The scramjet engine can be connected behind the ramjet as the afterburner.

The "Skylon" is a very ambitious project, which is made for the successor of the banned HOTOL-program, by British Airspace. The purpose of the "Skylon" is to create a space shuttle, which can operate from the regular airbases and take 30 astronauts to space.  In the second film is the introductions, how the British "Skylon" shuttle air-breathing rocket is made.

Sometimes people have asked, why the shuttle is not equipped with the separated turbojet, ramjet, and scramjet engines? The "Skylon" is easy to turn to VTOL-shuttle by using the extra vertical turbojets, which will rise the shuttle above the ground, and then the shuttle can turn to use its main engines.

Turbo-rocket scramjet would be the best engine system, what people can ever imagine. The system can use the separated turbojet, ramjet, and scramjet engines. So that means the system would not be very complicated. The acceleration would happen in stages. And if that kind of aircraft will turn to space plane, the system needs the flap ahead of the ramjet or scramjet engine. That flap is closing the air intake, and then the oxygen will start to inject along with fuel in that chamber.

 

That allows the craft to operate at the LEO (Low Earth Orbit) or suborbital missions. When the craft is traveling outside the atmosphere, it uses internal fuel and oxygen. When the craft is diving in the atmosphere it can start to use scramjet or some other engine type. The combination of turbojet, ramjet, and scramjet engines makes it possible that the craft and operate at the atmosphere and suborbital trajectories at the same time.

The low-speed abilities of hypersonic aircraft are really weak, except if the aircraft is equipped with a turbojet, ramjet (supersonic engine), and scramjet (hypersonic engine)engines. The aircraft would use turbojet for normal lift-off and then the craft can turn to use the ramjet engines, when the speed is high enough the scramjet will start to operate. There is the possibility that the scramjet will install after the ramjet as the afterburner.

When the speed of the system is increasing high enough, the fuel injection to the ramjet engine will stop, and the system would turn to start the fuel injection to the scramjet system. The turbojet engines can equip with iris, whose mission is to close the air intake, and that thing denies the damage in turbines. The electricity to the aircraft can deliver by using an air turbine, what is the windmill, what the intaking air will rotate. This kind of system allows connecting the good slow-speed abilities to the hypersonic capacity of the aircraft.

https://en.wikipedia.org/wiki/British_Aerospace_HOTOL

https://en.wikipedia.org/wiki/Ramjet

https://en.wikipedia.org/wiki/Scramjet

https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29

https://en.wikipedia.org/wiki/Turbojet