Ballistics and how less power is more energy delivery.

[Tackle]

Officer work, thanks.

With the understanding that it doesn't really matter, I wonder how much rotational energy we have to donate before it has to come from the linear.

Moment of inertia of a sphere, I, is 2/5 mR2

Rotation energy is 1/2Iw2, where I is as above, and w is the angular velocity (how fast it's spinning, radians per second if we're doing SI rather than fathoms-per-demihectare).

I make that 1/5 mR2w2

We know m (e.g. 0.004kg), R (e.g. 0.002975m), now we just need to paint a BB with a battenburg patten and film it with a high-speed camera to find out w.

Granted we're down at 0.0000000070805 w2 for a 0.4g BB, so we're not talking big numbers.

View attachment 81004

 

[Adolf Hamster]

Officer work, thanks.

With the understanding that it doesn't really matter, I wonder how much rotational energy we have to donate before it has to come from the linear.

Moment of inertia of a sphere, I, is 2/5 mR2

Rotation energy is 1/2Iw2, where I is as above, and w is the angular velocity (how fast it's spinning, radians per second if we're doing SI rather than fathoms-per-demihectare).

I make that 1/5 mR2w2

We know m (e.g. 0.004kg), R (e.g. 0.002975m), now we just need to paint a BB with a battenburg patten and film it with a high-speed camera to find out w.

Granted we're down at 0.0000000070805 w2 for a 0.4g BB, so we're not talking big numbers.

yes the angular velocity is a bit of an unknown.

in the spreadsheet i made a while back i ended up having to go with a macro and goal seek to just brute force it, hence the whole "20cm of rise" caveat as there needed to be a fixed goal to look for. although tbh a few corners were cut, eg the magnus force was simplified to the force for a cylinder of equivalent cross section rather than doing it properly and splitting it up into increments, or the very oversimplified drag model that treated air as an incompressible fluid. but then i was doing it because i was bored/curious so an approximation was good enough

for the aforementioned 1j of muzzle energy and 20cm of rise criteria it would come out as:

63.67 rad/s for 0.2g

79.54 rad/s for 0.25g

97.03 rad/s for 0.3g

133.46 rad/s for 0.4g

173.293 rad/s for 0.5g

it's part of the reason why as mentioned, heavier=better doesn't always hold true practically, when the losses in the hop to acheive sufficient spin drop the energy enough to the point where a lighter bb from the same gun would go further.

fun anecdote- it's possible to have 2 "sweet spots" for hop, first when you've just enough pressure to get the spin, then turning the hop on further results in the expected overhop, but go too far and the energy will drop to the point where it'll meet a second spot, with a much higher spin but lower energy.

although more usually by the time you get to that point the gun just jams.

View attachment 81004

 

[EDcase]

The answer is out there...

....waaaaaay out there ?

 

[Rogerborg]

133.46 rad/s for 0.4g

I make that 0.0001261148327138J of rotational kinetic energy, or a lot less than that required to hold it up, so it's got to be leeching that (small) amount from the linear.  Insignificant compared to the drag, I was just curious, unlike some peasants in here.   

 

[EDcase]

I'm not a peasant

I'm a serf ?

Wow, this thread has definitively come off the rails and into a ravine.

 

[Adolf Hamster]

I make that 0.0001261148327138J of rotational kinetic energy, or a lot less than that required to hold it up, so it's got to be leeching that (small) amount from the linear.  Insignificant compared to the drag.

yeah, can be fun to delve into this sort of thing, tbh i'm surprised it's that small myself figured it'd be a more major component.

 

[Tackle]

? this thread has definitively come off the rails and into a ravine.

About time I reckon ?, its got boring as f#ck?

 

[Lozart]

Magnus effect or not, all bullets have spin even airgun pellets. So by that measure, you can negate that as a factor as it is common 

Except you can't, because the Magnus effect in the case of airsoft BB's provides lift. It also produces increased turbulence in the BB's wake which contributes to drag which affects the terminal energy.

Axial spin in rifled barrels increases range by the conservation of angular momentum which is a whole different kettle of ballistic fish.

 

[Adolf Hamster]

About time I reckon ?, its got boring as f#ck?

What do you mean? From my perspective it just got interesting?

 

[Rogerborg]

What do you mean? From my perspective it just got interesting?

Really?  Nobody's been offered out IRL yet.  

 

[Shamal]

View attachment 81004

Haha ?

I  point de small end towards baddies,pull on da sticky down fing and see white balls come out da small end. Job done,I happy.?

Regards 

 

[AirSniper]

Russians go do something stupid

Excellent example of a high velocity impact by a tiny projectile in a vacuum travelling at speeds I understand are 20 times the speed of a bullet...  Fast Forward to 9:15.

 

 

[Guest]

“Never argue with a fool, onlookers may not be able to tell the difference.”





“Never argue with an idiot. They will drag you down to their level and beat you with experience.”



― Mark Twain

 

[Tommikka]

11 hours ago, AirSniper said:

Russians go do something stupid

Correction - Russia do a thing knowing the risk & not caring

 

[AirSniper]

Point again that Ballistics works in space... Shows that even in LEO that the pull of gravity can affect an object unless it is travleing with enough energy to carry it in to space.

