I see it was the seventh test, not sixth.

You've all probably seen this one by now, too.

http://www.space.com/spacenews/americas/x33_x33_7012.html

X-33 Engines Slated For Thursday Hot Fire

By Brian Berger, Space News Staff Writer
posted: 05:32 pm ET, 11 July 2001

WASHINGTON — The engines built for the NASA-Lockheed Martin X-33 are expected to rumble to life Thursday, July 12 as NASA resumes testing of the engines despite the overall program’s cancellation earlier this year.

NASA officials decided this week to proceed with a series of three hot fire tests of the X-33’s powerful linear aerospike engines. The focus of those tests will be the performance of the engines’ electromechanical actuators, or EMAs for short.

"We just got the word that they are going to go forward and do the testing," NASA spokesman Dom Amatore said July 11. "It’s a go."

Amatore said the tests could begin July 12 at Stennis Space Center near Bay St. Louis, Mississippi, with a brief ignition test.

Gary Lyles, manager of NASA’s Propulsion Project Office at Marshall Space Flight Center, Huntsville, Ala., told Space News in June that the series of tests under consideration, which would culminate with a full-throttle 100 second burn, are designed to see how the engines’ EMAs perform under realistic conditions.

EMAs control the flow of fuel to the engine and are considered one of the truly new technologies incorporated into the linear aerospike design. Today’s rocket engines, in contrast, rely on hydraulic actuators, which are prone to leaking.

NASA canceled the X-33 program in March, but elected to continue the EMA testing in May as an in-house project assigned to Stennis, with Boeing’s Rocketdyne Propulsion & Power division providing engineering support. The testing continued with $3.8 million in funding from NASA’s Space Launch Initiative, a $4.8 billion effort to develop reusable launch vehicle technologies.

The two experimental XRS-2200 aerospike engines were built by Rocketdyne.