Nike-Nike Smoke

[Bruiser]

So while waiting for parts to come in I am contemplating another build. It's the Nike-Nike Smoke and I am thinking of building it as a 1/10th scale single stage. That makes it a BT-60 tube, overall length is 40.88 and it will fly on a Estes 29mm F engine.



I am trying to decide about using a 8" long engine tube versus a 17" long engine tube.

I was going to load my open rocket files but it doesn't seem to like them... I did do both and both mocked up fine. The 8" tube has a caliber of 1.6 and the 17" tube has a caliber of 1.5

So pluses of the 8" tube. I have all the parts on hand. The lower fins can be thru the wall. Minuses are that the upper fins won't be thru the wall and the larger area between the engine and the nose cone for ejections.

Pluses of the 17" tube. Both sets of fins can be thru the wall construction. The area inside the tube will be reduced. Minuses are that I would have to order the tube.

I'd love to read your thoughts

 

[neil_w]

Obligatory question: why not a two stager?

 

[Bruiser]

Well, I had a big, long answer started then I erased it and wrote this:

-Booster is too long for reliable gap staging (from what I've read)
-It seems too small for electronic air start (from what I've read)
-If there is some micro module out there, it would probably be more than I want to spend
-I want to keep it simple. I've built three rockets since being born again and haven't flown one yet

Hmmn, my rocketry seems to be following the same path as my RC Aircraft hobby. I loved building more than flying.

-Bob

 

[cwbullet]

It is a good time for your first electronic two stage.

 

[neil_w]

-Booster is too long for reliable gap staging (from what I've read)

Hmm, I'm not too sure about that. How long is the booster? Longer than... this? (If you're interested in pursuing gap-staging, definitely ping @BABAR for pointers).

But by all means, build what you want, not trying to push.

 

[Bruiser]

Well it is certainly not that far, lol!

Let's just say I made it a two stage rocket, the booster would be 13. 625 tall. Assuming I powered it with a D engine and the engine was flush with the end of the body tube, there would be a gap of 10.875 to the sustainer engine, also assuming it is flush with the end of it's body tube. Seems a bit far but none of the articles I read specified a distance. There's also the matter of needing to cut hole in the side of the body tube to let the cold air escape so the hot gases can make it to the engine.

Just had a thought about the holes. So one of the articles suggested running a motor mount tube from the first stage to the second stage to help keep the hot gases "focused" for lack of a better term. It also said the holes on the engine tube and the body tube do not need to be in line with each other. So what if I cut the holes in the motor tube but instead of cutting holes in the body tube, I cut holes in the motor mount centering rings like on a baffle for the air to escape?

The other thing I was wondering about it how to you keep the booster from being destroyed upon touch down? I can't figure out how to put a chute or streamer in there. I mean you couldn't have a chute or streamer between the two engines or the second stage wouldn't ignite...

-Bob

 

[neil_w]

Let's just say I made it a two stage rocket, the booster would be 13. 625 tall. Assuming I powered it with a D engine and the engine was flush with the end of the body tube, there would be a gap of 10.875 to the sustainer engine, also assuming it is flush with the end of it's body tube. Seems a bit far but none of the articles I read specified a distance. There's also the matter of needing to cut hole in the side of the body tube to let the cold air escape so the hot gases can make it to the engine.

Just had a thought about the holes. So one of the articles suggested running a motor mount tube from the first stage to the second stage to help keep the hot gases "focused" for lack of a better term. It also said the holes on the engine tube and the body tube do not need to be in line with each other. So what if I cut the holes in the motor tube but instead of cutting holes in the body tube, I cut holes in the motor mount centering rings like on a baffle for the air to escape?

That is absolutely doable I think. And yes, running the motor mount tube all the way through the booster is a good idea.

The other thing I was wondering about it how to you keep the booster from being destroyed upon touch down? I can't figure out how to put a chute or streamer in there. I mean you couldn't have a chute or streamer between the two engines or the second stage wouldn't ignite...

Ah, now you've hit the crux. A long gap-staged booster will likely be stable (test this out with OR or Rocksim!), and come down ballistic if you don't do anything to prevent it. There are various crazy ways of hiding streamers for the booster; I don't know if any of those methods would work for you or not. Definitely go search around for gap staging on TRF and see what others have done, and as I said try pinging @BABAR directly; in addition to having done some crazy gap stages, he always has some creative solutions to try for almost any situation.

It ultimately may not work out for your build, but can't hurt to think about it a bit before committing to single stage version.

 

[Charles_McG]

-Booster is too long for reliable gap staging (from what I've read)
-It seems too small for electronic air start (from what I've read)
-If there is some micro module out there, it would probably be more than I want to spend
-I want to keep it simple. I've built three rockets since being born again and haven't flown one yet.

I've put an Eggtimer Quantum and an Eggfinder and 2x2S 300mAh Lipos into a 55-60 transition, extended by a BT60 coupler. It's tight fit, but it can be done. Read about and you'll find people putting altimeters into 29mm nosecones. BT55 is a hair bigger than 29mm motor mount tubing.

