Mechanical & Fluid Systems

Precise Air Bearings Redesigned

A simplified design affords low friction at minimum airflow. Highly precise air bearings for suspending objects over an epoxy flat floor in a laboratory have been developed. These bearings float on airgaps 3 to 5 mil (about 0.08 to 0.13 mm) thick. They are modern versions of precise air bearings, developed during the 1960s, that offer a working coefficient of friction of only 1/16,000. The basic design of these bearings can be scaled easily for different loads and airflows.

Posted in: Mechanics, Briefs, TSP

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Variable Submillimeter-Wave Delay Line for Cryogenic Use

Stiffness, size, vacuum adhesion, range, and number of parts were considered in designing this device. A variable delay line is being developed as part of a far-infrared or submillimeter- wavelength interferometer that would operate in a vacuum in the cryogenic temperature range. No such delay line for spatial interferometry has previously been built for operation under these conditions.

Posted in: Mechanics, Briefs, TSP

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Emergency Tether-Deployment-and-Recoil-Mitigating Systems

A report describes an emergency tether-deployment (ETD) system designed to minimize the harm caused by two events that can occur during deployment of tethered payloads from a space shuttle in orbit. One such event is snagging of the tether during payout while the payload is near the shuttle, causing rebound of the shuttle and payload toward each, thus possibly causing a collision. The other event is recoil of a tether that must be cut while it is under tension. If not suppressed, the recoil can cause the tether to become tangled around the shuttle. The ETD system includes a tether wound on a spool in a standard pattern that minimizes friction during payout, plus a rotating-arm mechanism that prevents snagging. The ETD system can be either (1) used as a primary deployment system or (2) activated automatically through breakage of a tether tiedown in the event of a snag or when the payload is at a safe distance from the shuttle. To suppress recoil, a core of solder is inserted along part of the length of the tether. When a wave of recoil reaches this part, the solder absorbs most of the recoil energy.

Posted in: Machinery & Automation, Briefs, TSP

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Mechanism for Docking a Miniature Spacecraft

This report discusses a proposed docking mechanism to be located in a small hangar on the outside of the International Space Station (ISS). The mechanism would enable docking of a miniature robotic spacecraft (or free flyer) that would carry a video camera and would operate in the vicinity of the ISS. The docking mechanism would include, among other things, (1) an electromagnet for actuation, (2) electrical connectors for transferring data to and from the free flyer and recharging the freeflyer power system, and (3) a quick-disconnect (QD) coupling for recharging a supply of gaseous N2. Once the free flyer had maneuvered into approximate docking alignment, an electromagnet in the mechanism would attract a ferromagnetic plate on the free flyer strongly enough to pull the free flyer in from a distance of as much as several inches (≈10 cm). The mechanism would include surfaces that would mate with surfaces on the free flyer to correct any misalignment as the free flyer was pulled in. Once docked, the free flyer would be held in place by either spring-loaded cam locks or the QD coupling itself. Data, power, and N2 can then be transferred to the vehicle.

Posted in: Machinery & Automation, 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, Briefs, TSP

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Cylindrical Shape-Memory Rotary/Linear Actuator

A shape-memory ribbon is wrapped around a cylinder to build up length. A compact actuator generates rotary or linear motion with a large torque or force, respectively. The original version of this actuator is designed to pull a wedge that, until pulled, prevents retraction of the proposed extended nose landing gear of the space shuttle. The original version is also required to fit into a volume that is severely limited by the size of the landing-gear assembly. The basic actuator design could be adapted to other applications in which there are requirements for compact, large-force actuators with similar geometries.

Posted in: Mechanics, Briefs, TSP

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Further Advances in Cooperative Transport by Mobile Robots

A gripping mechanism is presented for autonomous grasping/hoisting by two planetary rovers. Hardware and decentralized-control algorithms have been developed during continued research on the sensors, the actuators, and the design and functional requirements for systems of multiple mobile robots cooperating in the performance of tightly coupled tasks — for example, grasping and lifting long objects on challenging terrain. [Different aspects of the hardware and algorithms were described in “Advances in Cooperative Transport by Two Mobile Robots” (NPO-30376) NASA Tech Briefs, Vol. 26, No. 8 (August 2002), page 60. Although this research is oriented toward developing robotic capabilities for exploration of Mars, these capabilities could also be utilized on Earth.

Posted in: Machinery & Automation, Briefs, TSP

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