Transonic Effects on Paper Rockets . . .

[markfsanderson]

Greetings!
Although I'm a pilot (SEL VFR only) and understand the basics about transonic/sonic flight etc, I've no idea how it might apply to rockets and the materials they're made of. The basics, as I've read them are something like if you are going 'near' or will exceed the speed of sound, fiberglass, carbon fibre, nose cones with metal tips are all good. What's not as clear to me is the transonic region, let say from .65 mach to .90 mach . . . or maybe the lower end of that should be higher? Not sure. My question is: I've built a LOC/Precision HyperLoc 163 w/stickershock stickers on top of 5 or 6 light coats of enamel paint and will be finishing it up with 3 coats of clear enamel. There are some 29mm/180 AT motors that Apogee recommends that exceed .65 mach, and the I motor on that list (not recommended) exceeds mach 1. To that end, what is a paper rockets 'speed limit'? Is there a maximum of number of flights that at near mach that rocket can endure before it 'self destructs' or becomes too weak to fly? Can I safely fly this rocket w/an I (eye) motor and have some hope of recovering it intact? I believe the simulated speed is about 1.4 mach? But not sure. Any insight would be appreciated . . . Oh - I love the rocket . . . don't want it to disappear into a black hole, but am curious about the boundaries . . . .

Mark!

 

[Nytrunner]

The transonic region starts at the speed where some airflow over the vehicle is supersonic, and ends when almost all airflow is now supersonic. This is highly dependent on geometry and airstream temperature, so its generally simplified to between M.8 and M1.2.

I don't yet fly supersonic, but I've flown cardboard and ply up to M.7. At that point just worry about making sure your fins are on solidly and won't flutter.
Body tubes are strong, it's the couplers that will cause problems with air turbulence

This may be an expensive proposition, but start with the lower power motors and step up as the flights are successful! (you love the rocket and want to fly it, yes?

Handing off to the folks that do fly cardboard past Mach:

 

[DaveW6DPS]

I think of transonic as .72 mach and up.

Most LOC rockets are pretty sturdy. I don't know of an actual speed limit recommendation. Transonic flight can cause cumulative damage, but so do many aspects of rocket flight. Cumulative damage is usually easy to spot before it become a shred hazard. You were probably (hopefully) taught to run your hand along the fuselage during a preflight. Rippling or stressed rivets indicate an airframe that has been over-stressed.
You can't always find it, but most of the time.
You should examine your rockets in a good preflight, also. any sign of buckling, delamination of the tube, etc., would indicate cumulative damage.

Of course, most of the time if the rocket isn't strong enough for transonic buffeting, it will simply shred.

If you are going supersonic, make sure you punch through the transonic quickly. Otherwise, choose a motor that will keep you under transonic.

 

[heada]

I've sent a LOC NukeProMaxx supersonic before. Plastic nosecone can do it, plywood fins can do it and cardboard body can do it. Make sure the fin attachment is strong and the rest is fine. I don't think paint starts peeling off until you're getting close to M2 but I've never gone that fast before.

 

[boatgeek]

I’ve seen LOC 54mm tubing and standard plastic nose cone go to Mach 1.6 with no damage. I’d worry above 2.0 but that’s a whole different kettle of fish.