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Sagita Displays Hot Air Powered Helicopter

samzenpus posted about 10 months ago | from the full-of-hot-air dept.

Transportation 73

rcastro0 writes "Gizmag reports on the Sherpa, an interesting helicopter design at this year's Paris Air Show. As the article explains 'Rather than driving the rotors directly, the Sherpa's engine instead powers a compressor with an air intake at the rear of the helicopter.' There's no tail rotor. This approach is supposed to be more efficient, more reliable and more affordable than the traditional. A one-fifth scale model was shown to fly. Sagita, the 2008 startup behind the project, has yet to build a full scale prototype. They plan to sell a Sherpa two-seater for around US$ 200k in 3 years."

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So (0)

Anonymous Coward | about 10 months ago | (#44066507)

It's a "jet" (albeit powered by a piston-based engine) powered gyrorotor? Free-spinning prop, airflow to the back? I didn't RTFA, but this is what the summary seems to describe.

Re:So (-1)

Anonymous Coward | about 10 months ago | (#44066559)

Is she illin in the panicillin?
Is she chillin in the panicillin?
Is she stealin in the panicillin?
Is she feelin in the panicillin?

Panka panka

Is she liable no suitifiable pliable style is so suitifiable
Is she liable no suitifiable im not on trial but its suitifiable
Is she reliable no suitifiable not just viable but real suitifiable
Is she try-able no suitifiable lying in the aisle im real suitifiable

Is she spillin in the panicillin?
Is she squealin in the panicillin?
Is she feelin in the panicillin?
Is she trillin in the panicillin?

Panka panka

Is it libel? no suitifiable pliable style is so suitifiable
Is it a style? no suitifiable im not on trial but its suitifiable
Is it a mile? no suitifiable not just viable but real suitifiable
Is it wild? no suitifiable lying in the aisle im real suitifiable

this word power seems to have been lost (-1)

decora (1710862) | about 10 months ago | (#44066959)

power = work done over a period of time.

most normal people ascribe it to the fuel used. coal fired. gas fired. gasoline fired. propane. nuclear.

morons seem to think any part of the process = power, or even the IT idiots think the CPU runs on unicorn farts and claim the laptop is 'powered by intel'. intel doesnt fucking run gas turbines. this helicopter doesnt fucking run on hot air.

Re:this word power seems to have been lost (2)

wagnerrp (1305589) | about 10 months ago | (#44067119)

You've got that backwards. Work is power done over a period of time.

Re:this word power seems to have been lost (-1)

Anonymous Coward | about 10 months ago | (#44067701)

You've got that backwards. Work is power done over a period of time.

Not that it really matters:

Work = Force * Distance
Power = Work * Time

Work is the energy spent
Power is the rate

Re:this word power seems to have been lost (2, Interesting)

Anonymous Coward | about 10 months ago | (#44068021)

I research and teach physics, and even I think you're being kind of stupid here. Yes, that is a stab at the physics definition of power, but it should be pretty obvious to anyone with some basic understanding of English that there is a non-jargon meaning to the word, and usually it is quite clear from context which is meant. Many words have more than one meaning, get used to it, unless equivocation is a hobby of yours.

Re:So (1)

flyneye (84093) | about 10 months ago | (#44069195)

They didn't go into the "green hybrid" detail about the copter utilizing hose fed flatulence from the pilot and passengers, either.

Test it in Washington (3, Funny)

reboot246 (623534) | about 10 months ago | (#44066557)

Just put one of these helicopters over Washington D.C., and you'd have an unlimited supply of hot air.

The thing would be able to run forever!

Re:Test it in Washington (2)

NettiWelho (1147351) | about 10 months ago | (#44066937)

And get yourself arrested by the feds by siphoning illegally off the national strategic hot air reserve.

IT'S MADONNA'S BIRTHDAY! (-1, Offtopic)

Anonymous Coward | about 10 months ago | (#44066573)

I made it through the wilderness
Somehow I made it through
Didn't know how lost I was
Until I found you

I was beat incomplete
I'd been had, I was sad and blue
But you made me feel
Yeah, you made me feel
Shiny and new

Chorus:

Like a virgin
Touched for the very first time
Like a virgin
When your heart beats (after first time, with your heartbeat)
Next to mine

Gonna give you all my love, boy
My fear is fading fast
Been saving it all for you
cause only love can last

You're so fine and you're mine
Make me strong, yeah you make me bold
Oh your love thawed out
Yeah, your love thawed out
What was scared and cold

MADONNA IS THE BEST!

