A small aircraft jet engine is being tested in a corner of a military site on Salisbury Plain, which could lead to huge changes in the aviation industry.
The engine is not very different from other engines. It is a Rolls-Royce gas turbine that is used on regional planes.
The fuel being used is not normal. This is the first time an aircraft engine has been run on hydrogen.
Engineers cluster around an array of screens in the control room, a safe distance away, as it sits securely fastened to a sturdy test rig.
Rolls-Royce is conducting the tests with easyJet.
To show that it is possible to run and control a jet engine using hydrogen fuel is the immediate goal.
The plan is for hydrogen power to play a major role in allowing the aviation industry to continue growing.
Alan Newby is the director of aviation technology at Rolls-Royce.
We usually run this thing on fuel. Carbon dioxide is produced when Kerosene burns.
When hydrogen is burned, it doesn't produce any carbon and that's the beauty of it.
The project is being supported by easyJet.
The company thinks hydrogen power is the best way to reduce emissions.
David Morgan, easyJet's chief operating officer, said that they started looking at what might power the aircraft of the future.
The battery technology was not going to work for large commercial aircraft that we fly.
hydrogen is a very exciting proposition for us.
Hydrogen provides more power than batteries. Larger planes can't be powered by batteries.
It's a long way off. The tests have shown that hydrogen can be used to start a jet engine and run it at low speeds.
It will take a lot of research and a lot of money to build a new engine that can power a passenger aircraft safely.
The aircraft needs to be changed. The space required to fly the same distance is four times that of hydrogen.
It needs to be cooled to -253C in order to make it into a liquid. It needs to be turned back into gas before being burned.
Alan Newby at Rolls-Royce said there was a big change from the aircraft point of view.
They have to have a tank with hydrogen. You have to keep it cold.
There is an issue of how you feed it to the engine.
The environmental benefits of hydrogen are dependent on where the hydrogen comes from.
Green hydrogen is produced at the European Marine Energy Centre in the Orkney Islands.
The electric current splits water into hydrogen and oxygen. Waves and wind power are used to produce electricity. It's a very clean fuel due to this.
Most of the hydrogen produced for industrial use is obtained from a process that mixes high temperature steam with natural gas.
A lot of carbon dioxide is released into the atmosphere as a result of this. Burning fossil fuels provides a lot of energy.
Blue hydrogen is one of the alternatives. The carbon dioxide is captured and either stored or recycled.
This could make it a cleaner fuel. The view was challenged in a paper by researchers.
They said that using blue hydrogen could be harmful to the planet.
There's a lot of hydrogen hype at the moment, says Matt Finch, UK policy director of campaign group Transport and Environment.
People are saying that they need hydrogen. It's heard for cars, trucks, ships, planes, home heating, and chemicals.
The UK is currently producing zero green hydrogen. It is not possible to fulfill all the needs of everyone.
It's believed that green hydrogen will probably have to be rationed for decades to come, and that aviation may not be a priority for governments.
Zero- emission hydrogen planes are likely to be decades away.
They're likely to be limited to short haul markets at first. Synthetic sustainable fuels are often used on long haul routes.
The first tests on Salisbury Plain could be seen as a small step towards a technological revolution in the industry.