Record Breaking Supersonic UAV Being Developed at CU
Unmanned Aerial Vehicles are ubiquitous in the world today. We routinely hear stories about
their use, mostly in combat settings, but more and more in first response disasters situations.
Common to all these applications is the fact that the vehicles are flying subsonically. The
Predator flies at a max speed of 135mph and the Global Hawk at 497mph. Starkey Aerospace
Corporation (Starcor), a recently formed company in Colorado, is planning to extend the flight
regime to Mach 1.4 (1075mph) with the GoJett. This puts the GoJett in a new, exciting and very
useful category of UAV.
The GoJett is the work of Assistant Professor Ryan P. Starkey and his students at the University
of Colorado – Boulder. Work started in 2009 as a project at the university to improve the
performance of small turbine engines. As worked progressed on the turbine engine performance,
it was clear that significant improvement was possible. A vehicle was needed to showcase the
improved performance that was being achieved. Enter the GoJett seen in Figure 1.
Work continued on both the turbine engine and the vehicle until it became clear that there was
government and industry interest in both the engine and the UAV. In January 2012, the work
entered the incubator stage with eSpace – The Center for Space Entrepreneurship. eSpace is a
partnership of the University of Colorado and Sierra Nevada Corporation’s Space Systems
Group. eSpace is a 501(c)(3) non-profit organization formed to support the development of
entrepreneurial space related companies and personnel to support these companies. Starcor
entered the eSpace incubator to develop a high efficiency lubrication free gas turbine engine and
provide high-speed UAV development and test services.
One of the programs at eSpace is designed to help transition technology from the university
research sphere into the business world. Professor Starkey formed Starkey Aerospace
Corporation (Starcor) in January 2012 and is actively working with an executive mentor
arranged by eSpace.
Worked started with improvements to small turbine engines; engines in the 45 lb thrust class. See
Figure 2. The AT-450 engine manufactured by US Microjet has had it performance improved by
60% with the addition of an afterburner with a variable area nozzle and an additional 100%
improvement is possible via a new combustor can and turbine stage. Based on this proof-ofconcept development, Starcor has started developing its own engine for use in the speed record
which will include fluidic thrust vectoring. High fuel consumption of small gas turbines is
another problems tackled by the engineers at CU.
The GoJett is a 110 lb UAV (based on FAI air vehicle classes) and is being designed to set the
speed record for this class of vehicle. See Figure 3. Once this has been achieved, future designs,
which can be heavier and longer as needed, will be developed to provide access to flight test
regimes of interest for sonic boom reduction, storm penetration, and tactical and ISR missions at
a relatively low cost. The current vehicle is 6 ft long and has a Mach 1.4 flight range greater than
30 miles, the minimum range needed to complete the speed record.
As long as the vehicle stays below the proposed Mach 1.4 there will be no problems with vehicle
heating from viscous effects. To extend vehicle speeds to higher Mach numbers to test transition
from turbine to ramjet operations will require attention to this problem. Professor Starkey
pointed out that in these flight regimes, heating will destroy the turbine. However, the cost of the
turbine is small and providing access the high Mach flight regime makes this very cost effective.
Additional development work could, of course, address the turbine heating issue.
Aside from this exciting new technology is the example set by Starkey in several areas.
Firstly, the educational model for engineering students illustrated by this work. Griffin in his
speech at Purdue echoed the sentiment of Professor Gordon of the University of Reading that we
are troubled by how to educate students in the art and science of design as well as the analytical
side of engineering. Starkey has shown that he can use students at the undergraduate level,
through senior level capstone projects and graduate level student research to develop new
designs as well perform cutting edge analytical work to support the design work. It is an example
of “getting the design right” in order to choose the right design to go forward.
Secondly, he has shown how new technology can progress from university research projects to
incubator stage company formation. This not only brings new technology to the industry, but it is
providing jobs for the region as well as newly minted engineers from CU.
Thirdly, CU though its partnership in eSpace along with Sierra Nevada, has provided a path for
this educational model to succeed and increased the economic vitality of the region. This is the
kind of outcome that demonstrates the worth of our investment in educational institutions.
Interview With Professor Starkey
When the history of Starcor is written, what was the genesis of the idea when you look back?
It started with the desire to develop lower cost, higher performance small turbojet engines.
What was the enabling technology?
The small turbojets that we have been developing are twice as efficient as similar off the shelf
engines (based on test data). Further work on bearings, manufacturing, afterburners, nozzles,
and thrust vectoring will all add to the baseline performance and capabilities. We will also be
integrating a generator to power the vehicle electronics. The ultimate goal is to have a family of
engines built off of a common core so that the price, performance, and maintenance schedule
can be determined by the customer.
What are the challenges ahead: Technical, Business Development?
The biggest business challenge is transitioning a University based operation to a small company.
Fortunately, I have lots of good help from eSpace who is incubating the company, as well as
advisors. These challenges involve finishing our prototype engine in a timely manner and
obtaining sufficient funding to go through both low and high speed flight testing. The biggest
Technical Challenge is that every component within this vehicle is custom – no off-the-shelf
components are readily available. The most critical of these is the flight control system. We have
been fortunate to work with Blackswift Technologies - another CU spin-off company - who has
been developing a custom system for our needs.
What are the range and loiter time you are planning? Can you fly out supersonically, loiter
subsonically and then return supersonically or subsonically?
We are not disclosing range or loiter time currently, especially since our baseline vehicle is
designed to set a world record and is therefore limited to 50 kg. We could be much heavier (i.e.,
carry more fuel) and improve on both of those metrics. Also, it is tied into the cruise Mach – our
performance will be maximized at high subsonic conditions without the afterburner. Yes to your
second question – there are no limitations on how the mission is accomplished.
Will skin heating be a problem? Are you planning for expansion of materials?
Yes and no. At Mach 1.4 where we are targeting it is not too much of an issue. We will have no
issues building our system out of carbon fiber. Our biggest heating problems are internally
(electronics) and the around the engine.
What is your timeline for development?
The Engineering Test Unit is currently under construction. This will be used for manufacturing
and integration purposes and will also be used for hardware-in-the-loop and low speed flight
testing. The supersonic vehicle will likely be built in the Spring of 2013.
What is the plan for returning data to the base?
We currently have both streaming video and data during the flight as well as on-board data
storage.
What are plans to apply the GoJett to high speed testing?
This is the true strength of this engine/vehicle in that they will enable low cost supersonic flight
testing. We are also working on increasing the performance of this engine to push toward ramjet
takeover.
Is testing of the Mass Injection Pre-Compressor Cooled (MIPCC) concept contemplated?
Yes, but no specific plans/funding is in place yet to pursue it.
Figure 1. GoJett Vehicle in Flight
A rendering, created by master's degree student Greg Rancourt, of the UAV. (Courtesy Ryan
Starkey)
Figure 2. Professor Starkey's Team Reviewing Turbine Development
CU-Boulder Assistant Professor Ryan Starkey, left, with some members of his team, looks over
engine model nozzles for a first-of-its-kind supersonic unmanned aircraft vehicle, visible in the
rendering on the computer screen. From left are Starkey; Sibylle Walter, doctoral degree
student; Josh Fromm, master's degree graduate; and Greg Rancourt, master's degree student.
(Photo by Glenn Asakawa/University of Colorado)
Figure 3. GoJett Engineering Test Unit in Fabrication
Held by Brandon Bosomworth, master’s degree graduate (Photo by Edgar Flores, master’s
degree graduate/University of Colorado)