Helicopter blades scaling Versus Mass...

[Spacescifi]

Just wondering, if one attempted to make a massive helicopter... on par with a mass of oh... 300 tons, could it be made to look just like a regular helicopter but scaled up in size?

Or will the blades be so long that it will no longer look like a scaled up helicopter but more.... like a freak of engineering needs?

 

Spoiler

Yes... this is for scifi but not what you may think.

 

I was thinking of large thick disc shaped SSTO, which used the famous scifi shield tech to make and extend long blades made of... essentially forcefield.

Like the trope scifi shields, the forcefield blades are nearly unbreakable and can take more heat than normal matter before failing.

 

The cool thing is that the blades weigh virtually nothing and they can be extended or retracted back inside the ship's central roof hub ports.

So what you have are glowing plasma-like blades of forcefield that weigh virtually nothing.... taking the place of normal helicopter blades to do something extraordinary... lift a 300 ton disc SSTO.

 

 

Bonus question: Would the height ceiling of turbine helicopters (25,000 feet)  be sufficient to be much in the way of propellant savings, if the disc retracted the forcefield blades and flipped over to use rear rocket engines to reach orbit from 25,000 feet?

 

Or not much of a propellant savings?

 

[cubinator]

Maybe it would look more like a Ferris wheel on its side, a huge circular structure with holes in it, perhaps even kind of like a cheese grater.

[kerbiloid]

What would a 300 t helicopter for the Earth look like? The heaviest one is 60 t (Mi-26).

Probably a pentagram of five Mi-26s, connected together with struts.

Like the Mi-32 project
 

Spoiler

***
Back to the Mars.

A flying pack of 150 000 Ingenuities (2 kg) with a cabin hanged below on strings.

A forcefield variant: like the Jedi lightsabres but longer.

Edited August 13, 2022 by kerbiloid

[Shpaget]

Helicopter blades are constrained by the speed of sound. You don't want the tips to be faster, since a lot of aerodynamics bresk down above Mach 1.

[cubinator]

1 minute ago, Shpaget said:

Helicopter blades are constrained by the speed of sound. You don't want the tips to be faster, since a lot of aerodynamics bresk down above Mach 1.

Well they don't break down above Mach 1, they just change. The issues arise at the transition point near Mach 1. You might be able to make the wing geometry work out so that the part of the wing near M=1 is very narrow. Most airliners today fly with wings designed to minimize the negative effects of transonic flight and fly near Mach 1 (swept wings, adjusted thickness profile...) You might be able to apply some of these to a rotating airfoil

[Meecrob]

25 minutes ago, cubinator said:

Well they don't break down above Mach 1, they just change. The issues arise at the transition point near Mach 1. You might be able to make the wing geometry work out so that the part of the wing near M=1 is very narrow. Most airliners today fly with wings designed to minimize the negative effects of transonic flight and fly near Mach 1 (swept wings, adjusted thickness profile...) You might be able to apply some of these to a rotating airfoil

This "creation" would still have to be like a dodecacopter to lift that much. I can't imagine the transmission system since in an engine out situation, all rotors are geared together so there is equal (but lesser) lift.

Edited August 13, 2022 by Meecrob

[Nuke]

swept wings on a helicopter rotor seem like they would be rather unwieldy. blade would curve would act as a big off axis flap which might put too much stress on the swashplate linkages. you can bulk those up of course but that is extra weight. there is also the matter of the blades holding their shape with the centrifugal forces. i think most helicopter designs use that to their advantage to keep the blades in tension and less likely to flex in unpredictable ways. curved rotors pretty much invite that. 

[razark]

You propose magic helicopter force blades.  Why would you worry about dragging reality into it?

If you want an SSTO in scifi, just write it into the story, and skip the details of if it would actually work.  Of course it works, because it's used in the story!  If it didn't work, it wouldn't be in the story!

A rocket powered SSTO?
    Use it, because it fits the story.

A helicopter SSTO? 
    Write it in, because it fits the story.

A jet powered SSTO?
    Why not, if it fits the story?

A human sacrifice powered SSTO?
    Sure, because it fits the story.

A bunch of birds tied to the outside of the craft to lift it into space, which makes it an SSTO because anything in space is automatically in orbit?
    Sure, who the hell cares, it's scifi and whatever BS explanation you make up is what works because it's your story and that's how it works!

A space wizard powered SSTO?
    Sure, because it fits the story.

A completely unexplained system that is just an SSTO because the story needs an SSTO?
    Sure, because it fits the story.

 

On 8/12/2022 at 9:39 PM, Spacescifi said:

like a freak of engineering

It's scifi.  Who the hell cares if it's a freak of engineering?  Does it fit the story?

