A new variable-thrust engine was recently tested in Poland with different rates of propellant flowing through it, controlled by a new system of valves to control the flow of propellant along with a movable ‘pintle’ injector, all being commanded by an electronic control system.
A throttleable engine like this has many future applications, from landing rocket stages on Earth to upper stage ‘kick stages’ and exploration missions requiring a descent onto a moon or planet.
The bright nodules visible in the engine exhaust are ‘mach diamonds’ (or shock diamonds), a phenomenon created when supersonic engine exhausts are ‘squeezed’ by the outside air pressure. With the engine on the lower, 30% thrust, more diamonds are seen compared with when it fires at 50% and full throttle, as the lower thrust exhaust is more susceptible to outside pressure.
The new Throttleable Liquid Propulsion Demonstrator (TLPD) engine will now be dismounted and inspected, and the results will be analysed at the site of the prime contractor ‘Łukasiewicz Research Network – Institute of Aviation’ (Lukasiewicz-ILOT) in Poland before the next phase of testing begins.