My first staged rocket. Build Thread

[soxfan121]

This is going to be my first staged rocket, it will be flying on 2 g78 motors. The sustainer stage's motor has a 10 second delay and the booster's delay time is 7 seconds. Both are green mojave propellant types.
-The Sustainer is a minimum diameter 29mm
-The Booster is a 38mm airframe
-All body/ airframe tube is Blue tube as are the couplers
- fins are .125in thick balsa layered with paper and a thin epoxy layer sanded smooth then as with the rest of the rocket painted and polished for a very smooth finish. they will also have a airfoil cross section
-nosecone is a plastic nose cone from apogee
-sustainer ignition will be with the minitimer from perfectflite ( https://perfectflite.com/MT4.html )
-Both motors are aerotech G78G- (10&7) which are 133Ns each for a total of 266Ns of thrust. (equivalent to a 68% H motor) they are single use but i load them myself which makes them around $25 cheaper and no HAZMAT fee so $25 extra off my order! :grin:
~still deciding on the igniter please for all of you with more experience with this type of timer what igniter would be best? it says no copper heads or first fire (jr)

Predicted flight stats
Velocity off rod:60.8 ft/s
Apogee:7,548 feet
Velocity @ deployment:63.3 ft/s
Max Velocity:823 mph (MACH 1.1) or 1207ft/s
Max acceleration: 1084ft/s^2
Time to apogee:22.1s
Flight time:126s
Ground hit velocity: 47mph or 69ft/s :eyepop: I'll be working on fixing this...

 

[soxfan121]

Forgot these two attachments, ork file and split picture
Also forgot to mention tracking:
I designed a coupler section with probably 5+ ultra bright LED's on one side and the same on the other, the LED's will be attached to a balsa bulkhead (5 on one so 2 bulkheads) and these will endcap the coupler at each end, inside the coupler there will be all of the wiring and batteries. I will be launching this rocket at dusk at a Bong Wisconsin launch this summer if all goes well. still have not decided the exact date and I'm unsure if it will be launched with tripoli or NAR (most likely Tripoli).





View attachment lightning.ork

 

[CarVac]

Set your velocities in ft/s, it is more commonly used.

That said, you should have ground hit velocities below 15mph=22ft/s.

 

[DizWolf]

My first thoughts are 47MPH is too fast coming back down. Should be aiming for 20 MPH or less.

I could very well be missing something, but the aerotech G78's are Mojave Green propellant, the White Lightning is a G79. The impulses also don't match up to what I'm finding here: https://www.thrustcurve.org/motorsearch.jsp?id=581 Am I looking at the wrong motors?

Very cool design.

 

[soxfan121]

Set your velocities in ft/s, it is more commonly used.

That said, you should have ground hit velocities below 15mph=22ft/s.

Can do thanks for the quick response!

 

[soxfan121]

My first thoughts are 47MPH is too fast coming back down. Should be aiming for 20 MPH or less.

I could very well be missing something, but the aerotech G78's are Mojave Green propellant, the White Lightning is a G79. The impulses also don't match up to what I'm finding here: https://www.thrustcurve.org/motorsearch.jsp?id=581 Am I looking at the wrong motors?

Very cool design.

thank's for pointing that out i forgot that i changed them from g79 originally and forgot to check the new propellant

 

[Salvage-1]

fins are .125in thick balsa layered with paper and a thin epoxy layer sanded smooth then as with the rest of the rocket painted and polished for a very smooth finish. they will also have a airfoil cross section

are you sure you want to do this for Mach speeds? 1/8 ply would be better.

 

[CarVac]

are you sure you want to do this for Mach speeds? 1/8 ply would be better.

I would suggest 1/16" G10/FR4, which is super durable and smooth surfaced.

 

[soxfan121]

I would suggest 1/16" G10/FR4, which is super durable and smooth surfaced.

where do you buy 1/16" sheets of g10/fr4? also any suggestions on using it? (besides wearing a respirator and eye protection)

 

[DizWolf]

https://rocketrywarehouse.com/index.php?cPath=26&osCsid=f1ca20dd7aa0d9ea06b2e05cf6a3f7ce

 

[soxfan121]

https://rocketrywarehouse.com/index.php?cPath=26&osCsid=f1ca20dd7aa0d9ea06b2e05cf6a3f7ce

thanks!

 

[alexzogh]

Soxfan!

I'm a cubs fan, but glad to see more Chicagoans. Where do you plan on launching? Given the relatively small size of,the rocket, and the challenging launch sites in the area that have a waiver high enough for this, I would really consider putting a tracker in it if you want to have a good chance at getting it back.

if you plan on launching at Bong, I'd be happy to lend you a GPS, or radio directional tracker for the fight.

i would also echo some of the other comments. It is unlikely surface mounted balsa fins will survive the up, and definitely won't survive the down given your terminal velocity. Because of the size of the sustainers fins, I would also consider a fiberglass layup tip-to-tip, and/or choose a different motor configuration (think smaller) for at least the first flight

 

[JRL303]

Very cool design and project. Take a look at Firestar for igniters.

 

[soxfan121]

Soxfan!

