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NeilT

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Airships as a way of changing the way we fly
« on: October 02, 2023, 06:24:47 PM »
I created this thread because we're starting to dominate the Aviation thread and I guess it deserves one of it's own.
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #1 on: October 02, 2023, 07:48:21 PM »
Pumping hydrogen out would make it lighter and thus increase buoyancy. You can not vent because it is at negative pressure to atmosphere. You must pump it.

The ballast system should be separate from the main balloon. Pump air from outside balloon to inside pressurized tank to add weight. Release pressurized air to atmosphere to make lighter.


I get the feeling we are talking about different things.

No you had it right an I had it wrong.

So with a compressed air ballast you can pump the hydrogen from the low pressure lift vessels to retain the pressure balance as the airship rises into lower atmospheric pressure.

However highly compressed air ballast could be released or pumped back in again at any time to manage the overall lift capability and to balance the entire ship.  Using multiple ballast chambers to match the multiple lift chambers would allow quite a bit of control on the trim of the ship to make sure it is always at the correct attitude and to avoid creating harsh navigation situations.

I had thought about this long ago but I didn't refer to the notes I took when talking about this.

You know, of course, that a ship of this kind could gain quite a lot of altitude.  At least until the balance between the lift chambers (outside air pressure 1psi) and the ability of the atmosphere around it to hold the ship up, stabilised.

I would expect the operating altitude to be much higher than the Hindenburg though.  Early airships flew at around 650ft.
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oren

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Re: Airships as a way of changing the way we fly
« Reply #2 on: October 02, 2023, 08:48:30 PM »
These huge airships are like the Solar Roads or the vacuum Hyperloop. Sounds good initially, but fails the practicality test, too many technical hurdles/risks and too few problems that can't be solved with existing solutions.

NeilT

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Re: Airships as a way of changing the way we fly
« Reply #3 on: October 02, 2023, 08:54:24 PM »
I did some additional research about the speed of the Hindenberg and why.  It comes down to each doubling of the power of the engines only produces 40% additional speed and the size and share of the Hindenburg creates the resistance.

That being said, with 6,000 SHP (shaft horsepower), for an engine which weighs 700kg, this gives us significant benefits over 1930's technology.  Also propeller design has improved dramatically.

4 marine diesels used by the Hindenburg could only be driven at 850bhp rather than their max rated 1,300.  This is obvious to any mechanic, the harder you drive these engines the less time they last.  In the 1930's our materials knowledge was poor.  A standard car engine of the day would require a rebuild after 50,000 miles.  Today we expect to get 250,000 miles minimum.

So 8 tonnes of marine diesels would produce a usable 3,400bhp and it drove the Hindenburg at around 75mph.  Around 40 hours to cross the Atlantic on the northern route.  Rather an upgrade on 5 days for the fastest racing liner, but still not as good as the 16 hours provided by the Boeing 314 clipper.

Then again if you wanted  to take the clipper you had to get to the port and from the port at the other end.  So that added quite a few hours when Airships were more conveniently located.

Now let's look at speeds and modern powerplants.

A 6,000 shp turboprop can be had at 700kg in weight.  Twelve of these will weigh 8.4 tonnes and produce 72,000 shp max.

Ignoring propeller design and hull surface design (graphene over canvas and higher deformity strength and low CD coatings), doubling the available cruise hp from 3,400 to 6,800 will bring the speed of the airship up to 105mph.  Doubling again to 13,600hp brings us up to 148 mph and doubling it again to 27,200 hp brings our speed to 208  and doubling again to 54,400 just under 300mph.

At 54,400 hp the turboprops would be running at 75%. This is within standard cruise ability of these engines.  But another 1.4 tonnes of engines would add another 12,000 shp which would bring it well into the 60% bracket.

Let's take a step back and see what this would have cost us on the Hindenburg in the 1930's.  With the engines used, that speed would have required 64 engines.  With a gross weight of 128 tonnes.  Or more than half the gross weight of the entire airship at that time.  For them 300 mph was simply impossible.  They could not get it off the ground.  Power to weight ratio of gas turbines makes things possible that were simply impossible before.  For the weight increase of just one additional Hindenburg engine and some smart engineering to reduce the drag of the engines, suddenly airship speeds move into the same level as fixed wing.

As I write this I'm aware that there are both 10,000 shp turboprops designed for the A400 and a 12,000 shp turboprop designed by the USSR for their Bear military planes.  So I'm being conservative here.

At 300mph that brings the no headwind time to cross the atlantic down to 10 hours.  Just 4 hours over the time it takes a normal jet liner.

Of course tailwinds on such a ship would contribute far higher over ground speed advantages than a jet liner due to the the wind resistance of the structure.

Naturally a headwind would also cause more loss of time.

Here are some other things.   Much of the navigation issues of the early airships were due to their speed and the speed of the winds they had to content with.  If your cruising speed is 75mph and your max speed is 85 mph, when you hit a 60mph wind you are standing still with little ability to manoeuvre.  If, however, your cruising speed is 300 mph and you have significant power in reserve to deal with headwinds, then your ability to manoeuvre is dramatically increased.

Then landing.  Looking at the way we engineer things today compared to even 70 years ago, we see opportunities which were never even considered.

Let us take an example of the Forth road bridge and the new Forth Crossing.

The forth road bridge I have a lot of experience with having driven and ridden motorcycles over in fairly high winds.  Speeds were lowered to 40mph and even 30mph and the bridge was often closed.



Note the lack of any wind protection.

Now let's look at the Queensferry Crossing, only recently opened.



Note the wind protection. 

From their website.

Quote
“Since it opened in 2017, the Queensferry Crossing has never been closed to cars due to high winds, and we’ve only had to divert high-sided vehicles on a handful of occasions.

https://www.theforthbridges.org/news-from-the-forth-bridges/queensferry-crossing-wind-shielding-success/#:~:text=%E2%80%9CSince%20it%20opened%20in%202017,on%20a%20handful%20of%20occasions.

The Forth Road Bridge was opened on Sept 4th 1964.  This is the advance in the way we do engineering between the nearly 60 years since.

