Apologies, I have not read the books in a long time. I was curious how John Carter travelled to Mars? My initial thought was that it was some "new age" (for the time?) Astral Projection type process. His body itself stayed on earth, but he manifest his Astral form on Mars?
As I think a bit more about War of the Worlds: Offensive how would the Humans get to Mars? I can think of only a few examples and those would be Space: 1889, Flash Gordon, and John Carter. The Space: 1889 and Flash Gordon models seem less likely in the AQMF timeframe, so that left me to recall the John Carter method of travel.
The Space 1889 world depended on the ‘luminiferous ether” which permeated all matter. By clever invention, it could be harnessed to provide propulsion in vacuum by the “ether propeller.” Ether propellers were invented by famous electromagnetic experimenters like Edison, Tesla, Armstrong and others.
Ether propellers did not work at low altitudes due to atmospheric interference, so they could only operate at high altitudes (above 12.000ft). However, when “liftwood” was discovered on Mars the problem of low altitude flight was overcome. Liftwood created a gravity shadow above it rendering things above it weightless. This enabled a combined liftwood/ether propeller craft to be created for surface take-off and vacuum flight. Before lift wood was available, ether propeller flight had to be from high mountaintops or from balloons or dirigibles. The laboratories working on them were located far up mountains.
While we are at it, let us remember “Cavorite,” a synthetic analog of lift wood. HG Wells created it his book The First Men In the Moon. By blocking gravity on one side or the other, his spacecraft could liftoff and maneuver.
I re-read the first few books in the series two years ago. Hadn't read them since junior high! The way he's transported to Mars sounds like a form of astral projection - with the major exception that his body went too! The cave he sheltered in from the indigenous warriors was a portal of some sort. How he got back to earth wasn't as clear, but later he's able to will himself back to Mars, apparently from any location.
It is possible for humans to get to Mars with "Steampunk Technology."
Create a tube, about 100 meters in diameter. Along side it is a tube 10 meters in diameter. Both pointed up. They are connected at the bottom. The whole structure is in a earthen mound.
The small tube is empty, at the bottom there is a "capsule" with the appropriate payload.
The larger tube is filled with water.
Explosive bolts are detonated. The water from the large tube is released and pushes the capsule up.
The "flush toilet" has the energy to get a payload into space. A journey to Mars is possible.
In a place like the Space Coast in Florida, there is enough rain to make this system work. The space coast was chosen for rockets because it is close to the equator and Earth's rotation gives space capsules a boost.
well... in the war of the worlds setting you could use flash boiling of the reservoir with captured heat rays to make the system more efficient by water volume, allowing you to send larger payloads, or small payloads with less water. actually, the Martians may have used something similar.