"Rigid airship" using low density hydrogen (LDH) inflation

[KingoftheChaosEmpire]

TL;DR Summary

New idea for inflating airship with LDH(at most 30%hydrogen)
What is the formula for finding out the minimum shell compressive strength?
Beyond possible, is LDH "inflation" for a large airship practical? What would be limitations or things to consider?
Would making regular machined parts out of LDH honeycomb be possible&practical? If so, it could be revolutionary.

I know now that making a full on vacuum airship is unfeasible for it's compressive properties. So why not just make a rigid airship that is evacuated enough that the hydrogen is no longer significantly dangerous to it's surroundings, using say 25-30% density of neutral hydrogen? What's the weakest compressive material I could use for that?
Could I, in practice make any rigid part out of a honeycomb-like structure of LDH-cells? This could be revolutionary in creating lighter weight rigid parts provided volume isn't too sensitive and lighter weight is an advantage. And of course, individual parts can be made out of their own honeycomb, with variation in shape, dimensions, hydrogen densities and what not depending on their allowances and needs.

Can someone give me a formula(and tell me all the dependent/constant variables) to get real values on this and fact out the feasibility myself? Thanks.

 

[DaveC426913]

Years back I explored this a little (mostly by asking here on PF).

What I learned was that the puny gain between H and He is just not worth it.I stole this from Google:

"...the buoyant force for one m³ of helium in air at sea level is: 1 m³ × 1.114 kg/m3 × 9.8 N/kg= 10.9 N. Thus hydrogen's additional buoyancy compared to helium is: 11.8 / 10.9 ≈ 1.08, or approximately 8.0%..."

It's a lousy reference but it will give you a start in the right direction.

 

[russ_watters]

Summary: New idea for inflating airship with LDH(at most 30%hydrogen)

What does LDH stand for? 30% of what? Are you saying 30% of atmospheric pressure, pure hydrogen?

Beyond possible, is LDH "inflation" for a large airship practical?

It's easy enough to calculate the weight savings from reducing the amount of hydrogen. See how much it is.

evacuated enough that the hydrogen is no longer significantly dangerous to it's surroundings, using say 25-30% density of neutral hydrogen?

You sure that's a thing? I don't think it is.

Anyway, there is no simple formula for the weight of the structure. You'd have to design it or compare to existing structures.

 

[Baluncore]

Welcome to PF.

I know now that making a full on vacuum airship is unfeasible for it's compressive properties. So why not just make a rigid airship that is evacuated enough that the hydrogen is no longer significantly dangerous to it's surroundings, using say 25-30% density of neutral hydrogen? What's the weakest compressive material I could use for that?

1. Design and implementation will depend on the specification of operating altitude and ceiling. The maximum differential envelope pressure will only need to be about 1 psi, with internal gas pressure adjusted with altitude.

2. The compressive structure will not be a tubular honeycomb, but will be a two layer, 3D space-frame, like an octet truss. The structure will be approximately spherical, made from connected rigid subsections, (gores), like a soccer ball.

3. The small patches of envelope membrane will not be flat like a drum, but will bulge inwards, so tension in the surface membrane does not add so much to the hoop compression in the rigid structure.

https://www.physicsforums.com/threads/vacuum-airships-would-multi-skinning-work.994352/

 

[KingoftheChaosEmpire]

Years back I explored this a little (mostly by asking here on PF).

What did you explore? What is "this" and where are those questions on PF? Do share this as much as possible please and get this to people who have similar interests/ related experience.
I guess you have to make a new quote to respond to new comments.

 

[DaveC426913]

What did you explore? What is "this" and where are those questions on PF? Do share this as much as possible please and get this to people who have similar interests/ related experience.

The concept of hydrogen filled or vacuum filled dirigible as a practical alternative to He.

I'm afraid I didn't turn up the old thread. Must have been too long ago.

Anyway, the upshot was essentially what i posted above. The gain in buoyancy is paltry.

 

[KingoftheChaosEmpire]

Design and implementation will depend on the specification of operating altitude and ceiling.

