Liquid Hydrogen Powered aircraft in 1988

Tenger

Found this on flightglobal.com. Brillant. God bless Russian ingenuity.

Twenty years ago, long before ‘biofuel’ became a marketing hook, the Soviet Union quietly flew for the first time a modified version of the Tupolev Tu-154B to demonstrate how aircraft could be powered with an alternative energy source.

Designated the Tu-155 the aircraft took to the air on 15 April 1988, its thrust partly generated using liquid hydrogen..................................

http://www.flightglobal.com/blogs/flight-international/2008/04/tupolevs-cryogenic-tupolev-tu1.html

dogmatix

Aye - a good idea. In theory the only emissions from a hydrogen powered jet would be water vapour.

The main downside to Hydrogen fuel is it requires much greater amounts to provide the same "power" as standard aviation fuel. So either much of the internal space is taken up by the fuel meaning considerably reduced cargo and passengers carried or you end up with an airliner looking like the airbus beluga. Either way it would be very costly, so unless there are major advances in the engines themselves i can't see it taking off.

pclancy

Why isnt it mainstream? Well money of course! Theres probably another 80 years of oil left so the fatcats of the worlds governments and oil businesses are quite happy with the way things are now...if the soviets could do that 20 years ago theres no reason except for the above for us not to be flying in near totally green aircraft now had the technology been given proper investment and research. Until we really start to run out of oil nobody wants to fund stuff like that, theres too much big money tied up in the worlds oil markets and industries. Sad but a reality at the moment. Imagine a world full of hydrogen fuel cell cars, busses, trains, ships and planes that only had water coming from their exhausts, it would be fantastic.

Refreshingly Iceland is well on its way to become the worlds first non-fossil fuel dependant country, its a small start but will give the world a chance to see whats possible on a small scale. http://www.tve.org/earthreport/archive/10Sep2001.html

New Zealand too is doing well and plans to have 90% of its power generated from renewable sources as soon as 2025. They've already got loads of thermal, solar, geothermal and water powered power stations and are installing tidal turbines at the moment near wellington to see how they work. http://www.stuff.co.nz/dominionpost/4505606a23882.html

Back to aviation though, wouldnt it be nice see Boeing and Airbus push the engine manufacturers for a cleaner solution? More efficient aircraft are appearing but are out of the financial reach of most african, south american and some asian carriers that are still flying the worlds fleet of "classic" 737s for example...

Also IMO military aviation should be closely looked at for a replacement fuel source...The world's military burns a quarter of the worlds jet fuel and is responsible for 70% of ozone depleting CFCs!!! and guess what...the US military generates more hazordous toxic waste then the top five chemical companies combined.

Deacon Blues

One of the main problems with liquid hydrogen as a fuel source is that it takes more times the energy to make it than it releases when burnt. Yes, it sounds wonderful. you burn the liquid hydrogen and the main emisson is water (there are also some nitrogen compounds when it's burned in air, and they need to be controlled). However, you've used more energy to make and store the liquid hydrogen than is released. So, if you're using oil to provide the energy to make the liquid hydrogen, it's cheaper and more efficient to use it directly to do the job of the liquid hydrogen.

Only if the energy used to make liquid hydrogen is (relatively) cheap and plentyful, maybe either green or nuclear, does liquid hydrogen become efficient as a fuel. Also, as it does not exist naturally, it is manufactured, and the main and cheapest way is by steam methane reforming, which uses natural gas. Once the natural gas runs out, and we go back to basics, and manufacture hydrogen from water, then the energy required becomes much greater, particularly on an industrial scale.

So, while liquid hydrogen seems like a dream fuel, it isn't. Because it doesn't exist naturally, it really needs to be looked upon as an energy transfer medium, rather than a fuel, and the energy required to provide a global hydrogen economy is vast, many times more than required with the current global oil economy.

tracker-man

Hydrogen fuel can be prepared by electrolysis of water (i.e. passing an electric current through it) to dissociate it into its component parts of hydrogen and oxygen. When the hydrogen fuel is burnt it combines with atmospheric oxygen to produce non-polluting water vapour. If the electricity used to produce the hydrogen comes from alternative sources such as wind, tidal or wave generators then a closed, totally environmentally friendly, cycle can be created.
As early as 1956 experiments took place in the USA with a hydrogen powered Canberra bomber. The Russians experimented with a triple engined Tupolev Tu-154 which first flew in 1988. Just one of its three engines was powered by hydrogen. At the start of the 1990s DaimlerChrysler Aerospace/Airbus of Germany and Russia's Tupolev began work on a project named Cryoplane for hydrogen powered aircraft propulsion systems. The plan was to initially develop a demonstrator, hydrogen powered, modified Dornier 328JET aircraft but by 1999 the project had been halted because of high costs. The project was relaunched in April 2000 with 35 companies from 11 European Union member countries working on a two year preliminary study of hydrogen powered aircraft propulsion systems. EIADS Airbus are leading the project.


Model of a Cryoplane There are a number of modifications required to current aircraft engines and aircraft structures before hydrogen fuel can be used. Hydrogen contains 3 times as much energy per Kg as kerosene which means that only a third as much fuel by weight needs to be carried to cover a certain range. However, hydrogen is a significantly less dense fuel than kerosene and will need much larger aircraft fuel tanks even when the fuel is stored in liquid form at -253 °C as it will have to be. Even taking into account the fact that only one third of the weight of hydrogen will be required, fuel tanks on a hydrogen powered aircraft will need to be 4 times the volume of those on conventional aircraft. These tanks will have to be heavily insulated because of the low storage temperature and spherical or cylindrical tanks placed above the main passenger compartments are the best option. The fuselage of aircraft will become stockier to accommodate this change.
Only small modifications will be needed to enable aircraft engines to burn hydrogen but specialised fuel pumps, pipes, control valves and refuelling systems will be needed in a hydrogen powered engine. This has resulted in some of the original Cryoplane partners (Daimler-Benz Aerospace and Tupolev) filing a number of patents on such systems i.e. US5548962, US5505053 and US5660358.
As the hydrogen fuel will be mixed with air (specifically the oxygen contained in air) and then ignited in the engines some nitrogen oxides (NOx) emissions will result from the combustion process since nitrogen is the major component of air. However, NOx emissions from hydrogen fuelled engines can be lowered by up to 80%, as compared with kerosene burning engines, using a process called Micromix developed by the University of Aachen. The large amounts of water vapour produced by hydrogen engines could also be a problem as water vapour acts as a greenhouse gas but only at altitudes above 10 Km. Restricting the altitude at which planes fly could solve this problem.
It is likely that people's fear of hydrogen as a fuel will have to be overcome. Ever since the Hindenburg and other hydrogen filled airship crashes people have had a fear of the explosive properties of hydrogen as a fuel. In fact hydrogen is a safer fuel than kerosene. In the event of a crash, freed hydrogen fuel will rise quickly and any fire will result in an upward pointing flare whereas kerosene will form a wide carpet of flame around a crashed aircraft. Moreover, hydrogen is very fast burning with very low radiation of heat and its combustion products are non-toxic. Many people forget that when the Hindenburg caught fire in a landing accident it did not explode and of the 97 passengers and crew on board 62 survived.