Thu. May 26th, 2022

Bringing a vessel to the right Mars orbit takes time, energy and money. Credit: Pixabay.

Putting a satellite into orbit around Mars has never been easy. To get the information and data they need to collect, the probes must achieve a specific orbit at low altitude. To achieve this orbit, satellites use a technique called Aerobraking, which brushes the spacecraft toward the top of a planetary atmosphere. To achieve maximum air resistance, the orbiter lowers the height of the vessel with a little help from its solar panels. However, this procedure takes fuel and a lot of time to complete, generally up to six months.

Now, however, engineers at the University of Illinois Urbana-Champaign are improving the process to save time, energy and money.

“The trip to Mars takes somewhere between six and nine months,” said Zach Putnam, a professor of aeronautical engineering at the university. “We can not really change that, but we think we can shorten the time it takes to aero brake to a low-altitude orbit. And the fuel on board that we save can be used to do other things like holding the spacecraft. alive longer. “

Engineers have created a real-time algorithm that rotates a satellite’s solar panels that can control how much air resistance is generated on the spacecraft. The algorithm includes control modes to limit the heat rate or heat load – or both – while trying to take advantage of energy reduction. The process can then be used to control the vessel during atmospheric passages to control heating and energy depletion. This process allows the satellite to fly much closer to operational constraints and aero brakes much faster.

“Being able to control the satellite during each atmospheric passage enables us to ensure that we do not overtemperature the solar panels while flying much closer to the thermal limit,” Putnam said. “This is a big improvement. Instead of aero braking for three to six months, it might only take a few weeks.”

Aero braking consists of three phases: Walk-In, Main Phase and Walk-Out.

During the Walk-In phase, engineers instruct the spacecraft to lower the periapsis (the nearest point on Mars in its orbit) one orbit at a time and move the spacecraft from its Mars orbit insertion height to its aero-braking height. This phase is used as a calibration period to understand atmospheric densities and the way the orbiter performs in and out of aero braking. This generally lasts about a week or five orbiting the red planet.

The main phase is the longest and can last about five and a half months. Once the satellite reaches its operational altitude (where the desired atmospheric densities were found), the main stage of aero braking begins. The orbiter is ordered to make large falls in its orbit. If the height became too low, the vessel would be in danger of overheating. If the altitude becomes too high, aero braking ends too late. Therefore, small propulsion maneuvers are occasionally performed to hold the satellite within a specified “corridor” by raising or lowering its periapical height.

The walk-out phase is the shortest phase in about five days. Here, the circulation increases its periapsis, which causes the circulation to shrink more calmly. When the apoapsis (the furthest away from Mars, the spacecraft reached in its orbit) is reduced to 280 miles (450 kilometers), the periapsis is raised out of the atmosphere and the aero braking is completed.

Putnam believes the new process will change the way future Mars orbits operate.

“This software would greatly reduce our reliance on ground stations,” he said. “If we could automate it on board and only have to check in with the spacecraft once a week, it would really reduce costs. And that could be done by many satellites at the same time.”

The study was published in the Journal of Guidance, Control and Dynamics.

Leave a Reply

Your email address will not be published.