"Spinning Saucer of the Apocalypse" - 36" Saucer with Helicopter Recovery

[delta22]

In the summer of 2010 I built the Turbine Rocket Saucer (= TRS), a 20" spinning saucer that most often flies on 5 or 6 Estes D motors. An original design that lifts off spinning fast on a column of smoke and hovers for a few seconds before gradually descending. To date it has flown 27 times firing 138 motors. TRS was featured in the Nov/Dec issue of Sport Rocketry and in this TRF thread: https://www.rocketryforum.com/showthread.php?t=13727

This project, the "Spinning Saucer of the Apocalypse" (= SSoA) is a 1.8x upscale of the Turbine Rocket Saucer.

Planning - design improvements:

TRS has a flat bottom on its saucer ring, which hurts its stability as it descends, as the saucer to want to tip to spill air. To try to improve stability the SSoA's ring will have a triangular cross section that is equally angled top and bottom.

TRS has a sharp outer edge which takes damage every 2nd or 3rd flight and has been repeatedly repaired. SSoA will have rounded edges where it contacts the ground, both for the durability of the saucer and for improved safety if it ever comes in contact with a spectator as it lands.

Planning - size:

I wanted to be able to fly the SSoA on 4x G motors, which is about four times the total impulse of TRS. Shooting for similar flight profile, targeted area that was less than 4x and weight that was more than 4x of TRS.

Upscale....Weight....Area.....Diameter
1.6x ........4x..........2.56x....32"
1.8x.........5.8x........3.2x.....36"
2x............8x..........4x........40"

So went with a 1.8x upscale with a 36" diameter.

Below are some arty pictures I took at different exposures of the Turbine Rocket Saucer sitting inside the ring of the Spinning Saucer of the Apocalypse.

 

[delta22]

Started the build with the outer saucer ring.

Picked up some 2" thick sheets of foam from Lowes and marked out the circular cuts.

Started with an Exacto razor saw and then switched to a jigsaw as it was easier to slide through the foam. Used the lines to align the top of the cut and a metal bar taped to the edge of the table to align the bottom of the cut. The foam piece was positioned with a nail through its center into the table and rotated as it was cut.

The amount of foam debris created with these cuts was amazing.

 

[delta22]

Then sanded all foam surfaces with 220 sandpaper. Used sanding block for outer surfaces to even them off, using metal table edge again to align outer sanding.

Inner curve sanded with scrap foam as block from the inside cut. Then rounded all edges.

After this was done twice, joined two identical foam rings with epoxy to form final ring core.

Ring has 36" OD, 28" ID and is 4" tall. Ring foam core weighed 9oz.

 

[delta22]

Used a light (about 10oz) five inch fiberglass sleeve from Soller to fiberglass the ring.

Had to cut the sleeve to wrap it around the ring. The fiberglass wanted to curl badly and was hard to position.

I taped the glass in place and wetted it with epoxy by working it through from the outside and removing the tape after surrounding glass was completely wetted and in position.

Put down paper and release plastic on the flattest area of my basement floor. Then put the ring there to dry with the glass seam positioned on the bottom against the flat release material.

Fiberglassing the ring took about 3 hours, but the end result came out well.

Ring now weighs 38oz and feels strong and stiff.

Last picture shows older saucer inside new ring.

 

[CarVac]

What sort of motors and igniters do you plan to use? I did a 2xG76 cluster cone rocket, and one lit about a quarter second after the other one with Firstfire Juniors (not ideal, I know), though it flew just fine.

 

[eggplant]

Looks great so far Boris! I can't wait to see it. Will it be ready this spring? Also, Boris is the cluster king. Go to his website to see what he uses: https://www.bpasa.com/Cluster-box.htm

 

[Threemorewishes]

You could do a dual stage saucer!

 

[delta22]

What sort of motors and igniters do you plan to use? I did a 2xG76 cluster cone rocket, and one lit about a quarter second after the other one with Firstfire Juniors (not ideal, I know), though it flew just fine.

I plan to start with 4x F40 motors and then go to G64s. By using RMS reloads, can put a little Rocketflite ML Pyrogen at the top of the motor, helping with very quick pressurization.

I use either the Rocketfllite ML, CF or MF igniters/ematches, plus the cluster box noted below.

Looks great so far Boris! I can't wait to see it. Will it be ready this spring? Also, Boris is the cluster king. Go to his website to see what he uses: https://www.bpasa.com/Cluster-box.htm

Thanks. I plan to have it ready for the CMASS 4/28/12 Amesbury launch. Also to fly it at LDRS.

The cluster box was featured in the Jan/Feb issue of Sport Rocketry.

You could do a dual stage saucer!

Interesting idea......

It would be hard to keep the upper stage from burning the lower stage. Have thought about parallel staging, using a timer to fire additional motors several seconds into the flight.

