Why Is the Neutron Rocket Using Carbon Fiber Composite Instead of Stainless Steel?

SpaceX abandoned the use of carbon fibre composite and instead went for stainless steel in their Starship. So why is Rocket Lab sticking with Carbon fiber composite?

Isn’t carbon fiber composite really expensive to build rockets from? That is a question I recently got. It is a good question because items made of carbon fiber composite are typically expensive. Elon Musk himself made a big point of how much money they were saving by going for stainless steel instead of carbon fiber composite, which was their initial choice for the Starship rocket.

However, carbon fiber as a material is actually not very expensive. It isn’t made of any rare minerals. It is basically made from hydrocarbons. Threads are made from polymers. It is similar to fabrics made from polymers such as polyester or nylon. Carbon fiber begins life as a Polyacrylonitrile polymer. Polymer just means similar-looking atoms chained together into long strains.

Example of a polymer. CH₃ molecule is repeated multiple times to create a polymer.

This polymer gets processed to create long strands of carbon atoms. These are spun into threads which are then woven into cloth. You can in fact get clothes made of carbon fiber. Here is a cap made from carbon fiber.

A hat made from carbon fiber.

To get an actual hard material you can build structures out of, you need to soak the carbon fiber cloth in a resin (liquid plastic) such as epoxy and let it dry to harden. You can think of Carbon fiber composite as a plastic material with carbon fiber threads inside to keep it together better. This is similar to how we put steel bars inside concrete. Glass fiber composite as commonly used to build boats is using a similar process.

In both cases, it is not the raw materials which are expensive. It is the process. Building things out of carbon fiber has long been expensive. For example if you make a bicycle frame…