Protect Your 'Eggstronaut': Build an Egg-Drop Lander
The egg-drop project is a classic and time-honored tradition in many science classes. The goal is usually to build a device that can protect an egg when dropped from a high location. This activity puts a twist on the classic project, motivated by real-world advances in space exploration. Can you build a reusable egg-drop lander that can survive repeated falls from the same height? Try this activity and find out
- Paper and pencil
- Raw eggs
- Paper towels for cleanup
- Assorted craft and construction materials such as popsicle sticks, paper cups, egg cartons, cardboard, etc.
- Cushioning materials like cotton balls, bubble wrap, Styrofoam®, etc.
- Tape and/or glue
- Optional: materials to build a parachute, like string and a plastic bag
- Area to drop the egg that will be easy to clean up in case the egg breaks
- Before you start, sketch a few design ideas for your egg lander. Think about the materials you have available, and how you could use them for different purposes. For example, what can cushion the egg and absorb energy when it hits the ground? What will provide structural support and hold your lander together? How could you build a parachute? Try to think of at least three different designs.
- If you have trouble getting started, a very basic design could consist of a small cardboard box or plastic food storage container, lined with a cushioning material, with the egg placed in the middle.
- Pick one of your designs and build a prototype. Make sure you can easily open the design to check if the egg is broken (e.g. don't permanently tape the egg inside a box).
- Place an egg in your lander and drop it from the height you decided on.
- Check if the egg is broken and check the lander itself for damage.
- Drop the lander again from the same height. Repeat this process, checking for damage each time, until the egg breaks or the lander falls apart and cannot be re-used. Keep track of the total number of drops it survives and write this number down.Do you notice any "weak spots" or parts of the lander that did not perform as you expected? How could you change the lander to improve its performance?
- Using your observations, build a second, improved prototype of your lander, and test it following the same process.Does your improved lander survive more drops than your original?
You might have found this project surprisingly difficult! Even if the egg survives the first few drops, you might start to see wear and tear on your lander. Taped or glued joints could start to come apart, materials like straws or popsicle sticks might start to bend or snap, and cushioning materials like cotton balls might become compacted, decreasing their effectiveness over time. Many successful traditional egg drop devices might intentionally rely on this behavior. If you only need to drop your device once, you can design it so that some of the materials break, absorbing energy and protecting the egg. That approach doesn't work if you want to re-use the device dozens of times!
In addition to protecting the egg, a successful re-usable device will need to minimize and distribute impact forces when landing. This means slowing the lander down as much as possible to begin with (e.g. by using a parachute), and spreading the impact out over a large surface or multiple points (as opposed to a single leg or corner, which concentrates the force all in one place). Testing and observing your design allows you to identify weak spots that can be fixed in future designs. This process of repeatedly designing, building, and testing, called iteration, is used by real engineers!
An egg drop project is a great way to learn about several classical physics concepts. When you raise an egg off the ground, it gains gravitational potential energy. When you drop the egg, the potential energy is converted into kinetic energy, the energy of motion. When the egg hits the ground, some of that energy is converted to other forms, like sound or heat, and some of it goes into breaking the egg! A protective device that can safely absorb some of this energy can help prevent the egg from breaking. The higher you start the egg, the more energy it will have — so you need to absorb more energy to keep it from breaking.
You can also think about this in terms of Newton's second law of motion. When the egg hits the ground, it rapidly decelerates (its speed changes). Objects that experience high accelerations or decelerations feel very high forces, which can cause them to break. If you can slow down the egg's crash landing by cushioning it (or adding a parachute, so it isn't going as fast to begin with), then you will reduce the force felt by the egg, and decrease its odds of breaking.
What does all this have to do with space exploration? For decades, NASA has designed vehicles that must protect their precious cargo—human astronauts (and robots!)—when landing on the Moon, Mars, or returning to Earth. Private companies like SpaceX are also entering the realm of space exploration, with a heavy emphasis on reusable vehicles, to help decrease the cost of space travel. So, instead of building a disposable egg-drop device and dropping it from increasing heights until it eventually breaks, in this project you built a reusable device that can survive dozens (or even hundreds) of falls from the same height.
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For Further Exploration
- Do this project with some friends! Everyone can build their own lander and compete to see whose can survive the most drops. Can you combine ideas and observations from individual designs to build an improved lander that outperforms the others?
- Launching materials into space costs money. The heavier something is, the more fuel it takes to launch, and the more expensive it gets! This means that a heavy lander might do a great job protecting the egg but would be very expensive to launch. Can you redesign your lander to be lighter and use fewer materials, but still protect the egg for the same number of drops?