Tutorial: Fighter Plane Design

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Basic fighter design

Fighter jets are among the hardest to build, and will all be slightly different. So, this tutorial will only cover basic design aspects, and all the things you should think about while designing/testing your fighter.

Top Speed

The best fighter jet should be able to outrun any opponent, so having multiple engines is a plus. Also, the Turbojet engines are more powerfull than jet engines, but don't work so well at lower altitudes, so the altitude it is designed for is a factor. Rocket engines also have much greater thrust, so will allow for higher top speeds but will have a large impact on many other factors of the jet. A good speed in the atmosphere would be 400 m/s, however the higher your jet operates the easier it is to reach a higher top speed.

Acceleration/Decelleration

Being able to speed up/slow down quickly is vital to your manouvering and reaching your top speed, so for an jet primarily designed to be agile it's vital. For bombers and such, it's less so. The best way to get good acceleration is to have a high trust-to-weight ratio, but breaking is a little more difficult. Landing gear and legs have a higher drag when deployed so can be used like airbrakes to slow your jet down, but they are slow to deploy, and often just look weird.

Manouverability

Maybe the most important aspect of the fighter, it should be able to outmanouver any rival jet. Having many control surfaces and having them cover all or most angles will allow for good manouverability but too many often cause issues such as warping the structure of the jet. RCS can be used too, and is vital for SSTO fighters. Having SAS modules or reaction wheels will provide extra tourque but not usually enough to have much of an effect (in the atmosphere). Balancing the plane right will also help to keep it stable.

Range

Basically how far the fighter can travel. A fighter that has a larger range can go further and fight for longer, and in real life wars often genuinely affects the outcome of a battle. A jet designed with normal intakes and engines will get better range lower in the atmosphere than a jet with ramjets and turbojet engines, which are designed to work better higher up and vice/versa. The amount of fuel carried will make a difference, a jet fuel tank contains less fuel than a rocket fuel tank. However this is where weight comes into play, as a lighter jet can fly with it's engines at a lower speed and get better efficiency. A fighter with a large amount of lift could also glide while traveling to save fuel. This tactic works best for a high altitude jet. Rocket engines provide great speed and power but will decrease fuel efficiency sharply due to their large fuel consumption and weight.

Weight

How heavy your jet is. A heavier jet will have severe reductions to manouvering and usually the same applies for it's range. To keep weight down you can use jet fuel tanks instead of rocket fuel, or structural fuselages if extra fuel is not needed. Removing extra features can also keep wieght down.

Adaptability

Esssentially what a jet can do, and what it can't. A pure bomber cannot usually beat a fighter, a high altitude stealth bomber is probably not built to land on water and an air superiority fighter will probably beat a jet designed to be an SSTO space fighter. Multiple engines and intakes designed for different purposes will help, allowing a jet to have fair performance in fights at any altitude. Also, consider what you want your jet to do. What's it trying to fight? If it's ground targets, maybe you should build a bomber to operate at low speed and altitude for accuracy. If it's trying to fight other planes it needs to be fast and manouverable. If it needs to go long distances add dropable fuel tanks, give it and efficient engines and such. And if it needs to go into space, it will need RCS and a specialised setup. VTOLS are horribly difficult to built but can often be superb fighters, if you intend to build one it is strongly reccomended you look at a specialised tutorial, as they are often very different to normal fighters.

Saftey

Which features you have to keep your jet airbourne and your kerbal alive. Armour can be used though is not usually very effective and will contribute to the wieght of the fighter. The cockpit/s can have their own release sytems and parachutes to eject in an emergency. Also, having the engines on an action key to turn them off can help in a flameout/stall situation, to prevent the jet going into a spin as so often happens during a flameout.

Weaponry

Kerbal space program was never designed as a war game, so there are no inbuilt weapons. However there are many modded weapons on the internet, so finding weaponry such as homing missiles or lazers should not be hard. As for creating your own, there are several things to remember (this is using weapons you create out of parts and not using mods):

1: The type of fighter affects the weapon. A pure fighter will want something accurate that flies straight. Your best choice is a light missile with it's own propulsion that is designed to reach top speed as fast as possible, and to have the jet stable and fast enough to get in close to the target. A bomber however can carry a much heavier bomb that could use SAS and a probe core to create a bomb that can fly iteslf, or at least fly in a straight line, or just lots of light bombs.

2: The plane should have a similar balance when carrying the weapon and once the weapon is fired. Looking at the centre of lift/balance while the weapon is not attached helps to keep this constant. If you do not do this there is a good chance the jet will become unflyable either from the start or once the weapon/s are fired.

3: Space weaponry will behave very differently to weapons built for the atmosphere, and will deviate towards the centre of mass, though if the centre of mass is lined up straight they will have perfect aim

4: Recoil is not an issue for the jet but the decouplers will have an effect on the missile, rocket or bomb when it is deployed, often sending them spiraling. Without a probe core and SAS this is hard to avoid, but having the weapons undock instead of decoupling often solves this (however, if your weapon has it's own propulsion it cannot be fired at the same time as undocking which has it's own set of problems and solutions)