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Space Exploration

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  • $\begingroup$ I hear you, but I feel a quibble coming that I cannot fully actualize about counting the LEM. And the Descent/Ascent as two more stages. What about SM, for TEI then? $\endgroup$ Commented Aug 7, 2013 at 21:57
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    $\begingroup$ There's a difference between a "module" and a "stage". The "service module" has a rocket motor, while the "command module" does not; it's just an environmental compartment unlike virtually any other module of the Saturn V/Apollo vehicle. The Saturn V itself is three stages: five F1 liquid motors (S-1), then five J-1 liquid motors (S-2), the two in combination being enough for LEO, then a single J-2 engine in the S-IVB (S-B) third stage that would break LEO and head out to the moon, carrying the LEM and CSM. $\endgroup$ Commented Aug 7, 2013 at 22:57
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    $\begingroup$ The CSM would then separate, dock with the LEM stored underneath it, then as this pair reached the moon, the CSM's SPS would fire to settle into a stable orbit of the moon (instead of slingshotting around). The LEM would separate, use the DPS "descent stage" to land, the APS "ascent stage" to return, then the CSM's SPS would fire to break lunar orbit and return home. Ideally, the firing of the SPS to break lunar orbit is the last time a "main engine" on any part of the Apollo vehicle fires. $\endgroup$ Commented Aug 7, 2013 at 23:03
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    $\begingroup$ So, call it six independent stages of disposable rocket motors, used in seven "phases" of the Apollo mission requiring some part of the vehicle to speed up or slow down using rocket thrust: Launch, LEO, LEO departure, lunar capture, LEM descent, LEM ascent, lunar orbit departure. The final phase, re-entry deceleration, is accomplished using the Earth's atmosphere as most of our space vehicles do. $\endgroup$ Commented Aug 7, 2013 at 23:06