"Plunger" Ejection mod post 18 "TextBook" Rocket-- Input GREATLY welcomed.

Well, I've accepted the commission from Earth Day project with Space Center Houston, so I will try to do a build thread and appreciate any advice I can get.

Desire is for rocket(s) built out of textbooks.

My original plan was one small one launched on a D and one larger one on 3 Ds. May need to go with a G for the larger. Want to stay out of high power land.

Got the books covers---- great building material but heavy, especially with the polygonal plan I have in mind.

Here is what I have so far.

The little blocks are cardboard "fillets" that keep the alignment straight.


The "fin can" for the larger rocket is already at 321 grams. This is 11 inches long. Was planning on 3 sections plus nose cone, estimate the other two sections also 11 inches long will probably come in around 250 grams each, nose cone probably 150 grams. Still need to add engine mount, parachute won't weigh that much. Plus engines. 3 Ds at 41 grams each so add another 125 grams, already at nearly 1100 grams. So either need to go up to 4 Ds (cluster reliability starts to become an issue) or go to a bigger engine, thinking a G. Hoping I can FIND a G for a test flight at hobby lobby (seems like they have stopped carrying the composites, but will check again tomorrow)

Thanks all

Tom

Hi Tom,
They commissioned me to build one too!
Problem is, they sent me the wrong package!
I was sent a scarf along with a letter to Grandma thanking here for taking care of the grand kids.

No, I'm not making this up . . .

hcmbanjo said:

Hi Tom,
They commissioned me to build one too!
Problem is, they sent me the wrong package!
I was sent a scarf along with a letter to Grandma thanking here for taking care of the grand kids.

No, I'm not making this up . . .

Click to expand...

Great, now we are going to go from the Little Green Man to the "Granny's Bloomers" Rocket

Although.... if you were trying to attract the fairer sex to the rocketry hobby, a tube fined rocket fashioned as a Lady with a Hoop Skirt might fit the bill.

Chris,

My apologies the textbooks didn't arrive yet.

The production team has no idea where that scarf came from or how our label got on that package. Does someone's grandma have a box full of textbooks waiting to be turning into a model rocket? No idea.

We'll get you more textbooks. And give you a chance to set them free. Textbooks probably never really wanted to be textbooks.

Great to see Tom exploring!

Thanks,
Craig

hcmbanjo said:

Hi Tom,
They commissioned me to build one too!
Problem is, they sent me the wrong package!
I was sent a scarf along with a letter to Grandma thanking here for taking care of the grand kids.

No, I'm not making this up . . .

Click to expand...

Got final shape worked out. I am at 670 grams (these are some heavy textbooks! and that is just the covers!) and that is without engine mount, engines, and recovery. Should be easily loft-able on cluster of 3 D12s. A little shorter than I planned on, but adding another section brings me up another 220 grams and starts getting a little too close for comfort. Looked up recommended max launch weight for a G engine at 900 grams, so I think I am better off with the 3 Ds. (Correct me if I am wrong.)

I don't like the nose cone, came out a little too small, and need a more striking color, so will re-do that part.

How's it going, Tom?

Any updates and /or new pictures?

Can't wait to see final product!

Will finish tomorrow Sunday with parachute and final "pin striping"
Problem.... I have no D12-3s. My order from HobbyLinc is delayed and H0bbylobby has only D12-5s and D12-0s.
I am currently at 930 grams without engines and chute. Engines will add 126, chute and shrouds and shock won't add much, so I will be in the 1188 grams for max lift off for 3 d12-3s at 396 grams each. I have launch lugs capable of handling up to a 1/4" rod, recommend longest 1/4 " rod you have. I may drive up to Memphis tomorrow to see if anyone up there has D12-3s. If not I will NOT be able to test the rocket before I send it.

Second smaller rocket I should be able to test on single D12-5.

My main computer is on the fritz so can't send pics at the moment.

Plan to get all in Mail Monday. Do you want the larger rocket if I can't test it before sending?

Thanks for the update, Tom.

That all sounds good.

Yes, we'd like both rockets, tested or not.

And it's great to get any notes from you about engines and recommendations of rods.

We'll have our rocket expert inspect them and make sure they're safe to launch.

Thank you!

Great. Will get them in ups tomorrow 2 day shipping. Recommend D12-3 s for both, (3 for biggie, 1 for smaller).
Both 1/4" rod, 6 feet if you have it, at least 4 feet.
I will try to remember to send you 3 quest igniters for the cluster. Need an ignition system that will handle the low voltage continuity check. Your launch experts will know what I mean.


The biggie has a plunger ejection system, I will put pics in build thread, but I still recommend some dog barf wadding for insurance.
Do these go to the address you emailed me?

First flight of all scratch rockets should be heads up flight, be great if your guys can run a test before the real event.
Thanks for letting me participate.
Tom

Since the big one is heavy, lumbering, kind of a dinosaur, and has three fins, figured I'd call it the Triceratops (plus starts with T for Textbook.)

