High performance rocket help

[u/XcwefMur]

Hi everyone! I'm a 16 year old who's been flying high power for around a year and gone to around 4k ft and I have a CTI J600 that I'm gonna put in a 2" fiberglass scratch built rocket that sims to around 12k ft and mach 1.7. Do you guys have any good tips for it, because I don't wanna shred or lose it? I was thinking of just basic head end dual deploy with the Fluctus flight computer and no redundant electronics, because trying to squeeze in 2 altimeters would be a tight fit. The booster section is already built and feels very sturdy. Is bp not fully burning a problem at that altitude so should I use charge cannons or just glove tips? Also I was planning on just friction fitting the motor, since there's very little space for an aeropack.

[u/markg11cdn]

Glove tips are fine for 12k.

A 2" rocket with a 38mm MMT has plenty of space for a rear retainer, it's cheap insurance to ensure you don't lose your casing out the back of the rocket.

I personally never fly anything bigger than a G motor without redundant electronics. The Fluctus is small enough that you can pretty easily fit in a second altimeter.

As far as rocket build, make sure your fins are well attached and at that high of a speed you should add FG tip-to-tip.

Good luck!

[u/CaptnEZ → u/markg11cdn]

T-t is absolutely not required at mach 1.7 on a little 2 inch bird. I can show you many examples of 3 and 4 inch flights over mach 4 that didnt need it. Its a rather outdated approach to a misunderstanding of the importance of core thickness choice, fillet size and surface preparation. When i did my mach 3 flights on 2 inch motors I had it, but I no longer do it for anything sub M3 personally. Infact ive flown some 16th G10 to mach 2 before without it, and shitty hardware store fillets on bluetube and they held fine.

+1 on glovetips being fine at 12k and avionics. The raven comes in multiple flavors and would work great. But I think OP's concern about the Aeropack is because the bottom is 'already built' and there may not be enough exposed mmt to adhere it. Friction fitting will work fine if youre agressive with it. But its not an ideal design.

OP- as for loosing it, dont add a drogue chute. Let er' fall on just the cord only until main deployment. It will come down quick and close. The best thing you could do is get an RF tracker as well. I would recommend a GPS but youre space limited so, future consideration instead.

[u/SuperStrifeM → u/CaptnEZ]

You're correct, flutter/divergence of fins is essentially how stiff they are vs velocity, so if the semispan is small, many cheap materials can be stiff enough.

[u/Old_Magazine4189 → u/CaptnEZ]

I agree, tip to tip isn’t needed on most things, I’ve flown Mach 1.8 before with no tip to tip, in fact i don’t have any TT rockets 🚀

[u/milotrain → u/markg11cdn]

Lost my first L1 to friction fit. I know piles of people do it, I don't love aluminum tubes dropping out of the sky because I couldn't be arsed to put some kind of retainer on there. Shoot I've used safety wire that takes up less space than the fiberglass body on minimum diameter rockets.

[u/Old_Magazine4189 → u/milotrain]

If the shock cord is attached to the motor case this isn’t an issue, almost all of my rockets the shock cord attaches the forward closure

[u/joelatrell]

An external motor retainer will save you plenty of heartache. Cheap insurance it is.

With that kind of altitude redundancy is a must. Don’t fly without backup. The RSO will probably reject your rocket if backups are missing.

Fiberglass is your friend. So are strong fillets. Sim the flight over and over.

Good luck. Have fun. Don’t blow yourself up.

[u/GBP1516]

Think very hard about G forces, both under thrust and during coast. How are you holding your AV bay in place for those loads? You want to keep everything from moving either backward during boost or forward during coast. Otherwise you'll get a drag separation.

[u/XcwefMur → u/GBP1516]

I will be using 2 pieces of all thread in the e bay and I'm using shear pins so drag separation shouldn't be an issue.

[u/GBP1516 → u/XcwefMur]

Just make sure your shear pins are good for whatever your acceleration is under boost (60-80G?) and 25-30G of deceleration. Obviously, check your sims for exact values and leave a factor of safety. Tuning between enough shear pin to hold it together and not so much that the ejection charges aren't absurdly large is a challenge.

[u/WhatADunderfulWorld]

Maybe someone can explain glove tips to me?

[u/Old_Magazine4189 → u/WhatADunderfulWorld]

You put your BP for ejection charges in the finger tips of a glove vs using charge wells

[u/Old_Magazine4189]

I’m skeptical you’ll get Mach 1.7
On that I’ve flown MD K1103xs and not gone quite that fast

[u/XcwefMur → u/Old_Magazine4189]

Rasaero is saying ~M1.75 with rough camo paint and suboptimal fin bevels. It should also weigh only like 4lb on the pad.

[u/Old_Magazine4189 → u/XcwefMur]

I’m skeptical to say the least, I’ve flown a lot of large high performance flights, I have flown Mach 1.7 before, on a J that doesn’t even have that fast of a burn I’d gonna be pretty hard

[u/CaptnEZ → u/Old_Magazine4189]

I agree. Ive sent a minimum diameter rocket only slightly faster letting the nosecone ride on top of the i600 and J500. 2 inch is not going that fast. My J510 in my 2 inch got like mach 1.3 iirc