The Lunar Module RCS Plume Deflector

A critical part of the Lunar Module was manufactured in a way you may not expect.

Apollo 12 Astronaut Pete Conrad captured this picture of Alan Bean as he descended the ladder on the Lunar Module Intrepid. Note the RCS Plume Deflector on the ascent stage of the Lunar Module. Photo- NASA

Here’s a piece I wrote on LinkedIn a few years ago. I mention it here because the engineer who designed the RCS Plume Deflector reached out to me via LinkedIn earlier today. I’ve updated it a bit from it’s original format and content. Enjoy!

Trimming ounces off of spacecraft components is a challenge that all aerospace manufacturers face. A delicate balancing act of shaving weight while maintaining capability has led to some incredible designs over the years.

The Grumman Corporation (now Northrop Grumman Corporation) built the Lunar Module to be as light as possible, which is partyly why it has such a unique shape and design. Part of building a light spacecraft involved new manufacturing techniques, resulting in components like the reaction control system (RCS) Plume Deflector seen below.

The RCS thrusters on the Lunar Module were a series of small mini-rocket engines capable of producing 100 pounds of thrust. These thrusters provided the means for astronauts to control the attitude of the spacecraft. Like any rocket or thruster, they also produced heat and an exhaust plume which could have damaged the thin skin of the spacecraft, had the RCS Plume Deflector not been there.

Engineers devised a solution that used layers of Inconel, Inconel mesh, and Nickel foil. It was light enough to meet weight constraints while also being able to withstand temperatures of up to 1800 degrees Fahrenheit.

I always assumed this part of the Lunar Module was just a solid piece of metal and never gave it another thought. It never occurred to me that this piece was manufactured as a blanket using super alloys like Inconel. An ingenious and fascinating bit of manufacturing history.

The last picture in this post shows a cross-section of the Inconel mesh that was used for the Plume Deflector. Diagram- NASA