The shrinking capability for flight testing in the U.S.—the jewel in the crown that paved the way for the nation's leading role in global aerospace in the 20th century—is forcing NASA and Air Force planners into a major review aimed at halting the decline.

The action comes as the agency and USAF gird themselves for potential budget cuts that could further threaten existing flight-test capacity. It also follows in the wake of controversial findings from a National Research Council (NRC) report into the state of NASA flight research, the recommendations from which were aired to a broad industry group for the first time at the American Institute of Aeronautics and Astronautics Joint Propulsion Conference in Atlanta.

The growing shortfall in new test assets has been keenly felt by NASA, which has not sponsored a major X-plane for seven years and has seen recent efforts to develop a larger, piloted X-plane rejected on budget grounds. At the same time, even funding for more affordable, small-scale unmanned experimental aircraft has become tighter as pressure grows to trim NASA's already reduced aeronautics allocation.

One solution being studied by the Air Force Research Laboratory (AFRL) to partially cover the gap includes closer collaboration with NASA and the FAA on potential joint flight-test efforts to explore energy-efficient technologies. The search for lower fuel burn is a common goal for commercial and defense communities, and is a top priority for the Pentagon, which wants to dramatically reduce energy consumption across the services. AFRL is keen to study potential flight-test efforts for technology, which could particularly target the Air Force's current use of 2.4 billion gal. of fuel per year. Of this, 64% is consumed by the air mobility fleet, which could be a prime candidate to use the same fuel-saving technology being studied by NASA and the FAA.

William Harrison, AFRL technical adviser for fuels and energy, says the approach includes “formulating an AFRL, NASA, FAA portfolio to divide and conquer, and we've been doing that over the past year.” The scheme includes taking technologies such as laminar flow, low-cost composite structures, advanced engine cycles and alternate fuels, and funneling them into testbed aircraft or applying them to future upgrades.

“There's maybe an opportunity to re-wing and reengine an existing legacy transport aircraft and use that as a demonstrator,” says Harrison. Although no specific aircraft is identified, the most likely candidate for the project is believed to be a Boeing C-17 in the 2017-19 timeframe. The concept is even more intriguing, given that the C-17 fleet is now the largest single consumer of fuel in the Air Force and will be ripe for a life extension until the advent of a C-X family of replacements in the late 2020s or beyond.

However, a more radical concept for testing a wider range of advanced technologies is also being considered, says James Kenyon, associate director of aerospace technology in the Office of the Secretary of Defense. “We are raising the possibility of a larger modular X-plane, inspired by the X-56 idea, which could work.” Nevertheless, several fundamental questions still need to be answered, he cautions. “Is it feasible, will it be cost-effective, how useful will it be—all these are to be determined,” he says.

The X-56A, initially known as the MUTT (Multi-Use Technology Testbed), is being developed by Lockheed Martin for AFRL, which intends to employ it to evaluate technologies for mitigating aerodynamic wing flutter. Supported by NASA, which plans to use the testbed as a long-term research asset after the AFRL work is complete, the X-56A will deliberately explore dangerous parts of the envelope. As this could lead to the destruction of a wing, the X-56A is provided with a ballistic parachute recovery system. It is also uniquely designed with substitute multiple fuselages and wings to enable a rapid return to test.

The X-56A continues the recent trend to smaller, more affordable unmanned X-planes, while the AFRL vision calls for a larger, multirole testbed of the type originally envisioned to evaluate advanced concepts in NASA's Environmentally Responsible Aviation (ERA) program. There were efforts to share the cost of this testbed with other agencies, but the plan was scrapped because of budget restrictions. “We asked for an experimental flight vehicle for ERA, but the Office of Management and Budget (OMB) asked for a 50% cut in our requested funding. Now we have to show the ERA goals without the benefit of an experimental vehicle,” says NASA Aeronautics Research Mission Directorate Deputy Associate Administrator Thomas Irvine.

Because of worries over the way budget cuts were damaging flight-test capabilities, NASA approached the NRC. “We were concerned. Is that skill atrophying to the point where it won't be useful going forward? So we reached out to the [National Academy of Sciences] to help us try to figure out how to reach a healthy level,” he says.

