Special Coverage


Electrochemical Systems Generate Ozone and Ozonated Water

The only inputs needed are electric energy and mildly pressurized water. Improved electrochemical systems for generating ozone (in gaseous form and/or dissolved in water) have been invented for use in disinfection and in industrial processes in which the unique, highly oxidizing chemical properties of ozone are needed. More accurately, these systems generate oxygen along with high (relative to prior systems) concentrations of ozone and, optionally, with hydrogen as a byproduct. These systems contain no pumps and very few moving or wearing components, and the only inputs needed to operate these systems are electric energy and water supplied at mild pressure. Moreover, these systems can readily be designed and constructed on any scale (e.g., from research laboratory to industrial) to suit a wide variety of applications.

Posted in: Physical Sciences, Briefs


Thermally Conductive Metal-Tube/Carbon-Composite Joints

Modified solder joints accommodate differential thermal expansion. An improved method of fabricating joints between metal and carbon-fiber-based composite materials in lightweight radiators and heat sinks has been devised. Carbon-fiber-based composite materials have been used in such heat-transfer devices because they offer a combination of high thermal conductivity and low mass density. Metal tubes are typically used to carry heat-transfer fluids to and from such heat-transfer devices. The present fabrication method helps to ensure that the joints between the metal tubes and the composite-material parts in such heat-transfer devices have both (1) the relatively high thermal conductances needed for efficient transfer of heat and (2) the flexibility needed to accommodate differences among thermal expansions of dissimilar materials in operation over wide temperature ranges.

Posted in: Manufacturing & Prototyping, Briefs


Internal-Combustion Engines With Ringless Carbon Pistons

Efficiencies would be higher and weights lower than those of conventional engines. Internal-combustion engines would be constructed with cylinders and ringless pistons made of lightweight carbon/carbon composite materials, according to a proposal. This proposal is a logical extension of previous research that showed that engines that contain carbon/carbon pistons with conventional metal piston rings running in conventional metal cylinders perform better than do engines with conventional aluminum-alloy pistons. The observed performance improvement (measured as increased piston life during high-performance operation) can be attributed mainly to the low thermal expansion of the carbon-carbon composite. Carbon-carbon pistons can continue to operate under thermal loads that cause aluminum pistons to seize or sustain scuffing damage due to excessive thermal growth and thermal distortion.

Posted in: Materials, Briefs


Pneumatic Accelerator for Launching a Spacecraft

A report proposes the development of a ground-based launch-assist apparatus that would accelerate a spacecraft to a speed of about 270 m/s. The apparatus would include a track along which the spacecraft would ride on a sled coupled to a large piston driven by compressed air along a tube (more precisely, a concrete tunnel lined with stainless-steel sheet) below the track. The connection between the sled and the piston would be made via a coupling plate that would slide along a slot on top of the tube. The slot would seal after passage of the coupling plate. As described thus far, the apparatus could be characterized as a modern, high-acceleration, high-speed version of pneumatic drives with slot connections to rail cars that were used in Europe during the 1840s.

Posted in: Mechanics, Mechanical Components, Briefs, TSP


Remote Agent as Applied to the Deep Space 1 Spacecraft

A report presents updated information about the Remote Agent — a reusable artificial-intelligence software system that was described in “A Remote Agent Prototype for Spacecraft Autonomy” (NPO-19992), NASA Tech Briefs, Vol. 21, No. 3 (March 1997), page 106. This system was conceived to enable spacecraft to operate robustly with minimal human supervision, even in the face of hardware failures or unexpected events. It also is expected to offer similar benefits for communication networks, chemical plants, and other complex systems on Earth.

Posted in: Information Sciences, Briefs


DNS of a Supercritical H2/O2 Mixing Layer

This report discusses direct numerical simulations (DNS) of a mixing layer between supercritical flows of oxygen and hydrogen. The governing conservation equations were those of fluctuation- dissipation (FD) theory, in which low-pressure typical transport properties (viscosity, diffusivity and thermal conductivity), are complemented, at high pressure, by a thermal-diffusion factor.

Posted in: Physical Sciences, Briefs


Goal-Based Fault Tolerance for Spacecraft Systems

A report discusses the concept of goal-based fault tolerance as implemented in NASA’s Mission Data System (MDS), which is a developmental architecture for unified flight, test, and ground software that is intended to be adaptable to a variety of next-generation deep-space missions. In goal-based fault tolerance, unlike in prior approaches to fault tolerance, it is not assumed that faults that necessitate deviations from prescribed sequences of commands will occur infrequently; instead, it is assumed that unpredictable conditions, including faults, can arise at any time, and fault tolerance is incorporated as an intrinsic feature of every aspect of system design in a unified approach to ensuring robust system behavior.

Posted in: Information Sciences, Briefs, TSP