What is the future of Hydrogen in Aviation? Good question. Every futurologist has a place for Hydrogen (H) in their predictions. However, the range of optimistic projections is almost matched by the number of pessimistic ones.
There’s no doubt that aircraft propulsion generated using H as a fuel can be done. There’s a variety of way of doing it but, the fact is, that it can be done. What’s less clear is a whole mass of factors related to economics, safety and security and desirability of having a hydrogen-based society.
H can be a clean form of energy[1], as in its purest form the process of combustion produces only water. We need to note that combustion processes are rarely completely pure.
It’s an abundant element but it prefers to be in company of other elements. Afterall, the planet is awash with H2O. When H is on its own it has no colour, odour, or taste. In low concentrations, we humans could be oblivious to it even though there’s a lot of it in the compounds that make us up.
Number one on the periodic table, it’s a tiny lightweight element that can find all sorts of ways of migrating from A to B. Ironically, that makes it an expensive element to move around in commercially useable quantities. H is often produced far away from where it’s used. For users like aviation, this makes the subject of distribution a fundamental one.
Part of the challenge of moving H around is finding ways of increasing its energy density. So, making it liquid or pumping it as a high-pressure gas are the most economic ways of using it. If this is to be done with a high level of safety and security, then this is not going to come cheap.
There are a lot of pictures of what happens when this goes wrong. Looking back at the airships of the past there are numerous catastrophic events to reference. More relevantly, there’s the space industry to look at for spectacular failures[2]. A flammable hydrogen–air mixture doesn’t take much to set it off[3]. The upside is that H doesn’t hang around. Compared to other fuels H is likely to disperse quickly. It will not pool on the ground like Kerosene does.
In aviation super strict control procedure and maintenance requirements will certainly be needed. Every joint and connectors will need scrupulous attention. Every physical space where gas can accumulate will need a detection system and/or a fail proof vent.
This is a big new challenge to aircraft airworthiness. The trick is to learn from other industries.
NOTE: The picture. At 13:45 on 1 December 1783, Professor Jacques Charles and the Robert brothers launched a manned balloon in Paris. First manned hydrogen balloon flight was 240 years ago.
[1] https://knowledge.energyinst.org/collections/hydrogen
[2] https://appel.nasa.gov/2011/02/02/explosive-lessons-in-hydrogen-safety/
John Vincent 