Looking at the old pictures of airship "airports", there is no reason why the airship landing jetty cannot be rotating and orientated to the wind.  Also there is no reason why wind shield barriers cannot raise and lower after landing and before take-off.

So I may be nuts and, perhaps airship mad.  But I think that the world as a whole is ignoring a method of transportation which could redefine the way that we travel around the world and also how much we pollute/do not pollute as we do so.

Please feel free to rip any/all of what I've written apart.  I don't do math well so I  have to extrapolate from what I read which has been simplified to the level I can work with.


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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #4 on: October 02, 2023, 09:07:32 PM »
These huge airships are like the Solar Roads or the vacuum Hyperloop. Sounds good initially, but fails the practicality test, too many technical hurdles/risks and too few problems that can't be solved with existing solutions.

I could open a thread on on a transatlantic tunnel using the same tunnelling technology in use today to create the Putgarden/Rødby tunnel.   ;D ;D ;D

If you want fantastic ideas with little chance of ever being seen.  How about maglev propulsion using asynchronous pivoting counterbalancing gyroscopes?

How about a space launch facility to launch people and cargo to interplanetary cyclers using opposed maglev in orbit???  I talked that one through with an astrophysicist who works on space launch.  No problem with the logic, just that it would cost so much in the first place nobody would do it....

I thought this one was actually grounded in real engineering which is actually achievable today.

Everyone who is working on stuff like this today, for instance the Airlander, is tied to their own conclusions and their own bias and the conclusions and bias of their backers.  I got onto their forum and was able to send suggestions that they ditch the turbodiesel engines and go for gas turbines.  As you can see from the shp calculations and weight, it is a total no brainer.  But they are going to "go with that they know".  Probably because it is a lot cheaper to do a few demo vehicles with the diesels but at the cost of crippling themselves for any real series production or real utility.

In order to succeed you have to try.

What you say above is exactly what the space community told Musk.  He was so gutted that they were such a bunch of losers that he decided to form a company which would get to Mars and build a city on Mars.

They laughed at him.  Mostly his hero's.

Who is laughing now.  It's obvious isn't it?  landing a booster is too hard, too expensive and Nobody will pay for it and Nobody will use it.

Obvious isn't it?  Well it was in 2002.

History has a strange way of proving that the impossible was just a lack of imagination and application.
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oren

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Re: Airships as a way of changing the way we fly
« Reply #5 on: October 02, 2023, 09:17:40 PM »
Reusable rockets and a reusable huge spaceship solve something that had no solutions previously (not with the same economics anyway). It wasn't just an engineering excercise (some fail, some succeed) but also a very lucrative market in need of a cheaper solution.
I can't see what airships bring in terms of economics, or by tapping a huge new lucrative market, in the niche between ships and airplanes.

morganism

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Re: Airships as a way of changing the way we fly
« Reply #6 on: October 02, 2023, 09:32:15 PM »
There is also an airship design in Britain, that uses the Dyson fan design, with the hollow center.
I recall it made it easy to turn, and into the wind movement was easier also. Can't remember the drive system

Thing looked like a Q, and may have been named something like that....

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Re: Airships as a way of changing the way we fly
« Reply #7 on: October 02, 2023, 09:34:35 PM »
IDK , there are a LOT of heavy lift designs that have been put forward in the last dozen years...

There is a desire for it in industry. It is a lot more efficient on fuel.
Military has been funding as a surveillance and border security platform.
Seems like a lot of aeronautics studies and designs from lifting bodies and stealth, along with hypervelocity stuff is available for modeling now. Does wind turbine blade design transmit to propeller work?

If you have all that available water on-board, does that make steam punk propulsion realistic?

edit:moved from aviation thread

NeilT

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Re: Airships as a way of changing the way we fly
« Reply #8 on: October 02, 2023, 09:49:31 PM »
I can't see what airships bring in terms of economics, or by tapping a huge new lucrative market, in the niche between ships and airplanes.

Until the wold recognises that aviation the way we are doing it today has to go.

Then we're going to see a rush for solutions and those solutions are not going to be a liner to New York every time you need to physically need to get there.  In fact there are already groups organsing to ban liners and shipping.  Much as they are clueless to where much of their food comes from.

I see airships as a solution to what is coming.  Not a solution to what is now.

Airships in the 1930's were a solution to a problem of ever faster commerce where it could take a week or more to reach your destination.  They were outmoded by another form of transport which promised much faster travel.  But the fuel consumed would also be higher.  At a time when nobody concerned themselves with the CO2 balance of the atmosphere the only real cost was fuel, staff and maintenance.   Now we know better.  Eventually the cost of that speed of travel will be challenged.  Even the shipping.

People today believe that they know everything and that ships can sail around the world under wind power the way that powered vessels do today.  That you can ban flights for all those other things but when you want to fly half way around the world to experience that wonderful winter sun, that a plane will magically be available to you.  Not realising that if you want to go to that holiday in the winter sun, in Bali, that the sailing ship to take you there will take 3 months.  So you'd better plan for 6 months off work and sell your home to get your one week in the sun.

People believe stupid stuff and they forget the reasons why we have idiomatic phrases and expressions like "when your ship comes in".

When reality crashes in I'd prefer that we have something, rather than a few high taxes and using up all our renewables to make fuel for people who are clueless about the world but suckers for slogans.
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John_the_Younger

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Re: Airships as a way of changing the way we fly
« Reply #9 on: October 02, 2023, 09:56:04 PM »
Just to have it included in this new thread (Thanks, Neil!):
Previous posts related to Sceye's airship

May 29, 2021 - Thread: Aviation

June 22, 2021 - Thread: Solar Power from Space? It’s complicated.