The 'probably more than you want to spend' is a fair guess

 

[Bruiser]

I found an Apogee newsletter where they gap staged an Estes Nike-Apache. They had the motor mount tube go all the way to the sustainer. The engine of the sustainer actually slipped into the booster motor mount tube. They put the vent holes in the booster motor tube just below the sustainer engine, then put holes in the centering rings so the air could vent out the back of the booster (like I thought of yesterday). They taped a streamer to the outside of the motor mount tube. Now here's the part that gets me. When the sustainer engine ignites it pushes against the booster engine causing the booster motor mount tube (complete with centering rings) to shoot out of the booster body tube and the steamer unfurls for the recovery. In the process the body tube also gets pushed off the sustainer. I imagine the fit of the sustainer engine into the Booster motor tube would need to be a little less tight than the fit of the sustainer and booster body tube joint so that it will push the motor mount assembly out rather than just blow the booster stage off intact...

-Bob

 

[Dipstick]

Can you post that...I'm intrigued

 

[Woody's Workshop]

Bruiser...
I like it!
Build what you feel comfortable with.
Enjoying building more than flying isn't a problem...
Like me, it's a hobby. Just enjoy it.
I will make one suggestion...
Buy a pack of engines, and fly em.
And as always...Post Pics!

 

[Bruiser]

Duplicate...

 

[Bruiser]

Here's the link to the article:
https://www.apogeerockets.com/education/downloads/Newsletter416.pdf

It is the most "in-depth" article I have found that is close to the Nike-Nike layout. I had to read thru it several times to understand and it's still a lot for me to wrap my head around. Seems like everything has be just right or:

your booster is going to come in ballistic (if the motor mount assembly stays in the body tube)
the entire rocket is going to come in ballistic (if the second stage doesn't ignite)

It seems to me that the "fitting of the slip joints" is the key. You want the booster motor mount to slide in and out easily but not so much that it tries to fall out when you are handling it. The sustainer engine needs to fit in the booster motor mount tube without slop (because it helps to keep the stages aligned) but not snuggly because you want it to just slip apart upon ignition. The coupler that joins the booster to the sustainer needs to be without slop either to keep the two stages aligned, but probably snugger (is that a word?) than the engine in the motor mount.

I mocked it up in Open Rocket last night and everything looked good with the balance. With two "D" engines it said slightly over 1,000 feet which is probably to high for the balloon park 5 minutes from my house. There are fenced properties on three sides of the park...

I ordered a Estes 7247 Nike Smoke (my next build) from eRockets Tuesday night and I called Randy to see if he could add a 24mm motor mount tube to that order but the Smoke had already shipped. They have a heavy wall, foil lined tube that would be perfect for this project but shipping is more than the tube I am going to have to wait until I do a larger order

-Bob

 

[neil_w]

It seems to me that the "fitting of the slip joints" is the key. You want the booster motor mount to slide in and out easily but not so much that it tries to fall out when you are handling it.

This is a general characteristic of rear-ejection I think. I haven't done one yet. The weird thing here is that the motor mount should slide out upon ejection but you *also* want the booster BT to slide off the sustainer. Thinking of both of those happening at once makes my head hurt a little. It's possible that even if it's fairly loose, the friction of the motor mount sliding out of the tube will pull it with it. Eventually of course the shock cord will yank it out, but you'd like it to come off more quickly I think.

The sustainer engine needs to fit in the booster motor mount tube without slop (because it helps to keep the stages aligned) but not snuggly because you want it to just slip apart upon ignition.

That is typically not an issue, since motors are designed to fit into the motor mount tube (1st-gen Q-Jets notwithstanding ). If they're loose you can always wrap a bit of tape around the end of the sustainer motor.

The coupler that joins the booster to the sustainer needs to be without slop either to keep the two stages aligned, but probably snugger (is that a word?) than the engine in the motor mount.

Also generally not a problem. For my Odd'l cyclone, I CAed the coupler and then sanded it nice and smooth, slides really nicely. Given temperature and humidity variations you do want to check the fit before each flight.

They have a heavy wall, foil lined tube that would be perfect for this project but shipping is more than the tube I am going to have to wait until I do a larger order

Been there.

An alternative is to use regular heavy-walled BT50 (for the booster motor mount tube I would *definitely* use heavy-wall) and then coat the inside of the tube with CA.

 

[Bruiser]

Neil, that's something I hadn't considered. When the sustainer ignites and blows out the booster's motor mount, the mount itself will tug the rest of the booster off as the streamer deploys.

I hope my Smoke arrives soon so I can put off deciding... What I've been doing so far is progressing too quickly.





Right now I am busy with building back up the portion of the nose cone that slips in the manila body tube I had to make. I got a little happy sanding. It doesn't take long to go to far when the drill press is spinning and you have a tool with 120 grit paper on it

Maybe I should start building the modified fins for my Smoke. I think I have a heavy wall 24mm mount from the Protostar kit I bought on clearance for $7.49 at Hobby Lobby. I can mock it up with a BT60 tube to get the correct thru the wall measurements.

-Bob

 

[neil_w]

I think I have a heavy wall 24mm mount from the Protostar kit I bought on clearance for $7.49 at Hobby Lobby..

WOW that was a deal...

 

[Bruiser]

It was and I would have bought more but it was the only rocket they had on clearance. Since there are no hobby shops around, I have been buying kits from them to use for parts. The Nike-Nike is going to use mostly parts from a Star Orbiter kit.

-Bob

 

[Bruiser]

Well my Nike Smoke has arrived so I'll be thinking on this while I turn my Smoke into something a little different

Thanks for all the input. With you all's help and advise I am actually considering it!

=Bob