The file is the first segment of a multi-part compressed archive.
When large games or programs are shared online, they are often "split" into smaller pieces (parts) to make them easier to upload and download. To use this file, you generally need to follow these steps: Kerbal.Space.Program.2.Early.Access.part01.rar
What are you seeing (e.g., "Unexpected end of archive")? Do you have an extraction tool like 7-Zip installed? The file is the first segment of a