Don't know if speed of sound has been exceeded by "model" rockets or if it is allowed. Bet Brett knows the answer.
Oh, certainly! Not at all uncommon, the hard part has always been to prove it. It was quite a trick in the late 60's-early 70s, and we had a few we thought *may* have done it in the early 70's. FSI even sold a kit purported to manage it, although most were pretty skeptical given that it was staged BP motors. It moved right along! The biggest engine we could get was an F, and it was darn near impossible to get any sort of speed-measuring payload in the model, AND, have it light enough to still have sufficient speed. You can't hear the supersonic "pop" since the angle WRT the ground is very small. People tried color-changing paint that would shift at a particular temperature but it didn't stay fast enough long enough to transfer any significant heat.
By the way, light weight is important to ultimate speed, most models above a D can pretty easily be built too light for maximum altitude. Too light, and it gets moving fast, but the speed dies off before it gets very high. Like throwing a ping-pong ball. With a heavier model the speed doesn't get as high, but it keeps going. So there's not a lot of motivation to save weight, frequently you need to add ballast to optimize the performance.
Now, it's almost a trivial issue. Even one of the motors in the Saturn V model, used for maximum performance, is capable of going supersonic quite easily with a substantial payload, like an integrating accelerometer. Actually the passage of the shock wave past the barometer port is kind of an issue, because a barometric switch is sometimes used to deploy the recovery system, and the shock wave pressure can mimic low altitude. Most of the deployment electronics packages contain an "mach inhibit" system that prevents this. Point being, supersonic is so common that they are building it into $30 deployment packages.
Actually, I am not much of a fan of HPR, and part of the reason is stuff like this launch. Maybe I am just an old stick in the mud, but you could put a rocket to 250,000 feet or more with all that propulsion. It's a neat flight, but seems like kind of a waste.
I am also far from an HPR expert - Steve Fitton and Larry Foster are much more experienced in HPR than I am. I was an old Modroc competitor, and I finished in the Top 20 in NAR season points at recently as 2000, I think. My last three or four contest-qualifying flights were OOS and some sort of record, with various caveats to invalidate them. Best two were a 35 minute D Dual Eggloft flight (~8:30 timed, seen to land and recovered at ~35 minutes, after flying from one side of Livermore to the other, including right over the top of the Lawrence Livermore Labs (DQed, egg cracked)), and a 20+ minute OOS flight in 1/2A Flexwing Glider, last seen headed west at about 1500 feet and climbing rapidly (unofficial test flight).
Brett
Topic: "It's only a model" Saturn V (Read 7436 times)