For  invulnerability  in  this  game,  use the DOS utility DEBUG.
First  backup your game to be edited, then type the following from the
DOS prompt:

ren raider.exe cheater.cht
debug cheater.cht
e 1460 f8 c3
e 920 90 90 90
e 901 90 90 90
Then type:
w
q

Then rename CHEATER.CHT back to its previous name.