How Do Ion Engines Work? The Most Efficient Propulsion System Out There

How Do Ion Engines Work? The Most Efficient Propulsion System Out There

People always ask me why we’re stuck with
chemical rockets. Seriously, exploding a bunch of hydrogen or
kerosene is the best 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 tonnes 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. But 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 airlessness of space. 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 tonnes of cargo off Earth and into space. But they’re incredibly inefficient. A 550 metric tonne Falcon Heavy is carrying
almost 400 tonnes of fuel and oxidizer. 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
9.5 minutes. Want to make more maneuvers? Want to accelerate for days, weeks or even
months? Too bad, you’re 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 the 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 ejecting your propellant. The most efficient chemical rocket can throw
hot gases out the back at 5 km/s. Ion engines, on the other hand, can eject
individual atoms 90 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%, while ion engines see an efficiency of 90%. So how do ion thrusters work? It’s actually pretty weird, and totally
sounds like science fiction. Instead of hot gases, ion thrusters eject
ions. These 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. 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 of the back of the spacecraft at speeds of up to 90 km/s. 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 it has to carry. The big problem is that that kick really is
tiny. The thrust of ion engines is measured in millinewtons,
like, thousandths 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 had been developing this thruster concept
for decades but were never willing to risk it on an active mission where a failure could
end it. So NASA gathered up a bunch of risky technologies,
and packages 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 it 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 allowed the spacecraft to go into orbit
around the asteroid Vesta, make observations, then break orbit and travel to asteroid Ceres
and make even more observations. And it could still have fuel in the tank to
visit even more asteroids. Just to 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 ESA’s 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 5 years continuously. With these successes, we’re going to see
even more spacecraft equipped with ion thrusters in the future, but ion thrusters 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 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 NEXIS) engine, the spacecraft would 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 8 ion thrusters
to study Callisto and then Ganymede for three months each, and then settle into a final
orbit around Europa. If conditions were 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 thousandths of newtons. At the highest power 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 ESA demonstrated that a spacecraft in low Earth orbit should be able to pull
in molecules of air 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 for long periods. Spacecraft could operated at lower altitudes,
and space stations could remain in low Earth orbit indefinitely without needing to be reboosted. This is going to be 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 going to see more missions equipped
with them. They could even be the engines that carry
human astronauts from Earth to Mars in the coming decades. What do you think about ion engines? Let me know your thoughts in the comments. Once a week I gather up all my space news
into a single email newsletter and send it out. It’s got pictures, brief highlights about
the story, and links so you can find out more. Go to to sign
up. And finally, here’s a playlist.


100 thoughts on “How Do Ion Engines Work? The Most Efficient Propulsion System Out There”

  • Hi Fraser. I'd like you to do a video on the idea of deep-space exploration using a nuclear energy sourced ion engine. What you've done here is great but it would be bringing it to the next level if you could do a thought mission (or 2, or 3…) to some place like Sedna for example…AND do it with some numbers. For example, starting with some useful satellite mass orbiting Sedna, then moving to the question of how long a nuclear fuelled ion engine would take to get from Earth to the dwarf planet. What size of a chemical rocket would be necessary to lift that payload from the surface of the Earth, accelerate, and then decelerate so as to be able to go into orbit. Now THAT would be an interesting video! It took many years to get to Pluto and Ultima Thule; how quickly could such a journey be done using a nuclear powered ion engine?

  • Fusion could it be like atom smasher were radiation atoms colide in away with hydrogen who knows anybody know respone

  • Looks like Ion Thruster will beat Plasma Thruster, because I cannot imagine being carry on by an ultra ultra high temperature source just few meters from me….

  • carol Kampstra says:

    it wont get you off the ground let alone in to space . not enough thrust .still going to need that fuel burning rocket .

  • To have Humans travelling to Exo-planets without them going crazy on the way. It would probably have to take less than a few months. Or have them all in cryo-sleep the whole time.

