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  • Here we are in a parking orbit of 118 miles high.

  • And just how high is that? Let's take a look...

  • The Karman Line is generally considered to be the start of outer space.

  • The International Space Station orbits here.

  • Most satellites orbit between here...

  • ...and all the way out here.

  • It's called a parking orbit because

  • it's not high enough to stay in orbit for a long time.

  • But don't worry, we'll only be here for about 2 hours.

  • After orbiting the Earth 2 or 3 times and confirming all systems are good

  • it's time to ignite the 3rd stage one more time for about 6 minutes.

  • We call this the Translunar Injection.

  • This is what sends us away from the Earth and towards the Moon.

  • The S-IVB is now completely useless.

  • Remember that's the 3rd stage at the top of the Saturn V.

  • The Spacecraft Lunar Module Adapter panels detach

  • exposing the Lunar Module.

  • The Command and Service Module do a complete 180 degree turn around.

  • The Command Module must dock with the Lunar Module and pull it out.

  • In space, temperatures are a lot more extreme.

  • There was a real danger of parts of the spacecraft freezing

  • or other parts getting too hot.

  • To prevent this, the spacecraft was now put into a slow roll

  • so that there was an even heat distribution.

  • This was called Passive Thermal Control

  • but also nicknamed the "Barbecue Roll"

  • If we ignore the moon, this is what our flight path will look like

  • we're still orbiting the Earth but we're in the shape of an elipse

  • heading all the way out into the middle of nowhere.

  • With the Moon however, everything starts to make a little more sense.

  • At the time of launch, the Moon is about here.

  • During the next 3 days, their paths converge.

  • Just to be clear, this is the Earth and Moon drawn to scale.

  • I animate it out of scale so it's easier to see the flight paths.

  • So, the Moon's gravity changes where the spacecraft flys.

  • This is called a "Free Return Trajectory"

  • If something were to go wrong with the engines

  • the astronauts would still be able to get home.

  • On the other hand, if all systems are go

  • it's now time to enter Lunar orbit.

  • This is called the Lunar Orbit Insertion.

  • As the spacecraft passes behind the Moon

  • the Service Module engine was fired up for about 6 minutes to slow the spacecraft down.

  • At times like this they would loose contact with mission control

  • because they are on the far side of the Moon.

  • Unfortunately, this is where a lot of important events happened.

  • The guys at mission control just had to sit tight until the astronauts came around the other side.

  • Now it's time for the main event.

  • When the astronauts are ready

  • two of them get into the Lunar Module

  • and get ready to land on the Moon.

  • One of them stays behind and continues to oribit the Moon.

  • Side note: the Lunar Module was usually just called the LM.

  • And when the Command Module and Service Module were together

  • they were usually referred to as the CSM.

  • The LM now extends it's legs.

  • After making sure everything still checks out

  • the LM separates from the CSM.

  • The LM must get to a safe distance of about 2 miles away

  • before firing the descent engine.

  • The engines fire up for about 30 seconds.

  • This is called the Descent Orbit Insertion.

  • This puts the LM down to about 50 thousand feet above the surface.

  • Now the engine fires up again for Powered Descent Initiation.

  • The windows are initially pointed down.

  • But as we get closer to the surface

  • the windows will be facing forward

  • to give the astronauts a good view of the surface they'll be landing on.

  • The landing site needs to be on level terrain

  • and away from any big boulders.

  • There's a limited amount of fuel so the astronauts can't take too long to land.

  • And finally...touch down.

  • Now it's time to step down the ladder, say some historic words,

  • plant the American Flag, get some rock samples

  • and do some science.

  • After the Lunar stay was over, it's time to take off from the surface.

  • but, let's save that for part 3.

  • Thanks for watching and I'll see you in the next video.

Here we are in a parking orbit of 118 miles high.

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B1 US module lunar moon spacecraft orbit descent

How the Apollo Spacecraft works: Part 2

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    joey joey posted on 2021/04/26
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