The NRC report, which was briefed to Congress and the OMB, includes recommendations that met with a mixed reaction at NASA. Wes Harris, professor of aeronautics and astronautics at the Massachusetts Institute of Technology and the leader of the report, says the NRC fully backs the continued need for flight testing, despite the growth of simulation and other ground-based test techniques.

“This is a path to, an advocate for, and a champion for aeronautics. It advances technology, increases U.S. competitive advantage, improves the balance of trade, creates more skills and jobs [and] reduces the impact of aviation on the environment. It also improves air safety, and we're interested in being a champion for increased efficiency in flight operations,” says Harris.

Although NASA's request for a report was an unusual task for the academy, he says, a broad team of experts was brought in to “recommend how NASA might maintain a robust flight-research program within defined budget scenarios.”

The NRC recommended that the agency should select a “small number [2-5] of focused, integrated, higher-risk, higher-payoff and interdisciplinary programs.” These could be supported by a set of cost-effective flight-test vehicles, each costing $30-50 million per aircraft over three years. This, says the report, could be done “even within the existing budget” but only if the agency eliminates some smaller programs. “NASA should phase out the majority of its lower-priority aeronautic activities,” it adds, without attempting to identify targets.

The NRC found that although the aeronautics budget has shrunk drastically, to less than $600 million today compared with more than $2 billion in the 1990s, the associated workforce has remained more or less the same. The council also found that aeronautics has “become risk-averse and its projects less ambitious, which suggests a decline in our intent to stretch a bit in flight testing,” says Harris. Other criticisms included an “insufficient strategic direction from NASA headquarters.” There is also a need for more programs that “from Day One include flight research.”

Overall, the NRC found there were too many small projects supported by a constrained budget, and that NASA's level of cooperation with other agencies was limited. It concluded that “systems-level flight research has essentially stopped at NASA.”

Harris says, “Although we talked about a series of midsize projects, we also talked in another recommendation about a grander flagship program, more X-plane like, a truly national program.” One such concept could be aimed at proving low-boom technology as a possible starting point for a supersonic business jet. Harris says NASA “should proceed immediately with an integrated-technology experimental aircraft to validate low-boom acoustic ground signatures and establish a set of quantitive measures of sonic boom overland.” The conquest of the sonic-boom problem, which stands in the way of viable supersonic travel, is “a golden opportunity,” says Harris. “We can take control of this, and we should not let us pass this one by.”

Mark Anderson, director of platform performance technology for Boeing Research and Technology, asserts that U.S. aerospace is “teetering on the brink of being able to do low-boom supersonic flight.” But without NASA, “who is going to take a risk like that? I'm concerned we're backing away from this.”

The report also singled out the agency's ERA effort and recommended that NASA “collaborate with the Defense Department and FAA on a subsonic experimental aircraft that would integrate advanced aerodynamics, structures and engine technology. Hypersonics, which will be effectively dropped under current budget plans (see following article), should also be revived, it says. The agency should “reform” the hypersonic project around a specific goal of developing and demonstrating technology for a vehicle that within 25 years could fly on “point-to-point flights” anywhere on Earth in a few hours. For this effort, NASA should again coordinate with the Defense Advanced Research Projects Agency and other defense organizations. “The committee feels that the whole area of hypersonics will not advance, cannot advance, without flight testing,” says Harris.

Although NASA concurs with the NRC's views on the importance of flight research and the need for greater collaboration, Irvine says the agency “takes exception to the assertion that NASA is not making progress or contributing to advancing the aviation industry.” Furthermore, the agency believes the report is too “vehicle-centric” in recommending the phasing out of low-priority activities to fund “high-risk, high-return, interdisciplinary programs.”

Aurora Flight Sciences CEO John Langford recommends that NASA establish an ongoing, competitive flight-research program modeled on the Discovery and Mars Scout space missions. Pointing to the Sikorsky X-2 as a recent example, he says that “there is plenty of evidence that cutting-edge flight-research programs can be accomplished for around $50 million per project.”