Experimental Engines

XCOR has designed and built a number of experimental engines. The XR-2P1 is among the longest lived and most versatile of all these engines.


Beginning in early 2000, XCOR began to test a small integrated rocket engine that incorporated all the elements of a larger engine, but allowed XCOR to validate engine improvements quickly and cheaply. The Tea Cart (named for its installation on a roll-around cart and the heated cooling water it produces) is a 15 lbf nitrous oxide/ethane engine that, despite being XCOR’s oldest engine, was called into service quite frequently for many years as an R&D device and public demonstrator.

The Tea Cart was the working illustration of XCOR’s philosophy of reliability, reusability, maintainability and relative ease of operation.  By late April of 2000, the Tea Cart engine was publicly demonstrated at the Space Access Society’s annual meeting in Scottsdale, Arizona. With the approval of the local fire marshal and the conference’s hotel management–and to the delight of Space Access attendees–the engine was fired several times in a hotel conference room. In addition, XCOR was satisfied that the engine was subjected to a wide range of operating environments before it had a public demonstration. XCOR worked closely with the Kern County and Scottsdale fire marshals to insure that this engine and its tests met with their approval.

The Tea Cart engine continued to support unique research. In early 2006, XCOR and ATK GASL received a DARPA contract to "investigate, develop, and demonstrate a novel configuration for a liquid rocket engine, namely a Third Fluid Cooled (TFC) liquid rocket engine," for which we used the Tea Cart to generate superheated steam suitable for driving a Rankine cycle. This steam cycle will allow a turbopump system to develop high chamber pressure in a more efficient way than staged combustion cycles, thus improving the performance and durability for boost propulsion, as well as orbital transfer applications.  The Tea Cart engine was pressed well beyond its original design parameters to higher temperatures and pressures than it had ever seen before, and provided cost-effective proof that this new technology is feasible.

The objective of this project was to provide DoD with technology enabling the development of higher performance liquid rocket engines. XCOR’s extensive work on this 15 lbf water-cooled test engine served to simplify the propulsion needs for future vehicles. In successful tests of the Tea Cart engine we have demonstrated that it is possible to turn down coolant flow until steam is generated in the cooling jacket.

We believe that many tests on a small engine are better than no tests on a large one. As of this date, the Tea Cart has an accumulated run time of more than 150 minutes in 1,837 main stage runs, as well as thousands of igniter tests.

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