An advanced, lightweight, low-power consumption brake has been developed to satisfy NASA's special requirements for use on actuators during spaceflight. This brake can increase the stopping, holding, and parking ability of a spacecraft while reducing its electrical power consumption. Two notable strengths of the design of this brake are modularity and fault tolerance. The use of brakes like this one can be expected to increase performance measures and safety margins in terrestrial as well as outer-space applications.
Brakes of this type are used in outer space or on Earth to stop, hold, or park a moving vehicle that is being driven by electromechanical devices. In spaceflight, brakes must be lightweight, exhibit short closing times, and conform to the geometries of pre-existing actuator structures. The principal issue in designing brakes for spacecraft is excessive power consumption, which is particularly costly
under circumstances in which resources are already at a premium and the loss of resources could cost time or jeopardize human lives. Although in some respects the situation is less critical on Earth, lives are nonetheless frequently lost when vehicle brakes fail. An advanced electromechanical braking system that satisfies the requirements for spacecraft and that increases the braking ability of Earth vehicles would surely prove beneficial to the government and to commerce.
When NASA assigned the task of designing an advanced braking system that could reduce the cost of spaceflight, it asked not only that the essential requirements pertaining to spaceflight (low power consumption and minimal thermal effects) be satisfied but that they be satisfied in a manner surpassing previous designs while reducing power consumption to 1/100 of a baseline level. Some of the benefits of the NASA design, relative to a design according to standard practice, are illustrated in the table. The modularity of design is another benefit: two or more modules can be included in a single braking system, so that if one brake fails the other brake(s) will continue to operate. Such redundancy creates a level of fault tolerance unequalled in previous space-deployed brake designs.
Brakes like this one could be used not only in outer space but also on Earth in applications in which multiple actuators operate at moderate to high temperatures, design goals include minimization of weight and power consumption, and there is a need for the insurance added by redundancy. Such brakes would be suitable for use with servo-actuators, especially in robots, wheeled exploratory vehicles, antenna-deployment mechanisms, and power tools.
This work was done by Delbert Tesar, Hau Nguyen-Phuc Pham, Derek Black, William F. Weldon, Richard Hooper, and Michael James Meaney of the University of Texas at Austin for Johnson Space Center.