Re:IT'S MADONNA'S BIRTHDAY! (-1)

Anonymous Coward | about 10 months ago | (#44067105)

The Three Johns (used to?) do a funny routine in their live shows mocking Madonna as a prelude to "English White Boy Engineer".

It's very funny!

"Engineer, Engineer"

What are they up to? (1)

Cassini2 (956052) | about 10 months ago | (#44066595)

It is not energy efficient to run the main rotor based on simple compressed air. Thermodynamically compressing the air and then letting it decompress results in a great deal of waste heat energy. Mechanical systems are significantly more energy inefficient.

I'm wondering if they have separated the compressor and turbine stages in a conventional jet engine in an effort to get a fuel economy or weight improvement.

Re:What are they up to? (0)

Anonymous Coward | about 10 months ago | (#44066629)

I think the engine heating the air ads to its expansion, and increases the efficiency.

Re:What are they up to? (4, Insightful)

russotto (537200) | about 10 months ago | (#44066687)

I'm wondering if they have separated the compressor and turbine stages in a conventional jet engine in an effort to get a fuel economy or weight improvement.

I cheated and read the article, and it appears that is what they've done.

However, they haven't actually built it; they have a 1/5 scale model, but it's using an electric motor (so it's not clear what it proves), and furthermore the laws of aerodynamics are not scale-invariant.

It's not clear why they're trumpeting the lack of a tail rotor as a new thing; this isn't a NOTAR design (single main rotor with no tail rotor); it's a coaxial helicopter, which is nothing new at all.

Re:What are they up to? (1)

camperdave (969942) | about 10 months ago | (#44066871)

What bothers me is that if this is a counter-rotating coaxial design, they why does it have a tail at all? Are we too used to seeing helicopters with tail booms that we can't imagine one without one?

Re:What are they up to? (3, Informative)

m0n0RAIL (920043) | about 10 months ago | (#44067089)

The tail provides stability during forward motion. A helicopter without one would need constant corrections to maintain its orientation during forward flight.

Re:What are they up to? (0)

Anonymous Coward | about 10 months ago | (#44067201)

"Are we too used to seeing helicopters with tail booms that we can't imagine one without one?"

Duuuuuuuuude... it's where the GoPro mounts!

Re:What are they up to? (5, Informative)

stockard (1431131) | about 10 months ago | (#44067219)

Coaxial helicopters still have a tail due to the controls on the empennage. Helicopters are a bit odd in that the pilot is basically flying the rotor disk, and the fuselage is kinda just "along for the ride". So, if you wanted to rotate or adjust the pitch of the fuselage, you'd need some sort of controls on the fuselage to do so. (Some adjustment can be made with the rotors, but the standard tail controls are a bit simpler.) So, while coaxial helicopters are more inherently stable and don't need a tail rotor, they'll still have a tail. (See the Ka-50 [wikipedia.org] , X2 [wikipedia.org] and Ka-27 [wikipedia.org] among others [wikipedia.org] , as examples.)

The reason you want controls at the aft end of the the tail is because for things like the elevator, you want as big a moment arm as possible to reduce the force required to adjust the pitch of the aircraft. Similarly, the vertical stabilizers are there to help reduce sideslip at higher speed, since a helicopter can fly in any direction, regardless of the orientation of the fuselage. (Generally for lighter helicopters, the vertical stabilizers are fixed, though the larger ones can have a movable rudder.)

Additionally, having a tail will help you if you need to do an autorotation [wikipedia.org] , as it will help prevent the rotors from impacting the ground at the rear when you flare it right before landing. (Here are some examples: http://www.youtube.com/watch?v=T-5ARzqF3R4 [youtube.com] )

Disclaimer: While I'm a helicopter engineer, I don't work on the controls, so this may be a bit of a simplistic explanation. :)

No disclaimer needed (1)

Anonymous Coward | about 10 months ago | (#44068053)

No disclaimer is needed. This is precisely the reason I still come to this site. Bravo!

