Posted on 11/10/2004 9:31:28 AM PST by the_gospel_of_thomas
How about pressure? Does breathing liquid in deep-sea applications help with that pressure? Saw it in the ovie "The Abyss"...
31 - "Okay, so if Mach 5 is "3800 mph", how can Mach 10 be "about 7200 mph"?"
Mach is a measurment of the speed of sound, in the air. This varies with air density. Mach 1 is basically the speed of sound at sea level.
So linear distance speeds are not equivalent measures to mach speed.
At sea level, Mach 1 is 760 MPH. At 35,000 feet, Mach 1 is 660 MPH.
If we and you are only really concerned with ten seconds or so why use a scram jet to begin with as such a propulsion system relies on a rocket to bring the craft up to speed to allow operation of the scramjet? Rockets work fine for short distances where velocity is crucial such as shooting down an aircraft or bringing down a missile but for larger, slower targets in the atmosphere, there is the cruise missile. Air breathing, hypervelocity aircraft are still a research program and will be for some time to come.
Your question really needs to be rephrased, more along the lines of "How can an engine be designed to work on an aircraft that travels at very high speeds.?"
A typical turbojet engine with a compressor and turbine needs to slow the air entering the engine down to subsonic speeds before it enters the compressor or the engine will suffer serious problems. Also, there is an upper limit to the speed at which a turbojet can operate because there is a point where the air entering the engine can't be slowed down to subsonic speeds.
On ramjets and scramjets, there are no moving parts to cause problems because the air entering the engine is compressed by passing through shockwaves. On a ramjet the air flow behind the shockwave (which is external to the engine) is subsonic and at a higher pressure than in front of the shockwave. It passes into the combustion chamber where it is mixed with the fuel and ignited. The resulting expanding gases provide the thrust. Like the turbojet, there is an upper limit to its speed.
In a scramjet, as in the ramjet, the incoming air is compressed by shockwaves (the shockwaves can be external or internal to the engine). The difference in the scramjet is that the airflow is supersonic all the way through the engine. The (theoretical) advantage of the scramjet is that the top speed is limited by heating and structural issues instead of velocity.
How does one start one of these - wouldn't the air have to already be moving through the engine at that speed before turning it on?
Correct, neither ramjets or scramjets produce static thrust.
pardon the profanity...
but this kicks ass.
I believe it was twenty minutes.
First "cruise missile", yes.
But the power was provided by a "pulse-jet", a kind of two-cycle engine that had a compression and exhaust cycle.
To my knowledge, no other aircraft has ever employed such an engine.
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