As two little-known companies refine their designs for a supersonic business jet, bigger manufacturers are joining the race for speed
With none of the hyperbole that surrounded the endof civil supersonic travel with Concorde's retirement in 2003, industry is quietly and cautiously laying the groundwork for the next generation. Technology studies and demonstrator designs are under way that could lead to development of small commercial supersonic transports in the next decade. But with two companies having declared their hands, the race is already on.
Since unveiling rival supersonic business jet (SSBJ) designs at last October's National Business Aviation Association convention, unknowns Aerion and Supersonic Aerospace International (SAI) have kept a low profile. But both are refining their designs while moving towards assembling international industrial teams to make their SSBJs a reality.
Aerion is due to give an update at the Paris air show. Backed by US billionaire Robert Bass, the Reno, Nevada-based company is in windtunnel testing as it nears the end of Cycle 2 of Phase 1, and a decision on whether to proceed to the next stage. The next step is to begin signing up risk-sharing partners.
Aerion believes its SSBJ could enter service first, as early as 2011, because it does not require a regulation change to allow supersonic flight over land. Conceived around patented supersonic natural laminar-flow aerodynamics, the aircraft is designed to cruise over water at Mach 1.6, then drop to a boomless M0.98 over land without sacrificing range. It will use existing engines. In Cycle 1, completed last July, Pratt & Whitney completed a preliminary durability study on its JT8D-219 turbofan for Aerion. "We did not see anything that would not allow its use," says Peter Robertson, advanced commercial engines programme manager. "There were some areas of concern, and we are now doing the next level of analysis on those."
Aerion's SSBJ is not a low-boom design, but founder Richard Tracy was recently granted a patent for what may be a follow-on aircraft that would allow boom mitigation through airframe shaping. This design locates the unswept supersonic laminar-flow wing at the rear, balanced by a highly swept canard foreplane mounted on a narrow, elogated forward fuselage.
SAI is in Phase 2 of its SSBJ programme, refining the airframe and systems designs and working on certification and manufacturing plans. The two-year phase began early this year, with the work performed by Lockheed Martin's Skunk Works and funded by money bequeathed by late Gulfstream founder Allen Paulson.
"By the end of Phase 2, we will have a complete plan for certification and manufacturing," says SAI chief executive Michael Paulson. The company also hopes to have its international industrial team on board by the time Phase 2 is completed late next year. Lockheed Martin is already working with potential suppliers on systems definition, says Paulson.
SAI spent $25 million on Phase 1, and Phase 2 is budgeted at $50 million. "The work being done at Skunk Works is fully funded by SAI," says Paulson, but the plan to bring in outside partners and funding for Phase 2 "is going well". The company intends to select an engine supplier at the end of Phase 2, ready to move into Phase 3 – detailed design involving industrial partners. First flight is scheduled for 2010-11, and certification for 2012. Although the M1.6-1.8 QSST is a low-boom design, SAI does not expect approval for unrestricted supersonic flight at entry into service. "We will not get supersonic over land out of the box," says Paulson. "That will be a follow-on to the initial certification and will involve a lot of testing." Based on simulations, the sonic boom is "insignificant", he says, and cannot be heard above "normal everyday noise".
The Skunk Works is refining the design to reduce drag and increase range, now 7,400km (4,000nm), to the 8,000-8,100km SAI's market studies indicate to be ideal. Other changes are subtle, but include 5% more internal volume and two additional cabin windows, making a total of six.
Big aircraft
For a business jet, the QSST is a big aircraft: about 40m (130ft) long with a 20m wingspan and 69.5t maximum take-off weight. It is designed to seat eight to 12 passengers, but Paulson says SAI is studying a 30- to 40-seat, 5,500-6,300km-range version for airline use. "We are now allocating resources to a quick feasibility study to see if we can use the current aircraft as a platform for a stretched version."
While Aerion and SAI are both aiming for early next decade, established business jet manufacturers do not expect to begin developing an SSBJ before 2010. Europe is just starting a four-year study of the key technologies for a small commercial supersonic transport, while US industry is working to secure NASA funding for low-boom demonstrator to fly in 2008.
