# ProjectHybrid airship

#### boogabooga

##### Bug Crusher
Could you please explain how PAYLOAD and BALLAST scenario parameters are being used to size the airship, or why PAYLOAD does not get added to the total mass?

Also, I saw a condition in which the lifting gas had lower pressure than the atmosphere. That shouldn't happen on earth with a helium airship.

#### markp

##### Member
The airship is sized so the airship has neutral buoyancy and zero ballonet volume at its pressure ceiling altitude. Ballast and payload mass from the scenario are used for this calculation. Payload mass isn't added to the actual airship because I've assumed the payload will be something attached via the docking port.

Yes the gauge pressure goes negative but it's not supposed to. I'll fix that.

Thanks for testing it.

#### markp

##### Member
I think I've figured our how to deliver the airship to different places in the Solar System and make it fun. The basic idea is that the airship is delivered in cargo boxes and then assembled at the destination with the press of a key.

However for the airship to assemble itself the correctly, i.e. spawn the vehicle, the correct number of cargo boxes required will need to be delivered. The number of boxes will depend on the assembled mass of the airship. A large airship requiring more boxes than a smaller airship. The boxes will also have to be placed in close vicinity to each other for the airship to assemble itself.

I will use my DRM 1 cargo lander to test out the idea. I think it might be quite fun as some precision landing may be required if more than one lander has to be used to deliver the cargo boxes.

#### Urwumpe

##### Not funny anymore
Donator
Could your code also work for simulating a vacuum airship on Mars?

#### markp

##### Member
Could your code also work for simulating a vacuum airship on Mars?

I don't see why not. A basic approach could be to set the lifting gas mass and the structural masses could be set from the scenario file. Then by setting the lifting gas mass to zero you could have a vacuum airship. Mmm I wonder if it's really that easy. I can check if you like.

#### Urwumpe

##### Not funny anymore
Donator
I don't see why not. A basic approach could be to set the lifting gas mass and the structural masses could be set from the scenario file. Then by setting the lifting gas mass to zero you could have a vacuum airship. Mmm I wonder if it's really that easy. I can check if you like.

Would be nice, I still have about 3 hours of work left on my shift before can test it at home.

I suspect a few control functions like venting gas should no longer work. But controlling altitude by ballonets should be the same as for a hybrid.

#### markp

##### Member
So the code is designed to calculate the size the airship mesh and calculate structural masses depending on the pressure ceiling requested in the scenario file. Ballast mass is also used in the calculation.

It's possible to put in a line of code to override the lifting gas mass in the calculation of the total mass.

Code:
  liftgasmass     = 0.0;
airshipmass    = m_structure+envelopemass+liftgasmass+ballgasmass;

The size of the airship would be calculated assuming that the lifting gas is helium though.

#### Urwumpe

##### Not funny anymore
Donator
So the code is designed to calculate the size the airship mesh and calculate structural masses depending on the pressure ceiling requested in the scenario file. Ballast mass is also used in the calculation.

It's possible to put in a line of code to override the lifting gas mass in the calculation of the total mass.

Code:
  liftgasmass     = 0.0;
airshipmass    = m_structure+envelopemass+liftgasmass+ballgasmass;
The size of the airship would be calculated assuming that the lifting gas is helium though.

well - then it should be better to fork it for vacuum with vacuum pumps. The size of the ship should rather depend on payload mass, as far as I understand the physics.

#### markp

##### Member
It's also possible to set the gas density to zero in the initialisation routine that calculates the size of the airship.

Not sure that's any help. Things will become clearer over the next few days I guess.

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#### Urwumpe

##### Not funny anymore
Donator
It's also possible to set the gas density to zero in the initialisation routine that calculates the size of the airship.

Yes, but it shouldn't be zero.... only close to zero. :lol:

#### markp

##### Member
Yes, but it shouldn't be zero.... only close to zero. :lol:

Yes quite.

Setting the gas density to 'zero' seems to work although the ballonet size remains fully inflated as the airship rises because the pressure on the envelope is negative.

Do you have any idea of the equivalent areal density for the envelope of such a vacuum airship on Mars? From terrestrial rigid airships I get around 5-6 kg/m2 for a very crude calculation of an areal density (surface area / structural mass).

Donator

#### markp

##### Member
Yes that looks very interesting, thanks!

There seems to be some numbers from their study on page 37 that might help.

#### Urwumpe

##### Not funny anymore
Donator
Oh yes, did not see them when going over the pages. The deployment also looks interesting there.

#### markp

##### Member
So I get about 0.2 kg/m2 for their areal density which is very good compared to non-rigid airship numbers of 0.35-0.52 kg/m2 quoted on page 5 of a paper available online called, "A methodology for determination of baseline specifications of a non-rigid airship".

#### markp

##### Member
Also working on a cargo container for delivering the airship to different places

Last edited:

#### Urwumpe

##### Not funny anymore
Donator
Also working on a cargo container for delivering the airship to different places

View attachment 16437

Not "Airship inside"? :lol:

If you want to know a real joke: Thieves managed to steal a trailer with a registered hot air balloon near my place. I really wonder where they want to sell it. :lol:

#### markp

##### Member
Not "Airship inside"? :lol:

If you want to know a real joke: Thieves managed to steal a trailer with a registered hot air balloon near my place. I really wonder where they want to sell it. :lol:

That's pretty bizarre.

#### markp

##### Member
OK so now an airship has been delivered to Mars packed up nicely in some cargo containers. Who's going to unpack and assemble it though?

#### markp

##### Member
I now have a version of the airship that can be created in a stored configuration. The properties of the assembled airship can be set during the simulation from a 'master' cargo container. The size of the airship will depend on the amount of extra cargo containers have been delivered nearby.

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