I'm a cubs fan, but glad to see more Chicagoans. Where do you plan on launching? Given the relatively small size of,the rocket, and the challenging launch sites in the area that have a waiver high enough for this, I would really consider putting a tracker in it if you want to have a good chance at getting it back.

if you plan on launching at Bong, I'd be happy to lend you a GPS, or radio directional tracker for the fight.

i would also echo some of the other comments. It is unlikely surface mounted balsa fins will survive the up, and definitely won't survive the down given your terminal velocity. Because of the size of the sustainers fins, I would also consider a fiberglass layup tip-to-tip, and/or choose a different motor configuration (think smaller) for at least the first flight

I will definitely be launching at Bong and that would be great if you could lend me a tracker are you planning on heading up there any dates this summer? For the body I'm using bluetube and i have decided to use G10/FR4. what type of tracker (s) do you have? i need to see if It will be usable in my rocket (29mm) and if i can pay you back if i lose it haha. that's really cool that you live in chicago where do you live?

 

[degreaser]

PML can provide pre-cut G10 fins.

https://publicmissiles.com/secure/ComponentsFins.asp

 

[soxfan121]

I'm using a 9v battery for the staging timer (to ignite the sustainer stage) and need 12v for the firestar igniters, i need an igniter that requires < or = to 9v to ignite that will also work in a g78 motor.

 

[soxfan121]

My first thoughts are 47MPH is too fast coming back down. Should be aiming for 20 MPH or less.

I could very well be missing something, but the aerotech G78's are Mojave Green propellant, the White Lightning is a G79. The impulses also don't match up to what I'm finding here: https://www.thrustcurve.org/motorsearch.jsp?id=581 Am I looking at the wrong motors?

Very cool design.

the one's you're looking at are g79w i'm using g78g

 

[soxfan121]

where do you buy 1/16" sheets of g10/fr4? also any suggestions on using it? (besides wearing a respirator and eye protection)

wow i feel slow...i accidentaly put .625 instead of .0625in. into my ork design HAHA ...when i saw the altitude go down 6,000ft... but when i got it right I actually found it boosted the altitude 200+ft new height is 7,677ft, however it goes slower: 750mph or 1100 ft/s

 

[Eat, sleep, and Fly]

-Both motors are aerotech G78G- (10&7) which are 133Ns each for a total of 266Ns of thrust. (equivalent to a 68% H motor) they are single use but i load them myself which makes them around $25 cheaper and no HAZMAT fee so $25 extra off my order! :grin:

When you say" I load them myself" what do you mean? Are they actually aerotech loads, or are they EX?

 

[CarVac]

When you say" I load them myself" what do you mean? Are they actually aerotech loads, or are they EX?

LMS is a certified single use type that you glue together yourself.

 

[Eat, sleep, and Fly]

LMS is a certified single use type that you glue together yourself.

... I definetley just had an "oh duh" moment!

 

[EeebeeE]

Going back to the fins...You are going to want at least 1/16" G-10. It would be better to have 3/32". Those things are raked back real far and at mach speeds even 1/8" plywood fins are going to rip off. You may even want to redesign them. It is a beautiful classic shape, but at mach speeds they will be impractical.

 

[soxfan121]

Going back to the fins...You are going to want at least 1/16" G-10. It would be better to have 3/32". Those things are raked back real far and at mach speeds even 1/8" plywood fins are going to rip off. You may even want to redesign them. It is a beautiful classic shape, but at mach speeds they will be impractical.

alright I'll see about redesigning them, I'm in school right now and then have a rocket club meeting after school so when i get home if i have time ill fix the fin design. thank's for pointing that out i'll see about making them thicker and redesigning them but also trying to cut down the weight of the rocket. thank's for all of the input guys!

 

[bobkrech]

I see several potential failure points on this design, so I'm going to ask a few questions on who the rocket works.

1.) In your simulation, when did you fire the second stage motor? And what was the airspeed when you fired the motor?

Your second stage should have a velocity of at least 150 fps when the second stage motor ignition occurs to insure that the rocket will be pointing up, not sideways or down at the end of the second stage burnout.

2.) By what design mechanism does the second stage separate from the booster?

You're not using BP motors so it's not a good idea to use the second stage igniton to push the booster away from the second stage as the booster will be severely damaged or destroyed by the second stage motor exhaust. At the least, the booster is not going to remain pointing up, so the delay may be all wrong for safe booster recovery.

A drag separation scheme should be employed so that the booster will start to separate on burnout, and by the time of the second stage ignition, is well separated from the second stage so it's flight path will not be altered by the firing of the second stage motor.

A cone and socket joint is the best way to accomplish this, and is how boosted darts separate. There are alternative methods, but in order to safely recover both stages safely, you must insure that the coupling between the stages will drag separate long before the second stage motor fires, but before the second stage velocity drops below 150 fps.

3.) When you did you simulation, did you use the actual weights of the booster and sustainer or did you let you simulation package calculate it from the internal database.

If you don't use the actual weights in the simulation, you are most likely to over esimate the altitude and thus will go over apogee and be well on the way down when your ejection charges fire which may cause a recovery failure by stripping the chute or zippering the airframe.