@Baluncore thanks for responding. I appreciate that you gave some procedures. Ok so I wanted to respond but the problem is I have a slow brain and it takes years for me to make a response, so instead of trying to make a singular response at a time to a person, I'm just going to acknowledge people's statements, but send my response when I finish making them in my notes. So yeah, thanks and please do share
But on an immediate note, if your saying that making a hexagonal skeleton with skin on top is the most effective low pressure design, then that's awesome. See you.

 

[KingoftheChaosEmpire]

Welcome to PF.1. Design and implementation will depend on the specification of operating altitude and ceiling. The maximum differential envelope pressure will only need to be about 1 psi, with internal gas pressure adjusted with altitude.

2. The compressive structure will not be a tubular honeycomb, but will be a two layer, 3D space-frame, like an octet truss. The structure will be approximately spherical, made from connected rigid subsections, (gores), like a soccer ball.

3. The small patches of envelope membrane will not be flat like a drum, but will bulge inwards, so tension in the surface membrane does not add so much to the hoop compression in the rigid structure.

https://www.physicsforums.com/threads/vacuum-airships-would-multi-skinning-work.994352/

Thanks for welcoming me. Again, I have no idea why it copied your entire comment but here goes.

Quotes are difficult to use so instead I'm just going to be copying and pasting texts:"Design and implementation will depend on the specification of operating altitude and ceiling."

Well I haven't figured out exactly. As much as possible, really. I don't see anything bad about that. The limiter here is how light the structure can be made.
*Since I made this comment my thoughts have completely changed on this, I don't even want a vacuum airship anymore, I would rather just have hydrogen-based inflation, with the hydrogen evacuated in an inflatable skin only enough that it's danger is greatly reduced, since in a puncture air will seep in, rather than the hydrogen bursting out. At the same time the airship no longer has to deal with hydrogen leakage, a significant bonus. With this idea one can return to using large airships and even the Zeppelin military ship without making significant changes to them, besides reducing the weight by kiloliters of hydrogen and a heavy aluminum shell.

 

[Baluncore]

I have no idea why it copied your entire comment but here goes.
Quotes are difficult to use so instead I'm just going to be copying and pasting texts:

Highlight the part of the post you wish to quote, then to have it inserted into the reply window, click to select the 'quote' or 'reply' tab that appears.
You can switch BB display mode by clicking on [ ] in the toolbar.

The limiter here is how light the structure can be made.

Yes. But the structural implementation is dependent on the maximum differential pressure that must be opposed or countered by the structure, which is limited by the ceiling, where the balloon will have a perfect internal vacuum. First, specify the ceiling, then everything will follow. The balloon will become buoyant at sea level once that differential pressure is achieved. As air is removed, the balloon will rise, maintaining a similar differential pressure.

I would rather just have hydrogen-based inflation, with the hydrogen evacuated in an inflatable skin only enough that it's danger is greatly reduced, since in a puncture air will seep in, rather than the hydrogen bursting out.

A double envelope will increase the weight of the carcass. Avoid the oxygen in air by filling the outer envelope with nitrogen. Avoid high pressures in the nitrogen, since pressure increases density.

 

[KingoftheChaosEmpire]

Dang, I'm at the library right now, and I wish I could have logged in and continued replying on computer, but the site has log in issues, telling me to message an admin or something. I guess I'll just continue replying on the phone.

I see not only are you well versed on this topic, but you have already seen and thoroughly thought out this very thing I was trying to explain. Well, you didn't answer the structural balloon part, but the post you've linked shows you've already answered my question on it. I feel bad for clogging up the space now but more people need to be talking about this, so it's easier for parties to find.

Since you know so much about it, is it cool if I ask you where you got your information? Did you read/do you know of any books or manuals that explains the basics of this? Something like that is what I'm looking for. Thanks for replying.

 

[phinds]

Quotes are difficult to use

No, quotes are trivial to use and if you're going to be a member here you need to learn how to use them. See post #9 for a start.

 

[jrmichler]

Did you read/do you know of any books or manuals that explains the basics of this? Something like that is what I'm looking for.

It's all basic physics and engineering.

Physics: Force on the skin = pressure X area.

