Answers sought for SSBJ questions

Aviation International News » June 2002
October 3, 2007, 5:02 AM

The good news is that a supersonic business jet (SSBJ) is almost inevitable. The not so good news is that it is probably at least a decade away. And securing the funding for research may be as problematic as the noise from any sonic boom.

Northern Virginia-based aviation analyst firm The Teal Group recently said that creating an SSBJ will take considerable effort and some unprecedented industrial partnerships. The first such proposal emerged in the late 1980s as a joint venture among Gulfstream, the Sukhoi Design Bureau, Rolls-Royce and Lyulka.

That ultimately unsuccessful effort was followed in late 1997 by Dassault’s revelation that it was doing preliminary design work on an SSBJ concept. With a synergistic military fighter jet background upon which to draw, the French manufacturer seemed particularly well positioned to bring a supersonic business jet to fruition.

But Dassault shelved its SSBJ project in March 1999, about the time that Boeing began flirting with Sukhoi and Gulfstream briefly hooked up with the Lockheed Skunk Works in the hopes of making this dream a reality. Teal said the Boeing/Sukhoi effort would have presented a great opportunity for a transatlantic joint venture with Dassault, but the French firm evoked little interest.

Gulfstream is now owned by General Dynamics, which developed the F-16 and last year acquired the former Galaxy Aerospace, whose Astra SPX and Galaxy business jets are built by Israel Aircraft Industries. Some industry observers already have suggested that IAI might become a technological partner with Gulfstream to develop an SSBJ.

“I think all of us in the industry know that this would require large investment; therefore, it’s a large risk and several of us would try to do it together,” Gulfstream president Bill Boisture said last month. “But that’s just driven by the imperatives of the business situation.”

He said the Savannah, Ga.-based airframer was “not really” talking with any other manufacturers about an SSBJ, adding, “We are still at the very early stages. We don’t spend a lot of time comparing notes.”

The Teal Group noted that an SSBJ would allow private aviation to retake the high ground in terms of travel time and prestige, and it predicted that regardless of whether Boeing builds the almost super-Sonic Cruiser, it is “unlikely that we won’t have an SSBJ in another 20 years.”

To bolster the argument for an SSBJ, the analysts noted that the high-end of the business jet market has exploded–Gulfstream’s IV and V; Dassault’s Falcon 900 and 7X; Bombardier’s Challenger, Global Express and Global 5000; Airbus’ Corporate Jetliner (based on the A319); and Boeing’s Business Jet (based on the 737). Combined, these aircraft types comprise a market worth $50 billion over the next 10 years, Teal estimates.

As these maximum prices of top-of-the-line business jets surged from $24 million to $45 million, Teal said, suddenly a $65- to $70 million SSBJ is a “very reasonable” proposition. Further, it said that large fractional-ownership providers (and perhaps airlines) will also help the SSBJ. “These customers will provide necessary launch orders, probably with considerable risk-sharing money,” Teal added, or large down payments.

NetJets Pledges SSBJ Support
NetJets executive vice president Richard Smith already has visions of supersonic flights between New York City and Palm Beach, Fla., and he is convinced that the next supersonic civil jet should be “reverse-size engineered.” Instead of waiting for technology to build a large SST for the airlines, or even a large-cabin business jet, it should begin as a smaller-cabin SSBJ.

“In the interest of getting the project off the ground, it is not necessary to have existing large-cabin luxury,” he told AIN. “At NetJets, the hottest-selling aircraft is the Cessna Citation X, which has a double-club, eight-passenger midsize cabin.” Smith said the midsize cabin is “very acceptable” to the Citation X NetJets owners, mainly because they are not in it very long.

Smith said a number of existing NetJets owners are interested in an SSBJ, and the fractional provider has met with “any and all parties” that are interested in such a project. The company has had meetings with NASA, Gulfstream, Boeing, Dassault, Rolls-Royce, Pratt & Whitney, General Electric and Lockheed Martin.

“Quite frankly, I told them that NetJets is not really interested in a clone of the Concorde,” he said, meaning an aircraft that can go supersonic over water but not over land. Also, the company is not interested in an SSBJ that is limited to a range of 4,075 nm. “We need an airplane that can go 4,750 nm nonstop, and it must be able to go supersonic over land and water,” Smith explained.

NetJets predicts there will be plenty of interest in trips between New York and Los Angeles, L.A. to Tokyo and New York to Paris. “But if you can’t fly supersonic over land,” Smith said, “it’s not worth developing.” He estimated that NetJets would operate “at least” 50 SSBJs worldwide, at a per-aircraft price in the $80 million range. “And when you get to that type of expense, I think fractional ownership makes more and more sense.”

Smith said that just 2.5 years ago, there was not a lot of serious interest in the concept, but in the past six months there has been a marked increase in this interest. “There are other applications for the airplane,” he continued. “Obviously there is a potential governmental interest, and I think you can say there is probably some military interest.”

