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Selecting a lunar landing site

Published onMar 31, 2020
Selecting a lunar landing site
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In this activity, you’ll learn how NASA chose the Apollo mission landing sites when they went to the Moon. Once you understand all the important factors in landing site selection, you’ll have the chance to make your own lunar lander and landing site to attempt your own landing!


Activity Summary

Background and Discussion - 20 minutes

  1. The Apollo 11 Moon Landing

  2. Landing Site Selection Factors

  3. Mission Design and Logistical Considerations

Activity: Attempting your own moon landing - 30 minutes

Objectives

The student will:

  • Learn about the geography of the moon

  • Learn which factors to consider when choosing a landing site on the lunar surface


Background: “The Eagle has Landed”

  1. The Apollo 11 Moon Landing

When astronauts first went to the moon, they had to complete a mission no one had tried before. While building the rocket to get to the Moon was hard, the astronauts were especially worried about the process of landing on the Moon. Here on Earth, airplane pilots know exactly where to land because we’ve already built runways or helipads telling them where to go, and have a pretty good idea what the surface of the Earth is like in terms of soil, mountainous regions, etc. But when the Apollo astronauts were training to land on the Moon, the only thing they could study were pictures taken by Lunar Orbiters.

Check out this video by NASA explaining how important, and difficult, the Apollo 11 landing was:

The Moon Landing Was a Disaster...Almost
  1. Landing Site Selection Factors

NASA had a lot of factors to consider when choosing a landing site, mainly:

  • Smoothness and approach path - choosing an area with relatively few craters without any large hills, cliffs, or other obstacles in the way.

  • Propellant - making sure they used the least amount of fuel when landing.

  • Free-return - making sure they could re-dock with the orbiting Apollo spacecraft

  • Lighting - making sure the sun would provide good visibility.

  • Slope - making sure the landing area wasn’t too steep.

Take a look at this image of the Moon. What features do you notice?:

The moon’s surface has three major features: craters, maria, and highlands.

  • Craters are formed by meteor impacts on the Moon’s surface. In general, the density of craters on a surface corresponds to the age of that surface (density = # of craters / area of surface). Older surfaces have many more craters, while younger surfaces have less craters.

  • Maria are the dark regions of the Moon, and believed to be remnants of lava flows that travelled through cracks on the moon’s surface and eventually cooled. Maria have very few craters.

  • Highlands are the Moon’s mountainous regions, which are older and lighter in color than lunar maria. The highlands are made of a rock called anthorosite, which forms from slow moving lava flows.

NASA chose five candidates for a landing site, shown on the map below (you can also see the actual landing sites of the Apollo missions on this interactive 3D map):

Based on what you’ve read above, why do you think these sites were chosen?

Something else the astronauts had to consider was the impact of the atmosphere on the attempt to land.

Watch this video of Commander David Scott dropping a hammer and a feather on the Moon. What do you notice?

Hammer vs Feather - Physics on the Moon

What would happen if you dropped a hammer and feather on Earth?

Try it at home: take a regular piece of paper and let it fall horizontally (so the paper is horizontal to the floor). Now, crumble it up and let it fall from the same height. Does it fall faster or slower? Why?

The reason objects on Earth fall at different speeds is due to something called drag. Drag is a a force experienced by an object in free fall due to its interaction with air molecules, which slows it down. On Earth, we have an atmosphere composed of gasses like Oxygen, Nitrogen, and Carbon Dioxide. The Moon doesn’t have an atmosphere.

Take a look at how astronauts returning from the Moon land on Earth:

Apollo 15 Splashdown

Would this work on the Moon? Why or why not?

  1. Mission Design and Logistical Considerations

There are four primary stages of a moon mission: launch, cruise, EDL (entry, descent, and landing) and return. Each comes with its own unique challenges, and choosing a good landing site can make each stage easier to accomplish.

