Author Topic: New Airship Designs  (Read 27485 times)

Offline Arch Admiral

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Re: New Airship Designs
« Reply #40 on: 06/03/2017 06:20 am »
Other commentators have demolished the airship as a space launcher, so I will address it as a cargo carrier. The pre-1935 helium airship failed for many reasons that are inherent in the technology:

-- the Earth's atmosphere is too thin. Even at sea level the lift from helium, hydrogen, or even pure vacuum requires an enormous volume to lift any significant weight.

-- the air density falls off too rapidly with altitude. An airplane just flies faster in thin air to get the same lift, but the airship loses lift directly with outside pressure. The USN scouting airships had trouble crossing the continental divide in New Mexico, and were limited to about 6000' in simulated combat.

-- the air density varies too much with time. Temperature and humidity changes were not followed by the lifting gas so it was a constant struggle to maintain neutral buoyancy. When helium replaced hydrogen this problem got worse because helium was too expensive to vent. Also, the airship gets lighter in flight due to fuel consumption so you have to condense ballast water from the engine exhaust or scoop it up from the ocean.

-- the winds are too high. Wind speed is a significant fraction of cruising speed and an unexpected wind shift can run you out of fuel.

-- the air is too turbulent. As airships got bigger to enjoy economies of scale, their lengths got close to the scale of updrafts and downdrafts in storms. By the 1930s they were getting broken in half. As low-altitude aircraft, they couldn't fly very far without encountering a weather front.

-- ground handling is very difficult in anything but a flat calm and hangar space is needed for every ship in storm conditions. The expense of building a new hangar bankrupted Cargolifter (if it wasn't an investment scam from the start).

These new airship proposals usually ignore most of these problems or propose cures that are worse than the problem, like blending in elements of HTA aircraft or helicopters. LTA is a technology that might work on a planet with a thicker and calmer atmosphere than Earth's.

Offline hkultala

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Re: New Airship Designs
« Reply #41 on: 06/03/2017 06:57 am »
Other commentators have demolished the airship as a space launcher, so I will address it as a cargo carrier. The pre-1935 helium airship failed for many reasons that are inherent in the technology:

-- the Earth's atmosphere is too thin. Even at sea level the lift from helium, hydrogen, or even pure vacuum requires an enormous volume to lift any significant weight.

Enourmous volume is not really a problem if it still is not too expensive.

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-- the air density falls off too rapidly with altitude. An airplane just flies faster in thin air to get the same lift, but the airship loses lift directly with outside pressure. The USN scouting airships had trouble crossing the continental divide in New Mexico, and were limited to about 6000' in simulated combat.

For a cargo airship travelling on anywhere else than mountainous area, there is no need to go high. I don't see this as a problem.

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-- the air density varies too much with time. Temperature and humidity changes were not followed by the lifting gas so it was a constant struggle to maintain neutral buoyancy. When helium replaced hydrogen this problem got worse because helium was too expensive to vent. Also, the airship gets lighter in flight due to fuel consumption so you have to condense ballast water from the engine exhaust or scoop it up from the ocean.

This static-lift difference can be solved by pumping gas between highly pressurized container and the main low-pressure airbags. When the airbag is deflated and the helium is in the high-pressure tank, external air takes that volume and the ship is heavier. When the airbag is inflated the external air is pushed out.

So no need to use any ballast or vent out helium.

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-- the winds are too high. Wind speed is a significant fraction of cruising speed and an unexpected wind shift can run you out of fuel.

This can also used as advantage; Design the flight routes so that you are travelling WITH the wind, not against it.

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-- the air is too turbulent. As airships got bigger to enjoy economies of scale, their lengths got close to the scale of updrafts and downdrafts in storms. By the 1930s they were getting broken in half. As low-altitude aircraft, they couldn't fly very far without encountering a weather front.

Modern kevlar, carbon-fiber, titanium and Al-Li construction materials are much stronger than anything 85 years ago.

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These new airship proposals usually ignore most of these problems or propose cures that are worse than the problem, like blending in elements of HTA aircraft or helicopters. LTA is a technology that might work on a planet with a thicker and calmer atmosphere than Earth's.

No, they do not.

The static-lift problem is solved at least in Aeroscraft.


And I think you are missing the two most important reasons:

1) Cheapness of oil making aeroplane travel cheaper.

But now there is huge environmental pressure to reduce oil usage, making aeroplanes non-desired.

2) People got scared of travelling in airships due hydrogen-related accidents.

This is not a problem for cargo use, AND now enough generations have passed that this scare is gone.
Though for modern people, airships are too low. We want everything immediately.

Offline Hanelyp

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Re: New Airship Designs
« Reply #42 on: 06/04/2017 02:58 am »
...
Quote
-- the air density varies too much with time. Temperature and humidity changes were not followed by the lifting gas so it was a constant struggle to maintain neutral buoyancy. When helium replaced hydrogen this problem got worse because helium was too expensive to vent. Also, the airship gets lighter in flight due to fuel consumption so you have to condense ballast water from the engine exhaust or scoop it up from the ocean.

