Your TranStar suit starts off with 45 slots of inventory space, and everything has to fit in here. You’re going to run out of room in your inventory — probably pretty early in the game, in fact. Luckily, expanding your inventory is pretty easy. Unluckily, it requires a pretty precious resource to do it.
Upgrading your suit requires you to gain the Suit Modification 1 (and then 2 and 3) ability from the neuromod menu. The first upgrade will increase your inventory to 60 slots, the second will increase it to 77 slots and the third will max out your inventory at 96 slots. Getting to the maximum inventory size will take 13 neuromods.