Re:What are they up to? (1)

Jane Q. Public (1010737) | about 10 months ago | (#44071877)

"...you want as big a moment arm as possible to reduce the force required to adjust the pitch of the aircraft."

This.

As well as improve stability, I would think. While main-rotor adjustments might be sufficient to control yaw, having that "moment" probably smooths out that control by adding some inertia.

Re:What are they up to? (1)

Jeng (926980) | about 10 months ago | (#44066913)

but it's using an electric motor

Yes, apparently the helicopter that is suppose to run on hot air does not, which makes this just a bunch of hot air.

What are they up to?

Seeking venture capitol.

Re:What are they up to? (0)

Anonymous Coward | about 10 months ago | (#44067151)

The article doesn't seem to state that this is intended to use a conventional gas turbine. Could they be planning to use an internal combustion engine instead, something like the Caproni-Campini engine of the 1940s?

Re:What are they up to? (1)

wagnerrp (1305589) | about 10 months ago | (#44069491)

It's similar, but not quite the same. In a motorjet, you basically have a piston-driven afterburner. The piston engine powers the compressor, the compressed air is combusted, and the exhaust is dumped out the back end. This is dumping the combustor, and using the compressed air to drive a pair of contrarotating turbines, in turn driving rotors.

Re:What are they up to? (3, Interesting)

modecx (130548) | about 10 months ago | (#44070733)

As far as I can see, their innovation can be accurately summed up thus:

They've decoupled the power turbine (the one which provides power to the rotors via a gears and such) from the engine, and mix cooler air into the exhaust stream. They've done away with the transmission and drive train by forcing this much cooler exhaust stream through a power turbine directly coupled to the main rotors, and they have also eliminated all of the complexity of a tail rotor and associated drive train by going with co-axial counter-roating rotors to provide necessary anti-torque.

It's the laws of thermodynamics I'm most concerned about, since most thermodynamic cycles suffer when cold fluids are introduced. Maybe eliminating the losses in mechanical transmission and weight offset that? Who knows, but if it works like they claim, that's pretty cool.

Re:What are they up to? (1)

camperdave (969942) | about 10 months ago | (#44066935)

It seems to me that if they directed the exhaust downward, rather than using it to drive a turbine to spin the rotors, they'd be ahead of the game. As it is, this seems like a glorified turboprop engine.

Re:What are they up to? (1)

Ungrounded Lightning (62228) | about 10 months ago | (#44066991)

... this seems like a glorified turboprop engine.

Which it is.

But without the fancy gearbox of a turboprop or the transmission of an engine-driven rotor. It should be WAY simpler mechanically, much lighter, and need far fewer moving parts. Eliminating the gearbox losses should gain them far more efficiency than plumbing the fast, hot, gas around costs.

Re:What are they up to? (2)

wagnerrp (1305589) | about 10 months ago | (#44067205)

Without the "turbo" part either. "Turbo" implies a gas turbine engine. Turbojets are nothing more than a gas turbine. Turbofans have a gas turbine at their core. A turbocharger is a gas turbine wrapped around an internal combustion engine. This is a piston powered helicopter with a fluid dynamic transmission. It's merely different from the typical fluid dynamic transmission in that it is an open loop. Anyone in the automotive world will tell you a fluid dynamic transmission is lossy and inefficient. The only reason to plumb hot gasses around is because your engine design means you already have those hot gasses handily available. Oh, and they decided to supercharge it for some reason...

As for hot, fast gasses, they claim to be powering the rotor turbines with 100C compressed air, that's only that temperature after being heated up by the engine coolant and engine exhaust. At that temperature, there's not even enough energy in the flow to make that supercharger a net gain.

