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Directory:StarRotor Corporation

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StarRotor continuous-cycle engine

At about half the size of a normal car engine, the concept is purportedly two to three times more efficient than conventional internal combustion engines, anticipating 60 to 90 mpg once integrated into automotive applications.

Presently producing compressor applications, while developing the expander applications.



Official Website


On Sept. 9, 2006, from 3:00 to 3:55 pm Pacific time, Sterling D. Allan will be doing a live interview with Mark Hotzapple, co-inventor of the StarRotor Continuous Cycle Engine.


April 24, 2008

"We have been focusing on compressor sales so that we can create a stable economic foundation for our company." (Mark Holtzapple)

Sept. 8, 2006

Mark says they have a second contract secured for a compressor, which they are now building, and a third contract pending. "We are now starting to look like a business."

Mar. 7, 2006

Received by email from Mark Holtzapple:

We got our first order. It is for a $200,000 natural gas compressor, purchased by a major oil company.

Feb. 28, 2006

Received by email from Mark Holtzapple:

We have already completed four generations of compressors. So far, our maximum measured isentropic efficiency is 76%. At this measured efficiency, we can calculate that an engine would be about 50 to 58% efficient.
At the moment, we are in the debugging stages of our Generation 5.0 compressor. We expect it to be completed soon... perhaps next week. We hope to show an isentropic efficiency > 80%... we shall see. If we achieve 80%, then it is possible to have an engine that is 58 to 65% efficient.



Adapted by Sterling Allan from OSEN coverage he helped compose on Nov. 22, 2006.

The Future of the car engine. Could it be the StarRotor? Designed by a 5-year old company in Texas, it’s about half the size of a normal car engine, is 50-60 percent efficient, and - according to it’s makers – will be able to take you from New York to L.A. on just one tank of gas.

The company feels this puppy could make the jump from the lab to under your hood within the next decade.

Device is capable of burning a number of different fuels, from gasoline and diesel to natural gas and hydrogen.

What they have now is the "compressor" side of the engine. The "Expander" side is expected in about a year.

The 4th prototype (compressor) was expected to be completed in November, 2005, followed by testing. The company was expecting 80% efficiency, compared to the 72% they have measured on the 3rd prototype.

Two units have been sold to an oil company for beta testing (are being built now), according to Mark Holtzapple, co-founder and president. A new CNC mill procured this past Summer enables them to now fill orders.

The technology is protected by five U.S. Patents by Holtzapple, who is a professor of chemical engineering at Texas A&M University.

They are presently targeting the "distributed power" market with stationary power units. "The automobile market is very difficult to get into," said Holtzapple.


  • US 6,686,326; Holtzapple , et al. May 3, 2005; Quasi-isothermal brayton cycle engine
  • US 6,684,658; Holtzapple , et al. February 4, 2004; Vapor-compression evaporative air conditioning systems and components
  • US 6,530,211; Holtzapple , et al. March 11, 2003; Quasi-isothermal Brayton Cycle engine
  • US 6,427,453; Holtzapple , et al. August 6, 2002; Vapor-compression evaporative air conditioning systems and components
  • US 6,336,317; Holtzapple , et al. January 8, 2002; Quasi-isothermal Brayton cycle engine


Quoting from

  • The StarRotor engine is projected to be very efficient (45-60%). By simply replacing conventional engines (15-20% efficiency) with a StarRotor engine, fuel economy will double or triple. For example, a conventional luxury car getting about 25 mpg on the highway would get about 75 mpg. A conventional economy car getting 40 mpg would get about 120 mpg.
  • It should produce very low pollution. Advanced combustor technology reduces pollution, including unburned hydrocarbons, carbon monoxide, and nitrogen oxides.
  • It has multi-fuel capability. Any liquid or gaseous fuel can be burned, including gasoline, kerosene, jet fuel, diesel, alcohol, methane, hydrogen, and even vegetable oil.
  • It should be inexpensive to mass produce. The parts count of the engine is about 10% of a conventional automobile engine, and the majority of parts do not require complex machining.
  • There should be no vibrations. All moving components are in pure rotation; there are no oscillating components therefore it is in balance.
  • It should be quiet. Because the gas is fully expanded, there is low exhaust noise.
  • The engine is expected to have a long life and low maintenance. The compressor and expander of the StarRotor engine have a slight clearance between the rotors, resulting in no friction or wear. Also, it should require very infrequent oil changes, perhaps every 100,000 miles. Because it has very few moving parts, it is expected to be very reliable and require very little maintenance.
  • The engine should be smaller than conventional internal combustion engines. The StarRotor engine volume and mass are about half that of a conventional internal combustion engine. A 130-hp engine will occupy approximately 2 cubic feet.
  • It should have a high turn-down ratio. The engine is efficient over a wide range of speeds and torques.
  • The StarRotor engine should be easily scalable. Designs from 50 W to 50 MW are possible.