October 2, 2023 - Thread: Aviation

Company website: https://www.sceye.com/

Some things I think are interesting about Sceye:
* They are developing a high-altitude platform station (HAPS)
   - that can be geostationary at 65,000 feet (19.8 km)
   - provide multiple services (high speed internet, climate monitoring)
   - helium filled bags

* hull fabric (compared with other's)
   - 5 times stronger relative to weight
   - 1500 times more gas tight
   - UV and ozone resistant

* lithium-sulphur battery
   - Energy density more than 400 Wh/kg (i.e., past the threshold at which airplanes go electric)
   - Nearly 2 times greater energy density than best electric vehicles

* solar cells
   - very light (half the weight of other's) - solar 'cape' covers the platform









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Re: Airships as a way of changing the way we fly
« Reply #10 on: October 02, 2023, 10:14:39 PM »
Quote
I can't see what airships bring in terms of economics, or by tapping a huge new lucrative market, in the niche between ships and airplanes.
Have you seen pictures of trucks delivering wind turbine blades?  As turbines get larger, delivering blades will get more difficult.  An airship (much bigger than what Sceye is developing) will just need to wait for a relatively calm wind to deliver anywhere.  Maybe a niche market, but an awfully useful one!  [OK, in China they have specialty trucks that hold the blade at one end only (blade 'flies' over the edge when truck goes around hairpin turns) and blade lies close to the earth (on back-end truck?) to go under bridges.]

Neven

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Re: Airships as a way of changing the way we fly
« Reply #11 on: October 02, 2023, 10:44:18 PM »
I was really enthusiastic about airships 20 years ago. Just the idea of a big tower with those balloons docking from all sides at different heights...  8)

What are the potential advantages CO2-wise, assuming such a thing could get off the ground, figuratively speaking?
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #12 on: October 02, 2023, 10:59:54 PM »
I was really enthusiastic about airships 20 years ago. Just the idea of a big tower with those balloons docking from all sides at different heights...  8)

What are the potential advantages CO2-wise, assuming such a thing could get off the ground, figuratively speaking?

Neven it does come down to speed.  The faster you go the more fuel you burn.  If it can be used as a  more leisurely mode of travel then the gas does the lifting and the engines only provide thrust.  This can be very efficient especially as fixed wing aircraft have to go fast enough to keep the airflow over the wing to keep them in the air.  When you start talking about hundreds of tons load then airflow for lift is a very big thing.

So with a slower speed and less fuel burned to travel, then less fuel used.  If you use a lot less fuel it becomes more manageable to use either hydrogen or biofuels, created by renewables, for propulsion.

Also there is, as has been mentioned, the potential to cover the outer skin with solar cells.  Perovskite probably.  Which would power a lot of stuff onboard without needing to burn more fuel.

There are some other angles I didn't go into.  Fixed wing aircraft suffer a lot of airframe stress during their lives.  Something an airship could be engineered to avoid.  Especially using advanced materials.  Fixed wing aircraft lifetime is measured in hours and pressurisation cycles.  As they have to fly high and fast to keep fuel efficiency and optimal flying time, their life can be as low as 20 years.  Especially on short hops.

The main advantage I can see here is that if we can mitigate and get over our fear of Hydrogen as a fuel on these ships, we can have a solution which allows us to remove a large portion of current air travel which can be so damaging.  Without an alternate there will be too much resistance to change.

I know, it's a very long shot, but if people don't walk through it and just dismiss it out of hand as too difficult, then it will always remain that hard thing that people can't do.

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Sigmetnow

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Re: Airships as a way of changing the way we fly
« Reply #13 on: October 02, 2023, 11:17:49 PM »
Now let's look at speeds and modern powerplants.

A 6,000 shp turboprop can be had at 700kg in weight. Twelve of these will weigh 8.4 tones and produce 72,000 shp max.

Ignoring propeller design and hull surface design (graphene over canvas and higher deformity strength and low CD coatings), doubling the available cruise hp from 3,400 to 6,800 will bring the speed of the airship up to 105mph.  Doubling again to 13,600hp brings us up to 148 mph and doubling it again to 27,200 hp brings our speed to 208  and doubling again to 54,400 just under 300mph.

This does not take into the account the effects of drag and mass of the huge ships being imagined.  (The 50-ton Airlander is the size of a football field; some posts referenced ships carrying 500 tons and being a mile long.)  Basic physics provides plenty of reasons why freighters do not get up to 300mph, and big airplanes do not carry 500 tons.  If the force of all those engines did not rip apart such a massive airship, turbulence in jet stream winds likely would.

Besides, wasn’t the whole idea of huge airships to get away from using engines that burn lots of fossil fuel? ;)
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #14 on: October 02, 2023, 11:49:36 PM »
Besides, wasn’t the whole idea of huge airships to get away from using engines that burn lots of fossil fuel? ;)

Yes it was. But the example was worked from a discussion I found on the original Hindenburg.... Based on all those factors.

The idea is to have a solution when we're told that we can't just shut down air travel.  That will require more than just one air freight option.
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Re: Airships as a way of changing the way we fly
« Reply #15 on: October 03, 2023, 03:18:09 AM »
I've been thinking for a while now about using airships for static lift, rather than travel. You could remove just the mature/unwanted trees from a tropical rainforest. Or clearing away rubble after an earthquake. Or lifting damaged boats out of the water. Clearing roads or rail tracks after a landslip.  Many other uses come to mind.

I've always assumed that you couldn't get enough lift unless you use mega-sized airships, but from what you people are saying, it's possible. So why aren't people doing it?
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Re: Airships as a way of changing the way we fly
« Reply #16 on: October 03, 2023, 03:02:35 PM »
I've been thinking for a while now about using airships for static lift, rather than travel. You could remove just the mature/unwanted trees from a tropical rainforest.

There are no unwanted trees in the tropical rainforest. It will take care of itself.

For clearing bulk you should be able to shift a lot of load but then you have to lift and load it.

It is just not an alternative for fast and reliable delivery of people or goods. It is not relevant as an alternative on the short to medium term. So it won´t do anything for the CO2 budget which needs some more drastic action on ashorter time frame.
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #17 on: October 03, 2023, 07:06:13 PM »
So why aren't people doing it?

They are restricting themselves to Helium which creates issues.  The 8%difference between helium and hydrogen is a very big issue as you scale.

Then there is the need for very extreme engineering.  This requires a lot of money and there is no clearly defined market for the ships at this time.

Most airships are gas bag types built with late 20th century technology.  High lift airships require much more extreme engineering which requires a lot more money.  Investors want the known because they know that the unknown can come in with astronomical cost.

