Since the inception of man’s interplanetary ambitions, spacecraft trajectory planning – the determination of the specific path a spacecraft should take to arrive at a desired celestial object – has been an essential challenge. Often, there is no obvious perfect solution for a deep-space mission, leading to the development of a diverse array of software tools and mathematical processes that seek to determine the “most feasible” course.
The Global Trajectory Optimization Competition (GTOC) is an annual opportunity for teams from across the world to creatively develop and implement solutions to a variety of spacecraft trajectory planning problems. For the first time, a team of student researchers from the U-M Aerospace Engineering Department participated, placing 16th in the European Space Agency’s 9th Global Trajectory Optimization Competition. The online competition attracted 69 teams.
In the past, GTOC challenges have included trajectory planning to map four Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto) using repeated multiple fly-bys and guiding probes to gather science in the asteroid belt. This year, the challenge focused on addressing the issue of “space junk,” accumulation of inactive satellites and other debris in orbits around Earth that can pose hazards to new missions. Dr. Taheri, lead researcher of the U-M team, explains:
“This problem [of space debris] is very important. There are a lot of inactive satellites in low-Earth Orbit, and companies such as SpaceX and OneWeb have very ambitious projects to put up more in the vicinity of Earth. We need a spacecraft that can deorbit these satellites and this year’s GTOC challenge was a great opportunity to utilize our tools to verify the possibility of removing debris in a hypothetical situation.”
The competition challenge was: “It is the year 2060 and the commercial exploitation of Low Earth Orbits (LEOs) went well beyond the trillion of Euros market size. Following the unprecedented explosion of a Sun-synchronous satellite, the Kessler effect triggered further impacts, and the Sun-synchronous LEO environment was severely compromised.
Over the course of the month-long challenge, teams submitted a series of missions aimed at removing 123 orbiting pieces of debris distributed among sun-synchronous orbits. Multiple missions have to be designed that cumulatively remove all the debris pieces to restore the orbital environment functionalities. Proposed missions were ranked according to mission cost, calculated from proposed spacecraft mass and a base cost that increased over time.
"The competition stimulates development of new methods for which there are currently no solutions"Dr. Ehsan Taheri
“This competition requires a complete dedication of time. Most of the time, team members had to stay overnight, working on clusters and submitting solutions. [Though intense], I see this competition as having many benefits for our students. It creates motivation and enables students to get involved with real practical problems. It generates many ideas that will result in publications and novelties, stimulating development of new methods for which there are currently no solutions.”
After U-M’s strong performance this year, Taheri sees an opportunity for further integration of space trajectory optimization into the U-M Aero curriculum:
“Our top 20 ranking is something to be extremely proud of, especially considering [the caliber] of the competition. Scientists from all main space agencies, private space companies and Universities actively participate in this competition. This challenge was an effective demonstration of a chance for the department to invest more in the fields of astrodynamics and trajectory optimization, providing valuable options for students interested in space sciences. My hope is that we can see new classes or curriculum emerge that focuses on these topics in the near-future.”
The U-M team under Dr. Taheri was composed of one undergraduate and two Master’s students, working in collaboration with researchers from Michigan Tech.