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NASA NTRS2013

Advanced Neutron Spectrometer

Energetic neutron measurements remain a challenge for space science investigations and radiation monitoring for human exploration beyond LEO. We are investigating a new composite scintillator design that uses Li6 glass scintillator embedded in a PVT block. A comparison between Li6 and Boron 10 loaded scintillators are being studied to assess the advantages and shortcomings of these two techniques. We present the details of the new Li6 design and results from the comparison of the B10 and Li6 techniques during exposures in a mixed radiation field produced by high energy protons interacting in a target material.

Christl, Mark↗

NASA NTRS2007

Inductive Linear-Position Sensor/Limit-Sensor Units

A new sensor provides an absolute position measurement. A schematic view of a motorized linear-translation stage that contains, at each end, an electronic unit that functions as both (1) a non-contact sensor that measures the absolute position of the stage and (2) a non-contact equivalent of a limit switch that is tripped when the stage reaches the nominal limit position. The need for such an absolute linear position-sensor/limit-sensor unit arises in the case of a linear-translation stage that is part of a larger system in which the actual stopping position of the stage (relative to the nominal limit position) must be known. Because inertia inevitably causes the stage to run somewhat past the nominal limit position, tripping of a standard limit switch or other limit sensor does not provide the required indication of the actual stopping position. This innovative sensor unit operates on an electromagnetic-induction principle similar to that of linear variable differential transformers (LVDTs)

Alhom, Dean↗

NASA NTRS2007

Programmable Thermostat Module Upgrade for the Multi-Purpose Logistics Module

The STS-121/ULF1.1 mission was the maiden flight of the Programmable Thermostat Module (PTM) system used to control the 28 V shell heaters on the Multi-Purpose Logistics Module (MPLM). These PTMs, in conjunction with a Data Recorder Module (DRM), provide continuous closed loop temperature control and data recording of MPLM on-orbit heater operations. This paper will discuss the hardware design, development, test and verification (DDT&V) activities performed at the Marshall Space Flight Center (MSFC) as well as the operational implementation and mission performance.

Clark, Dallas↗

NASA NTRS2004

The Deflection Plate Analyzer: A Technique for Space Plasma Measurements Under Highly Disturbed Conditions

A technique has been developed to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The present method is an extension of the capabilities of the Differential Ion Flux Probe (DIFP) to include a mass measurement that does not include either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This reduces the complexity and expense of instrument fabrication, testing, and integration of flight hardware as compared to classical mass analyzers. The new instrument design is called the Deflection Plate Analyzer (DPA) and can deconvolve multiple ion streams and analyze each stream for ion flux intensity (density), velocity (including direction of motion), mass, and temperature (or energy distribution). The basic functionality of the DPA is discussed. The performance characteristics of a flight instrument as built for an electrodynamic tether mission, the Propulsive Small Expendable Deployer System (ProSEDS), and the instrument s role in measuring key experimental conditions are also discussed.

Wright, Kenneth H., Jr.↗

NASA NTRS2003

The Deflection Plate Analyzer: A Technique for Space Plasma Measurements Under Highly Disturbed Conditions

A technique has been developed to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The present method is an extension of the capabilities of the Differential Ion Flux Probe (DIFP) to include a mass measurement that does not include either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This reduces the complexity and expense of instrument fabrication, testing, and integration of flight hardware as compared to classical mass analyzers. The new instrument design is called the Deflection Plate Analyzer (DPA) and can deconvolve multiple ion streams and analyze each stream for ion flux intensity (density), velocity (including direction of motion), mass, and temperature (or energy distribution). The basic functionality of the DPA is discussed. The performance characteristics of a flight instrument as built for an electrodynamic tether mission, the Propulsive Small Expendable Deployer System (ProSEDS), and the instrument s role in measuring key experimental conditions are also discussed.

Wright, Kenneth H., Jr.↗

NASA NTRS2001

RADX34: A Future-X Demonstration of Autonomous Robust Abort Technologies on the X-34

The Charles Stark Draper Laboratory, Inc. has been conducting the RADX-34 Future-X Pathfinder Flight Demonstration experiment under the direction of the NASA Marshall Space Flight Center. The Future-X experiment will use the X-34 to demonstrate autonomous abort technologies needed for the next generation of reusable launch vehicles. This project will involve integration of real-time abort mission planning algorithms with the existing guidance and control to provide abort coverage for the low-Mach flights of the X-34. This paper describes the design and capability of the abort planner three months prior to the conclusion of its development. The mission planner described herein is able to respond to loss of thrust, determine which runways can be reached within the vehicle constraints, and designate an appropriate landing site. This project, when complete, will mark the first step in the development of the Next Generation of Guidance and Control (NGGC) autonomous algorithms. NGGC algorithms will help ensure the second generation of reusable launch vehicles will meet their cost, safety and reliability requirements.

Aron, Edward C.↗

NASA NTRS1999

NASA's Reusable Launch Vehicle Technologies: A Composite Materials Overview

A materials overview of the NASA's Earth-to-Orbit Space Transportation Program is presented. The topics discussed are: Earth-to-Orbit Goals and Challenges; Space Transportation Program Structure; Generations of Reusable Launch Vehicles; Space Transportation Derived Requirements; X 34 Demonstrator; Fastrac Engine System; Airframe Systems; Propulsion Systems; Cryotank Structures; Advanced Materials, Fabrication, Manufacturing, & Assembly; Hot and Cooled Airframe Structures; Ceramic Matrix Composites; Ultra-High Temp Polymer Matrix Composites; Metal Matrix Composites; and PMC Lines Ducts and Valves.

Clinton, R. G., Jr.↗

NASA NTRS1994

Active Inertial Vibration Isolators And Dampers

Report describes development of active inertial vibration isolators and dampers in which actuators electromagnet coils moving linearly within permanent magnetic fields in housings, somewhat as though massive, low-frequency voice coils in loudspeakers. Discusses principle of operation, electrical and mechanical considerations in design of actuators, characteristics of accelerometers, and frequency responses of control systems. Describes design and performance of one- and three-degree-of-freedom vibration-suppressing system based on concept.

Laughlin, Darren↗

NASA NTRS1992

Digital active material processing platform effort (DAMPER), SBIR phase 2

Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

Blackburn, John↗