Special Coverage


Performing Launch Depressurization Test on Large Test Articles Using Two Vacuum Chambers in Tandem

NASA’s Jet Propulsion Laboratory, Pasadena, California Two vacuum chambers were used in tandem to perform a launch depressurization test. The test article was mounted in a 10-ft (≈3 m) Vertical Vacuum Chamber (Chamber 248-10). The 25-ft (≈7.6-m) Space Simulator (Chamber 150-25) was rough-pumped and used for ullage.

Posted in: Briefs, TSP


Pyramid Micro-Electrofluidic-Spray Propulsion Thruster with Integrated Attitude and Thrust Vector Control

NASA’s Jet Propulsion Laboratory, Pasadena, California A micro-electrofluidic-spray propulsion (MEP) system was built on a micro scale, in which arrays of hundreds of nano-thrusters are etched on silicon wafers like ICs, only a centimeter on a side. Many dozens of these thruster chips can be arrayed to form a macro-thruster of finite and significant thrust. Approximately 300 centimeter-square, 100-micro-Newton micro-thrusters are arrayed in a square pyramidal structure. The pyramid is of shallow obliquity, with no more than 20° offset from the spacecraft face. This small angular offset is sufficient to provide thrust vector control (TVC) for the thruster.

Posted in: Briefs


Sampling Mechanism for a Comet Sample Return Mission

A similar sampling mechanism could be deployed in dangerous situations on Earth. Goddard Space Flight Center, Greenbelt, Maryland Sample return missions have the ability to vastly increase scientific understanding of the origin, history, current status, and resource potential of solar system objects including asteroids, comets, Mars, and the Moon. However, to make further progress in understanding such bodies, detailed analyses of samples are needed from as many bodies as possible. A standoff sample collection system concept has been developed that would quickly obtain a sample from environments as varied as comets, asteroids, and permanently shadowed craters on the Moon, using vehicles ranging from traditional planetary spacecraft to platforms such as hovering rotorcraft or balloons on Mars, Venus, or Titan. The depth of penetration for this harpoon- based hollow collector was experimentally determined to be proportional to the momentum of the penetrator in agreement with earlier work on the penetration of solid projectiles. A release mechanism for the internal, removable sample cartridge was tested, as was an automatic closure system for the sample canister.

Posted in: Briefs, TSP, Machinery & Automation, Monitoring


An Operationally Based Vision Assessment Simulator for Domes

Applications include remote visualization, flight simulation, virtual environments, and planetariums. Ames Research Center, Moffett Field, California The work described here is part of the U.S. Air Force-sponsored Operational Based Vision Assessment (OBVA) program that has been tasked with developing a high-fidelity flight simulation laboratory to determine the relationship between human vision and performance in simulated operationally relevant tasks. The OBVA simulator was designed and built to provide the Air Force School of Aerospace Medicine (USAFSAM) with a scientific testing laboratory to study human vision and testing standards.

Posted in: Briefs, Computers, Simulation Software


Ad Hoc Adaptive Pitch Axis Pilot Model

Neil A. Armstrong Flight Research Center, Edwards, California Flight research has shown that adaptive flight control systems can be susceptible to adverse pilot-controller interactions, including pilot-in-the-loop oscillations (PIO). Conventional PIO analysis is performed using a static pilot model and a linear, time-invariant model of the aircraft and its control system. For aircraft with time-varying dynamics such as damage or failure, pilot technique may change rapidly to maintain control. An adaptive pilot model can be used to evaluate potential interactions between the pilot and an adaptive flight controller. An ad hoc algorithm was designed for the real-time adaptation of a pilot model describing a pitch angle gross acquisition task. The pilot model consists of an adaptive gain and a fixed time delay. The adaptive gain is adjusted based on the magnitude of the tracking error and the aggressiveness of the response. The algorithm was shown to match human pilot adaptation (simulation) to changes in dynamics including nominal, increased, and decreased loop gain; increased and decreased damping; and increased and decreased natural frequency. The algorithm also exhibits the classic pilot crossover theory response of –20dB/dec@0dB. Unique features of the pilot model are: Continuous adaptations in which gain adjustments are updated continuously and naturally converge to a solution when the aircraft dynamics are time-invariant. Bidirectional adaptation in which the pilot gain increases or decreases as required. Explicit modeling of the pilot’s ability to phase-correlate command/response. Adaptation is normalized to be proportional to the piloting task. This work was done by Curt Hanson of Armstrong Flight Research Center. For more information, contact the Armstrong Technology Transfer Office at 661-276-3967. DRC-012-007

Posted in: Briefs, Aviation


Development of a Turnkey Clear Air Turbulence Detection System

Turbulence is determined via three infrasonic microphones. Langley Research Center, Hampton, Virginia Currently, the only available means of reporting clear air turbulence (CAT) is the pilot report (PIREP), whereby a pilot experiencing turbulence reports their location and associated data. In this report, a system is proposed that would allow the detection of CAT through infrasonic emissions.

Posted in: Briefs, TSP, Aviation, Detectors


Lunar Cold Trap Contamination by Landing Vehicles

Software and methods are developed to assess the magnitude and distribution of lunar surface contamination caused by the engine exhaust of a landing vehicle. John F. Kennedy Space Center, Florida The emerging interest in lunar mining poses a threat of contamination to pristine craters at the lunar poles, which act as cold traps for water, and may harbor other valuable minerals. Lunar Prospector type missions will be looking for volatile (molecular) compounds that may be masked by the exhaust gases from landing vehicle engines. The possible self-contamination of the landing site could negate the scientific value of the soil samples taken in the vicinity of the landing site. Self-contamination may also lead to false-positive readings of resources available on the lunar surface. This innovation addresses the software and methods needed to assess the magnitude and distribution of lunar surface contamination caused by the engine exhaust of landing vehicles on known or planned descent trajectories.

Posted in: Briefs, TSP


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