SpaceX nearly died because they didn't get to space with their first 3 launches.  Simply put Elon didn't have enough money to get the firm to the point where orders would pay for the further development of the business.  Investors weren't willing to put enough money behind SpaceX and Elon funded almost everything out of his own pocket.  The extreme risk 4th launch paid off and NASA came in with an order which allowed the business to produce the Falcon 9.

This is one success story.  History is littered with the alternatives.  Hence no investment money for exactly the kind of engineering required.
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Re: Airships as a way of changing the way we fly
« Reply #18 on: October 04, 2023, 12:53:04 AM »
So why aren't people doing it?

Transporting wind turbine parts to field sites has been suggested as a fitting use for airships.
 
But airships have so many limitations: wind speed, wind direction, adverse weather, landing site requirements…  and need a huge hangar and a ground crew for upkeep.  Their slow speed means they must be stationed near any daily job sites, and they can’t quickly travel long distances.  Helicopters, on the other hand, are faster, more flexible and capable, can work with a ‘crew’ of one or two, don’t require much in the way of ground support except for fuel, and there’s lots of them — so they are the easy choice.
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #19 on: October 04, 2023, 02:19:34 PM »
So why aren't people doing it?

Transporting wind turbine parts to field sites has been suggested as a fitting use for airships.
 
But airships have so many limitations: wind speed, wind direction, adverse weather, landing site requirements…  and need a huge hangar and a ground crew for upkeep.  Their slow speed means they must be stationed near any daily job sites, and they can’t quickly travel long distances.  Helicopters, on the other hand, are faster, more flexible and capable, can work with a ‘crew’ of one or two, don’t require much in the way of ground support except for fuel, and there’s lots of them — so they are the easy choice.

1930's airships this is all true.  Even the Airlander which is based on a concept constrained by many different choices that is also true.

It doesn't need to be true for an airship actually designed for this kind of work.  There is a reason why there is a distinction between rigid airships and inflatable airships.  The design and engineering are totally different.

Also much of the air speed conditions, go away when you use gas turbines to massively ramp the power to weight ratio.  Diesel engines may have increased dramatically in power to weight performance since the 1930's but they are still ridiculously poor compared to a gas turbine.  but they are cheap and very available with low relative maintenance.

If you have more than double the wind speed in real world thrust, you can navigate even in relatively high winds.  Also don't think that normal aircraft don't get grounded by high winds.  If the wind is across the runway then 45mph or more will ground most aircraft.  I've spent a lot of time on the ground stuck because of cross winds.

I theorised that you could build a landing area for a rigid airship which would allow it to dock upwind every time.

I also talked about potential shelters which could be retracted.

Yes it all costs money.  But we are not desperate enough yet.
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #20 on: October 04, 2023, 02:49:09 PM »
Neven asked about advantages and there was one I missed.

Taking Perovskite and 27% solar efficiency, the hull of a Hindenburg airship has a potential generation capacity of 9MW.  Let us say that only half of that is achievable.  4.5MW is 6 million mechanical horsepower.

Sufficient, I would say, to drive at a reasonable speed.  Say 300mph.

Yes there would need to be backup gas turbines for night operations.  So hybrid motors.
Yes there would need to be allowances for poor weather and poor solar performance.
Yes you could add 50t of Li batteries even at 260wh/kg to provide emergency power and balance the panel output.

Going west would be quite feasible as you are following the sun.  10 hours over the atlantic on solar power.  Sounds like a fairy story doesn't it?

A rainbow worth chasing?

And before we start talking about how it has poor characteristics for control at low altitudes, go have a look at how the ISS controls attitude with Gyroscopes.



It is possible to use a much more simplified version of the same conservation of angular momentum to help control attitude of an airship.

Not that this has been used much outside the space arena.  But the principle holds.

Think this is fantasy? Check out the centrifugal force calculator.

https://www.omnicalculator.com/physics/centrifugal-force

10 tonnes with a 2m radius spinning at 10,000rpm has a centrifugal force of 4.9 Billion pounds force.

Something to work with.

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Re: Airships as a way of changing the way we fly
« Reply #21 on: October 05, 2023, 03:37:28 AM »
Quote
Also much of the air speed conditions, go away when you use gas turbines to massively ramp the power to weight ratio.

Show me the thrust puck. ;)  One that doesn’t rip a lightweight airship apart at high thrust and speeds.
 
A ship the size of the Empire State Building will have a massive drag coefficient.

Quote
If you have more than double the wind speed in real world thrust, you can navigate even in relatively high winds.
You’ll just be burning a ton of fuel while pointing in a direction you don’t want to go, to offset the movement of the air that’s carrying the ship.
A huge lighter-than-air ‘craft in a strong crosswind near the ground will be blown sideways uncontrollably.  Crabbing an approach to land using the limit of a huge airship’s rudder authority would require a clear area large enough for a landing from any direction.  (Huge ships don’t turn quickly — it has hundreds of tons of inertia heading in just one direction. — either that, or it’s breaking apart.) Even airliners have crosswind takeoff and landing limits, and they are moving at many times the speed of an airship, and are heavy and strong enough to withstand severe turbulence.
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NeilT

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Re: Airships as a way of changing the way we fly
« Reply #22 on: October 05, 2023, 02:40:24 PM »
You do remember where I found the structural strength to weight of carbon fibre to be 10:1 that of Duralumin? Allowing for a halving of structural weight with a 5x boost in strength?

Or the point where I mentioned that a cylindered structure could function like the structural pack of a Tesla.

Then there is the potential of solar, love someone to cross check those calculations because 27,000 square meters of solar cells will produce more power than any conceivable amount of gas turbines and also electric mothers have the power to weight ratio to drive it.

When trying to land, the biggest problems were the available aileron force to swing the ship and the force of the drive against the wind.

For that read what I posted about centrifugal force and how it is used in the ISS. In space they have to use thrust to avoid saturation.  On earth gravity applies the force and normal aerodynamics too.

This is all feasible. It will require money and dedication but what would that matter for the ability to fly 700 people over the Atlantic in under 20 hours with virtually no emissions?
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Re: Airships as a way of changing the way we fly
« Reply #23 on: October 05, 2023, 03:23:24 PM »
The acceptable operating weather would be more limited than an airplane.

