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Comment by NikkiA | Hacker News Reader

What decides if it's an airship or not is not whether it has wings, but whether it's lighter than air. This thing is lighter than air, thus it is an airship.

Yet more terrible writing by the BBC.

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Uh, cite for that? Sorry, that's ridiculous pedantry. It's very reasonable to call the thing an airship, or an aeroplane (something done in the article only once, and in the context of a sourced quote justifying the distinction no less). I'm aware of no dictionaries or professional categorizations this article violates. It's a device that spans the boundary, and the article is literally about that, as the technology is (well, sorta) interesting.

Why is lack of adherence to your personal aeronautical jargon preferences a criterion for "terrible writing"? And why is this the top comment in the topic? Come on folks.

"The central fuselage is filled with helium, which makes it buoyant so it can ascend like a balloon."

"And inside that there's another bag with compressors on it that brings air from outside, compresses the air, which makes the aeroplane heavier and then it descends like a glider."

Sounds like it's an air submarine. The description of the variable buoyancy sounds pretty much like what a submarine does.

This is not really accurate. Submarines maintain roughly neutral buoyancy and use a motor for propulsion. They can use lifting surfaces for buoyancy control, but they need the motor to move forward. Airships operate on essentially the same principle--- airships are closer to "air submarines" than "air ships."

This device is an air-equivalent of an underwater glider.[0]* It establishes positive buoyancy to rise through the fluid (air, in this case, rather than water) and then establishes negative buoyancy to enter a dive, after which it glides just like any other glider.

The difference between this thing and a 'normal' glider is that it uses buoyancy to rise in altitude rather than needing to be towed by a conventional airplane.

[0]https://en.wikipedia.org/wiki/Underwater_glider * An underwater glider being the water equivalent of a... glider.

I might be misunderstanding things but it sounds like the "breathing" (compressing atmospheric air) gives it variable density? I guess it makes it a sometimes-an-airship.

It's both heavier and lighter! There's a compressor that can bring air in from the outside and make it heavier than air, and then this air can be released making it lighter again. This is explained in the article. It really is something new.

Like a hot air balloon which becomes heavier than air or lighter than air by regulating temperature in order to ascend or descend? That's fancy tech as of year 1800.

As long as we're nitpicking terminology, hot air balloons aren't airships either, they're aerostats. And they certainly don't use their variable bouyancy to propel themselves in directed flight. Saying this thing is just a hot air balloon is like saying an airplane is just a glider.

How would a more traditional airship descend, if not by becoming heavier than the air surrounding it?

It's new because it is being done in the atmosphere. I work with Autonomous Underwater Vehicles (AUV) which have employed this method of propulsion for at least a decade. For AUVs the variable buoyancy is achieved by having an expandable bladder of fluid which can be contacted to allow ballast to enter or expanded to expel ballast. Check out Slocum gliders if you are curios

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