The X3 Ion Thruster Is Here, This Is How It’ll Get Us to Mars


Alec Gallimore: “What you’re seeing is this
energetic blue-greenish plasma that comes out of the thruster. It really looks like science fiction. In the end, we’re supplying electricity through
a wire and an inert gas and we turn it into this beautiful plasma that’s moving at tremendous
velocities that’s providing thrust that may one day send people to Mars.” Chemical rockets are the workhorses of the
space age, and they’ve had a pretty standard formula for the past 60 years. Get millions of pounds of liquid or solid
fuel into a rocket, light it on fire with an oxidizer, and then the speed of the propellant
shooting out the back gives the rocket enough thrust, or kick, to get into space. This works great for escaping Earth’s gravity. But if we want to get to Mars, chemical rockets
have hit their their performance limit. We need new propulsion systems that can rapidly
shoot a spacecraft across interplanetary distances, while using less propellant at the same time. That’s where the X3 comes in. As part of NASA’s NextStep program, the
X3 is an entirely new space engine that’s all electric. Alec Gallimore: “Electro-propulsion devices
have the equivalent of 10 times the propellant efficiency of a chemical system. To give you an example, a chemical rocket
tops out at around 40,000 mph. An electric system can go over 100,000 mph
and in fact, NASA is working on a project to design one that can actually achieve a
velocity of 500,000 mph. And at that speed you cover a distance between
the Earth and the Moon in about 30 minutes.” Here at the University of Michigan’s Plasmadynamics
and Electric Propulsion lab, engineers and students are working on the X3, a type of
electric propulsion design called a Hall thruster. Alec Gallimore: “Hall effect thrusters are
really a kind of a very ingenious propulsion system. We take a propellant, in some cases an inert
gas like xenon. We put a huge amount of energy into it, creates
a high temperature plasma, charged particles of electrons and ions, and then we can use
electromagnetic fields to shoot out the plasma at very high speeds. So they’re very simple in design, complex
though in operations and very, very efficient.” Hall thrusters aren’t just a thing of the
future. There are actually hundreds of satellites
above you right now using electric propulsion to stay in position. But this technology hasn’t been used for
manned missions yet, because the amount of thrust they’re capable of generating is
just too low, which means slower acceleration and a longer trip to Mars. So, we need more thrust. Ben Jorns: “Traditional Hall thrusters that
work in space operate between one and six kilowatts. Now the X-3 comes in and trying to scale Hall
effect thruster technology, into a new power operator machine. So going from six kilowatts to 100 or 200
kilowatts. And the advantage of that is if you go to
higher power, you can generate higher thrust. And therefore have higher acceleration. Instead of using one channel, which a traditional
hall thruster has three channels, so you take all those engineering requirements and you
multiply it by a factor of three.” For these engines to be used in space one
day, testing is critical, and these labs are uniquely equipped for the challenge. Alec Gallimore: “Sitting behind me is what’s
called ‘The Large Vacuum Test Facility’ the LVTF. It has one of the highest pumping speeds in
the world, which means it’s able to have a very low pressure while it’s operating a large
flow rate. And we use it to simulate space. We have 19 cryogenic pumps, that remove all
the air and all the gasses from the chamber so we can have a more realistic environment
to test these thrusters. Students run experimental campaigns in the
LVTF. One student might be trying to analyze the
life of a thruster. Another person might be trying to understand
how the electrons from the cathode make their way to the channel. A successful test is often when you find something
unexpected that ultimately leads you to having a better understanding of the device you’re
testing. And that happens quite a bit.” But the X3 is too powerful for even the LVTF,
and at this point, only NASA’s Glenn Research facility can handle its testing at full capacity. Alec Gallimore: “A typical thruster may
weigh 10 pounds, this thing weighs 500 pounds. So just designing and building all the components
of this mega-scale thruster was a challenge that we took on. Last year was a blockbuster year for the X3. It set records for Hall thrusters for the
highest power level at over 100 kilowatts of power. The highest level of thrust and actually the
highest amount of current being passed through any type of Hall current thruster.” These engineering achievements are key, because
electric propulsion is going to be a central part of our future in space. Alec Gallimore: “NASA is working on developing
a sort of a 20 year game plan. The idea is that we’ve been in the International
Space Station now for more than a decade and that has been a great. But the next step would be something like
a space station around the Moon. We would have an outpost around lunar orbit
to test new technologies that would be needed to have humans live in space. Hall thrusters are playing a really important
role in this…it’s baseline is to have a bank of four Hall effect thrusters around
because they want to be able to move around this space station and actually demonstrate
the ability to use electric propulsion of this kind with a human attended spacecraft.” The X3 is likely two incarnations away from
being flight ready, but the work happening here is all about demonstrating new principles
for how to design electro-propulsion engines. Ultimately, future space travel will use a
combination of chemical and electric propulsion to travel through space. And it’s projects like the X3 that make
a future mission to Mars even more possible. For more science documentaries, check out
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