This video is hopefully going to simplify the Apollo docking system and make it easy
to understand. I have read a lot of NASA documentation on
the subject but couldn’t find many animations to show the actual system in operation.
Now the Probe and Drogue docking system was approved over many other concepts in 1963.
Mainly because it had the least weight penalty The final configuration of the Apollo docking
system consists of the Lunar module tunnel ring and hatch, the drogue assembly, the probe
assembly, the Command module docking ring, and automatic ring latches, and finally, the
Command module forward hatch,
. The docking ring is bolted to the command
Module and serves as the mounting structure for the docking latches, the electrical connections,
and the two seals that allow pressurisation of the docked Command Module and Lunar Module
tunnel area.
The drogue assembly is a truncated cone structure that is installed in the LM tunnel and serves
as the guide and the receiver for the probe head.
The drogue consists of a 1-inch-thick aluminum honeycomb (sandwiched between aluminum face
sheets), three main support beams, and six-stringers. Drogue mounting lugs are part of the main
support beams and mate with drogue mounting pads in the LM tunnel. One of the drogue pads
contains a latching mechanism that provides rotational constraint and can be actuated
by the crewman during installation or removal of the drogue from either the CM or the LM
side of the transfer tunnel. that’s the background on the actual equipment,
so I’m now going to show the sequence of events and how the docking system actually
works. Prior to flight, the ground crew places each
of the 12 latches in the cocked position by two pull strokes of the latch handle.
When the spacecraft is in earth orbit, the crew extends the docking probe in preparation
for docking with the LM and Saturn booster during translunar flight.
The actual docking maneuver occurs shortly after translunar injection and begins with
the separation of the CSM from the S IVb. once the command module is free, a maneuver
is executed to align the CM and LM docking ports in preparation for docking.
The pilot aligns the image superimposed on the Optical sight with the target sight situated
on the LM. The crew then initiates a closing velocity
so that the probe head contacts and engages with the drogue.
You can see here the probe capture latch assembly protrude through the Drogue and engage the
3 latches. the crew observes an indicator to confirm
capture latch engagement prior to initiating the probe retract system to pull both spacecraft
together. The crew initiates the retract command which
then pulls the Docking ring and LM tunnel together.
Now The 12 docking ring latches are automatically actuated when the LM tunnel ring depresses
a trigger on each of the latches. As the tunnel depresses the latch trigger, the hook and
handle are released, and this allows them to rotate to a position where the hook is
over the docking ring lip. Ring latch engagement provides a pressure-tight,
structurally rigid connection between the spacecraft to allow crew ingress,
the tunnel and the LM are pressurized by opening a valve in the CM forward hatch.
One crewman then removes the forward hatch, verifies engagement of the 12 latches, connects
the electrical umbilical, verifies engagement of the probe extend latch, vents the gas from
the probe retract system, and reinstalls the forward hatch.
The LM is then separated, and the docked spacecraft continue their journey to the moon
Prior to spacecraft entering into lunar orbit, the crew must enter the LM.
the probe and the drogue must all be removed
The Probe consists of a manual capture release
handle, which detaches the probe head, and has a ratchet assembly for probe removal.
After the LM checkout activity is completed, the two crewmen re-enter the CM, and the removed
hardware is reinstalled in the tunnel. but is not electrically connected.
in preparation for lunar descent, the hardware is removed again and the 2 astronauts enter
the lunar module. The probe and the drogue are then re­installed,
his time, however, the drogue is reinstalled from the Lunar Module side.
the probe is pre­loaded to 6000 pounds of tension to allow the subsequent unlatching
of the 12 docking ring latches and to maintain tunnel pressurization. the forward hatch is
then installed The Lunar Module Is then able to undock and
land on the moon. On return from the moon, the docking procedure
is carried out again. This time the Lunar Module pilot also can also align the Lunar
module by aligning with a lit target in the command module window.
The docking procedure and capture happens in the same order as previously carried out.
When it is time to separate the two spacecraft permanently, all the equipment is passed into
the Lunar Module and Both hatches are secured. This time however the Final separation of
the docking ring is accomplished by a pyrotechnic initiation of an MDF, that’s a mild Detonating
fuse, this explosively severs the ring structure. And that’s it. The lunar module will decay
in its orbit and eventually crash onto the moon's surface. The only one to survive is
Apollo 10’s Lunar module called Snoopy. This is currently in orbit around the sun
and is due to pass 4 million miles from Earth on July 10, 2037. Get your telescopes out.