Lost in Space operates on a principle I like to call “Chekov’s Time Machine.”
With 20 years, and only an older/mutated Dr. Smith to nurture his ambitions, Older Will creates a working portal to the past.
As we see young Will Robinson’s experiments in creating a temporal distortion device yield some interesting school science projects, it’s eventually revealed that Will’s designs were pretty solid.
Generating a window in time that one could literally walk, or jump, through, Lost in Space makes it as simple as turning on the machine, punching in the time and place you’re looking to go back to, and making it happen.