What will power our vehicles in the future?

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#2765352 23-Aug-2021 12:16

RobDickinson:

So basically 2 cylindrical cells in an aero shaped cover.

Yep - but just pointing out that Project Fresson was able to abandon their initial battery powered retrofit plans for the Islander, and consider Hydrogen fuel-cell, mainly because Innovatus was able to spec pylon mounted H2 tanks that would meet the environmental, regulatory and operational requirements for this size of the aircraft.

Their Hydrogen storage system, rather than being some slap-dash add on, is key - along with Ricardo's fuel cell systems and controller - to getting the project off the ground (pun intended).

Innovatus Technologies Ltd's ShyFT (Scottish Hydrogen Fuel Tank) is - they claim - an engineered composite high-pressure vessel for gaseous hydrogen. It's a multi-chamber design, that can conform to applications where simple, cylindrical shapes simply aren’t practical. And with it, the company boasts having the world’s highest gravimetric storage density, of 10%. They also claim their tank is 25% lighter and has a 20% lower cost than competing tanks.

There are other early stage H2 fuel cell aircraft projects also looking at using Innovatus tanks, so just pointing out that rather than 'whoever designed that hasn't thought about it much at all' - their tank design's the culmination of a decade of research and millions of dollars of investment..

frankv

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#2765362 23-Aug-2021 12:27

Two cylinders will have half the volume of one cylinder with twice the radius (V = 2 * (L * pi * (R/2)^2)), but will have nearly the same surface area (A = 2 * (L * pi * R + 2 * pi * (R/2)^2)), where R is the radius of one large cylinder.

So weight (proportional to surface area) is about the same, but volume is halved. Clearly weight isn't paramount. And given the right angle between the pylon and the pod, with no intersection fairing, I'd say aerodynamics isn't key either. All in all, not a very efficient way to carry hydrogen.

Their largest tank can hold 5.4kg of hydrogen = 648MJ of energy. They boast of a Gravimetric Storage Density of 10%... i.e. the tank weighs 10 times as much as the hydrogen, so 54kg, and a total weight of about 60kg. The equivalent in energy for jet A1 is about 15kg (about 19 litres), with maybe a couple of kg for the tank. But if you can put they hydrogen through a fuel cell instead of an ICE, you get a huge improvement in efficiency.

I started out with these calculations to show that numerically it wasn't feasible, but I must admit it looks doable -- two hydrogen tanks instead of jet A1 tanks on the plane would mean one less passenger, so not a huge disaster. And maybe you get some of that weight back, depending on the weight of the fuel cell(s) and motors (anyone got numbers for those?) vs the weight of a couple of ICEs.

Technofreak

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#2765373 23-Aug-2021 12:46

morrisk:

Technofreak you note "For sure some of Sounds Air's routes could work..." which I guess is the reason that they have placed an order.

Having some routes, some of the time flown by an electric plane will reduce their emissions so that is an improvement if the goal is to reduce emissions as a company. It may come at a cost but they must have thought of that and accept this.

The key point is the cost of no one doing anything is as predicted by all credible scientists - significant global warming and the cost of that in relation to the world as we know it.

Note I said could work. The performance data from Heart is very basic so it's very hard to accurately determine exactly the endurance of the ES19. I rather suspect that when you dig deep enough you will find the endurance is severely limiting to the extent that except for blue sky days that aircraft is practically useless.

Aviation accounts for around 2% of all CO2 emissions. As others have said there are areas that will produce a much better environmental return for the dollar than aviation.

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Technofreak

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#2765384 23-Aug-2021 13:00

RobDickinson:

Sigh.

"It gives an energy cost per kWh of 17.4 dollar cents for the Turboprop aircraft and 7.1 dollar cents for the electrical aircraft (both engines drive the propellers, which are assumed to be equally efficient in the two cases)."

https://leehamnews.com/2021/07/01/the-true-cost-of-electric-aircraft/

Now imagine if we apply correct carbon pricing to jet fuel...

Sigh!!!!!!!!!!