Edited August 14, 2022 by razark

[KSK]

@Spacescifi

You may already be aware but the Roton might be of interest here, although admittedly, it's more of a freak of engineering needs than a regular helicopter. From the article:

"Bevin McKinney's initial concept was to merge a launch vehicle with a helicopter: spinning rotor blades, powered by tip jets, would lift the vehicle in the earliest stage of launch. Once the air density thinned to the point that rotary-wing flight was impractical, the vehicle would continue its ascent on pure rocket power, with the rotor acting as a giant turbopump.[5]

Calculations showed that the helicopter blades modestly increased the effective specific impulse (Isp) by approximately 20–30 seconds, effectively only carrying the blades into orbit "for free." Thus, there was no overall gain from this method during ascent. However, the blades could be used to soft land the vehicle, so its landing system carried no additional cost."

The Roton had (or was intended to have) a modest 3.2 tons of cargo, carried by a 181.4 ton (fully fueled) vehicle.

On the whole, I would echo @razark's comment. Your forceblade SSTO sounds cool, so just run with it. I'm reminded of the ornithopters from Dune - giant metal dragonflies are about the least practical aircraft I can imagine but i) they looked great on the eventual big screen and ii) they really got across the notion that Dune is a far-future Clarketech setting where technology is sufficiently advanced that mundane practicality can take a back seat to rule-of-cool.

Edited August 14, 2022 by KSK

[Nuke]

16 hours ago, razark said:

A human sacrifice powered SSTO?
    Sure, because it fits the story.

i think you would get higher specific impulse if you only sacrificed virgins. now if only you could find one. 

[Spacescifi]

45 minutes ago, Nuke said:

i think you would get higher specific impulse if you only sacrificed virgins. now if only you could find one. 

Ultra-conservative high control group religions that use the BITE model of control?

Believe me... I know lol.

[cubinator]

On 8/13/2022 at 8:22 PM, Nuke said:

swept wings on a helicopter rotor seem like they would be rather unwieldy. blade would curve would act as a big off axis flap which might put too much stress on the swashplate linkages. you can bulk those up of course but that is extra weight. there is also the matter of the blades holding their shape with the centrifugal forces. i think most helicopter designs use that to their advantage to keep the blades in tension and less likely to flex in unpredictable ways. curved rotors pretty much invite that. 

My first instinct is to connect the tips of the blades with a big circle, sometimes you see this on toy spinners. It'd be bulky, but we're talking about something that's supposed to carry an enormous weight anyway. Maybe it'd end up being even closer to a solid disk than that. Especially since that ring is going to be under extreme and random stress from interacting tip vortices. I know helicopter airfoils are typically thicker than fixed wing ones to increase strength.

Edited August 15, 2022 by cubinator

[kerbiloid]

2 hours ago, Nuke said:

i think you would get higher specific impulse if you only sacrificed virgins. now if only you could find one. 

(An Orion tungsten joke is with great regret skipped here).

19 hours ago, razark said:

A human sacrifice powered SSTO?

Why not? The Kethane mod was always providing this option.

Edited August 15, 2022 by kerbiloid

[Nuke]

1 hour ago, cubinator said:

My first instinct is to connect the tips of the blades with a big circle, sometimes you see this on toy spinners. It'd be bulky, but we're talking about something that's supposed to carry an enormous weight anyway. Maybe it'd end up being even closer to a solid disk than that. Especially since that ring is going to be under extreme and random stress from interacting tip vortices. I know helicopter airfoils are typically thicker than fixed wing ones to increase strength.

a helicopter rotor is a very dynamic thing. each blade can have a different pitch based on how its phased and the angle of the swash plate. like if you pitch forward the blade in the back will increase pitch while the opposite blade will decrease. assuming zero roll, the blade will actually flutter up and down as it rotates. tying the ends together would need to be done through a bearing system since the blades need to be free to pitch as needed for cyclic control. that would be straight forward for a straight wing (though adding a ring to that configuration would be completely unnecessary) but a wing with any kind of slope or curve the tip would follow an arc so big that any plausible bearing system would add a lot of drag.

i couldn't find any examples of swept chopper blades, though i saw several with a curve at the tips or some other wingtip geometry. i couldnt find a rotor head design  that could for example offset either the root or tip of the wing to create a swept blade. there are probibly structural or aerodynamic reasons why those dont exist.

[Spacescifi]

On 8/14/2022 at 1:12 AM, KSK said:

@Spacescifi

You may already be aware but the Roton might be of interest here, although admittedly, it's more of a freak of engineering needs than a regular helicopter. From the article:

"Bevin McKinney's initial concept was to merge a launch vehicle with a helicopter: spinning rotor blades, powered by tip jets, would lift the vehicle in the earliest stage of launch. Once the air density thinned to the point that rotary-wing flight was impractical, the vehicle would continue its ascent on pure rocket power, with the rotor acting as a giant turbopump.[5]

Calculations showed that the helicopter blades modestly increased the effective specific impulse (Isp) by approximately 20–30 seconds, effectively only carrying the blades into orbit "for free." Thus, there was no overall gain from this method during ascent. However, the blades could be used to soft land the vehicle, so its landing system carried no additional cost."