This would be a very interesting design if they actually used a gas turbine engine, rather than a piston engine (or realistically, an electric motor in their scale demo), as they would actually have enough exhaust flow to make it work. It would basically be the same thing GE did with their unducted fan, mating the contrarotating fan disks directly to a pair of contrarotating turbine disks, eliminating any deswirler or gearbox. The trouble is that these rotors have a strict top speed. Their tips cannot exceed the speed of sound, as doing so would cause all kinds of noise and vibrational issues on the helicopter. The scale difference between the rotor and the turbine means that means you're going to be running at a painfully low RPM, which is exactly why no one has done this commercially yet. It's really tough to get a turbine running that slowly, efficiently, and with significant power output.

Military applications (0)

Anonymous Coward | about 10 months ago | (#44066599)

(1) Can You armor that center point on the rotors to make more it bullet resistant than a standard heli?
(2) how loud/quiet it is?

Sounds iffy (0)

Anonymous Coward | about 10 months ago | (#44066635)

The fluid coupling between the compressor and the rotor can't be efficient. I guess you're saving power that'd be going to the tail rotor, but what's providing your yaw action? A steerable nozzle in the tail?

Hmmn.....

Re:Sounds iffy (1)

Ungrounded Lightning (62228) | about 10 months ago | (#44066955)

The fluid coupling between the compressor and the rotor can't be efficient.

SURE it can.

What makes you think it can't? It's just a rotating joint with a seal on a hollow shaft. Nothing new here, move along.

In fact there is nothing new here anyhow, unless there's some aspect of it they're not telling us. "Water sprinkler rotor"-style helicopters have been played with for half a century or so.

Re:Sounds iffy (1)

wagnerrp (1305589) | about 10 months ago | (#44069581)

Because fluid couplings are inherently inefficient. You use them in a turboshaft engine because of the very nature of your gas turbine core, releasing all of its energy as large volumes of exhaust air. You use them on cars and heavy industrial vehicles because they continue to produce significant torque even when stalled out at zero RPM, allowing you to move heavy loads from a standstill without burning up a mechanical clutch. When you don't have good reason to use a fluid coupling, you use a mechanical one for the efficiency gains.

the helicopter's performance is theoretical (1)

manu0601 (2221348) | about 10 months ago | (#44066679)

TFA says "the helicopter's performance is theoretical". They only flew a 1/5 scaled prototype.

Hot Air Powered Helicopter (1)

NettiWelho (1147351) | about 10 months ago | (#44066745)

Hot Air Powered Locomotion; This new technology will ensure the hyperpower status of the USA for the 21st century; given plentyful resources located in the north americas politician deposits.

Re: Hot Air Powered Helicopter (1)

jd2112 (1535857) | about 10 months ago | (#44066953)

What we need is a generator that runs on bullshit. Washington DC could be the Saudi Arabia of bovine excrement power with ample reserve in Wall St. in the unlikely event that DC should ever prove insufficient.

Re:Hot Air Powered Helicopter (1)

Ungrounded Lightning (62228) | about 10 months ago | (#44067011)

This new technology will ensure the hyperpower status of the USA for the 21st century; given plentyful resources located in the north americas politician deposits.

Nah. The U.S. has no monopoly on government bombast.

Aren't They All (0)

Anonymous Coward | about 10 months ago | (#44066841)

I guess I'm missing something but aren't all helicopters powered by compressed gas? ;-) We have various ways of using fuel to create the compressed gases but all methods produced high pressure gases that are then used to do work.

My first thought ( as it seems with most posters) was to hitch the thing to as many politicians as we can catch. Not only would we have people on the moon and Mars but the Cherenkov radiation due to the high acceleration would be entertaining.

Something isn't adding up... (3, Interesting)

wagnerrp (1305589) | about 10 months ago | (#44067003)

According to the article, the air is compressed, then heated by the engine's cooling system, then mixed with exhaust gasses, and the resultant flow into the turbine is only 100C? Something doesn't seem right here. That temperature difference implies such a low boost that it won't even operate effectively as a supercharger, much less provide anything like enough power to those turbines. There's a reason gasoline engines with worthwhile turbochargers and superchargers all have intercoolers, and that's because compressing air makes it really damn hot.

Re:Something isn't adding up... (0)

Anonymous Coward | about 10 months ago | (#44067193)

They're claiming 85% efficiency, which if true would represent an efficiency gain of about 30% over the best engines available today and would have been discovered about 80 years ago.