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Re: Airships as a way of changing the way we fly
« Reply #24 on: October 05, 2023, 03:44:23 PM »
I don't know.  For aircraft most issues come with cross winds.  If you can land an airship from any direction you are not tied to a fixed runway.

This is often mitigated by having more than one runway on a different point of the compass.  But if you have spent a lot of time flying out of single runways in areas with strong winds, as I have, you soon come to realise that it does't take a real storm to close the runway to fixed wing.

One pilot explained it to me as the force you can put on the rudder.  Once the wind speed exceeds the force you can put on the rudder, you can't land if it the wind is across the runway.

The large wide bodied planes have the highest force on the rudders.

From my prior readings the largest issues with handling were strong headwinds with a slow forward speed and also conditions which didn't allow a lot of airflow over the rudder and ailerons at the back.  I've discussed how I would approach that.
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Re: Airships as a way of changing the way we fly
« Reply #25 on: October 05, 2023, 06:20:16 PM »
People who say it cannot be done should not interrupt those who are doing it.

NeilT

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Re: Airships as a way of changing the way we fly
« Reply #26 on: October 05, 2023, 07:42:56 PM »
OK so my prior calculations were wrong on the power from the solar cells, but anyway electric would still be more than the original Hindenburg.

Let's take the 4 x 6,000 shp gas turbines.  So max 24,000 shp.

Now your ship, the MSC Opera weighs 65.6 thousand tonnes.  It has a power of 41,000 hp.  That comes out at 1.6hp per tonne.

Now my postulated airship will be 250 tonnes.  Or 285 airships for one cruise ship.  I have 24,000 hp available to me so my hp to tonne is 96.

Oh and remember my gas turbines are running on Hydrogen....

So my airship has 61 times the ability to fight inertia as that cruise ship.
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Re: Airships as a way of changing the way we fly
« Reply #27 on: October 05, 2023, 08:53:15 PM »
Quote
I have 24,000 hp available to me so my hp to tonne is 96.

That’s power to a shaft.  Cool. But the cruise ship has the benefit of braking under/against water.  Against air, your 24,000 hp would tear up the ground under the engines… and then the debris would destroy them.  So, no takeoff or landing with full power.

Consider how long it would take to accelerate 285 tonnes with a huge drag coefficient to operational airspeed.  Hours?  Because lower altitudes mean more drag force, and there’s those pesky accelerational and vibrational forces that want to tear even the strongest ship apart at 100% power. 

Slowing and descending to land from jet levels would require as much (probably more) time and power as the climb. And while overshooting at the jet levels is merely “busting an altitude,” there’s no such luxury when landing.  If there’s a miscalculation or a change in the local conditions at the landing site during the hours of the approach, especially with a super-tough exterior, the penalties for an overshoot/hard landing/litho-braking/crash are severe.   Full power during landing is not appropriate, no matter how strong you imagine your ship is.
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Re: Airships as a way of changing the way we fly
« Reply #28 on: October 05, 2023, 11:36:40 PM »
Quote
I have 24,000 hp available to me so my hp to tonne is 96.

That’s power to a shaft.  Cool. But the cruise ship has the benefit of braking under/against water.  Against air, your 24,000 hp would tear up the ground under the engines… and then the debris would destroy them.  So, no takeoff or landing with full power.
When starship 2 lifts off, we will know if Space X knows how to build a safe take off & landing arena.

I guess that unlike in Hindenburg days, guys with ropes securing the airship as it lands is not an option.

Maybe someone can persuade a high-tech Titan to spend a few hundred million bucks building a Zeppelin sized prototype as a classier way of throwing away the loot than on yet another mega-yacht. After all, with multi-billionaires now ten-a-penny, super-yachts are so, so passé. And what with SpaceX's Model T Falcon turning Space into a mass-travel industry, even the hoi-polloi have a chance for a trip to zero-gravity.

« Last Edit: October 05, 2023, 11:45:36 PM by gerontocrat »
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Re: Airships as a way of changing the way we fly
« Reply #29 on: October 06, 2023, 12:44:03 AM »
Maybe someone can persuade a high-tech Titan to spend a few hundred million bucks building a Zeppelin sized prototype as a classier way of throwing away the loot than on yet another mega-yacht.

Maybe indeed.  Although I guess to answer all my questions and Sigs it would be more like the $10bn set aside for Starship.
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Re: Airships as a way of changing the way we fly
« Reply #30 on: October 06, 2023, 04:11:24 AM »
This is nice if 99% of human population disappear and the remaining 1% decide to behave like teletubbies.

In that world airships can be the greatest means of transport.

In the world of reality, it won’t. Sorry.

An under-100 kt airspeed aircraft will encounter difficulties many days to find a practical route. If we are all teletubbies and don’t mind spending nine flight hours instead of four while we play many teletubbies games, then it’s all fine. Otherwise forget about it.
If the flights are canceled for one week due to wind and atmospheric conditions, teletubbies won’t mind, will be joyful on the grass waiting for the week to pass.
Not to speak about turbulence… but teletubbies have more fun the more turbulence there is.

Do you, Neil?


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Re: Airships as a way of changing the way we fly
« Reply #31 on: October 06, 2023, 12:36:42 PM »
And EV's were golf carts for environmentalists.  It took 30 years, billions of dollars and is going to suck in trillions of dollars in the end.

They are easy by comparison. Then again you could walk or cycle or take the bus instead of using your car.

Row boat over the Atlantic anyone?
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Re: Airships as a way of changing the way we fly
« Reply #32 on: October 06, 2023, 01:55:52 PM »
That’s power to a shaft.  Cool. But the cruise ship has the benefit of braking under/against water.  Against air, your 24,000 hp would tear up the ground under the engines… and then the debris would destroy them.  So, no takeoff or landing with full power.

The airship would come in upwind and then descend vertically over a clear area.  Turbofans on modern jets don't kick up dirt into the engines because they run on runways.  Even then, the air goes out the back and the debris goes out the back.  New air comes in the front.


Quote
Consider how long it would take to accelerate 285 tonnes with a huge drag coefficient to operational airspeed.

