By Stephen Trimble & Graham Warwick
Service to emphasise stealth rather than speed for new long-range strike aircraft and declines revolutionary leap
The US Air Force prefers to start fielding a new bomber force by 2018 without making a revolutionary leap in aircraft technology, senior service officials said last week.
The results of a long-awaited analysis of alternatives for a next-generation long-range strike (NGLRS) aircraft point to a manned subsonic bomber with a combat radius beyond 3,700km (2,000nm) and a bomb load from 6,350-12,700kg (14,000-28,000lb), says Maj Gen Mark Matthews, director of plans and programmes at Air Combat Command.
Variable-cycle engines combining high speed with long loiter will not be ready for production before 2018, when the US Air Force's next-generation bomber is supposed to become operational. But research is under way that could produce fuel-efficient higher-bypass embedded engines with stealthy inlets and exhausts.
The US Air Force Research Laboratory will award two contracts in July to begin the Adaptive Versatile Engine Technology (ADVENT) programme leading to ground runs of a large turbofan demonstrator in 2012, but USAF planners have been told that an engine based on ADVENT would not be ready for production until 2018.
Following the demonstration, a two-year technology-maturation phase would be required to meet the full operability and durability requirements, allowing engine development to begin by 2014. "We hope to do that in four years, and be ready to go into production in 2018," says ADVENT programme manager Jeff Stricker. "We are not lined up with long-range strike. That's what we are telling the air force."
Other research under the AFRL-led Versatile Affordable Advanced Turbine Engine programme could produce more fuel-efficient embedded engines with advanced integrated inlets and nozzles, suitable for a stealthy subsonic bomber.
The goal is to emphasise stealthiness rather than speed to fulfil the new bomber's mission to penetrate defended enemy airspace and remain there for long periods.
Completing the analysis allows the USAF to take the next step in the US military's acquisition process: submitting a request for the Joint Staff to approve the requirement for a new bomber fleet, Matthews said during an Air Force Association-hosted event on 1 May. If the Joint Staff approves, the air force can launch a formal acquisition programme, beginning with a science and technology investment phase, followed by a competition to begin full-scale development.
The air force's six-year budget plan includes nearly $335 million in direct funding for an NGLRS programme, plus additional funding in other "technology maturation" programmes, such as engine research.
Matthews said the analysis came to the conclusion of a subsonic aircraft with a pilot on board as a result of a cost/benefit review that showed that configuration offered a "best value" approach. He stressed that the air force is moving forward with the new bomber concept in a "challenging fiscal environment", in which it is already seeking to buy a new tanker, combat search-and-rescue helicopter, satellite communications, space-based surveillance system and the Lockheed Martin F-35 Lightning II.
The preference for a low-speed aircraft is likely to have dismayed air force officials who preferred an approach that balanced the survivability of a high-speed and super-stealthy aircraft with the persistence offered by an optionally manned system.
Retired Gen Gregory Martin, a former commander of Air Force Material Command, criticised the air force's previous stance on science and technology research that emphasised stealth perhaps at the expense of high-speed engine technology.
"Our focus has not given them the option they need to produce something revolutionary or very, very more advanced than what we have today," he said.
Although the new bomber force will be fielded as a manned system, the USAF has a broader vision for the fleet that includes adding autonomous capabilities. The 2006 Quadrennial Defense Review calls on the air force to shift 45% of its long-range strike fleet to unmanned systems after 2018.
"The air force has a commitment to unmanned systems," Matthews said. "We envision a family of [NGLRS] systems in the future, of which a component will be unmanned."