Future lunar missions may be fuelled in space depot
Imagine this. A spacecraft docks at a propellant depot - somewhere between the Earth and the Moon - and picks up extra rocket fuel before making its way to the lunar surface.
According to engineers at Massachusetts Institute of Technology (MIT), future lunar missions may be fuelled by gas stations in space.
Orbiting way stations could reduce the fuel a spacecraft needs to carry from the earth.
With less fuel on board, a rocket could launch heavier payloads such as large scientific experiments, the scientists said.
"Whatever rockets you use, you would 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 is that much more payload you can take with you," explained Jeffrey Hoffman, a professor at MIT's department of aeronautics and astronautics.
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 is 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-enter the earth's atmosphere.
Instead, the MIT team proposes using contingency propellant from past missions to fuel future spacecraft.
For instance, as a mission heads back to the 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 back at the depot for the next mission - an arrangement that the team refers to as a 'steady-state' approach.
A depot may also accumulate contingency propellant from multiple missions, part of an approach the researchers call "stockpiling".
According to Hoffman, transferring fuel between the depot and a spacecraft would simply involve astronauts or a robotic arm picking up a tank.
"In building the International Space Station (ISS), every time a new module is added, we have had to hook up new fluid connections. It is not a trivial design problem but it can be done," he noted.
(Posted on 07-03-2014)