Actually the drag calculations are a combination of friction, surface under that friction and the velocity at which the object is moving plus the surface area displacing air up front.  So up to 150mph would be fairly quick.  Yes additional speed to 200mph would take longer and additional fuel/power to maintain.

However if we ban wide bodied jets on non critical journeys over the Atlantic or Pacific, then your acceleration options and journey times are both corrrespondingly slower and longer.

Quote
Slowing and descending to land from jet levels would require as much (probably more) time and power as the climb. And while overshooting at the jet levels is merely “busting an altitude,” there’s no such luxury when landing.  If there’s a miscalculation or a change in the local conditions at the landing site during the hours of the approach, especially with a super-tough exterior, the penalties for an overshoot/hard landing/litho-braking/crash are severe.   Full power during landing is not appropriate, no matter how strong you imagine your ship is.

Actually neither ascent or descent take much more energy than ballast management.

Unlike a jet which requires air pressure to be pretty constant over the wing to provide lift, the difference in pressure for an airship causes far less trouble.  They don't just "fall out of the air".  Totally different dynamic to the lift.

That being said it is about balance and balance needs careful attention and also the ability to alter it quickly.  This means if you are using liquid oxygen as ballast you need to be able to vent it quickly.  Because whilst sudden updrafts are self correcting, sudden down force needs action when close to the surface.

Airships are fairly resistant to pitch issues because they balance around the centre of the lift mass.  Yaw is another thing entirely.

It might be worth reading a journalists writings on a Hindenburg flight.  It answers some of the questions about take off in rough weather and how the power managed in those conditions.

https://www.garemaritime.com/sky-cruise-flight-hindenburg/#google_vignette

It also talks about something I already knew about.  The extremely crude mechanisms used to control the airships and keep them even and on direction.  No radar, radio via morse mainly, humans controlling the vessel, mechanical inclinometers, altitude by either lights or crude measures.

Even then, the entire journey was smooth and easy for the passengers.

Yes, landing is the dangerous part in poor weather.  Yet that is also true of any aircraft today.  With an airship it can be mitigated with the right landing area.  Personally I've been diverted to other airports enough times to know that with fixed wing aircraft there are times when you simply can't land.
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Re: Airships as a way of changing the way we fly
« Reply #33 on: October 06, 2023, 04:22:56 PM »
Quote
The airship would come in upwind and then descend vertically over a clear area.
Quote
Actually neither ascent or descent take much more energy than ballast management.

The climb and descent parts of the flight also involve accelerating to cruise speed… and then getting rid of all that speed before landing.

As noted above, a huge airship will normally cruise with the prevailing winds (West to East, in the northern hemisphere), cruising in the jet stream, where winds reach 200 to 300mph [320 to 480 kph] — plus, you suggested, your ship might increase to twice wind speed, for navigational purposes….  (??)   But whatever cruise speed is attained, it must be eliminated by retro-propulsion before reaching the “cleared area.”  That requires a lot of fuel burn.  Internal ballast management does not in itself affect airspeed.

To “descend vertically over a clear area,” the ship would need to not only dump all forward speed, but fly backwards within the airmass that is moving it downwind — wind that is constantly changing with height; wind that changes speed and direction faster than the ship can react.  Never mind “poor weather” — landing in anything but absolutely calm conditions practically guarantees a crash of some sort — and a 250-tonne airship doesn’t have the option of a go-around at the last moment.
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Re: Airships as a way of changing the way we fly
« Reply #34 on: October 06, 2023, 05:57:45 PM »
As with all lighter than air ships, they adjust height to control impact from the winds.

The Hindenburg had a max power of 3,400hp and a max cruising height of 800ft.

These are serious limitations which a modern airship would expect to overcome.

Flying in upwind means you are providing thrust just to stand still and extra thrust to move forward.  If you drop thrust below the threshold of wind resistance then you start to fly backwards.

This is a large body of knowledge gained over decades with prior airship operations.  It can then be applied forwards with modern technology.  For instance I the ship would not be using ropes but highly likely to attach to a pole and then descend down the pole with the rear of the ship similarly "captured".

All it needs to do is reach the pole at the right speed and attach.  Then get control of the tail end and descend down to, or below, the ground.

There are additional things which can be built into the ship. Such as the passenger compartment being a self contained pressurised vessel which can be ejected with parachutes in extreme adverse situations.

these are things which were simply impossible with the technology used in the Hindenburg.  Useful to remember that his ship was conceived and designed in the 1920's.  The build was early 1930's.  Virtually none of the materials science of WW2 was evident in the design.

Just because you see an airlander with its gas bag structure and underpowered diesel engines, does not mean that this is the only way to do an airship or that even the constraints on an airlander apply to a more efficiently designed airship.
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Re: Airships as a way of changing the way we fly
« Reply #35 on: October 06, 2023, 07:24:04 PM »
A commercial jet lands at 120kn - 140knot of airspeed, preferably headwind or very soft tailwind (very important) and with crosswinds max 30 or even 40 kn (which is hard but doable).

Still landing is less and less often the cause of accidents.

Wind shear and storms microbursts are the worst enemies. However their detection and corresponding flight management has improved very much over the last 50 years.

I cannot even imagine how reduced the envelope of safety of a landing airship is compared to what I just described.

Why are you guys resuscitating a 100-year old tech that was already discarded while modern aviation has evolved infinitely and has no competition WHATSOEVER in these airships? To claim that minuscule elimination of 2% contribution to AGW?


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Re: Airships as a way of changing the way we fly
« Reply #36 on: October 06, 2023, 08:40:21 PM »
Quote
Flying in upwind means you are providing thrust just to stand still and extra thrust to move forward. 

In the same way the ship used the west to east jet stream winds to cruise, it can only approach the landing area roughly west to east, with the prevailing wind as a tailwind, pushing the ship along, and requiring significant retro-propulsion to come to a stop, since there is no runway to apply brakes on.

A huge airship does not have the maneuverability to perform the usual Downwind-Base-Final box-shaped approach pattern, which is normally used by regular aircraft (even the big ones, although ATC may alter it for traffic control) to precisely adjust descent rate, heading and groundspeed for landing, into the wind, on Final, in order to minimize touchdown speed. 

