Projet SSBJ Aerion

[Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] have begun to hone their designs for a supersonic business jet (SSBJ), reigniting aspirations for a programme launch or demonstrator build in the near rather than far term.

Pres Henne, Gulfstream's senior vice-president of programmes, has confirmed that the company "recently" tested a
supersonic nacelle design on one engine of a [Vous devez être inscrit et connecté pour voir ce lien]-powered Gulfstream IV on the ground.

The static run of a full-scale nacelle installation successfully proved that the sharp-lipped inlet, a design necessity, would not cause stability issues for the engine's fan by distorting the input flow.

Initial indications are positive that the Tay 651 and nacelle combination "would be suitable for an experimental vehicle", says Henne, adding, "however we are not planning to [build a supersonic business jet demonstrator] at this
time".

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The static engine test is one in a growing checklist of tests that encompass the tip-to-tail needs for an SSBJ, suggesting that the Savannah-based company is more serious about the project than it publicly admits.

Along with nose-extendable supersonic spike tests with NASA, Gulfstream has tested external vision systems for zero-forward visibility cockpits and is working on advanced composite design
processes for wings and fuselages.

Accompanying the technology is the regulatory and public acceptance angle, which Gulfstream is working through the International Civil Aviation Organisation, the US Federal Aviation Administration and NASA.

For the inlet, NASA is taking the next step with a series of supersonic windtunnel tests on a scaled model of the inlet in the Glenn Research Centre's 2.4-1.8m (8-6ft) facility.

The model, referred to by NASA as an isentropic relaxed compression inlet, includes a series of curved vanes used to
channel the bypass air.

Henne says Gulfstream has been performing preliminary designs that are "getting real close" to all of the requirements for an aircraft to meet perceived noise level of 70dB (70PLdB) while flying supersonic over land, a practice banned in Europe, the USA and elsewhere. The noise threshold, which Gulfstream and NASA came to independently, can be compared to "closing a good car door or a refrigerator", says Henne.

Meanwhile, ICAO is addressing the possibility of setting a threshold noise level for such flights through its committee.

The nacelle design, although not revealed, could be similar to a US patent that Gulfstream applied for in February.

With the proposed nacelle, the patent states that an engine with 15,000lb maximum take-off thrust (67kN) and bypass ratio of 3:1 could power an SSBJ at a cruise speed of Mach 1.7.

Those thrust and bypass characteristics closely match those of the Tay 651.

Las Vegas-based Aerion too is focusing on nacelle characteristics in forthcoming windtunnel tests to check changes made during a series of engine nozzle noise screening tests more than a year ago, says Richard Tracy, director and chief technology officer for Aerion.