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It is one of Lockheed Skunk Work's least glamorous projects, and it looks a lot like a Dornier 328JET, otherwise known as a "DoJet," but the X-55 Advanced Composite Cargo Aircraft (ACCA) could give the Boeing-Lockheed consortium a leg up in winning the high-stakes Long Range Strike Bomber tender.
The X-55 ACCA came out of an Air Force Research Lab's program known as the Composite Affordability Initiative. This program would explore building a full-scale certified aircraft via advanced and large-scale composite manufacturing processes.
The X-55 rotates off the runway on its first flight out of Palmdale California's sprawling Plant 42 complex.
Technology applied in the production of the X-55 could not only end up decreasing weight while increasing the strength and raw performance of new aircraft designs, but it could also simplify their construction via drastically cutting down the number of parts used in those designs. Also, most composite structures have a longer life expectancy than metal ones, allowing for better airframe longevity and corrosion-resistance. Finally, by using similar design and fabrication techniques as those utilized on the X-55, timelines from a design's conception to its first flight could also be slashed along with the aircraft's production and sustainment costs.
One thing that makes the ACCA so obscure is that it looks totally unassuming, as its design was borrowed largely from a Dornier 328JET. In fact, a DoJet was used as a donor aircraft for the program. This not only accelerated the program's timeline and lowered its cost, but it also provided a control variable for which the X-55 could be compared to when it was finished.
The standard Dornier 328JET has seen resurgent success as a private corporate shuttle and charter aircraft.
In late 2007, AFRL awarded the ACCA contract to Lockheed Martin, controversially beating out Aurora Flight Services which bid on the project using a Soviet designed Antonov An-72. A comparatively tight budget of $50M was available for the construction and test flying of the X-55. Lockheed Skunk Works, which has made its reputation on doing some pretty amazing things on a limited budget and timeline, ran with the project.
Lockheed took the wings, engines, subsystems and the nose section of the DoJet and built an entirely new fuselage and tail section to attach them to. This new fuselage was two and a half feet wider, featured a drop-down rear ramp and was able to accept military standard 463L cargo pallets. Advanced composites were used in its design that would allow for an "out of autoclave" curing process that occurred at lower temperatures and pressures than what traditional "in-autoclave" composite curing processes demand. These cutting-edge techniques make it possible for large, single-piece composite structures to be built. Other techniques pioneered via the rapid prototyping revolutions of the last decade and a half were also used on the aircraft to speed up its construction and minimize cost.
The X-55's huge parts were baked in room-sized, low-temp ovens and the design excluded traditional rivets and fasteners. Instead, the large canoe-like fuselage components (upper and lower) were bonded to a circular frame. The aircraft's large composite parts were made out of a sandwiched structure consisting of a carbon fiber skin with a nomex core. The whole affair was highly experimental, and the project was delayed when the first main fuselage section failed to cure properly.
All said and done, the X-55 had eliminated 90% of the Dornier 328JET's parts. Traditionally, the DoJet, which is made primarily of aluminum alloys, would have over 3,000 metallic parts and just over 30,000 individual fasteners. The X-55 had just 300 parts and less than 4,000 fasteners. These metrics alone made the X-55 a huge success even before it ever flew, which it did for the first time on June 2nd, 2009.
Since the construction of the X-55 was a huge experiment, the aircraft had a fairly short flight-test schedule of around twenty flights. During those flights the aircraft's 600 onboard sensors measured loads and pilots validated the aircraft's targeted performance. In the end, the X-55 was a huge success and broke new boundaries when it came to simplifying aircraft designs, speeding up their construction, and cutting costs while still enhancing raw performance.
Fast-forward five years to the super high-stakes Long Range Strike Bomber bid that pits Northrop Grumman against a Boeing-Lockheed team, one that is more about controlling cost than providing exotic out-of-the-box performance and capability. The USAF knows full well that the program's biggest vulnerability is its somewhat optimistic $550M per-aircraft price tag. Faltering big-budget defense programs like the F-35 and shrinking defense budgets have made any substantial price increases a potential program-killer for the LRS-B, as Congress and the war-weary public are sick of bait-and-switch, gold-plated defense programs. Additionally, the B-2's sad history of shrinking production numbers and ballooning costs are still burned into the psyches of the Pentagon's leadership. It was and still remains the Pentagon definition of a procurement "death spiral."
As a result of these factors, USAF program managers have already forgone requiring cutting edge subsystems and sensors in the initial LRS-B design, instead opting for mature systems or ones already deep into their development cycle, in hopes of lowering risk and cost. This tactic is offset by building the new stealth bomber with modularity in mind so that its systems can be easily upgraded down the road as funds become available.
Because the USAF has foregone making the LRS-B's guts 'bleeding edge,' the aircraft's structure, which is so critical for an advanced stealth aircraft that needs to have broad-band low observability in order to evade threats for decades to come, is left up for grabs as a place where cost and efficiencies can be found. As a result, the team with the most manufacturing experience with large composite structures and their simplified assembly has a very good chance of winning the bid.
When it comes to pedigrees, Boeing has the world's first mostly-composite airliner, the 787 Dreamliner, under its belt and Lockheed has not only the world's first operational stealth flying-wing drone, the RQ-170 Sentinel, which clearly uses many of the advanced composite design processes used in the experimental P.175 Polecat demonstrator, but they also have the X-55 as a feather in their cap. This is in addition to the F-35, F-22 and F/A-18E/F/G, all of which use large composite structures in their designs. Meanwhile, Northrop Grumman has the now quarter century plus-old B-2 Spirit and the RQ-4 Global Hawk, already a decades-old design as well, and possibly a new secret stealth flying wing reconnaissance aircraft dubbed the RQ-180, on their resume.
These are impressive accomplishments, and there are surely other black budget test articles that go along with them, not to mention Northrop Grumman bought famed composite aircraft maker Scaled Composites back in 2007. Nonetheless, Northrop Grumman is facing a tough race as the combined experience of defense prime contractor giants Lockheed Martin and Boeing is surely very attractive to the USAF's bomber buyers. This is especially true considering that the USAF itself chose and worked closely with Lockheed's Skunk Works on the X-55 and knows exactly what they are capable of when it comes to leading-edge composites.
So there you have it, the relatively unpopular and humble X-55, an aircraft that now sits at Blackbird Air Park at Plant 42 in Palmdale, CA, could very well be one of the keys to winning what might be the last manned long-range combat aircraft ever built. A proposition that represents decades work and close to $100B in income.
Not bad for a little $50M plastic "frankenjet" that flew only a handful of times.
From This Obscure Skunk Works Jet May Help Team Win New Stealth Bomber Bid
