The Magic of Ion Thrusters

As you get into the spaceship, you prepare for your long journey ahead. 8 months is what you will spend, hurling yourself toward Mars, in a small room with the other astronauts.

One day as you’re bored, you think about a new and potentially game-changing idea in the market of space transportation.

Ion thrusters are these really cool systems of propulsion that basically shoot ions out the back. They are able to transport things at speeds compared to the speed of light.

Conventional chemical rockets can go up 28 000 kilometres per hour but, Ion thrusters have the power to go almost 350 000 kilometres per hour.

If we humans will be able to harness this great force, we would be able to revolutionize this field and make the option of things like living on Mars, much more feasible.

Chemical Rockets

Before we get into how ion thrusters work, we need to understand how the three main types of chemical rockets work, and all the things they can’t do:

Solid Propellant Rocket Engines

A solid fuel engine is an engine where the rocket fuel(either petroleum, cryogens, or hypergolic) is mixed with an oxidizer, and they are then set as a solid of propellant grain inside a solid cylinder.

At the bottom of the cylinder, there is a combustion chamber. where everything is mixed, then it is lit.

As all the solid propellant fuel is lit, a combustion process takes place where exhaust gas high temperatures and pressures are pushed out the combustion chamber into the nozzle where they create thrust, due to Newton’s third law.

Liquid Propellant Rocket Engines

Liquid propellant rockets use liquid fuel, such as kerosene, or liquid hydrogen, as well as an oxidizer such as liquid oxygen.

They are both stored in separate tanks, and then later, pumped into combustion chambers.

They are sprayed out through the injection nozzles, where they rapidly mix together and react, causing thrust.

An advantage with liquid propellant rockets is that they can control the amount of thrust being produced.

Hybrid Propellant Rocket Engines

Hybrid propellant rocket engines use a system where they fuel as a solid inside the combustion chamber, and there is a liquid oxidizer stored in a separate chamber.

When the rocket is ready to produce thrust, the pressure is brought to the oxidizer tanks where a valve is opened, the oxidizer is then released into the combustion chamber, where it reacts with solid fuel and is ejected.

The reason that I talk about how chemical rockets work is for they suck. The amount of fuel and energy it takes to get the smallest things into space is crazy.

Chemical rockets are only 35% efficient, so some people would say; “there is massive room for improvement” but, many scientists and I think the way to go is ion thrusters.

How Ion Thrusters Work

In the simplest forms, ion thrusters don’t heat up gas, but they give the gas(xenon) an electric charge, then, they are called ions and are shot out the back at ~90 000mph.

Although ion thrusters now seem simple, they are composed of so much more than that.

Instead of hot gasses, ion thrusters eject ions, which are atoms or molecules which have an electrical charge for they've lost(proton) or gained an electron.

In the case of an ion engine, they are emitting positively charged ions, which have lost an electron.

Once you’ve created all of those ions, you can now direct them using magnetic fields, accelerating them into space at ridiculous(~90km/s)speeds.

The magnetic fields would either use a form of permanent magnets or an electromagnet to create magnetic fields strong enough to reduce back streaming of the electron, without perturbing ion trajectories.

The one question that may then arise is: how would you actually just make ions out of thin air?

The gridded ion thruster is a thruster that is able to generate a plasma, inside the spacecraft.

The gridded ion thruster puts massive amounts of neutral propellant atoms like xenon and electrons. When the two collide, they create even more electrons, turning them into positively charged ions.

The process keeps repeating, but every time one positively charged ion makes it out, it is met by a negatively charged ion, which is moved out through another, much smaller grid at the end of the chamber

Once this process happens, the ions are accelerated out the back of the ion thruster, creating thrust and movement.

Though, you may be thinking, wouldn’t this take a lot of energy, with a ton of weight going towards batteries?

The answer is yes, this process requires a ton of energy, but luckily, we are able to attach solar panels to the spacecraft which was almost nothing compared to the batteries and engines required to use something like this normally.

Ion thrusters are shown to be about 90% efficient. That makes them almost 3 times more efficient than conventional chemical rockets, and we would be able to go so much further in space. Ion thrusters are also considered to be one of the most efficient forms of rockets.

Deep Space 1 Mission

For a while now, NASA has been working on Ion thrusters. To make a fully functioning ion thruster, assuming there are no problems, it would cost almost 50 million dollars.

In 1998, NASA decided to pile up all of their concepts that could break down, proving catastrophic for the future applications of whatever technology and put them on a mission called the Deep Space 1 mission.

Some of the technology on the spacecraft are:

• Solar Concentrator Array with Refractive Linear Element Technology (SCARLET)
• Autonomous Navigation System (AutoNav)
• Remote Intelligent Operations Software (Remote Agent RAX)
• Beacon Monitor Operations Experiment.
• Small Deep-Space Transponder (SDST)
• Miniature Integrated Camera Spectrometer (MICAS)

But the most expensive and the tech with the biggest application is the ion thruster.

The deep space 1 mission turned off its engines in 2001, just 3 years after starting, but it proved some really cool things.

686,029,871 kilometres is how far away comet 19P/Borrelly is from the earth. For reference, the comet 19P/Borrelly is about six times further than Mars is to the earth.

This mission showed that ion thrusters work, and they are able to go really far without a major risk of breaking. As the mission was stopped, there was still about 10% of xenon fuel left, meaning that if necessary, it could leave its orbit from the sun and make it back to earth.

Future Applications

In the coming decade, there is a very good chance that ion thrusters will become more and more used.

Ion thrusters will be able to do crazy things and go crazy far compared to conventional rockets. Once we start to modernize the trip to Mars, a lot of people would want to do it, but they would not want to wait the 8 months to get there.

Ion thrusters will be able to make that trip in a fraction of the time, making it even more economically viable.

A trip to Alpha Centuria, our closest star system, it’s 4.367 light-years away, but that trip could be done in one human lifetime.

Not only will ion thruster be able to travel really far really fast, but it will be able to do tasks like clearing all the debris and junk from around the earth.

A task like this would be hard for it takes a lot of fuel to go around the earth’s orbit collecting things. A task like this would make the takeoff of future rockets much easier.

TL;DR

• Chemical rockets are only 35% efficient, and ion thruster could be 90% efficient, making space travel a lot easier and faster.
• Ion thrusters give the gas xenon an electrical charge, then, they are shot out the back at ~90 000mph.
• The deep space 1 mission was a mission where they put all risky technology together and put it in space. One of the technologies on that was ion thrusters, and it did amazing things.
• Ion thrusters could get humans to our closest star system Alpha Centuria(4.367 light-years away) in a single lifetime.
• Ion thrusters could help in clearing all debris from the earth’s orbit.