Until May 8th you can download Dead Space 1 for free.
Link: https://www.origin.com/store/buy/dead-space/pc-download/base-game/standard-edition-ANW.html
If you want to "purchase" it without Origin installed:
Link: https://www.origin.com/store/cart/add/eyJPRkItRUFTVDoxMDk1NDc1MjAiOjF9...