In the simplest terms, a helicopter is able to fly by generating enough lift with its spinning rotors to offset its own weight, enabling the craft to take flight.
A key part of that ability is the general condition of the air in which the machine is trying to fly, with sea level flight involving much denser air than at higher altitudes. For helicopters, denser air is typically a good thing, making it far easier to get lift than in the atmospheric conditions found high above earth.
But what if you wanted to fly a helicopter on another planet 200 million miles away?
You would turn to research done by Assistant Professor James Coder. Or at least that’s what NASA did in preparing for its most recent mission to Mars, which included Ingenuity, a helicopter probe that has been used to explore the planet.
“One of the biggest challenges on Mars is that the air density is very low, about what it would be at 100,000 feet on Earth,” said Coder. “Landing and taking off a helicopter on Mount Everest is so challenging it has only been done once, and that’s less than a third of the altitude. When you have less air density, the only way to get enough lift is to spin the rotors faster—but you need to keep the blade tip speed slower than the speed of sound.”
But all flow is not the same, which is where Coder’s expertise comes into play.
There are two main types of flow: laminar and turbulent, which can generally be thought of as smooth and rough, respectively.
While that distinction might determine the enjoyment level of a helicopter ride on Earth, being able to accurately predict where the laminar flow is at its smoothest is critical in the harsh Martian atmosphere, where every bit of energy expended matters.
“Flying something on Mars is very, very hard,” said Coder. “There’s a lot that went into the design of that helicopter.”
And at least part of that design was based off research that Coder had conducted regarding flow over a number of years.
“I started noticing that NASA was using my model to help the design,” said Coder. “To know that what I’ve worked on over the last decade is making a difference—is used to help something fly on Mars—was rewarding.”
Ingenuity is still very much active, having completed more than a dozen missions to date and, thanks to a solar-powered rechargeable battery, should continue to provide insight and data for some time to come.