Concept analysis and laboratory observations on a water piercing missile launcher Chris J. Weiland a , Pavlos P. Vlachos a,n , Jon J. Yagla b a Randolph Hall Room 114S, Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24060, USA b DTI Associates, Dahlgren, VA, USA article info Article history: Received 22 October 2008 Accepted 19 March 2010 Available online 13 May 2010 Keywords: Water piercing missile launcher Concentric canister launcher Submerged gas jet abstract The water piercing missile launcher (WPML) is a new concept for launching missiles from submerged platforms. The WPML employs a high speed gas jet, using rocket exhaust as the gas source, to create a dry path underwater through which a missile may pass without contacting water. The gas jet is deflected due to cross flow and the gas jet trajectory is computed through a semi-empirical relationship commonly used to describe single phase jet deflection. This relationship, which requires an experimentally determined constant to predict jet deflection, is computed using experimental data. Uncoupled simulations of rocket exhaust and missile dynamics are shown to demonstrate how such a launcher could be utilized in launching a generic artillery missile. Although the results indicate the optimal launch depth, in terms of maximizing the launch depth while minimizing missile restraint time, is 14 m given an 8 m/s submarine speed it may be possible to launch a missile from a moving submarine at a speed of 5 m/s at a maximum depth of 20 m. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction For the past several years, the water piercing missile launcher (WPML) has been studied both conceptually and experimentally as the next generation missile launching platform for submarines (Yagla et al., 2004, 2008). Due to its unique design, the WPML is thought to offer several advantages over conventional launchers, such as increased launch depth and increased submarine speed at launch. The primary differences between the WPML and the current launch technology are the method in which the missile is ejected from the launcher and the environment the missile travels in from the launcher to the free surface. While past launchers utilized a gas generator device to blow the missile out of the launcher, and only after the missile left the free surface did the rocket motor ignite, the WPML requires the missile to exit the launcher under its own thrust. The WPML uses the rocket exhaust gases to create a high speed underwater jet, which forms a dry environment for missile flight while underwater. An additional advantage of the WPML is that since missiles operate in the gas jet underwater, non-marinized weapons could be launched as they remain dry throughout their flight path. The WPML utilizes a unique geometry and several forward thinking concepts to combine many attractive features into one launcher, such as an integrated gas management system for each missile tube and a distributed electronic architecture (Yagla, 1997). The WPML is a scalable and modular design that includes all the necessary electronics to launch a missile in a single canister. Electronic commonality between the canisters allows for each submarine to carry many different types of missiles with a plug-and-play capability. The WPML utilizes a unique geometry so that the launcher serves as an integrated gas management system. The launcher is comprised of two concentric cylinders joined at the aft end with a hemisphere (Fig. 1). The missile is launched and initially guided from the inner cylinder. After ejection from the motor nozzle, rocket gases (arrows in Fig. 1) strike the hemisphere and are turned 1801. The exhaust gases travel through the annular region formed by the inner and outer cylinders where they exit the launcher from the fore end along the missile line of fire. These high energy exhaust gases form a jet, which penetrates into the environment. As a result of this gas management system missiles can be hot-launched from inside the ship hull without complicated systems to redirect exhaust. When the WPML is submerged, the high speed gas jet interacts with the surrounding water to form a complex multiphase flow system. For shallow launch depths the WPML acts in a ‘‘water piercing’’ fashion. The gaseous jet ejected by the launcher extends from the submarine hull to the free surface providing a dry environment for the missile to travel through as it moves towards the free surface. A schematic that depicts the conceptual operation of a submerged WPML is shown in Fig. 2 (gas jet in red, free surface as blue curve). Upon ignition of the rocket motor, the gas jet discharges into the water and leads the missile (Fig. 2a). When the missile has gained enough thrust to exit the ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/oceaneng Ocean Engineering 0029-8018/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.oceaneng.2010.03.009 n Corresponding author. Tel.: + 1 540 231 3366; fax: + 1 540 231 9100. E-mail address: pvlachos@vt.edu (P.P. Vlachos). Ocean Engineering 37 (2010) 959–965