 During the following year, an aft-facing Bristol-Siddeley Viper III jet engine, mounted on the rear of the decking behind the lift fan housing, supplemented the ducted-air propulsion produced by the piston engine, increasing the craft's maximum speed from 35 to 50 knots; the Viper installation followed an earlier installation of a Blackburn/Turbomeca Marboré of approximately half the Viper's thrust.The SR.N1 was involved in tests for a total of four years prior to its retirement, having demonstrated the practicality of the concept.The SR.N1 itself has been preserved and placed on public display at the Science Museum at Wroughton.