The Apollo Spacecraft was an incredible machine that allowed astronauts to walk on the moon. It was split up into 3 parts, the Command Module, the Service Module, and the Lunar Module. Later on, we'll talk about what each module does, but first, let's talk about the launch vehicle that gets us into orbit. The Saturn Five rocket. Each mission was launched from Cape Canaveral in Florida. Mission Control was in Houston, Texas. The Saturn Five rocket was 363 feet tall. Just to get a good size comparison, here is the size of a person, and here is the size of a Boeing 747. The Saturn Five was split up into 3 stages; they referred to each stage by a technical name. The first stage was called the S-1C and was powered by five F1 rocket engines. The second stage was called the S2 and was powered by five, slightly smaller, J2 rocket engines. The third stage was called the S-4B and was powered by only one J2 rocket engine. The actual spacecraft stored up at the top of the rocket stages. Here is the Lunar Module, which would land on the Moon. During the launch, it was protected by four panels, known as the spacecraft Lunar Module adapter. The Service Module contains the engines necessary to enter and leave lunar orbit, as well as fuel cells and other electrical components. The Command Module is where the 3 astronauts spent most of their time. At the very top, you'll find the Launch Escape System. In the event of an emergency, it would carry the Command Module safely away from the rocket. The structure you see next to the Saturn Five is called the Launch Umbilical Tower. You'll notice 9 service arms provide access to the Saturn Five. On the day of the launch, the 3 astronauts ride an elevator to the top service arm. The White Room is where they enter the Command Module. Four of the service arms are moved out of the way before the launch. The First Stage ignites 8 seconds before the Saturn Five leaves the ground. As the Saturn Five starts to rise, the remaining 5 service arms quickly rotate to get out of the way. It takes about 12 seconds for the rocket to completely clear the tower. As the Saturn Five picks up speed, the astronauts will feel as much as 4 G's, or 4 times the amount of gravity pressing them into their seats. The First Stage shuts off at 2 minutes 42 seconds at a height of about 42 miles. Explosive bolts detonate, releasing the first stage, and letting it fall back down to the Atlantic Ocean; shortly after, the second stage fires up. We're high enough in the atmosphere now, that the Launch Escape System is no longer needed. The second stage shuts off at 9 minutes and 12 seconds at a height of 109 miles. The third stage fires up for a short amount of time to get the astronauts into a Parking Orbit of 118 miles. It shuts off at 11 minutes and 39 seconds, but does not detach yet. One of the hardest parts of the mission is over, but the adventure doesn't stop here. We are in a parking orbit 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 toward 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 turnaround. 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 ellipse heading 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 flies. 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 going, It’s now time to enter the 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 lose 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 orbit 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 its 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 was time to take off from the surface. Let’s talk about the Lunar Module a little more. It was split up into two stages, The Descent Stage got us safely to the surface, but now its dead weight and will be left behind on the surface of the Moon. The Ascent Stage has it’s propulsion system, which is what gets the two Astronauts safely back into orbit. Don't forget about our one lonely Astronaut, who's still orbiting above us in the CSM. What I'm about to explain is called Rendezvous and Docking. I'm going to change the Moon's scale here, so we can show this a little better. Lift, will need to happen at just the right time. The Ascent Stage fires up for about seven and a half minutes. This gets us initially back into Lunar Orbit. Several short engine burns happen over the next three and a half hours. It takes almost two orbits before docking can happen. In later Apollo Missions, they were able to do this in less than one orbit. After the LM and CSM are docked, all valuables are transferred to the Command Module. It's time to say goodbye to the LM Ascent Stage; it was either left floating in Lunar Orbit or intentionally smashed into the Moon. It's now time to head home; this is very similar to what we've done before. On the far side of the Moon, the Service Module Engine fires up for about two and a half minutes. This is called the Trans-Earth Injection. It was a three-day journey to get back home. Remember that the Service Module contains things like oxygen tanks and fuel cells; you can't go inside. This means that all three Astronauts are in the Command Module for the remainder of the journey. Sure hope no one gets claustrophobic. Once we're back in Earth Orbit, the Service Module is no longer needed. We started with the giant Saturn Five Rocket, and now the Command Module is the only part that returns safely to Earth. The climax of the whole mission is called Re-entry. All this time, the Service Module was protecting what's on the bottom side of the Command Module, the Heat Shield. Re-entering the Earth's atmosphere is dangerous because of the enormous heat it causes. The Heat Shield protects the Command Module for several minutes as it passes through the atmosphere. Down below, an Aircraft Carrier waits for the Astronaut's arrival. Once we get about two miles above the surface, the parachutes are deployed to slow us down even more. The hard part is over.
You must be logged in to post a comment.