I know that the CSM turned around after separation from SLA, and by using its probe, it captured the drogue of LM. The CM then issued a command to latch and pull back the locking ring of LM, so that the two units can mate properly without any leakage. After that the "Probe and drogue assembly" was removed from the LM-CM connecting tunnel, and then the LM crew shifted from CSM to LM.

My question starts here: This procedure of docking is understandable because the probe was inserted in the drogue and the "latch & pull back command" was ISSUED by the persons inside the CSM. However, when the LM returned from its moon mission, it did not have a probe, so did its "drogue" performed similar functions? In case of a situation of the person is CSM was unable to issue the latch & pull back command, how the LM would have docked?

Or was it that the entire control of docking opeartionwas again with CSM and not with LM?


1 Answer 1


Looking at the "APOLLO EXPERIENCE REPORT -THE DOCKING SYSTEM by Robert D. Langley, we can find:

These initial ground rules became part of the Apollo specifications, with the significant docking and crew transfer requirements summarized as follows.

  1. Docking velocity and alinement [sic] requirements for initial contact will include an axial (closing) velocity of 0.1 to 1.0 ft/sec, a radial (transverse) velocity of 0 to 0.5 ft/sec, an angular velocity of 0 to 1.0 deg/sec, a radial alinement of 0 to 1.0 foot, an angular X-axis alinement of 0 ° to 10 °, and a rotational alinement of -60 ° + 10 °.
  2. The CSM will serve as the active docking vehicle for translunar docking.
  3. Both the CSM and the lunar module (LM) will be designed with the capability to serve as the active spacecraft for lunar orbit docking.
  4. In the docked configuration, an unaided crewman can perform all of the functions necessary to accomplish crew transfer in either direction (CSM to LM or LM to CSM).

Sadly I could not find much information about the LM as active docking vehicle, because the above report is mainly concerned with writing about what was actually experienced. my main point of concern is docking tunnel pressurization, though, as the CSm docking tunnel was usually pressurized from within the CSM. I could not find out how the LM would have achieved this.

According to the above, it should have been possible to use the LM as active vehicle for translunar docking and achieve crew transfer from the LM to CSM without the help of the crewman in the CSM.

  • $\begingroup$ @ Polygnome. Hi, thanks for your reply. While reading further on the subject, I came to know that the LM crew had one more option of entering the CSM. That was by EVA. They had the option of "manually opening the access hatch" of CSM / CM, and get in. This was provided considering a possibility of CM person being unable to take any action, for any reason. If you want, I will send you the link where this is explained. $\endgroup$
    – Niranjan
    Commented Jan 7, 2019 at 5:16
  • $\begingroup$ @Niranjan Ah yes, the EVA capability, I completely forgot about that. Please feel free to share any links you have on that topic. $\endgroup$
    – Polygnome
    Commented Jan 7, 2019 at 9:24
  • $\begingroup$ @ Polygnome: Hi, I am really sorry for the late response. I had read about EVA option while browsing through the web, and was not specifically looking for any particular information. I will search the source of my info once again, and keep you posted on that. Sorry for the delay. $\endgroup$
    – Niranjan
    Commented Jan 11, 2019 at 2:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.