According to Smith, there have been theories batted around for decades on an airframe shape that can reduce or eliminate a sonic boom, but they have never been tested and proven. “Until there is some funding to actually conduct in-flight testing of airfoil shapes,” he said, “we will never know. That’s where DARPA [Defense Advanced Research Projects Agency] can really come to the party.”

In late April DARPA selected Lockheed Martin Advanced Development Co. of Palmdale, Calif., and Northrop Grumman of El Segundo, Calif., to head Phase II of its Quiet Supersonic Platform (QSP) program.

They will continue work in the systems studies segment of the QSP program, updating their aircraft designs and technology assessments based on revised program goals, perform validation of their designs, perform utility and cost analysis and develop technology-maturation road maps.

Show Me the Money
Lockheed Martin received more than $2.4 million and Northrop Grumman approximately $2.7 million. In addition, Arizona State University was given $700,000 for Phase II of its project to demonstrate distributed roughness to inhibit crossflow instabilities for natural laminar flow on swept wings, and General Electric of Cincinnati was awarded slightly more than $3 million in Phase II funding last September to conduct advanced propulsion systems studies, mature high-performance nozzle technology and advanced fan technology.

In a separate effort, Northrop Grumman received more than $3.4 million to conduct a flight demonstration of direct sonic boom mitigation using a modified Northrop F-5E fighter. It will be outfitted with a specially designed nose glove to produce a shaped sonic-boom signature on the ground.

The demonstration will include a wind-tunnel test to validate computed sonic-boom signature predictions, safety-of-flight wind-tunnel tests to verify handling qualities of the modified F-5E and finally a series of flight tests to validate the predicted persistence of shaped sonic booms. The program intends to demonstrate for the first time that an appropriately shaped aircraft will produce a mitigated sonic boom.

For Phase II, the QSP program adjusted the system goals to emphasize characteristics that are more relevant to a long-range supersonic military aircraft. The systems studies will focus on the refinement of aircraft designs, the quality of which will depend on the ability of the system integrators to use advanced design methods and tools to update the QSP vehicle concepts developed in Phase I. The vehicles will be optimized to meet revised sonic-boom concepts while maximizing range and payload.

Lockheed Martin and Northrop Grumman will perform trade studies in collaboration with GE to identify desirable propulsion performance, size and weight. Contractors will fabricate and test advanced structural components to failure to validate performance relative to predicted performance. The optimization of swept-wing laminar flow to minimize drag, using real wing configurations, is an important aspect of the Phase II effort, DARPA said.

Northrop Grumman and principal team member Raytheon Aircraft have developed a preferred “dual relevant” concept for the next phase, featuring a “joined wing” or “strut-based wing” configuration. Northrop Grumman QSP chief engineer Steve Komadina said the result is something “we think can be evolved into a strike aircraft or a business jet.”

It is aimed at an approximately Mach 2.2 cruise speed and balanced field length of 7,000 ft, about midway between the military strike requirement and the needs of business jets. It can accommodate either two side-by-side, 27-ft-long weapons bays or a 22-ft passenger cabin.

DARPA awarded the Phase I contracts in fall 2000. Northrop Grumman received a contract for what the aircraft characteristics would be and what it would look like. Last summer it received a follow-up contract to conduct the first flight demonstration of an aircraft with a less intense sonic boom, which will be flown later this year at NASA’s Dryden flight-test center.

“They will fly a regular F-5 and measure the boom and then fly the modified F-5 and measure the boom,” said a Northrop Grumman spokesman. “Our studies show this shaped sonic plume will be noticeably less noisy. As far as we know, this will be the first time a shaped boom has actually been flight tested.”

Under Phase II, one part is for systems studies and technology development, which will validate and demonstrate the concepts defined in the first phase. A second part has Northrop Grumman again working with Raytheon Aircraft on fabrication and testing of a structural component made with an advanced composite core.

Boisture said Gulfstream is continuing with some DARPA-funded studies of the different technology issues that must be addressed before anything is even close to being marketable and operational. “These are small studies that we’re taking a piece at a time,” he told AIN last month. “Much of what we’re doing right now is focused on boom suppression.”

DARPA said a key finding of Phase I was that no single breakthrough technology would enable a QSP-type vehicle. A range of technologies has to be properly integrated to approach the stringent sonic boom and performance goals, it said.
Agreeing that an SSBJ is going to take a while, Boisture said Gulfstream will continue to participate “as we can in what we call the technology building blocks. We have discussions ongoing with several other OEMs with respect to teaming and partnering, but nothing definitive at this point.”

The obstacles to development and entry are so significant, Boisture said, that everyone is slowly working toward them, but nothing is quantified in terms of getting a vehicle in the air or having something to market at this point. He estimated that there might be a partial-scale demonstrator within 10 years.

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