Where possible, I'd like to do a hard-science approach, but only so far that it produces a fun and believable experience. Some games take the hard science approach too far and this results in a tedious, painful, grindy experience (ie No Mans Sky). I'd like to put effort and thought into things to make it believable, but will eschew hard science in favor of semi-realism that sounds like it could be possible, but probably isn't if someone crunched the numbers. I may tweak things if people with the hard science backgrounds gives me feedback, but as I don't know anyone with a Bachelors in any of the sciences, I'll have to go by my own personal understanding of how physics, biology and chemistry works (I took Phy, Bio, and Chem 12 in high school, so I'm not totally screwed on this front, and have completed Single-Variable Calculus in University with an A-)
As for the Drones themselves, I was thinking that they used a combination of jet-engines and turbo-fans; Turbo-Fans for hovering in a spot, while jet engines for moving forward. However you do make a good point, that in order to operate in a low atmosphere planet without much breathable oxygen, it would produce unique problems for hovering drones. I'll have to think on drones then...
-----
Also new file: Manmade Disasters! Summary:
There are three manmade disasters that are entirely avoidable with correct player choices. They each provide a sort of risk-reward kind of choice for the player. The three are: Rioting, Containment Breach, and Rain of Fire.
Rioting occurs when you have insufficient consumer goods to meet the entire colony, and then a check is performed to see if a riot results. If one does result, all structures take 10% to 20% of maximum HP as damage over time and you suffer a morale drop as this is a negative morale event.
Containment Breaches occur when a lab that is currently researching something takes damage. The chance of the breach is based on damage suffered + current damage taken. If a breach occurs, you either release a Plague, an Explosion, or an EMP, depending on the research you are currently researching. The severity of the breach is based on Maximum HP of a lab, and thus Advanced Labs are always worse as they have more HP, but also are less prone to them, as it will take more hits before it finally suffers a breach.
Rain of Fire occurs when you destroy an enemy missile or space-stuff with a mass driver or a hunter killer (survivalists). Creates a meteor shower that deals damage over an area, but no guarantee it will be over your base or their base; site chosen randomly.
---
Potential solution to the drone problem:
Bomber Drones have a special fuel mixture that would provide it's only oxygen (much like how thruster engines in a vacuum work to produce combustion-based thrust) but would need to refuel at a Drone Factory. This limited fuel would also limit their attack distance as if they ran out of fuel, they would crashland.
The other two drone types have battery-powered turbo-prop fans for lift. They also have solar panels on the roof to provide some power to restore the batteries (but not enough to keep them airborne), allowing them to field recharge their batteries. Multiple structures would be set up to provide battery recharging, when near a base. They would also have a thruster engine that could provide a boost in forward momentum, but would require refueling at a Drone Factory.