Space will soon have its very own gas station stacked with rocket fuel.
Scientists have now floated plans for fuel depots to be stationed at Lagrange — regions in space between the Earth, moon, and sun that maintain gravitational equilibrium.
Objects at these points remain in place, keeping the same relative position with respect to the Earth and the moon.
This way, future lunar missions may soon dock at a fuel depot, somewhere between the Earth and the moon and pick up extra rocket fuel before making its way to the lunar surface.
MIT engineers say orbiting way stations could reduce the fuel a spacecraft needs to carry from Earth — and with less fuel on board, a rocket could launch heavier payloads, such as large scientific experiments.
Scientists also floated the idea of stock piling.
Spacecraft heading to the moon would carry contingency propellant as they normally would, dropping the tank at a depot on the way back to Earth if it’s not needed.
Over time, the depot builds up a large fuel supply. This way, if a large lunar mission launches in the future, its rocket wouldn’t need a huge fuel supply to launch the heavier payload.
Instead, it can stop at the depot to collect the stockpiled propellant to fuel its landing on the moon.
Over the last few decades, scientists have proposed various designs, such as building a fuel-manufacturing station on the moon and sending tankers to refill floating depots. But most ideas have come with hefty price tags, requiring long-term investment.
The MIT team has come up with two cost-efficient depot designs that do not require such long-term commitment.
Both designs take advantage of the fact that each lunar mission carries a supply of contingency propellant — fuel that’s meant to be used only in emergencies.
In most cases, this backup fuel goes unused and is either left on the moon or burned up as the crew re-enters the Earth’s atmosphere.
The MIT team proposes using contingency propellant from past missions to fuel future spacecraft.
For instance, as a mission heads back to Earth, it may drop a tank of contingency propellant at a depot before heading home.
The next mission can pick up the fuel tank on its way to the moon as its own emergency supply. If it ends up not needing the extra propellant, it can also drop it at the depot for the next mission.
“Whatever rockets you use, you’d like to take full advantage of your lifting capacity,” says Jeffrey Hoffman, a professor of the practice in MIT’s department of aeronautics and astronautics.
“Most of what we launch from the Earth is propellant. So whatever you can save, there’s that much more payload you can take with you”.
The main drawbacks for both depot designs include maintenance; keeping depots within the Lagrange point and preventing a phenomenon, called boil-off, in which fuel that’s not kept at cold-enough temperatures can boil away.
If scientists can find ways around these challenges, Hoffman says, gas stations in space could be an efficient way to support large lunar explorations.
