Building the scramjet that works
In blog 2 we talked a little bit about how a scramjet can operate at hypersonic speed.
Today we will talk in more detail about some of the problems that we have solved to build a scramjet that works.
Here in Australia, we have led the world in hypersonic flight research over the last 20 years. Researchers at the University of Queensland developed the scramjet engines used for the SPARTAN.
Over 100 people earned their doctorate (PhD) here while solving some of the challenges unique to scramjets. We have accumulated a vast body of knowledge and experience right here in Australia, overcoming difficult technological obstacles using hypersonic wind tunnels, some of the world’s fastest computers and most importantly some good Australian ingenuity.
Join us as we continue to lead the world in the hypersonics race.
Problem 1 - Ignition
Scramjets do not work below Mach 5. But once that speed is reached, they are the most efficient engine we know of.
Figure 1 shows the components that make up a scramjet. The inlet, or intake, collects the air as the vehicle travels along at hypersonic speed. This generates shock waves, that compress the air so that it is hot enough to burn fuel. Next the air enters the combustor, where fuel is injected.
This is one of the most difficult parts of the engine, as the air remains supersonic throughout and is moving extremely fast through the engine.
For combustion to occur, the fuel must be able to mix with the oxygen in the air (air is made up roughly of 21% oxygen and 79% nitrogen), and then burn before the air passes out the back of the engine.
This has to happen very quickly. Say our scramjet combustor is 2 metres long, as is the case for our SPARTAN scramjet.
At Mach 8 the air passes through the scramjet at approximately 2000 metres/second. So that means that the fuel must mix and burn with the air in one thousandth of a second!
This is not easy to accomplish.
It is like trying to keep a match alight in a cyclone.
It's like trying to keep a match alight in a cyclone
Problem 2 - Changing conditions with changing speeds
For access-to-space, the scramjet must accelerate from Mach 5 to Mach 10.
However, creating more thrust than drag is not the hard part.
As the speed increases at hypersonic speeds, conditions change substantially. It must therefore be able to operate under a range of conditions as it accelerates.
Figure 2 shows a UQ designed scramjet engine that was tested in a hypersonic wind tunnel. Its shape allows it to operate successfully over a large speed range.
The SPARTAN scramjet starts working at Mach 5 and increases speed to Mach 10, before releasing the upper stage to go up to space. As it does this the angles of all the shock waves change, and so does the air velocity and temperature through the engine. The SPARTAN scramjet is able to account for this and still generate thrust.
Now we want to use the results of the decades of hard work that have gone into developing Scramjets in Queensland.
With the inclusion of Scramjets, our launch system is much more efficient than the existing rocket-only launch systems that the rest of the world is using.
This offers huge immediate benefits and opens up exciting future possibilities.
It’s time to take SPARTAN into the real world and that is what we are doing at Hypersonix.