Low-gravity environment of the Mir Space Station

Abstract

The NASA Lewis Research Center's Space Acceleration Measurement System is being used to record the low-gravity environment of the Mir Space Station. Approximately 220 hours of non-continuous data were collected between October 1994 and November 1995 in the Kristall and Kvant-1 modules. Acceleration data were collected on Mir during the STS-74 docking. Two data analysis techniques are introduced and the results of extensive data analyses are summarized. Transient and oscillatory accelerations recorded on Mir are generally produced by vehicle subsystem operations, experiment operations, and crew activity. In looking at oscillatory disturbances in the acceleration spectrum from about 0.01 Hz to 250 Hz, we see that crew exercise (1 to 4 Hz with broadband excitation from 10 to 40 Hz) and structural modes (0.3 to 2 Hz) contribute the most energy below 5 Hz. From 10 Hz to 100 Hz, vehicle subsystems (water pump at 24 Hz and harmonics, air circulation system at 51 Hz) and several significant unknowns, particularly in the 40 to 90 Hz range, are the principal sources of disturbance. Above 100 Hz, strong contributors lie at 102 Hz (air circulation system harmonic), 120 Hz (water pump harmonic), and 140 Hz (unknown). Gyrodyne operation can be seen at about 166.7 Hz (10,000 rpm). The microgravity environment of Mir is similar to the NASA Space Shuttle Orbiters except that the Mir structural modes are at lower frequencies and there appear to be more subsystem vibration sources on the larger, more complex Mir structure.