Dassault is leading a team of 37 partners in the European Commission-funded High Speed Aircraft (HISAC) study programme, which aims to overcome the environment constraints on developing an economically viable small supersonic aircraft – addressing noise, pollution and efficiency by pooling advances in structures, propulsion and aerodynamics using a technique known as multidisciplinary optimisation. The goals are ambitious: airport noise 10dB lower than Stage 4; NOx emissions less than 10g/kg near-term and below 5g/kg long-term; a 50% cut in CO2 emissions; and "acceptable" boom.
The team will study three configurations for a 45-65t aircraft capable of speeds of M0.95-1.8 and ranges of 6,500-8,300km – low noise/drag, low boom and laminar flow – comparing aircraft weight, cabin size, cruise Mach, range, field performance, noise, emissions, sonic boom and efficiency. "We will use the different designs to integrate the technologies, select the best one, and define what is achievable in performance, boom and noise together," says Olivier Villa, Dassault senior vice-president, civil aircraft.
HISAC is just a study, and Villa does not expect development of a supersonic business jet to begin before the end of the decade. This is similar to the timescale foreseen by US industry as it works to persuade NASA to fund an X-plane programme to flight-demonstrate the low sonic boom technology they believe is essential for any future supersonic aircraft. Their task has been made more difficult by deep cuts in aeronautics research funding in NASA's FY2006 budget, but a plan to build and fly a sub-scale low-boom demonstrator remains intact for now.
Encouraged by the success of the Shaped Sonic Boom Demonstrator (SSBD) – a modified Northrop F-5 that proved airframe shaping can reduce the sonic-boom overpressure – US airframe and engine manufacturers formed the Supersonic Cruise Industry Alliance last July. The group comprises Boeing, Cessna, Gulfstream, Lockheed Martin, Northrop Grumman and Raytheon, plus General Electric, Pratt & Whitney and Rolls-Royce's Allison Advanced Development unit. The 10th member is business jet fractional ownership company NetJets.
Alliance charter
The alliance's charter is to "enable quiet, safe, affordable, environmentally acceptable supersonic flight over land within 10 years", says Eric Brachhausen, vice-president of American Technology Alliances (AmTech). The industry group is working with NASA, the US Federal Aviation Administration and Department of Defense under the Super 10 Alliance, assisted by AmTech – a non-profit organisation facilitating collaboration by the industry consortium and the larger alliance.
Brachhausen says the industry alliance made a presentation to NASA last October, then submitted a detailed proposal for a flight demonstrator programme in December. Industry proposed a step-by-step approach, starting small but leading to integration of the technologies required for quiet supersonic flight, including sonic-boom mitigation, propulsion integration, aerodynamics, structures and systems.
But there was a hitch – NASA could not afford the $1 billion price-tag on the proposed programme. The agency asked the alliance to rescope the project, says Brachhausen, focusing it on a breakthrough consistent with NASA's desire "to produce outcomes, not output". By January, the industry group had put together a proposal for a small-scale low-boom demonstrator, and the quiet supersonic project was one of only four in NASA's FY2006 request in February.
The alliance members are now working on a NASA-funded concept exploration study to flesh out a more modest, $150 million programme to fly a small manned X-plane that would demonstrate sonic boom can be reduced to an acceptable level by shaping the entire airframe, not just the forward fuselage as was the case with the F-5 SSBD. The goal is to have the demonstrator flying by early 2008.
Robertson says the alliance's timetable is set by the need to have the public acceptance data ready for presentation to the 2010 meeting of the International Civil Aviation Organisation's Committee on Aviation Environmental Protection (CAEP), which develops standards for aircraft noise and emissions. CAEP received its first formal briefing on quiet supersonic flight recently when Gulfstream made a preliminary presentation of the Super 10 alliance's timetable and objectives. "They [CAEP] are beginning to think through the issues," says Brachhausen.
Nothing is yet certain, as NASA faces a tough budget battle this year while undergoing major internal restructuring. How a quiet supersonic demonstrator will be funded, what shape the programme will take, the design of the demonstrator, and how much work will be done by NASA and how much by industry are all issues to be resolved. If the effort fails, the manufacturers have other plans, says Roberston. For some, those plans may include co-operating with Aerion or SAI.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International