Check out this video explaining the Apollo 11 mission stages:

NASA Apollo Animation

Launch and Cruise

During launch and cruise, the spacecraft leaves Earth and enters into its trajectory to the Moon. It is necessary to choose a landing site that can be approached easily from this trajectory without using a lot of fuel. For example, if the spacecraft path approaches the moon’s equator, it will be very difficult and resource-intensive to land at the moon’s poles!

Entry, Descent, and Landing

During Entry, Descent and Landing (EDL), the spacecraft enters the moon’s gravity field, descends to the surface, and lands on the ground. This is the most challenging step of a moon mission. There cannot be anything obstructing the path of the spacecraft on it’s way down to the surface (like a mountain!), and even cliffs and craters can be dangerous if there isn’t enough fuel left to fly over them. It is important that the landing site be relatively flat and free of debris to make it easier for astronauts to walk and prevent the lander from being damaged.  Finally, good lighting from the Sun helps astronauts see where they are going.

Return

Return is the last step. The spacecraft takes off from the moon’s surface and returns to Earth. In an emergency, the spacecraft should be able to take off from the landing site and enter what is called a free-return trajectory. In this trajectory, the spacecraft is pulled back to Earth without needing to fire the engines. To ensure the safety of the astronauts, any landing site selected should be able to easily enter the free-return trajectory. 


Mission: Attempt your own Moon Landing!

Modified from “Make an Astronaut Activity” by NASA JPL: https://www.jpl.nasa.gov/edu/learn/project/make-an-astronaut-lander/

Materials, Resources and Prep

  • An small open area or hallway to set up a mock landing site, approximately 2 x 2 ft space

  • Scissors

  • 1 piece of stiff paper or cardboard, approximately 4 x 5 in

  • 1 paper or plastic cup

  • 3 index cards, 3 x 5 in

  • 3 rubber bands

  • 8 plastic straws

  • Tape, 1 meter

  • 10 mini marshmallows (optional)

  • A phone with camera to capture video (optional)

Design your lander

  • Using the materials listed in the “Materials and Resource Prep” section, brainstorm a design for a lunar lander!

  • Ask: “What kind of shock absorber can you make from these materials to help soften a landing?”

    • Marshmallows, folded index cards and straws can be used to soften the landing of your lander. 

  • Ask: “How will you make sure your lander doesn’t tip over as it falls through the air?”

    • Distributing the weight evenly on your lander helps keep it upright

 Build your lander

  • Put your spacecraft together. Attach the shock absorbers to the cardboard platform.

Make a moonscape

  • In your open area, use some objects from around your house to make obstacles for your lander. For example, use a box to make a cliff, or Legos to make lunar rocks. 

  • With tape, a sticker or a piece of paper, mark where in your moonscape your landing site is. 

Test!

  • Pick up your lander and move it over your moonscape at a height of one foot until it’s over your marker. Drop your lander onto the marker. Does anything prevent your craft from landing? Did your craft get damaged during landing? 

  • Now removing some of the obstructions from your site. Try landing your craft again. Was it easier to land your craft this time? Why? Keep changing up your moonscape and record which ones made landing the easiest and which ones made landing the hardest. 

Share-out!


Conclusion

Landing on the Moon is a difficult task! We still don’t know a whole lot about the texture and exact composition of the soil and terrain on the Moon, and as we plan for our return to the lunar surface, we’re going to have to solve a lot of the challenges you just learned about. Discuss ways we could use new technologies (apart from the Apollo 11 Lunar Lander) to land on the Moon in new ways. What if we made a different kind of lunar module? What if astronauts didn’t even use modules to reach the surface? What kinds of problems would they face?

Enter our K-12 Lunar Habitat Challenge!

As part of MIT’s larger return to the moon, we’re running an online K-12 challenge, and encourage you to submit an entry! The challenge is to design a lunar habitat and submit your designs to our team by May 15, 2020. The winners of the challenge will be selected for a special prize! Details of the competition and how to enter can be found here.

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