Multi-purpose vehicle with folding wings would be fired from ex-Trident missile tubes

Lockheed Martin has revealed new details of its submarine-launched and recovered multi-purpose UAV (MPUAV) proposal as it embarks on a two-year study of the concept with the US Defense Advanced Research Projects Agency (DARPA).

The MPUAV concept, built around a compact 450kg (1,000lb) payload vehicle with folding wings, is likely to merge downstream with the newly revealed morphing UAV project, says senior project engineer Robert Ruszkowski.

Intended to be launched from the missile tubes of a converted Ohio-class submarine, the MPUAV is designed for a 1,100-1,300km (600-700nm) radius of action and for carrying surveillance and reconnaissance payloads as well as weapons such as Boeing's small-diameter bomb and Lockheed Martin's low-cost autonomous attack system (LOCAAS) mini-missile.

The 5.8m (19ft)-tall vehicle would be boosted out of one of the submarine's 24 ex-Trident missile tubes by two expendable Mk135-class Tomahawk missile rockets. This would provide a 10-12s window to start up the UAV's 3,000lb-thrust (13.3kN) turbofan engine, possibly a Honeywell AS903 derivative. High-pressure nitrogen would start the engine rapidly, as well as over-pressure the internal cavities of the UAV by about 0.345bar (5lb/in2) to offset pressures and prevent water ingestion. Silicone-based sealants and syntactic foams would also be used to prevent leakage.

These features would also help maintain low observability during the UAV's flight towards the coastline after launch and wing deployment. After completion of its mission, the UAV will return for a splashdown recovery, which is a "whole different ball game with a 9,000lb aircraft and a 125-130kt [230-240km/h] stall speed", says Ruszkowski. "There are several ways to do it. One is to stall and do a pre-programmed 'Cobra' manoeuvre, and a more plausible option is to deploy a chute and re-enter nose first." The target is to keep impact loads in the 5-10g range, requiring a 4.5-5.5m-diameter parachute.

Below the water, the UAV would be located by sonar and recovered by a remotely operated submersible.

Source: Flight International