Flying straight in, with a tailwind, is the most dangerous kind of approach — the one most susceptible to problems even in regular aircraft which are capable of quick corrections.  As a pilot, having performed several hundred takeoffs and landings in light airplanes and helicopters, I can attest to this.
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Re: Airships as a way of changing the way we fly
« Reply #37 on: October 06, 2023, 08:46:46 PM »
Flying straight in, with a tailwind, is the most dangerous kind of approach — the one most susceptible to problems even in regular aircraft which are capable of quick corrections.  As a pilot, having performed several hundred takeoffs and landings in light airplanes and helicopters, I can attest to this.

Yeah, my terminology is wrong.  I'm talking about landing right into the head wind.
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Re: Airships as a way of changing the way we fly
« Reply #38 on: October 06, 2023, 09:55:04 PM »
Yeah, my terminology is wrong.  I'm talking about landing right into the head wind.

Which a huge airship cannot do, unless it spends hours, many miles, and tonnes of fuel, fighting the wind and changing its direction of flight to perform a circling approach.  Soooo inefficient.
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Re: Airships as a way of changing the way we fly
« Reply #39 on: October 07, 2023, 12:42:50 PM »
Yeah, my terminology is wrong.  I'm talking about landing right into the head wind.

Which a huge airship cannot do, unless it spends hours, many miles, and tonnes of fuel, fighting the wind and changing its direction of flight to perform a circling approach.  Soooo inefficient.

Depends on the power ratio.  Also remember I talked about using ISS style attitude control the spin the ship.

So it can cruise past the landing berth downwind, spin around and boost back upwind into the bay.  If you have the power to drive the ship at 200mph you have more than enough power to approach a docking tower, into a 100mph wind, at 50mph or less.  Clearly gusting winds are the real problem.  But additional attitude control helps there.

But quick, efficient and probably faster than a wide body jet doing a Taxi in all conditions fixed wing aircraft can operate in.  At Paris CDG it can take over 15 minutes to get from the runway to Terminal 1.  I know I've timed it over and over again whilst my time to catch my connecting train trickles away.

I also considered a pressurised and detachable passenger cabin so that the airship could be rapidly turned around.  No need to wait for baggage loading or passenger loading.  It would be sitting there waiting to go.  Of course a detachable cabin with chutes and possibly boosters to prevent hard landing also negates much of the hydrogen risk.

All fitting into the reduced stress architecture of flying airship.
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Re: Airships as a way of changing the way we fly
« Reply #40 on: October 07, 2023, 06:00:55 PM »
When you have built your ‘giant airship of the imagination’ in Kerbal Space Program and operated it successfully, without it tearing itself apart, running out of fuel, or crashing, let us know.
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Re: Airships as a way of changing the way we fly
« Reply #41 on: October 08, 2023, 07:27:45 PM »
When you have built your ‘giant airship of the imagination’ in Kerbal Space Program and operated it successfully, without it tearing itself apart, running out of fuel, or crashing, let us know.

I'm just throwing out ideas and showing that basing "airship" engineering on practises from the first two decades of the 20th century does not mean that we can't do better.

Face facts, the design of the Hindenburg comes from not too far away from the design of the Titanic in terms of time.  Literally a decade or so.
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Re: Airships as a way of changing the way we fly
« Reply #42 on: October 08, 2023, 11:52:03 PM »
When you have built your ‘giant airship of the imagination’ in Kerbal Space Program and operated it successfully, without it tearing itself apart, running out of fuel, or crashing, let us know.

Just curious but can you do that in KSP?
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Re: Airships as a way of changing the way we fly
« Reply #43 on: October 08, 2023, 11:56:07 PM »
When you have built your ‘giant airship of the imagination’ in Kerbal Space Program and operated it successfully, without it tearing itself apart, running out of fuel, or crashing, let us know.

Just curious but can you do that in KSP?

I found some links about designing and building airships in KSP, so it would seem so.  It would be on their Earth-simulator planet.

https://waterpigs.co.uk/articles/ksp-airship-design/
« Last Edit: October 09, 2023, 12:04:05 AM by Sigmetnow »
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Re: Airships as a way of changing the way we fly
« Reply #44 on: October 09, 2023, 12:12:32 AM »
Funny. Only watched a friend once crashing ships into Earth repeatedly for research. Probably on how to figure out how not to crash. And something with gliding or flight.
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Re: Airships as a way of changing the way we fly
« Reply #45 on: October 09, 2023, 11:55:07 AM »

I found some links about designing and building airships in KSP, so it would seem so.  It would be on their Earth-simulator planet.

https://waterpigs.co.uk/articles/ksp-airship-design/

Some interesting ideas there.  Pity I'm not a lot younger I would have worked on extension design.
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Re: Airships as a way of changing the way we fly
« Reply #46 on: October 26, 2023, 12:05:05 AM »
Google Founder’s Airship Gets FAA Clearance
https://spectrum.ieee.org/lta-airship-faa-clearance

Sergey Brin’s Pathfinder 1 can now take to the skies



IEEE Spectrum has learned that Lighter Than Air (LTA) Research, the company that Brin founded in 2015 to develop airships for humanitarian and cargo transport, received a special airworthiness certificate for the helium-filled airship in early September.

That piece of paper allows the largest aircraft since the ill-fated Hindenburg to begin flight tests at Moffett Field, a joint civil-military airport in Silicon Valley, with immediate effect.

The certificate permits LTA to fly Pathfinder 1 within the boundaries of Moffett Field and neighboring Palo Alto airport’s airspaces, at a height of up to 460 meters (1500 feet). That will let it venture out over the south San Francisco Bay, without interfering with planes flying into or out of San Jose and San Francisco International commercial airports.

The huge airship will initially be attached to a mobile mast for outdoor ground testing, before conducting about 25 low-level flights, for a total of 50 hours’ flight time.

Although its rigid design hearkens back to the gargantuan airships of the early 20th century, Pathfinder 1 is almost completely different from any large airship that has flown before. Crucially, its reported 96 welded titanium hubs and 288 carbon fiber reinforced polymer tubes are light enough that it can use non-flammable helium instead of explosive hydrogen as a lifting gas.

