Helicopter Recovery

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
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The Sky Dart
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Helicopter Recovery

Post by The Sky Dart »

If someone is interested in the copter recovery, we've done a little test confirming possibility of a reliable deployment of a rotor. We used our pet project air rocket model, but there is nothing stopping one from using the same approach to recover a water rocket.
The key feature of the system is that the rotor is deployed automatically without help of any additional devices.

[youtube][/youtube]
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The Sky Dart
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Stevo14
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Re: Helicopter Recovery

Post by Stevo14 »

Wow. Very nice!

Could you elaborate on how the system deploys "without the help of any additional devices"? Is it just NOAA or is it more complicated (springs levers etc.)?
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The Sky Dart
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Re: Helicopter Recovery

Post by The Sky Dart »

Stevo14 wrote:Wow. Very nice!

Could you elaborate on how the system deploys "without the help of any additional devices"? Is it just NOAA or is it more complicated (springs levers etc.)?
The nose cone shoulder diameter is a bit less than the inside diameter of the body tube it sits in. It allows it to slide freely out of the body tube when the blades open up. There are no springs, levers etc. The folded back blades keep the nose cone in place on the way up and doesn't allow it to pop out at the moment of launch.

Now, the key is how to force blades to open. Without any additional effort a rocket of such shape-form will have it's centre of gravity (CG) in front not only the centre of pressure (CP), but in front of its centre of lateral area (CLA) as well. This effectively makes it very stable. It means that on reaching the apogee the rocket will promptly turn nose down.

If CG is moved somehow in between CLA and CG, the rocket will glide downwards on it side because it'll be the stable position. Transition from one stable state to another on the apogee will be through some backsliding during which the blades will be forced up by incident flow of air.
Cheers,
The Sky Dart
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The Sky Dart
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Re: Helicopter Recovery

Post by The Sky Dart »

By the way:

- The best or rather lowest descent rate for a copter recovery system is about 3.6*SQRT(W/S), where W-rocket mass in kg, and S- rotor disc area in m.sq. This is the lowest possible descent rate for a well design rotor. It corresponds to about 85% of the Cd of a spherical parachute of the same area.

Helicopter class sport models usually have blades as long as their body. The aim is to stay in the air as long as possible. However, if higher rate is acceptable much shorter blades can be used.
Cheers,
The Sky Dart
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U.S. Water Rockets1
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Re: Helicopter Recovery

Post by U.S. Water Rockets1 »

The Sky Dart wrote:By the way:

- The best or rather lowest descent rate for a copter recovery system is about 3.6*SQRT(W/S), where W-rocket mass in kg, and S- rotor disc area in m.sq. This is the lowest possible descent rate for a well design rotor. It corresponds to about 85% of the Cd of a spherical parachute of the same area.

Helicopter class sport models usually have blades as long as their body. The aim is to stay in the air as long as possible. However, if higher rate is acceptable much shorter blades can be used.
Thanks for sharing the design. This is one of the best engineered helicopter recovery designs to come along in a very long time. You're obviously put a lot of thought into the design and really did your homework. Good job!
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