Abstract – In today’s world, rarely do soldiers ever see the ones that they are fighting. Hand-to-hand combat is a term of the past. Today, weaponry has become so advanced that it has almost become a game of point and click. In most wars of the past, bombs were just dropped from aircraft in large numbers, in a ‘spray and pray’ fashion, in hopes that one or more of the groups of explosives would destroy the intended target. Not only was this method costly, but it was also very prone to failure. Over the course of time, a new breed of bomb was produced. This newer and many times more volatile weapon had the ability to hit and destroy and object with laser-like precision. This surgical tool of war came to be known as a ‘smart bomb’. With the rise of weapons capable of pin-pointing anything on land, sea, and in the air, so arose an almost limitless number of possible applications for this tool of death.
Index Terms - control system, Second World War, smart bomb, ‘spray and pray’
The Weapon: How is it Different from Conventional Bombs? The standard ‘bombs’ of the past were quite primitive; they consisted of some explosive material packed packed into a case with a fuze mechanism of some sort. This fuze worked primarily in one of three ways. A time-delay system, an impact sensor, or a proximity sensor were all effective methods used to detonate the bomb. At the instant when the fuze is triggered, it ignites the explosive material, which results in an explosion, destroying the surroundings. Aircraft using this type of bomb are using what is refered to as a ‘dumb bomb’. This type of bomb is named so because it is merely dropped from an airplane and left to simply fall to the ground below. Hitting a target using this type of weapon wasn’t easy, which is why when ‘dumb bombs’ are used, they are dropped in very large clusters. In contract to ‘dumb bombs’, ‘smart bombs have a controlled flight path, either by a human, or by a computer within. The flight path is controlled so that it may hit its target with laster-like precision. A smart bomb is esentially a dumb bomb with a few major modifications. The added systems/parts include: an electronic sensor system, a built-in control system, a set of adjustable flight fins, and a battery. Upon being dropped from the airplane, the smart bomb ‘glides’, so to speak, through the air without any type of propulsion system of its own, other than the initial velocity which it recieved from the airplane carrying the bomb. During its decent, the adjustable flight fins stabalize its flight and along with the control system, give the bomb a way to steer itself as it glides through the air. Throughout the bomb’s decent, the control system tracks the designated target on the ground and the sensor system sends the control system information the relative position of the target. At this point, it is the control system’s turn to steer the bomb towards the target. The control fins on the smart bombs work the same way that the various flaps do on an airplane. By tilting the fins in a specific direction, there is an increase in drag on the side of the bomb that the fin(s) turn towards, which in turn causes the bomb to move in the direction of the side with increased drag. The continuous sensing and adjustment process continues until the bomb reaches the target, which is when the fuze mechanism ignites and sets off the explosive material. Generally, smart bombs have either proximity fuzes, which set off the explosive material just before the bomb hits the target, or impact fuzes, which detonate the explosive material upon impact of the bomb with the target[5].
The Dawn of Smart Weapons The term ‘smart’ when used in reference to weaponry wasn’t implimented until later on in the last century. The Grandfather of all smart weapons was the V2 Rocket, a German-made, unmanned, guided, ballastic missile. It was guided by a very complex gyroscopic system that sent signals to steering tabs on the fins and to vanes in the exhaust. These rockets were used towards the end of World War II to namely target London and Antwerp[4],[6].
Wernher Von Braun, creator of the V2, was recruited in 1932 by Walter Dornberger, to head the solid-fuel rocket and research and development in the Ordnance Department of the German Army. Later on, Braun became technical director of the rocket research station at Peenemunde. There, he began to develop the long-range ballistic missile, the A4, and Wasserfall, the supersonic anti-aircraft missile. It was during the Second World War that Braun began working on a new secret Weapon, the V2 Rocket. Braun was later arrested by the Gestapo when Heinrich Himmler, head of the Schutzstaffel(SS), because he feared that Braun was getting too interested in space travel, and was not completely trying to work on weapons to help Germany win the war. It was only after the Gestapo were convinced that Braun was willing to use all of his energies to develop the bomb that Himmler believed had the potential to win the war for Germany, was he released and allowed to go back to work[8].
