Space ship that moves but the player can still walk around

Not sure if I understood your question correctly but it’s quite common trick to keep the ship stationary and move the environment around it (like clouds in the sky). This will make the illusion of movement when ship/character/whatever actually is stationary. Maybe separate the landing/takeoff into own level and when the player is taking a walk in the ship use level where the above trick is used and switch between levels when required.