Builds Rockets for NASA
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- Aug 27, 2011
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My doubts are a bit different. And I am with Drew that likely if this goes unstable, it will STAY unstable. Interestingly I think the most dangerous rockets in terms of instability are those that are temporarily unstable. Scary flight at NSL 2020 where a high power rocket did a near complete loop about 50-100 feet off the pad, fortunately the trajectory on the final segment was at least 45 degrees vertical and perhaps more importantly (and frighteningly likely purely fortuitously) AWAY from the flight line and parking lot. It’s these rockets that start unstable, get a no vertical trajectory, and then get up enough speed to BECOME stable and therefore pick up kinetic energy that are scary. Rockets that become and STAY unstable tend to sky write, they just spin and twist randomly, main risk is that they fall on someone or something and cause injury because of their mass rather than their velocity, or they are fire risk because they come to earth with motors, delays, or ejection charges still active.I feel rather hypocritical urging @Senior Space Cadet not to launch his dirt dive recovery rocket, even on a deserted soccer field miles from anyone, while saying this looks like a cool experiment and eagerly waiting for the results. I assume you've got a 'chute or streamer in there, but that's not the point. It looks potentially dangerous, to a significantly greater (if not very large) degree than most of the rockets any of us launch.
You're certain that tension in the strings keep them rigid enough to transfer force to the body, but I confess I'm skeptical (not that I'm anywhere near sure they won't). You're not so sure it will work that way after burnout, and I have very little doubt on that part; it won't. (You aptly point out that at that point it's a hazard only to the rocket, assuming a 'chute or streamer deploys.)
Still, because of the substantially larger than normal chance of totally unpredictable behavior immediately upon leaving the launch rod, please don't launch this anywhere near other people.
Do you plan to prop the drive section up on the rod so that the ring is dangling, i.e. the strings start out straight?
I am curious about your concern after burn out, I am thinking the drag of the tail will be greater than the drag on the nose and tube section, so I expect that it won’t become significantly MORE unstable than it may be during active boost, but often the intuitive answer isn‘t correct. And if it DOES become unstable during the delay/coast phase, unless the delay is really long it is unlikely to re-orient node down and pick up enough speed to “go ballistic” before ejection charge fires.
so risks from this rocket are significantly different, if fecal turbine interaction occurs, I expect it will be immediately as it leaves the pad, it will sky write and flop to the ground possibly still under thrust, and be a fire danger (this is one rocket where I would keep an extinguisher handy unless you are launch on playa. The “other” rocket discussed is a “missile”, I don’t care if it spins a bit and has a blunt nose cone, the EXPECTATION is a ballistic return. That takes it out of the “model rocket” category. At that point it is either a weapon or a dangerous experiment.
this pushes the envelope, but at least has some science behind it. Still a FAR pad bird (or better, fired with no spectators in a remote location with a very low fire/brush danger.