To run Space War you first need the Multiple Emulator Super System (M.E.S.S.) from www.mess.org (freeware)
This program runs very similar to MAME, with a similar folder structure. However, none of that needs to be configured. All you need to do is launch the program by means of double clicking messgui.exe
Next, download this .zip file which contains a useful readme.txt from the creator of the file, Raphael Nabet, as well as the spacewar.rim file that M.E.S.S. requires.
In M.E.S.S, navigate down the list to the PDP-1 entry and double click.
A largely black screen will appear showing a number of controls and a familiar File menu along the top.
Click Devices > Punched Tape #1 > Mount… and navigate to the spacewar.rim file.
You would expect the game to begin however, you are really only half way there. The file is mounted but has not yet been “fed” into the virtual PDP-1. You need to hit Ctrl-Enter in order to fed the program into the machine. You will know you have begun when you see the blinking light indicators showing the load in progress. These blinking lights can be seen on a real PDP machine here.
When completed, Space War begins!
There are details in the Spacewar readme.txt on how to control the two ships. For simplicity I have copied that section of the readme.txt here so you can start playing right away but I would urge you to read the entire file to be able to configure various game settings.
Control the ship with the controllers (under the MESS pdp-1 emulator with default key mapping and QWERTY key captions, they are mapped to the A, S, D, F and Z keys for player 1, and to the arrow and / keys for player 2)
Many thanks to Raphael Nabet and the people behind M.E.S.S. for making this fantastic emulation possible.