The V2 was the first ever projectile of any sort whose trajectory could be changed. Prior to the V2’s invention, once a missile left it’s firing mount, there was no way to change the target destination or to keep the missile in line with its original target should anything such as strong winds throw it off course. This of course was a very frustrating problem for every country that used missiles (At this time in history, a missle was a rocket that was aimed directly at a target. After release, it was never certain that the missile would even come near the target). The power of missiles was almost mind-blowing, but the probability that the missile would land on target was not always certain, and could be very costly in terms of resources and the outcome of a war, should the missiles miss target[4]. The Engine The V2 had an A4 rocket motor, which was the first engine design to successfully move large volumes of fuel to the combustion chamber single gas-turbine driven fuel pumps. Contained in the small ellipsoidal tank(Figure 1), was 130 liters of hydrogen peroxide, which powered the gas-turbine. The hydrogen peroxide was expelled from the tank by compressed nitrogen from the bottles on the rack. Being one of the key components in the engine assembly, the thrust frame was able to transmit 23-tons of thrust to the rocket while being able to withstand the immense punishment and with the added benefit of being quite light. The V2 had an operational range of 234 miles, and the max burning time of the engine was 65-70 seconds. Fully fueled, the V2 had 4900kg of A-Stoff which, was a liquid oxygen with a temperature of minus 183 degrees Celsius and a mixture of 75% Ethyl alcohol and 25% water, called B-Stoff. The rocket also carried 175kg of T-Stoff, which was composed of 80% hydrogen, and 22kg of Z-Stoff, which was a mixture of 1/3 part sodium and 2/3 part water. The Z-Stoff was used for the propulsion of the mighty 580 horsepower turbine[7].
Up until recently, most smart bombs were either TV/IR-guided (Television/Infrared-guided) or laser-guided, both using visual sensors to locate their destination ground targets. Both of these types of systems can be very highly effective, given the right conditions within which to operate. The one major drawback of these systems is that the bomb sensor must always maintain visual contact with the target. Should cloud cover or other obstacles of any sort get in the way of the bomb’s line of sight to the target, the bomb will most likely veer off course.
The TV/IR-guided bomb has either a standard video camera or an infrared camera, used for night vision, mounted to the nose of the bomb. In the remote operation mode, the smart bomb acts like a remote-control plane. The onboard controller relays information using radio signals which are sent to a human operator. The human operator then relays commands to the control system to steer the bomb in the right direction. The benefit of this mode is that no specific target is needed to launch it, and the target doesn’t even need to be in sight at the time of launch. The operator just needs to know that the target is in the area and in what general direction, and then target it as the video camera picks up the image. In automatic mode, the smart bombs functions a bit differently. In automatic mode, the pilot must target something through the bomb’s video camera prior to launch. This sends a signal to the bomb to lock on to the target. The bomb’s control system in automatic mode steers the bomb so that the targeted image stays near the center of the video display. This is the way it ‘zeros in’ on the target. In this mode, many smart bombs can be launched at once on several targets without the remote operator worrying about controlling several bombs at the same time, which would be almost impossible. Laser-Guided Laster-guided smart bombs work quite a bit differently from the video camera smart bombs. This type of smart bomb uses a laster seeker, made up of an array of photo diodes, which are are semiconductors that generate a current or voltage when illuminated by light. These photo diodes, in particular, are sensitive to the frequency of laser light, and in order for the bomb to lock onto its target, a human operator, either on the ground or in the air, must use the laser to keep the smart bomb on track. The operator does this by ‘painting’ the target with a laser designator (the laser designator is like a laser pointer, it is the pointer that tells the smart bomb where to go). The designated target reflects the laser beam off of itself and the laser seeker picks it up. The system that the laser-guided smart bomb works on is somewhat similar to the TV/IR-guided smart bombs in automatic mode. The laser designated has its own unique pulse pattern. Before the bomb is dropped, the computer inside the aircraft provides information on the specific pulse pattern of the laser designator. Once the bomb is in the air, the control system is only interested in laser energy with this pulse pattern. The goal of the control system in the laser-guided system is to steer the bomb so that the reflected laser beam hits near the center of the laser seeker. By doing this, the bomb is kept heading on course very effectively[5].
