Procurement: Scramjet Salvation


February 27, 2021: In a rare event, a new Russian warship entered service more or less on schedule. The first of the new Gremyashchiy class corvettes was accepted by the navy in 2020, as planned. Construction of this ship began in 2011 at the Amur shipyards in the Pacific coast. The ship was launched six years later in mid-2017. Gremyashchiy was completed in early 2019 and began sea trials that revealed no major problems that might have delayed entering service for years, as has been the case with some other new ships. The Gremyashchiy sea trials were extensive and intense, ending with an extended cruise to northwest Russia where it carried out exercises in the White Sea. Gremyashchiy then travelled south to the Baltic Sea where it will be based. While it was initially hoped that Gremyashchiy would enter service at the end of 2019 but sea trials took longer because the ship was using engines from a new supplier, an unfortunate side-effect of the Russian 2014 invasion of Ukraine.

There are currently plans for six Gremyashchiy (Project 20385) class corvettes, with some built at a shipyard in northwest Russia. Displacing 2,500 tons, Gremyashchiys have a top speed of 50 kilometers an hour, a crew of 100, endurance of two weeks and a range (without refueling) of 7,400 kilometers. Armament consists of one 100mm gun, two AK-630 autocannon for close-in defense against missiles and small craft, eight VLS (Vertical Launch System) cells for Kalibr or Zircon anti-ship missiles plus sixteen smaller VLS cells for Redult short-range anti-aircraft missiles. Here are also eight torpedo tubes for lightweight 330mm anti-submarine torpedoes and two pedestals mounted 14.5mm machine-guns. There is a landing pad and hangar for a helicopter.

The first Gremyashchiy was delayed four years because a Russian firm had to design and build a new engine. These corvettes were originally designed to have German engines. That was no longer possible after 2014 because of Ukraine-related sanctions. A capable Russian manufacturer had to be found and that took time. The new Russian maritime diesel engines for the corvettes required more time at sea during sea trials to ensure that the new engines were as reliable and durable as the ones built in Germany.

Gremyashchiy complements the slightly smaller Steregushchiy (Project 20380) class corvettes. Six of these are in service and six more are being built with the ultimate goal of having 24 of them. With access to resupply ports or an accompanying replenishment ships these corvettes can travel to anywhere on the planet.

These corvettes are replacing larger Cold War era frigates and destroyers that Russia can no longer afford to build or operate. Russia has been successful at designing and building these new, smaller warships. For example, at the end of 2018 the Russian Navy achieved a rare feat, it put into service the first of two classes of new warships and did it on time. The first of 22 Karakurt (Project 22800) Corvettes entered service in the Baltic Sea. Nine more are in various states of construction in three shipyards. This is a new type of coastal corvette that is more capable on the open seas. Some of them are being built in the Crimean shipyards Russia acquired in 2014 when they basically took Crimea from Ukraine. Russia has been building more of the smaller corvette-type ships since the 1990s for a number of reasons. First, the Russian shipyards have proved more effective in building these small (under 1,000 tons) ships. Then there is a great need for heavily armed corvettes to serve as low-cost patrol vessels that can handle just about anything they run into during coastal patrols and can even be useful in wartime. Finally, there is a growing export market for this type of ship.

The Russian navy, because of budget cuts, has suspended or canceled work on many new subs and large surface ships. That enables the Navy to apply all its procurement efforts to obtaining smaller ships on budget and on time. Not only are the smaller ships cheaper but they can be built quickly and are easier to monitor for quality control. The shipyards producing these smaller ships know they are fortunate because so many other years have had construction contracts canceled or suspended.

While the first Gremyashchiy was armed with the widely used Kalibur missile, in late 2019 it was announced that Kalibur would be replaced in the corvette with a radical new kind of anti-ship missile, one employing a scramjet engine. This 3M22 Zircon missile would be the first operational cruise missile using scramjet propulsion. It is not certain that the Zircon is really operational and works reliably. To make that happen Russia would have had to overcome some formidable technical problems with regard to design and manufacturing of such a missile. Scramjet tech has been around for decades but the problem has always been controlling a scramjet propelled missile moving at over 900 meters a second. That’s faster than most rifle bullets and a scramjet moves at more than twice that speed, as in up to 6,000 kilometers an hour.

The specs for Zircon sound like a scramjet weapon. It is a two-stage missile with the first stage using a rocket to get the missile up to a high enough speed (at least 3,000 kilometers an hour) for the scramjet to work. Once that speed is achieved the scramjet takes over for the last minutes of flight. Despite the high speed the Zircon must remain very maneuverable to hit the target ship. Description of the Zircon have lacked a lot of detail but the missile is fired from the same type of VLS cell used by the Kalibr cruise missile, which is similar to the American Tomahawk. In theory, a workable scramjet missile could fit in the VLS cell. Zircon is described as having a max range of up to 2,000 kilometers and a 300 kg (660 pound) warhead. Even without a warhead exploding, getting hit by a Zircon, traveling twice as fast as a rifle bullet, would create devastating impact damage on a ship.

What makes scramjets work is the compression of the incoming air, without the use of a fan system (as in conventional jet engines). But while scramjets have been in development for half a century, the lack of adequate materials to handle the high heat and pressure as well as adequate design tools, frustrated attempts to build workable, and reliable scramjets. Scramjets have few moving parts but must cope with very extreme conditions and the design challenges have proved very frustrating.

The materials problems have been overcome. The most recent documented (made public) scramjet program was the American the X-51A Waverider project that was halted in 2013 but recently resumed. In the past the main problem with X-51A was that it could not be made reliable enough. The X-51 tests, like all previous ones, ended with the aircraft crashing. The next step was to get longer hypersonic engine use, de-acceleration, and landing via parachute (and eventually an auxiliary engine.) A 2010 flight test had the 8 meter (36 foot) long, cruise missile-like X-51 aircraft boosted to 3,300 kilometers an hour, using a solid-fuel rocket, at which point the scramjet engine took over, and successfully operated for over two minutes, achieving speeds of nearly 6,000 kilometers an hour. This was the longest a scramjet had ever operated. The previous best was ten seconds. By 2013 the 4th test got the liquid fuel engine going for five minutes. Going beyond the 2013 test proved too expensive and time consuming to continue when there were cheaper alternatives available, and these depended more on getting into orbit and letting gravity provide and maintain the high speed. Russia, China and India (which collaborated with Russia on the Brahmos missile) have all said future models of some existing missiles (like Brahmos) would have a scramjet second stage. No one has yet delivered a verifiable working scramjet missile but Russia has revealed several successful tests of the Zircon and, if the missile is installed and used in ships like the Gremyashchiy, the new hypersonic missile will be considered a success. X-51 is supposed to be ready for service by 2025.


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