Hello,
https://www.bell-labs.com/usr/dmr/www/spacetravel.html says:
Later we fixed Space Travel so it would run under
(PDP-7) Unix instead
of standalone, and did also a very faithful copy of the Spacewar game
I have a file with ".TITLE PDP-9/GRAPHIC II VERSION OF SPACEWAR". (I
hope it will go public soon.) It seems to be a standalone program, and
it's written in something close to MACRO-9 syntax. I'm guessing the
Bell Labs version would have been written using the Unix assembler.
Best regards,
Lars Brinkhoff