Supercharged Ejector Ramjet (SERJ)

[Jane-DoH]

I've been doing some reading on Supercharged Ejector Ramjet (SERJ) engines, and from what I remember reading it used a series of ejector rockets to effectively entrain air and force additional air through the ramjet allowing it to function at low airspeeds with a fan added at the front of the engine, driven by a separate turbine at the front of the engine, to enhance the effect by drawing in air and compressing it prior to it going into the duct. Some designs to function at higher speeds had the means for the fan to rotate out of the duct.

The part I seem to have difficulty grasping is how they managed to keep the fuel consumption down -- rocket engines guzzle gas at unbelievably high rates which is why they aren't used in most aircraft designs -- unless they planned to shut the rockets down once they were flying fast enough to keep the ramjet running by itself.

While I'm at it, modern day they could use a pulse-detonation engine in lieu of the rockets correct?

[EEngr]

Rocket fuel consumption

Propulsion newbie here.

I always thought that rockets' primary drawback was their high consumption of oxidizer, which they have to carry around.

[Jane-DoH]

I didn't know that... I thought they just burned fuel fast

[EEngr]

I didn't know that... I thought they just burned fuel fast

Partly true. The stereotypical rocket following a ballistic flight path is going to consume more fuel than a vehicle that can take advantage of aerodynamic lift*. But the stoichiometric oxygen/fuel mass ratio (for ethane) is about 3.5:1. So for every pound of fuel, you've got to carry 3.5 pounds of O2.

*The stereotypical rocket heading into orbit also suffers from having to pass through a broad range of airspeeds and altitudes quite rapidly. Designing an air-breathing propulsion system that could adapt quickly enough would be quite a challenge. For an airplane (SR-71 for example) that spends a considerable amount of time cruising within a smaller range of altitudes and speeds, its an easier problem to solve.

[TAAMGuy]

I believe if you check the NASA webpage you will see that the space shuttle carries about 4 times the liquid oxygen as liquid hydrogen. Well, at least once more anyways.