You only read the first part where he calculates the direct cost of the energy which for the sample mission came out at $181 USD for jet fuel and $67 USD for the electricity consumed. You need to read on a bit further where he talks about the total cost of the battery energy. When you calculate the costs of the batteries amortised over 1000 cycles you come up with a per flight cost of $847.80. Add on the electricity costs you end up with $914.80 USD which is just over 5 times more than the cost of jet fuel.

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Technofreak

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#2765389 23-Aug-2021 13:11

Dingbatt:

Hence my comment about the low hanging fruit. Put the most energy (pun intended) into de-carbonising surface transport. Battery technology and hydrogen technology will be improved by that, the offshoot being improving the viability for aviation.

As far as that picture of the Islander goes, two words, airframe icing.

Agree entirely about the low hanging fruit.

I don't see icing as an issue peculiar to the tanks, true icing is an issue but that goes for the whole airframe. The tanks can be put inside a shape or fairing that minimised drag and icing.

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Technofreak

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#2765400 23-Aug-2021 13:22

frankv:

PolicyGuy:

There are already designs - yes, paper only at this point - for short-range aircraft with under-wing lightweight carbon fibre tanks for liquid hydrogen. Like this B-N Islander based design:

Literally pi(e) in the sky. Those pods are the wrong shape for cryogenic hydrogen storage. Ideally you would have spheres, to maximise volume/surface area. Next best would be cylindrical or ovoid. But a cuboid (albeith with rounded corners and ends) that is small in one dimension is just about the worst shape you could choose. So whoever designed that hasn't thought about it much at all.

I think what you're seeing is an artists impression and not the final shape. Also the tanks will end up in a fairing to optimise drag profiles etc.

It seems there has been a fair bit of development on these tanks. Whether or not they end up being practical is another question.

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RobDickinson

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#2765402 23-Aug-2021 13:27

Technofreak:

Sigh!!!!!!!!!!

You only read the first part where he calculates the direct cost of the energy which for the sample mission came out at $181 USD for jet fuel and $67 USD for the electricity consumed. You need to read on a bit further where he talks about the total cost of the battery energy. When you calculate the costs of the batteries amortised over 1000 cycles you come up with a per flight cost of $847.80. Add on the electricity costs you end up with $914.80 USD which is just over 5 times more than the cost of jet fuel.

Thats a ridiculous claim though. batteries will last far longer than 1000 cycles, and will get cheaper etc.

Yet still we dont have correct environmental impact priced into jet fuel

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Technofreak

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#2765439 23-Aug-2021 14:03

RobDickinson:

Technofreak:

Sigh!!!!!!!!!!

You only read the first part where he calculates the direct cost of the energy which for the sample mission came out at $181 USD for jet fuel and $67 USD for the electricity consumed. You need to read on a bit further where he talks about the total cost of the battery energy. When you calculate the costs of the batteries amortised over 1000 cycles you come up with a per flight cost of $847.80. Add on the electricity costs you end up with $914.80 USD which is just over 5 times more than the cost of jet fuel.

Thats a ridiculous claim though. batteries will last far longer than 1000 cycles, and will get cheaper etc.

Yet still we dont have correct environmental impact priced into jet fuel

The author of that article doesn't agree and explains why.

The increased weight of the aircraft makes it accelerate slower to takeoff speed. It doubles the runway distance needed for takeoff. Once in the air, the increased drag from the weight and the larger wing increases the aircraft’s drag. To compensate, we need to run the engines harder to generate more thrust. It increases energy consumption.

Despite optimizing the aircraft speed in all flight regimes to lower drag and thus thrust, the aircraft consumes more energy than the Beech 1900. As it flies slower than the Beech 1900 to minimize drag, it keeps this higher energy consumption for longer.

The result is the aircraft consumes three times more energy for the 200nm trip, at over 3,000kWh. As we have 1,000kWh available for the trip (the rest has to remain reserves), our range of the aircraft is less than 100nm.

There is no point in increasing the battery size to increase the possible range, as when we increase the battery size, and by it the aircraft weight, the range decreases. The aircraft drag rises faster than our available energy increases.

