Educate me, coriolis effect, longest sniper shot, flying

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fudge80

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fudge80
I work in the gun industry part time so when the longest sniper shot in recorded history happens usually there is some banter and questions. Yesterday a Canadian sniper was credited at making a kill shot at over 2 miles. A lot goes into making a shot that long, over 600ft of bullet drop over that distance, etc.

All the articles state coriolis effect comes into play at shooting distances of over a 1000 yards. I have always wondered why? I never thought it was actually a factor more of a myth. None of my co-workers really knew so we started googling, all the articles state that since the bullet is not connected to the earth that the earth is rotating underneath it.

So my question is why doesn't the same principal apply to airplanes? Since the earth is rotating west to east why can't I take my little Cessna up and do a few 360's and land several hundred miles west of where I started? ( or an Olympic long jumper having extra distance when jumping towards the west vs. jumping towards the east, or any other of a million examples)

Any thoughts and discussion on this are greatly appreciated.
 
As a former Artillery guy, it's definitely very real at those distances. It matters for an artillery round which has a MUCH bigger allowance for being inches off. I can't imagine how he did that with a .50 cal....
 
fudge80 said:
So my question is why doesn't the same principal apply to airplanes? Since the earth is rotating west to east why can't I take my little Cessna up and do a few 360's and land several hundred miles west of where I started?
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It does apply to airplanes. If a plane were making perfect 360's over an airport in a no-wind situation without any geographical or navigational reference, after 20 mins or so, you'd no longer be over the airport.

It's also why when flying from London to New York that you leave at 3pm and your arrive at 3pm.
 
How are you navigating?

Direction will be most influenced by travel in a north/south direction. If you get up in the air, and head to a distant airport heading north or south, or some component thereof, and you dead-reckon locking your autopilot in to heading mode, ignoring winds and navigational inaccuracies, you will be offset from the airport by some determinable distance. If you navigate by GPS, VOR or have a visual, you will be automatically correcting from the effects of Coriolis the same as you will be automatically correcting for the winds.

Inertial navigation systems (INS) are a special case, and it is my understanding that they can be inherently self-correcting subject to where they are initialized, e.g. on the ground.
 
jbarrass said:
As a former Artillery guy, it's definitely very real at those distances. It matters for an artillery round which has a MUCH bigger allowance for being inches off. I can't imagine how he did that with a .50 cal....
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Reformed Redleg as well. Drift was even more critical for high angle where the time of flight was even greater up to one minute, allowing earth to rotate the target away. Coriolis has effect due to projectiles spin as well.

I'll spare you a discussion about tube jump and tube droop. :D
 
OK, so I have an airport exactly 100 miles West of me and one that is 100 miles East of me, all other variables the same except Coriolis does it take less time to get to the one West of me?
 
The Coriolis effect is due to the earth's speed with respect to space just above it standing still is higher at the equator than it is north. Get to the north pole point and is rotational speed is zero. Its a sinusoil. Anyway if you fire an artillery round to the north from the equator, it tends to move with its equator speed. So it moves in the direction of spin of the earth, to the east. Keep in mind the air directly above the earth tends to move with the earth.

Same if you shoot a pea shooter towards the center of a record in a record turntable. It moves along with the speed it had from the edge of the record, which moves it along.

Both are examples of coriolis effect.
 
coloradobluesky said:
The Coriolis effect is due to the earth's speed with respect to space just above it standing still is higher at the equator than it is north. Get to the north pole point and is rotational speed is zero. Its a sinusoil. Anyway if you fire an artillery round to the north from the equator, it tends to move with its equator speed. So it moves in the direction of spin of the earth, to the east. Keep in mind the air directly above the earth tends to move with the earth.

Same if you shoot a pea shooter towards the center of a record in a record turntable. It moves along with the speed it had from the edge of the record, which moves it along.

Both are examples of coriolis effect.
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Or, stated another way, it stops moving laterally at equatorial speed once it's fired, while the earth under it continues to rotate, barring relative wind effects.
 
Sac Arrow said:
Or, stated another way, it stops moving laterally at equatorial speed once it's fired, while the earth under it continues to rotate, barring relative wind effects.
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I think you have that backwards. It is moving at equatorial speed while the ground slows as it moves north or south.
 
fudge80 said:
I work in the gun industry part time so when the longest sniper shot in recorded history happens usually there is some banter and questions. Yesterday a Canadian sniper was credited at making a kill shot at over 2 miles. A lot goes into making a shot that long, over 600ft of bullet drop over that distance, etc.

All the articles state coriolis effect comes into play at shooting distances of over a 1000 yards. I have always wondered why? I never thought it was actually a factor more of a myth. None of my co-workers really knew so we started googling, all the articles state that since the bullet is not connected to the earth that the earth is rotating underneath it.

