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HomeAircraftHelicopterHelicopter Main Discussion › What if you had a Heli (electric) on the space station, what would be the settings
02-10-2008 04:43 AM  10 years agoPost 61
Invrted1

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Cincinnati, Ohio

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I will have to settle for one of my little cheap Al Capone Blacks.

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02-10-2008 02:00 PM  10 years agoPost 62
tamro

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Fort Mill South Carolina USA

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Gravity in space
Most devices are propulsion driven in space. But there are some gravitational pull in space. After all, the Sun keeps the planets in order and orbit. The mass of the objects also play a rule in this situation. But to answer the question, maybe if you add a motor to the tail of the Heli, it would work. After all, the size of the motor will matter due to the reduction in gravity that could drive the tail to give a pitch.

HeliPoPTer

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02-10-2008 02:03 PM  10 years agoPost 63
GimbalFan (RIP)

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there are some gravitational pull in space.
A person (or an object) aboard an orbiting spacecraft experiences ZERO sensation of gravity. An orbiting object is constantly falling. If it's also at the right altitude to match its orbital speed, it and everything in it will never fall down -- it'll all just continue to fall around.
maybe if you add a motor to the tail of the Heli, it would work.
There'd be no detectable differences between a heli with a motor on its tail and an identical one with a belt or shaft driven tail.
the size of the motor will matter due to the reduction in gravity that could drive the tail to give a pitch.
Huh??

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-10-2008 02:18 PM  10 years agoPost 64
spork

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A person aboard an orbiting spacecraft experiences ZERO gravity. An orbiting object is constantly falling. If it's at the right altitude to match its orbital speed, it never falls down -- it falls around.
Sort of - but this is a complicated issue. The person "experiences" no gravity, not because there IS no gravity, but because he is freefalling - just like the first couple of seconds when jumping out of a plane. The gravity in low earth orbit is only something like 15% to 20% less than on earth actually.

On the other hand, everything in low earth orbit experiences "gravity gradient". There are two related effects (converging lines of attraction, and weaker gravity on your head than on your feet - if you're oriented feet toward earth) that can still be detected. If left on it's own, the shuttle would assume a nose toward earth, or tail toward earth, attitude, and would swing like a pendulum with a period on the order of 20 minutes because of gravity gradient. This is why they describe the on-board experiments as "micro gravity experiments" rather than zero-G experiments.

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02-10-2008 02:20 PM  10 years agoPost 65
GimbalFan (RIP)

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This is why they describe the on-board experiments as "micro gravity experiments" rather than zero-G experiments.
I'll stand -- uh... float -- corrected. But are you gonna sit there in your chair and tell me that at 230 +/- miles up a 6' astronaut can FEEL the difference in top to bottom gravity? 6' is 1/200,000th the height of 230 miles. Wouldn't that mean the difference is also on the order of 1/200,000?

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-10-2008 02:34 PM  10 years agoPost 66
spork

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But are you gonna sit there in your chair and tell me that at 230 +/- miles up a 6' astronaut can feel the difference in top to bottom gravity? 6' is 1/200,000th the height of 230 miles. Wouldn't that mean the difference is also on the order of 1/200,000?
That's why they call it "micro-gravity". The effect is very small, but not zero. I would doubt very much if the astronaut could detect it unless he could manage to keep his body straight for a long time without touching anything around him. If he were "below" the craft's C.G. he'd fall. If he were above, he'd move toward the "ceiling". And either way, his longitudinal axis would align itself toward earth.

There's something very very wrong with both of us. Up 'til 2:00 am, and up again at 6:00 am!? You must've had to get up for one of your morning high-test cigars!

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02-10-2008 02:39 PM  10 years agoPost 67
GimbalFan (RIP)

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Big Coppitt Key, FL

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You must've had to get up
Nah -- never got down. G'night.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-10-2008 03:09 PM  10 years agoPost 68
"Cam"

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UK

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Is that like the tennis racket effect?

Spork don't quote half a statement and say it's wrong.

SO what happens if you change the weight of a heli? Make it lighter, what would happen if you made it really light? Would there be a problem?

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02-10-2008 03:50 PM  10 years agoPost 69
Invrted1

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Cincinnati, Ohio

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Cam Uk:

If you go back through the thread a bit, you will see that a workable model has been described very well. Counter-rotating blades, with "tail" blades in front and rear, and very little pitch. I think what is most interesting is the flight method. Pointing the mainshaft where you want to go is a very unusual way to fly, but will get the job done very well. Sporks statements on this subject cleared it up for me.

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02-10-2008 04:13 PM  10 years agoPost 70
spork

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Mountain View, CA

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Is that like the tennis racket effect?
No, the tennis racket effect is a purely dynamic effect. It's based on the relative moments of inertia of the three body axes. The centripetal force will cause the body to want to "flatten out" in the plane of rotation.

