I have, possibly in the TNS context, but fixing the equations is off topic. If you got that part right, you'd still think the string doesn't break. I took my formulas from reviewed sites, still not as good as a textbook, but I have no textbooks, and the numbers from my formulas match those of the calculators available online. I used the nice natural unit of 1 ly/y², which is about 3% under 1g, making it also a very relatable acceleration. Still unanswered, 3rd time: 1 How does an engineer know to use the equation for a trailing rocket or not? How does NASA get anything into space if the mathematics requires knowledge of unknowable things? 2) Suppose there is a large number of ships taking off all at once, one every 10 light years. You know the series of ships is there, but you don't know where you are in the list. There might be an unbounded number of ships in the line. Now how far away from the launchpad does our ship get after 2 months? 3) The first derivative of velocity is (coordinate) acceleration. True or false?