It's marketing hype exaggerated enough that even gullible layman spot it easily.

Re:Something isn't adding up... (0, Insightful)

Anonymous Coward | about 10 months ago | (#44067385)

It sounds like a turbine being used to compress air, which then spin the rotor blades via some type of air pump. Is the gain in efficiency made through avoiding a gearbox and powering the rotors via a direct drive? Sounds like a good idea! If it works as well as they claim there could be a lot of other applications.

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44069409)

Turbines don't compress air. Turbines convert potential energy in the air into mechanical kinetic energy, reducing total pressure. Compressors add total pressure, and... well... compress things.

They run a compressor (air pump) to generate high pressure air, which they then feed through the turbines. The turbines are physically attached to the rotors on the same disk, so there is no need for drive shafts, transmissions, or anything. GE did the same thing with the two contrarotating pusher props on their UDF back in the 80s. The trouble is that you need to have those turbines extract enough power from the air to run the rotors. They're not physically large, so they can't produce a lot of torque. They're limited in RPM by being directly attached to the rotors. Low torque times low RPM equals low power, too little power to drive the rotors. GE got away with it on their UDF prototype because the fan and turbines were much closer in diameter, thus the turbine could run at a much more favorable RPM.

Re:Something isn't adding up... (1)

b4upoo (166390) | about 10 months ago | (#44067429)

You are correct. The design sounds fishy. Just for a start why the heck would you put an air intake at the rear of the bird? Even if the machine has an 80 mph top end the ram air effect of a forward mounted air intake would be a huge advantage. Maybe they should take a clue from every jet fighter ever built and notice not a single design mounted the air intake in the tail. Designs like that should be designed with deep thinkers like Glen Beck signing the blue prints.

Re:Something isn't adding up... (1)

fahrbot-bot (874524) | about 10 months ago | (#44068049)

Just for a start why the heck would you put an air intake at the rear of the bird?

I'm not an aviation engineer, but wouldn't a rear-facing inlet reduce the likely hood of something, like an actual bird, getting sucked in?

Re:Something isn't adding up... (0)

Anonymous Coward | about 10 months ago | (#44068325)

For airplanes its certainly a problem, for helis not so much, usually air inlets are high near the rotor, due to heavy rotor downdraft only way for a bird to get into inlet is to first go through rotor. Spray of minced meat is not as harmful for turbines as intact birds.

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44069297)

No. Ram air at 80mph will not produce any meaningful difference. You're talking about maybe one psi difference between forward facing and rearward facing at that speed, while your compressor is going to have to be producing several tens of psi to power that rotor. The only value of ram air on a car is that you're feeding the engine fresh, cool air, as opposed to air entering through the grille and heated by the radiator.

Re:Something isn't adding up... (1)

MiG82au (2594721) | about 10 months ago | (#44069729)

Or you could just go calculate it with 1/2 rho v^2 and realise it's 0.1 psi...

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44069879)

Yeah, or look it up in the table in the back of one of the books on my shelf behind me, but it's morning, and my first day off in two weeks. Forgive my laziness.

Re:Something isn't adding up... (0)

Anonymous Coward | about 10 months ago | (#44067467)

Interesting observation, the heat produced from turbo/super chargers are extreme. But they company has yet to build a full sized heli, which is interesting. I love how they claim it works with a "model". When you compare flying it in short bursts, with a long flight, that will obviously show the flaws with this idea. Not sure to what extent there testing is, but it seems they have done long test flights (or I would at least hope so)

Re:Something isn't adding up... (1)

drinkypoo (153816) | about 10 months ago | (#44069267)

According to the article, the air is compressed, then heated by the engine's cooling system, then mixed with exhaust gasses, and the resultant flow into the turbine is only 100C? Something doesn't seem right here

IANAP[hysicist] and I'm bad with math so I'm possibly not even capable of doing the numbers, but gases do cool when they expand. If they're letting them out through some kind of control aperture, then perhaps the flow is only 100C at the point at which it reaches the turbine blades. Or maybe that's a lot of bunkum, because as I said, I haven't done the numbers. However, you don't seem to have accounted for this in your complaint.

