Ronald L. Berry

“ The time of deorbit is chosen so as to result in landing at a discrete recovery area, as done in Projects Mercury and Gemini. The SPS deorbit burn is targeted so as to place the earth's horizon at a specified point in the spacecraft window for monitoring purposes.
In summary, then, as regards launch aborts, the main things to remember are: (1) abort capability in one mode or another is available throughout the entire launch phase on a continu­ous basis; (2) contingency orbit insertion followed by de­orbit is always prime when it is available. ”

“ Summarizing the trans lunar injection phase, then, one can state that: (1) redundant abort capability exist continuously throughout the translunar injection phase; (2) spacecraft performance margin is great enough to allow considerable flexibility in selection of return times and choice of a landing area; (3) the only critical or marginal abort mode is when the Service Module RCS system must be relied upon to perform the abort maneuver. This mode would only be required in the event of an SPS failure as well as failure to perform transposition and docking to obtain the LM propulsion systems. ”

“ This fact, combined with the fact that the reentry ranging capability is also relatively fixed, means that the inertial position of landing is approximately fixed for a given return plane. This means that the abort trajectory problem is essentially a timing or a rendezvous problem. In other words, the return must be timed such that, as the spacecraft reaches its relatively fixed inertial landing point, the desired landing area is just rotating underneath. ”