Model tests and time domain simulations for launch and recovery

Launch and recovery model tests have been in constant evolution for more than a decade thanks to a continuous improvement of model manufacture and instrumentation. While the first tests could only look at mated craft, it was very soon clear that self-propelled vehicles are necessary to also study the approach and extraction phases. Previously, this was done with radio-controlled models steered from the carriage by a trained helmsman. Because this solution introduces quite some challenges regarding assessment of human influence, more work has been done to develop autonomous models. This work has been started within the LAURA JIP (LAUnch and Recovery of Any small craft Joint Industry Project) which is focusing on the development of a standardized launch and recovery system for naval applications. In the current phase of the JIP, the craft model has been further developed to include the full approach and extraction phase. The optical tracking system has been improved, as well as the radio control system, to allow a real-time positioning of the model along a prescribed track mimicking the full scale approach trajectory of a RIB. Thanks to this new testing approach it was possible to quantitatively compare recovery conditions. This also opens the door for USV testing since there is no longer a need for human control of the vehicle. Finally, MARIN has made a further step to use time domain simulations for preliminary assessment of the launch and recovery system. The simulations are based on the tests of the first JIP phase in which the craft was performing station keeping at a prescribed distance from the mother ship. This was done with fast time domain simulations with limited hydrodynamic interactions.