 

[delta22]

Been working on other projects so progress is slow right now.

My son's TARC team got some good qualification flights in with scores of 17 and 20, hope they make it to the nationals again this year.
Also painting rooms in my mother's house and building my L3 project: https://www.rocketryforum.com/showthread.php?t=32802

Been filling a few holes in the fiberglass covering the foam ring with epoxy.

Also cut and fiberglassed with 3x wraps of 1.3oz glass two center pieces:

> 1" diameter LOC tube 10" long which will be at center of rocket and serve as launch lug

> 7.6" diameter LOC tube 4" long which will serve as the central hub to which the turbine blades will attach

Also ordered and received some other parts:

> 2x centering rings 1/8" thick, made to order by LOC, to join the two parts glassed above

> Many 1/8" x 4" x 24" sheets of basswood, which will be built up to form the turbine blades

 

[Sully]

Looking very cool. Will this be ready for the CMASS launch later this month?

 

[delta22]

Looking very cool. Will this be ready for the CMASS launch later this month?

My first rocketry priority is to have this ready to fly at the CMASS Amesbury 4/28/12 launch.

It will probably be naked (unpainted) and based on how things go for the first flight(s) there may well be modifications to follow.

Because the rocket design and flight profile is so unusual, tweaking design and motor selection is likely.

It took a half dozen flights to dial in these parameters on this project's smaller predecessor, the Turbine Rocket Saucer.

 

[delta22]

Thanks to Bill Spadafora for making the custom launch rod for this project.

It is primarily 1/2" ID black iron pipe. This pipe is normally used for natural gas. It is very heavy and rigid, and has an OD of just under 0.9".

The longest (3ft) section will point straight up and is what the SSoA launches from. The pipe coupler closer to the bottom of the rod is what the saucer will sit on while waiting for launch. The shorter bottom section is welded to a 1/2" rod for easy mounting into any HP pad.

24" ruler in picture for scale.

 

[delta22]

The "launch lug" will be located in the center of the saucer so that the saucer can spin quickly and stabilize before separating from the rod.

The lug is 10" long and made up of LOC 1" tubing wrapped with three layers of 1.3 oz fiberglass. Inside of that is another section of the same cardboard tube with a slice removed to reduce its diameter. The protruding short sections of inside tubing are about to be trimmed off.

This created a light, rigid tube that has an excellent fit with the rod.

 

[delta22]

The bottom centering ring has four 10-24 Tnuts installed to allow future attachment of custom motor mounts. These will not be used for normal flights but provide for flexibility.

Also installed a door in bottom CR to allow for installation of electronics. A timer to would support firing parallel staged motors to extend flight time. Could also add LED lighting if ever an HP night flight opportunity presented itself.

Last two pictures show center launch lug installed in the 7.6" OD center hub.

 

[delta22]

Been patching small holes in the fiberglass sleeve.

Then wiped ring with more resin to maximize hard, even shell.

 

[delta22]

Formed and CA'ed into place a paper cone for the top of the center unit.

Then covered with 2 1/2 circular pieces of 1.3oz fiberglass creating a build up of 4+ layers that covered all of the cone plus about 1" onto top and bottom tubes.

 

[delta22]

I was considering several possibilities for engine arrangement.

Originally thought I would use 4x 29mm F40 or G64 engines positioned similarly to the setup in the smaller Turbine Rocket Saucer, producing both spin and lift.

Have decided to use one arrangement of motors to induce spin and another set for lift. This allows for optimization of motor selection and placement for each task.

Initial flight plan is to use 8x very canted Estes C11 motors positioned just inside the bottom of the outer ring to induce spin. With about 2.5 lbs of thrust each x 8 motors pushing for 0.9 seconds, they should induce the roughly 3 lb outer ring assembly to spin at about 1000 RPM. This compares to the 1500 to 2000 RPM measured for the smaller TRS.

For lift will use 2x AT F40 reloads, moving up to G64 engines if all goes well. As these are lift motors, they are positioned straight down near the center of the rocket.

Picture shows the 2x 29mm lift engine tubes added to the center unit.

 

[delta22]

Started with 8 pieces of 1/8" x 4" x 24" basswood to build up the turbine blades.

Dave Lindberg had suggested twisting the blades to vary the angle of attack to even up thrust. This way the outer area of the blades which travels fastest will be at a slight angle and the slower inner area will have a more aggressive pitch.

To accomplish this:
> rounded the top edges of each piece of basswood
> cut them in half forming 16 pieces 1 ft long
> using a generous amount of CA and a wedge under one end of each blade, glued pairs of these pieces forming twisted blades 4" x 1/4" x 12"

Used up 30g Locktite pro CA. Speed and strength of bond is amazing.

As this process is not something I had done before, the first three blades had unintended warps and I rejected them. The fourth was perfectly flat except for the desired twist, lifting the inside corner by 1/2".

