A level AQA computer science NEA

Is creating a simulation of the universe (mainly just the solar system) a suitable investigatory project for A level computer science NEA, using unity and modelling things such as gravitational forces etc.? Is this suitable enough to get an A or A* in the NEA?

Its very hard to say without the whole doc. You need to show an iterative process and show a good level of syllabus, like use OOP. You need teacher feedback to develop your ideas even further. This feedback loop needs to show to give the high marks, have you looked at examplars of A graders, just google it. You will have to work on what is said in the feedback. This is the whole idea of agile process. You work on the feedback.

I understand however is the idea itself is of A-level standard and could allow me to access the higher marks if I do the documentation well and follow the agile process?