Frequently Asked Questions
Yes. Firstly, Blue Origin has already constructed and tested a scaled-up version of the JetQuad, known as the Charon Test Vehicle. The vehicle is powered by four jet-engines and has successfully flown to 100 meters and landed back-down, more information is available at:
Secondly, in 2006, NASA has filed a patent for a jet-engine powered vertical take-off and landing vehicle. The link is shown below.
Lastly, in 2010 University of Southern California has filed a provisional patent for my original AirBooster concept, during the USC annual Innovation Showcase.
In 2010, I also presented the AirBooster concept at Southeast Regional AIAA Student Conference, competing in the Master's Division papers.
To clarify, $10,000 is the estimated materials/engine cost of constructing the first prototype of the JetQuad, which is a specialty designed vehicle, one of it's kind. We expect that the production-model, when mass-produced, will cost less.Last updated:
No. The JetQuad is not a project that is related to my research at ASU. For my PhD Dissertation I am researching other advanced rocket-based propulsion concepts.
The JetQuad is derived from the AirBooster technology, which is something I have been researching on my free time, for fun, since 2008.Last updated:
The lubrication system of a jet-engine is designed to operate with the jet-engine in horizontal orientation. How reliable are the engines in vertical orientation?
So far, we have logged close to 5-hours of combined engine operation using our one and only Xtreme Turbines X24 engine, which is a very basic engine. From the beginning, the engine has only been operated in vertical orientation, with the exception of the last few tests on the test-stand, when the engine was in horizontal orientation. So far, with the exception of the occasional "wet" start (some flames during start), we have observed no decrease in performance or reliability from operating the engine in vertical orientation.Last updated:
In the dynamic model, the derivative of engine thrust is coupled directly to vehicle rotation. Does this mean that flight stability software is impossible to build?
With the advent of modern simulation tools and a plethora of software, we are confident that flight stability software can be developed. Our current dynamic model already performs the mentioned coupling. We are not saying this is easy - it will be challenging to program a corresponding controller, but certainly not impossible.Last updated:
Why would you use the JetQuad to boost rockets to the edge of the atmosphere if conventional rockets can do the same thing?
To begin, JetQuad is fully-reusable, and consumes significantly less propellant then an equivalent rocket stage. Also, the propellant (Jet-A fuel) is readily available at local airports. So right off the bet, the operator saves money by not having to dispense the rocket-stage and use complicated fuels. To add to that, JetQuad is much safer to start, since it starts operation at 25% throttle (idle). Furthermore, the jet-engines are rated at 25-hour of operation between maintenance, further enhancing the reusability factor of the JetQuad.
As an additional note, the idea of JetQuad and AirBooster vehicles, in general, is to compete with Boost Launch Providers like Virgin Galactic White Knight 2 and Orbital Pegasus which is launched a giant Airliner, just to name a few.Last updated:
There is a common misconception that air-planes are much more efficient at boosting rockets then equivalent jet-engine powered stage, like the JetQuad. However, there is one key detail here that is important to consider. The jet-engine powered stage does not have wings, control surfaces, fuselage, cabins, wheels, etc... So although a jet-engine powered stage has to generate a lot of thrust to launch vertically, it is still less thrust, then an equivalent air-plane, since you are actually starting-out with a much smaller vehicle. To be specific, the JetQuad is 10 times smaller than an equivalent carrier aircraft designed to loft the same payload to 10km altitude.
Another critical aspect to consider is that all aircraft-launched rockets first pitch-up to gain more vertical velocity before pitching back-down. in the process, they lose a fraction of the original horizontal velocity provided by the carrier aircraft. On the other hand, the JetQuad sets-up the rocket in an ideal pitch-up state and provides it with a vertical velocity component. No complicated maneuvers needed, the rocket simply disengages from the JetQuad and continues upward.Last updated:
The number of engines used is a design choice based on several factors. Firstly, to control roll of the vehicle, we are using throttle and de-throttle of opposing engine pairs. From this perspective, four engines is the minimum amount of engines needed to perform this type of maneuvering.
Although our first prototype AB1, was underpowered, the second one, AB1.1 wasn't. Even though AB1.1 has only one engine, it blasted off easily at just 70% throttle. The four-engine configuration is actually slightly over-powered with a Thrust/Weight ratio of 3.4:1. Hence, any more engines then four, like six or eight, is simply not necessary, at least not at this point of technology development.Last updated:
Jet-engines are known to have a higher throttle response delay than equivalent quadcopter electrical rotors. How does this affect the functionality of the JetQuad?
There are two types of delay that occur for the jet-engine that one does not experience with conventional Quadcopters. The first delay occurs between the throttle and the turbo-shaft spooling-up to a given RPM, this delay is measured as the delay between throttle signal and turbine torque applied on the engine. Once the turbine spools-up, more air is drawn into the engine and it takes some more time for the additional air to heat up and produce the additional thrust. This is the second delay.
The jet-engine that we end up using for the jet-quad will be mounted on a jet-engine test stand where these delay values will be directly measured. These values are not constant are actually functions of the throttle position.
We will then import the table relating throttle and throttle-delay for both torque and thrust directly into the dynamic model. After that, we will design the necessary controllers to mitigate these delays. As mentioned before, the vehicle will not be as responsive as a Quadcopter, but will still be capable of flight.Last updated:
Because of the engine-tilt, the turbine moment has two components, with the primary component, acting on the vehicle's rotation along the vertical axis, and the secondary minor component acting on the longitudinal, x-axis. The tertiary torque, is caused by the rotating air-stream as it drags on the inlet and outlet of the engine.
We intend to characterize the thrust and torque of each engine using a jet-engine test stand. This will performed prior to mounting the engines into the JetQuad vehicle.Last updated:
Besides the issue of stability, the previous prototypes lacked a few key features, unavailable due to funds.
At first, the JetQuad will be equipped with an altimeter so that it may perform smooth take-off and landings. We will also be using a Telemetry system to save-off real-time data to review later and optimize system performance. Eventually, we would like to use a GPS system to program the JetQuad for both lateral and vertical translations.Last updated:
What happens to the performance of the JetQuad as it ascends to greater altitude? Don't the turbines stop working from lack of air?
When considering a constant acceleration ascent of the JetQuad, several factors have to be taken into account. The air pressure drops resulting in a decrease in stagnant pressure at jet-engine inlet. However, since the JetQuad is accelerating, the dynamic pressure acting on the inlet actually increases - inlet ram effect. An increase in dynamic pressure compensates for the decrease in stagnant pressure resulting in relatively consistent performance from ground to 33,000 feet.
A few years ago we have ran a unique C++ code to examine the performance of the jet-engine as it ascends through the atmosphere in a vertical orientation. The analysis included full thermodynamics at all engine stations, inlet, compressor, combustor, turbine, nozzle. The results confirmed the ram-drag assertion.Last updated:
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