The Ergometer Vibration Isolation System (EVIS) was developed to isolate the vibration caused by cycle ergometer exercise. The EVIS employed isolators at four corners of a special one-piece cycle ergometer mounting frame to inhibit transfer of forces to the spacecraft structure, and four active "throw-mass"-type stabilizers which counteract the forces induced by exercise and stabilize the ergometer. The stabilizers had linear motors to drive the throw masses. Accelerometers and sophisticated control feedback circuitry were used to detect the forces and control the motion of the stabilizers. This study had the following specific aims:
Acceleration data was collected on the STS-50 mission using the High Resolution Acceleration Package (HIRAP) and the Space Acceleration Measurement System (SAMS). HIRAP data was downlinked during the mission allowing a quick look at the acceleration levels produced by cycle exercise in the three different mounting configurations. The SAMS data was recovered from the Orbiter after landing and required a significant amount of postflight analysis to produce the final report.
Identify the magnitude and frequency of the vibration generated by the cycle ergometer with the isolation system on specific areas of the Spacelab module and middeck area of the Orbiter.
Based on the SAMS data, there was no discernible difference in the acceleration data between the EVIS and bungee system. The hard-mounted cycle clearly produced higher acceleration levels than those obtained using the EVIS or the bungees, particularly at Orbiter resonant frequencies.
Evaluate the ease of set up and stowage of the EVIS.
The setup and stowage of the EVIS was somewhat involved because of the number of parts, complexity of the cabling system, mounting requirements for the isolators, and the requirement to install stabilizer modules and isolators as matched pairs. The use of color coding on the cycle frame, stabilizer modules, isolators, and cables was invaluable in ensuring the correct setup of the system; extensive ground-based training and in-flight procedures reduced setup time and made the crew aware of any anomalies in system setup or operation.
Evaluate the impact of the EVIS on the performance of exercise activities.
During cycle exercise, it is natural for a person to use upper body motion to aid the legs in performing the required exercise. In-flight videos showed that crewmembers routinely reached for objects (cycle display panel, drink bags, towels) during the exercise session. This type of motion is not tolerated by the EVIS as demonstrated by the stabilizer throw masses.
Evaluate the impact of the EVIS on crew activities in the middeck area.
Given the volume requirements of the EVIS, the limitations in stowing the system between exercise sessions, and the difficulty of performing middeck operations during cycle exercise, the EVIS is not recommended for Shuttle flights, particularly on a flight where a SLM is not present. A system of this size would be more practical in the SLM where there is more room and where a variety of crew activities are not occurring simultaneously.
Results from Acceleration Data
EVIS: While exercising on the cycle/EVIS system, an acceleration level of approximately 25 µg's was measured with HIRAP. The primary component of this acceleration was in the x (Orbiter fore-aft) direction and was due to the yawing motion of the rider and cycle system produced by the rider's leg and upper body movement. Some system motion in the z direction was observed and the EVIS Powerdown Test (EPDT) was initiated to determine how much of the z motion was being attenuated by the reaction forces generated by the throw masses in the EVIS stabilizers.
Bungees: The bungee system was set up and several exercise sessions performed prior to taking HIRAP data. The HIRAP data showed acceleration levels of approximately 40 µg's for cycle exercise using the bungees; the primary loads occurred in the x direction due to the yawing motion of the rider and cycle system. During downlink of a bungee session, investigators on the ground observed that the bungee pre-loads were not high enough for adequate system stability and that the addition of two extra bungees would help the stability and possibly reduce the level of vibration. After the above recommendations were implemented, the crew reported that the system stability had increased.
Hard Mount: The cycle was hard mounted to the aft flight deck for four exercise sessions during a mission g-tolerant window. HIRAP data from these sessions showed acceleration levels of approximately 50 µg's. The crew reported this to be the most stable and comfortable cycle configuration.
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