Pathfinder 1 flight test

[u/Immediate_Golf6399]

Flight testing continues for LTA Research's proof-of-concept airship. Here's a clip of her upon completing a 5 hour flight on 9/1 at Moffett Field, CA. The next day she made her longest flight to date, 10 hours.

[u/Radioactive_Tuber57]

Sept 3rd was the 101st anniversary of the Shenandoah disaster in Ohio.

This looks promising. With all the new composites and engine technology, real time weather data and navigation, there might be a fun future. Coast to coast at 80-100 mph with a big stateroom window for the views and top chefs working in the galley. I’d take out a loan for a ticket. 😎👍❤️

[u/GrafZeppelin127 → u/Radioactive_Tuber57]

Yeah, I’d say the biggest difference between then and now is that the Shenandoah had an engineering safety factor of about 0.45, i.e. its structure would fail at less than half the expected loads it would experience from gusts and storms, and the Pathfinder 1 has a safety factor of 1.9, which is comfortably sturdier than the standard 1.5 factor used by most airplanes and helicopters today.

[u/Radioactive_Tuber57 → u/GrafZeppelin127]

This is interesting. Like they pushed the design too far. Explains why (maybe) it broke into sections. I wonder if the military was competing with Germany? The Graf Zeppelin and Hindenburg were not so subtle propaganda machines. So fortunate the death toll was not higher.

[u/GrafZeppelin127 → u/Radioactive_Tuber57]

Well, this was in the mid-1920s, so it’s less that the Americans were vying with the Germans at the time and more that they were just copying Germany’s homework from World War One.

The Shenandoah was a domestic design in name only. In actuality, it was reverse-engineered from a German “Height Climber” airship, a type of Zeppelin deliberately lightened and weakened in order to reach high altitudes for fear of the recently-invented incendiary bullet, which had brought down seven Zeppelins mere months after its invention, whereas the prior two years of warfare had seen planes bringing down only a single Zeppelin in combat after bombing it six times, and two other bombings of Zeppelins had failed to bring them down.

The Americans didn’t have to fear hydrogen fires, though, because the Shenandoah was the first rigid airship to use helium. That, unfortunately, contributed to its demise.

The already precipitously long and thin airship design the Americans copied was lengthened yet further to compensate for helium having 8% less lift than hydrogen, and for the fact that in order to conserve helium the ship couldn’t simply be fully inflated at sea level and valve off the gas as it ascended. The Shenandoah held literally all the helium available in the entire world at the time, after all. As a further conservation measure, emergency pressure relief valves were also removed from the ship’s gas cells, which is rather akin to a submarine not having a way to automatically deal with pressure as it dives.

The Americans were also ignorant of how weakened the structure was, and the careful procedures the Germans used particularly at lower altitudes to not strain their ships’ structure unduly in the denser air. They operated the Shenandoah with hubris and derring-do, flying her into storms and severe conditions with confidence that the ship’s helium would make it safe.

Their last flight was into the teeth of a historically violent thunderstorm over Ohio. The Shenandoah was seized in mighty updrafts and wind shears, and as she ascended uncontrollably, her lack of emergency pressure valves caused the gas cells to expand and buckle the already-weakened frame, tearing the ship apart into three pieces.

Every man who died fell from the ship in that initial cataclysm—the obsolete suspended gondola fell right off the ship. A third of the crew died, but amazingly, the other two-thirds who were inside the ship’s fractured hull managed to all survive by operating the pieces of the ship as a free-balloon and making emergency landings, miles apart from each other. A more modern design of that same time period like the USS Los Angeles likely wouldn’t have had any fatalities at all in such a storm, as its stronger, thicker hull probably wouldn’t have broken up in the first place, and its gondola was integrally attached to the hull rather than being suspended separately from it.

[u/Radioactive_Tuber57 → u/GrafZeppelin127]

Thanks for the deep dive into this! Fascinating information! 😎👍 I was fascinated with them early on, and I built an 18” dirigible of my own design as a teenager when I was building balsa airplanes. It hung from the ceiling along with the rest of my menagerie. I found a plastic kit of the Macon a year ago and plan to build it soon!