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44069427)

Huh? By expanding and cooling, you mean decompressing. You're right back at the same point I described, too low of pressure ratio above atmospheric to do anything useful.

Re:Something isn't adding up... (2)

dywolf (2673597) | about 10 months ago | (#44070927)

This is actually not new technology.
In fact, most turboshaft helicopters already use this sort of system, eg: Hueys and Cobras (my background)

What you have here is a non-physical or indirect link between the engine and rotor transmission.
In some helicopters the link is direct or physical. IE, the transmission gearbox is directly attached to the engines output shaft, just like a car with a direct connection. This means the transmission must input must therefore spin at the same RPM as the engines output.

What they have done is the helicopter equivalent of the torque converter in your car. The rotor transmiion and gearbox is NOT directly connected to the engine's output shaft.

So how this works is you have a turbine engine. A jet engine basically. It produces a jet exhaust. What Hueys and Cobras, and Im sure some other types as well, what they do is rather than put the xmission gearbox directly on the engines output shaft is they isntead have a seperate unconnected turbine in the exhaust stream. Thus, the hot, compressed and fast flowing exhaust turns this second turbine. And it's this 2nd turbine that is connected to the xmission gearbox and thus to the rotor. This is essentially like the torque converter now common in cars.

By not having a direct link you do reduce mechanical complexity, as well as increase reliability. The 2nd turbine, the one driven the by the exhaust, can be keyed differently, thuis naturally resulting in a lower RPM than the engines axial shaft, and without using a gearbox in between to step down the RPM. Thats where the reduced complexity and higher reliability come from.

In the case of Hueys/cobras we're talking about stepping down from a jet turbine (say, 40k RPM) to a Rotor speed of say ~120 RPM. That kind of gearboxing is going to have high streess, high wear and tear, be extremely hot, and need careful babying. So instead we put this power turbine in the exhaust stream and design it so it naturally spins at a slower speed for a given flow rate, achieving the same effect as a gearbox. Now this is obviously still going to be a higher RPM than the final Rotor output, so theres still gearboxing and further reduction (say ~2k to 120 rpm). But the big jump from the engines axial RPM is accomplished via exhaust air flow.

In the helo community the engine is thus commonly known as the "Gas producer" (Ng, rpm of the gas producer). So what they've done here is replace the jet engine as the gas producer with an air compressor, to achieve the same goal: air to drive a Power Turbine that actualy moves the rotor.

Also note, for space sake the two turbine shafts, engine and power, are usually coaxial, hence the name: turboshaft.
Compared to jet engine with a propellor directly attached via gearing, which is the turboprop.
(lot of words, but now you know a whole lot more about modern helo engines)

Re:Something isn't adding up... (1)

dywolf (2673597) | about 10 months ago | (#44070941)

when i say "some helicopter have a direct link" its referring more to much older designs using piston engines.
i dont know of any turboshaft powered helos that have a directly linked xmission....since as stated thats wher ethe name of the powerplant type comes from!
so..there.

Re:Something isn't adding up... (1)

dywolf (2673597) | about 10 months ago | (#44070987)

damn we need an edit button. "and im sure some other types as well"...dont know why i typed that. damn stream of thought typing.

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44071455)

I understand how a helicopter engine works (no offense taken by the explanation). My problem with this design is two fold.

First, according to the article, the air they're feeding into the turbine is around 100C, and they even made a point of saying it was low temperature so no special cooling measures would be needed. In a turboshaft engine, the exhaust coming out of the gas turbine into the secondary is closer to 1000C. Temperature and pressure are intimately linked. You can't have one without the other (at least not without additional cooling stages), and if the combined flow from the compressor, engine cooling, and engine exhaust is only 100C, there's not going to be anywhere near enough useful energy in that flow to drive a turbine powerful enough to keep it aloft.

Second, they've got their turbines connected directly to the rotors, with no gearbox. Those turbines look like they're going to be around a foot in diameter in the full scale aircraft, and they're operating with no mechanical advantage at just a few hundred RPM. There's no way they're going to get enough torque out of those turbines with that short of a moment arm to drive the rotors. That's the whole reason we use gearboxes. GE got away with this same design in their UDF prototype because the difference in diameter between the propeller and turbine was much lower, plus they used seven stages for each propeller to do it. Here, I doubt if they would have room for more than two, and there's still the issue of finding enough room to turn the exhaust flow back down and out the bottom of the shroud.