Pics show placement of the cardboard shoulder in the nose cone. The nose cone is a three sided pyramid. Last pics show placement of what I call cardboard fillets that act as guides to keep the edges in place.

Triceratops... nice.

Looking good, Tom.

Final Mass on Triceratops: 2 lbs 10 oz or 1190 grams, puts it right at max lift off weight for 3 D12-3s. This is with engines, parachute, and pin striping. Only thing not included is wadding. Since it has a piston ejection system, none needed (although would add some for insurance.)

Now for work on the Katana. Gotta get all in the mail tomorrow.

With Lucy the Wonder Dog

Great textbook rocket!

The tall nosecone came out really nice.

And the fin design is an interesting use of the one surface.

Any pre-launch predications?

Launch predictions

First, not going to set any altitude records

With 6 foot rod predict low and slow but stable lift off for triceratops. Lots of fin area so should be stable. Little concerned about altitude before deployment as we are at max lift off weight and a draggy rocket. First flight should be heads up without a spectators, my main regret is not having a chance to test fly. For the record, this is the first time HobbyLinc has let me down on prompt shipping.

Katana should be low and slow, but certainly within capability of D12-3 with a 6 foot rod. Still it is a new design and would test fly before public display.

You should have both rockets tomorrow/Tuesday. I will be interested in and will certainly respect and appreciate the opinions of the NASA rocket experts regarding airworthiness of these birds. They were a pleasure to build. Even more fun to mail them to an official NASA address. How many rocketeers can say they are NASA subcontractors and they build rockets for NASA by request!

Hope your event is a blas.... I mean a hit.

Tom

BABAR said:

Even more fun to mail them to an official NASA address. How many rocketeers can say they are NASA subcontractors and they build rockets for NASA by request!

Tom

Click to expand...

Hi Tome,
I just got mine in the mail today! It should be there by the deadline.
You're right, it was cool actually sending something to NASA.

My rocket was more traditional with a round body tube. Your triangular body should be plenty strong!
I had a tough time with the nose cone, I had to make a one also.
The first one warped as the glue dried and it ended up looking like a zucchini!
This build was a real learning experience for me.

I'll probably cover the build on the blog as soon as I get it all written up.
I enjoyed your build thread.

P.S. (I sent the scarf back to Grandma)

Triceratops Prep

Triceratops has the following difference from a typical rocket.
Being constructed from book covers, which are 6 times heavier square inch for square inch surface area than balsa, it is a bit of a brick. 2 lbs 10 oz loaded. I will confess I did "cheat" on the outboard (red colored) fins, these are balsa. While I believe the design would be stable as built without the OUTBOARDs if it wasn't so darn heavy, I added the extra "finnage" for insurance.

It has a triangular rather than cylindrical body tube. Even with three motor mount tubes the distribution of the ejection charges will not be as evenly spread across the interior. In addition, the angular internal contour is more likely to force the chute off the side or other asymmetric force rather than forward. And finally, while there are other short rockets, it is kind of "stubby" (I had planned to go longer but ran into weight considerations.)

For this reason there is a plunger or "tray"

This is attached by a fishing leader (actually 4 of them, as I couldn't find one long enough) to the motor mount. The wire fishing leader is attached to with Kevlar to the three protruding engine tubes at the tail end. The part within the forward compartment which will be exposed to engine blast is all wire leader to prevent burn through.
The wire leader extends to the tray, through a small hole, and continues to attach to the Kevlar attachment to chute and nose cone.

The tray is slightly smaller in diameter but shaped the same as the internal contour. It has a pringles can bottom where the three engine motor mounts will flame it. I find the bases of the pringles cans are fairly easy to cut to shape with good scissors, just be careful as ctu edges are extremely sharp.

The tray has mylar along the edge to make it slippery. Like the Katana, the inside of the body tube is intentionally left smooth (no shock cord attachment or anything else) to "catch" the tray or chute". The "sides" of the tray I think are wide enough to maintain the orientation of the plunger so it doesn't "tip over" or otherwise catch. If you turn the rocket over, it easily falls out.

For prep, I still would put some cellulose (dog barf) wadding between the tray and the engine tubes, and a small amount on top of the tray. Just for insurance.

The red wraps on the tail end of the protruding engine tubes are not just for show. I didn't want to have motor hooks as it makes it hard to sit this rocket on it's tail for display or storage purposes, and I didn't want to forward recess the engines any more. Motor retention will be combination of friction fit, but there is also enough protruding accessible engine mount tube to put a strip of tape around the protruding engine butts and the engine tube. Always thinking positive (that this puppy may actually fly TWICE) the mylar will allow the tape to be removed AFTER the flight to get the engine out. In the past I have found pulling the tape off frequently pulls paint or even worse outer layer of paper off the mount/rocket.

The launch lugs are made of book cover cardboard and are large enough to accommodate a 1/4" steel rod, 6 foot recommended.

Fingers crossed for straight trails.

Tom