The RD-843 is a Ukrainian single nozzle liquid propellant rocket engine.
It burns a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide (N2O4) oxidizer.
[2] It was developed by Yuzhnoye Design Bureau for Avio and is manufactured by Yuzhmash.
It uses the RD-869 thrust chamber, the old Soviet ICBM SS-18 final stage engine from which it is evolved, and which was also designed by Yuzhnoye.
[5] The Vega and Vega C uses it as the main engine on its AVUM (Attitude & Vernier Upper Module) fourth stage which it calls the MEA (short for Main Engine AVUM).