[big-bang]

dear all,,
i have a rocket model .
but i cant analysis What happens !
for ex i dont know for better flight we must have more pressure or more velocity in The output of rocket?
and Whether this modeling is good for flight if not why?
thanks

[ARTem]

Hello, big-bang.
First of all, you should ask yourself what really you want from your model (distance range, flight velocity, amount of useful mass, etc.).
You can use Meshchersky equation to evaluate for yourself contribution to impulse from pressure difference (p_atm-p_nozzleCut)*F_nozzleCut and mass flow rate (and of course, it's mass flow of combustion products that moves rockets).
Of course, modeling is good not just for flight but for all engineering applications.
You can evaluate friction coefficient at different altitudes, impulse given to rocket from fuel and nozzle configuration, heat taken by rocket shell from air and hot combustion products, stress in rocket components due to start acceleration and maneuvers and etc.