Twelve electric motors distributed on the sides and tail of the airship, and four fin rudders, allow for vertical takeoff and landing (VTOL) and speeds of up to about 120 kilometers per hour. A tough layer of laminated Tedlar material contains 13 helium bags of ripstop nylon, which contain lidar systems to track the gas levels within.

Pathfinder 1 has a hybrid propulsion system, with two 150 kilowatt diesel generators working alongside 24 batteries to provide power for the electric motors, according to a recent presentation by LTA’s CEO, Alan Weston. He said that LTA has plans to use hydrogen in later versions of the airship, perhaps as fuel for future fuel cells or turbogenerators, and possibly even as a lifting gas.

The gondola that LTA is using for the airship was designed by the famous Zeppelin company in Germany and can accommodate up to 14 people, although no superfluous passengers will be allowed during testing.

Ultimately, LTA intends its aircraft to be used for humanitarian missions, deploying cargo and personnel to areas that are inaccessible by road. Brin runs a separate non-profit, called Global Support and Development, that has already carried out such missions by sea, in the Caribbean, Latin American and the South Pacific.
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Re: Airships as a way of changing the way we fly
« Reply #47 on: November 09, 2023, 10:05:37 PM »
(aha, thats where i saw the Q airship, on the Drive)

This Alien-Looking Airship Design Used A Propulsion Method Unlike Any Other

Designed to lift heavy loads in and out of nearly anywhere, the LTA 20-1 airship was exotic in pretty much every way.

The aerostat featured a highly unique means of propulsion wherein its spherical balloon, once filled with helium, would rotate, lifting it into the air and sending it on its way by what's known as the 'Magnus Effect.'

https://www.thedrive.com/the-war-zone/this-alien-looking-airship-design-used-a-propulsion-method-unlike-any-other


www.cambridge.org© in this web service Cambridge University Press
Cambridge University Press
978-1-107-01970-6 - Airship Technology: Second Edition

https://assets.cambridge.org/97811070/19706/frontmatter/9781107019706_frontmatter.pdf


https://aeroscraft.com/

FOR THE FIRST TIME IN HISTORY,AN AIRCRAFT HAS BEEN DESIGNED TO CONTROL BUOYANT LIFT AND TO OFF-LOADING STORES DURING HOVER

 AEROS INFRASTRUCTURE INDEPENDENT VERTICAL LOGISTICS

    Unrestricted hub-less collection–distribution network.
    Reduction of shipping time and cost by orders of magnitude.
    Integrates multiple supply-chains, no restrictions on hub location.


https://oceanskycruises.com/

https://american-airships.com/#performance


areostat;
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vox_mundi

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Re: Airships as a way of changing the way we fly
« Reply #48 on: November 16, 2023, 04:51:35 PM »
How Silicon Valley Will Put Airships Back In Flight
https://techxplore.com/news/2023-11-silicon-valley-airships-flight.html

It's longer than three Boeing 737s. Someday it could carry up to five tons of cargo and float from San Francisco to Chicago.

Long hidden in a dark hangar at Moffett Federal Airfield in Santa Clara, California, the remarkable Pathfinder 1—a gigantic white cigar-shaped airship—was rolled out into the bright Bay Area sunshine for some quick exercise last week, then rolled back in.

The behemoth aircraft, the brainchild of Google co-founder Sergey Brin and aviation innovator Alan Weston, behaved exactly as intended.

It didn't float, because it was securely tethered by ropes held by ground crew. That's planned for next time, probably within several weeks. Its initial maneuvers will be around Moffett Field, which Google leases from NASA Ames. Over the next year, it will fly several FAA-approved missions at an altitude below 1500 feet over the waters of the South Bay, including the Dumbarton Bridge.

But, as hoped, Pathfinder "superheated" when its skin was warmed by the sun, causing it to expand and lighten. When propelled by small electric motors, it swung one direction, then another.

The Pathfinder is not a blimp, like the familiar balloons that drift over football stadiums. Blimps have no internal structure so can lose their shape, and deflate. The Pathfinder is an dirigible, with a rigid framework of 10,000 carbon-fiber reinforced tubes and 3,000 titanium hubs to form a protective skeleton around the gas cells, surrounded by a lightweight synthetic Tedlar skin.

The airship is about 400 feet long. By comparison, the traditional Goodyear blimp is 250 feet long.

Pathfinder 1 will be the largest aircraft to take to the skies since the ill-fated Hindenburg dirigible of the 1930s, a major air disaster that was broadcast to people all over the world.



Pathfinder 1 is just the first in what could be a family of airships, according to Weston.

Even as this prototype learns how to reliably fly in real-world conditions, LTA is starting construction of another and much larger airship, called Pathfinder 3, in the same Akron, Ohio, hangar where Goodyear built the U.S. Navy's rigid airships of the 1930s.

That aircraft, one-third bigger than Pathfinder 1, could be ready for flight later this year.
« Last Edit: November 16, 2023, 04:58:28 PM by vox_mundi »
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morganism

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Re: Airships as a way of changing the way we fly
« Reply #49 on: February 22, 2024, 06:52:40 AM »
Space Perspective could begin test flights of its privately owned capsule suspended under a high-altitude balloon within the next couple of months, the company's co-founder told Ars this week.

Florida-based Space Perspective released photos of its first completed test capsule Tuesday. The company will use this pressurized capsule, called Excelsior, for a series of test flights this year over the Atlantic Ocean just off the coast of Cape Canaveral. Taber MacCallum, Space Perspective's co-founder and chief technology officer, said employees have also finished fabricating the giant balloon that will lift the test capsule into the upper atmosphere for the first test flight.

The final piece of the puzzle is a ship, named Marine Spaceport Voyager, that Space Perspective will use to launch the balloon and capsule. This vessel is due to depart an outfitting facility in Louisiana in the next few weeks for a trip to Port Canaveral, Florida, where Space Perspective will load aboard the capsule and balloon. Then, perhaps in four to six weeks, ground teams will be ready for the system's first test flight, according to MacCallum.
(more)

https://arstechnica.com/space/2024/02/test-flights-on-tap-for-space-perspectives-luxury-high-altitude-balloon/#p3