For those who have forgotten this is what we are to be talking about.
The statement "...if it actually holds together....." gives me the creeps as the one running the launch.
I would really like to see "I have tested all the materials successfully, have worked out the issues as I worked up in impulse". Just a shot in the dark and hope it all holds does not give me a warm fuzzy.
I know it takes a lot of time and money to do this but we get a lot of rockets burning in.
Mark
Mark,
I say that because, quite honestly, I have never flown this fast or high before, and no other commercial motor that I am aware of can push a rocket this high and fast. Could I say that I am absolutely sure that it will work? No, not without lying. Since there have been several attempts, every one of which has shredded, it's still somewhat of an unknown where exactly the line is between a rocket which will survive an N5800 and one which will not. When I originally came up with this concept, a bit over a year ago, I was pretty confident it would hold together, and I have refined the design substantially since then. However, since the concept, a number of other rocketeers have attempted to fly this motor in a minimum diameter rocket, and to date, all of them have shredded, including some very impressively constructed rockets. Looking at these past attempts has significantly changed my design, and it does make me wonder what exactly is required to make this work.
I have successfully flown up to around mach 2 before, and I have discussed the project extensively with people who have flown in the neighborhood of mach 3. Since my local club has a standing 20k waiver with windows to 35k, we have a number of altitude junkies, and as a result, high performance flights tend to be somewhat more common at my local club than most places in the US, and that has resulted in a number of people with fairly extensive experience at high altitude, high speed flights. However, the fact is, the number of currently active rocketeers who have successfully flown and recovered a mach 4 class rocket could probably be counted on one hand, at least as far as I know. As for working my way up to this in impulse? If you actually run the simulations, the only thing that might even come close in speed would be a 75mm minimum diameter on the new 75mm 6xl imax, and even that doesn't get up to the same kind of speed as this does. Part of the reason this interests me is that it is uncharted territory - it's at least somewhat well established what it takes to survive at mach 3, but mach 4 is still somewhat of the unknown, at least as far as amateur rocketry is concerned.
I will say that I have done extensive simulation and engineering on this design, and I have been thinking over it since more than a year ago, so this isn't something just drawn up on a napkin one day. Do I think it has a good chance of surviving? Yes, and I am doing everything I can to increase those chances. The fins should have a substantial margin of safety in terms of flutter and absolute strength requirements, and as I said, I am coating all of the high heat surfaces in materials rated to more than 2000F, which should be higher than the peak stagnation temperature which the rocket experiences during boost. In addition, all of the structural joints and regions are made with 500F rated epoxy, so that any heat which soaks through the coating (or comes from the casing) is unable to damage or weaken the structure during coast. The rocket is designed with only one separation point, with the motor casing as the coupler, so it should be basically immune to coupler failure, and the separation point is more robust than most.
Despite all of this effort, it is absolutely an experimental launch, testing both techniques and flight conditions which are extremely uncommon in amateur rocketry. That's why I'm bringing it to Balls rather than, say, LDRS. To quote the Balls website:
BALLS 21 is a venue for projects that should NOT be flown publicly due to safety and legal restrictions. This may include, but is not limited to, LARGE rockets, complex staging or clustering, metal rockets, self designed and/or fabricated rocket motors and new technologies being developed or proven
I feel that this sums up my rocket nicely - it is an unusual rocket, being developed and proven for the first time. However, I do feel that a lot of time and thought has gone into this, and I have done my best to ensure that it will have the best possible chance of holding together during flight. If you have any specific concerns, please let me know - I would be glad to elaborate on how I plan to mitigate certain risks, or in the unlikely event that I haven't thought of a particular risk yet, I would much rather hear about it now than later.
Believe me, I understand your concern, and that is why I am doing my best to think of everything in advance, as well as sharing the design details before flight.
