Motion Control

Evaluation of Rail Gun Technology for Launch Assist of Air-Breathing Rockets

John F. Kennedy Space Center, Florida A prototype horizontal electromagnetic rail launcher has been demonstrated along with a corresponding theory. This system builds out of published work in augmented rail guns, but modifies this technology so that the motor can operate for seconds rather than milliseconds, and provide low acceleration (such as might be needed to launch an aircraft) rather than the extreme accelerations seen in the guns. The final system operates off of relatively low voltages (tens of volts), but with substantial currents. A lab bench prototype has been constructed and operated, demonstrating 13 Gs acceleration of a small 230-gram sled.

Posted in: Briefs, Motors & Drives

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Using Harmonics to Control Flutter in Wings with Electrical Motors

This control system concept applies principles of forced aeroelasticity to distributed electric propulsion systems. Armstrong Flight Research Center, Edwards, California As aeronautics engineers develop innovative distributed electric propulsion systems, they face new challenges in ensuring that these innovative aircraft are safe as well as fuel efficient. In particular, these systems involve a large number of electrically driven fan motors mounted across a wing that induce vibrations that negatively affect the aircraft’s stability. These vibrations cause problems regardless of whether the motors are bottom-mounted, top-mounted, or wing-embedded.

Posted in: Briefs, Motors & Drives

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Micropulse Detonation Rocket Engine for Nano-Satellite Propulsion

Goddard Space Flight Center, Greenbelt, Maryland An efficient propulsion system would use a micropulse detonation rocket engine (–PDRE) for nano-satellite maneuverability in space. Technical objectives are to design, build, and conduct a small detonation tube experiment in order to explore the feasibility of using –PDRE for propelling a nano-satellite. The plan is to study the requirement and predict the performance of –PDRE using various candidate propellants, as well as to conduct ground experiments, demonstrate useful thrust, and measure the specific impulse in a two-year time frame, so that a follow-on project can be proposed in a future NRI Center Innovation Fund.

Posted in: Briefs, TSP

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Experimental Testbed for 1-MW Turboelectric Distributed Propulsion Aircraft

A low-cost glider design mitigates risk in conducting experiments for cutting-edge “green” aircraft concepts. Armstrong Flight Research Center, Edwards, California Researchers at NASA’s Armstrong Flight Research Center are developing a concept aircraft for testing turbo-electric distributed propulsion (TeDP) experiments. TeDP generally involves providing thrust to an aircraft via wing-mounted ducted electric fans, which consist of an electric motor, a fan, stators, and other components surrounded by cylindrical ducting within a fan case. The fan motors are powered by a combined battery and turboelectric generator system. To sufficiently power an aircraft approximately 50 ft (≈15 m) in length and with a gross weight of 25,000 lb (≈11,340 kg), this system must be capable of generating 1 MW of power.

Posted in: Briefs, Aviation, Motors & Drives

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Propellant Loading Visualization Software

Monitoring of complex propulsion pressure systems has been simplified with colors. Goddard Space Flight Center, Greenbelt, Maryland Complex pressure systems are utilized during testing in the propulsion branch as well as during the propellant loading stage of a mission. Keeping track of the state of such a system becomes more difficult as the complexity of such a system increases, and when extensive procedures are being followed. A book-keeping system is needed for visualizing these complex systems.

Posted in: Briefs, TSP

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Robust Gimbal System for Small-Payload Manipulation

This is a low-mass, small-volume gimbal unit. NASA’s Jet Propulsion Laboratory, Pasadena, California Spaceborne gimbal systems are typically bulky with large footprints. Such a gimbal system may consist of a forked elevation stage rotating on top of the azimuth motor, and occupy a large volume. Mounting flexibility of such a system may be limited.

Posted in: Articles, Briefs, TSP, Motors & Drives

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A Phase-Changing Pendulum to Control Spherical Robots and Buoy Sensors

The pendulum adds new flexibility to motion control. NASA’s Jet Propulsion Laboratory, Pasadena, California A novel mechanical control system has been proposed for spherical robots to be used as multifunctioning sensor buoys in areas with ambient forces such as winds or currents. The phase-changing pendulum has been specifically designed for Moballs, a self-powered and controllable multifunctioning spherical sensor buoy to be used in the Arctic and Antarctica, or in other solar system planets or moons with atmosphere, such as Mars or Titan. The phase-changing pendulum has been designed to function in different phases: 1) When used as the spherical buoy, the Moball needs to take advantage of external forces such as the wind for its mobility. With no constraints, it could keep the center of mass in the geometric center of the sphere to facilitate the sphere’s movement. 2) However, as soon as the Moball needs to slow down or stop, the sphere’s center of mass can be lowered. 3) Furthermore, the phase-changing pendulum could lean to the sides, thereby changing the direction of the Moball by biasing its center of mass to the corresponding side. The Moballs could take advantage of such a novel phase-changing pendulum to go as fast as possible using the ambient winds, and to stop or steer away when facing hazardous objects or areas (such as the gullies), or when they need to stop in an area of interest in order to perform extensive tests. It is believed that this is the very first time that a pendulum has been suggested to control a spherical structure where both the length and the angle of the pendulum are adjustable in order to control the sphere. 4) Finally, the phase-changing pendulum could also control the sphere in the absence of wind. The spherical sensor buoys or Moballs could use the stored harvested energy (e.g., from sunlight or earlier wind-driven motions) to move the phase-changing pendulum and create torque, and make the spherical sensor buoys initiate rolling with the desired speed and direction. This is especially useful when the spheres need to get close to an object of interest in order to examine it.

Posted in: Articles, Briefs

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