Re:Something isn't adding up... (1)

dywolf (2673597) | about 10 months ago | (#44073003)

i can explain the mechanics of the engine, but the physics/thermodynamics of the heat and flow etc is not something im expert on so i actually cant really speak to how they could get it working at 100C, though i do recognize that its unusually "cool". i guess it would just depend on how much energy they need to drive the rotors themselves, and i'd just be guessing.

mechanically, it did seem odd that the power turbines are seemingly integral to the rotor mast/housing, no reduction gearbox. as for getting rid of it (the air), i wondered if they were maybe bleeding the air into the blades and out the tips once it was used.

Re:Something isn't adding up... (1)

wagnerrp (1305589) | about 10 months ago | (#44074197)

one reason jets are hot is because its a consequence both of the required pressures need to both keep the reaction self sustaining and not escaping out the front (essentially a pressure wall from the compresor stage so it can only go rearward), and combustion itself.

Really, it's all due to efficiency. The higher your pressure ratio, the higher the thermodynamic efficiency of your cycle. The trouble comes down to scaling issues. In order to reach high pressure ratios, you necessarily end up with high temperatures, those high temperatures require exotic mechanisms to keep the hot sections within reasonable operating conditions, and those exotic mechanisms require lots of room to implement. The largest aircraft and industrial gas turbines run upwards of 40:1 pressure ratio. Turboshaft engines for helicopters are usually closer to 10:1. Little RC jet engines often run at an awful 3:1 or so.

For comparison, gasoline and diesel engines typically run around 25:1 and 75:1, respectively. Note that the rise in temperature during compression causes a feedback that further increases pressure, so those numbers are going to be much higher than the more commonly used compression ratios. That also explains why diesels operate at so much higher thermodynamic efficiencies than gasoline and turbine engines, even though gasoline and turbine engines use inherently more efficient cycles.

the physics/thermodynamics of the heat and flow etc is not something im expert on so i actually cant really speak to how they could get it working at 100C

A good compressor stage is going to manage around 1.5:1 pressure ratio. It's easier to pull energy out than to put it in, so a good turbine stage might do 2:1 pressure ratio, and you're likely going to have at least two stages for the power take off on a turboshaft. At 100C, assuming adiabatic compression from atmospheric, you're looking at around a 2:1 pressure ratio, but that's not what happened here. The air was compressed, and then heated by the engine, in effect taking the place of the combustion chamber. Chances are the compressor is running well shy of 1.5:1. Now if you don't have the pressure (or velocity) to reach your torque requirements, you can always make up for it in volume, but the turbine disk in that nacelle on top just doesn't have the area to do that either.

Re:Something isn't adding up... (1)

dywolf (2673597) | about 10 months ago | (#44073051)

(really really need an edit button)
although...one reason jets are hot is because its a consequence both of the required pressures need to both keep the reaction self sustaining and not escaping out the front (essentially a pressure wall from the compresor stage so it can only go rearward), and combustion itself. the heat itself isnt necesarily required, it's "just there". so if they could get the required pressures and airflow for their power turbines to work without as a much heat, so much the better for them i guess.

Don't sound terrible new or efficient to me (1)

WegianWarrior (649800) | about 10 months ago | (#44067593)

An engine drives a compressor, heat is added to the compressed air and it's used to spin a turbine that isn't hooked up to the compressor? In that case it's the bastard child of a motorjet [wikipedia.org] and a turboshaft [wikipedia.org] - and looking at the temperatures involved it's unlikely to be terrible thermally efficient. They might be able to coax enough power out of it to drive a small chopper, and it might be cheaper and/or easier to maintain than a pure turboshaft engine... but somehow I think this will vanish into obscurity pretty fast.

TL:DR version: Two old ideas mashed together, unlikely to be 85% efficient

Prototype Video is Flakey (1)

edelbrp (62429) | about 10 months ago | (#44068133)

It looks and sounds like the 1/5 scale prototype is electric and very crudely controlled... only 8 throttle settings? The blades are counter rotating, so no tail rotor is needed except to rotate the craft (which it can't, it seems). Any cyclic adjustments to one of the lift rotors looks like it could cause a catastrophic collision with the other. It seems to me the demo in the video was basically completely uncontrollable except for the throttle.