Used this piece plus the wedge as a form to build the remaining fins, plus three replacements, to finally get 8 well formed turbine fins.

 

[delta22]

Carefully marked out positions for center unit, outer ring and 8x turbine fins in preparation for assembly.

 

[delta22]

Cut and sanded (to make them more uniform) cardboard forms to accurately position turbine blades.

Cut and sanded the turbine blades carefully to length get a snug and even fit for assembly.

 

[delta22]

Working on the flattest area of my basement floor, very carefully positioned all fan blades. Went around the rocket half a dozen times tweaking and checking all part positions.

Then tacked everything together with Locktite CA. Half an hour later filleted tops of all fan blades with West Systems 206 epoxy thickened with colloidal silica.

Base goal for this rocket is a similar flight profile as its little brother, TRS, with a typical flight time of about 15 seconds. Ideal would be a longer flight time.

At Turbine Rocket Saucer's maximum of 1500 to 2000 RPM, with a 30 degree blade pitch and fan blades with maximum radius of 7 inches, maximum air speed through fan is about 40 to 50 feet per sec.

For the SSoA, targeted a reduced maximum fan air speed in the hopes of reducing drag, sustaining spin rate and longer total flight time.

Set a 15 degree pitch for the fan blades on their outer ends where they join the ring. The amount of twist achieved during fin assembly has the fan blade pitch near the center at about 20 degrees.

The SSoA has a target maximum of 1000 RPM and a maximum fan radius of 14":

1000 RPM / 60 sec = 16.7 revolutions per sec
x 2 pi radius (14") / 12 inches per foot = 122 feet per sec max fan velocity
15 degree angle has about a 1 to 4 pitch so
122 ft / 4 = about 30 ft per sec maximum air speed at fan

Part weights: ring 41 oz, fan blades 24 oz, center hub 12 oz.

Total weight of pictured assembly 4.8 lbs. Launch weight will be about 6 lbs.

Size: 36" diameter and 10" tall.

 

[delta22]

Added braces at the bottom of the rocket between the hub and fan blades. Shaped from 2" squares of 1/8" basswood. Tacked with CA and then filleted twice with epoxy.

This greatly stiffened the flat rocket to better stand up to the thrust of the central lift motors.

 

[delta22]

Built "spin" motor tubes from 24mm LOC tubing. Wrapped 3x with 1.3oz FG, cut to 4" lengths and glued in pairs.

Then 2 strips of 6oz FG formed a sling around each motor tube pair, firmly anchoring it to the ring and adjacent fin.

 

[delta22]

To smooth airflow over spin motor assemblies, created fairings.

CA'ed 3" strips of paper to create form. Then covered with 2x layers of 6oz glass to both make form rigid and further anchor spin motor tubes as centrifugal force will be intense.

Structure of rocket is complete. Remaining prep is sanding and minor epoxy touch up.

Will fly Saturday at 4/28/12 CMASS Amesbury, MA launch.

First flight will be on 2x AT 29mm F40s for lift and 8x Estes C11s for spin.

Will have motors for a second flight with choice of F40/G64 and C11/D12 combinations depending on first flight performance.

 

[JStitz]

Boris! great project...I have done production woodwork/cabinetry/Props and making those 16 pieces can drive you nutz!
I'm op: on this build.
I hope the centrepidal (did I spell that right) forces will not be too much..dont spin her up too much!

Have you thought about selling LED kits?

 

[Quaranta]

Will fly Saturday at 4/28/12 CMASS Amesbury, MA launch...

How did it go?

 

[Coop]

Echoing the above--let us know how it went off!


Later!

--Coop

 

[bobkrech]

Boris had 2 great flights at the CNASS launch held in Berwick, ME courtesy of MMMSC.

He has lots of pictures and videos.

Bob

 

[delta22]

Yesterday, 4/28/12, CMASS flew with MMMSC at their beautiful field in Berwick, ME as the fire hazard conditions at Amesbury, MA were too high.

First flight for the Spinning Saucer of the Apocalypse went up on 2x AT F40 and 8x Estes C11 motors.

Used my cluster box and Rocketflite CF igniters to fire all motors.

 

[delta22]

This was an intentionally conservative first flight with regard to impulse for this original design rocket.

The quick burn of the 8x C11 spin motors got the saucer spinning quickly even before the F40s struggled to lift the 6 lb rocket off the rod. For the first second there was so much smoke at the pad I was not sure the rocket was going to leave the rod.

It flew for 5 seconds to about 50ft altitude staying flat for the flight.

Looking at the position of the blue tape stripe in video frames was able to judge RPM fairly accurately. Will post videos later today.

Peak was 900 RPM declining to 600 when it landed and continued to spin for a couple seconds laying flat on the grass, creating a green ring on the bottom of the saucer.