The fifth-generation StarRotor compressor.  First tested in February 2006. The compressor is 12 inches long by 15 inches in diameter. It is capable of producing a pressure ratio of 6:1, while processing 205 acfm at 6,000 rpm. To date, the fastest it has operated is 3600 rpm with a flow of 129 acfm. Running without liquid or oil injection, it reached >80% energy efficiency at 2800 rpm.Source:
The fifth-generation StarRotor compressor. First tested in February 2006. The compressor is 12 inches long by 15 inches in diameter. It is capable of producing a pressure ratio of 6:1, while processing 205 acfm at 6,000 rpm. To date, the fastest it has operated is 3600 rpm with a flow of 129 acfm. Running without liquid or oil injection, it reached >80% energy efficiency at 2800 rpm.


StarRotor Corporation is a startup company founded to commercialize technology from Texas A&M University. It was incorporated in March 2001 by Dr. Mark Holtzapple and Andrew Rabroker, the original co-inventors of StarRotor technologies. Their novel idea was to use gerotors to process gasses. From this idea the StarRotor compressors, air conditioners, expanders, and engines are becoming a reality.

Having licensed the rights to commercialize the invention from Texas A&M, the company began to refine and develop the StarRotor concept. Between spring 2001 and spring 2005, the company developed a working first- , second- , and third-generation prototype of the StarRotor compressor. The first two working prototypes demonstrated the technology and provided the necessary preliminary testing data. The third-generation compressor resolved many of the technical obstacles, allowing this product to be offered for commercial sale. StarRotor continues to develop the engine, water-based air conditioner, and related technologies.


The company is presently focusing on the distributed electric power industry. After that has matured, it expects that the automotive industry will open, possibly by 2010.


Mark Holtzapple

Mark Holtzapple, Co-inventor and President of StarRotorImage Source: Texas A&M
Mark Holtzapple, Co-inventor and President of StarRotor
Image Source: Texas A&M

Dr. Holtzapple is a professor in the Department of Chemical Engineering at Texas A&M. (Ref.)

Ph.D., University of Pennsylvania, 1981
B.S., Cornell University, 1978

Mark Holtzapple is a professor of chemical engineering in the Dwight Look College of Engineering at Texas A&M. He joined the Texas A&M faculty in 1986. Previously, as a U.S. Army captain and research engineer, he worked to develop cooling systems for chemical protective clothing. Dr. Holtzapple’s research interests include bio-based fuels and chemicals, energy efficiency, and food and feed processing. He holds more than 20 patents and has received numerous scholarly and scientific honors and awards. [1]

Andrew Rabroker

Also of Texas A&M University.

TAMU Distinguished Lecture Series presentation

Texas A&M's Distinguished Lecture Series usually pulls from extra-TAMU individuals, but each year selects two speakers from within TAMU. Mark Holtzapple of TAMU gave the final lecture for 2005-2006 school year, addressing the need for energy solutions, focusing in on solutions via biomass and StarRotor technologies that he has been orchestrating.

Sustainable Energy and Transportation: Engineering the 21st Century

  • Lecture - 223 slide PowerPoint presentation. Refer to these to go along with the video presentation.

In the News

  • The Race to 100 MPG - Gas prices are up, fuel economy is down—but the brightest minds in auto technology are about to do something about it. Chemical-engineering professor Mark Holtzapple and his colleague Andrew Rabroker were attempting to build a better compressor for an air conditioner when they hit on the idea that became the StarRotor engine’s basic architecture. (Popular Science; Sept. 2006)
    • Podcast (mp3) Episode 13 covers StarRotor
  • A Compact Brayton-Cycle Engine and Biomass Process for Mixed-Alcohol Fuels - A Texas A&M chemical engineering professor has developed a process to convert biomass to a mixed alcohol fuel that contains more energy than fuel ethanol. He has also developed a compact Brayton-cycle engine (the same thermodynamic cycle employed by jet engines) capable of being powered by any type of fuel—including his MixAlco mixed alcohol fuel. Prof. Mark Holtzapple projects that his StarRotor engine, which is being developed by a company of the same name, could deliver efficiencies of 49–55% applied in a passenger car—about 2.5 to 3 times more efficient than a conventional gasoline engine. (Green Car Congress; Apr. 28, 2006)
  • Video: KBTX TV3 coverage of StarRotor (Sept. 12, 2005)
  • Aggies design more efficient car engine - Holtzapple said StarRotor has features that customers want but typical engines don't provide, such as high efficiency in oil consumption, low maintenance, low price and a lasting durability. (The Battalion; July 7, 2005)


"StarRotor has a gas turbine engine company with a lot of promise. I give it a big thumbs up. 60% absolute efficiency in an engine capable of half a megawatt of output without gigantic capital outlay is terriffic! It deserves to be high on the Top 100 list." -- Ken Rauen, PES Network, Science Adivisor, and New Energy Congress founding member (Feb. 27, 2006)


Engineering / Manufacturing Facility:
StarRotor Corporation
1712 Gooseneck Dr.
Bryan, TX 77808


Phone: 979-778-2102
Fax: 979-778-1569


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