When Lost in Space first took off in 1965, it was set in the distant future of 18 years or so ago. Many examples of the technology used in the show were plausible developments of contemporary items extrapolated into the future… the walkie talkies, miniature microphones and weapons portrayed in the series were all believable at the time. We now know that lasers are singularly ill-suited to use as a hand-held weapon (that is why Star Trek invented the phaser to replace it), and even my first cell phone was more compact than the Robinson’s walkie-talkies.
But there were other items of technology that made appearances throughout the series; some were one-off items, others were regular background set dressing or provided business for the actors in a scene. Others were rather scientific and useful machines with little historical precedent (and often, little scientific accuracy).
Early in the series Will repairs what is referred to as a radio telescope, but laments that he still hasn’t been able to restore sound with the picture it picks up (John being attacked by a giant cyclops). The misnomer, inexcusable as radio telescopes were in use when the episode was written, still sounds cool and perhaps explains the assumption that sound was part of what it was designed to pick up.
In season two Will uses a material analyser to identify something outside the ship in space; it occupies the same location as the radio telescope had. That particular console can be seen in a number of episodes to have the one, the other, or neither piece of equipment installed. Perhaps it was an all-purpose jack of sorts.
The Robot turned out to have an add-on replicator (“The Space Vikings”) but it was only used for rather trivial items. It makes its second and last appearance in “The Galaxy Gift” (where it is used for equally trivial purposes). Why the replicator wasn’t used more frequently by the Robinsons to solve their chronic shortage of parts is never explained. It may simply have been that it had a limited capacity or needed specific raw materials to work from, or even had a limit on the complexity of what it could duplicate.
In “Mutiny in Space” a rain making device is used to ill effect by Dr. Smith. It is not really that far-fetched a mechanism; the principles of cloud seeding were long known at the time the episode was written, and it is not too much of a stretch to apply them as they were in this episode.
A food purifier features in “Space Circus.” It might have worked by radiation, but the open bay into which the plants were placed for treatment would make that very unsafe. It seemed to be rather complex, so it likely used a range of radiation; the trick was to find the right combination of levels of the different bands. In reality, gamma radiation and x-rays are routinely used to sterilise different things in a variety of contexts… but you don’t want to stand too close while it is being done.
Some of the devices used by the crew of the Jupiter 2 had a definite Heath Robinson facet to them; others were far more plausible, and not at all far-fetched.