Open Rocket Safe Launch Conditions

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kjkcolorado

kjkcolorado

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Working on a scratch build design in Open Rocket. I'm running some simulations to get an idea of performance with different motors. I'm missing something in terms of identifying where to find values equating to safe launch conditions such as thrust to weight ratio. In trying to find the smallest motor I could safely use with my design, I kept trying simulations with smaller and smaller motors and never saw any warnings even with motors I know would not provide enough thrust for a safe launch. Help...
 
kjkcolorado said:
Working on a scratch build design in Open Rocket. I'm running some simulations to get an idea of performance with different motors. I'm missing something in terms of identifying where to find values equating to safe launch conditions such as thrust to weight ratio. In trying to find the smallest motor I could safely use with my design, I kept trying simulations with smaller and smaller motors and never saw any warnings even with motors I know would not provide enough thrust for a safe launch. Help...
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You have a good, modern simulation software in your hands. You don't need old-time rules of thumb like T/W ratio.

If you want warning messages and clues on how to interpret the data, then use Thrustcurve, or perhaps wRASP32.

In OR, you need to dig into the numbers and graphs and make your own assessment. To the best of my knowledge, there are no warning lights. Look for 50 fps minimum launch rod velocity (more with cross wind) and positive stability margin throughout the flight.
 
I wouldn't just call Open Rocket 'good'. Given all it can do and the fact that the developers have made it available to all for free makes it GREAT! That's why it surprises me that there aren't some built in safety checks for simulations, such as velocity off the launch rod or thrust/weight ratio.
 
OpenRocket does produce warnings for various situations. In the simulation table's first column a red '!' indicates there are warnings for that simulation. Click on it and they will be displayed. Examples of these warnings are low launch rod velocity, instability, high speed recovery deployment. It does not do thrust/weight ratio because that is more of a rule of thumb for use on the field.

Kevin
 

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