Calculating flight time for indirect fire
- Thread starter Zparkz
- Start date
Border Reiver
SOC-14 1K
This might get a little complicated.
Factors that affect time of flight are,
Barrel Length.
Shell Charge
Atmospheric pressure.
Humidity
Gun's muzzle velocity.
Shell Weight.
Planetary Rotation.
Weather; precipitation & wind for example.
Barrel temperature.
Charge Temperature.
Barrel elevation.
Air Density.
And more. In the good old days when I was at RSA Larkhill they would teach us ""emergency manual firing" which involved a slide rule, an inch and a half thick book of firing tables, various plotting boards, graphs and a sheaf of meteorology reports. Apparently they don't teach it anymore and I met a number of senior officers surprised to find I knew how to do it.
The whole thing would take minutes to calculate bearing, elevation, time of flight and most suitable charge for any given target. A specialised computer like Gunzen or FCA can do the whole thing in a second.
So in answer to your question, nope, no easy way to calculate it.
Factors that affect time of flight are,
Barrel Length.
Shell Charge
Atmospheric pressure.
Humidity
Gun's muzzle velocity.
Shell Weight.
Planetary Rotation.
Weather; precipitation & wind for example.
Barrel temperature.
Charge Temperature.
Barrel elevation.
Air Density.
And more. In the good old days when I was at RSA Larkhill they would teach us ""emergency manual firing" which involved a slide rule, an inch and a half thick book of firing tables, various plotting boards, graphs and a sheaf of meteorology reports. Apparently they don't teach it anymore and I met a number of senior officers surprised to find I knew how to do it.
The whole thing would take minutes to calculate bearing, elevation, time of flight and most suitable charge for any given target. A specialised computer like Gunzen or FCA can do the whole thing in a second.
So in answer to your question, nope, no easy way to calculate it.
I don't need tha whole shebang, but as 4 factors are known generally. Weapon range, range to target, local gravity and local atm. pressure. For game purposes this should be enough.
I use the TNE rules along with FF&S. However the rules do not give any indication for flight time of artillery shell or mortar fire.
I use the TNE rules along with FF&S. However the rules do not give any indication for flight time of artillery shell or mortar fire.
if I may ask, by how much are all these factors relevant to the final impact point? for example, if earth's rotation is ignored, by how much will the shot vary from its predicted impact point?
automation makes us forget so much. you should put together a training video program demonstrating how to calculate impact points manually, put it on some disks and in some nice notebooks, and send it to every artillery command you know of. they'll file it away in some corner, but someday they might come running and pull it out.
mike wightman
SOC-14 10K
Border Reiver
SOC-14 1K
That is so cool. Never seen that before.
It's a very accurate summation of artillery science.
Rotation of the earth is important because of Coriolis effect. This can affect the fall of shot at longer ranges by around 50m. It can also affect flight times by up to half a second (not a lot but time of flight is very important for observing the fall of shot or taking cover). I remember being told that during the Battle of the Falklands (in WW1 not 1982) British Royal Navy gunners were missing by up to 200m because they corrected for Northern hemisphere coriolis instead of Southern.
Another apocryphal story about how important these factors can be is of a British Territorial Artillery unit (no names but they may be based in South Shields) inputed the previous day's MetMessage (meteorolgical data) into their FDC). The result was the destruction of the local garrison's primary school by a single 105mm shell. Thank goodness they were Weekend Warriors.
I'll have a look and see if I can come up with some simple range and flight times for some common calibers. If I fudge the atmospheric conditions I should still be able to produce accurate gravitational effects.
It's a very accurate summation of artillery science.
Rotation of the earth is important because of Coriolis effect. This can affect the fall of shot at longer ranges by around 50m. It can also affect flight times by up to half a second (not a lot but time of flight is very important for observing the fall of shot or taking cover). I remember being told that during the Battle of the Falklands (in WW1 not 1982) British Royal Navy gunners were missing by up to 200m because they corrected for Northern hemisphere coriolis instead of Southern.
Another apocryphal story about how important these factors can be is of a British Territorial Artillery unit (no names but they may be based in South Shields) inputed the previous day's MetMessage (meteorolgical data) into their FDC). The result was the destruction of the local garrison's primary school by a single 105mm shell. Thank goodness they were Weekend Warriors.