  • Here is the most powerful and efficient ion thruster ever made, even though it is just a rough prototype. It can lift its power supply directly from the ground. It could alternatively carry a small propellant tank or use commercially available solar cells. Please click the purple icon to see video and facts.

  • We need faster forms of travel so we can make it to other stars. Ion engines aren't even in the that league. It would take an ion engine even longer than solid propellent driven space craft.
    We need ultra fast travel. It will come in about another 800 years. We're just too low on the evolutionary ladder. When we stop killing each other is when we'll be capable of true learning.

  • EnglishTeacherBerlin says:

    Great video!
    Also see this German guy, who built his own ion thruster that propels air out its end.

  • If you would like to see an ion thruster that can lift its power supply from the ground, Please click of the purple channel icon to the left. it can accelerate at much more than 1G continuously,… as well as carry a small propellant tank if needed.

  • With no atmosphere no drag, Wouldn’t need propulsion once set in motion. So there is something that smells rotten here. The thrust would only have to be till craft is up to speed. Then you’ll need reverse or side thrust to stop or change direction.

  • Compressed air or gas could be used for fuel in space. So they need to figure out a way to vacuum in air as the solid fuel leaves the tanks.

  • Doubleheaded Eagle says:

    I first heard about ion engine’s when I read a Star Wars how does work book as a child. Apparently the Millinum Falcon has an ion engine.

  • 3xtr4_0rd1n4ry says:

    i have an idea!

    Create a Fission or Nuclear Fission Generator then maybe we could implement that as a power source (i.e. all the extra energy (heat) used as the power source)

  • Could you get more thrust by accelerating heavy atoms (lead; uranium)? Excuse my lack of scientific knowledge.

  • I don't really get all the "hate" in some of the comments here… First off, consider us fortunate if we regularly, reliably and affordably get to the moon and NASA's Gateway project, then Mars. That'd be an incredible leap of progress.

    Second, you don't need to instantly accelerate to 99% of the speed of light for a propulsion technology to be useful in the vacuum of space – There are many dimensions of space travel that have just as much value as the initial acceleration.

    Third, we've got a much more serious issue if we want to venture to our outer solar system to consider – namely keeping humans alive that long and sane to boot (preferably having the option to return from their voyage as well safe and sound…), PLUS we still aren't sure exactly what effect only one year has had on our human physiology while in space. We're learning but… our sample size is as small as it could get lol.

    Fourth… Ok sure, I also want revolutionary engines but those aren't within our reach in the foreseeable future. Trust me, I'd love to create and harness a black hole and intermittently feed it to power our propulsion. Of course. It ain't happening in ANY type of useful time frame though.

    Fifth, the Ion puns guys… We all need to stop being so negative about this topic… 😀

    I really enjoyed the video and you taking the time to answer comments below Fraser! Consider me subbed!

  • The power electronics which create the ions, the magnetic fields to guide the ions, and the electric field to accelerate the ions is a pretty trick achievement.

  • Thank you for ending on a hopeful note. There are too many stories of "We had this amazing idea for a solar system mission… but the project was scrapped."
    The current generation of ion engines use krypton, right? At what rate do they consume fuel? Weeks of constant thrust means weeks of depleting its source of ionizable atoms.

  • Amachetay Cybo says:

    Don't forget warp drive and wormholes cuz we actually already have both just not really a public thing yet

  • Ion engines are tremendesly inefficient while inside any kind of atmosphere due to the resistance of atmospheric drag.

    However, once you get into space where there is no atmosphere (or very low atmospheric resistance) it is incredible efficient.

    But don't think of having a drag race in outer space though.

    Ion engines have a very low acceleration rate. But still acceleration. Over time that is. While still using the same amount of output thrust. And that is why they're so efficient.

  • How big are these ion engines? Can they fit in a shuttle fully assembled?
    It would be cool to see an array of them in space.

  • This makes the idea of chemical rockets seem even more exoticly magnificent Chemical rockets started during the second world war the nazi's von BraunI am disgusted that nobody else from the free world since that time has managed to think of anything better than that since then so where did the rocket idea come from in the first place Aliens?

