Fire and Forget

By the end of my last post, we’d got as far as the 1950s in terms of the development of air warfare, an interesting period of transition, particularly for fighter technology. With the development of the jet engine and supersonic flight, the potential of these faster, lighter aircraft was beginning to outstrip that of the slow, lumbering bombers they ostensibly served. Lessons were quickly learned during the chaos of the Korean war, the first of the second half of the twentieth century, during which American & Allied forces fought a back-and-forth swinging conflict against the North Koreans and Chinese. Air power proved a key feature of the conflict; the new American jet fighters took apart the North Korean air force, consisting mainly of old propellor-driven aircraft, as they swept north past the 52nd parallel and toward the Chinese border, but when China joined in they brought with them a fleet of Soviet Mig-15 jet fighters, and suddenly the US and her allies were on the retreat. The American-lead UN campaign did embark on a bombing campaign using B-29 bombers, utterly annihilating vast swathes of North Korea and persuading the high command that carpet bombing was still a legitimate strategy, but it was the fast aerial fighter combat that really stole the show.

One of the key innovations that won the Allies the Battle of Britain during WWII proved during the Korean war to be particularly valuable during the realm of air warfare; radar. British radar technology during the war was designed to utilise massive-scale machinery to detect the approximate positions of incoming German raids, but post-war developments had refined it to use far smaller bits of equipment to identify objects more precisely and over a smaller range. This was then combined with the exponentially advancing electronics technology and the deadly, but so far difficult to use accurately, rocketeering technology developed during the two world wars to create a new weapon; the guided missile, based on the technology used on the German V2. The air-to-air missile (AAM) subsequently proved both more accurate & destructive than the machine guns previously used for air combat, whilst air-to-surface missiles (ASM’s) began to offer fighters the ability to take out ground targets in the same way as bombers, but with far superior speed and efficiency; with the development of the guided missile, fighters began to gain a capability in firepower to match their capability in airspeed and agility.

The earliest missiles were ‘beam riders’, using radar equipment attached to either an aircraft or (more typically) ground-based platform to aim at a target and then simply allowing a small bit of electronics, a rocket motor and some fins on the missile to follow the radar beam. These were somewhat tricky to use, especially as quite a lot of early radar sets had to be aimed manually rather than ‘locking on’ to a target, and the beam tended to fade when used over long range, so as technology improved post-Korea these beam riders were largely abandoned; but during the Korean war itself, these weapons proved deadly, accurate alternatives to machine guns capable of attacking from great range and many angles. Most importantly, the technology showed great potential for improvement; as more sensitive radiation-detecting equipment was developed, IR-seeking missiles (aka heat seekers) were developed, and once they were sensitive enough to detect something cooler than the exhaust gases from a jet engine (requiring all missiles to be fired from behind; tricky in a dogfight) these proved tricky customers to deal with. Later developments of the ‘beam riding’ system detected radiation being reflected from the target and tracked with their own inbuilt radar, which did away with the decreasing accuracy of an expanding beam in a system known as semi-active radar homing, and another modern guidance technique to target radar installations or communications hubs is to simply follow the trail of radiation they emit and explode upon hitting something. Most modern missiles however use fully active radar homing (ARH), whereby they carry their own radar system capable of sending out a beam to find a target, identify and lock onto its position ever-changing position, steering itself to follow the reflected radiation and doing the final, destructive deed entirely of its own accord. The greatest advantage to this is what is known as the ‘fire and forget’ capability, whereby one can fire the missile and start doing something else whilst safe in the knowledge that somebody will be exploding in the near future, with no input required from the aircraft.

As missile technology has advanced, so too have the techniques for fighting back against it; dropping reflective material behind an aircraft can confuse some basic radar systems, whilst dropping flares can distract heat seekers. As an ‘if all else fails’ procedure, heavy material can be dropped behind the aircraft for the missile to hit and blow up. However, only one aircraft has ever managed a totally failsafe method of avoiding missiles; the previously mentioned Lockheed SR-71A Blackbird, the fastest aircraft ever, had as its standard missile avoidance procedure to speed up and simply outrun the things. You may have noticed that I think this plane is insanely cool.

But now to drag us back to the correct time period. With the advancement of military technology and shrinking military budgets, it was realised that one highly capable jet fighter could do the work of many more basic design, and many forsaw the day when all fighter combat would concern beyond-visual-range (BVR) missile warfare. To this end, the interceptor began to evolve as a fighter concept; very fast aircraft (such as the ‘two engines and a seat’ design of the British Lightning) with a high ceiling, large missile inventories and powerful radars, they aimed to intercept (hence the name) long-range bombers travelling at high altitudes. To ensure the lower skies were not left empty, the fighter-bomber also began to develop as a design; this aimed to use the natural speed of fighter aircraft to make hit-and-run attacks on ground targets, whilst keeping a smaller arsenal of missiles to engage other fighters and any interceptors that decided to come after them. Korea had made the top brass decide that dogfights were rapidly becoming a thing of the past, and that future air combat would become a war of sneaky delivery of missiles as much as anything; but it hadn’t yet persuaded them that fighter-bombers could ever replace carpet bombing as an acceptable strategy or focus for air warfare. It would take some years for these two fallacies to be challenged, as I shall explore in next post’s, hopefully final, chapter.

