Why no vacuum or hydrogen based airships?

Factual Questions
281

Yes. I don’t really know what to go on to give you an answer. I guess each one of those engines is equivalent to a car engine. My car heats up enough for the heater to come on in about 5 minutes. A blimps volume is much larger than a car, so you’d need more efficient heat exchangers. We know that they can make it work with propane burners in the Breitling Orbiter, but that’s different than using engine heat. It may very well be that it heats up so slowly that the heat dissipates before it accomplishes anything meaningful.

Since we don’t know what the thermal characteristics of the envelope are, don’t know what kind of heat exchange and circulation we’re using, and only guessing at the thermal output of the engines (which burn a different kind of fuel,) we are still at the WAG stage.

I guess the first place to start is to take our BTU/hr. Figure and see how fast that would heat up the volume of helium. If that number comes back promising, we start chopping it down with things like heat loss, circulation, etc.

282

If you want to heat an entire balloon, then you make the balloon a teardrop shape. If your balloon isn’t a teardrop shape, then you’ll mostly just be heating up a teardrop-shaped section on the inside. Mostly, but there will still be some heat transfer to the rest. Putting a teardrop-shaped balloon inside your main balloon will just eliminate some of that transfer. The interior of the inner balloon will heat up just fine, but that doesn’t matter, because you want to heat up all of it.

283

Gotcha. The Orbiter was hot air and helium, hence the balloon within the balloon. The blimp is just helium. A second envelope foes nothing to help.

284

Article on vacuum airships in the Christmas edition of New Scientist (An English popular science magazine)

There’s a research student working at MIT who calculates that with current materials the shell needs to be about 10% of the radius. One of the solutions canvased is to rise as a hot-air balloon, then switch to vacuum (and turn off the heaters).

The article also suggests that people might like the idea of floating around under a balloon :). If people can’t handle the idea of traveling in a 737Max, I can’t see how the idea of traveling in an airship (with a much worse safety record) would ever be commercially viable.

285

A new proposal:

The H2 Clipper would carry payloads up to and beyond 340,000 lb (150,000 kg), says the company, and would offer up to 265,000 cubic feet (7,530 cubic metres) of cargo space. It wouldn’t travel as fast as a plane, cruising at about 175 mph (282 km/h), but it would move boxes some 7-10 times faster than a boat (China to the US in 36 hours, for example) and with zero emissions.

286

A good point made by an interviewee in that article:

  • Banning flammable substances from use generating aerostatic lift, but allowing them for use generating forward thrust, is absurd. Flammable fuel leaks have caused numerous aviation disasters without these substances being banned wholesale.

It seems quite plausible that modern engineering could make these safe.

287

I wonder if double-bagging would make a hot air airship more efficient. One downside to hot air balloons is heat transfer from the hot balloon to the outside air. Put an air chamber between them to reduce heat transfer.

Fusion might be a usable technology to power a hot air blimp or airship. there’s just one teeny obstacle for now…

Don’t have time to (re)read the the whole thread, but fun Hindenburg fact - the problem with the Hindenburg (and may winged aircraft of the time) was the skin was doped fabric and highly flammable. The tragedy was more due to static electricity igniting the envelope than because of hydrogen. Hydrogen just added to the spectacle.

288

Here’s a link and a bump:
Research into secret advanced technology that could explain some UFO/UAP (DEEP DIVE) : SpecialAccess

The author goes on …for some time… and I didn’t read much of it but seems interesting.

I’ve covered this topic before when speculating how observations such as the cube in a sphere UAP or even the balloon like UAP apparently observed during the shoot downs could potentially be advanced forms of vacuum balloon technology. I had found a** 2018 patent **from LANL under contract with the DOE to develop such technology using alleged breakthroughs in aerogel technology. I have also discovered numerous USAF reports on “vacuum lighter than air structures” or VLTAS.

289

Nutcase has a hammer, sees a lot of nails. There’s no reason whatsoever that a vacuum airship should be cubical. Even if someone did come up with a miracle material that made it possible, it’d still be a sphere.

290

Still, the achille’s heel of airships is how vulnerable they are to bad weather. So many of the airships in the heyday of Zepplins crashed in bad weather - winds, lightning, heavy rain (what’s the weight of all the water running off the acre of airship?)

I would imaging a vaccum airship would be a strong frame holding a covering against air pressure, so the skin would bulge inward from the frame. Aerogel if light enough might be a candidate frame.

291

There is no ‘frame’ that’s going to allow for a vacuum airship. The force on the thing would be insane. A 2 PSI differential can crush a railroad tanker car. Something light enough to float and strong enough to maintain a vacuum across a huge volume would have to be made of unobtanium, or it would buckle at the first imperfection in the surface.

Here’s an interesting balloon design, an airship-to-orbit proposal:

Imagine a gigantic balloon slowly floating up high into the stratosphere (200,000 ft). At a certain altitude, the balloon no longer has excess bouyancy, and stops climbing, However, the balloon is designed with lifting surfaces. When you stop climbing from bouyancy, you fire up some engines, and start moving forwards. The combination of bouyancy and lift from the few molecules left at that altitude causes you to climb. As the pressure gets lower, you accelerate faster. Eventually, you reach orbit. But you do so slowly and gently over days or weeks.

To come down, you reverse the process. Retro-fire in orbit, start a very slow descent. As you hit air molecules, you get some lift, so you slow down more. Eventually, you transition from orbital speeds to speeds in which you are mostly floating. Then you just come down like a balloon. No re-entry heating, no extra G forces.

The balloon would be huge - six kilometers across. It could hever land on Earth as it would be torn apart by the lower atmosphere. So you have a large floating balloon station at 140,000 ft, and the giant orbital balloon only travels between the station and orbit.

As a bonus, this would prove out the tech ologies needed for an orbital floating station on Venus.

Lots of technical challenges, but nothing like a vacuum balloon. But the concept is probably dead because Starship will almost certainly beat it on cost to orbit.

292

The “frame” wouldn’t be a frame; it’d be the entire envelope. Any other design is just introducing weaknesses for no reason. If you did have some magically-strong material sufficient to make a frame that you could stretch a membrane over, you could make an even better airship (more lift for less material, and more margin to withstand catastrophe) if you replaced the entire membrane with that material.

293

This thread is almost 7 years old. Most of the usual suspects now chiming in (myself certainly included) litigated the heck out of the structural issues the first time. Which went around a lot of times before the OP finally lost patience with not getting his preconceived answer reinforced.

I’m not objecting to us having a fresh go-around now. Just pointing out we might look at what we wrote last time & save a few bits. Or at least refer back to those excellent posts of yesteryear.

294

Oh yes, I’m well aware a “vaccum balloon” frame would have to be more than insanely strong and light, not even considering the envelope. I was just pointing out the geometry that would result.

295

Yes, that would be the geometry that would result, if you were silly enough to build it with a frame.

296

I was wondering how they are doing a year and a half later. Their plans are:

2023 Prototype Design Completion
2024 Prototype Build begins
2026 Prototype First Flight
2029 Commercial Operation