One of the longstanding challenges of space exploration is the huge amount of thrust it takes to escape the Earth's atmosphere. That kind of power is also expensive to create, so the holy grail of the last decade or so has become more efficient and inexpensive ways to move around space. SpaceX is working on reusable rockets, but another nascent concept involves "sailing" on the solar wind.
We first detailed the electric solar sail developed by Dr. Pekka Janhunen of the Finnish Meteorological Institute in 2008, and now it's back in a paper recently published in the journal Acta Astronautica. The report outlines how combining the sail with the mining of asteroids for water to convert to fuel could be the best way to conduct manned missions to Mars in the future.
You can consult our original article for more details on the workings of the sail, but the central concept involves using dozens of very long thin conducting filaments and an on-board electron gun to create a field that the solar wind then "pushes" against to propel the craft.
The basic pitch in the new paper is that because the so-called "e-Sail" is relatively lightweight compared to traditional propellant-based spacecraft, it's cheaper to get into space. Further, once in space, the e-Sail could be used to help mine asteroids for water that can then be converted to synthetic fuel for other types of spacecraft. Fueling stations orbiting around Mars and Earth could then be set up to enable more efficient manned trips between the two planets.
Having fuel in orbit around Mars could be especially helpful in better enabling more controlled and pinpointed landings on the Red Planet, as well as obviously putting a fuel source nearby for return trips to Earth.
As an added bonus, the mined water can also be used for radiation shielding for manned compartments, further reducing the overall mass that needs to escape Earth's clutch for such missions.
The catch is that the e-Sail can only ferry relatively small payloads, and the Earth's magnetic field blocks the solar wind, so while you still need rocket power to get an e-Sail into space, once it's there it could potentially become a sort of space ferry. It could then help get the infrastructure in place to eventually move cargo and people more efficiently between the two planets.
The e-Sail team estimates that once it is all set up, the costs to run the infrastructure between the orbits of Earth and Mars would be comparable to the expense of maintaining the International Space Station.
The e-Sail also has the potential to cover longer distances in shorter amounts of time. According to the team behind it, a Pluto fly-by could be possible in about five years, which is almost half the time it has taken NASA's New Horizons craft to reach the distant dwarf planet.
NASA is also testing its own solar sail, but seems to be sticking to rocket propulsion for its own Mars missions, so far.
Check out the video below for a simulation of how the solar sail will be deployed.
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