Tech Briefs

Autonomous Guidance Algorithm to Auto-Pilot Spacecraft in the Vicinity of Primitive Celestial Bodies

Sequential convex programming is used. NASA’s Jet Propulsion Laboratory, Pasadena, California The dynamics in the vicinity of small bodies are highly nonlinear. Trajectory design in small-body environments requires accurate gravity and solar radiation pressure models to guarantee the satisfaction of spacecraft operational constraints such as thruster silent times, state, and control constraints. The G-PROX guidance algorithm generates fuel-optimal trajectories in the vicinity of asteroids and small bodies. The non-convexity in the control constraints is handled with the lossless convexification technique, which is a convex relaxation of the control constraints. G-PROX uses sequential convex programming and solves a convergent sequence of convex optimization problems generated via sequential linearization of both the dynamics and control bounds, synergistically combined with lossless convexification. The sequence of convex optimization problems converges to a locally optimal solution of the original nonlinear non-convex problem.

Posted in: Briefs, TSP, Robotics

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Safe Maritime Autonomous Path Planning in a High Sea State

Path planning for sea surface vehicles prevents capsizing and bow-diving in a high sea state. NASA’s Jet Propulsion Laboratory, Pasadena, California The goal of this work was to develop algorithms and software to generate a path that takes into account the direction of waves and wind as much as possible in order to mitigate potential damage to an autonomous underwater vehicle. A risk-based path planning algorithm to analyze real-world sensory data is combined with an enhanced sea surface model to generate a safe path.

Posted in: Briefs, TSP, Robotics

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Human Grasp Assist

A spinoff of the NASA/GM Robonaut 2 humanoid robot, this lightweight, motorized device can reduce or eliminate repetitive stresses to hands and arms. Lyndon B. Johnson Space Center, Houston, Texas Repetitive manual operations can degrade the work efficiency of a human operator over time, with the cumulative stresses of repetitive motion potentially affecting the resultant product quality and/or process efficiency. Accordingly, a lightweight, motorized device has been created that a user/operator may wear on a hand and forearm to augment the innate ability to flex his or her fingers, thumbs, and various connecting phalanges of a hand, thus optimizing the amount of grasping force applied to an object. The amount of augmenting tensile force provided by the motorized device may be controlled by the user via force-based contact sensors positioned at a distal end of each finger. As the operator exerts a grasping force on an object, a microcontroller, which may be embedded within (or connected to) a flexible band or strap portion of the device, automatically executes an algorithm to thereby calculate and/or select an optimal amount of augmenting tensile force required for executing the grasping action.

Posted in: Briefs, Robotics

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Scientific Balloons as Solar Sails

Goddard Space Flight Center, Greenbelt, Maryland Existing scientific research balloons such as those launched from Wallops Flight Facility could be placed in near- Earth space where they would perform as solar sails, providing relatively inexpensive propulsion systems for interplanetary missions. The balloons would accelerate at rates comparable with the ion drive performance of the NASA Dawn spacecraft, so they would enable unprecedented low-cost access to interplanetary space.

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Non-Thermal, Plasma-Assisted Catalytic Reactor for CO2 Methanation

Marshall Space Flight Center, Alabama Converting in-situ resources such as CO2, which is the main component of the Mars atmosphere, into methane for rocket propellants can significantly reduce the cost and risk of human exploration while at the same time enabling new mission concepts and long-term exploration sustainability. Methanation of CO2, also called a Sabatier reaction, is hence a key enabling technology required for sustainable and affordable human exploration of Mars.

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Sea-Level Flight Demonstration Altitude Characterization of a LO2/LCH4-Based Ascent Propulsion Lander

Lyndon B. Johnson Space Center, Houston, Texas A recently developed 1,500-lbf (6,672-N) thrust-class liquid oxygen/liquid methane (LO2/LCH4) rocket engine was tested at both sea level and simulated altitude conditions. Sea-level tests were conducted using both a static horizontal test bed, and a vertical takeoff and landing (VTOL) test bed capable of liftoff and hover-flight in low atmospheric conditions. The vertical test bed configuration is capable of throttling the engine valves to enable liftoff and hover-flight.

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Improved Hall Thrusters Fed by Solid Phase Propellant

Mg is more abundant than Xe and provides a much higher specific impulse. John H. Glenn Research Center, Cleveland, Ohio Hall thrusters normally use Xe propellant, which is expensive and scarce in the solar system. The weight of Xe is such that typical Hall thrusters are limited in specific impulse to approximately 3,000 s. The objective of this program was to improve and demonstrate Mg Hall thruster systems. Mg is abundant in the solar system and has an atomic mass approximately one-fifth that of Xe, which means much higher specific impulse is achieved than with Xe at typical thruster operating conditions (power, voltage).

Posted in: Briefs, TSP

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