<font color="yellow">"1) The Non-Constant(Unless you have a nice engine) thrust produced by the engine, for this I have no clue how to do."</font><br /><br />I'm assuming this means the change in thrust by altitude. Propforce already gave the basic equation and pointed to Sutton's book, since I just got my copy I'll attempt to chime in little more details from it.<br /><br />Total engine thrust comes from two part, momentum thrust and pressure thrust. First part is the basic Newton action-reaction 101, engine throws propellant backwards so the rocket gets pushed forwards. This thrust remains the same despite altitude. Pressure thrust is the result of difference between ambient pressure and exhaust gas pressure at nozzle exit. If exhaust gas pressure if bigger than ambient then you get positive thrust from it. To sum this into equation:<br /><br />F = <i>d</i>m*v<sub>exit</sub> + (p<sub>exit</sub> - p<sub>ambient</sub>)*A<sub>exit</sub><br /><br /> <i>d</i>m rate of propellant consumtion, v<sub>exit</sub> exhaust gas speed at nozzle exit , A<sub>exit</sub> nozzle exit area<br /><br />I recommend getting the Sutton book, bit pricey but it's worth the every cent! <br /><br />(Especially when Amazon UK sent along with the books a voucher to a <i>lingerie</i> shop, 30% rebate from 100£ garments ... I guess they thought the rocket interest has a Freudian meaning!?)