Tech Briefs

The TechSat 21 Autonomous Sciencecraft Experiment

Software has been developed to perform a number of functions essential to autonomous operation in the Autonomous Sciencecraft Experiment (ASE), which is scheduled to be demonstrated aboard a constellation of three spacecraft, denoted TechSat 21, to be launched by the Air Force into orbit around the Earth in January 2006. A prior version of this software was reported in "Software for an Autonomous Constellation of Satellites" (NPO-30355), NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 44.

Posted in: Briefs, TSP, Software

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Software for Analyzing Laminar-to-Turbulent Flow Transitions

Langley Stability and Transition Analysis Codes (LASTRAC) is a set of engineering software tools developed with the C++ language and modern software technologies for use in analyzing transition from laminar to turbulent flows. LASTRAC is a product of on-going NASA Langley research projects related to transition flow physics modeling and simulations. It is intended to be a set of easy-to-use engineering tools that can be applied to routine engineering design studies. At the current stage, LASTRAC is capable of performing transition calculations based on linear stability theory (LST) or linear and nonlinear parabolized stability equations (PSE) for a broad range of flow regimes and configurations of interest for the design of low-speed as well as supersonic and hypersonic vehicles. At present, LASTRAC is limited to two-dimensional, axisymmetric, or infinite swept-wing boundary layers. Options for general three-dimensional boundary layers are currently under development. The LST option makes it possible to perform traditional N-factor transition correlation. Linear and nonlinear PSE are used to track instability wave evolution from small-amplitude till early transition stage in a high-fidelity manner. It is planned to incorporate modules in LASTRAC that models the receptivity (the process by which perturbations are introduced into laminar boundary-layer flow) and late stage of the transition process. These software modules are intended to enable LASTRAC to perform computations for different stages of laminar-to-turbulent transition in an integrated fashion.

Posted in: Briefs, TSP, Software

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Lidar for Guidance of a Spacecraft or Exploratory Robot

A report describes the Laser Mapper (LAMP) — a lightweight, compact, low-power lidar system under development for guidance of a spacecraft or exploratory robotic vehicle (rover) at Mars or another planet. The LAMP is intended especially for use during rendezvous of two spacecraft in orbit, for mapping terrain during descent and landing of a spacecraft, for capturing a sample that has been launched into orbit, or navigation and avoidance of obstacles by a rover traversing terrain. The LAMP includes a laser that emits high-power, short light pulses. The laser beam is aimed in azimuth and elevation by use of a mirror on a two-axis gimbal, which scans the beam across a field of regard. Light reflected by a target is collected by a telescope, and the distance to the target is determined by measuring the round-trip travel time for reflected light pulses. The distance information is combined with directional information to construct a three-dimensional map of targets in the field of regard.

Posted in: Briefs, TSP, Electronics & Computers

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Electrochemical, H2O2-Boosted Catalytic Oxidation System

This system offers several advantages over O2-boosted systems.An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

Posted in: Briefs, Physical Sciences

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Permanent Sequestration of Emitted Gases in the Form of Clathrate Hydrates

Hydrates would be formed under natural conditions. Underground sequestration has been proposed as a novel method of permanent disposal of harmful gases emitted into the atmosphere as a result of human activity. The method was conceived primarily for disposal of carbon dioxide (CO2, greenhouse gas causing global warming), but could also be applied to CO, H2S, NOx, and chorofluorocarbons (CFCs, which are super greenhouse gases). The method is based on the fact that clathrate hydrates (e.g., CO2×6H2O) form naturally from the substances in question (e.g., CO2) and liquid water in the pores of sub-permafrost rocks at stabilizing pressures and temperatures. The proposed method would be volumetrically efficient: In the case of CO2, each volume of hydrate can contain as much as 184 volumes of gas.

Posted in: Briefs, TSP, Physical Sciences

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Miniature Radioisotope Thermoelectric Power Cubes

These devices could supply power at extremely low temperatures for years. Cube-shaped thermoelectric devices energized by a particles from radioactive decay of 244Cm have been proposed as long-lived sources of power. These power cubes are intended especially for incorporation into electronic circuits that must operate in dark, extremely cold locations (e.g., polar locations or deep underwater on Earth, or in deep interplanetary space). Unlike conventional radioisotope thermoelectric generators used heretofore as central power sources in some spacecraft, the proposed power cubes would be small enough (volumes would range between 0.1 and 0.2 cm3) to play the roles of batteries that are parts of, and dedicated to, individual electronic-circuit packages. Unlike electrochemical batteries, these power cubes would perform well at low temperatures. They would also last much longer: given that the half-life of 244Cm is 18 years, a power cube could remain adequate as a power source for years, depending on the power demand in its particular application.

Posted in: Briefs, TSP, Physical Sciences

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Miniature Robotic Spacecraft for Inspecting Other Spacecraft

A report discusses the Miniature Autonomous Extravehicular Robotic Camera (Mini AERCam) — a compact robotic spacecraft intended to be released from a larger spacecraft for exterior visual inspection of the larger spacecraft. The Mini AERCam is a successor to the AERCam Sprint — a prior miniature robotic inspection spacecraft that was demonstrated in a space-shuttle flight experiment in 1997. The prototype of the Mini AERCam is a demonstration unit having approximately the form and function of a flight system. The Mini AERCam is approximately spherical with a diameter of about 7.5 in. (»19 cm) and a weight of about 10 lb (»4.5 kg), yet it has significant additional capabilities, relative to the 14-in. (36-cm), 35-lb (16-kg) AERCam Sprint. The Mini AERCam includes miniaturized avionics, instrumentation, communications, navigation, imaging, power, and propulsion subsystems, including two digital video cameras and a high-resolution still camera. The Mini AERCam is designed for either remote piloting or supervised autonomous operations, including station keeping and point-to-point maneuvering. The prototype has been tested on an air-bearing table and in a hardware-in-the-loop orbital simulation of the dynamics of maneuvering in proximity to the International Space Station.

Posted in: Briefs, TSP, Mechanical Components

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