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Newbie Joined: Mar 20, 2004 Posts: 2 Status: Offline

Just a question about bombing in ccip mode with a dumb bomb like oh a mk. 84 configured for high altitude drop. Does the ccip computation take into to affect the wind? Say through GPS via ground speed vs airspeed and direction? thx in advance.

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Yes, the system even makes a computer model of the wind changing in altitude. Via the INS (updated by GPS) it has info on the current wind at the flying altitude. Then it starts computing the coriolis force and the tendency of wind to decrease in altitude (Using all kind af tabels depending on latitude, airspeed,...) With all this it makes a rather realistic solution...Off course this is all based on assumptions and calculations, it's still a dumb bomb.

bye

Last edited by Stefaan on Mar 21, 2004 - 10:11 PM; edited 1 time in total

Hey Frodo,

I'm surprised to see the Coriolis effect being taken into account. I was under the impression that the coriolis force only had a noticable effect on large-scale phenomena such as weather systems. Shows how accurate those systems are I guess Smile

I was wondering if you have any idea on the influence of the corealis force on the trajectory of a Mk.84 ? (Just curious if you happen to have a ballpark figure, would take to much time to do the calculations Smile

stefaan

Newbie Joined: Mar 20, 2004 Posts: 2 Status: Offline

Thank you very much frodo, thats a great help.

F-16.net Editor Joined: Sep 23, 2003 Posts: 2833

Just to mention, which I am sure you all know. Early Blocks "in the old days" didn't have GPS assist for CCIP. Wink

I'm not so sure CCIP accounts for any Coriolis effects, but the effect is not limited to large weather systems. You can obverve it in your bathroom sink when it drains...

Ok, let me check on that one. I was under the impression that the system makes a realistic 'image' of the entire trajectory including the coriolis force. Just some standard values entered in the system. Wind changes in force and in direction, even when it is only 10-20 degrees it has to be taken in acount. I'm checking this and I will post my answer as soon as possible.

Bye

The system works like this: It knows the wind at flying altitude. It predicts the winds between current altitude and -4000ft (so below ground), It takes 0kts at -4000ft. So in between it calculates a gradual decrease in strenght and direction. The ground is a known value so it can predict the wind at target altitude. The stronger the wind at flying altitude the stronger the wind prediction on the ground. For the correction in direction a bunch of tabels are used because it depends on the latitude, initial velocity of the bomb (and I guess a lot of other factors are being used)...
I didn't had the time to check this info in the books but I used the knowledge of some guys here...Anyone is free to correct the details. (the details!! because the general idea is correct Mr. Green

)

Bye guys

Last edited by Stefaan on Mar 22, 2004 - 03:39 PM; edited 1 time in total

habu2,

The coriolis effect on bathroom drains was actually a pet peeve from my theoretical mechanics professor at the uni Smile

The coriolis force does have an effect on smaller systems, but it's negelectable compared to other factors. In a bathroom sink, major factors contributing to the rotation of the draining water are the physical construction of the drain, followed by convection forces in the water.

So water draining counter-clockwise in the northern hemisphere and clockwise in the southern is an urban myth, except in strictly controlled lab conditions.

http://www.physics.ohio-state.edu/~dvan ... ewcor.html (section 5.2)

Because of the distances/speeds involved, the effect could be noticable on a Mk.84 trajectory though.

stefaan

Stefaan,

It is not the bomb that is influenced by the coriolis force, it is the wind direction! If you have the change look at a wind map displaying the wind in altitude. You can see that the wind is not blowing from the same direction as the wind on the surface (most of the time it is 10-20 degrees but I've seen more). So since the bomb's trajectory is influenced by the wind...The System of the f-16 makes a wind prediction of the bomb on his way down.
I don't think the coriolis force is strong enough to influence a bomb but the wind is a big player.

Greetz

ps: you're correct on the bath experiment

Veteran Joined: Dec 09, 2003 Posts: 337 Status: Offline

"put the green thingy on the targe thingy, hit the red thingy to make the target thingy go boom."

THAT is how CCIP works

Cylon

F-16.net Editor Joined: Sep 23, 2003 Posts: 2833

Veteran Joined: Dec 09, 2003 Posts: 337 Status: Offline

Didn't mean to get technical..........

Cylon

Elite Joined: Dec 16, 2003 Posts: 798 Status: Offline

Heeee aaaahhhh!

Ya gotta love this Cylon dude. He has it right.

As we used to say, "Put the doofer on the ubahunk, and pickle"

On a less serious note, we were all surprised how many variables were incorporated in the F-16 fire control computer compared to the A-7D/E.

no flat earth assumption. Great circle all the time
rotation of earth under the bomb during its time-of-flight
coriolis (read bullet above)
crude assumption of changing winds between release altitude and tgt alt
GRAVITY delta if tgt was up on a high mountain

All this prolly got us a meter or two better accuracy than the A-7D.

The thing that made the F-16 so good was a better inertial for the short term. In other words, navigation error versus short term drift. The radar ranging was also a big player.

Now for the wind discussion:

bombs don't get blown by the wind. They fall thru the airmass, and if the airmass is moving, big deal. The jet is also flying in that airmass.
with no atmosphere, a bomb will fall directly below the jet until it hits the ground
changes in wind between release altitude and tgt alt is neat to talk about, but is not a significant player unless you're dropping a drogue-equipped B-61 (read nuke). Just think about it...... roll a 500 pounder off of a tall building during a hurricane. How many inches do you think that sucker will be blown by the wind?
air slows down the bomb due to friction/drag. Hence, the bomb will hit behind the jet in the airmass. This is called 'trail'. When the jet is 'tracking' toward the tgt in a crosswind, then the bomb will hit behind the jet AND 'downwind' with respect to the inertial/geodetic frame of reference. In the airmass, it will only intersect tgt alt directly behind the jet. Trail is a biggie for a very high altitude release, like 20000 feet. It is also a biggie for high-drag ord like the big munition dispensers, drogue nukes, etc. It isn't more than a few meters for a 5000 foot release of a 'slick' bomb.

later,

F-16.net Editor Joined: Sep 23, 2003 Posts: 2833

I always like the way you compare the A-7 to the F-16... of course from your flying experence... but also where the torch was passed from the most accurate single seat day bomber ( A-7 ) to a slightly better one ( the early F-16 ).

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