A vehicle which breaks the laws of physics...

[Screwdriver]

I'm with @PhillipM on this one. If they are regular wings then that's a very good point regarding the balance between the wings with all that lift and your control surfaces. I got kicked out of RAF pilot training ("not officer material" who'da thunk it) and lost interest in flying but I assume the balance would be drastically off in, lets be honest, a pretty difficult situation to start off with

I much prefer realistic challenges though because if you say "assume the plane has been designed for use in space", I think I might actually explode.

A scientific theory is defined not by what you can prove but what may be disproven. The amazing thing about Blackbird is you actually did it and you made it work. If you're going to build an aircraft for use in zero g, I'm in.

Until then...

 

[spork]

I'm with @PhillipM on this one. If they are regular wings then that's a very good point regarding the balance between the wings with all that lift and your control surfaces. I got kicked out of RAF pilot training ("not officer material" who'da thunk it) and lost interest in flying but I assume the balance would be drastically off in, lets be honest, a pretty difficult situation to start off with

I much prefer realistic challenges though because if you say "assume the plane has been designed for use in space", I think I might actually explode.

A scientific theory is defined not by what you can prove but what may be disproven. The amazing thing about Blackbird is you actually did it and you made it work. If you're going to build an aircraft for use in zero g, I'm in.

Until then...

I'm not suggesting we design a special plane. I'm just talking about a regular old plane. But at least I think I see what you're getting at now. Nominally the airfoil and/or incidence will have the wing lifting and the tailplane pushing down. That will lead to a nose-up pitch moment (in the frame of the aircraft). But the center of mass is so close to the center of pressure that I don't think it would take more than a touch of down elevator to balance.

But that's not the fun one. It gets way more interesting with a helicopter.

 

[AVI_8]

Aircraft can fly quite happily in a zero gravity situation, they behave exactly the same, if you apply left aileron the aircraft will go roll left, if you apply rudder the aircraft will yaw in the direction of applied rudder, the way the aircraft flies is exactly the same in zero gravity as it does pulling 6G positive, or in level flight.

Look at what an aerobatic aircraft does, you can go from +10 to -8 G and that’s pretty common on a descent sporty aircraft.

A party piece I used to do was to put my map in the rear seat, pitch down to a high speed then pitch up to around 45 degrees, then apply enough forward pressure on the yoke to get no lift, basically no gravity, or actually a tiny bit of negative G, the map would lift off the seat, start to float then as the aircraft started to descend still with 0 G it would float forward and with a bit of practice I could make it settle on the dash coaming, its called a parabolic loop, it’s how they train astronauts to experience no gravity, though they do it in a wide body aircraft and lasts around 30 seconds whereas in a small aerobatic aircraft it only lasts around 8 seconds due to the lower speed.

Landing would be fun though in this hypothetical zero gravity situation, trying to slow down for starters.

A narrow body jet for example, like a Boeing 737 or an Airbus 320, with normal gravity if you’re flying level at 4000 ft and doing 330 knots and then close the thrust levers maintaining level flight it takes around 8 nautical miles just to slow down to the point that you can extend the first stage of flaps which is around 220 Knots so that’s 8 miles just to lose 110 knots, with no induced drag in this zero gravity situation induced drag being the by product of lift slowing down to get below flap limiting speed may not even be possible due to the residual idle thrust from the engines.

With a helicopter, if it’s sitting on the tarmac in a zero gravity situation as soon as you released the rotor brake the rotors would start to spin and the helicopter would start to also spin in the opposite direction, you’d get dizzy very quickly before the helicopter would end up on its side with bits of rotor blade flying off in all directions.

 

[PhillipM]

I don't think you'd have too much issue with a heli in terms of takeoff - you only need to barely spin up and your tail rotor has more than enough authority, that's no different to normal.
Your issue is you tilt the disc and pitch the heli to get forward thrust which is a reaction force against the weight of the body - it would really depend on the heli, but I would say you'd be fine so long as you didn't go too nuts with accelerations. If you have negative prop on the rotor then you'd be fine anyway if it inverts just invert the rotors. Could lead to some fun stunts.

 

[spork]

Aircraft can fly quite happily in a zero gravity situation, they behave exactly the same...

For an airplane, I agree. How about a helicopter?

A party piece I used to do was to put my map in the rear seat, pitch down to a high speed then pitch up to around 45 degrees, then apply enough forward pressure on the yoke to get no lift, basically no gravity, or actually a tiny bit of negative G, the map would lift off the seat, start to float then as the aircraft started to descend still with 0 G it would float forward and with a bit of practice I could make it settle on the dash

I used to do the same thing with my wallet. But I started with it on the dash. A couple of times I did it with myself by not using the seat belts.

