Airlander 10: Longest aircraft damaged during flight | Hacker News Reader

Airlander 10: Longest aircraft damaged during flight

bbc.co.uk

47 pointsteh_klev49 comments

A spokesman said: "The flight went really well and the only issue was when it landed."

Well, that's kind of every air flight ever. Its sticking the landing that's the hard part. Its not the fall that kills you; its the sudden stop at the end.

Blowing up in midair, or spilling some of the passengers so that they land separately from the plane can be a problem, too.

Also catching fire while aloft can be an issue, cf the Hindenburg.

Virtually all buoyancy-based aircraft post-hindenburg use Helium or other non-combustive gases for buoyancy. Airliner uses Helium as well [1].

[1] https://www.hybridairvehicles.com/downloads/download/Airland...

> other non-combustive gases

What options exist other than helium?

There isn't really anything else -- if you look at a periodic table, you can see the next inert gas is Neon, but it is heavier than Nitrogen (which makes up most of the atmosphere).

Nitrogen itself is not easy to set alight, though.

But it would take an enormous volume of nitrogen to achieve significant positive buoyancy when the nitrogen is enclosed by much of anything. Air's mass is 28.97g/mol, vs. 28g/mol for N2. So, based on my vague recollection of chemistry, that means you only get 1g of container/cargo/engine for every 22.4L of gas enclosed.

> that means you only get 1g of container/cargo/engine for every 22.4L of gas enclosed.

For reference, the Hindenburg carried about 200 million liters of gas. A nitrogen craft would need approximately 1.52 million liters to carry a single 150#/68kg human being, not counting the additional gas needed for the craft itself.

So if you want to build a Hindenburg-size craft to carry about half a dozen people it might actually be plausible!

For the sake of argument, would it be possible to use vacuum? Maybe some kind of spongy structure, with no single points of failure, but lighter than air by way of being mostly nothing?

If your spongy structure is capable of withstanding a half decent vacuum it will likely be much heavier than the volume of that structure filled with air.

No, because there is no known material (even exotic stuff like nanotubes) that can hold a vacuum AND be lighter than the contained volume equivilant of air.

I was wondering the same thing. It would have to be a sphere, a thick shell constructed of an incompressible material such that the inward pressure causes compression. Some kind of honeycomb structure?

The weight of the shell depends on the area (goes up as the square of the radius). The lift depends on the volume (goes up as the cube). Seems like for a large enough size you might be able to get positive lift.

The inward pressure per square inch of shell is constant (14.7 lbs. per sq. in. at sea level with a total vacuum inside), so as long as the inward pressure is distributed evenly it doesn't seem like it has to be stronger just because it is larger.

Inside would only have to be a partial vacuum. You can heat the gas inside to reduce the pressure differential, which might not be too costly if the shell is fairly thick and provides thermal insulation. Here again the volume vs. area works in your favor.

Conclusion: Probably Buckminster Fuller could come up with something.

But it would still be only marginally lighter than hydrogen or helium, and require a much more sturdy support mechanism.

Some analysis on this topic has been done: https://en.wikipedia.org/wiki/Vacuum_airship#Material_constr...

Neon is actually less dense than Nitrogen. According to Wikipedia:

  Nitrogen..Density at stp (0 °C and 101.325 kPa) : 1.251 g/L
  Neon......Density at stp (0 °C and 101.325 kPa) : 0.9002 g/L

Nitrogen has a lower atomic number than Neon, but on the other hand Nitrogen is diatomic, which I imagine accounts for the greater density.

Neon is insanely expensive however.

But just imagine if you ran some high-voltage current through it..

Yeah lightning strikes could look cool.

None. I thought. Methane is also flammable and a vacuum is not a gas and not currently possible.

But wiki says Ammonia (Hard to combust)-

https://en.wikipedia.org/wiki/Lighter_than_air

Off planet you obviously have other options.

But a complex molecule might work I assume?

One of the advantages of large lighter than air craft is that they actually tend to crash in slo-mo, so the "sudden stop" tends to be pretty slow. In the case of the Hindenberg, a lot of the people who died did so because they jumped out too early and fell to their deaths, rather than "ride" the craft down.

Even in the worst disaster, the USS Akron, most deaths were due to drowning and hypothermia after the ship went down, rather than impact.

The majority of Hindenburg victims burnt to death - "riding the craft down" doesn't seem quite such an attractive option.

Well, obviously you don't want to hang around very long after its on (or even close to) the ground. IIRC, most of the burning deaths were crew-members in the upper parts of the ship who were either caught in the fire in its first stages or didn't have a way out even after it hit the ground. The lower decks weren't ignited till it hit the ground.

But the point is that "impact" wasn't a common cause of death for those who stayed in the ship until it was near the ground. Even when the lifting gas is being vented fairly rapidly, they tend to comedown at survivable speeds.

The ones who burnt to death were trapped with no way out. They didn't have the choice to ride it down.

Those were were not trapped either survived or jumped too early.

IIRC, most of the survivors simply waited near the bottom until landfall, then walked away. I think many of the victims had a choice between jumping or burning, but it definitely seems like a burning envelope is survivable if (your part of) the cabin doesn't catch.

Maybe the focus should have been on making the cabin nonflammable. Suspending the cabin with an air gap, and lining it (especially on top) with serious fireproof and heat-resistant lining, might have done the job.

