29-04-2021 | | By Robin Mitchell
Recently, the Ingenuity helicopter on Mars performed its first successful flight demonstrating that flying craft could be the future of space travel. What is Ingenuity, what electronics help to make it possible, and what challenges does it face?
The Ingenuity helicopter is a prototype helicopter transported to Mars by the latest Nasa Rover, Perseverance. The project's goal was first to prove that a helicopter could operate on Mars, and from there, go on to prove that rovers of the future could be used far more efficiently with the use of drones.
Rovers on extraterrestrial bodies face numerous challenges that can make using them very difficult. The first challenge faced is that such bodies are almost always millions of mile away, and as such, signals take time to reach the rover. This means that any actions have to be carefully planned out and sent as a series of commands instead of using real-time driving.
The second challenge faced by such rovers is that the area being landed is unknown, and driving the rover into the wrong area could effectively end the mission should the rover get stuck. As a result, rovers have to move in very small increments with researchers studying photos and data to determine the best path.
The third challenge faced by rovers is that when the two above challenges are combined, the rover cannot explore all areas of interest, and instead has to prioritise. This leads to potential discoveries not being made, and therefore reducing the use of the rover.
Therefore, NASA decided to solve some of these challenges with the use of a helicopter called Ingenuity. The idea behind the drone is that it can be sent out at a great distance and provide mapping and points of interest. From there, researchers can examine many areas first before dedicating a rover to explore the area.
The Ingenuity helicopter weighs only 1.8KG, has a power rating of 350W, and a rotor diameter of 1.2M. The construction of the helicopter mostly relies on carbon fibre as this provides excellent strength to weight ratio. However, the electronics powering the rover are rather peculiar and unexpected.
According to Tim Canham, a senior software engineer for JPL, NASA probes and devices are classed between A to D with A being the highest priority and requiring the least risk. At the same time, D indicates a low priority and high risk. The Ingenuity has a rating of Class B which means that it has a high priority, but the need to reduce risk is not as extreme as a Class A device. An example of a Class A device is the Perseverance rover itself, as this MUST work.
However, the Class B rating of the helicopter allowed the development team to use less high-end electronics. While critical components were chosen for their radiation-hardened abilities, many other components are “off-the-shelf”, with some parts even being sourced from SparkFun.
The main processor that drives the helicopter is a Qualcomm Snapdragon 801which is commonly found in cellphones. While this may seem like a basic microprocessor, the truth is that the CPU of the helicopter is orders of magnitude faster than the rovers main processor. This is because the processor used on the rover needs to be a proven design, and the only way such a part can be proven is with decades of use without fail.
Navigation of the helicopter is done using a VGA monochrome camera, a laser altimeter, and a cellphone-grade IMU. Interestingly, the magnetic field on Mars is extremely weak and random meaning that magnetic orientation and navigation is not possible. All navigation done on the helicopter uses visual data for mapping. Instead of storing an entire map of the area, it uses the difference between visual frames to determine its direction and position.
The operating system found on the helicopter is based on Linux, and this system has been previously used in other missions including CubeSats. Furthermore, the software is open-source and available on GitHub for anyone to look at and use. https://github.com/nasa/fprime
Probes sent beyond Earth face challenges that would put most manufactured devices to shame. From extreme radiation to intense G forces, any electronic system on a spacecraft has to withstand the extremes of extremes.
It is these extremes that see many spacecraft rely on very old technology that has been proven for years. For example, controls in NASA crafts has typically been levers, buttons, and hardened screens, and this caused a shock when SpaceX did its first flight with a futuristic craft using touchscreens and mood lightning.
Above all else, reliability is the most important feature in any component used. The expensive nature of spacecraft means that failure is not an option, and a failure can set back projects for more than a decade. Therefore, a designer who wants a guaranteed success will use processors, RAM, and transistors designed in the mid-1990s.
Simply put, designing a spacecraft requires a design to take massive impacts, be impervious to radiation, survive in extreme temperatures (well beyond industrial levels), never experience a system fault without some kind of backup system, and then survive re-entry.