Lt. Col. Robert Bettinger, assistant professor of astronautical engineering, Air Force Institute of Technology, was recently awarded a patent for his invention, “Early Warning Reentry System Comprising High Efficiency Module for Determining Spacecraft Reentry Time.” His module uses three simplified inputs: spacecraft physical shape, spacecraft aerodynamics, and atmospheric density. Shown in the diagram is an example output of the linear model developed by Bettinger. Individual re-entry time predictions (blue dots) converge to a line as the actual re-entry date approaches, and this line gives the overall prediction estimate (AF Contributed Image).

By Jaclyn Knapp, AFIT CSRA

WRIGHT-PATTERSON AIR FORCE BASE, Ohio – Lt. Col. Robert Bettinger, assistant professor of astronautical engineering and deputy of the Center for Space Research and Assurance, Air Force Institute of Technology, was recently awarded a patent for his invention, “Early Warning Reentry System Comprising High Efficiency Module for Determining Spacecraft Reentry Time.” The system utilizes simplified representations of both the satellite and atmosphere to predict the re-entry time of uncontrolled spacecraft with improved prediction accuracy.

“Using coarse approximation, the linear model enables increased confidence in re-entry time prediction nearly a week prior to the event without the need for exact spacecraft aerodynamics or knowledge of the solar cycle,” said Bettinger.

Space professionals estimate there are more than three thousand active spacecraft of various sizes orbiting the Earth. The disposal of spacecraft from low Earth orbit in the atmosphere is important to reduce the growing population and associated risks of space debris. Not all satellite re-entries are controlled, however, and the re-entry of uncontrolled space vehicles poses a risk to both people and property.

Recent uncontrolled atmospheric re-entries of low Earth orbiting spacecraft have highlighted the necessity of accurate re-entry time and location predictions. The problem and potential hazard of re-entering “space junk” has become a global news story, such as the re-entry of the Tiangong-1 space station in April 2018 and the Long March 5 Upper Stage in mid-2021.

Unfortunately, re-entry time predictions are highly uncertain due to the very nature of the re-entry environment: the atmosphere. In recent decades, the inclusion of increasingly precise models for spacecraft aerodynamics and atmospheric density into re-entry prediction algorithms has improved overall prediction accuracy, but at a cost of computational complexity.

“AFIT faculty, staff, and students are conducting cutting-edge research with a direct application to the immediate technical problems facing our country. Patents are one means to recognize our technical innovations, and are a laudable achievement for both the inventor and the AFIT family,” said Dr. Walter Jones, AFIT director and chancellor.

In the future, the Center plans to utilize the patent for expanding AFIT’s re-entry analysis program and to spur the development of enhanced models to predict the re-entry time of spacecraft in highly-elliptical orbits, such as a launch vehicle in a Geosynchronous Transfer Orbit.

The Air Force Institute of Technology, or AFIT, located at Wright-Patterson AFB, Ohio, is the Air and Space Force’s graduate school of engineering and strives to be the student’s first choice for advanced academic education and technical professional continuing education.