# Help me with engines

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#### bat681987

##### New Member
can someone tell me the engine: preasur an engine has

for example "this is not a true statement" A engine:1pound

if you dont understand ill put it this way how much weight can engines F-J push up

I think I know what you're getting at.....

Check out https://www.thrustcurve.org/

Info on the graphs is at https://www.thrustcurve.org/background.shtml

There are thrust curves for virtually any rocket motor made. Some of the curves are in lbs of thrust....some are in Newtons. To convert Newtons to lbs divide the Newtons by 4.45.

As you look at the curves you will notice that thrust varies as the engine burns over time. Most of the curves will give you a maximum recommended lift off weight for that particular motor.

It's not as easy as saying that a "F" engine has "X" thrust since the "F" class is determined by the TOTAL impulse of the engine. In other words...how much thrust it delivers for the whole burn. Some engines burn longer that others.

Hope that helps,
John

Example: The Apogee F10. The F10 has a total of 80Ns, putting it in the F impulse class. The Aerotech F101 has a total of 79Ns of impulse, just about the same as the F10. One would think that since the F10 and the F101 have the same total energy, they will be able to "push" up the same amount.

Here's the kicker: The F10, having 10N of average thrust (2.2lbs for 8 seconds), would not be able to lift a rocket that would fly on the F101 (23lbs of energy for about 1.0 second. If you do the math, the numbers don't exactly add up, its rocket math )

thanks that helps out alot

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