14 DAY TRIAL // In a paper published in the latest issue of the journal Acta Astronautica, engineers at the Massachusetts Institute of Technology (MIT) in Cambridge detail their new concept of propellant depots in space. The team believes that such a setup could enable space agencies to explore targets such as the Moon and beyond with increased efficiency.
The new study was led by Jeffrey Hoffman, a professor with the Department of Aeronautics and Astronautics at MIT, and his team of graduate students, including Koki Ho, Katherine Gerhard, Austin Nicholas, and Alexander Buck. There are significant benefits to having access to space gas stations, the group argues in their paper.
The way this would work is quite simple – a spacecraft would depart Earth, dock to a gas station somewhere between our planet and the Moon, and then continue on its way with a fuel tank of propellant. This would entail the tremendous benefit of launching probes, landers, or rovers with less fuel, and therefore more science equipment.
Experts say that this is not the first such proposal. For decades now, scientists have been proposing various designs for refueling spacecraft mid-flight, including a scenario where a refinery is built on the Moon for fuel production. Ferries would then deliver fuel to other floating depots. However, most of these ideas have been plagued by the need for long-term, heavy financial investments.
This drawback has been addressed in the new paper, which contains details of not one, but two different, cost-efficient depot designs that can be assembled without a huge price tag. Both approaches are centered around the contingency propellant all Moon-bound spacecraft carry for emergencies.
Usually, this fuel is destroyed by venting it over the lunar surface or, in the case of manned missions, is burned up as the spacecraft reenters Earth's atmosphere. What the group proposes is that this fuel be used to propel future missions, by stockpiling it in dedicated caches.
“Whatever rockets you use, you’d like to take full advantage of your lifting capacity. 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,” Hoffman explains.
The depots would be accessible to lunar spacecraft on their way back to Earth. During a short pit stop, the vehicles could transfer any extra fuel to these structures and then continue onwards with the minimum amounts necessary.
The drawbacks associated with both designs have largely to do with maintenance costs and with the intricate mechanisms that would have to be developed in order for spacecraft to seamlessly and safely connect to the depots. However, the group is confident that these issues are easier to deal with than funding shortages.