The Roton had (or was intended to have) a modest 3.2 tons of cargo, carried by a 181.4 ton (fully fueled) vehicle.

On the whole, I would echo @razark's comment. Your forceblade SSTO sounds cool, so just run with it. I'm reminded of the ornithopters from Dune - giant metal dragonflies are about the least practical aircraft I can imagine but i) they looked great on the eventual big screen and ii) they really got across the notion that Dune is a far-future Clarketech setting where technology is sufficiently advanced that mundane practicality can take a back seat to rule-of-cool.

 

On second thought... I really don't like the look of forceblades.... lightsabers are played out.

Plus... I reckon actual solid blades that can retract or extend may be more possible anyway.

How? Attribute it to advanced scifi tech... some kind of scifi metal that is normally liquid but can harden and stay solid when electric current is running through it.

 

So therefore when the blades retract they are actually returning to liquid form and going back into a tank, and when they extend it is the process in reverse.

 

In addition, the metal blades are very lightwight, which explains how they can extend long enough to lift a 300 ton SSTO.

I always prefer scifi tech that has mutiple applications, and this kind does.

Yet it does have one major drawback.

When current is applied, the metal will become virtually unbreakable in it's solid form, so long  forces coming upon it from the outside do not exceed the amount of electrical power flowing through the metal.

So what that means is if some force exceeds the amount of power going into your blades and hits them, that part of the blade hit will explode like a bomb.

Paradoxically this metal makes for kind of good ablative armor if it fails, but not the kind of thing thing spaceships usually want to use, since in order to be really effective it has to become an energy hog and really cannot afford to fail anyway.

Planetary military bases and industrial bases use though it though, since they have access to far more energy than spaceships have.

Edited August 15, 2022 by Spacescifi

[insert_name]

1 hour ago, Spacescifi said:

 

On second thought... I really don't like the look of forceblades.... lightsabers are played out.

Plus... I reckon actual solid blades that can retract or extend may be more possible anyway.

How? Attribute it to advanced scifi tech... some kind of scifi metal that is normally liquid but can harden and stay solid when electric current is running through it.

 

So therefore when the blades retract they are actually returning to liquid form and going back into a tank, and when they extend it is the process in reverse.

 

In addition, the metal blades are very lightwight, which explains how they can extend long enough to lift a 300 ton SSTO.

I always prefer scifi tech that has mutiple applications, and this kind does.

Yet it does have one major drawback.

When current is applied, the metal will become virtually unbreakable in it's solid form, so long  forces coming upon it from the outside do not exceed the amount of electrical power flowing through the metal.

So what that means is if some force exceeds the amount of power going into your blades and hits them, that part of the blade hit will explode like a bomb.

Paradoxically this metal makes for kind of good ablative armor if it fails, but not the kind of thing thing spaceships usually want to use, since in order to be really effective it has to become an energy hog and really cannot afford to fail anyway.

Planetary military bases and industrial bases use though it though, since they have access to far more energy than spaceships have.

with this you might as well just have it make the uber strong semiliquid metal into a space elevator and then retract it when the craft is at the top

[Spacescifi]

52 minutes ago, insert_name said:

with this you might as well just have it make the uber strong semiliquid metal into a space elevator and then retract it when the craft is at the top

 

Wow.... I had not thought of that... thanks lol.

 

But yeah... you are correct.

 

But for adventuring on strange new Earth worlds.... behold.... the mega-copter?

 

Wonder how it would sound?

 

Helicopter with bass?

[kerbiloid]

6 hours ago, Spacescifi said:

In addition, the metal blades are very lightwight, which explains how they can extend long enough to lift a 300 ton SSTO.

Metal blades are weaker than composite ones.

The classic An-2 with aluminium wings is a biplane. Some of its modern modification projects are monoplanes thanks to the composite wings. 

[mikegarrison]

16 hours ago, kerbiloid said:

Metal blades are weaker than composite ones.

That's not the way to look at it, usually.

All materials have their own properties, and generally you can (within limits) make a part of equal strength out of any of them. But that might mean the weight is different, or the thickness is different, or the durability is different, or the strength in tension is the same but in compression is different, or the cost is different, etc.

It's not that metal blades aren't strong enough. It's that they are heavier for the same strength, which means you need a more powerful engine, which is also heavier, which means you have a heavier helicopter, which means you need stronger blades, etc. etc.

Edited August 16, 2022 by mikegarrison