Page:LunarLandingMIssionSymposium1966 1978075303.pdf/352

 Seven sub-modes exist which would be available from the ground for short in this one basic mode. In other words, there exists seven different classes or abort trajectories which will be possible with a single unconstrained atttude burn, There was really no requirement for this kind of flexibility in the previous phase—in otherword, during the earth parking orbit phase—because the spacecraft was always in the close proximity of the earth, and there was really no significantly different ways to return to reentry, Beginning, with this phase, however, the spacecraft could be in a preabort orbit which extends a consderable distance from the earth, This fact, combined with the large spacecraft performance capability, means that abort trajectories having significantly different characteristics as regards $$\delta\mathrm{V}$$, return time, and landing point are possible, Therefore, plans are being made to take advantage of this situation to provide greater flexibility in real time planning.

The Seven sub-modes available are as follows:

Time critical returns to a contingency area. This class of abort returns the spacecraft to a contingency recovery area in the quickest possible retrun time consistent with the constraints of the situation. A contingency recovery area is a continuous line