The potential for LH2 (liquid hydrogen) is enormous. That’s matched by the logistical and technical difficulties in exploiting this gas’s great potential. It offers energy for a means of propulsion that is nowhere near as environmentally damaging as existing means.
Society already integrates hazardous liquids and gases into everyday life. Each one has been through several iterations. It has been a rollercoaster. Each one has been at the root of disasters, at one time or another.
- We use gas for cooking and heating in domestic settings. Periodically explosions demolish buildings. Leaks cannot be ignored. Harm can be done.
- We use light and heavy oils widely in transport systems. Periodically intense fires burn vehicles. Care in handling is essential. Harm can be done.
Without having to say it, both above harm the environment. The search for non-CO2 emitting ways of flying is urgent. Here, I’m writing about harm to people. Physical harm. The business of aviation safety.
Often the physical harm is not associated with the design of the systems used but to the maintenance of those systems. Naturally, there was a learning curve. If we look at early versions of those systems, fatal accidents and incidents were far more regular. So, here’s the challenge for aviation. How do we skip the dangers of the early learning phase? How do we embed rigorous maintenance practices from day one? Big questions.
On the first one of these, lots of fine minds are engaged in putting together standards and practices that will address good design. If this works, and it will be tested extensively, the chance opens for introduction to service with a great deal of confidence that the main risks will be managed.
On the second of these, there’s not much happening. You might say there’s an element of chicken and egg. The shape and form of future LH2 systems needs much more work before we can think deeply about how they will be maintained.
I think that’s wrong. It’s old-fashioned thinking. As the industry has often practiced, making the systems first and then devising ways of maintaining them while in-service. That’s yesterday’s reasoning.
Making aviation system maintenance the Cinderella in the LH2 world is to invite failure. This is a situation where advancing the consideration of how the in-service realm could work, day by day, is necessary. It’s advantageous.
Here’s my reasons.
- There are generic approaches that can be tested without knowing the detailed design. That can take existing learning from other industries, like chemical and space industries, and consider their application in aviation.
- Emerging technologies, like machine learning, coupled with large scale modelling can provide ways of simulating the operational environment before it exists. Thereby rapidly testing maintenance practices in a safe way.
- It’s imperative to start early given the mountain that needs to be climbed. This is particularly true when it comes to education and training of engineers, flight crew, airport and logistics staff and even administrators.
Everyone wants to accelerate environmentally sustainable solutions. When they do get to be in-service, they will be there for decades. Thus, an investment, now, in study of maintenance systems will pay dividends in the longer term. Remember, early fatal accidents and incidents can kill otherwise sound projects or at least put them back on the drawing board for a long time.
NOTE 1: I didn’t mention Liquefied Petroleum Gas (LPG). It’s in the mix. Another CO2 contributor. LPG containers have pressure relief valves. LH2 containers will likely have pressure relief valves too. That said, venting LPG is a lot more environmentally damaging than LH2. From a safety perspective they can both create explosive conditions in confined spaces. Maintenance staff may not need to carry a canary in a cage, but they will certainly need to carry gas detectors when working on LH2 powered aircraft. Our noses will not do the job.
NOTE 2: Events on the subject: https://www.iata.org/en/events/all/iata-aviation-energy-forum/
https://events.farnboroughinternational.org/aerospace/sustainable-skies-world-summit-2024
2024 ICAO Symposium on Non-CO₂ Aviation Emissions
John Vincent 