How high will a bullet travel?

[Plasmech]

I want to make a spreadsheet that calculates how high different caliber bullets will go if fired straight up. Note that this (actually firing straight up) is something that should never be done in any corcumstance.

So I have the muzzle velocity, the bullet weight, and the drag coefficient. Let's assume we're firing from sea level. I do not know how to employ the drag coefficient, and am not sure how to take into account thinning air as the altitude increass. Please help!

I can do this calc no problem if we assume we're in a vacuum, just convert initial kinetic energy into final potential energy. Just not sure how to take the air into account.

 

[GregLocock]

I'm a bit frightened that any engineer can't work this out for themselves.

F=1/2*rho*Cd*A*v^2


Note that the drag coefficient varies substantially with speed, especially in the transonic region.


Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

That'll get you an answer, but bullet drag varies drastically as velocity decreases, in general.

I can tell you that a 105-mm APFSDS round is supposed to reach about 21 km altitude at 45º superelevation as calculated by a VERY expensive simulation program.

TTFN

FAQ731-376

 

[GregLocock]

http://www.geocities.com/greglocock/ballist9.zip

may help

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Plasmech]

Greg,

I would not consider this calculation a fundamental one. In a vacuum it's first week high school physics. Add the air of varying density and it's not exactly a cakewalk.

 

[Plasmech]

IR: what's firing the 105mm Sabot? I thought they were mostly 120mm, fired from the M1A1's smoothbore gun...

 

[GregLocock]

You should still know what to do with drag, unless you are an electrical engineer I suppose.

As to the variation of atmospheric density with altitude

http://www.grc.nasa.gov/

http://WWW/K-12/airplane/atmos.html

The program I mention above takes both the change in Cd and rho into effect.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

The 120-mm smooth bore was not the first choice for the M1

TTFN

FAQ731-376