This static-lift difference can be solved by pumping gas between highly pressurized container and the main low-pressure airbags. When the airbag is deflated and the helium is in the high-pressure tank, external air takes that volume and the ship is heavier. When the airbag is inflated the external air is pushed out.

So no need to use any ballast or vent out helium.
I like ammonia as a trim fluid.  At atmospheric pressure it's a lifting gas, even if not a great one.  At manageable pressure it condenses to a supercritical fluid that would function as ballast.
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-- the winds are too high. Wind speed is a significant fraction of cruising speed and an unexpected wind shift can run you out of fuel.

This can also used as advantage; Design the flight routes so that you are travelling WITH the wind, not against it.
This was done a lot in the age of sail.  Ships crossing the Atlantic would travel East at one latitude then West at another, finding prevailing winds to their favor going both ways.  To better take advantage of such routes, the circuit would make multiple stops on at least one side of the ocean.  We also have much better weather reporting than before the age of satellites, allowing adverse weather to be more easily avoided.

Offline sanman

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Re: New Airship Designs
« Reply #43 on: 06/10/2017 11:33 am »
Interesting news continues in this area.  It seems Google's Co-founder Sergey Brin is building the world's largest airship at NASA's Moffett Field: http://www.popularmechanics.com/flight/a26670/more-details-sergey-brin-airship/.  Listed uses include humanitarian relief and also doubling as a luxury air yacht.  If reusable rockets really get going, I suspect we might see an airship built that could accommodate them inside as well.  Brin's design got its start via help from Igor Pasternak, who NSF members may remember as the founder & designer of Aeroscraft.  Thus Brin's design features variable buoyancy and even active buoyancy management.

Gee, if Brin can fund something like this, I wonder why others like Jeff Bezos shouldn't also see merit in this, because of the ability to ferry rocket stages. But I guess when your factory is near to your launchpad, you don't care so much. Paul Allen could probably use his Stratolaunch aircraft for ferrying stages. But maybe ULA could make use of airships - perhaps ones made by parent Lockheed?

Online catdlr

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Re: New Airship Designs
« Reply #44 on: 11/18/2017 12:08 pm »
HAV Airlander 10 crash, 18 November 2017

SciNews
Published on Nov 18, 2017



Hybrid Air Vehicles Airlander 10 performed a successful test flight on 17 November 2017, at Cardington Airfield, Bedfordshire. On 18 November, Airlander becomes loose from its mooring and collapsed into a hedgerow. Unconfirmed reports of one person suffering minor injuries.

https://www.youtube.com/watch?v=JtGpg680vQw?t=001

« Last Edit: 11/18/2017 12:08 pm by catdlr »
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Offline Aussie_Space_Nut

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Re: New Airship Designs
« Reply #45 on: 11/18/2017 11:01 pm »
Very disappointing.

Became loose. There is a story waiting to be told.  :(

Offline nacnud

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Re: New Airship Designs
« Reply #46 on: 11/18/2017 11:05 pm »
From the bbc

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The world's longest aircraft has collapsed to the ground less than 24 hours after a successful test flight.

The Airlander 10 - a combination of a plane and an airship - was seen to "break in two" at an airfield in Bedfordshire, an eyewitness said.
Owner Hybrid Air Vehicles Ltd said it appeared the Airlander broke free from its mooring mast, triggering a safety system which deflates the aircraft.

Hopefully it's not as bad as it looks.
« Last Edit: 11/18/2017 11:05 pm by nacnud »

Offline sanman

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Re: New Airship Designs
« Reply #47 on: 11/22/2017 05:08 pm »
Btw, Russia seems to have their own version of the platform, called Atlant - complete with variable buoyancy technology:

http://rosaerosystems.com/atlant/obj858






Offline Arch Admiral

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Re: New Airship Designs
« Reply #48 on: 11/24/2017 04:21 am »
Like I said before, "ground handling is very difficult in anything but a flat calm". In the 1920s the USN developed massive mooring towers, tail carts, circular railroad tracks, and diesel locomotives to keep their airships rigidly controlled on the ground. None of this stuff was installed at Cardington during the R100/R101 program and the Airlander people thought they could get away with a tiny tracked vehicle that doesn't look big enough to handle an advertising blimp. Airlander 10 has wrecked itself twice in two years and these people need to stop the project right now while they are still all alive.

Offline Star One

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Re: New Airship Designs
« Reply #49 on: 11/24/2017 07:56 am »
From the bbc

Quote
The world's longest aircraft has collapsed to the ground less than 24 hours after a successful test flight.

The Airlander 10 - a combination of a plane and an airship - was seen to "break in two" at an airfield in Bedfordshire, an eyewitness said.
Owner Hybrid Air Vehicles Ltd said it appeared the Airlander broke free from its mooring mast, triggering a safety system which deflates the aircraft.

Hopefully it's not as bad as it looks.

Second crash in just over a year, sounds like the scepticism about this project is well deserved.

Offline Vahe231991

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