Reno, Nev.-based Aerion is releasing results from recent flight tests of a natural laminar flow (NLF) wing test article this week here in Las Vegas, while the company continues to work to have its supersonic business jet enter service in 2020. The goal of these tests was to measure “real-world robustness” of supersonic NLF, which is a key technology for the Aerion SSBJ, in regards to surface quality and manufacturing tolerances.
Conducted from January 31 to June 20 at NASA Dryden Flight Research Center, the 11 test flights recorded data from a 40- by 80-inch phase-two test article mounted on the belly of a NASA F-15B research jet that was flown at speeds up to Mach 2.0. According to Aerion, the tests confirmed that formulas for “predicting surface imperfection effects on laminar-turbulent transition, previously validated for subsonic flows, now can be extended to transonic and supersonic regimes.”
In less technical terms, “The robustness that we had hoped for and expected on the wing test article was there,” Aerion chief technology officer and director Richard Tracy told AIN. “Flow over a NLF wing can indeed withstand a lot when it comes to wing surface roughness. The height to trip the boundary layer was higher than we expected.”
Aerion used various methods to create roughness over the wing, including putting one-sixteenth-inch dots of tape at varying distances from the leading edge. The company also applied patches of car-wrap film in some tests to achieve a rough surface with different thicknesses, Tracy said.
Despite the roughness, the flow over the wing test article in the transonic region (Mach 0.9 to Mach 1.0) was “pristine,” company test manager Jason Matisheck said. “As you go faster into the supersonic region, laminar flow gets even better.”
SSBJ Engine Revisited
At the EBACE show earlier this year, Tracy told AIN that Aerion was “revisiting” the powerplant for its SSBJ, citing the previously selected Pratt & Whitney JT8D-219’s inability to meet upcoming Stage 5 noise requirements. “The timing is right in the development schedule to do this,” he said. “And a new engine will give us more growth options for follow-on models. We’ve always said we are planning a family of aircraft. We see this as a step forward that builds on everything we’ve done to date.”
He noted that discussions with engine manufacturers, which started in May, are still ongoing. “There’s really no off-the-shelf engine available for the Aerion SSBJ, so we’re looking at several existing cores and then will have one of them customized for our airplane,” Tracy said. “There are several good choices for engines, and right now our big focus is on the powerplant.”
An engine swap also allows the company to reconsider the aircraft’s specifications, with the most likely changes being more range than the originally specified 4,000 nm and a wider cross section. But a cruise speed higher than the planned Mach 1.6 isn’t happening, Tracy said, since higher speeds would translate into higher skin temperatures that require use of exotic materials.
Aerion CEO Doug Nichols said the plan is to select an engine core and manufacturer by the end of next year, as well as choose an OEM partner by mid-2015. The OEM partner would then build an SSBJ prototype, which Aerion expects to fly in 2018, he said. A planned two-year flight-test program would then pave the way for certification in 2020, Nichols added.
Because the range and size of Aerion’s SSBJ could increase under the “refreshed configuration,” Nichols said, “then the value and price point will likely rise” above the previous estimate of $80 million (2007 $). Aerion won’t have any new price estimate available until after an engine is selected and the updated configuration is frozen, he noted.