Adrian

Wikipedia gives the stagnation temperature, for air, as Tstag/Tamb = 1 + .2M^2. So for Mach 3, the ratio of absolute temperature would be 1+ .2*9, or 2.8. So for 300K ambient temperature, the stagna...

Nice pictures, Chad. That really shows why someone might want to keep the fins swept back enough to stay within the Mach cone angle. I agree with Chris that sweeping the fins to 74 degrees would be ...

It's kind of a shame that you can't just graph or predict dynamic pressure in rocksim though. But you can graph density and velocity, so it's pretty easy from there.

Oops. I just realized I forgot to convert from Newtons to lbs in the last wind shear calculations, so the 375 N converts to 86 lbs, which is right about what Chris calculated the 2nd time. I think w...

Rocksim indeed lets you use a launch tower that is 5000 feet high, and enter 150 ft/sec of cross-wind. When I ran it, it predicted that such a situation would result in just under 300 N*m of torque w...

Ok, 76 lbs is a lot more reasonable than stacking 10 SUVs on the end of the tube. I think i'll use rocksim to double check. It provides restoring torque as an optionin the graphs. I'll see if it let'...

Well, after some calculations... Ah, the cool refreshing sound of real engineering. Very interesting results. 150 ft/sec of instant shear is a pretty conservative worst case, but it shows the margin w...

Good comments on the fins; the Mach cone angle at M3.5 is about 16 degrees. So these would need to have a really long root chord and short tip length. That alone will do wonders to reduce the flutt...

If one would be fun, two would be better, so tell you what. You and John make the booster, Chris and I will make the sustainer, and we'll hit 100 kft together. 😆

Cool. I'm interested. You would definitely want a Von Karman cone for it. I can ask my friend who did the mandrel for my 38mm VK cone to do the same thing in 75mm. The length may exceed what he ...

Thanks Bruce. The altitude competitions are more fun when more people are playing, so I'm glad John Wilke is back, John Bixler is in it, and Chad and some others are getting into it too.

Yes, you are right. I remembered the dry weight wrong. My calcs show exactly 500 grams, but that still puts it over what you recommend and what Adrian's dry weight probably was. I'll take another look...

This was the second annual Memorial Day a**hole apparently launches a rocket near a plane event.

Congratulations, John. Dang, that's some impressive simulation. Any details for your rocket? Where did it land? Pictures?

Many flyers more experienced than I have warned about the issues near Mach 2. For my 30K shot last year, I added a significant amount of weight, as I didn't want to mess w/ the velocities that I was ...