TEPREL

In the first versions of the engine the propellants are driven to the engine by using a pressure-fed cycle with helium.^[5] Later versions of the engine (TEPREL-C) incorporate a turbopump.^[6]

The TEPREL-DEMO engine, originally called NetonVac1, was first tested in 2015. It is a calorimetric engine model, intended to demonstrate combustion stability as well as to acquire relevant information such as ignition and shut-down sequences, pressures and temperatures along the engine, thrust and propellant mass flow rates at different thrust profiles. Additionally, the engine served to test all associated hardware and software at PLD Space Propulsion Test Facilities. The engine is capable to produce a thrust of 28 kN at sea level.^[7][8]

With the TEPREL-A engine, first tested in 2017, the company included several design upgrades, such as a new combustion chamber design,^[9] an improved injector geometry and a regenerative cooling system. The later enables the engine to fire for nearly 2 minutes, which is the envisaged nominal functioning duration for the suborbital launch vehicle Miura 1. At sea level, the engine produces a thrust of 32 kN.^[8][7]

TEPREL-B is the first flight version of the TEPREL engine. Several design improvements have been implemented to reduce the overall weight of the engine. It is equipped with a thrust vector control system^[10] and a convergent-divergent nozzle, all regeneratively cooled.^[11] In May 2019 the first unit of this model was destroyed during a test. After a long investigation PLD Space concluded that the problem was due to excess pressure during engine start at ignition. PLD Space addressed the issue through a combination of improvements to the launch site infrastructure and procedural improvements.^[12] It is currently fully operational. In February 2020, PLD Space successfully completed a 122-second test that allowed it to achieve flight rating.^[13]

On August 28, 2020, PLD Space completed required tests for the thrust vector control system on the Teprel-B rocket engine.^[10]

Flight version of the TEPREL engine^[14] to be used in the Miura 5 rocket. Initially it was expected to produce 105.5 kN^[15] of thrust at sea level.^[6] Later expected thrust was increased to 190 kN.

Version of TEPREL-C adapted to vacuum, and capable of re-ignition in microgravity conditions.^[16] Capable of 75 kN of thrust.