Hi lunarsignals!
I'm glad your group is enjoying Impulse Drive! Combat in Impulse Drive is a mixture of the freeform Roleplaying>Moves>Outcomes style of play you find throughout normal play, but has its own ecosystem of moves that play off each other to give you a scifi action feel similar to shows like Farscape or Killjoys or games like Masseffect 2.
You don't necessarily enter combat formally with a roll for initiative but flow in and out of action as the stakes change through play. In the game, I refer to a group of moves as "action & combat" because an action scene isn't always about shooting space guns or waving around laser swords, and can also be running, scooting behind cover, a vehicle chase, or any number of dangerous or exciting scenarios.
The biggest thing to keep in mind as to whether you're in an "action & combat" situation is how much immediate pressure or danger is preventing characters from taking their time or acting casually. If a player wants to recover some harm or gather their wits, is it dangerous to stop and do so or are they out of immediate danger?
If there's no immediate pressure & the character(s) have a chance to catch their breath or regroup, you've probably left "action & combat" situations & can regroup - either have small scenes of character licking their wounds or regrouping for the next ordeal. If there is immediate pressure or danger, players roll the Recover Move to give their character a moment to get into cover & prepare to continue the engagement.
I also recommend that you have NPCs treat dangerous situations as their character suggests. When does the cost of violence become too high? When are the NPCs likely to give up, surrender, or leave? What will the NPCs demand if they have the upper hand? What might force the NPCs to fight to the bitter end?
My final piece of advice is to treat the determination of when the situation is dangerous or not as a part of the conversation. Discuss it as a group, and find a consensus you can all agree on.
If you'd like to see Impulse Drive in action, you can watch this game I ran for some awesome folks over at The Gauntlet a few years back: