They are a corp. grunts sent on a secret mission to retrieve valuable cargo from a colony ship. I hope they'll retain enough motivation to explore the ship for the cargo after they realize the ship has been abandoned.
naturally, I'm a day late, so I hope yer game went well.
I was gonna recommend adjusting your premise, which would help reduce the problems the other guy had.
Namely, the ship is carrying cargo, one of the containers is for the corporation.
The ship suffers a problem, and ceases communication. Last message was the engine was down. You might have the ship drift into an asteroid belt for added threat later.
So the corporation sends the PCs to get to the ship and return with that precious cargo before scavengers get to it first.
This sets the tone on WHY the party would go to the ship and that the initial percieved danger is asteroids and scavengers.
This means you can start the adventure AT the ship, or navigating through the asteroid field for a few extra initial pulls. It also sets the danger level that there may be combat with bad guys.
It's hard for players to argue that they accepted that premise while refusing to initially board the ship.
Once aboard, they'll have to explore a bit to get to the hold. If you spring on the big scary and they want to bolt, you can use the asteroid belt to damage their own ship, making them needing to scavenge parts to fix their ride.
the goal being, to get them to go deeper, keep moving, and eventually work towards escape as the second half, rather than the immediate reaction.