A lot of time and effort goes into planning routes for space missions. Researchers look for the most efficient path between planets and moons because spaceflight is expensive. Even small gains in efficiency can save millions.
An international team of researchers say they've found a method of calculating a more efficient route between Earth and the moon using advanced computer modeling.
The cheaper route to the moon that the team found was actually hidden. Spacecraft that journey through our solar system only use fuel only part of the time. Gravity is often the preferred method of propulsion, because it's free. There are gravity-determined routes throughout our solar system, which are often referred to as the Interplanetary Transportation Network.
So finding a cheap route to the moon has a lot to do with gravity, specifically the gravitational pulls of both Earth and the moon. In spaceflight, "variate" refers to a natural trajectory leading to a certain orbit. The researchers found that, instead of using the branch of the lunar-orbit variate closest to Earth, it's better to enter that variate from the opposite side.
"Instead of assuming it's easier to choose the part of the variate closest to Earth, we can use systematic analysis with faster methods to try to find nontrivial solutions," study co-author Vitor Martins de Oliveira, a postdoctoral researcher at the University of São Paulo in Brazil, said in a statement.
Essentially, the team found that free gravity-based propulsion is more plentiful when taking the hidden path. This newly reported route uses 58.80 meters per second (m/s) less fuel consumption than the previous cheapest known route. Again, even this little efficiency gain would help reduce the cost of traveling to the moon.
Another benefit for the route the researchers found is that it won't cause interruptions in communication with Earth. "The Artemis 2 mission, for example, lost communication with Earth for a while because it was directly behind the moon," Oliveira said. "The orbit we propose is a solution that maintains uninterrupted communication."
But the newfound route is not the last word in cheap Earth-moon travel, the researchers noted. Their modeling work factored in gravity from just Earth and the moon; future research could include additional variables, like gravity from the sun, potentially leading to even more cost-effective trajectories..
"The systematic analysis we applied in our work is something that could be adopted more widely going forward," study lead author Allan Kardec de Almeida Júnior, a researcher at the University of Coimbra in Portugal, said in the same statement.
The study was published April 10 in the journal Astrodynamics.
