I think we're very close to solving this challenge. It looks like your fins and booster were just fine, as was your nosecone. This issue now is the upper airframe. The challenge is to get it as strong as possible while maintaining RF transparency. Perhaps a custom thick walled fiberglass tube, along with a custom fit nose cone?
I missed that part of the build, what I remember was "As kevin said, it's ordinary cf from performance rocketry. I'm not too worried about its strength, since it will actually be shorter than the motor casing. As a result, the casing will act as a full length aluminum coupler, pretty much eliminating any chance of the tube buckling. It also should never have a very high heat load, since it will never be directly exposed to the airstream. Honestly, the tube is the one part of the rocket that doesn't terribly concern me." So the motor did not go all the way to the nosecone shoulder?
Awesome flight, sorry it failed. Better materials...I'm especially glad we didn't fly now: even reinforced, I doubt our front end tube would have been strong enough. Especially since our nosecone design is so much heavier than yours... This is really surprisingly hard to do, isn't it?
What were your recovery plans? Apogee detection/deployment/etc.. I'm curious to see what you came up with, especially since we're re-designing that from scratch right now for our attempt.
Did the electronics survive?
Any data from the altimeters?
Ted
That's actually one of my more...um...ambitious? Yeah we'll go with ambitious here. That's one of my more ambitious ideas for a future project. Make the entire rocket one solid, glued-together piece, with no seams at all, and then eject the entire motor casing out the back for recovery. It has substantial structural and aerodynamic benefits, since there's no external seams at all, and the nose cannot possibly wobble, but there's the difficulty of kicking 4 feet and 10 pounds or so of motor case out the back reliably, with as minimal of a chance of binding as possible. I think it would be doable though. It also introduces some unique headaches with the electronics design, but at least at the moment, it's my leading contender for my next design when I get around to rebuilding. I'll need to figure out a full recovery schematic, but I'm cautiously optimistic about the possibilities here.Now, I have little experience with this.... but.... what if instead of the nose cone coming off, the laundry came out the rear end? Then you could simply secure the nosecone on (or even mold it into the body tube). Just a random Idea I had.
Shame this didn't work. I should point out I've been checking here almost twice a day waiting for a flight report...
Gotcha, and I was giving you a hard time on the rebuilding bit.
-Kevin
For deployment, I had a 24mm CF tube on top of my e-bay that was about 5 inches long, and there was effectively a piston consisting of a 24mm CF coupler and a 7/8" (I think - it was whatever size fit) oak dowel. There was a 0.4 gram charge inside the 24mm tube, and the piston was shear pinned in, so effectively, it was 0.4 grams of black powder inside an unvented 24mm tube less than half an inch long. The idea was to contain the pressure to allow the black powder to completely burn at altitude, and as the piston was pushed out, the dowel (which was against a bulkhead near the tip of the nose cone) would push the nose off, so I never had to pressurize the internal volume of the nosecone to deploy.
I hope you find the time and money to do this. Also, an onboard keychain camera of some sort
cjl said:As I said, I do have several ideas, but they will have to wait for that magical combination of funding and motivation.
I think it's definitely doable though - I may try again at BALLS next year, regardless of the status of the CTI prize, since as much as anything, I'm doing it for my own enjoyment and curiosity.
I think if one wants to learn more about the limits of composites from a flight like this, an onboard camera is a good idea. It is hard to know exactly what happened this time around, so what new information do we have for the next attempt? The camera would be helpful to confirm that the fins did not come off first, for example.
Correct - I shear pinned the piston together, but the nosecone itself was designed to be held on with drag forces alone. Given that the failure happened while the motor was still putting out over a thousand pounds of thrust, and the rocket was in the neighborhood of mach 3, I doubt that it could have been an internal pressure separation. I have a few more calculations to run on that before I can be absolutely certain, but the nose cone was well vented, and at that point in the flight, should have been held on by more than 150 pounds of drag forces and 100 pounds of inertial forces, which should make pressure separation at that altitude impossible (even if it had been unvented, the pressure differential should have been insufficient to move the cone).Chris,
Sorry to hear about the shred. Great try, and I hope you do try again. The rocket looked awesome coming off the pad.
Your deployment system sounds very innovative. Nice way to handle the issue of BP burn at altitude. It sounds like you just shear pinned the piston, and not the nose itself. How big was your vent hole? Could the problem have been pressure separation, or at least enough separation to have caused the imperfection in the fit that you hypothesized in post #428?
Jackson made a vent hole sizing worksheet that uses pressure data from RockSim to calculate a flow rate out of the hole and corresponding pressure over time. I’ll get after him to post it on a new thread, but in the meantime, I can have him PM it to you, if you want.
Wouldn't a magnetic switch work?
I think if one wants to learn more about the limits of composites from a flight like this, an onboard camera is a good idea. It is hard to know exactly what happened this time around, so what new information do we have for the next attempt? The camera would be helpful to confirm that the fins did not come off first, for example.
[Crazy Idea/] Is there any chance of using a high speed ground based camera for data analysis? I mean these failures happen at such low altitude that it must be possible with the right tracking to catch it all on high speed tape. Chris, I know you have done some work at Wallops so I know you must have some experience with the professional world of optical tracking. [crazy idea off/]
Good try Chris. Very proud of you for your efforts.
Bryce
That would be awesome - the ground based optical tracking produces some incredible results, and you're correct that I've seen it used at Wallops. Sadly, it's way beyond my (or I suspect any other amateur) capability in terms of both equipment and cost.
I had a magnetic switch. The electronics were too far towards the middle of the rocket though, so the E-bay could be assembled just fine, but the nose had to be off to arm. As I said, this will definitely need a better design for next time.
I had a magnetic switch. The electronics were too far towards the middle of the rocket though, so the E-bay could be assembled just fine, but the nose had to be off to arm. As I said, this will definitely need a better design for next time.
A big magnet should have been enough for that. Did you have one?
The upper tube was actually the older style (cloth based) PR FG tube, not the newer filament wound stuff. As for rebuilding? As I said, I do have several ideas, but they will have to wait for that magical combination of funding and motivation.
I don't know about the rest of you guys, but I'm sufficiently intriqued enough to see some team sponsoring of the next project by Chris.
In fact, if he keeps us posted for next year, I'll ante up $ome.
I won't be doing any Mach 3 flights myself anytime soon, but I wouldn't mind seeing this one suceed.
One or two provisos...HE designs it - we offer advice and only advice that he picks and chooses.
He keeps receipts and we get to see it fly.
I would be willing to donate to a project of his also.
+1 from me.
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