Author Topic: BfX atmospheric conditions  (Read 3357 times)

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BfX atmospheric conditions
« on: February 11, 2011, 12:37:34 AM »
Dear all,
Lately I was confused which atmospheric conditions I used in BfX - it was too long ago to remember and it seemed I also forgot the physics behind the drag functions.

Okay. Drag functions are independend of atmospheric conditions.


In the calculation of drag you have to use a density of air. In BfX the ICAO conditions are used (15 degrees C and 101324,6 Pascal 0% humidity), which are common for present day ballistic programs. Just checked the code - I am sure again - it holds for any BfX drag function

There is also the US Army standard meteo conditions (15 degrees C and 99991,6 Pascal), frequently used in the past. BFX_C which is used to convert ballistic coefficients, contains a bug thatI will soon fix. It incorrectly converts the ballistic coeficient as it assumes that BfX uses the US Army standard meteo conditions. if you enter
=BfX_C() and you  see the output BfX_C(T=15 [Celcius]; P=99999.76 [Pascal] []) then this is erronuous.

The new version will show BfX_C(T=15 [Celcius]; P=101324,6 [Pascal])

Expect the correction soon.


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Re: BfX atmospheric conditions
« Reply #1 on: February 11, 2011, 01:28:39 AM »
Bug in BfX_C is fixed