Gravity gradient is a static effect. It also works on the different moments of inertia - but simply tries to align the long axis of the body in the direction of the gravity vectors.
Spork don't quote half a statement and say it's wrong.
Sorry, you'll have to take me back there. Where did I quote half a statement and call it wrong?
SO what happens if you change the weight of a heli? Make it lighter, what would happen if you made it really light? Would there be a problem?
A heli has to lean to the right in a hover (assuming clockwise spinning mains from above). For a given amount of torque on the main blades, that lean will have to be greater as the heli gets lighter. If the heli weighs nothing at all, there is no amount of lean that will counter the side-force of the tail. This is what leads to the continuous rolling of the heli trying to chase the side-force of the tail.

Obviously we can make very light helis that don't have this problem. That's because we have less and less torque as they get smaller. If we kept the main rotor diameter constant and the headspeed constant, while we made the heli lighter, we'd see this problem even though the torque on the mains would go down somewhat due to less pitch. At full headspeed, there's still plenty of parasitic drag on the mains to lead to this behavior.

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02-11-2008 07:28 AM  10 years agoPost 71
"Cam"

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UK

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A heli is ZeroG could fly with very, very low headspeed?

Would the phasing have to be changed? Is there a way to work it out?

Like the tiny lama helis their phasing is something like 30 degrees instead of 90 on the 'normal' helis.

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02-11-2008 07:32 AM  10 years agoPost 72
spork

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Mountain View, CA

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A heli is ZeroG could fly with very, very low headspeed?
Depends what you mean by "fly". In zero-G it could float motionless in the air with no headspeed at all. Beyond that the headspeed would be determined by how much acceleration you wanted. But as mentioned above, you'd have to redesign the heli somewhat to navigate in zero-G in any sort of practical way.
Would the phasing have to be changed?
The phasing wouldn't change. That's a dynamic issue related to gyroscopic precession. Works just the same in zero-G.

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02-11-2008 08:15 AM  10 years agoPost 73
"Cam"

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UK

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well no, helis with very light blades at low rpm have a different phase angles.

The question was how to work it out.

Could you imagine a heli in use on mars in the future?

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02-11-2008 08:31 AM  10 years agoPost 74
spork

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Mountain View, CA

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helis with very light blades at low rpm have a different phase angles.
You're right. I only meant to say that zero-G had nothing to do with phase angle. Disk inertia and RPM does.

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02-11-2008 08:37 AM  10 years agoPost 75
w.pasman

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Netherlands

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I think you need a chinook style with two rotor blades to avoid the tail rotor with all of its problems.

Even better would be a complete redesign of the heli, I think what you really want in this case is completely rotatable rotor head, so that you can aim the thrust vector in every direction as needed.

And you would need to re-learn flying, as you would need to tilt the heli the full 90 degrees forward to get forward movement, instead of just a few degrees.

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02-11-2008 02:28 PM  10 years agoPost 76
spork

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Mountain View, CA

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I think you need a chinook style with two rotor blades to avoid the tail rotor with all of its problems.
Yaw would still be a problem. Presumably you'd have counter rotating blades running at the same RPM. To yaw you'd give one more collective than the other, but that would cause as much pitch as yaw.

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02-11-2008 02:34 PM  10 years agoPost 77
Juggernaut

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Canada, Great White North

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Gyroscopic effect.
With the fly bar and/or the blade spinning causes a gyroscopic effect.
3 situations effect the heli

no Gravity
torque
Gyroscopic effect by main rotor and tail rotor

check out
http://www.youtube.com/watch?v=dCcf...feature=related



Finally learned to fly inverted, Helps if you stand on your head

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02-11-2008 03:09 PM  10 years agoPost 78
spork

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Mountain View, CA

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Gyroscopic effect.
With the fly bar and/or the blade spinning causes a gyroscopic effect.
3 situations effect the heli

no Gravity
torque
Gyroscopic effect by main rotor and tail rotor
I'm not sure I follow your point. In zero-G torque and gyrocopic effect would apply just as they do in 1 G.

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02-11-2008 05:58 PM  10 years agoPost 79
helimatt

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Lafayette, IN

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Guys, my read is that spork (Spock? ) is all over this one. If you had another tail rotor out front same distance from the c.g. (coincident with the main shaft), you'd be able to spool up zero collective and stay in one place. To accellerate in roll or pitch you'd want the same amount of cyclic input, because the heli has the same inertia to initiate or stop the rate of roll about any axis. "forward" flight, just like he says- very different from flying in gravity.

I think, once you got started you could do piroflips continuously without any collective inputs, other than small corrections to hold them stationary, or move the heli around while piroing.

"tail slides" at any speed you like. What ever that means when there is no "up". I don't think that funnels would be possible.

Turning off the mass in a simulator will not get it right, as the rotating and translating inertias would then be zero; the heli would not be representative of any physical reality at all. Turn off gravity and see what you get. I think you can do that in the sim, right (need to check on my Reflex tonight)...

Very entertaining discussion.

Never, ever, ever, ever give up.

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02-11-2008 08:10 PM  10 years agoPost 80
spork

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Mountain View, CA

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I don't think that funnels would be possible.
You could still do them, but they wouldn't look quite like funnels. The main-shaft would describe a plane. In other words, instead of the heli being at a high bank angle, it would be at a 90 degree bank angle. But of course the axis of the funnel could be horizontal, vertical, or any direction at all (since those words have no meaning in zero-G).

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