Mechanical & Fluid Systems

Release of a Stuck Solar Array or Antenna

Several options are examined that may also be useful in remotely controlled terrestrial environments.

Goddard Space Flight Center, Greenbelt, Maryland

Satellite launches experience approximately one deployment failure every two years. These failures include a solar array or antenna that fails to deploy because it is stuck due to a mechanism failure, or is snagged by a cable or thermal blanket. Knowledge of the exact circumstances of the deployable failure is limited. Ground commanding of the spacecraft is conducted in an attempt to free the stuck deployable.

Posted in: Briefs, Mechanical Components, Automation, Failure analysis, Antennas, Antennas, Robotics, Satellites
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High-Heat-Flux-Capable Boundary Layer Vortex Generator and Boundary Layer Transition Device

Lyndon B. Johnson Space Center, Houston, Texas

Afixed geometry device has been developed to promote boundary layer transition and generation of streamwise vorticity, and is capable of withstanding entry heating environments for the Space Shuttle Orbiter. Designed to have a total height above the surface of the same order as the local boundary layer thickness, this device is approximately 0.25 in. (≈0.6 cm) tall and 4 in. (≈10 cm) long for the Orbiter entry application. Because temperature exposure is a key design factor for entry systems, the geometry has been optimized to establish peak heating rates and peak surface temperatures that are close to being spatially consistent on the protuberance. A relatively thin cross-section of 0.4 in. (≈1 cm) provides significant thermal radiation relief via conduction through the aft surface of the geometry. Sufficient mechanical strength to satisfy launch, ascent, entry, and landing conditions has been maintained in the design.

Posted in: Briefs, Mechanical Components, Automation, Thermal management, Thermal management, Aerodynamics, Entry, descent, and landing
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GEMINI Stability Control for Reducing Pointing Jitter in CubeSats and Smallsats

Pointing jitter is significantly reduced by using two reaction wheels per axis, passive vibration isolators, and differential speed control.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Because of the cost-effectiveness of flying smallsats compared to large flagship spacecraft, there is increasing interest in boosting their capabilities for supporting precision science payloads and sophisticated instrumentation. Unfortunately, a major current drawback with using smallsats is their inability to hold the pointing line-of-sight steady without jittering. Line-of-sight jitter degrades observations made by cameras and other imaging-type instruments, and fundamentally limits the quality of science that can be obtained.

Posted in: Briefs, Mechanical Components, Automation, Stability control, Imaging, Imaging and visualization, Imaging, Imaging and visualization, Vibration, Vibration, Test equipment and instrumentation, Satellites
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Piezoelectric-Actuated Rotary Ultrasonic Motor

This motor can be used where rotary actuation is required, particularly in cryogenic and high-temperature applications.

NASA’s Jet Propulsion Laboratory, Pasadena, California

This actuator was developed out of a need for a cryogenic actuator that can operate effectively in spite of the thermal mismatch involved with construction materials that have different expansion coefficients. Also, there is a need for a cryogenic motor that can drive infrared systems and produce minimal thermal energy that can interfere with their operation.

Posted in: Briefs, Mechanical Components, Mechanics, Automation, Sensors and actuators, Sensors and actuators, Thermal management, Thermal management, Materials properties
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How to Prevent Step Losses with Stepper Motors

While stepper motors are an excellent solution for many applications, a key concern is step losses. However, in most instances step losses can be prevented or corrected. It is important to remember that a stepper motor does not operate like a DC motor. This white paper from MICROMO engineers provides guidance to determine step losses or non-operation across a variety of applications.

Posted in: White Papers, White Papers, Mechanical Components, Mechanics, Medical, Motion Control, Motors & Drives
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Launch Tie-Down and Release Mechanism for CubeSat Spacecraft

This hardware configuration takes up an extremely small volume inside the CubeSat bus.

NASA’s Jet Propulsion Laboratory, Pasadena, California

As CubeSats take on increased functionality, including larger solar arrays for increased power demands and large antennas for science and communications needs, the requirements for launch tie-down and release mechanisms are evolving. In the past, some large CubeSat-deployable structures (solar arrays) relied on the confining walls of the CubeSat canister to act as the restraint mechanism. However, this practice is largely eliminated now, with most CubeSat specifications requiring a minimum amount of dwell time (after the CubeSat has been ejected from its parent canister) before the deployable structure can be released and deployed on orbit. Thus, a reliable restraint and release mechanism that does not depend on the geometry of the canister walls must be implemented.

Posted in: Briefs, Mechanical Components, Antennas, Antennas, Packaging, Launch vehicles, Satellites
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Ratcheting Threaded Tapered Collet for use in Planetary Sample Caching Systems

The desired sample tube preload can be tailored to specific applications, and allows each sample to be individually secured.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Aridged retention interface is necessary to secure planetary sample tubes within a caching system for use in future sample return missions. The assumed retention interface requirements are as follows: the interface shall maintain sample integrity at large deceleration landing loads; the interface shall minimize weight and complexity; and any required actuation for sample tube retention shall be performed by an external source (such as a robotic end-effector).

Posted in: Briefs, Mechanical Components, Containers, Mountings, Entry, descent, and landing
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Planetary Ice Mining by Down-Hole Energy Injection

This lightweight technology operates in low gravity with energy efficiency.

John F. Kennedy Space Center, Florida

Ice has been discovered on Mars and is present in the permanently shadowed craters on the Moon and on many asteroids. The ice is usually buried beneath an overburden of regolith. Evidence indicates this overburden may be a meter deep in some locations for the Moon; for Mars, it varies with latitude and may be as deep as or deeper than two meters in many locations. To obtain this ice as a resource in usable quantities, existing technology will require that it be strip-mined.

Posted in: Briefs, Mechanical Components, Water, Mining vehicles and equipment, Spacecraft
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The Ultimate Shaft-To-Hub Connection

Polygon Shapes - Multi-Faceted Problem Solvers

Kinematically ground polygonal shapes have been used as drive connections for more than 45 years. What is now referred to as Polygon Systems was developed by Fortunawerke, Stuttgart, West Germany, who patented a grinding machine capable of producing matched polygonal shaft and bore diameters.

Posted in: White Papers, White Papers, Mechanical Components, Mechanics
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Integrated Epoxy Feedthroughs Improve Fuel Pump Reliability

Of all the design decisions that affect the operation of an in-tank fuel pump, the way you seal the pump housing may top the list. A bad seal will allow liquid fuel to work its way into the housing, which will eventually corrode the electronics and potentially cause a risk of fire.

Posted in: White Papers, Aeronautics, Defense, Mechanical Components, Mechanics
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