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| Solar Electric Propulsion |
The chemical rockets used on most spacecraft today
produce thrust by burning fuel and oxidiser in a
chemical reaction and expelling the exhaust gasses
backwards. This produces very high thrust but uses
a lot of fuel and some of the thrust is burned simply
to accelerate the mass of the fuel. Solar Electric
Propulsion, also known as an ion drive, achieves
much more-efficient thrust by doing away with the
chemical reaction. Instead, the Xenon gas propellant
is positively charged by bombarding it with electrons
in a magnetic chamber and then accelerated with
a negatively charged grid. As the atoms leave
the exhaust nozzle, they’re travelling at 144,840
kilometres (90,000 miles) per hour. Although the
thrust from SEP can only lift a sheet of paper, it’s ten
times more-efficient than chemical rockets.
Solar sails offer even better efficiency by doing
away with propellant altogether, with the reflective
material harnessing the momentum of light itself.
As the Sun’s rays bounce off the sail, the deflected
photons impart a tiny but constant force. Over
several months or years the gentle thrust from these
ultra-efficient propulsion methods can accelerate a
spacecraft to interplanetary – or interstellar – speeds.
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