I was thinking of good places to launch today (currently launching at the high school field). I'm in Michigan surrounded by farmland so usually if there aren't crops in the fields it's muddy.
Then I thought what about the middle of a frozen lake in the winter? Out on Saginaw Bay (Lake Huron) you can see for miles in any direction. Does the cold affect the motors? What about the rocket's flight in cold air? The only thing I can think of is the materials like fins and glues will be more brittle when frozen.
All BP motors need to be protected from thermal cycling, as Micromeister described. They have a much greater chance of failing when they have been allowed to get too cold for any extended period of time. 45° is a spring day; they can easily survive temps in that range. It becomes a problem with prolonged exposure to temps that are significantly below freezing, especially sub-zero temps. Composite propellent motors don't suffer from this problem. To protect against thermal cycling, store black powder motors in a sheltered, warm location during the cold winter months. At a winter launch, keep them in an inside coat pocket until you are ready to use them.A-D motors seem to do well in winter but I have seen E motors cato a lot when it gets around 45* or lower.
Verna
www.vernarockets.com
FWIW, I've seen 3 different people destroy 3 very nice rockets within 15 minutes of each other using E motors, at or just below 45* that had only been on the pads for about 5 minutes before launch. They came out of warm cars. The first I thought was a bad motor. The second a coincidence. The thrid made it obvious to me E's are sensitive to even minor cool temperatures.
On the same day I flew many A-D, including several clusters that had been out all day and after temps had fallen to about freezing with no problems. But I will say that of all the bp motors I have seen cato they have all been E's. Perhaps the larger the motor the more susceptible they are to temps.
Verna
www.vernarockets.com
I have launched Estes for 40 years and launch E9's like Amy Winehouse goes through cigerettes and I have never, ever seen an Estes engine CATO. Maybe they just ship the good stuff to Texas. oint:
The only times I've ever seen Estes motors CATO it has been E9's, and they've all been fairly recent. I think there's more to the story than temperature.
temperature cycling and humidity. the BP will expand when it gets hydrated, and it will expand when heated. the cycling will cause it to develop microfractures that when exposed to the flame front and pressure will crack and increase the pressure until the clay nozzle explodes.
those packages have printed cardboard backsides, that might prevent a rapid swing in humidity, but they will allow 'moisture' to enter(and leave) slowly. unless the motors are stored in a climate controlled space from manufature to your hands...they will be subject to humidity/temprature cycling. thats not even considering the possibility that they might have been dropped...say when the clerk picks them up, scans them then tosses them on the counter(seen that one, asked the clerk to not do that again).
rex
I have to go with the "breathable" cardboard idea. I have packages of A engines from 1972 with rusty igniters but the packages have never been opened.
Verna
www.vernarockets.com
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