Space Acceleration Measurement System Research Articles

Analysis of Vibratory Data Collected by the Space Acceleration Measurement System (SAMS) on Blue Origin, June 19, 2016

Abstract On Sunday, June 19, 2016, a Space Acceleration Measurement System triaxial sensor head flew on a suborbital flight aboard Blue Origin's New Shepard vehicle to collect precision vibratory accelerometry data. The Space Acceleration Measurement System (SAMS) sensor head was mounted inside of a Blue Origin single payload locker inside of the crew capsule. This paper describes the configuration, capture, and analysis of the SAMS data from this flight along with other, related flight log information provided by Blue Origin. Three overlapping periods during the flight were identified and characterized to provide future users of the platform with insight into options that may prove suitable for their research needs. Average accelerations in the Post-Separation Period were consistent with other low-g research platforms, while the shorter Microgravity Period in the middle of the flight showed ultra-quiet vibratory acceleration environments. Researchers can consider this microgravity quality versus time a tradeoff in their experimental designs.

Ground based ISS payload microgravity disturbance assessments

In order to verify that the International Space Station (ISS) payload facility racks do not disturb the microgravity environment of neighboring facility racks and that the facility science operations are not compromised, a testing and analytical verification process must be followed. Currently no facility racks have taken this process from start to finish. The authors are participants in implementing this process for the NASA Glenn Research Center (GRC) Fluids and Combustion Facility (FCF). To address the testing part of the verification process, the Microgravity Emissions Laboratory (MEL) was developed at GRC. The MEL is a 6 degree of freedom inertial measurement system capable of characterizing inertial response forces (emissions) of components, sub-rack payloads, or rack-level payloads down to 10 - 7 g 's. The inertial force output data, generated from the steady state or transient operations of the test articles, are utilized in analytical simulations to predict the on-orbit vibratory environment at specific science or rack interface locations. Once the facility payload rack and disturbers are properly modeled an assessment can be made as to whether required microgravity levels are achieved. The modeling is utilized to develop microgravity predictions which lead to the development of microgravity sensitive ISS experiment operations once on-orbit. The on-orbit measurements will be verified by use of the NASA GRC Space Acceleration Measurement System (SAMS). The major topics to be addressed in this paper are: (1) Microgravity Requirements, (2) Microgravity Disturbers, (3) MEL Testing, (4) Disturbance Control, (5) Microgravity Control Process, and (6) On-Orbit Predictions and Verification.

Contact angle hysteresis generated by the residual gravitational field of the Space Shuttle

When the two fluid phases of a substance are present in a cylinder, one of the possible equilibrium configurations is for two liquid phases to be present, one above the vapor phase and one below. If surface tension dominates the gravitational effects, the two-interface configuration is the thermodynamically favored one. When the system is in the two-interface configuration, the difference in pressure between the two liquid phases is predicted to be the same as it would have been had no vapor phase been present! Although the pressure profile cannot be measured directly, it is predicted to cause the contact angle value at the upper three-phase line to be smaller than that at the lower three-phase line. This difference in contact angles can be measured, and from the measured values, the theory can be used to determine the value of the gravitational intensity. In an experiment conducted on a Space Shuttle flight, the configuration adopted when glass cylinders of different diameters were each partially filled with water was recorded. The fluid in each cylinder was found to adopt the two-interface configuration, as predicted. A 56 mm diam glass cylinder that had a height of 86 mm was observed to have a contact angle at the upper three-phase line of 6.7±1.3° and 26.5±4.0° at the lower. The value of the gravitational intensity inferred from the measured contact angles agrees with that reported from the (NASA) electronic Space Acceleration Measurement System (SAMS). This agreement supports the prediction that contact angle hysteresis is generated by a difference in pressure between the two liquid phases of the two-interface configuration.

Low-gravity environment of the Mir Space Station

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.