So my question is why doesn't the same principal apply to airplanes? Since the earth is rotating west to east why can't I take my little Cessna up and do a few 360's and land several hundred miles west of where I started? ( or an Olympic long jumper having extra distance when jumping towards the west vs. jumping towards the east, or any other of a million examples)

Any thoughts and discussion on this are greatly appreciated.
Click to expand...

The articles that talk about the ground moving beneath it are not accurate. Think of it like the turntable mentioned above. It is only a factor in north and south trajectories because the circumference of the rotation changes over the length of bullet travel.
 
Cooter said:
I think you have that backwards. It is moving at equatorial speed while the ground slows as it moves north or south.
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This is correct. It carries it's equatorial speed north.

Keep in mind the air is moving slower as it goes north becaue the air moves about the same speed as the earths rotation for this calculation.

Its a frame of reference problem.
 
fudge80 said:
So my question is why doesn't the same principal apply to airplanes? Since the earth is rotating west to east why can't I take my little Cessna up and do a few 360's and land several hundred miles west of where I started? ( or an Olympic long jumper having extra distance when jumping towards the west vs. jumping towards the east, or any other of a million examples)
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The wind will negate the Coriolis effect
 
dmspilot said:
Why engage in the discussion when you can post useless snark?
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I agree about the snark, but he's probably referring to the fact that Coriolis isn't a factor when circling over a constant Latitude. It only is a factor when traveling Longitudinally.
 
Sac Arrow said:
Yes.
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Earth's rotation doesn't have any direct effect on flight times in either direction. The primary reason for westbound flights to be longer than eastbound, is mostly due to the jet stream, not necessarily the Coriolis Effect.
 
Clark1961 said:
It's not useless if one stops and thinks about Newton's contributions.
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I thought his discovery of the self-picking apple tree was brilliant. No illegal aliens on ladders. Just harvest the fruit while sitting in the orchard reading a book (these days wearing an OSHA approved hardhat on the jobsite of course).
 
fudge80 said:
I work in the gun industry part time so when the longest sniper shot in recorded history happens usually there is some banter and questions.
Click to expand...

Where do you work in the firearms industry? My best friend works for one of the big manufacturers and it's shocking how little some of his co-workers know about the product they peddle.

Marketing people flipping pictures of a right handed gun around to look like left handed gun because it looks better in the ad that way... Only problem is they only make that action in right hand...
 
The earth's spin has an effect on launching into space. Always launch with the rotation of the earth. The rocket carries the speed of the earths rotation with it and doesnt have to accelerate as much to reach escape velocity.
 
There was a video on YouTube demonstrating this effect. The guy set up two targets, one 1000 yards east, and one 1000 yards west. If I can recall correctly, when shooting East his rounds hit above the Point-Of-Aim. When shooting West the hits were below the Point-Of-Aim. The effect was explained as the East target would be moving downward as the earth rotated away from the shooter.

Then again I could be way off target.
 
coloradobluesky said:
The earth's spin has an effect on launching into space. Always launch with the rotation of the earth. The rocket carries the speed of the earths rotation with it and doesnt have to accelerate as much to reach escape velocity.
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Learned that in Kerbal Space Program!
 
Sac Arrow said:
Then explain how I am wrong. I am listening.
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The effect occurs not because the bullet loses its momentum but because it preserves it. So assume the bullet is traveling 1,000 mph with the equator before it is fired and also assume it is fired True North. As it travels North, it continues to travel 1,000 mph latitudinally but the lines of longitude are closer together than they were at the equator and it will therefore begin to traverse lines of longitude. At 45°N the earth is spinning 700MPH so it would appear that the bullet is deflected East at an angular velocity of 300mph as it travels over that latitude. There is no coriolis effect for objects traveling East -West.
 
Clark1961 said:
It's not useless if one stops and thinks about Newton's contributions.
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I guess I'm not as smart as Newton. Sad.

You realize I was talking about the airplane, and not the bullet, right? Last time I flew cross-country, I did not have to calculate Coriolis effect in order to determine my heading and ETA to my destination accurately.
 
You are on target

midwestpa24 said:
There was a video on YouTube demonstrating this effect. The guy set up two targets, one 1000 yards east, and one 1000 yards west. If I can recall correctly, when shooting East his rounds hit above the Point-Of-Aim. When shooting West the hits were below the Point-Of-Aim. The effect was explained as the East target would be moving downward as the earth rotated away from the shooter.

Then again I could be way off target.
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I still bear the mental scars of corriolis effect.

We were shooting mines out the torpedo tube, they were converted torpedoes that could "swim" into the harbour the idea being we could mine a harbor covertly from way outside. The mines travelled a long way, about half an hour.

At some point I was "invited" to come from the torpedo room where I was supervising loading mines to report to the Captain why I was shooting the mines in the wrong heading.

Seems the current was setting the mines to the left of the true heading to the harbor, so in his mind I should have been aiming to the right of true heading. Yet, "I" (my fire control system) was sending those mines out to the left! I was asked to explain why the discrepancy and in general how the Navy could be so misguided to assign me as his Weapons Officer.

