Mechanical Components

Design Concept for a Nuclear Reactor-Powered Mars Rover

A report presents a design concept for an instrumented robotic vehicle (rover) to be used on a future mission of exploration of the planet Mars. The design incorporates a nuclear fission power system to provide long range, long life, and high power capabilities unachievable through the use of alternative solar or radioisotope power systems. The concept described in the report draws on previous rover designs developed for the 2009 Mars Science laboratory (MSL) mission to minimize the need for new technology developments.

Posted in: Mechanical Components, Briefs, TSP

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Several Developments in Space Tethers

Five reports address different aspects of development of tethers to be deployed from spacecraft in orbit around the Earth. The first report discusses proposed optoelectronic tracking of retroreflective objects located at intervals or of retroreflective coats along the entire length of a tether to measure lateral motions. The second report describes digitally controlled spooling machinery that retracts or extends a tape tether at controlled speed and tension in the spool isolated from uncontrolled tension on the outside. The third report discusses part of this machinery that pivots to accommodate misalignments between the deployed and spooled portions of the tether and contains rollers used to exert tension and speed control. The fourth report discusses aspects of designs of proposed electrodynamic tethers, which would be electrically conductive and would interact with the magnetic field of the Earth to exert forces to modify orbits of deploying spacecraft. The fifth report discusses electrical aspects of designs of electrodynamic tape tethers, including the use of solar cells or motional electromagnetic force to generate currents in tethers and the use of electron emitters and electron and ion collectors at opposite ends of tethers to make electrical contact with the thin plasma in surrounding space.

Posted in: Mechanical Components, Briefs

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Development of Vapor-Phase Catalytic Ammonia Removal System

A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars. The VPCAR process is implemented by a system of highly integrated design in which some power consumption is accepted as a cost of minimizing the volume and mass of a wastewater-processing system and eliminating the need to resupply water. The core of the system is a wiped-film rotating-disk (WFRD) evaporator, which removes inorganic salts and nonvolatile organic compounds from the wastewater stream and concentrates these contaminants into a recycle-and-bleed stream. The WFRD evaporator is also part of a subsystem that distills water from the wastewater stream. This subsystem operates in a vacuum-vapor/compression distillation configuration in the temperature range from 20 to 65 °C. Volatile organic compounds and ammonia, distilled along with water, are oxidized to CO2, H2O, and N2O in a packed-bed, hightemperature catalytic reactor placed at the outlet of the vapor-phase compressor of the distillation subsystem. A VPCAR engineering demonstration unit is expected to be included in a humanrated simulation of a mission to Mars.

Posted in: Mechanical Components, Briefs, TSP

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Flexure Rings for Centering Lenses

The rings accommodate fabrication tolerances and thermal-expansion mismatches. Specially shaped mounting rings keep lenses precisely centered, regardless of temperature, in the lens housings of cameras and other optical systems. These rings feature (1) well-defined contact spots for alignment, plus (2) relieved surfaces that form flexures to accommodate small manufacturing tolerances and differences among the thermal expansions of lenses, lens housings, and the rings themselves. These rings are made by numerically controlled machining of recently developed clean, strong, machinable plastics.

Posted in: Mechanics, Mechanical Components, Briefs, TSP

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Variable-Specific-Impulse Magnetoplasma Rocket

This rocket is expected to enable long-term human exploration of outer space. Johnson Space Center has been leading the development of a high-power, electrothermal plasma rocket — the variable- specific-impulse magnetoplasma rocket (VASIMR) — that is capable of exhaust modulation at constant power. An electrodeless design enables the rocket to operate at power densities much greater than those of more conventional magnetoplasma or ion engines. An aspect of the engine design that affords a capability to achieve both high and variable specific impulse (Isp) places the VASIMR far ahead of anything available today. Inasmuch as this rocket can utilize hydrogen as its propellant, it can be operated at relatively low cost.

Posted in: Mechanics, Mechanical Components, Briefs

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Water Containment Systems for Testing High-Speed Flywheels

Water-filled containers are stacked like bricks. Water-filled containers are used as building blocks in a new generation of containment systems for testing high-speed flywheels. Such containment systems are needed to ensure safety by trapping high-speed debris in the event of centrifugal breakup or bearing failure. Traditional containment systems for testing flywheels consist mainly of thick steel rings. While steel rings are effective for protecting against fragments from conventional and relatively simple metal flywheels, they are also expensive. Moreover, it is difficult and expensive to configure steel-ring containment systems for testing of advanced flywheel systems that can include flywheels made of composite materials, counter-rotating flywheels, and/or multiple flywheels rotating about different axes. In contrast, one can quickly, easily, and inexpensively stack waterfilled containers like bricks to build walls, (and, if needed, floors, and ceilings) of sufficient thickness to trap debris traveling in any debris traveling in any possible direction at the maximum possible kinetic energy that could be encountered in testing a given flywheel system.

Posted in: Mechanical Components, Briefs, TSP

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System Finds Horizontal Location of Center of Gravity

Mass and center-of-mass data are updated at a rate of = 267 Hz. An instrumentation system rapidly and repeatedly determines the horizontal location of the center of gravity of a laboratory vehicle that slides horizontally on three air bearings (see Figure 1). Typically, knowledge of the horizontal center-of- mass location of such a vehicle is needed in order to balance the vehicle properly for an experiment and/or to assess the dynamic behavior of the vehicle.

Posted in: Mechanical Components, Briefs, TSP

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