Aerodynamics for Mark Rober's Record Egg Drop

Summary

In this video, Mark Rober and Joe Barnard collaborate on an ambitious project to drop an egg from 100,000 feet and recover it safely using a rocket with movable fins. They discuss the technical challenges, including landing pad design, weather balloon simulations to predict egg trajectory, and aerodynamic simulations for fin control. Despite setbacks and the realization that more work is needed, they reflect on the importance of asking the right engineering questions and consider alternative methods to achieve their goal.

Takeaways

• 🚀 Mark Rober collaborated with Joe Barnard to create a video on achieving the world’s highest egg drop from 100,000 feet.
• 🥚 The goal was to safely drop and land an egg without it cracking by using complex guidance and control mechanisms.
• 🛏️ Initial landing pad idea involved foam pads to cushion the egg, which was proven viable for terminal velocity impact.
• 🎈 A weather balloon was used to calculate the dispersion range, ensuring the egg would drop within a 1 km range of the landing pad.
• 🦾 The team designed a high-altitude re-entry vehicle with movable fins, named HARVER (High Altitude Re-entry Vehicle for Egg Recovery), to guide the egg safely.
• 💨 Using rocket fins for steering involved complex aerodynamic simulations, requiring validation through computational fluid dynamics (CFD) and real-world tests.
• 🚗 Joe tested the fin design by mounting a test jig on his car and driving at highway speeds to simulate airflow and validate CFD results.
• 📉 The results showed good alignment between CFD and real-world data, though some errors were attributed to test conditions and vehicle positioning.
• 🛠️ Several test flights were conducted to refine control systems, though challenges with dynamic stability and fin effectiveness led to flight failures.
• 🤔 After much consideration and testing, Joe realized that continuing with this design would require more wind tunnel time and redesigns, prompting exploration of alternative methods.

Q & A

What was the primary goal of the project involving Mark Rober?

The primary goal was to perform the world's highest egg drop from 100,000 feet and recover the egg safely without it cracking.

Why did they calculate the egg’s terminal velocity?

They calculated the egg's terminal velocity, which was about 30 to 35 meters per second, to determine the impact speed and design a landing pad that could cushion the egg without breaking it.

What was the purpose of using a weather balloon simulation tool?

The weather balloon simulation tool was used to calculate the regular dispersion of a balloon launched to 100,000 feet and estimate the egg's landing area with a margin of error of about one kilometer.

How did they plan to guide the egg back to the landing pad?

They planned to use a rocket with movable fins to steer the egg back toward the landing pad, employing similar principles to the Falcon 9 rocket's grid fins.

What vehicle was designed for the egg drop and why was it named 'Harvard'?

The vehicle was called 'Harvard,' which stands for High Altitude Re-entry Vehicle for Egg Recovery. It was designed to guide the egg safely back to the ground using movable fins and simulations.

What challenge did they face with the egg’s impact speed?

The egg’s terminal velocity was about 35 meters per second, but the rocket was moving at around 110 meters per second above the landing pad. This made the impact speed vs. accuracy a key challenge.

What role did computational fluid dynamics (CFD) play in the project?

CFD was used to simulate how the rocket's fins would generate side forces during descent. The team compared these results with real-world tests to ensure the simulations were accurate.

How did the team test their fin design in the real world?

They built a fin test rig using 3D printed parts, mounted it on the hood of a car, and measured the side forces at different fin deflection angles while driving to compare with CFD results.

What went wrong during the first flight test of the Harvard vehicle?

The vehicle failed during the first flight test due to a rogue negative sign in a fin movement constraint function, which caused the fins to behave incorrectly.

What realization did the team come to after consulting with aerodynamic engineers?

The team realized that completing the project would require more work, such as wind tunnel testing and further simulations. They concluded that while the project was within their capability, it needed more resources than initially anticipated.