What is rs 25?

RS-25 is a liquid-fueled rocket engine that is designed to be used on the main propulsion system of NASA's Space Shuttle. It was developed by Rocketdyne (now Aerojet Rocketdyne) and was first used in 1981 when the Space Shuttle Columbia was launched.

The RS-25 engine uses liquid hydrogen as fuel and liquid oxygen as an oxidizer to produce thrust. It has a thrust of around 470,000 pounds and its specific impulse (a measure of its efficiency) varies between 363 and 452 seconds.

The RS-25 engine was used on all Space Shuttle flights and is considered one of the most reliable and efficient rocket engines ever developed. After the end of the Space Shuttle program, NASA began reusing and upgrading the engines for use on the new Space Launch System (SLS) rocket that is being developed for future deep space missions.

Each RS-25 engine costs around $50 million to produce and has a lifespan of around seven flights. The last RS-25 engine was delivered to NASA in October 2019 and is expected to be used on the first SLS launch in 2021.