people always ask me why we're stuck
with chemical rockets seriously
exploding a bunch of hydrogen or
kerosene is the best that we can do good
news there are other exotic science
fiction sounding propulsion systems out
there which use electromagnetic fields
to accelerate atoms allowing their
spacecraft to accelerate for months at a
time I'm talking about ion engines of
course and several spacecraft have
already used these exotic thrusters to
perform some of the most amazing
missions in the exploration of the solar
system I know I know
chemical rockets seem really primitive
take tons of liquid or solid fuel light
it on fire with an oxidizer and then use
the speed of the explosive gases to give
you a kick in the opposite direction
thanks Newton's third law the chemical
rockets do the trick those gases do give
a rocket the kick it needs to get into
space because they bring their own
oxidizer with them they work in the
atmosphere and they work in the airless
nough subspace the advantage of rockets
is that they can deliver enormous
amounts of energy in short periods of
time the kind of reaction you need to
blast tons of cargo off earth and into
space but they're incredibly inefficient
a 550 metric ton Falcon Heavy is
carrying almost 400 tons of fuel and
oxidiser the first stage will only burn
for 162 seconds and the second stage
will fire for 397 seconds that gives you
a total burn time of about nine point
five minutes want to make some maneuvers
want to accelerate for days weeks or
even months too bad
you are out of fuel of course these
shortcomings from chemical rockets have
led scientists to search for other forms
of propulsion especially when you're out
in space and one of the most successful
so far is the ion thruster
when you're working out the rocket
equation an important factor is the
velocity that you're rejecting your
propellant the most efficient chemical
rocket can throw hot gasses out the back
at five kilometers per second ion
engines on the other hand can eject
individual atoms ninety kilometers a
second this high velocity gives the
spacecraft a much more efficient
acceleration the best chemical rockets
see a fuel efficiency of about 35
percent while ion agency and efficiency
of 90% so how do I on thrusters work
actually pretty weird and totally sounds
like science fiction instead of hot
gases ion thrusters eject ions which are
atoms or molecules which have an
electrical charge because they've lost
or gained an electron in the case of an
ion engine they're emitting positively
charged ions which have lost an electron
once you've got ions you can direct them
with a magnetic field accelerating them
into space at tremendous speeds so where
do they get all the ions the thrusters
create them by generating a plasma
inside the spacecraft and they bombard
neutral propellant atoms of some gas
like xenon with electrons these
collisions release even more electrons
from the propellant turning them into
positively charged ions this plasma soup
of electrons and positively charged ions
has an overall neutral charge the
electrons are held in the chamber
leading to more ionizing events while
the positive ions are siphoned out
through a grid at the end of the chamber
as they pass through this grid high
voltage accelerates them out the back of
the spacecraft at speeds of up to 90
kilometers per second for each ionized
particle that the spacecraft can kick
out it gets a tiny kick in return
the whole system is powered by solar
panels so the spacecraft itself doesn't
need to carry any kind of battery or
power system minimizing the total weight
that it has to carry the big problem is
that the kick really is tiny the thrust
of ion engines is measured in millions
like thousands of a Newton hold a piece
of paper in your hand that's the kind of
forces involved but they can operate for
days weeks even months accelerating and
accelerating long after chemical Rockets
would have run out of fuel so if you're
already out of the gravity well of a
planet they're very efficient engines
for dramatic changes in velocity NASA
and other space agencies have actually
used ion engines very successfully in a
range of missions they've been
developing this thruster concept for
decades but we're never willing to risk
it on an active mission we're a failure
could end it
so NASA gathered up a bunch of these
risky technologies and package them
together as the Deep Space 1 mission
which launched in 1998 Deep Space 1 was
equipped with 12 different technologies
that NASA wanted to test out including
low power electronics solar concentrator
arrays various scientific instruments
and a solar electric propulsion system
its engine was run for enormous lengths
of time allowing you to make close
observations of asteroids and comets and
even Mars NASA doubled down on the
technology of Deep Space 1 giving its
dawn mission three redundant ion engines
these allow the spacecraft to go into
orbit around the asteroid Vesta make
observations then break orbit and travel
the asteroid Ceres and make even more
observations and it could still have
fuel in the tank to visit even more
asteroids just give a sense of its
acceleration dawn can go from 0 to 100
km/h in 4 days of continuous thrusting
ion thrusters were used to carry ISA
smart-1 spacecraft from Earth orbit to
lunar orbit and on the Japanese Hayabusa
spacecraft ion engines have been tested
here on earth and successfully operated
for more than five years continuously
with these successes we're gonna see
even more spacecraft equipped with ion
thrusters in the future but i untrust
rooms themselves are getting more
powerful and resourceful i said that ion
engines produce very little thrust but
there are some ideas to boost their
output the first is dramatically
increase the amount of electricity that
you're using to accelerate the ions
instead of solar panels NASA considered
creating an ion engine powered by a
nuclear reactor about 15 years ago NASA
considered a mission known as the
Jupiter icy moons orbiter mission
powered by the nuclear electric xenon
ion system or Nexus engine the
spacecraft will be capable of exploring
each of Jupiter's icy large moons in
sequence Ganymede Callisto and Europa
the spacecraft would have been launched
into orbit in three separate pieces
which would then be assembled in Earth
orbit and launched off to Jupiter the
spacecraft would use its eight ion
thrusters to study Callisto and then
Ganymede for three months each and then
settle into a final orbit around Europa
if conditions are right it could even go
into orbit around IO of course we don't
get to have nice things and the mission
was cancelled back in 2005 there are
other ways ion thrusters can be scaled
up NASA is testing a high thrust version
of ion engines known as the x3 Hall
thruster this engine is capable of
blasting out ions and produces 5.4
newtons of force again not much but
remember that previous thrusters top out
in the thousands of Newtons at the
highest levels this could be the
technology that will carry human
astronauts to Mars cutting down the
flight times to just a few months
engineers are planning to run the x3 for
100 hour tests this year to see if it
has the same kind of long-term operation
as the smaller ion engines the coolest
idea I've heard recently for ion engines
is the idea of an air-breathing engine
under development by the European Space
Agency instead of carrying any
propellant at all engineers at ESO
demonstrated that a spacecraft in
low-earth orbit should be able to pull
in molecules of a
right from the atmosphere and then
ionize them and blast them back out
since the spacecraft would be using
unlimited solar electricity for power
and pulling its propellant from the
atmosphere it could operate without
refueling potentially forever spacecraft
could operate at lower altitudes and
space stations could remain in low-earth
orbit indefinitely without needing to be
reboosted it's gonna be a real
game-changer and not only earth this
technology could be used on Mars or
Venus or Titan anywhere with an
atmosphere ion engines have already made
an impact on space exploration and in
the next few years we're gonna see more
missions equipped with them they can
even be the engines that carry human
astronauts from Earth to Mars in the
coming decades what do think about ion
engines lemon-aid your thoughts in the
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