Again, some of these "Projectiles" are the size and weight of flecks of paint.

In space a fleck of paint travelling at the speeds of a bullet in space carries enough momentum that if it hits something, can crack that thing, chip it or in some cases, pass straight through the hull of the ISS. 

Again, I draw attention to the fact that ballistics works any where and the denial by some that the same calculations for airsoft are the very same calculations used in daily science for calculating KE, even in air gun and live round shooting, archery and so on. 

It seems to be a lost fact on people.

 

[Guest]

Point again that Ballistics works in space... Shows that even in LEO that the pull of gravity can affect an object unless it is travleing with enough energy to carry it in to space.

Again, some of these "Projectiles" are the size and weight of flecks of paint.

In space a fleck of paint travelling at the speeds of a bullet in space carries enough momentum that if it hits something, can crack that thing, chip it or in some cases, pass straight through the hull of the ISS. 

Again, I draw attention to the fact that ballistics works any where and the denial by some that the same calculations for airsoft are the very same calculations used in daily science for calculating KE, even in air gun and live round shooting, archery and so on. 

It seems to be a lost fact on people.

NO.

Those flecks of paint are not travelling at the speed of bullets, a fact that seems to be lost on you.

Low orbit satellites (inc ISS) travel at 17000 mph, geosynchronous satellite at 7000mph.

The “pull of gravity” as you put it (side note, gravity is not a force, it doesn’t pull anything, see A.Einstein et al) always affects anything, whatever speed it’s travelling at, there is no “unless”?.

You're not doing yourself or your point any favours getting basic science wrong, no wonder nobody is listening to you pontificate about ballistics ??‍

 

[Adolf Hamster]

it's also worth questioning how come we don't include the gravitational pull of the moon, sun, other planets, etc, or how earths own gravitational acceleration isn't strictly constant into earthbound ballistic calculations.

 

[Rogerborg]

it's also worth questioning how come we don't include the gravitational pull of the moon, sun, other planets, etc, or how earths own gravitational acceleration isn't strictly constant into earthbound ballistic calculations.

You clearly haven't watched the Mark Wahlberg documentary "Shooter" where he takes all those into account, and also temperature, humidity, air pressure, and the Coriolis effect, does the sums in his brain, and then goes "Click-click BOOM".  100% FACT.

 

[Adolf Hamster]

You clearly haven't watched the Mark Wahlberg documentary "Shooter" where he takes all those into account, and also temperature, humidity, air pressure, and the Coriolis effect, does the sums in his brain, and then goes "Click-click BOOM".  100% FACT.

no but i can shoot imram zakhaev before the wind dies down in cod4, basically the same thing.

although evidently i'm not that good because i keep hitting his arm even though i'd swear the bullet hit his head

 

[AirSniper]

NO.

Those flecks of paint are not travelling at the speed of bullets, a fact that seems to be lost on you.

Low orbit satellites (inc ISS) travel at 17000 mph, geosynchronous satellite at 7000mph.

The “pull of gravity” as you put it (side note, gravity is not a force, it doesn’t pull anything, see A.Einstein et al) always affects anything, whatever speed it’s travelling at, there is no “unless”?.

You're not doing yourself or your point any favours getting basic science wrong, no wonder nobody is listening to you pontificate about ballistics ??‍

Gravity, there is big debate on what it actually is even now in the scientific world.

Something as big as the moon does effect the earth, the earth has a barrycenter much like the sun has from the gravitational effects of Jupiter. 

On the earth this translates to the tides that we see.

Again my point that ballistics works no matter where you try it.

In space, there is no resistance to an object that has energy imparted on it.  So something travelling at 5 km/s is going to do a lot of damage or pass right through something.

I am not getting my science wrong, there is nothing wrong with it, the issue is that people are picking fault where non exists and over complicating things based on what alternate examples I can provide so that finally the penny drops.

As for the science, people's eyes generally glaze over, not my problem if people can't see the relationship.

Tell me, how many feet per second would a projectile be travelling on exit of the muzzle if you only input 1 Joule of energy and your mass was 0.00002g ? would be the same as a fleck of paint and travel at nearly 22,000mph like here https://www.dailymail.co.uk/sciencetech/article-3587882/What-happens-tiny-fleck-paint-hits-space-station-Tim-Peake-reveals-crack-ISS-window-debris-collides-craft.html which was suggested to me when I searched fleck of paint mass to try and ball park some figures for this. 

And Einstein, as brilliant he was, some of his theories are now being challenged at the time and now as our understanding of the universe expands.

As for my ballistics input, I am using the very same equations that are used in airsoft as in airgun as in live round as in launching a big eff off rocket in to space... If you think that rockets has nothing to do with ballistics, that s the same as denying that rocket grenade launchers AKA RPG's  don't exist.

Try adding something useful like a source of information for me to consider rather than an opinion. 

https://www.calculatorsoup.com/calculators/physics/kinetic.php?given_data=velocity&KE=1&KE_units=joule&m=0.00002&m_units=gram&v_units=foot+per+second&sf=0&given_data_last=velocity&action=solve

1 Joule of energy

tiny mass... How many fps?