Composite motors and cold weather

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prfesser

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Yesterday it was 11F (-12C) when I headed to the Music City Missile Club launch, and it wasn't a whole lot warmer when I got there. Temperatures maxed out around 38F.

We experienced a disturbing number of chuffs, including a Big Bertha on a Q-Jet D-motor that never got off the pad, just sat there and burned all the propellant, then ejected.

Burn rate and ignite-ability of composite propellant both decrease with temperature. Lesson learned: when it's cold, pack motors to be used in a cooler with a few heated bricks to keep the contents warmed. Or warm the motors in an inside pocket to bring them close to room temperature before installing in the rocket. Then get the rocket on the pad and launch while the motor's still warm. No need to be frantically hasty, once the motor is warm it will take a little while for the propellant inside to cool down.

Best -- Terry
 

waltr

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Our last club lauch we also had a lot of motors not igniting and one of mine chuffed but did light and go. High temperature in the low 30's F.
Seems the AeroTech igniters were not getting the motors going. I gave several DIY igniters away for launches did not light the motors after two or three failures with Aerotech igniters. My DIY igniters use Procast (BKNO3+V) from QuickBurst. All motors with a ProCast igniter light right off. My one chuff was on an Aerotech igniter.
No one seemed to have issues with BP motors, only composite motors.
 

Steve Shannon

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Yesterday it was 11F (-12C) when I headed to the Music City Missile Club launch, and it wasn't a whole lot warmer when I got there. Temperatures maxed out around 38F.

We experienced a disturbing number of chuffs, including a Big Bertha on a Q-Jet D-motor that never got off the pad, just sat there and burned all the propellant, then ejected.

Burn rate and ignite-ability of composite propellant both decrease with temperature. Lesson learned: when it's cold, pack motors to be used in a cooler with a few heated bricks to keep the contents warmed. Or warm the motors in an inside pocket to bring them close to room temperature before installing in the rocket. Then get the rocket on the pad and launch while the motor's still warm. No need to be frantically hasty, once the motor is warm it will take a little while for the propellant inside to cool down.

Best -- Terry

That’s exactly what I witnessed when I had some local TARC teams flying during the winter.
 

UhClem

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Ignition at cold temperatures is more difficult with marginal igniters. With good ones, not so much. I know that things like the ATACMS are routinely chilled to -40C prior to launch at WSMR just to show that they meet that requirement.

I wouldn't blame the Q-jet problem on the cold since I watched a flier have four straight fail in a similar way on a warm day.
 

Buckeye

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Same here. About 20 deg F, but sunny. It was like the pressure of the igniter initially launched the rocket before the Q-Jet finally ignited. Kinda like a two-stage. The Q-jet burn was rather wimpy, as were some 24/40 AT motors. Estes black powder motors fared much better.

However, I don't notice much difficulty with High Power motors in the cold.
 

wonderboy

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Does anyone have more any ideas for keeping motors warm while at a launch when vehicles and a power-source aren't nearby? I like the cooler and warm bricks idea. I was thinking if the cooler was small enough, perhaps some of those chemical handwarmers.
 

dhbarr

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Does anyone have more any ideas for keeping motors warm while at a launch when vehicles and a power-source aren't nearby? I like the cooler and warm bricks idea. I was thinking if the cooler was small enough, perhaps some of those chemical handwarmers.
The thing about insulated boxes is every time you open the lid you lose 100% of your warm air. Maybe a side opening?
 

prfesser

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Does anyone have more any ideas for keeping motors warm while at a launch when vehicles and a power-source aren't nearby? I like the cooler and warm bricks idea. I was thinking if the cooler was small enough, perhaps some of those chemical handwarmers.
I think you'd find that placing a few bricks in front of the furnace vent the night before, then into a small cooler, would keep motors warm enough for some hours. I might be wrong.

Best -- Terry
 

High Desert Rocketry

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We heat up rice bags in the microwave at night as hand warmers for working at the test stand prior to firing in the morning. Cheap and reusable...I also use it at home under my pillow so we don't run the furnace at night. Just a piece of cloth sewn into a 8 x 8" bag with about 2 pounds of rice.

I would imagine a few pounds of warmed rice bags in a cooler would last a long time and also, if needed, help warm cold hands. Back in my younger winter mountaineering days, one of the things we would often do was fill one and two-liter soda bottles with warm water and put in the foot section of our sleeping bags for the night and then have water without needing to melt snow for the next day's drinking water.

Feb 4 2022 UC Berkeley liquid bi-propellant test stand GSE preparations:

UC Berkeley Feb 5 2022 at night.jpg



UC Berkeley at night.jpg
 

bad_idea

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I flew a 7 motor Q-Jet cluster recently in ~15F temps, all ignited just fine.
What igniters did you use, and what sort of controller? I've been working with Estes BP motors in my small clustering because the BP motors are easy to light very consistently with the MJG BP starters, but I'd be interested in moving to Q-Jets for some flights if I could achieve equal reliability.
 

boomtube-mk2

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Keep in mind that in cold weather the batteries being used for the launch system are not operating at their best.
Unless you are keeping them warm somehow.
 

Bat-mite

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I heat my motors by blowing a propane torch up the nozzle end. It gets hot REAL FAST! :clapping: :eggnog:
 
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