Background Information

The basic gist of the project is to optimize one aspect of Battle Damage Assessment (BDA).  The goal of BDA is to permit in-mission assessment of target kill, in order to reengage immediately or eliminate redundant missile strikes.  The older methods of damage assessment took long periods of time since it consisted of photo interpretation by an analysis specialist.  One benefit is a confirmed delivery with long-range identification from beyond the threat envelope. It also works for all weather conditions, day or night.  This is a huge advancement to photo interpretation.  BDA eliminates losing the lives of pilots that fly over dangerous territory to take photos of a target that was just attacked.  Bunker busters use BDA to give information on targets as far as 60 feet underground or through 20 feet of concrete.  The benefits for this technology are endless.

           Although BDA is a great idea, it is difficult to execute.  To deliver such valuable information to the people that need it is not an easy task.  Running a communication wire from the projectile to a transmitter that is a safe distance away from the impact blast is one way.  In a ground-to-ground situation, a stripper plate houses the transmitter.  This stripper plate will be discussed later.  In an air-to-ground situation, the transmitter is housed in the tail kit and pulled quickly away form the projectile by the means of a parachute.  For both of these situations the communication wire must be housed inside the tail kit.  The space in the tail kit is now a constraint.  The type of information collected is different for each mission and condition.  The projectiles are equipped with instruments that will give the vital information on the conditions the bomb is in before detonation.  An easy example to visualize this is if a target, lets say a Mr. Hussein, is congressing on the fourth floor of a seventeen story building, then an accelerometer would be placed in the projectile to show a graph of acceleration spikes for every ceiling the projectile crashed through before detonation.  If the graph shows fourteen spikes, then the projectile delivery is confirmed.  If the graph was to only show two spikes then the fighter plane could turn around and engage the target with another projectile.  The information that the target will be in a certain place at a certain time might not come around again for some time. 

            As one can assume this technology is not for all projectiles.   Torpedoes and some missiles use wires for control, which is not the same idea.  Projectiles that use BDA are the T.O.W. missile, the GBU-28, which was developed and used in the Persian Gulf War, and the BLU-118.  The most common use for this technology is a bunker buster.  These missiles are specifically design to plummet through the earth and destroy bunkers of supplies and enemies.  

The present mandrel design holds the wire for uncoiling in a cone shape.  The mandrel has grooves winding around it that spiral up to the top.  These grooves are there to hold the first winding of the current wire.  The mandrel can later be “unscrewed” from the spool when the release agent (silicone compound) is dry.  This cone shape is based on the fact that as the wire unspools, during free fall, it follows a path that is determined by the exit diameter at the end of the tail kit.   The slope of the current mandrel is determined by the exit diameter, and the dimensions allotted to the mandrel assembly.  For example, if the exit diameter for the wire were held constant, the slope would be the ratio of the length (L) of the mandrel to the base radius.  Of course if the exit were bigger it would increase the slope, which is preferable. 

The major flaw of this geometry is that as the wire unravels from the spool body, it rubs against the wire that it is wrapped around.  This unnecessary friction leads to undue stress on the wire, which may lead to transmission failure.

Currently, the wire is wound from bottom to top, and then brought back down to be wound from bottom to top again.  This is repeated as needed. This method produces an increase in acceleration (jerk) each time the wire is sent back to the bottom.  As the wire reaches the bottom, it will change acceleration again.  Having the wire wrapped in this fashion produces extra force that can cause failure of the wire.

These two problems were remedied by changing the geometry of the mandrel and the orientation of the wire.  The new design calls for a cylindrical mandrel, which has a slope of one.  The diameter is limited to the minimum bend radius of the wire chosen and the diameter of the wire exit in the tail kit.  As for the wire, it will be unwound in layers from top to bottom.  This reduces friction between the wire and the body significantly because the wire, in theory, will be going straight up; therefore the only resistance would be the silicone used to hold it in place.  

The release agent will be the same as the one being used now.  It exhibits no tribulation in hindering the un-spooling and is necessary to hold the spool’s form for both designs.

As for the wire being used, it is a fiber optic cable with a steel conduit to protect it.  The reason for its use is its speed of data transmission and its ability to transmit even if the fiber optic is physically broken, but the ends not too far away from each other.  This is because light can travel through a changing medium with minimum degradation as opposed to electricity, which would have to jump the gap with a  “spark.”  The down side to using a fiber optic setup is that the conduit has a larger bend radius compared to wires being tested.  Fiber optic cable is also expensive due the purpose needed.  The wire will be an off the shelf wire that is currently available.

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