Um, Corriolis Effect? I ventured.

Much more verbal harrassment ensued, the result being that I was finally released to go back loading mines, minus any shred of dignity.

As it happened the FCS was correcting for corriolis effect, which had a larger effect then the set and drift in the opposite direction. I showed this to him later by showing the shoot bearing north of the equator(corrects to the left), at the equator (no correction) and south of the equator (corrects to the right).

Any apology? No way, he said I should have been more sure of the answer.
 
GRG55 said:
I thought his discovery of the self-picking apple tree was brilliant. No illegal aliens on ladders. Just harvest the fruit while sitting in the orchard reading a book (these days wearing an OSHA approved hardhat on the jobsite of course).
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I thought it was a fig tree.
 
Cooter said:
The effect occurs not because the bullet loses its momentum but because it preserves it. So assume the bullet is traveling 1,000 mph with the equator before it is fired and also assume it is fired True North. As it travels North, it continues to travel 1,000 mph latitudinally but the lines of longitude are closer together than they were at the equator and it will therefore begin to traverse lines of longitude. At 45°N the earth is spinning 700MPH so it would appear that the bullet is deflected East at an angular velocity of 300mph as it travels over that latitude. There is no coriolis effect for objects traveling East -West.
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You are correct that momentum is preserved, but It isn't exactly true that there is no coriolis effect for objects traveling east west. The speed is not affected, at least directly, but a bullet will travel further when fired to the west, since the trajectory is rising with respect to the horizon, and falling in the other direction due to the earth's rotation, resulting in more drop.

Let's say that we are at the equator, and we fire a bullet to the east, travelling at 1,000 mph, horizontal to the horizon. With respect to the surface of the earth, the bullet is travelling at 1,000 mph. Relative to the earth as a mass, it's stationary. You've canceled the absolute horizontal velocity component out. It would be like dropping a bullet on the top of a spinning globe. On the other hand, if the bullet is fired to the west, you have doubled the speed with respect to the earth as a mass, and the bullet then rises above the surface of the earth as it departs tangentially. Whether artillery ballistic computers take that effect in to account I do not know.

Let's now take the case of an airplane. In theory, a flight to the west would involve a slight decent component in level flight with respect to the surface of the earth, and an ascent component flying to the east. Given the same power setting, speed to the west would be faster for that reason. Measurable? Probably not.
 
Drift factors in Artillery Tabular Firing Tables (TFT) aren't directionally related. It is solely only a function of range. In my (now antiquated) Fire Direction days, while I know Coriolis Effect was discussed and having an effect, but it wasn't something which had a stand alone correction factor in manual gunnery...which I did daily for three years on a daily basis. If it was included in the old Tactical Fire Control (TACFIRE) System or Battery Computer System (BCS) in the 80-90s, it was embedded and never something we had access nor need to address.

A large function of artillery drift is due to the spinning of the projectile as much as due to Coriolis Effect.
 
Bullets dont go far enough to be affected by the earths spin, shooting east to west. The effect going north to south is very small also. The difference is 1/10th of the effect of shooter wiggle, environmental (wind and pressure and altitude), and mechanical differences +- . The programs that calculate bullet drop can include coriolis but if done right the difference is less than the smallest adjustment the scope has (which is usually 1/4 moa).

Artillery shooting 10 or 20 miles IS affected by such things, but effect is still small. Nothing beats a forward observer. Wind effect in 20 miles is way bigger than anything. And the wind changes from shot to shot.
 
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Sac Arrow said:
You are correct that momentum is preserved, but It isn't exactly true that there is no coriolis effect for objects traveling east west. The speed is not affected, at least directly, but a bullet will travel further when fired to the west, since the trajectory is rising with respect to the horizon, and falling in the other direction due to the earth's rotation, resulting in more drop.

Let's say that we are at the equator, and we fire a bullet to the east, travelling at 1,000 mph, horizontal to the horizon. With respect to the surface of the earth, the bullet is travelling at 1,000 mph. Relative to the earth as a mass, it's stationary. You've canceled the absolute horizontal velocity component out. It would be like dropping a bullet on the top of a spinning globe. On the other hand, if the bullet is fired to the west, you have doubled the speed with respect to the earth as a mass, and the bullet then rises above the surface of the earth as it departs tangentially. Whether artillery ballistic computers take that effect in to account I do not know.

Let's now take the case of an airplane. In theory, a flight to the west would involve a slight decent component in level flight with respect to the surface of the earth, and an ascent component flying to the east. Given the same power setting, speed to the west would be faster for that reason. Measurable? Probably not.
Click to expand...

If the object fired doesn't move closer to or further from the axis of rotation, then there is no coriolis effect.

Edit: See @Clark1961's post below. That sounds like what you are describing.
 
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