The Alternative Oven

During the Second World War, the RAF pioneered the use of radar to detect the presence of the incoming Luftwaffe raids. One of the key pieces of equipment used in the construction of the radars was called a magnetron, which uses a magnetic field to propel high-speed electrons and generate the kind of high-powered radio waves needed for such a technology to be successful over long distances. After the war was over, the British government felt it could share such technology with its American allies, and so granted permission for Raytheon, a private American enterprise, to produce them. Whilst experimenting with such a radar set in 1945, a Raytheon engineer called Percy Spencer reached to the chocolate bar in his pocket; and discovered it had melted. He later realised that the electromagnetic radiation generated by the radar set had been the cause of this heating effect, and thought that such technology could be put to a different, non-military use- and so the microwave oven was born.

Since then, the microwave has become the epitome of western capitalism’s golden age; the near-ubiquitous kitchen gadget, usually in the traditional white plastic casing, designed to make certain specific aspects of a process already technically performed  by another appliance (the oven) that bit faster and more convenient. As such, it has garnered its fair share of hate over the years, shunned by serious foodies as a taste-ruining harbinger of doom to one’s gastric juices that wouldn’t be seen dead in any serious kitchen. The simplicity of the microwaving process (especially given that there is frequently no need for a pot or container) has also lead to the rise of microwavable meals, designed to take the concept of ultra-simple cooking to its extreme by creating an entire meal  from a few minutes in the microwave. However, as everyone who’s every attempted a bit of home cooking will know, such process does not naturally occur quite so easily and thus these ready meals generally require large quantities of what is technically known as ‘crap’ for them to function as meals. This low quality food has become distinctly associated with the microwave itself, further enhancing its image as a tool for the lazy and the kind of societal dregs that the media like to portray in scare statistics.

In fairness, this is hardly the device’s fault, and it is a pretty awesome one. Microwave ovens work thanks to the polarity of water molecules; they consist of one positively charged end (where the hydrogen part of H2O is) and a negatively charged end (where the electron-rich oxygen bit is). Also charged are electromagnetic waves, such as the microwaves after which the oven takes its name, and such waves (being as they are, y’know, waves) also oscillate (aka ‘wobble) back and forth. This charge wobbling back and forth causes the water molecules (technically it works with other polarised molecules too, but there are very few other liquids consisting of polarised molecules that one encounters in cookery; this is why microwaves can heat up stuff without water in, but don’t do it very well) to oscillate too. This oscillation means that they gain kinetic energy from the microwave radiation; it just so happens that the frequency of the microwave radiation is chosen so that it closely matches the resonant frequency of the oscillation of the water molecules, meaning this energy transfer is very efficient*; a microwave works out as a bit over 60% efficient (most of the energy being lost in the aforementioned magnetron used to generate the microwaves), which is exceptional compared to a kettle’s level of around 10%. The efficiency of an oven really depends on the meal and how it’s being used, but for small meals or for reheating cold (although not frozen, since ice molecules aren’t free to vibrate as much as liquid water) food the microwave is definitely the better choice. It helps even more that microwaves are really bad at penetrating the metal & glass walls of a microwave, meaning they tend to bounce off until they hit the food and that very little of the energy gets lost to the surroundings once it’s been emitted. However, if nothing is placed in the microwave then these waves are not ‘used up’ in heating food and tend to end up back in the microwave emitter, causing it to burn out and doing the device some serious damage.

*I have heard it said that this is in fact a myth, and that microwaves are in fact selected to be slightly off the resonant frequency range so that they don’t end up heating the food too violently. I can’t really cite my sources on this one nor explain why it makes sense.

This use of microwave radiation to heat food incurs some rather interesting side-effects; up first is the oft-cited myth that microwaves cook food ‘from the inside out’. This isn’t actually true, for although the inside of a piece of food may be slightly more insulated than the outside the microwaves should transfer energy to all of the food at a roughly equal rate; if anything the outside will get more heating since it is hit first by the microwaves. This effect is observed thanks to the chemical makeup of a lot of the food put in a microwave, which generally have the majority of their water content beneath the surface; this makes the surface relatively cool and crusty, with little water to heat it up, and the inside scaldingly hot. The use of high-power microwaves also means that just about everyone in the country has in their home a death ray capable of quite literally boiling someone’s brain if the rays were directed towards them (hence why dismantling a microwave is semi-illegal as I understand it), but it also means that everyone has ample opportunity to, so long as they don’t intend to use the microwave again afterwards  and have access to a fire extinguisher, do some seriously cool stuff with it. Note that this is both dangerous, rather stupid and liable to get you into some quite weird stuff, nothing is a more sure fire indicator of a scientific mind than an instinct to go ‘what happens when…’ and look at the powerful EM radiation emitter sitting in your kitchen. For the record, I did not say that this was a good idea…