The problem with available energy means we can’t size the battery for optimal time on aircraft before changes. We need to load the battery to 100% for each flight to get somewhere (not the 200nm we should though). The operating costs skyrocket as we need to change batteries after 1,000 flights, which with six flights per day is every six months.

The finding is the battery energy density has to climb above 1kWh per kg to change this, and we are today some 600% from this point.

Conclusion
Electric aircraft came in vogue when electric cars worked, with Tesla as a good example. The point all missed was that our petrol cars are miserable energy hogs. They use about 5%-7% of the energy in the gasoline as they coast from stoplight to stoplight.

Battery or hybrid cars recover energy as you stop for the light. But there are no stoplights in the sky and our airliners use between 25% to 50% of the energy in the jet fuel. It means electric aircraft, whether with batteries or hybrid, doesn’t improve state of the art; they degrade it.

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Technofreak

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#2765444 23-Aug-2021 14:09

Dinga96:

Would you better off putting those drop tanks somewhere else apart from the undersides of the outer wing. There just going to get in the way there.

If you take the Cessna Caravan for instance .Some varients have a quiet large hold under the forward fuselage.I wonder how many tanks could sit in that hold.More than that concept drawing Islanders I suspect.

Under the wing is just fine. Probably as good as anywhere plus it's close to the centre of gravity.

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Dingbatt

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#2765463 23-Aug-2021 14:48

Technofreak:

quote:Dinga96:

Would you better off putting those drop tanks somewhere else apart from the undersides of the outer wing. There just going to get in the way there.

If you take the Cessna Caravan for instance .Some varients have a quiet large hold under the forward fuselage.I wonder how many tanks could sit in that hold.More than that concept drawing Islanders I suspect.

unquote

Under the wing is just fine. Probably as good as anywhere plus it's close to the centre of gravity.

Well no, not really. Point loads are different from distributed loads (ie a fuel tank), so unless the wing has been designed to take pylon tanks (not drop tanks which as far as I know are only used by military aircraft) a structural redesign would be required. And yes airframe icing is a problem for pylon tanks particularly if they are ‘pre-cooled’ by their contents. The altitudes that these propellor driven commuter aircraft operate in is right in the icing zone.

Dinga96: The gondola fairing on the Caravan is fitted to compensate for its otherwise inadequate baggage storage. Any weight carried in a non-lift producing part of the aircraft requires more structure in the wing, which requires more lift, which requires more structure in the wing, etc…

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Technofreak

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#2765486 23-Aug-2021 15:38

Dingbatt:

Well no, not really. Point loads are different from distributed loads (ie a fuel tank), so unless the wing has been designed to take pylon tanks (not drop tanks which as far as I know are only used by military aircraft) a structural redesign would be required. And yes airframe icing is a problem for pylon tanks particularly if they are ‘pre-cooled’ by their contents. The altitudes that these propellor driven commuter aircraft operate in is right in the icing zone.

That's a given re the structure and possible need for redesign, no argument there. You might be interested to know the BN2 has an approved modification to allow under wing pylons to the fitted. My comment was in response to the the wing tanks being in the way by being located under the wings, they are not in the way.

Re the the airframe icing, that's rather a moot point as the BN2 Islander is not certified for flight in icing conditions when the under wing pylons are used. Without the pylons the aircraft has to be fitted with an approved modification incorporating appropriate de-icing and anti-icing equipment before flight into icing conditions can be contemplated. Then it's still only approved for light icing conditions. Basically a system to allow you time to exit icing conditions, it's not a system to allow continued flight in icing conditions

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Dingbatt

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#2765496 23-Aug-2021 16:07

We agree then. But my points apply to more than the horrible little puss bucket that the BN2 is (personal opinion :-)).

When I was young I saw wonderful drawings of the Boeing 2707 SST. But all I ever saw were drawings (I know some serious design went on). Nothing ever flew. I fear a lot of these designs will remain as drawings.

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Technofreak

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#2765598 23-Aug-2021 16:59

Dingbatt:

We agree then. But my points apply to more than the horrible little puss bucket that the BN2 is (personal opinion :-)).

