of our past success in human space flight, and will continue to play a critical role in future ventures. To prepare for the day when crews may leave low-Earth orbit for long-duration exploratory missions, space medicine practitioners must develop a thorough understanding of the effects of microgravity on the human body, as well as ways to limit or prevent them. In order to gain a complete understanding and create the tools and technologies needed to enable successful exploration. space medicine will become even more of a highly collaborative discipline. Future missions will require the partnership of physicians, biomedical scientists, engineers, and mission planners. This paper will examine the future of space medicine as it relates to human space exploration: what is necessary to keep a crew alive in space, how we do it today, how we will accomplish this in the future, and how the National Aeronautics and Space Administration (NASA) plans to achieve future goals.     

Fluxes of Quasi-trapped Electrons with Energies >0.08 MeV in the Near-Earth Space on Drift Shells <Emphasis Type="Italic">L</Emphasis> < 2

We study the characteristics of fluxes of electrons with energy >80 keV in the near-Earth space regions corresponding to the drift shells L = 1.7, 1.4, and 1.1 observed during the entire period of the GRIF experiment onboard the Spectr module of the Mir orbital station from October 1995 to June 1997. The obtained geographic maps of the distribution of electron fluxes at the height of the station flight (400 km) and, also, the estimates of the spectra indicate that the South-Atlantic Anomaly provides for a mechanism of stable replenishment for shells with L < 1.5. The mechanism of stable replenishment of shells with L < 1.5 may be due to the scattering, in the residual atmosphere, of electrons from the inner radiation belt precipitating into the region of the South-Atlantic Anomaly.