Why Fighter Jets Don't Use Scramjets

Fighter jets don’t use scramjets because they’re only effective at high speeds, and jets need a different engine for takeoff and landing. Long-range missiles, however, combine a rocket for launch and a ramjet for cruise.
_________________________________________________
_________________________________________________
Our channel is about Aviation.
We make the best educational aviation videos you've ever seen; my videos are designed to clear misunderstandings about airplanes and explain complicated aviation topics in a simple way.

[abasthegodemperor]

Another reason they can't use ramjets is that during high AoA manuevers, the engine couldn't get enough air to keep a consistent amount of thrust. Keep in mind even turbojets sometimes struggle to breathe during high AoA maneuvering, so just imagine how bad a ramjet would have it.

[earth]

the sr71 is one of the few examples of a combined turbojet and ramjet engine system, however it flew like a brick with an engine strapped onto it. Another issue with having high speed fighter jets is that g forces exist, having a high speed aircraft would make any sort of maneuver dangerous.

[godzillatoons]

In case you guys are wondering:
The catapults on aircraft carriers are able to launch aircraft, with the necessary lift, with around 500 sq ft of pressurized steam propelling the catapult.

If we were to use ramjets or scramjets, we'd need to have bigger aircraft carriers with longer runways in order to use rocket propelled catapults, and ground runways would also need rocket propelled catapults. And those are just budget options.

[RedThest]

it's obvious why scramjets aren't used
because jets would keep falling into pools

[michaelc.]

As other people have said, ram/scramjets are both pretty highly dependent on the intake airflow and doing any significant amount of angle of attack or sideslip may result in the engine just cutting out. In fact this problem is also present in two-stage missiles with ram/scramjets and will put a fundamental limit on how much they can maneuver in cruise

[Rafoz_]

Scramjets are really good if you want to find water in the desert, they also land often in private pools, at least they have the strongest rocket boost ever made

[petersmythe]

The other reason here is that the optimal turn rate is constrained by human and structural limits. If a ramjet fighter gets into a merge it actually can't get more than a few degrees/sec turn rate because it's stuck at Mach 2.

If a ramjet fighter needs to turn away from an incoming missile, same problem. It is fully committed to whatever direction it's going.

[Stalin_]

The problem is that ramjet and scramjet engines need huge amounts of air, and the plane or the body carrying these engines must be taken by a bomber and launched, which may cause huge amounts of air to enter the engine and heat it gradually to burn the fuel. These engines depend on pressure heating, unlike jet engines that draw air in with turbines and give it to the combustion chamber, then it burns with the fuel and is released in the form of an explosion or pulse. If you insist and want to use these technologies, the solution is to use a turbo ramjet or turbo scramjet, which initially works as a turbojet, and when climbing to high altitudes, it turns into a scramjet or ramjet.

[MrRyanisnumberone]

Mig21 is basically a flying ram jet, it works but it’s basically a rocket with some tiny wings for control and not much else

[MarcusPfeffer-rh]

Theoretically you can do a Turbofan/Ramjet hybrid engine where flaps would direct the flow of high-pressure air around the turbine blades to simulate a Ramjet at high supersonic speeds. And that has actually worked in the past, it’s just not really needed for a fighter and would be very complex, e.g. high maintenance costs and not very efficient.

[Mediocre_Moth]

Simple, because they will simply auto-lock to the nearest body of water, wether it be a puddle or an ocean

[tanalafauzan]

basically they only need to add longer exhaust since some of them already use afterburner which has pretty close principle to ramjet

[morpheus_]

I could see a fighter with a turbo-ramjet like the SR-71 working quite well actually, like other people have said ramjets don’t work well at high AoA maneuvers but ALL dogfights and high G maneuvers take place in the subsonic region anyways. That is where the turbojet would be active, and it would work just fine. The turbojet would be active up to Mach 2 ish, so they could make high G turns at Mach 1.6 if they wanted. Ramjets don’t work until you are above Mach 2. If the plane was intercepting a high speed bomber then they could switch to the ramjet to get Mach 3+.

[jordancambridge]

Instructions unclear I installed Scramjets on my Big Wheel.

[inkycat]

This is called a hybrid engine, you can absolutely combine a Turbo-fan with a Ramjet, it will have it’s tradeoffs including loss of mobility and increased weight etc etc.

[zyxwvutsrqponmlkh]

YF-12 used a ramjet that it could transition to in flight.
Many jet fighters have afterburners which is functionally a ramjet after the compression stage.

[Frost-l]

Two ramjets and 2 scramjets next to each ramjet and boom ultimate fighter jet

[antguy]

As a writer who wants realistic principles in their worldbuilding projects, this stuff *really* helps. Thanks.

[michaelmurray]

The Sr-71 Blackbird uses a pair of J-58 turboramjets which are essentially 2 engines in 1 unit. At speeds below Mach 2, they function like a typical turbojet. Once it got above that speed, they function more like ramjets with much of the air in the compressor stages of the turbojet being rerouted through bypass tubes and being “rammed” into the fuel that it mixes with in the afterburner portion. Hence why they’re called turboramjets.

[Banjogiga]

The difference between missles and planes is the fact that missles actually drop off portions of themselves exactly like a rocket and of course the engine is at the bottom so there must be multiple engines meaning that the designers have the ability to chose ramjets/scramjets while for a fighter jet to do that they would ether have to be air launched or eject a million dollar jet engine out the back and have to have extra systems like explosive bolts which if they failed would cause the entire jet to be destroyed taking the expensive scramjet or ramjets with it of which would be much more expensive than just turbojets due to their experimental and untested background