By John Hamilton
WHITE SANDS MISSILE RANGE, N.M. — Members from Air Force Research Laboratory, NASA and the Naval Surface Warfare Center Port Hueneme division, White Sands Detachment, are working together to ready the Hypersonic International Flight Research Experimentation (HIFiRE) Flight 2 research vehicle for launch later this year.
Preparations to fly a new high tech engine are currently underway at White Sands Missile Range.
Members from Air Force Research Laboratory, NASA and the Naval Surface Warfare Center Port Hueneme division, White Sands Detachment, are working together to ready the Hypersonic International Flight Research Experimentation (HIFiRE) Flight 2 research vehicle for launch later this year. The experiment itself is part of a joint effort between NASA and the Air Force, with the Navy providing the rocket and launch system the experiment will be flown on.
HIFiRE Flight 2 is an experiment being conducted to study and evaluate a special kind of engine called a scramjet. The scramjet, or supersonic combustion ramjet, and its related systems, are being readied at White Sands for flight later this year in Hawaii.
The HIFiRE Flight 2 scramjet is an advanced jet engine designed to function at extremely high speeds. “A scramjet operates in what we call the hypersonic area, somewhere in the neighborhood between Mach 5 and Mach 12,” said Sal Rodriguez, deputy for the White Sands Naval detachments test branch.
Typical jet engines function by using a series of large fans to draw air into the engine and pressurize it. This pressurized air is then mixed with fuel at subsonic speeds and ignited, which increases the air’s temperature and generates even higher pressures. The engine then expands this hot, pressurized air out of the back of the engine to generate thrust and push the engine, and whatever it’s attached to, forward.
A ramjet uses this same process but eliminates the fan. Instead the ramjet uses its own forward momentum and shape to take in air from the outside, slow it down to subsonic speeds and pressurize it. Fuel is then injected and ignited generating thrust similar to conventional jet engines. The HIFiRE Flight 2 scramjet works in roughly the same fashion as a ramjet, with a key difference being that a scramjet doesn’t slow the air down to subsonic speeds before mixing it with its fuel and burning it, allowing the scramjet to operate more efficiently then the ramjet at higher speeds.
The reason why a system like this is so important is because reaching and sustaining hyper velocity speeds is very hard to do and designers of such aircraft have to leverage every resource possible. “To go at those velocities, you have to do a lot of weight management so you could design an engine that doesn’t weigh as much. That’s where the limitations are with a conventional supersonic engine where you see a turbine, they are very heavy and they can only get you so fast,“ Rodriguez said.
Since the scramjet only works at high speed, it is typically brought up to speed using conventional technologies such as solid-fueled rocket engines. In the case of the scramjet experiment being prepared at WSMR, this means mounting it on the top of a Terrier-Terrier-Oriole sounding rocket. “We, the Navy, are partnered with [AFRL and NASA], we’re basically the bus, we are providing the bus that this payload is going to ride on, “ Rodriguez said.
The experiment will be conducted by launching the scramjet atop the rocket. Using the rocket’s first two stages to get to the proper altitude, the third stage with the payload still attached will coast unpowered into the right orientation needed for the experiment.
Then the rockets in the third stage will then fire, bringing the scramjet payload up to speed where the scramjet engine experiment will be activated. The HIFiRE Flight 2 scramjet experiment is not designed t be a complete vehicle. For this reason, the rocket is being used to push the scramjet up to the speed required for the engine to function, allowing scientists to focus on collecting data to better understand how the scramjet engine actually works.
“It really simplifies the payload systems that we need to have. We don’t have to have the payload itself accelerate through that Mach range. We can use the booster rocket to do that for us so we can focus on the science and research objectives,” said Kevin Jackson, HIFiRE Flight 2 project lead, AFRL.
To ready the scramjet for its moment of hypersonic glory technicians, engineers and researchers gathered at WSMR are looking at how the design will ride on the rocket that will launch it.
White Sands technicians, with engineers from AFRL and NASA, take careful measurements to evaluate the weight distribution of the HIFiRE Flight 2 research vehicle. Since the rocket will spin in flight, the payload’s weight has to be well-balanced to ensure stable flight. Should the weight distribution be off, the forces generated by the spin could cause the rocket to veer off course.
At this time, scramjets similar to the one to be flown HIFiRE Flight 2 are purely experimental systems, with only the experimental X-51A aircraft utilizing such an engine. In the future, it’s hoped that scramjet technology will be used to power high speed military aircraft and weapon systems, and to power spacecraft as they accelerate through the atmosphere toward space. “You could use a scramjet as say a mid stage or second stage boost engine for space access,” Jackson said.