In the first season of Lost in Space, the Robinsons encounter only one earth ship besides their own Jupiter 2. This occurs in the episode “Welcome Stranger” where Jim Hapgood lands on Priplanus in the Mercury- or Gemini- like space capsule he has been travelling in for a dozen years or more. Other members of this wiki have raised the question of whether or not Hapgood’s ship was only a landing vehicle; it is rather difficult to imagine such a small ship being able to hold the food and air (or even equipment to produce or recycle those) necessary to a voyage of any duration. “The Raft” features a knock-up capsule the Robinsons build using their atomic reactor core, but it does not manage to reach escape velocity and crashes back onto Priplanus.
The first alien ship encountered in the series is the eponymous derelict bubble creature spaceship. It seems (from information given in the season two episode “The Prisoners of Space” that this ship was in fact a sleeper ship—that is, its inhabitants were in a state of suspended animation during their voyage.
Perhaps the most intriguing ship ever to appear in the entire series was in “Invaders from the Fifth Dimension” (which also showcased two of the best aliens in the series). Unfortunately, this ship was not seen again in the series, either as a ship or as a prop.
The ship in “The Derelict” also appeared as part of the machinery in the Andronican’s spaceship, the exterior of which was it self a reuse of the ship first appearing in both parts of “The Keeper” (itself a very cool and plausible design for a ship built to carry live cargo).
The other ships which appear in “The Sky Pirate,” “The Space Trader,” “The Space Croppers” and “A Change of Space” are less impressive. They are all rather small or, as in the case of “The Space Croppers” merely a back-woods cabin with rocket nozzles. When in space, Effra affirms, they have was of making it airtight. A similar dodge is used in the season two episode “West of Mars” where the space ship is a jail cell that gets covered in plastic wrap when in space. The ships in “A Change of Space” are simply redresses of props from Irwin Allen’s previous catalogue.