When I was young I saw wonderful drawings of the Boeing 2707 SST. But all I ever saw were drawings (I know some serious design went on). Nothing ever flew. I fear a lot of these designs will remain as drawings.

I agree, many won't see the light of day. Speaking of the BN2 here's one development that didn't go far. I'm sure you'll enjoy this slight diversion off topic since you are such a fan of the BN2.

Undaunted by aerodynamic reality, the design team at Pilatus/Britten-Norman has announced plans for the BN2-XL (Extra Loud), promising more noise, reduced payload, a lower cruise speed, and increased pilot workload.

We spoke to Mr. Fred Gribble, former British Rail boilermaker and now Chief Project Engineer. Fred was responsible for developing many original and creative design flaws in the service of his former employer, and assures he will be incorporating these in the new BN2-XL technology under a licensing agreement.

Fred reassured BN-2 pilots however that all fundamental design flaws of the original model had been retained. Further good news is that the XL version is available as a retrofit.

Among the new measures is that of locking the ailerons in the central position, following airborne and simulator tests which showed that whilst pilots of average strength were able to achieve up to 30° of control wheel deflection, this produced no appreciable variation in the net flight path of the aircraft.

Thus the removal of costly and unnecessary linkages has been possible, and the rudder has been nominated as the primary directional control. In keeping with this new philosophy, but to retain commonality for crews transitioning to the XL, additional resistance to foot pressure has been built into the rudder pedals to prevent overcontrolling in gusty conditions (defined as those in which wind velocity exceeds 3 knots).

An outstanding feature of Islander technology has always been the adaptation of the 0-540 engine, which mounted in any other aircraft in the free world (except the Trislander) is known for its low vibration levels, so as to cause it to shake and batter the airframe, gradually crystallise the main spar, desynchronise the accompanying engine, and simulate the sound of fifty skeletons fornicating in an aluminium dustbin.

Britten-Norman will not disclose the technology they applied in enhancing this effect in the XL, but Mr. Gribble assures us it will be perpetuated in later models and sees it as a strong selling point; "After all, the Concorde makes a lot of noise," he said, "and look how fast it goes."

However, design documents clandestinely recovered from the Britten-Norman shredder have solved a question that has puzzled aerodynamicists and pilots for many years, disclosing that it is actually noise which causes the BN-2 to fly. The vibration set up by the engines and amplified by the airframe, in turn causes the air molecules above the wing to oscillate at atomic frequency, reducing their density and causing lift. This can be demonstrated by sudden closure of the throttles, which causes the aircraft to fall from the sky. As a result, lift is proportional to noise rather than speed, explaining amongst other things the aircraft's remarkable takeoff performance.

In the driver's cab (as Gribble describes it), ergonomic measures will ensure that long-term PBN pilots' deafness does not cause inflight dozing. Orthopaedic surgeons have designed a cockpit layout and seat to maximise backache, enroute insomnia, chronic irritability, and terminal (post-flight) lethargy. Redesigned 'bullworker' elastic aileron cables, now disconnected from the control surfaces, increase pilot workload and fitness.

Special noise retention cabin lining is an innovation on the XL, and it is hoped in later models to develop cabin noise to a level which will enable pilots to relate ear pain directly to engine power, eliminating the need for engine instruments altogether.

We were offered an opportunity to fly the XL at Britten-Normans' developmental facility, adjacent to the Britrail tea rooms at Little Chortling. (The flight was originally to have been conducted at the Pilatus plant, but aircraft of Britten-Norman design are now prohibited from operating in Swiss airspace during the avalanche season).

For our mission profile, the XL was loaded with fossil fuel for a standard 100 nm with Britrail reserves, carrying one pilot and nine passengers to maximise discomfort.

Passenger loading is unchanged, the normal under-wing protrusions inflicting serious lacerations on 71% of boarding passengers, and there was the usual entertaining confusion in selecting a door appropriate to the allocated seat.

