30 Years Before Boom, Sukhoi and Gulfstream Nearly Built a Mach 2 Capable Business Jet

Supersonic civilian jets can be a challenge even for the wealthiest and most well-equipped global superpowers. Only the Concorde has ever been even remotely close to successful. By successful, we mean even made it into service past 12 months.
Sukhoi-Gulfstream S-21 7 photos
Photo: Sukhoi-Gulfstream
Sukhoi-Gulfstream S-21Sukhoi-Gulfstream S-21Sukhoi-Gulfstream S-21Sukhoi-Gulfstream S-21Sukhoi-Gulfstream S-21Sukhoi-Gulfstream S-21
But that didn't stop the Russians from giving it the old college try. Admittedly, with some help from the Americans. In a modern era where collaboration between Russia and the U.S. of any kind sounds preposterous, the Sukhoi-Gulfstream S-21 proved this is only the case under the reign of Vladimir Putin. Under the old regimes of Gorbachev and Yeltsin, things weren't so cut and dry.

But to understand why two seemingly unrelated international aerospace firms teamed up to design the world's fastest business jet, we need to familiarize ourselves with both groups. As far as Sukhoi is concerned, you'll find their origins are quite different from that of Gulfrtream's.

Founded in 1939 by Pavel Sukhoi, Sukhoi is and always has been a military aerospace design bureau for the Russian/Soviet state first and a civilian manufacturer a very distant second. Sukhoi's most famous creation at this time was no doubt the Su-47 Berkut, a forward-wing-sweep jet fighter concept that proved Russia could indeed field a fifth-generation fighter.

Sukhoi had a breadth of experience in the fields most important to developing civilian Supersonic Transports (SSTs). Key areas like expertise in high-strength composite metals, servicing afterburning turbojets, variable-geometry wings, and stringent build-schedules fitting of a military manufacturer were no doubt attractive attributes for the other corporate partner in this whole affair.

Sukhoi\-Gulfstream S\-21
Photo: Sukhoi-Gulfstream
Gulfstream Aerospace may have its origins as a civilian project for Grumman, a military contractor. But unlike Sukhoi, Gulfstream's sights have always been firmly set on the civilian sector. Since the company's split from Grumman and its move from Bethpage, New York to Savannah, Georgia, Gulfstream's become known for one thing and one thing alone. Building some of the most expensive, most efficient, and best-equipped private business jets in the Western Hemisphere.

With this in mind, it's easy to understand how the strengths of both Gulfstream and Sukhoi could compensate for perceived weaknesses on the parts of both parties. Gulfstream has longed to apply its signature private business jet approach to a supersonic transport application since at least the late 1980s.

Supersonic-capable airframes are something that Sukhoi, makers of nearly every great Soviet jet fighter that didn't have MiG in its name, was well suited to build. Gulfstream's trademark eye for design would have no doubt made for a cabin and cockpit that pilots and passengers alike would've thoroughly enjoyed sitting in had the thing ever made it into production.

The joint project was dubbed the Sukhoi-Gulfstream S-21. It began in the early 1990s with an estimated development cycle from blueprints to operations of at least 20 years. This conservative development schedule ensured that Sukhoi-Gulfstream levied no false promises or exaggerated claims and allowed them to take their time getting it right.

Sukhoi\-Gulfstream S\-21
Photo: Sukhoi-Gulfstream
There were more than a few pre-existing difficulties on the parts of both companies. Private business jets weren't yet fixtures of modern American skies the way they are today before their .com-driven renaissance in the late 90s and early 2000s. Less than 2,900 business-class private jets were registered in the United States in 1986, according to a 1990 report by the New York Times.

That number increased to just over 3,000 by 1989. But before bubble brought Gulfstream new clientele, the world's first business jet SST was at least an excellent marketing exercise. Meanwhile, Sukhoi was contending with the government in charge of its oversight, going you-know-what's up in spectacular fashion.

As if to add another layer of intrigue to this curious design post-mortem. Most of the world at large was introduced to the Sukhoi-Gulfstream S-21 via this NY Times article. Interestingly, its publication predates the dissolution of the Soviet Union by just over a year. It was as if even Sukhoi knew Mr. Gorbachev's goose was cooked by that point.

There was more than one redesign between the 1990s and the early 2010s. But the basic concept called for a roughly 38-meter (124 ft) long fuselage with a 20-meter (65 ft 5in) wingspan and variable geometry wings that could tilt between 32 and 68 degrees depending on the speed.

Sukhoi\-Gulfstream S\-21
Photo: Sukhoi
For comparison, the Grumman F-14 Tomcat also had a maximum wing geometry of 68 degrees with a minimum sweep of 20 degrees in high-speed flight. Can you tell that half of the S-21's team primarily built fighter jets yet? If not, then the triple Aviadvigatel D-21A1 turbofan cranking out 16,535 lbf (73.55 kN) of thrust each surely would.

Despite a projected fully-loaded curb weight of around 51,800 kg (114,200 lbs), it was theoretically powerful enough to push the S-21 past twice the speed of sound with a maximum high-subsonic range of 4,000 nautical miles (4,600 mi, 7,403 km) if flown with a degree of restraint. With Gulfstream slated to handle the interior cabin while Sukhoi handled the airframe, it did at least look like a tempting design.

That's especially true if you were one of the few business people who could afford a $25 million MSRP and $2,500 per hour to operate Gulfstream G-IV back in the early 90s. But as should be clear by this stage, the market for such a machine was practically puny compared to just 20 years later and even tinier compared to the present day.

If even commercial-sized SST airliners like Concorde struggled to be profitable, Gulfstream reckoned, there was no way it would make sense as a business jet. At some undefined point between the mid-to-late 1990s and the 2010s, Gulfstream lost its passion for supersonic business travel it'd harbored since the previous decade and doubled down on the slowly emerging subsonic business jet market.

Sukhoi\-Gulfstream S\-21
Photo: Sukhoi-Gulfstream
Considering there are now 14,632 business jets in American hangars as of August 2022, this turned out to be the right move for Gulfstream. As for Sukhoi, their team retained the design blueprints for the S-21 and set off a relentless, 20-year-long funds campaign.

Correspondence with the French aviation firm Dassault and even the Chinese Communist Party failed to net the S-21 any funding by the 2012 to 2025 design study window. Since then, the project has been declared de-fact deceased. Meanwhile, Sukhoi's exploits as the designers of the PAK-FA, Russia's first true Gen-V fighter, must make the sting of a failed SST 30 years ago feel considerably more numb.

Meanwhile, the S-21's failure didn't inhibit other startup companies from attempting more or less the same idea. At this very moment, an American firm called Boom Technologies is developing a tri-jet, Mach 2-capable supersonic business jet called the XB-1 as a tech demonstration for their Overture SST airliner. Does any of that sound familiar? It should if you made it this far.
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