Beginning in early 2000, XCOR began testing a small integrated rocket engine that incorporated all the elements of a larger engine, but allowed us to validate engine improvements quickly and cheaply. The Tea Cart (named for its installation on a rollaround cart and the heated cooling water it produces) is a 15 lbf nitrous oxide/ethane engine that, despite being our oldest engine, is still called into service quite frequently as an R&D device and public demonstrator.
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 Holiday Inn’s management – and to the delight of the attendees – the engine was fired several times in the hotel’s conference room. The Tea Cart was the working illustration of our company’s philosophy of reliability, reusability, maintainability and relative ease of operation. In addition, we were satisfied that the engine was subjected to a wide range of operating environments before it had a public demonstration. We worked closely with the Kern County and Scottsdale fire marshals to insure that everything we did 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.