Lockheed Martin believes the next generation, high-altitude intelligence, surveillance and reconnaissance (ISR) platform should be both survivable and affordable. With this in mind, the company has designed its proposed U-2 replacement—the TR-X—to be a low observable, high-flying unmanned aircraft that reuses the U-2’s engine and accommodates current or future sensors for ISR or other missions.

As envisioned, the TR-X “really merges the capabilities of U-2” and the U.S. Air Force’s other high-altitude ISR platform, the unmanned RQ-4B Global Hawk, “in a very affordable way,” said Scott Winstead, Lockheed Martin’s U-2 business development manager. “With the U-2 fleet and the Global Hawk fleet, they’ve got a high-altitude ISR capacity that they’ve become comfortable with. If you take the U-2 away, that capacity drops to less than half. What we’re offering is something to get beyond this Global Hawk/U-2 issue.”

Lockheed Martin proposes a 10-year program that would deliver 30 aircraft; if it were contained in the Department of Defense program objective memorandum for Fiscal Year 2020, the TR-X (meaning “tactical reconnaissance”) would begin replacing the current high-altitude ISR fleet in the 2030 time frame, Winstead said. It would first replace the aging U-2, which the Air Force currently plans to retire in 2019.

The company revealed plans for the TR-X at the Air Force Association Air & Space Conference last September, and provided an artist’s impression showing an aircraft with swept wings, top-mounted engine inlet and canted, V-shaped empennage. Its Skunk Works advanced development unit has since achieved “higher fidelity” of the TR-X design, but has decided not to release any images, Winstead said.

Nevertheless, at Lockheed Martin’s annual media day on March 15, Winstead filled in more details on the TR-X, which he confirmed will be unmanned and air refuelable. The aircraft’s maximum takeoff weight will be around 54,000 pounds, more than the U-2 at 40,000 pounds and the Global Hawk at 32,250, with a 5,000-pound payload capacity. It will have a single engine—the same General Electric F118-101 turbofan that powers the U-2, but rated at maximum 19,000-pound thrust. (The U-2’s engine was derated to 17,000 pounds.) It will also use the same 45 kVA generator as the U-2, but with design space for an expansion to 65- or 75 kVAs, providing even more power for its radar or other mission equipment such as a high-energy laser or communications relay, Winstead said.

With a single engine, the TR-X will be able to fly to 70,000 feet—77,000 feet was determined as the optimal altitude, but that would require two engines, Winstead said. The aircraft will have the same 130-foot wingspan as the Global Hawk to prevent basing issues with existing hangars. It will have a newly designed, straight wing, which is not characteristic of a stealth aircraft, complemented by “low-observable (LO) shaping.” The LO shaping and electronic countermeasures will be its defense against detection by surface-to-air missile systems.

Winstead described air defenses as a “bubble” that protect an adversary nation from being penetrated by surveillance or other aircraft. The TR-X will provide ISR to the edge of the bubble. “It is survivable; it’s not unnoticeable,” he said. “You’re not going to get enough radar return for a missile to track and destroy you. It’s not designed to go inside the bubble. That’s why it’s so affordable, because you’re looking at a peacetime asset that is going to be out there operating every single day that now has some wartime capability. We’re designing it to compress the bubble as much as possible.”