Docking the Apollo Spacecraft was Surprisingly Complicated

Illustration for article titled Docking the Apollo Spacecraft was Surprisingly Complicated

How did that tiny, complicated spiky tip on the Apollo modules transform into a usable tunnel for astronauts after they docked? Through a bit of engineering ingenuity still in use today.


When we posted a photo from Apollo 17’s moon landing, Jeyl was understandably confused by the mechanics of how the command and service module hooked into the landing module:

Question. How does that very complicated looking tip turn into a tunnel for the astronauts to float through?

iCowboy provided a thoroughly detailed (and referenced!) answer:

That bit’s called the probe and fitted into a conical recess in the Lunar Module called the drogue. When centred, capture latches on the tip of the probe would click into place - this was known as ‘capture’. The Command Module would then order the probe to be retracted which pulled the two modules together. When fully retracted, twelve docking latches in the CM would click home on the sides of the LM’s docking tunnel to create a solid link.

Then the CM crew member would collapse the probe whilst the LM team did the same for the drogue and then they could go back and forth. There’s a glimpse of this process in Apollo 13 after the ship leaves Earth orbit - as if anyone needs an excuse to watch Apollo 13 again.

And if you want a real page turner - here is the official NASA report on the design of the docking system - enjoy!

brandb chipped in that they were, “Reportedly annoyingly complicated.” while Dogger1972 was more generous by calling it, “A nice bit of ingenious practical engineering.” Finally, okan170 gave us an update on the system’s evolution in modern-day spaceflight:

The probe on the front (the triangle on top), once latched to the other spacecraft, formed one solid hatch which is then pulled out of the tunnel. Soyuz still uses a similar system, but NASA has moved to androgynous docking systems to make things less complicated. These can have a removable hatch or removable petals.


As an added bonus reminder that history is a living concept, when we shared the history of pioneering aviation hero Sheila Scott, we uncovered her spiritual descendants. Scott was a founding member of Britain’s chapter of the Ninety-Nines, an advocacy group for women in aviation; both Flyinkelly and LovelyFeyd are modern-day io9rs and Ninety-Niners, with LovelyFeyd adding:

Her sense of style DOES appear to be impeccable, but having an airplane wrapped around you always makes you look stylish!


Fly strong and fly free, you fantastic space history buffs.

Top image: Apollo spacecraft showing off one of its many good sides. Image credit: NASA, as uncovered by maxvonian.

Contact the author at or follow her at @MikaMcKinnon.



The Constable

Anyone who’s played Kerbal Space Program knows how complicated docking is.

For the record, my docking procedure does not look like that. My docking procedure is always two pods in distantly far apart orbits as I cry over my keyboard.