# How fast were the Lunar Command Module and Landing Module traveling around the Moon when they reconnected?

I can't find this information online and am wondering how fast each were going around the Moon when they reattached to one another after the moon landing.

• In spaceflight "how fast?" always needs a "with respect to X" in order to be answerable. I assume you mean how fast is the pair traveling around the Moon so I've adjusted your wording. If you meant with respect to something else, or with respecte to each other then please feel free to edit further. Welcome to Space! – uhoh Jul 30 '19 at 1:00
• Sounds like a question for Apollo by the Numbers! – DrSheldon Jul 30 '19 at 1:04

At uhoh's suggestion, here's how to calculate the speed of the spacecraft. Let G be the gravitational constant, M the mass of the body we're orbiting (the moon) and r the radius of the orbit. In that case, the speed v is $$v = \sqrt{G * M / r}$$ If we use $$M=7.4*10^{22}kg$$ (mass of the moon) and $$r=1850 km$$ (100 km above the surface) we get $$v=1.63 km/s$$
• +1 looks great, thanks!! – uhoh Jul 30 '19 at 11:04