1. The problem statement, all variables and given/known data Hi! I was wondering how one can calculate the time we have to intercept and destroy a NEO? I have the semimajor axis, eccentricity, true anomaly, (v) inclination and r (a negative value) for the object, but I don't know where to begin). 2. Relevant equations All the orbital parameter equations (not in vector forms) 3. The attempt at a solution I know that it is a hyperbolic orbit since e is greater than 2. Its position and velocity are related to the semi-major axis, which we have a value for. We have to take into account that the Earth has a speed, and that the speed at the equator (in units of km/s) can be calculated with: Ve=2*pi*R/(24*3600) The orbital speed can be calculated from conservation of energy. The total energy of the comet is E=(1/2)mv The period of the NEO can be calculated with: P^2=((4*pi^2)/(G*Me))*a^3 (Me = mass of Earth, we can neglect the NEO's mass). I am sure that I need to include the period of both the Earth and the NEO I know that I have many equations regarding the orbital parameters, but I don't know where to begin. Can anyone guide me (with explanation and/or what equations to use)? Thanks in advance!