drop pods (perhaps precursor to the dropships) is a standard transportation mentioned in the Doom series.
The hero of Doom II (Marine (Doom II)) is said to have gone on leave after defending the UAC Mars Base on Mars. He reached earth by drop pod discovering it had been overrun by demons from the Outside.
Dropships also appear in Doom Resurrection.
Dropships or drop pods figure into the plot of Doom RPG and Doom II RPG, B.J. Blazkowicz III reaches Mars in one, and one is shown in the Doom II RPG comic, and also at the beginning of Doom II RPG.
Behind the scenes
The Hell on Earth novel appears to reference the backstory to Doom II in part as Flynn Taggart and Arlene Sanders flies back to earth from Deimos (rather than mars) using a modified mail rocket/shuttle. Amusing there is a reference to 'repelling back to the surface of earth' which is likely a nod to the repelling to surface of Hell in Doom 1 (as one of Flynn's sarcastic ideas). The shuttle drop is similar to the use of the drop ship in Doom II manual.