The Rachel is a prototype Yeerk ship. It is said to be a quarter the size of a Blade ship, and five or six times the size of a Bug fighter. It was the Yeerks attempt at developing an Intrepid-class ship. It is known for being incredibly fast and heavily armed. At the end of the Andalite-Yeerk War, this ship was surrenderd and kept in orbit around Earth for sometime.
After Prince Aximili's ship was captured by the The One, Jake, Marco and Tobias stole this ship to rescue him. These "New Animorphs" consisted of of these three original Animorphs and along with Menderash-Postill-Fastill, an Andalite in permanent human morph and two of Jake's trainees Sergent Santorelli and Jeanne Gerard. However, before they could board the new ship, they needed to name it, in accordance with Andalite tradition. Tobias observed that the ship was "beautiful and dangerous and exciting", so the ship was named The Rachel in memory of Rachel their fallen friend