Well, one could argue that missions take place near enough to the planet but not actually in orbit (where gravity would act as a centripetal force), so the planet’s gravitational pull must also be constantly counteracted in order to avoid crashing into it. Part of the engines’ thrust is therefore ‘lost’ to that end, leaving less thrust (=acceleration) available to perform flight maneuvers.
Well you made me remember something that could help with travel in CIU.
You all must know Battle Royale games. There’s this toxic areas, storm or whatever you call it and you can’t stay in one place because of that. So here’s three ways we can add it to game with small portion of sense:
Gamma rays. Not much to say. When there are gamma rays you need to avoid contact with them, but I don’t think that it would be possible to indicate in which area the gamma rays are.
Supernova. This would make more sense and be easier to show on map. it’s also easy to explain: The sun explodes and if you want to stay alive you need to go to other solar system. Simple.
Cosmic rays. This could be as well gamma rays above, but this is the theory that @BinhTurtle made me remember and I should mention it. So there’s a theory that there is a correlation between our solar system place in milky way galaxy and extinction of species. Here’s the link to explain that better than me: Death Rays From Space: How Bad Are They? | Space (It’s under Cosmic ray roulette heading)
And here’s the source: https://iopscience.iop.org/article/10.1086/518757/pdf
Well I agree with all of your ideas except the third one because imagine beating a level with heavy-bomber BX-9…imagine how slow would it move and how hard would it be to beat that level for example.