I don't think this could really be a real scale prototype let alone a real possible model of a full scale craft that could work.

Re:Prototype Video is Flakey (1)

Ksevio (865461) | about 10 months ago | (#44069483)

The prototype also stayed within a foot of the ground which makes me wonder if it can even fly or was just able to hover. Most toy electric helicopters flying around in the mall are more impressive than this demo.

Re:Prototype Video is Flakey (1)

Anonymous Coward | about 10 months ago | (#44070579)

I own a counter rotating RC helicopter [amazon.com] . The GP post implies they can't turn, but they can, by varying the relative speed of the blades. It's really fun to fly. Hard, because it's so light any draft moves it fast. Flying it around the house is like paying a very complex video game. It's my first RC aircraft and well worth the $50. You correctly noted that the toy model didn't get more than a foot off the ground. They are using the ground effect [rchelicopterfun.com] . It allows you to hover with less power. It feels like there's a bubble of air under the model. Flight is also super stable with ground effect, because the lower you get the less lift you need. It's super fun to zip around the house using ground effect, because you can ignore lift and just skate around on a cushion of air.

It's actually old tech (1)

Jesrad (716567) | about 10 months ago | (#44068609)

There is hardly anything new in here to see, except maybe for a new take on jet tip rotor.

Jet-tip rotor helicopters are old technology, especially in France where the only successful model of such an helicopter, the Sud Ouest SO.1221 "Djinn" [wikipedia.org] , has been designed and commercialized over 50 years ago.

Jet tip rotors had a lot of issues, from the thrust-control, failure-mitigation and temperature-control mechanisms that have to fight the huge centrifugal force at the end of blades, to the poor autorotation performance and, mainly, to the difficulty of designing reliable multi-engine configurations which pretty much limits this technology to small helicopters (and over-land operation only). Additionnally, a lot more power is lost in the compression and transport system than in a conventional gearing system, which eats away quickly any weight-saving. For one, the Djinn had double the fuel consumption of a similar-size chopper. That's why they disappeared.

Here, the Sagita's description from the article claims that the two contrarotating main rotors are driven by a pair of turbines which are driven by a compressor which is itself driven by the main engine and its turbine. That makes it a hybrid between a conventional turboprop helicopter where a turbine in the engine drives the main rotor through a gearbox, and a jet tipped helicopter where the engine's turbine drives a compressor which blows air (usually with added combustion, as in the ramjet-tip configuration used on the Djinn) through the rotor's blade tips.

In a way, it can be understood as the application to helicopters of a somewhat modern-ish turbopropeller tech used in airplanes, where different sets of turbines each drive the main propeller and the engine's inner compressor at different rotation rates. However, in an airplane this design is streamlined and integrates in a very straight-forward way inside the engine because the main propeller IS the "additional compressor", whereas on the Sagita, the main rotors are not aligned nor even integrated with the main engine, requiring a whole compressor added to the mix. That implies more mass, more complexity and some transmission losses that mitigate the efficiency of the whole thing, so I doubt their efficiency gains figures.

The very definition of vapor ware (2)

bdwoolman (561635) | about 10 months ago | (#44068707)

FTFA "Though a full-scale working prototype is yet to be built, Sagita claims to have proven the concept (albeit with an electric motor) with a one-fifth scale model. You can see the video of it in flight below.">

And it actually uses vapor. But not the good kind.

As for me? I am developing a teleportation device. I don't have a working prototype, but I have a proof of concept using my automobile. Any VCs out there can reach me on my FTL communicator. Also in development.

well... (0)

Anonymous Coward | about 10 months ago | (#44070691)

Technically all ICE and turbines are hot air powered.

Constant backwards thrust (0)

Anonymous Coward | about 10 months ago | (#44071629)

it looks like the intake is providing significant backwards thrust... at least of the 1/5th scale model.
Anyone know how much energy would be lost by ducting the intake 180 degrees?

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