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Turbine Rocket Saucer

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delta22

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Ever since building a fleet of fun Applewhite saucers several years ago, I wanted to build one that spins.

If it works, it will look cool, benefit from some gyroscopic stabilization, and with the right use of fins, may convert some of that spin into lift.

The design idea is an outer rim shaped and built like several Applewhite saucer designs. 20" total OD, 3" wide with 30 degree angle between top and bottom (pictured below). Inside that (not yet built) will go eight 3" x 3/16" basswood fins forming inner turbine blades. Center will be 4" tube that will accept interchangeable motor mounts.

Construction of the pictured ring uses 1/4" foam board for the bottom and paper to form inner and top rings.

< Shameless plug warning :clap: >
Applewhite's saucers fly with lots of fire and smoke at low altitude and don't need parachutes. They are very cool, great for any size field, and never have a bad recovery. http://www.artapplewhite.com/

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delta22

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Then fiberglassed the ring lightly for strength using 1.3 oz glass.

3 layers in the inside diameter as that is what the "turbine" blades will mount to, 2 layers on the top and 1 layer on the bottom of the foam board to harden the surface.

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cjl

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This should be really interesting. I'll be curious to see how it flies.
 

rstaff3

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Sounds pretty cool, can't wait for the flight report! Needs lights or at least a roll pattern.
 

delta22

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Internal fins attach to a 4" diameter tube 3" long, which is wrapped with a couple layers of the 1.3 oz FG.

Motor mount is interchangeable. Unit has 8x 24mm tubes canted surrounding 1/2" rod lug. This will allow many motor combinations and for the saucer to start rotating before separating from the rod.

Made a diagram to assist in accurate placement of all components.

Airfoiled 8 fins and tacked them in place with CA before applying light epoxy fillets top and bottom.

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delta22

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First flight was on 4x D12-0 motors. Liftoff was great, firing all motors, spinning and lifting quickly off the rod. Estimate about 100-150ft altitude.

Gyroscopic effect was noticeable with rocket staying very flat during liftoff. Some moderate lift continued after motor burnout, presumably due to turbine action of fins.

The only shortcoming in flight was on the way down. Rocket continued to spin at a gradually slowing rate until it hit the ground, so the gyroscopic effect prevented it from flipping over the way most saucers do on recovery. Instead it tipped to about a 45 degree angle and came down on one edge.

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delta22

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Second flight was on 8x D12-0 engines.

Again liftoff was great, firing all motors, with quick spin and lift off the rod. Very similar flight behavior to previous flight, this time reaching 150-200ft altitude.

Last picture shows the continued lift after motor burnout.

Both times liftoff was straight up and recovery angled to about 45 degrees, landing downwind.

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delta22

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Both landings seem to have impacted the same area of the rocket, with the second flight landing on a hard surface and doing more damage.

It will not be hard to repair the split edge, and at the same time lay a little more fiberglass on it to make the outer edge stronger.

What will be more challenging is to change with way it comes down.

I think more spin relative to its altitude may keep it flat until it touches down, softening the landings.

Two things that would help this occur would be:

1) More FG on the outer edge, adding both strength and rotational momentum (keeping it spinning longer).

2) Canting the motors more. There was lifting force to spare with 4x D12's in the moderately canted setup tested today.

I like the idea of a roll pattern, didn't have time to paint it today, but some type of roll pattern and/or lights would be very cool.

Outer ring (wedge shaped cross section without fins) weighted 6.1 oz. Completed saucer with motor insert was 13.3 oz. Depending on motors used, flight weight today was 1.1-1.6 lbs.

>> Any suggestions would be appreciated.
.

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rstaff3

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Frisbee recovery! The flights looked cool. Could you use a motor with eject that would eject just enough of a streamer to stop the spin? Just thinking out loud.
 

BobCox

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Very cool, Boris.

Last month I built an Art Applewhite cluster saucer, which comes with interchangeable motor mounts. I asked Art about using a canted cluster mount and he warned me against it. As you found out, a spinning saucer does not flip over during recovery and tends to land on its edge.

(Bit of irony -- as I posted this message, the Art Applewhite ad appeared on the top of the page.)

To get more altitude, I think you should either cant the motors more to get more spin so the turbine blades can provide the lift, or else cant the blades less so they have less drag during boost.

To get it to flip, maybe you could have a weighted nose cone with a shock cord about 6-10 feet long. When it pops off it would yank the saucer over and pull it down nose-first. By having a long shock cord, the weight would hit the ground first and give the rest of the saucer time to slow down before impact.


Another option: put angled deflectors on the top of the motors so that when the ejection charges fire, they slow down the rotation.
 

gdiscenza

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I have a thought concerning some fun electronics:

Install a weighted centrifugal switch to activate rim-mounted lights once the saucer comes up to spinning speed.

G.D.
 

