Astral projection was a psychic power that involved the mind (or soul) leaving the physical body and entering the astral plane. Humans developed a method of astral projection which allowed for psychically travelling to different planets as opposed to doing so in starships. (TV: Image of the Fendahl)
The Fendahl had such enormous energies that it was able to project itself from the Fifth Planet to Earth before being trapped in a time loop, possibly ravaging Mars along the way. (TV: Image of the Fendahl)
The Osirans were capable of mentally projecting themselves, and also designed psi-projectors which let them travel through space using only the power of their minds. (TV: Pyramids of Mars, PROSE: The Sands of Time)
In the 2010s, astral projection was dealt with in a popular film called Doctor Strange. Bill Potts suggested that the Twelfth Doctor watch Doctor Strange after he used this term, (PROSE: The Shining Man) and later compared her own astral form upon escaping the Dreamscape with those which were depicted in this film. (COMIC: The Soul Garden)