July 21, 2012

RATTLRS Supersonic Cruise Concept - a BrahMos Beater?

Artist's mockup of the jet powered supersonic missile concept dubbed Revolutionary Approach To Time Critical Long Range Strike (RATTLRS)
My post Hypersonic Missile Research and Doctrine of October 26, 2008 touched on the major heating problems of hypersonic missile flight above Mach 4. This may not be solved for 20 years.

There is also a propulsion problem - in the thick atmosphere there is currently a tradeoff between speed and range. The premier supersonic missile, the Indian-Russian BrahMos, may be able to travel up to Mach 2.8 but its range is probably less than 300km due to its heavy powerplant. This is a solid-propellant rocket for initial acceleration and a liquid-fueled ramjet for sustained flight.

In recognition of hypersonic heat and range problems the US-UK RATTLRS project has adopted an evolutionary approach - high supersonic speed (between Mach 3 and 4) using a single jet engine - rather than hypersonic speed with a two-stage rocket/ramjet (or scramjet) combination.
Simplicity is in the single stage and travelling within the bounds of the heat tolerance of airframe materials.
Wiki provides the following:

"The Lockheed Martin RATTLRS (Revolutionary Approach To Time Critical Long Range Strike) is an advanced cruise missile concept demonstration funded by the US Navy with the view to develop technologies that would then be used to develop a successor to the BGM-109 Tomahawk.

Lockheed’s Skunk Works is prime contractor, while Rolls Royce Liberty Worksis designing the YJ102R high-Mach turbine engine. The missile's airframe is similar in size and shape to the engine nacelle of the SR-71
Popular Mechanics says about the RATTLRS YJ102R turbine engine (probably a mockup above) it "might be the most powerful turbojet on the planet—at least by weight. It’s barely bigger than two breadboxes."

Janes provides details of the requirement and thinking behind super-hyper sonic missile systems.

"The US has been examining a range of very high-speed strike weapon concepts for a number of years. These weapons, both sea- and air-launched, have been drawn up for use against mobile and/or time-critical targets, along with hardened and buried targets. In all cases the weapons rely on the kinetic effects of a ramjet powerplant to attain the velocities needed to be effective against such target sets.

The supporters of these 'leap ahead' weapons point to their combination of range, speed and payload as a much needed way to provide the increased lethality required to defeat hardened targets (HARTs) in a non-nuclear package. The optimum penetration effect of a weapon in this class would be between 30 and 55 m.

In 1998 the US Navy drew up the concept for what, by 2001, had become known as the Joint Supersonic Cruise Missile (JSSCM) and Advanced Concept Technology Demonstrator (ACTD). To make the case for this weapon, CINC CFC Pacific prepared a brief that highlighted the effectiveness of a very accurate long-range, high-speed missile against mobile weapons deployed by North Korea, such as its 240 mm multiple-launch rocket systems. The same weapon would also be effective against special weapons facilities, command and control centres and air bases.

The promise held out for the JSSCM was to develop a system that could deny, degrade or destroy North Korea's strategic and operational centres of gravity within 15 minutes of the decision to launch."

Project Status

On September 28, 2007 Lockheed-Martin announced RATTLRS has completed "proof pressure testing" [what is that?]. Lockheed added: "This testing is a significant milestone as we enter into final integration and system checkouts prior to flight demonstrations planned for early 2008,"

Rolls-Royce announced on January 12, 2009 that it had successfully completed an initial test of its advanced, high-specific thrust YJ102R engine at the Indianapolis, Indiana facility. This test is the first of a series to be performed by LibertyWorks (Rolls-Royce North American Technologies Inc) , the company's research unit, and is designed to validate critical performance criteria under its High Speed Turbine Engine Demonstration (HiSTED) contract with the US Air Force Research Laboratory (AFRL).

If the US Navy is still pressing ahead with RATTLRS it would be mindful that when some US Trident submarines are fitted with Tomahawk cruise missiles meaning a cost in terms of much slower speed (time to target) compared to ballistic missiles. RATTLERS might partially make up for the shortfall. Still supersonic or hypersonic missiles suffer from, to date insoluble problems, including heat buildup, air resistence and short range for their size UNLESS:

- they have a hybrid (say turbofan and rocke) end which would mean varying velocities (though a high speed end run, say for 50 km, would be desirable) 

- and/or they are in thin (high altitude) or no air (space).

RATTLRS might also provide the new USS Virginia Class attack submarines with more potent cruise missiles, though RATTLRS might turn out to be only 20% faster than Tomahawk ie barely supersonic/supercruise.

For Australia possession of a missile with RATTLRS capabilities would be useful in the Future Submarines (Project SEA 1000) now envisaged to be operation after 2025. Air launched RATTLRS might also make up for some deficiencies in the F-35's ability to penetrate strong air defences (assuming Australia cannot buy the superior F-22 not even to face PAK FAs or Chinese made stealth jets).