Handeman

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Can you use D12-3s and eject the motor mount assembly, attached with some kevlar and a swivel of course? This should put the CG well below the spinning saucer and may provide more veritical helicopter recovery.
 

rokit

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. . . frisbee than a saucer (that whole angular momentum/gyroscope thing). As long as it's rotating, I don't think you will be able to get it to fully flip over. Unless you can either kill the spin, or keep the spin speed up until it lands, you will likely get that tilt at landing -- at least, that's what usually happened when I used to play Frisbee Golf :D

Mike
 

andytherocketeer

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Interesting.

With L << D they should be naturally stable with no spinning. My (non-spinny) saucers more often than not come in flat in a draggy mode rather than flipping over. Looks like the spinning ones are going in to frisbee mode before being horizontal to the ground and the spin stabilisation overrules the drag?

Certainly looks like something fun to play with though :)
 

delta22

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...Unless you can either kill the spin, or keep the spin speed up until it lands, you will likely get that tilt at landing...
Mike
That seems to be the heart of the matter right there.

1) Good: Spin fast until touchdown, lots of spin and modest altitude.

2) Not so Much: Slowing spin during recovery, more altitude, angle dive recovery = first 2 flights.

3) Good: Lift and spin at liftoff, for recovery kill spin and implement tumble or chute recovery.

Thanks all for many interesting suggestions, a lot of ideas to consider.
 

delta22

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Painted epoxy (West 206) inside the tear, taped it together and applied weight to press the bottom flat.

Then added slightly more fiber glass to top and bottom of outer ring, bringing build up of all 3 sides up to 3 layers of 1.3oz. Saucer weight went from 13.3oz to 14.9oz after this step.

Finally added 4 more motor tubes mounted to inner area of fins. These new motor mounts are canted at 60 degrees from vertical. Original 8 center motor tubes are canted at 20 degrees from vertical.

Next flight will combine motors in both positions. Could do 2x D12 at 20 deg and 2x D12 at 60 deg to get more spin and less lift. Or possibly 4x C11 at 20 deg to get a good kick off the rod and 2x E9 at 60 deg to really wind up the spin with the longer burn.

With more ring weight and strength, as well as additional very canted motor mounts, I will try to keep the saucer spinning fast and flat until it returns to ground. Altitudes will be moderate.

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delta22

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Flew the Turbine Rocket Saucer three more times at the CMASS launch in Acton, MA on 8/14/10.

Each of the 3 flights went up on 4 motors all loaded in the new motor tubes which are canted at 60 degrees from vertical.

The flights were great, with lots of spin and safe, quick, straight liftoffs. Recoveries were gentle this time due to increased spin and moderate altitude, I estimate about 100 ft.

Flight 1 pics below going up on 4x D12-0.

Video of flight 2 on 2x D12-0 and 2x E9-4 is here (6MB):
http://www.bpasa.com/Movies2010/TRS4.wmv

This is the flight profile I was hoping for! Spinning liftoff, hover and gentle recovery.

From the video it looks like about 4 seconds of lift, 3 seconds hover and 5 seconds for gradual recovery.


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delta22

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Also flew the saucer which most inspired this project, Applewhite's 12" Classic Saucer.

Going up on an AT F25 White Lightning.

A great kit seen here lifting off for its 28th flight.

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delta22

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Pictures of the TRS going up for the third time yesterday, again on 2x D12-0 and 2x E9-4.

Nice spin and liftoff with another gentle recovery.

In the third picture can see the saucer continue to lift due to the turbine action of the fins. At this point the saucer is hovering before gradually dropping.

A negative is that at burnout, the engines eject burning material over the fins and inside the ring causing minor scorching.

A bigger and unexpected negative occurred with the E9 engines, all four burned through the outside of their casings. I believe this is due to the fast spinning of the rocket in combination with the longer burning engine and delay.

Pulled out the E9 motors partially and rotated them for the last picture.

Will have to stick with the D12-0 engines going forward.

Next steps will be:
> Fix the 2 scorched fins
> Add 4 more very canted motor tubes
> Extend and/or add baffles at the top of the motor tubes to reduce scorching
> Paint on thin epoxy for more fire hardening

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cjl

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Very, very cool. I love the way it softly spins down to the ground.
 

rstaff3

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Good show Boris! That's really cool. BTW, I've had plenty of burn-throughs on Estes motors in spinny things (usually monocopters). This is even worse on the thin walled D5s.

PS, may I reuse one of the photos on my blog?
 

delta22

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Good show Boris! That's really cool. BTW, I've had plenty of burn-throughs on Estes motors in spinny things (usually monocopters). This is even worse on the thin walled D5s.

PS, may I reuse one of the photos on my blog?
Please feel free to repost a picture.

Interesting, I would not have guessed that the centrifugal force of a spinning rocket would have been enough to meaningfully change the internal dynamics of a rocket engine.
 

bobkrech

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Watching the launches is even better than the videos. They were truely spectacular.

Bob
 

rstaff3

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Please feel free to repost a picture.

Interesting, I would not have guessed that the centrifugal force of a spinning rocket would have been enough to meaningfully change the internal dynamics of a rocket engine.
Thanks!
 
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