When building a smart bomb, the intricacies that come into play are quite daunting. In the case of the V2 rocket, many different types of mixtures and fuels were needed to run the engine. The chemical knowledge needed to make the V2 a liquid propellant rocket is quite impressive. For the V2, problems arose with radio signals and how it could be possible to guide the rocket after it went over the horizon. Specific trajectories had to be calculated for the V2 when determining how much fuel to use. Most of the time, targets weren’t very far away from the launch sites, and propelling the rocket to its maximal altitude wasn’t always needed, thus less fuel was needed sometimes; this again, needed to be calculated in some way. The triggering mechanisms that determine when the explosive material within the bomb should go off takes quite a bit of precision. The electronic devices used to detonate the explosive material can be programmed for a specific time that would allow the bomb to penetrate multiple layers of a bunker before detonation[3]. And when all is finished with all of the inner workings of the bomb, there is the added pleasure of dealing with what shape the rocket should be to make it most efficient in flight.
In one incident, three soldiers lost their lives because in the heat of battle, a smart weapon missed it mark, the results were devistating. On today’s battlefield, even with the advances in weapon systems, which are designed to eliminate foes with pin-point accuracy and to minimize civilian and friendly casualties, it’s still possible to have casualties caused by friendly fire. The three killed were special forces soldiers, erased from this earth in a tragic friendly fire incident. The US, in Afghanistan, said that they were taking extraordinary measures to avoid civilian casualties in the campaign, but still, many American journalists have reported many civilian deaths and injuries from bomb attacks. The Pentagon is apparently working on systems to avoid friendly fire casualties by improving ‘situational awareness and target identification’. One of these systems plans to use small global positioning and millimeter-wave devices that would help troops on the ground and in the air identify each other as friendlies. Unfortunately, this system can’t distinguish civilians or other neutrals from the enemy. Problems such as this are very alarming to the public, considering the proclaimed ‘precision’ of these ‘smart’ munitions. It is quite disconcerting knowing that weapons of extreme precision are making such mistakes. The public is quite critical of things and when what is proclaimed isn’t the case 100% of the time, the public usually is not in favor. Should a conflict occur on our homeland, problems such as the ones in Afghanistan would become great causes for concern. One of the reasons why smart bombs were developed was because of the civilian and other neutral casualties that occured as a result of massive bombings; a reoccurance of these casualties is never a way to win the war with people’s confidence.
‘Smart’ munitions, weapons guided by lasers and satellites, are playing a lead role on today’s front lines in war. These guided missiles are far more effective than the standard bombs of the past. In the second World War, 108 aircraft, on average, dropping 648 bombs were needed in order to destory a single target. Many times, as a result of dropping this number of bombs in a ‘spray and pray’ fasion, civilians inevitably were caught in the barrage. One of the benefits of having more accurate weapons is that civilian casualties are kept at a minimum because of the precision of smart bombs. In 2001, 38 airfract were able to hit 159 targets on the first night of bombing during the campaign in Afghanistan. Smart bombs are the new wave of the future, what new advances in technology lie ahead, one can only dream about[1].
I’d like to thank all those in my life who inspired me to pursue math and the sciences, which lead me to choosing computer engineering as my major. Specifically, I’d like to thank my father for not telling me to stop playing games on the computer, which ultimately lead to my love for computers and programming. Also, without my dad, I wouldn’t have had a constant flow of computer, robotic, and programming magazines coming into the house to keep my hunger for information in computers always satisfied. To my teachers, Ignatius Brodzinski and Michael Castleman, thank you for piling all of that Calculus and programming work on me. If I hadn’t been pushed to constantly deal with an increasing workload, college might have been almost unbearable. I’d also like to thank Dr. Budny for constantly pushing me to ‘get to the line’. I never imagined that I could learn so much in such a short amount of time.