A sad day for 'copters.

[darthgriffin]

With no wind and overcast, 80 degree weather I decided to have a rare summer launch. My son's Dragonite broke a few shroud lines and somehow lost a fin, but my daughter's Cosmic Cobra flew perfectly. That was an abrupt end to the good flights. My Helicat and my daughter's Sky Twister both failed to deploy 'chutes and nose dived back to earth. Unfortunately they also decided to fly off to the side so instead of landing in the soft, wet grass of the park they landed in the hard AZ desert soil which is about as soft as concrete.


I assumed that my chute-inside-the-copter-blades technique had caused the NC to stick inside the BT, or that the ridiculous humidity, 66%, had caused them to stick. As I inspected them at home I found that the small, plastic pins the Helicat used as engine blocks had finally failed causing the motor to shoot up inside the first BT. I knew that would happen sooner or later to one of them so that explains one of them. The motor in the Sky Twister was still in place, but the clay cap that serves as a forward closure was still in place, well mostly.


I took the motors out of the other two rockets and a large piece of the clay cap fell out of the Cobra's motor (on bottom) and half of her wadding was still inside the body.

Can this much clay remaining in place prevent the ejection charge enough to cause a lawn dart? This level of humidity is very rare in AZ. Does anyone know if humidity has an effect on motor performance?

[blackbrandt]

That happened to a D12-3 that I launched. Half of the clay was still there, causing my Optima to Core Sample.

[cwbullet]

Darn, I like that kit.

[chadrog]

Humidity is often in the 90% range throughout the summer here, I don't think that was the issue. I'd kill for 66% right now.

[sandman]

I do have 5 left at a real close out bargain price! $7.00 each!

http://www.excelsiorrocketry.com/pro...id_product=539

[closet astronaut]

Here in Fl. the humidity is 80-90% every day. My last launch was July 4 a nasty day, soupy, muggy and hot, no problems with any launch as far as deployment. The last alunch day I had I used motors that had spent twelve years in the attic and had no problems.

[darthgriffin]

Well, I'll rule out the humidity then. I have heard people say that high humidity messes with their paining so I've been holding off on all my paint work until the monsoons pass.

I've heard that rocket motors are designed to burn, and the nozzles are shaped, so that the exiting gasses produce an even thrust. If the propellant is not burning evenly inside the motor could that account for the rockets veering off to one side? There was no wind and these heavy rockets have never been much for weather cocking anyway; especially when compared to the Dragonite, which flew strait up, as did the Cobra.