Also as a comment, for a first flight you should not be launch this rocket at dusk. If something happens, you will not see it, and I've seen a lot of rocket launched at night we the lights fail.

Bob

 

[CCotner]

Well Said. Also, a first-flight of a staged rocket should probably never happen at dusk or in less than perfect visibility, since there are so many things that can/do go wrong in 2-stage designs. I'd launch it out on the middle or back row, away from people, on a calm clear day first.

 

[soxfan121]

Well Said. Also, a first-flight of a staged rocket should probably never happen at dusk or in less than perfect visibility, since there are so many things that can/do go wrong in 2-stage designs. I'd launch it out on the middle or back row, away from people, on a calm clear day first.

CCotner and bobkrech i was actually thinking of a couple of these things today. I'm now using dual deploy on the sustainer stage (have not completed the design just yet) so i can make the need for a tracking device much less great or not needed at all and making it unnecessary to launch it at night because the lights are no longer needed. The rocket does separate from engine exhaust but that area is heavily reinforced to withstand the engine blast. the engine blast will be hitting a thick bulkhead layered thick in epoxy and the tube will have a layer of epoxy on the inside as well. the only thing that will be there is a hole for the igniter to pass through that will be plugged with epoxy, there is a aprox 5in. section of tube starting at the sustainer engine and ending a bit after that that will contain the staging timer. Bobkrech i just designed the rocket and whatever weights openrocket made the parts are the weights i assumed were correct and were therefore used in the simulations.

 

[Eat, sleep, and Fly]

CCotner and bobkrech i was actually thinking of a couple of these things today. I'm now using dual deploy on the sustainer stage (have not completed the design just yet) so i can make the need for a tracking device much less great or not needed at all and making it unnecessary to launch it at night because the lights are no longer needed. The rocket does separate from engine exhaust but that area is heavily reinforced to withstand the engine blast. the engine blast will be hitting a thick bulkhead layered thick in epoxy and the tube will have a layer of epoxy on the inside as well. the only thing that will be there is a hole for the igniter to pass through that will be plugged with epoxy, there is a aprox 5in. section of tube starting at the sustainer engine and ending a bit after that that will contain the staging timer. Bobkrech i just designed the rocket and whatever weights openrocket made the parts are the weights i assumed were correct and were therefore used in the simulations.

If you are launching at Bong, USE A TRACKER!!!!! I has the same mindset as you. I lost 2 rockets, and came awfully close to losing 2 more. One of the lost rockets I saw land. I am not talking about estes squirts either, these were decent size rockets, and they were not flying very high. At Bong, dual deploy will only cause you to lose an altimiter in addition to the rest of the rocket. $100 will by you an AT-2B unit, and you can use the WOOSH recievers. Bong is a relentless, downright horrible place to fly, but if yo have the guts to go >6,000ft there, please use a tracker.

 

[soxfan121]

If you are launching at Bong, USE A TRACKER!!!!! I has the same mindset as you. I lost 2 rockets, and came awfully close to losing 2 more. One of the lost rockets I saw land. I am not talking about estes squirts either, these were decent size rockets, and they were not flying very high. At Bong, dual deploy will only cause you to lose an altimiter in addition to the rest of the rocket. $100 will by you an AT-2B unit, and you can use the WOOSH recievers. Bong is a relentless, downright horrible place to fly, but if yo have the guts to go >6,000ft there, please use a tracker.

I'll look into a tracker, it's only $20 more than the dual deployment I was going to use anyway. I'll see what i can do about maybe not using dual deploy just tracking. I'm trying to keep this rocket lightweight and efficient as possible.

 

[soxfan121]

what do you guys think would happen if i used aerotech's EFC-1 (electronic ejection charge) instead of DD or tracking? what if i allowed the rocket to simply fall to around 750ft then deployed the parachute? would this be dangerous? if there are any other altitudes anyone would suggest if they think this is a good idea that would be great.Would it be a problem if the parachute deploys while the rocket is not vertical? I'm trying to keep this rocket, not necessarily as cheap as possible but not too expensive because I do not have a job so money is pretty tight when it comes to rocket materials and I already have an EFC-1... https://www.aerotech-rocketry.com/c...tions/EFC_Instructions/efc-1_instructions.pdf

 

[bobkrech]

In round numbers a rocket falling ballistic from ~6000 feet could be traveling as fast as 620 fps or 422 mph. A main parachute deploying at that velocity could generate a 1,500G shock load on deployment. This will destroy the chute and the rocket. It is not safe.

You're very enthusiastic about rocketry but I think you're going too fast, and if you continue down the path you are going, you will spend a lot of money and not have much success. Your signature shows you have launched 4 rockets this year and had 3 crashes. That's a success rate of 25% with single stage rockets. Successfully launching and recovering a 2 stage APCP rocket is much more difficult than a single stage rocket and right now IMO you do not have enough knowledge and skill to attempt the flight you are proposing and succeed. You need to join a club, find a mentor, and succcessfully launch and recover simple APCP rockets at least a dozen times before you attempt a complex 2-stage APCP rocket flight, and then you should do it with a larger than minimum diameter rocket so you can see that each stage of the flight works properly.

Bob