With a helicopter, if it’s sitting on the tarmac in a zero gravity situation as soon as you released the rotor brake the rotors would start to spin and the helicopter would start to also spin in the opposite direction, you’d get dizzy very quickly before the helicopter would end up on its side with bits of rotor blade flying off in all directions.

Why would the helicopter start to spin? You still have complete control of the tail rotor.

 

[spork]

I don't think you'd have too much issue with a heli in terms of takeoff - you only need to barely spin up and your tail rotor has more than enough authority, that's no different to normal.
Your issue is you tilt the disc and pitch the heli to get forward thrust which is a reaction force against the weight of the body - it would really depend on the heli, but I would say you'd be fine so long as you didn't go too nuts with accelerations. If you have negative prop on the rotor then you'd be fine anyway if it inverts just invert the rotors. Could lead to some fun stunts.

I don't want to give it away just yet, but the heli relies on gravity in a way that a plane does not.

 

[AVI_8]

I don't think you'd have too much issue with a heli in terms of takeoff - you only need to barely spin up and your tail rotor has more than enough authority, that's no different to normal.
Your issue is you tilt the disc and pitch the heli to get forward thrust which is a reaction force against the weight of the body - it would really depend on the heli, but I would say you'd be fine so long as you didn't go too nuts with accelerations. If you have negative prop on the rotor then you'd be fine anyway if it inverts just invert the rotors. Could lead to some fun stunts.

I would disagree, though I am not a helicopter pilot, with zero as in no gravity the helicopter would start to spin at almost the same rate as the rotor blades, yes the tail rotor would start to spin more quickly than the main rotor but by the time you’ve dome a couple of revolutions the skid would dig in and you’d be on your side, long before the tail rotor became aerodynamically efficient enough to help you

 

[AVI_8]

For an airplane, I agree. How about a helicopter?



I used to do the same thing with my wallet. But I started with it on the dash. A couple of times I did it with myself by not using the seat belts.



Why would the helicopter start to spin? You still have complete control of the tail rotor.

With no gravity there would be no friction on the skids, when the rotor starts to spin with no friction on the skids the helicopter would start to spin, the main rotor would need to be at a reasonable speed before the tail rotor would become efficient enough. We’re talking hypothetical here but I’ve seen it go wrong with helicopters even in real life, when it goes wrong it goes wrong very quickly

 

[AVI_8]

I used to do the same thing with my wallet. But I started with it on the dash. A couple of times I did it with myself by not using the seat belts.

You’re totally correct of course, a few glasses of wine and a 20 year period since I‘ve flown a light aircraft, start on the dash and it lands behind you.

By the way I love what you’re doing, but the physics is above my understanding, I’d love to see it in action.

 

[spork]

With no gravity there would be no friction on the skids, when the rotor starts to spin with no friction on the skids the helicopter would start to spin, the main rotor would need to be at a reasonable speed before the tail rotor would become efficient enough.

You make an interesting point. Initially the tail rotor is trying to counter the acceleration of the main rotor. In flight it's just trying to counter the drag of the main rotor at constant speed. So let's spot you that one and either start the helicopter already "in flight", or hold it down until the rotor is up to speed.

the helicopter would start to spin at almost the same rate as the rotor blades

But the helicopter is a LOT heavier than the blades. So conservation of angular momentum would suggest that the helicopter would rotate at a small fraction of the rotor RPM - even without the tail rotor to help.

But think of the balance of forces in hover. Things then get very interesting without gravity. I'm trying to get one of the Youtubers to take this one on.

 

[spork]

You’re totally correct of course, a few glasses of wine and a 20 year period since I‘ve flown a light aircraft, start on the dash and it lands behind you.

By the way I love what you’re doing, but the physics is above my understanding, I’d love to see it in action.

Thanks. I'm actually happy to go deep on the physics, but I get no enjoyment by talking over anyone's head. I actually prefer the challenge of making it clear to people that don't have the same background. So please feel free to jump in with questions.

 

[AVI_8]

But the helicopter is a LOT heavier than the blades. So conservation of angular momentum would suggest that the helicopter would rotate at a small fraction of the rotor RPM - even without the tail rotor to help.

Yes that’s true but with no gravity, weight plays a much lesser part.
so the balance of forces in the hover, you have lift from the rotors and a helicopter which has no weight, my question to you is do the rotors on a helicopter produce lift even with the collective fully lowered, like I said earlier I have never flown a helicopter and haven’t studied the physics, if the rotors can’t be at a pitch where they don’t produce any even a small amount of lift then the helicopter would be in a continuous climb, it would continue to climb, unless at zero collective there’s no lift, is that what you mean

The balance of forces in the hover is that weight equals lift
And if there’s no weight even the slight lift on the collective ….. Climb rate! But descent could be a different story, yes push on the cyclic and the houses get bigger, but then how do you slow down

 

[spork]

Yes that’s true but with no gravity, weight plays a much lesser part.

