A report discusses algorithms for realtime planning of translation paths of multiple spacecraft flying in formation. The algorithm takes account of requirements to avoid collisions while operating within resource constraints (e.g., not calling for an acceleration greater than maximum possible) and striving for optimality (e.g., completing a change of formation in minimum time or at minimum energy cost). The optimality/collision- avoidance problem is formulated as a parameter-optimization problem, in which the translation path of each spacecraft is parameterized by polynomial functions of time. It is shown that this parameterization is the key to the solution of the parameter-optimization problem in that it enables decoupling of the collision-avoidance and accelerationlimit constraints, thereby making it possible to solve the problem in two stages. In the first stage, one constructs feasible paths that satisfy only the collision-avoidance constraints subject to certain optimality criteria. It is shown that the acceleration- limit constraints can be imposed a posteriori to compute the required maneuver duration such that at least one acceleration component is saturated. This also enables construction of paths that require minimum time in the class of solutions being considered.
This work was done by Gurkirpal Singh and Fred Hadaegh of Caltech for NASA’s Jet Propulsion Laboratory. To obtain a copy of the report, “Collision Avoidance Guidance for Formation-Flying Applications,” access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Mechanics category.
This software is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393- 3425. Refer to NPO-30332.
This Brief includes a Technical Support Package (TSP).
Algorithms for Collision-Avoidant Formation Flying
(reference NPO-30332) is currently available for download from the TSP library.
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Overview
The document presents a technical support package from NASA detailing innovative algorithms for collision-avoidant formation flying of multiple spacecraft. Developed by Gurkirpal Singh and Fred Hadaegh at the California Institute of Technology for NASA's Jet Propulsion Laboratory, the report addresses the critical need for efficient and autonomous path planning in space missions that require spacecraft to operate in close proximity.
The primary focus of the research is on real-time planning of translation paths for spacecraft flying in formation, ensuring that they avoid collisions while adhering to resource constraints, such as maximum acceleration limits. The authors formulate the optimality and collision-avoidance problem as a parameter-optimization challenge, where the translation paths of each spacecraft are represented by polynomial functions of time. This parameterization is crucial as it allows for the decoupling of collision-avoidance constraints from acceleration-limit constraints, enabling a two-stage solution process.
In the first stage, feasible paths are constructed that satisfy only the collision-avoidance constraints while meeting specific optimality criteria. The second stage involves imposing acceleration-limit constraints a posteriori to determine the required maneuver duration, ensuring that at least one acceleration component is saturated. This method also facilitates the construction of paths that minimize the time required for formation changes.
The document highlights the novelty of the proposed algorithm, which integrates optimality, collision avoidance, and resource constraints—elements often overlooked in previous works. The iterative algorithm developed is scalable, making it suitable for large formations of spacecraft, which is essential for various space science missions, including variable baseline space interferometry.
The report also mentions the presentation of this technology at two significant forums in 2001 and indicates plans for a full-length paper submission to a referred journal. The software developed from this research is available for commercial licensing, with contact information provided for interested parties.
Overall, this document encapsulates a significant advancement in spacecraft formation flying, emphasizing the importance of collision avoidance as a mission-enabling technology for future space exploration endeavors.
