Virginia Tech researcher explores collision avoidance with space debris
The NASA-funded project proposes nontraditional strategies to prevent predicted collisions without adding to the accumulation of space junk.
For more than six decades, humans have been successfully exploring our universe – while also leaving a massive amount of space debris in our wake.
The graveyard of human objects accumulating in low-Earth orbit includes paint flecks from rockets, remnants of spacecraft, and defunct satellites. Objects larger than 10 centimeters are tracked by the U.S. Space Surveillance Network, and to date, more than 25,000 items of this size range are currently circling our planet at high speeds.
With every new spacecraft or satellite launched, we continue to add to the space junk problem. This growing debris field poses safety risks, increasing the potential for collisions and subsequent damage to current and future spacecraft and systems.
While there has been extensive research dedicated to the physical capture and removal of space debris, NASA is seeking nontraditional strategies focused on preventing a predicted collision without complete removal of the debris objects involved.
Riley Fitzgerald, assistant professor in the Kevin T. Crofton Department of Aerospace and Ocean Engineering, is exploring a novel approach to this just-in-time collision avoidance strategy. His research is focused on utilizing targeted dust cloud deployments - or a plume of fine material - from orbital platforms to avert predicted collisions.
Fitzgerald, recently appointed the Ryan and Krista Frederic Junior Faculty Fellow, is an expert in orbital mechanics and spacecraft navigation. His theoretical and computational research has been funded for $600,000 over three years through an Early Faculty Career award from NASA’s Space Technology Research Grants Program.
“The goal of any remediation plan is to reduce long-term risk to spacecraft and humans operating in orbit, specifically the risk of debris collision,” said Fitzgerald. “Removal of existing debris requires significant cost and effort. An alternative approach is to use targeted dust clouds to slightly alter the orbital path when there is notice of a potential collision.”
Collision avoidance
Simply explained, when a collision or close approach between two objects is predicted – often 12 to 48 hours in advance – an orbiting deployer would release a cloud of fine-grained tungsten dust onto a trajectory that intercepts the object's path. The resulting impact of the dust on the debris would act like a temporary increase in drag, effectively nudging the object and slightly adjusting its orbit to prevent the collision.
Given the high velocities involved, the fine-grain dust has enough effect to alter the orbital path, but the dust is light enough to quickly fall back to Earth without adding to the field of space debris.
Not only does this approach offer quicker response times in collision prevention, it also allows for adaptive tuning of the deployed dust clouds to the specific debris target. Fitzgerald and his team are using computational modeling to assess a variety of cloud geometries for specific debris or collision scenarios.
Over the course of the three year effort, the team will be analyzing dust deployment, dust dispersion patterns, and remediation effectiveness as well considering how the number, distribution, and size of on-orbit deployers affects remediation response time, coverage, and fuel costs over all phases of a system’s lifetime.
This flexible cloud geometry is scalable and able to provide effective and highly-responsive just-in-time collision avoidance (JCA) for a broad variety of debris objects and orbital paths. Increasing the number of deployer spacecraft would positively impact the coverage, response time, and system efficiency in the hopes that one will be in the right place at the right time for a rapid, efficient response.
“The biggest hope for an outcome — from my perspective and from NASA's — is a better understanding of the feasibility, scaling, effectiveness, and cost of this method relative to other proposed methods, for JCA and remediation in general,” said Fitzgerald.
“A concrete end goal is a series of recommended designs, and data showing how we could trade off the cost and percentage of collisions prevented. We'd also want to consider how well this compares to alternative methods so that NASA can make decisions about which debris remediation technologies, or combinations thereof, to develop further in the future.”