The facility for the clothing of embarking passengers to remove oil slicks from engine cowls during loading has also been thoughtfully retained.

Startup is standard, and taxying, as in the BN-2, is accomplished by brute force. Takeoff calculations called for a 250 decibel power setting, and the rotation force for the (neutral) C of G was calculated as 180ft/lbs of back pressure.

Initial warning of an engine failure during takeoff is provided by a reduction in flight instrument panel vibration. Complete seizure of one engine is indicated by the momentary illusion that the engines have suddenly and inexplicably become synchronised. Otherwise, identification of the failed engine is achieved by comparing the vibration levels of the windows on either side of the cabin. (Relative passenger pallor has been found to be an unreliable guide on many BN-2 routes because of ethnic considerations).

Shortly after takeoff the XL's chief test pilot, Capt. "Muscles" Mulligan, demonstrated the extent to which modem aeronautical design has left the BN-2 untouched; he simulated pilot incapacitation by slumping forward onto the control column, simultaneously applying full right rudder and bleeding from the ears. The XL, like its predecessor, demonstrated total control rigidity and continued undisturbed.

Power was then reduced to 249 decibels for cruise, and we carried out some comparisons of actual flight performance with graph predictions.

At 5000' and ISA, we achieved a vibration amplitude of 500 CPS and 240 decibels, for a fuel flow of 210 lb/hr, making the BN-2 XL the most efficient converter of fuel to noise since the Titan rocket.

Exploring the constant noise-variable speed and constant speed-variable noise concepts, we found that in a VNE dive, vibration reached its design maximum at 1000 CPS, at which point the limiting factor is the emulsification of human tissue. The catatonic condition of long term BN-2 pilots is attributed to this syndrome, which commences in the cerebral cortex and spreads outwards.

We asked Capt. Mulligan what he considered the outstanding features of the XL. He cupped his hand behind his car and shouted. "Whazzat?"

We returned to Britten-Norman field convinced that the XL model retains the marque's most memorable features, while showing some significant and worthwhile regressions.

Pilatus/Britten-Norman are however not resting on their laurels. Plans are already advanced for the three-engined Trislander XL, and noise tunnel testing has commenced. The basis of preliminary design and performance specifications is that lift increases as the square of noise, and as the principle of acoustic lift is further developed, a later five-engined vertical takeoff model is another possibility.

Thread drift OFF.

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Dinga96

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#2765808 24-Aug-2021 11:07

Dingbatt:

Technofreak:

quote:Dinga96:

Would you better off putting those drop tanks somewhere else apart from the undersides of the outer wing. There just going to get in the way there.

If you take the Cessna Caravan for instance .Some varients have a quiet large hold under the forward fuselage.I wonder how many tanks could sit in that hold.More than that concept drawing Islanders I suspect.

unquote

Under the wing is just fine. Probably as good as anywhere plus it's close to the centre of gravity.

Well no, not really. Point loads are different from distributed loads (ie a fuel tank), so unless the wing has been designed to take pylon tanks (not drop tanks which as far as I know are only used by military aircraft) a structural redesign would be required. And yes airframe icing is a problem for pylon tanks particularly if they are ‘pre-cooled’ by their contents. The altitudes that these propellor driven commuter aircraft operate in is right in the icing zone.

Dinga96: The gondola fairing on the Caravan is fitted to compensate for its otherwise inadequate baggage storage. Any weight carried in a non-lift producing part of the aircraft requires more structure in the wing, which requires more lift, which requires more structure in the wing, etc…

Dingbat referring to your last comment above

Well both the DeHaviland Mosquito and Lancaster carried increasingly heavy payloads, much heavier than at the start of their service life.

No wing design change as far as I know.

Dinga96

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Master Geek

#2765815 24-Aug-2021 11:18

Hydrogen may still be considered to have a question mark as to its future in aviation but these guys seem to think it will be a goer.I do not know how this will work.They appear to be serious about the future developement of Hyrogen delivery to airports and to aircraft,not much detail though .What do you all think.

Universal Hydrogen to convert 15-plus airliners to run on H2 pods (newatlas.com)

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