How NASA Reinvented The Wheel - Shape Memory Alloys

Summary

This Real Engineering episode explores the challenges of designing Mars rover wheels, highlighting the innovative use of Nitinol, a shape memory alloy, to create flexible yet durable tires that can withstand the harsh Martian environment. The video also promotes a design competition for young engineers to reimagine Mars transport vehicles.

Takeaways

• 🌍 The Mars rover's wheels have been one of the biggest technical difficulties encountered on the mission due to the rough Martian terrain.
• 🛠️ The Mars rover's wheels are made of solid aluminum, which is stiff enough to support the rover's weight but is susceptible to damage from sharp rocks.
• 🔍 NASA underestimated the roughness of the Martian terrain, leading to damage to the rover's wheels, which are only 0.75 millimeters thick, similar to a credit card.
• 🏎️ The Mars rover's top speed is just 0.15 kilometers per hour, yet this slow pace is enough to cause damage to the aluminum wheels.
• 🔄 The Mars rover's wheels need to be light to reduce launch costs, stiff to support the rover's weight, and capable of maintaining traction on unpredictable terrain.
• 🏆 The Opportunity Rover holds the record for the longest journey on an extraterrestrial body at 45 kilometers, followed by the Curiosity Rover at 20 kilometers.
• 🚀 The Mars Rover project cost 2.5 billion dollars and uses a nuclear reactor for power, highlighting the high stakes and investment in its success.
• 🔧 Engineers are seeking alternative wheel designs for future Mars rovers that can better withstand the harsh conditions and extend the mission's life.
• 🌡️ Traditional rubber tires are not suitable for Mars due to the extreme low temperatures that would make them brittle and the UV radiation that would degrade them.
• 🔄 Nitinol, a nickel titanium alloy with shape memory properties, is being considered for future Mars rover wheels due to its ability to deform and then return to its original shape when heated.
• 🏆 Goodyear, who developed the original Lunar wheel, was awarded the R&D 100 award in 2010 for developing a spring tire using Nitinol, which could be a game-changer for Mars rovers.

Q & A

What is the main topic of the Real Engineering episode described in the transcript?

The main topic of the episode is the engineering challenges faced in designing the wheels for Mars rovers, with a focus on the innovations and materials used to overcome these challenges.

What is the Mars rover's top speed on flat, hard ground?

The Mars rover's top speed on flat, hard ground is 0.15 kilometers per hour.

Why were the wheels of the Mars rover a significant technical difficulty in the mission?

The wheels of the Mars rover were a significant technical difficulty because they had to be stiff enough to support the rover's weight, light to reduce launch costs, and maintain traction on unpredictable Martian terrain, all while accruing substantial damage from the rough terrain.

What is the current record for the longest journey on an extraterrestrial body held by?

The current record for the longest journey on an extraterrestrial body is held by the Opportunity Rover, which traveled 45 kilometers on Mars.

What material are the wheels of the Mars rovers made of, and why is it problematic?

The wheels of the Mars rovers are made of solid aluminum, which is problematic because it is not thick enough to withstand the sharp rocks and rough terrain on Mars, leading to damage and potential wheel failure.

Why are rubber air-filled tires not suitable for Mars?

Rubber air-filled tires are not suitable for Mars due to the extremely low temperatures that would make rubber brittle and ineffective, as well as the degradation caused by UV radiation on the Martian surface.

What is the material used in the new spring tires that could potentially be used for future Mars rovers?

The new spring tires use a material called Nitinol, a nickel titanium alloy with shape memory properties that allows it to deform and then return to its original shape when heated.

How does the shape memory property of Nitinol work?

Nitinol has a unique crystal structure called martensite that can accommodate deformation easily. When heated, it forms austenite, which resets the crystal structure, and upon cooling, it remembers and returns to its original shape.

What is the significance of the transformation temperature in Nitinol and how can it be tailored?

The transformation temperature in Nitinol is significant because it determines the temperature at which the material transitions from martensite to austenite and vice versa. It can be tailored by adjusting the titanium content, with higher titanium content increasing the transformation temperature.

How does the super elasticity property of Nitinol benefit the Mars rover wheels?

The super elasticity property of Nitinol allows the Mars rover wheels to deform under stress and then recover their shape without the need for external heat, making them more durable and capable of withstanding the harsh Martian environment.

What is the purpose of the design competition mentioned in the transcript?

The purpose of the design competition is to encourage young engineers to brainstorm innovative and creative designs for a new Mars Transport Vehicle that improves on previous designs, with the top prize winner having their idea developed into a 3D model and gaining work experience at the Briggs Automotive Company.