  • Question (unrelated to this video): Whatever happened to that Hubble class telescope that the US Military just gave to NASA that you reported on (ages ago now I think)?

  • If you click on my channel icon to the left, you can see many prototypes of my ion thrusters lift their onboard power supplies against earths gravity. This is the first and only heavier than air ion propelled aircraft that can lift its power supply without external assistance. Under the videos there is a link to the website also.

    There was some news claiming MIT made an ionic glider that was the first to carry its power supply but, if you look into it fully you will see that in this rare instance, they were not first.
    The patented ion thruster on my site could carry a small propellant tank, so it should work in a vacuum, though it still needs to be tested for that. Imagine accelerating for long periods of time at greater than 1G. Even at a small fraction of that it would open up exciting possibilities!

  • Mattheu DePrano says:

    Thought provoking, I'd like to see a way for them to recharge their tanks with a compressor of some sort while in an atmosphere of a planet and be able to boost back off into space and use that atmosphere until the next planet.

  • Balasaravanan Palanirajh says:

    Can an ion engine ionise any element or only gases?
    If the ion thrusters can utilise carbon, minerals and other solid and liquid elements too, we can harvest a meteorite or asteroid on the way…

  • Some of the ionic remarks are very amusing . But the serious side ,  is reaching for the STARS a stretch too far. If a space craft could attain a million m.p.h it would still take a hundred plus years to reach the nearest star outside of our solar system. Imagine Astra 1 sends out an SOS, we have a computer malfunction, Six months later Huston replies, try rebooting it . A year later another communique . we tried that first but it dodn.t work. Not a lot like Star Trek.

  • @fraser I havent looked at the numbers, but do you think it would be possible to use this to have small ion engine drones that transport small packages on the moon? The gravity is much lower on the moon and one need as much power. I imagine for exploring the moon or even transporting light weight materials. As there is no real atmosphere stadard drones or small helicopters would not work. And if it only needs electricity they could work for decades i guess?

  • "Ion engines produce very little thrust, so in order to reach speeds of 100km/s they must accelerate continuously for months or years."

  • I know I mentioned it before however, but if anyone likes, they can click on my channel to the left, to see an ion thruster that can lift its power supply from the earth! It still needs to be proven that it can get better than 1 to 1 thrust using an onboard propellant tank rather than air as propellant.

  • how to grab nothing an push from it? only problem is NASA doesn't release it to the masses. 7 billion ppl at a problem it gets solved.!

  • The net through which the ionized gas passes destroys itself and requires replacement with the use of several hundred kilos of gas. Connect can not work indefinitely.

  • They have a small acceleration but can accelerate for a long time due to high fuel efficiency. They require a lot of electricity that would best be delivered from a nuclear reactor. Unfortunately, there is currently no such technology and interstellar flights are currently not possible.

  • I have a doubt cant we just use helium (hot air)balloon to reach at the halfway from end of atmosphere and can we even use a light thin vaccume chamber maybe made of graphene or something to make balloon like thing to reach almost edge of space and then just launch our small ion thruster rocketor sattelite slowly.
    Is this even possible practically i m really curious

  • You know the saying, you don't need to be a rocket scientist? Actually you do, and bring friends – this one is important and doable!

  • Where do the electrons go, are they ejected? I would think the low self capacitance would cause the voltage to rise, or is that not an issue unless coming into contact with something?

  • Geoffrey S Tuttle says:

    Ion thrusters won't get us off the ground so why do you compare them to chem rockets? What else can get us from the ground to orbit? Can't we fly a space-plane into orbit with a combination of scram jet and chem rockets yet?

  • Sir I think it is the phenomenon used in UFO same structure with propulsion like this only sir can't u try to make space craft using this phenomenon

  • If like 99% of the universe is made out of plasma couldnt we make some fucking plasma absorbing thing to us it on our plasma rocket. And to get to the atmosphere we use one of those roller coaster launcher thing like in tommorow land.

  • i whant you generations to embrace , is that the earth is a closed system , we cannot live the earth , there's no place to go.

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