Real economies are made by saving even 8.5% of the cost of an airship's gas. That's real money. Plus, that hydrogen won't escape the vessel over time, so that's a percentage you don't have to keep refilling.
Its about your customer's perceptions of risk. Key line: "Are the cost savings by using a 8.5% mixture of hydrogen worth all the trouble and effort it will take to convince your customers that the mixture is safe, as opposed to avoiding the safety questions altogether by using 100% helium?"
Have you worked with hydrogen? Being less prone to leaving than He is an extremely low bar and very far away from the claim that it doesn’t ever diffuse through anything.
Diffusion works both ways, too. Oxygen outside of the membrane will also slowly diffuse into the hydrogen and helium mix, further complicating any attmpts to remain non-combustible.
No, but the post I replied to, and apparently you felt the urge to reply to my comment. But I now understand that you did not intend to contribute to the discussion, thanks for the clarification!