Engineering (see Post #48 in https://www.physicsforums.com/threads/vacuum-airships-would-multi-skinning-work.994352/page-2): Start with the calculations for thin walled pressure vessels, recognizing that vacuum vessels use the same equations as pressure vessels.

Then you decide what you want it to do. If you want it to move, you need to provide a force to move it. That force is typically provided by an engine and propeller. The engine needs an engine mount, fuel, and operator controls. If you want to steer it, you need a means to control the direction. If you want it to hold together after it starts to move, you need to study aerodynamics (one book), after which you study aircraft structures (a different book). If you want carry people and/or cargo, you need at least a floor. If you want to know where it is, you need navigation equipment. If you to fly it legally, you need FAA registration, required instruments, a transponder, and a pilot license. If you want to park it, you need a mast, ground handling equipment, and a hangar. It you want it to work for more than a day or so, you need maintenance supplies and FAA licensed mechanic(s).

Could I, in practice make any rigid part out of a honeycomb-like structure of LDH-cells?

Sure you can. But first, refer to the post linked above, then study the mechanical properties of these materials. Then do the calculations to find the minimum mass of material that will handle the load. Don't forget the necessary safety factor.

There is no one book that tells you everything you need to know. You need a full bookshelf. The required knowledge is approximately a BS degree in aeronautical engineering, plus a year or so of study for items specific to your proposed airship and the required pilot license.

 

[Baluncore]

Since you know so much about it, is it cool if I ask you where you got your information? Did you read/do you know of any books or manuals that explains the basics of this? Something like that is what I'm looking for.

There is no recipe, just be open and different. You need to maintain a wide interest in technology, for a significant period of time.

Since no reduced-pressure air-balloon has yet arisen, the search for a solution must be based on a thorough understanding of first principles. Until then, hot-air and lighter-than-air gas mixtures will be enveloped by surface tension.

Some things can be proven mathematically impossible. Those who say something is impossible, but cannot prove it impossible, close their mind and give up on the search for a technological solution. They are a hindrance, let them go. Keep an open mind.

Vacuum balloons are a complex problem that may be solved only when sufficient ideas converge in the solution space of one experimenter's mind. Those who can keep the possibilities open and being discussed, are part of a community that is gradually creeping toward the many possible technological solutions.

 

[KingoftheChaosEmpire]

It's all basic physics and engineering.

Physics: Force on the skin = pressure X area.

Engineering (see Post #48 in https://www.physicsforums.com/threads/vacuum-airships-would-multi-skinning-work.994352/page-2): Start with the calculations for thin walled pressure vessels, recognizing that vacuum vessels use the same equations as pressure vessels.

Then you decide what you want it to do. If you want it to move, you need to provide a force to move it. That force is typically provided by an engine and propeller. The engine needs an engine mount, fuel, and operator controls. If you want to steer it, you need a means to control the direction. If you want it to hold together after it starts to move, you need to study aerodynamics (one book), after which you study aircraft structures (a different book). If you want carry people and/or cargo, you need at least a floor. If you want to know where it is, you need navigation equipment. If you to fly it legally, you need FAA registration, required instruments, a transponder, and a pilot license. If you want to park it, you need a mast, ground handling equipment, and a hangar. It you want it to work for more than a day or so, you need maintenance supplies and FAA licensed mechanic(s). Sure you can. But first, refer to the post linked above, then study the mechanical properties of these materials. Then do the calculations to find the minimum mass of material that will handle the load. Don't forget the necessary safety factor.

There is no one book that tells you everything you need to know. You need a full bookshelf. The required knowledge is approximately a BS degree in aeronautical engineering, plus a year or so of study for items specific to your proposed airship and the required pilot license.

It sounds like you're telling me I can only work my way up to learning how airships work. Well that's what I've been trying to do. I have an angle I want to learn from but nonetheless I'm trying to gain a better understanding of specifically the airship in order to improve upon it. I was just trying to cut the way and ask beforehand the practicality of my implements before I know enough to work it out myself. But thanks for any direction you can give me.

 

[russ_watters]

I recommend starting with a basic calculation of the lift available from an assumed size airship filled with helium, hydrogen and partial vacuum hydrogen. Or from the other direction, how big each would need to be to lift a given weight. That will tell you what your structure needs to weigh to be worth doing.

