And the last paragraph is the main problem. The ship would get torn apart from lone atoms and to actually stop yourself you need an exponential amount of fuel, because you need to accelerate ( much more than )half of it just to stop yourself.
Even if you protect yourself from relativistic atoms, they still create a drag. And that happens before you reach 0.99c.
Even if you protect yourself from relativistic atoms, they still create a drag. And that happens before you reach 0.99c.