How much fuel do I need for a fighter jet?

[X-Marshal]

I am trying to build semi-realistic fighter craft and I would like to know how much fuel I actually need (per engine). Mostly I use the Panther jet engine.

[Vanamonde]

Just depends on how far you want it to be able to fly.  

[Ryaja]

7 hours ago, X-Marshal said:

how much fuel I actually need

Yes

[Leganeski]

The Panther in wet mode has an Isp of 4000 s. The exact fuel consumption depends on how long you use the plane for, but I'll take a wild guess and say you might need an average TWR of 0.4 for an hour. In that case, your plane would to be about 30% fuel by mass.

That's a lot, but in practice, you wouldn't be using wet mode the whole time, which would raise the efficiency a lot, and a fighter jet might not need to be constantly executing maneuvers for an hour straight. If I made a fighter jet, I'd probably stick with dry mode the whole time (I_sp: 9000 s), and run it for like twenty minutes before landing back down. Then the plane would only need to be 5% fuel.

(Note that the number of engines doesn't matter other than letting you fly the plane at a higher TWR if you want.)

[X-Marshal]

14 hours ago, Leganeski said:

The Panther in wet mode has an Isp of 4000 s. The exact fuel consumption depends on how long you use the plane for, but I'll take a wild guess and say you might need an average TWR of 0.4 for an hour. In that case, your plane would to be about 30% fuel by mass.

That's a lot, but in practice, you wouldn't be using wet mode the whole time, which would raise the efficiency a lot, and a fighter jet might not need to be constantly executing maneuvers for an hour straight. If I made a fighter jet, I'd probably stick with dry mode the whole time (I_sp: 9000 s), and run it for like twenty minutes before landing back down. Then the plane would only need to be 5% fuel.

(Note that the number of engines doesn't matter other than letting you fly the plane at a higher TWR if you want.)

Ok, thanks

[jimmymcgoochie]

How long is a piece of string?

In the real world, fighter jets can range from something like the English Electric Lightning, which was little more than two jet engines with wings and a cockpit stuck to them with a minimal flight load to make it a rapid response fast interceptor, all the way to a heavy air superiority fighter like the F-15 Eagle which can carry three external drop tanks and (if my memory is correct) can fly around 5000 miles across the Atlantic without stopping, relying on sophisticated electronic systems and guided missiles rather than close-quarters agility.

How much fuel you need depends entirely on how far you want to fly and what kind of plane you’re building- a smaller, more agile plane will need less fuel to give it that agility but this will cost it flight range, whereas a plane built for greater endurance will suffer from the extra weight of fuel it has to carry around with it.

Cruising in “dry” mode will save you a lot of fuel when you don’t need the extra thrust of the afterburners.

[Coyote Foxtrot]

Design challenges like fighter jets can be a bit different to designing for a space mission as the design targets aren't given to you as you don't need to be concerned about getting it "there". When it comes to making these, it it better to set out design constraints/targets to aim for. Do you want an long-range air superiority fighter? You'll probably want to design it to be able to carry many fuel tanks but be able to drop them for improved maneuverability when dogfighting. Want an interceptor? You're probably more concerned with speed and range rather than maneuverability, so powerful engines and a lot of fuel is in need.