NASA considering X-33 engine tests as Pentagon ponders program pickup

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Testing proponents are proposing three separate hot firings, starting with a five-second ignition test and working up to a full-throttle 100-second burn.

WASHINGTON — The powerful linear aerospike engines intended for the orphaned X-33 experimental rocket could rumble to life this summer under an agreement being hammered out between NASA and the engines’ manufacturer. 

Pentagon officials are weighing a U.S. Air Force takeover of NASA’s troubled X-33, a subscale model of which is shown above returning from a 1998 drop test. Credit: NASA photo/ Tom Tschida

Officials from NASA and Boeing’s Rocketdyne Propulsion & Power division are scheduled to meet June 27 at the engine maker’s Canoga Park, Calif., headquarters for a pivotal discussion of the merits of hot-fire testing the X-33’s main propulsion system.

 Proponents hope to convince a key NASA Marshall Space Flight Center official — Garry Lyles, manager of the Space Launch Initiative’s Propulsion Project Office — to endorse a series of three hot-fire tests that would begin as early as July. Rocketdyne officials have been pushing for continued testing since at least April. 

“We hope NASA will give us the green light to proceed with the hot-fire series,” Rocketdyne spokesman Dan Beck said. 

Lyles told Space News he has not made up his mind, but will present his recommendation to Marshall Director Art Stephen- son and other senior NASA officials upon his return. 

NASA spokesman Dom Amatore said the U.S. space agency will decide by the end of June whether to proceed with the tests. 

The two Rocketdyne-built experimental XRS-2200 aerospike engines have remained on their test stand at NASA’s Stennis Space Center, Miss. since the space agency withdrew its support from the X-33 program in March

While X-33’s future is still in limbo pending a U.S. Air Force decision on whether to pick up the program, low-level testing of the engines has continued with $3.8 million in funding from NASA’s Space Launch Initiative, a $4.8 billion, five-year effort to develop reusable launch vehicle technologies. 

Lyles said NASA decided to continue testing the engine’s electromechanical actuators in May as an in-house project as- signed to Stennis Space Center, with Rocketdyne providing engineering support. 

Electromechanical actuators, or EMAs for short, 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.

Lyles said hot-fire tests will be approved only if they are deemed useful to the ongoing EMA work, which is scheduled to run through September. “We are not interested in risking the engine for a little bit of data,” he said. 

Still, Lyles said firing the engine could prove the best way to see how the actuators perform under realistic conditions. “What a hot-fire gives you is the right ambient conditions for the actuators and the right loads flowing through the valves,” he said. “It’s the final confirmation, but we have gotten a lot of data on the actuators otherwise.” 

Proponents of the testing are proposing three separate hot firings, starting with a five-second ignition test and working up to a full-throttle 100-second burn. Lyles said he will weigh the costs against the potential payoffs of the hot-fire testing before making his recommendation. “Cost is a factor,” he said. “If it’s going to cost me more money than we’ve got, then that’s a factor.”

Meanwhile, the prospect of hot-fire testing is welcome news to officials with X-33 prime contractor Lockheed Martin, who are trying to persuade the Air Force to adopt the program. NASA has been taking steps to close out the troubled program ever since passing it over for Space Launch Initiative funding. 

“The tests they are planning are certainly compatible with what we would have carried through with the X-33-related tests, so that’s good news,” said Evan McCollum, a spokesman for Lockheed Martin Space Systems of Denver. 

NASA and the X-33 team fired a single linear aerospike engine 14 times in 2000. This year’s tests were to focus on firing two linear aerospikes in tandem. In January, NASA conducted the first of nine dual-engine hot-fire tests that would have culminated in a firing lasting for several minutes to simulate the X-33’s planned flight profile. 

Lockheed Martin’s hopes of resurrecting the X-33 are based on the thinking among some Air Force officers that the program would bolster proposed military efforts to develop reusable space vehicles. Such vehicles include a military spaceplane capable of reaching any spot on the planet in a matter of minutes and a so­-called Space Maneuver Vehicle that could be launched on short notice to execute surveillance and reconnaissance missions over targets not adequately covered by satellites. 

Air Force Major Nate Titus, program manager for the Space Maneuver Vehicle, said the military could apply the X-33’s thermal protection system, for example, to its own reusable spacecraft.

Senior NASA and Pentagon officials discussed a possible military takeover of the X-33 program at a meeting at NASA headquarters here June 7. Among those in attendance were NASA Administrator Daniel Goldin and Air Force Gen. Ralph Eberhart, commander-in-chief of U.S. Space Command. 

The leaders appointed a gov­ernment-industry team to study transitioning X-33 to the Air Force. The team includes officials from NASA, the Air Force, the U.S. National Reconnaissance Office, Lockheed Martin and Boeing Co. of Seattle. 

The two-month study also will evaluate a new or expanded Air Force role in NASA’s X-34 and X- 37 experimental vehicle programs, NASA and defense officials said. 

In a written response to Space News questions, Air Force spokesman Maj. Andy Roake said it is premature to comment on whether the Air Force has sufficient funds to take over the X-33 program. Goldin said NASA endorses the idea of transitioning X-33 to the military and is willing to assist in the process but cannot afford to keep the program running in the meantime. 

“Over the next few months, I don’t think we are prepared to spend any additional funds beyond what is in the termination account until we see the mission need and potential for transition,” Goldin said in a June 13 interview. 

Goldin said he and senior defense officials intend to make a decision about the future of the X-33 program within a few months. 

The debate over the future of the X-33 has attracted the attention of influential members of the U.S. Congress. In a May 30 letter sent to Air Force Chief of Staff Gen. Michael Ryan, then-Senate Majority Leader Trent Lott (R-Miss.) urged the service to adopt the program. Lott became the Senate minority leader when his party lost control of the Senate in early June. 

The letter, obtained by Space News, was co-signed by a number of prominent Senate Republicans and Democrats. 

“It would be extremely unfortunate to lose the many advantages the X-33 offers,” the letter said. “Yet, without an expressed interest by senior Air Force leadership in the X-33 program, NASA intends to dismantle the program in the very near future. The significant progress made in this program will be lost to the country.”

Meanwhile, maintaining the X-33 program in its present holding pattern is not free.

McCollum said Lockheed Martin is incurring the expense of selling the program to the Air Force while NASA is covering the expense of maintaining X-33-related hardware at facilities in California and Mississippi. NASA still has some of the $941 million it pledged to spend on X-33 under a cost-sharing agreement with Lockheed Martin signed in 1996, according to agency and industry officials. 

The X-33 vehicle, which Lockheed Martin officials describe as 75-percent complete, is housed in a Palmdale, Calif., aircraft hangar that is being leased from a Swiss aviation company. The lease expires at the end of the year, McCollum said.