It's true the aerostatic lift would help here, but the Airlander 10 is not actually a lighter-than-air aircraft. It's a hybrid and requires aerodynamic lift from forward movement in addition to lift from its engine-driven propellers.

The hybrid approach is puzzling to me because there are a multitude of advantages to be gained by being fully lighter-than-air.

Is 'not actually lighter-than-air' always true, or only when it is carrying 10 tons of cargo?

My understanding is that when talking about aircraft, "lighter-than-air" means that it's designed to require no additional lift to keep it aloft regardless of cargo. Anything requiring non-aerostatic lift would be considered a hybrid.

https://en.wikipedia.org/wiki/Aerostat

I can think of a couple of advantages of hybrids. You could unload cargo without the thing trying to shoot up in the air and a problem with airships in general is them being blown around by the wind which may be less bad with a smaller hybrids. Also if you emergency land the thing may stay there whereas a fully lighter than air one would tend to drift off.

As they say: "The aviation industry has a perfect track record - they have never left anybody up there."

That's a legit thing to say about a prototype on its second test flight. You expect some setbacks, and this is an encouragingly minor one.

A minor setback is having to curtail the flight due to a faulty reading on a pressure gauge or a minor power issue with the engine.

A nosedive landing that damages the cabin in perfect flying conditions is about the very worst thing that can happen on an aircraft test programme, even if the flight crew walk away

I'm just saying, a crash that would be a disaster in a regular flight can be "not bad, we learned something here" for a new design on its second test flight.

For anyone who has not had the chance to read it there is a good article from the New Yorker on airships: http://www.newyorker.com/magazine/2016/02/29/a-new-generatio....

It was a fun light read. Although at the end I just felt like I got a lesson in really expensive, and partially complete vaporware (vapor-commercial-ware?) and was left with little hope for their future.

I highly recommend that article as well. Though yes, like you I was left with a sense that this industry is never going to take off, so to speak.

As the saying goes, any landing you can walk away from is a good one. A great landing is one where you can fly the plane again.

Ah, ya beat me to that quote!

Growing up, we flew in my dad's 4-seat (and later 7-seat) Cherokee very frequently and he'd always comment on his landing. He judged his entire flight by how easy it was to identify when the tire made contact with the runway. I remember a flight in high winds that he put down so softly that nobody could tell when we hit the ground. I also remember a landing when I was alone with my dad where we encountered a cross-wind a few seconds before making contact resulting in my slamming my head into the top of the cockpit and yelling "Mother F*cker!" (I was 14, he'd never heard me swear before and it was a bonding moment that he shrugged it off and thought it was totally warranted given the circumstances).

Bad landings seem to be something that unites almost all pilots. The better ones make bad landings less often, but nobody is immune.

Regarding your bonding moment, one reason I like to fly by myself is so I can swear as much as I want. Part of me is always slightly terrified of having a stuck mic.

It nosedived on landing, and suffered some damage to the cabin. The crew was fine.

That's a huge win for lighter-than-air flight in my book. A jet aircraft would be a smear of aluminum, carbon fiber, and jet fuel all over the runway.

Actually, a nose-dive landing occurred at LaGuardia in 2013 - Southwest Airlines - I believe the incident had something to do with the front landing gear failing. There was a small fire (as you mention, jet fuel is quite flammable and if there's a leak and a spark, that's a foregone conclusion, I'd imagine).

But the aircraft itself didn't look too bad which is a testament to decades of engineering experience with a device of such complexity[0].

[0] And found a link! http://gothamist.com/2013/07/23/video_southwest_planes_nosed...

I guess that's why you're not supposed to take your seatbelt off until you get to the gate...

Jet aircraft rarely nose lands. I'd imagine piloting a 90m helium balloon might be a bit more difficult and therefore result in far more nose landings.

  "The company has denied claims from a witness that a line
  hanging down from the vehicle hit a telegraph pole about 
  two fields away from its landing."

Telegraph pole? Is that a British colloquialism or do they still have telegraph poles over there? Or was that how they knew the witness was lying?

British term for a wooden pole that has wires at the top, regardless of what the wires are actually for.

"Telegraph pole" in an article about an airship was pleasantly quaint.

Watch the 1080p version.[1] Did they have a control system failure, or was this pilot error? The front fans are steerable, but there's no sign of an attempt to correct the nose-down attitude as the craft dives. Watch the front fan positions. After the crash, the front fans move, but by then the cockpit has been crushed and there's probably nobody in control.

This thing is the same concept as the Skunk Works' P791 prototype - slightly heavier than air, steerable fans - but the flight controls seem to be much less effective and the landing gear is far worse.

[1] https://www.youtube.com/watch?v=DkYbw4R_-RQ

Lots of different descriptions around this story: "Damaged during flight"..."has been damaged after nosediving on landing"..."damage to its cockpit when it hit the ground"..."Collided with the ground"

But only one honest: "The Air Accidents Investigation Branch has confirmed it is investigating the crash"

It crashed. During flight it collided with a fixed object (technically an "ollision") resulting in damage to the aircraft. On its second a test flight, the experimental aircraft crashed.

They all look honest to me, and the one you're praising is much less informative than three of the four you criticize.

Down the Irons!

Empire of the clouds[0]: part two…

[0]https://en.wikipedia.org/wiki/Empire_of_the_Clouds

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