When I'm talking about the heli spinning on rotor start-up, I'm only referring to the inertial mass of the rotors and heli - not their weight. Since the heli has so much more mass, it would spin proportionately slower than the blades.

so the balance of forces in the hover, you have lift from the rotors and a helicopter which has no weight, my question to you is do the rotors on a helicopter produce lift even with the collective fully lowered

Depends on the heli. Let's use a heli that lets you run the collective a little negative. We want to be able to produce lift either up or down.

The balance of forces in the hover is that weight equals lift

It's much more than that. I'll jump ahead...

In normal hover, the lift from the main rotors = the overall weight of the heli.
But that puts a torque on the heli - so we add a tail rotor to counter that torque.
But the tail rotor puts a net side load on the heli - so we then tilt the heli just a bit to counter that side load. You can see it if you look at a heli in hover.
But that slight tilt is the sum of the lift and the side load.
With no gravity, there's no weight. So instead of a slight tilt to the side, the heli would have to roll 90 deg to the side to counter a pure side load.
But now we've also rolled the side load by 90 deg, so we'd have to roll the heli another 90 deg.
We'll be continuously rolling the heli just to chase the side load of the tail rotor.

The same happens for translating the heli. We tip the main rotor forward just a bit to go forward. Now our main rotor produces enough lift to hold the heli up, and a bit of forward force. But with no weight, we need no lift. So if I want to go forward, I have to pitch 90 degrees "forward" (i.e. nose down).
The whole thing will be a nightmare.

 

[AVI_8]

Haha, thank heavens for gravity then !
Yeh now that you’ve mentioned that I know what you mean, a heli is always one skid down in the hover, that’s where it can go wrong with an inexperienced pilot, whereby if that lower skid touches the ground first and they’ve not anticipated problems in windy conditions.
I‘d love to fly a heli but at over £300 an hour I’ll need a lottery win its not as though I don’t get to see the ground from the air for free just now.
I had a passenger ride in a single Squirell with a mad man at the controls, I love Aeros in an aircraft but a stall turn at 200ft in a heli just seemed wrong, with hindsight it was great fun though !

 

[spork]

I've got a little heli time and a ton or R/C heli time. I'm trying to get one of the simulator companies to modify their program so I can set the gravity parameter so I can do this for a youtube video. It will be interesting to watch it having to tilt more and more to hover until it no longer works.

One company set me up, but it turns out their gravity parameter is ignored.

I'm hoping maybe I can talk RealFlight into it.

A few weeks ago the wife and I went to Churchill Canada to see the polar bears. We took a 2.5 hr heli tour that was spectacular. I'd love to get an ultralight heli - or at least one of those tiny single-place helis.

 

[AVI_8]

There’s a guy in the UK, his name is Mark Evans, he’s done a few TV series building many things, he did an awesome Land Rover, and a race car, then self built aircraft and the last one I saw he built a self build helicopter. All documented on TV series.
I’d love a project like that,
I’ve a colleague at work just now who‘s nearly finished an RV aerobatic aircraft, very lightweight with a 180 Lycoming and a wobbly prop. That should provide a lifetime of fun!

 

[spork]

I’ve a colleague at work just now who‘s nearly finished an RV aerobatic aircraft, very lightweight with a 180 Lycoming and a wobbly prop. That should provide a lifetime of fun!

I've got a buddy with an RV-8. We've done some aerobatics in it. Great little plane.

My day-to-day ride is a hang glider and a paraglider.

 

[AVI_8]

Actually I’ve just watched the video of you at the start of this thread, I hadn’t seen it before, that’s pretty groundbreaking what you did, and I can see the physics behind it, We’ll done you!
I‘m not sure where or how you can take that technology and understanding forward, but to add forward thrust from a tailwind, you’ve a very clever prop design there by the looks of it, where do you actually take it from there?

Yeh a hang glider is something I’ve thought about before or a microlight, inexpensive flying!

 

[spork]

Actually I’ve just watched the video of you at the start of this thread, I hadn’t seen it before, that’s pretty groundbreaking what you did, and I can see the physics behind it, We’ll done you!
I‘m not sure where or how you can take that technology and understanding forward, but to add forward thrust from a tailwind, you’ve a very clever prop design there by the looks of it, where do you actually take it from there?

Yeh a hang glider is something I’ve thought about before or a microlight, inexpensive flying!

I don't really plan to do anything with it. It was originally just intended as a brain teaser. But it got out of control. The deniers outnumber the believers by about 1000:1. So we decided to build it.

 

[AVI_8]

Well jeez, well done you for taking that huge financial cost to firstly attempt to do it and then to prove what you did worked as you calculated, that’s impressive stuff, I wouldn’t have believed it if I hadn’t seen it! Nice one!