Research sheds light on the use of multiple cubes for service and repair missions within the space

As more satellites, telescopes, and other spacecraft are built to be repairable, a reliable trajectory will be required for service spacecraft to reach safely. Researchers from the Department of Aerospace Engineering at Grainger University’s Faculty of Engineering at the University of Illinois at Urbana-Champaign are developing a methodology that allows multiple cubestats to function as service agents to assemble or repair space telescopes.

The method published in the Journal of the Astronautical Sciences states that it minimizes fuel consumption, ensures that service agents are closer to each other than 5 meters, and solves problems with non-space-related route guidance Can be used to do so.

“We have developed a scheme that will allow Cubesats to operate efficiently without collisions,” says Aerospace Ph.D. student Ruthvik Bommena. “Because these small spacecrafts have limited on-board computing capabilities, these trajectories are pre-calculated by mission design engineers.”

Bommena and his faculty advisor Robyn Woollands demonstrated the performance of the algorithm by simultaneously transporting two, three and four vehicle packs together, between the serviced vehicle and the space telescope receiving spatial service.

“These are difficult trajectories to calculate and calculate, but we came up with new techniques to ensure their optimality,” says Bommena.

Bommena said the most difficult aspect is the scale of distance. The James Webb Space Telescope’s orbit is approximately 1.5 million kilometers away, Lagrange Point 2 of the Earth of the Sun. That is where the gravity of the Sun and the Earth balance each other. It maintains orbit while apart from the sun.

“We use indirect optimization methods to ensure that the output solution is fuel-optimized without being too technical. The direct method does not guarantee that.”

“We also incorporated anti-collision path inequality constraints into optimal control formulations as stiff constraints, so spacecraft will not violate the constraints at any point in orbit.”

Bommena explained that traditional direct or indirect methods with constraints such as collision avoidance divide the trajectory into multiple arcs and increase complexity exponentially.

“Our methodology allows us to resolve the orbit as a single arc. We go directly from the starting point to the destination point. The fuel is optimal and the calculation is more efficient.”

Another major result from the study is the development of a circularly restricted three-body problem dynamic model related to novel targets.

“We needed to alleviate the numerical challenges that come from far away between the sun and the earth,” Bomena said. “To do that, we first shifted the center of the frame along the X-axis from the Sun Earth Vali Center to the position of Lagrange Point L2, and then derived the equation of motion compared to the target spacecraft. We also introduced new distances. The unit applies scaling factors that adjust proportionally in relation to the original distance measurements.”

Bommena said he and Woollands have been working on the project for about a year and a half. His breakthrough took place over long distance flights.

“Mathematics was working on paper. The big problem we had was fighting numbers. I was coding during a long flight. I tried a few things and suddenly converged. At first, I didn’t believe it. It was a very exciting moment and the next few days felt great.”

According to Bommena, the application for this work is to make services and assembly within a space safer and more efficient, but the methodology developed is very versatile and other trajectory optimizations with different constraints. It said it could be used in a scenario.