Something I've been following closely. Sergey Brin, co-founder of Google, is building a 200 meter long rigid airship in one of the Moffet Field Hangars. It's a personal project of his. It's being built for a few years now and they've kept it under wraps. So far no pictures of it or its construction although they reported most of the frame was done. It's supposedly a real airship, not a hybrid aircraft.

I've been fascinated by airships for years, and hope to fly on the Zeppelin NT in the future, and in a few years, I might consider getting into hot air ballooning as well.

Sergey shares this fascination. Not so long ago they found large helium deposits in Tanzania, which will provide enough helium for the coming decades, and keep this small industry alive, if not allow it to expand a little. We might see some other interesting Airship projects pop up. I don't expect it to return to its former glory. But I am especially interested in what Sergey is building as it doesn't need to be commercially viable. Most other Airship projects failed because they go bankrupt. This is just a billionaire side project. With modern tech and enough funds, something really, really interesting can be created. I think his airship will be completed within 2 years.  Will be an amazing sight to see. The biggest RIGID airship since 1938.

   I love blimps as we call them here.  I don't see why they couldn't succeed commercially.  The reason they failed, of course, is because they used to be hydrogen filled.  That's no longer the case.  I'd love to take a long trip in one. 

Rat Man wrote on Apr 16^th, 2019 at 7:12pm:

I love blimps as we call them here.  I don't see why they couldn't succeed commercially.  The reason they failed, of course, is because they used to be hydrogen filled.  That's no longer the case.  I'd love to take a long trip in one.

The lack of cheap, abundant helium is what suffocated the industry. In the early days there was barely enough helium mined to fill a few large airships. Today we have enough helium to support a small industry, but the future regarding helium supplies on earth is still uncertain, and that is why investors FLEE whenever they hear the word airship, and rightly so.

Airships leak. Helium is so small that every year they lose like 10 percent through the envelope. And once helium is in the atmosphere it goes into outer space. Other than mining the stuff, there is only one way we can produce helium artificially and that is with nuclear fusion, but the amounts produced would never be enough to fill a large airship. So, as long the helium supply issue isn't solved, airships are simple not going to return on a large scale. But there is plenty of it to support the current fleet of airships in the world, if not allow it to double in size.

The current Goodyear blimps are in fact German made Zeppelins. They still call them blimps however as it is good branding. The older ones, the real blimps, were phased out a few years ago. The new German-made ones aren't technically blimps but semi-rigids. They combine an internal framework with internal pressure. A blimp however only uses pressure and a nosecone to maintain its shape.

given modern materials and technology - there's actually no logical reason you couldn't go back to using hydrogen.

Most of the other fuel we use has explosive fumes. So that's not the issue. Given modern materials you could cut the hydrogen leakage to almost nothing. Pump it through oxygen to turn any you don't need into water. Use solar power to crack the water back into oxygen and hydrogen. You'd have an almost totally closed system that would just need a little water every now and then.

Easy to generate, easy to clean up unlimited amounts available.

Dirigible's are what I'd like to see make a come back.
Were I a bilionaire, I would build one :-) 
Lots of personal electric powered personal air vehicles around now, so you'd never need to land.
It's totally doable.

Once we get lightweight flexible solar panels and battery/electricity storage improves, you could run one solely on hot air, electric engines and all via solar power.

Or a closed loop hydrogen system.

The case against Hydrogen is economic more than technical but there are a lot of technical issues with hydrogen as fuel too. It takes a ton of energy to liberate hydrogen. It’s difficult to store unless it’s really cold because it can pass right through the walls of a storage tank over time.  Modern materials don’t fix fundamental physics issues of the mean free path, so it will always be leaky unless you’re doing some sort of electromagnetic containment or something. Recycling hydrogen isn’t as simple as mixing with O2 either... at least not at room temperature. You have to put energy in but when you do, the reaction is exothermic and can run away if not properly contained.  Dirigibles are pretty cool, but there’s a lot of hurdles still to overcome.

that's it be negative. You forget I'm only building this if I'm a billionaire :-)
All problems can be fixed with enough money :-)

Curious Aardvark wrote on Apr 17^th, 2019 at 12:03pm:

that's it be negative. You forget I'm only building this if I'm a billionaire :-) All problems can be fixed with enough money :-)

Sergey Brin originally wanted to use hydrogen, but it was not permitted.

The real die-hard airship fans usually do not shy away from hydrogen as lifting gas, given that the ship is properly engineered for it. I too believe it could probably be made safe enough, although I don't see it happening. Governments don't want it, investors don't want it, the general public doesn't want it.

Now what would really be interesting is a helium-filled nuclear airship. A case was made for this by German engineer Veress. At first glance it sounds crazy, until you study the concept more. You can read about that here - https://imgur.com/a/xEdOjHr

One problem is that combining the words "nuclear" and "airship" sounds like a really good way to kill investment.

well if you ar going nuclear - hot air makes way more sense.
You could have a continuous flow through and use the cooling air as propulsion.
nuclear power plants can be made pretty small these days.

But I suspect it would be something like project Orion. People would object to having nuclear over their heads :-)

Curious Aardvark wrote on Apr 18^th, 2019 at 6:17am:

well if you ar going nuclear - hot air makes way more sense. You could have a continuous flow through and use the cooling air as propulsion. nuclear power plants can be made pretty small these days. But I suspect it would be something like project Orion. People would object to having nuclear over their heads :-)

Hot air has worse lift than either hydrogen or helium.
A nuclear airship could use heated-helium, though. This would have as much lift, if not more, than standard hydrogen.

The ship would have to be really big though, +300 meters long, 60 meters diameter. Rigid airships only start making sense at those sizes and beyond, to be honest. And nuclear starts making sense when airships become that big.
A big problem with regular airships is the burning of fuel, which lightens the ship. A nuclear airship would not be bothered by this, and could stay in the air for nearly a decade. Previous airships topped out at 130 km/h, a nuclear airship could/should reach 200 km/h and more.
It would be able to carry +500 people, and be quite spacious.
There would be no exhaust and much less noise pollution.

But yeah, two big problems here. Nuclear isn't going to get approved, and even though airships become much more economical at greater size, the opposite is the case for the hangars.