I'll have a look and see if I can come up with some simple range and flight times for some common calibers. If I fudge the atmospheric conditions I should still be able to produce accurate gravitational effects.
Border Reiver
SOC-14 1K
I have to admit it is beyond me.
I can use simple trig for calculating time of flight for a fixed muzzle velocity and range/barrel elevation but the gunner in me wins out each time. There are too many other factors.
One thing I do recall is that I could (especially with computer assistance) arrange the battery's fall of shot with a tolerance of 10 to 60 seconds over medium ranges by altering the charge size and elevation (high angle fire/low angle fire). Most modern weapons come with a choice of 8 charges. Generally an observer would be happiest with a time of flight of between 15 and 25 seconds (though I've never had a satisfactory explanation for this).
I think I'm going to give a friend at QinetiQ a call. It's time for the boffins to work this one out for me. I'll ask for the MT low velocity CPR guns to be calculated for its shortest and longest ranges at artillery standard temperature and pressure (15°c & 0.98 atm). Hell he's got a big ass number cruncher that'll easily manage 100+ TFLOPS if he can get the time on it.
I can use simple trig for calculating time of flight for a fixed muzzle velocity and range/barrel elevation but the gunner in me wins out each time. There are too many other factors.
One thing I do recall is that I could (especially with computer assistance) arrange the battery's fall of shot with a tolerance of 10 to 60 seconds over medium ranges by altering the charge size and elevation (high angle fire/low angle fire). Most modern weapons come with a choice of 8 charges. Generally an observer would be happiest with a time of flight of between 15 and 25 seconds (though I've never had a satisfactory explanation for this).
I think I'm going to give a friend at QinetiQ a call. It's time for the boffins to work this one out for me. I'll ask for the MT low velocity CPR guns to be calculated for its shortest and longest ranges at artillery standard temperature and pressure (15°c & 0.98 atm). Hell he's got a big ass number cruncher that'll easily manage 100+ TFLOPS if he can get the time on it.
bryan gibson
Absent Friend
if you have an idea of the base performance specs , there are somne sites that actually have artillary gunnery tables listed, varied by wepaon and tube diameter.
Border Reiver
SOC-14 1K
Spot on Bryan. 
I've found a couple of pointers here and have also found the existence of ballistic calculators online.
Put in the relevant details and out pop the answers. Yet to find a good solid link for one of these.
I've also been reminded on another board (arrse forums, don't ask
) of an old rule of thumb formula. This was for keeping shells from hitting supporting aircraft and was hardly used due to automation and use of metres instead of feet.
Zenith (in feet) = 4 x time of flight squared.
It's more of a rough rule of thumb but is quite useful. Also most modern guns (105mm/152mm/155mm) wihout base bleed or rocket assistance will not spend any longer than 90 secs in the air. Considering that a counter battery radar unit can pass your locus, fdc can calculate the data and guns can be laid in that time it is entirely possible (but unlikely) for you to be eliminated before your shell lands. So shoot and scoot.
I've found a couple of pointers here and have also found the existence of ballistic calculators online.
Put in the relevant details and out pop the answers. Yet to find a good solid link for one of these.
I've also been reminded on another board (arrse forums, don't ask
) of an old rule of thumb formula. This was for keeping shells from hitting supporting aircraft and was hardly used due to automation and use of metres instead of feet.Zenith (in feet) = 4 x time of flight squared.
It's more of a rough rule of thumb but is quite useful. Also most modern guns (105mm/152mm/155mm) wihout base bleed or rocket assistance will not spend any longer than 90 secs in the air. Considering that a counter battery radar unit can pass your locus, fdc can calculate the data and guns can be laid in that time it is entirely possible (but unlikely) for you to be eliminated before your shell lands. So shoot and scoot.
Border Reiver
SOC-14 1K
Aha.
I've found a site with some pretty good but basic calculators.
http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html?v0=800&a=45&t=&vx=800&x=0&vy=0&y=0
All you really need is muzzle velocity and range.
I've found a site with some pretty good but basic calculators.
http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html?v0=800&a=45&t=&vx=800&x=0&vy=0&y=0
All you really need is muzzle velocity and range.
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