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Apollo 11 was the first mission to land on the moon. Michael Collins, Buzz Aldrin, and Neil Armstrong lived in the command module during the July 1969 mission. Aldrin & Armstrong also used the Lunar Module, nicknamed the “Eagle”, to actually descend to the surface of the moon. A service module was also part of the complete Apollo spacecraft, which contained the main propulsion system and consumables. All parts of the complete Apollo spacecraft were launched atop the Saturn V rocket.
If you want to see more objects and artifacts from the Apollo 11 Mission, see this National Air and Space Museum collection link.
Portrait of (left to right) Commander Neil A. Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin "Buzz" E. Aldrin, Jr.
Apollo 11 Command Module “Columbia” - currently on display in the Boeing Aviation Hangar at the Steven F. Udvar-Hazy Center in Chantilly, VA
But space is a big place! How did the Apollo spacecraft navigate the great expanse of space?
Katherine Johnson
Katherine Johnson
Navigation for the Apollo 11 Mission all started off with performing trajectory analysis. Katherine Johnson calculated the trajectories for the 1969 mission to the moon. You may have heard about her from her work as a “computer” at the National Aeronautics and Space Administration (NASA), which was formerly the National Advisory Committee for Aeronautics (NACA), with the Mercury Missions as depicted in the popular breakout movie Hidden Figures. Click on Katherine’s portrait to learn more about her personal life and all of her amazing contributions to some of NASA’s most important missions.
What is a trajectory?
What is a trajectory?
What is a trajectory? Well, basically, it’s a path mapped out for an item in space. The idea is to have clear beginning and ending points, and the orbits (including entrance and exit into and out of orbit) of said item included. These paths are based on gravitational-attraction properties of the masses in space. Learn more about trajectories at this link from NASA.
Apollo 11 Trajectory
Apollo 11 Trajectory
So, what did the trajectory look like for the Apollo spacecraft? What do you notice about this trajectory? What things were calculated? What specific information is included? Can you find the points of exit and entrance from the orbits?
You can click on the trajectory map to visit the National Air and Space Museum page with the image in order to better zoom in and view the map.
It’s great and all to have a plan that was well calculated, but how do the astronauts make sure they stay on track? That’s where navigational and control tools come into the picture.
Primary Guidance, Navigation, & Control System
Primary Guidance, Navigation, & Control System
The Primary Guidance and Navigation System on the Apollo was made up of three navigation systems:
Inertial Guidance System
Optical Navigation System
Command Module Computer
Check out the diagram of the Guidance, Navigation, and Control systems. What do you think the role of each of these systems are? How do each of the parts play into the overall system?
Inertial Guidance System
Inertial Guidance System
First, let’s look at the role of the inertial guidance system: This part of the system received data from accelerometers (sensor that measures acceleration acting on an object to determine orientation), gyroscopes (measures orientation and angular velocity), ground tracking stations on earth, and the astronauts' observations, sending it to the computer in order to compute needed adjustments. Can you find these items on the Guidance, Navigation, & Controls diagram? The photo shows a prototype of an amplifier oscillator that was part of the vibrating string accelerometer accelerometer used on the Apollo 17 mission. Click on the photo for an explanation of how it works.
Think about and research the definition of “inertial guidance”. What is this system focused on measuring and adjusting?
Amplifier Oscillator consisting of two ceramic electronic modules
Apollo Sextant Eye Pieces - currently on display at the Time and Navigation exhibition at the National Air and Space Museum in Washington, DC
Optical Navigation System
Optical Navigation System
Second, let’s look at the role of the optical navigation system. This system consisted of a telescope and a sextant. Can you find these items on the Guidance, Navigation, & Controls diagram? This sextant looks different than the sextant and octant used by Charles Wilkes or Anne Morrow Lindbergh or the sextant created by Jesse Ramsden that we have learned about in the other missions in this artifact immersion. While this instrument does not look like a traditional sextant, the basic procedure is descended from centuries-old methods used by navigators at sea and in the air.
What is the difference between a telescope and a sextant? How are they each used? What are the parts and pieces needed within the Apollo sextant? How have sextants/octants progressed over time now that we have learned about multiple types?
Star Charts
Star Charts
In conjunction with these optical navigation tools, star charts were used in order to know what information to input into the Apollo Guidance Computer to make necessary adjustments based on their current and desired positions. To determine position in space, an Apollo astronaut located a specific star using a single-power, wide-field telescope and then took measurements using a sextant.
What constellations or stars can you find that you recognize? Can you find them in your night sky? Would you be able to tell directions based on the location of those stars? Download and play with Stellarium, which can help you locate objects in the sky at any time on any date in any location!
Star chart used by Michael Collins, the Command Module Pilot, during the Apollo 11 mission
The crew also used a world map with an overlay of their orbital paths. How do you think this was used?
Map, Earth with Overlay, Apollo 11
Command Module Computer
Command Module Computer
The Command Module Computer would provide necessary information on the angles and navigation based upon input from both the interior and optical tools. For example, The sextant readings were automatically fed into the Apollo Guidance Computer—the electronic equivalent of the almanacs and mathematical tables sailors once used, allowing for necessary course corrections.
The overall guidance and navigation system was developed, built, tested, and evaluated at the MIT Instrumentation Laboratory in Cambridge Massachusetts.
Guidance & Navigation System, Command Module, Apollo, Test Article
Want to learn more about what it took to navigate to the actual surface of the moon? Click here to find out!
What would you like to explore next?
What would you like to explore next?
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