When low on energy, kill worker doctors and even Red Faction men to pick up more health and Environment Suits.
When Hendrix first starts talking to you, go down the catwalk away from the APC. There should be a tunnel that leads to a miner and guard fighting. Shoot that guard then shoot the one at the elevator. Stand in front of the elevator and face the wall behind it. Look up slightly to see a hole. Enter the hole and at the end is a pond or lake. At the bottom of the pond is a miner's body, health, and an Environment Suit.