Chris LaPanse

What kind of shroud line length would they have? I may be interested in one of the 48″ models.John: if they’re anything like the Rocket Rage, they’re kind of a pain to pack, but once you get them packed, they’re…   Read more»

You shouldn’t have to contact any witnesses beforehand – I know there will be plenty of people (me included) willing to sign off on a L2 at just about any launch. As for the test stuff, I’m not sure. I…   Read more»

Yes it was – it drifted much farther and in a different direction than expected. Glad to have it back – thanks very much to whomever returned it.

It’s definitely not the norm, that’s for sure. I had my first CATO larger than a D motor on Saturday. I’m not sure why there were so many failures, but hopefully, the trend will change next month.

Tim: will you have any of the Aerotech 38mm forward closures that don’t have a delay well (“Endburn Style”, or something like that)?Oh, and I’ll make sure to bring my 38-29 adapter for the Wildman – I may have to…   Read more»

Excellent :DI’ll have my Wildman Junior ready, so I’ll try some of the 38 H or I motors. I also managed to snag an I59WN longburning boost-sustain (I think that’s what Aerotech calls it) motor at LDRS, so I’ll try…   Read more»

Hobby epoxy would work fine if you wanted (15min probably – the 5min cures before it can really soak in, though it won’t really soak into the fiberglass at all regardless), although I prefer West System or Pro-Set. They’re more…   Read more»

Keep in mind that Adrian was assuming that CF could withstand 62,500 pounds per square inch without trouble. That would require near perfect CF work – probably with a high pressure, high temperature cure and top grade epoxy. Realistically, most…   Read more»

Great discussion….for the fin planform, there is the option to go with short fins with minimal sweep and as sharp a LE as you can make to reduce pressure wave. Think of an F-104 Starfighter wing or a Nike rocket…   Read more»

Well, I just ran it through rocksim, and rocksim seems to think the total force would peak at ~220lbf (that’s not too far from my value of ~72lbs on a single fin, considering all of the assumptions that I had…   Read more»

New calculations:(these ones are right, I promise)New dynamic pressure: 86.4 PSINew lifting force on a single fin: 72.6lbsNew thickness required (ignoring flutter): 0.019 inches of top, aerospace grade CF.New peak stress within 1/8″ thick fin in this scenario: 3500PSI (which…   Read more»

On a related note – it’s amazing how fast you forget things once you’re out of school for the summer. Things like how to properly read the table in the back of the aerodynamics textbook. (apparently, 1.9270 and 1.9270*10^-3 are…   Read more»

8 or 10 layers sounds like a bit much – you only need to build it up to roughly 1/8″ plate. Anyone know how many layers there are in 1/8″ plate CF?

That’s why I mentioned starting with relatively thin plate, and then adding quite a few layers of T2T. That in essence makes the entire fin can one piece of CF, and that should allow for these kinds of loads.

Well, after some calculations, it appears that 0.083″ fins are all that is needed at a minimum, at least for my design. That is using the assumption of a launch at 4k ASL (black rock, roughly), and that max Q…   Read more»

Well, my rough single stage sim to 40k or so with a 3kg rocket would pull around 50G on its way to M3.2. The acceleration shouldn’t be a problem – Adrian’s I powered shot did fine with greater acceleration than…   Read more»

I believe that is accurate, though we only touched on supersonic flight in my Vehicle Design and Performance class last semester. Once school starts up again, I’ll be taking 3000 level aerodynamics, and I could ask my professor about that…   Read more»

Well, I’ve put together some rough sims, and even with some fairly bad assumptions, I’m able to get some sims as high as 80k (with something like 40 seconds supersonic) on a 2-stage M3000 to J570, and 42k for a…   Read more»

They should definitely be within the mach cone, IMHO. Even if you assume a ridiculously short rocket (say, 1 foot longer than the casing), that allows for something like a 17 inch semi span before you hit the shock wave…   Read more»

It’s not the weight for the sake of weight, it’s the moment arm of having high density, high mass fins out far from the centerline trying to lever the fins off the body. Use low mass material – hell I…   Read more»