 

[sophiecentaur]

What I learned was that the puny gain between H and He is just not worth it.

Except the cost difference is high and the leakage with He could be a problem.

 

[sophiecentaur]

Something that really worries me is how stable an evacuated envelope would be against buffeting. The great thing about a ‘blown up balloon’ is that the whole design is so forgiving.
But that reaction would pooh pooh an idea like a rocket booster that returns - nice as pie - to where it started. So whada I know?
One day ?

 

[KingoftheChaosEmpire]

Seems like everything was mass deleted when I deleted my 1 comment. I'm done with this forum. This forum's controls sucks, it's not trivial it's difficult as hell, and you guys need to fix your difficult broken forum's before anyone new can join on. The controls for replying are terrible, the way the threads are made is terrible, how do you even make a new thread, I'm tired of going through a complicated process every time I want to do something that I could do basically in a YT comment section, maybe whoever designed that **** controls should look to them next time they want to make a forum. Trash forum. See y'all.

 

[sophiecentaur]

Trash forum. See y'all.

Toys out of pram! Well well well.

 

[DaveC426913]

If a thing is worth doing, it is worth the learning curve involved.

 

[Bystander]

Seems like everything was mass deleted when I deleted my 1 comment. I'm done with this forum.

"Don't let the door..."

 

[Baluncore]

@ KingoftheChaosEmpire
When you claimed to be unable to open a new topic, the topic was split by a moderator for you. You now have two topics:
1. "Rigid airship" using low density hydrogen (LDH) inflation
2. My balloon technology (the LDH honeycomb)

Seems like everything was mass deleted when I deleted my 1 comment. I'm done with this forum.

A coincidence.
Your other posts were not deleted, they were moved to the new topic. Participants were notified in “alerts” when their posts were moved to the new topic, but you ignored the alert, probably because it was off-screen on your mobile.

As “KingoftheChaosEmpire” you thought you could access the forum through a mobile phone, but then got confused and replied to a post by editing inside a quote. Maybe you toggled BB mode with [], which I guess could get confusing on a mobile.

Don't blame the forum for the small screen on your mobile phone.

 

[Baluncore]

... The controls for replying are terrible, the way the threads are made is terrible, how do you even make a new thread, I'm tired ...

To make a new thread.
Go to the main forum menu; Scroll down "Forums" to "Engineering"; then to the "Materials and Chemical Engineering" Forum;
Click on the "Post Thread" button to open a new topic in that forum.

Ok so I don't know how to post a new thread so I'll post my question here:

That post is at the start of your other thread. Follow the link.

 

[Drakkith]

This forum's controls sucks, it's not trivial it's difficult as hell, and you guys need to fix your difficult broken forum's before anyone new can join on.

Well this is new. We get new members all the time and in my 10+ years here at PF, including my time spent as a moderator of the forum, I can't recall even a single person complaining that the forum controls were too hard to use.

The controls for replying are terrible, the way the threads are made is terrible, how do you even make a new thread, I'm tired of going through a complicated process every time I want to do something that I could do basically in a YT comment section, maybe whoever designed that sht controls should look to them next time they want to make a forum.

I'm sorry this was too complicated for you. I can't remember what software PF runs on, but I know that the forum controls and features are similar to almost every other forum I've ever been a part of, so you can think of them as 'standard issue' for webforums (note that forums are very different from things like discord or the comments section of youtube or facebook). If you're unwilling to spend even a small amount of time learning the controls for a forum where people are willing and able to assist you (even if the assistance isn't what you expected) then I question your ability to accomplish your goal.

Trash forum. See y'all.

Have a nice day.

 

[berkeman]

Thread closed for Moderation until we can figure out if part of it needs to be split off into the Feedback forum.

 

[fresh_42]

For all who wonder about this off-topic rant at the end of a thread:

Here is the link to the alleged "deleted" thread:
https://www.physicsforums.com/threads/my-balloon-technology-the-ldh-honeycomb.1047208/

... I mean, the OP could have simply asked, or read his messages. Just saying.