What is TR-20?

The TR-20, also known as the Rocketdyne LR115, was a liquid-fueled rocket engine developed by Rocketdyne for use in the Apollo Lunar Module Descent Engine (LMDE). It was a throttleable engine that used Aerozine 50 as fuel and N2O4 as oxidizer. Its key feature was its deep throttling capability, allowing the LM to adjust its descent rate to the lunar surface with high precision. The TR-20 was crucial for achieving safe and controlled landings on the Moon during the Apollo program.