Quote from: wiki
The Novikov consistency principle assumes certain conditions about what sort of time travel is possible. Specifically, it assumes either that there is only one timeline, or that any alternative timelines (such as those postulated by the many-worlds interpretation of quantum mechanics) are not accessible.What if the time traveller killed his grandfather and then continued his timeline in that 'World'?
There is one complete 'time line' for the traveller, wherein the result of the time travel was a new 'World' without the grandfather. But he would not suddenly disappear because his timeline includes being born on the 'World' where his grandfather was not killed.
Both 'Worlds' would continue to exist as separate and multiple worlds...
And before any one suggests it – he could not go back and give his younger self the plans for the time m/c or even give him the time m/c unless the time m/c was developed and built for the first time in some previous time line.