Mars, Perseverance & the extreme cold challenge
Temperatures in space are a strange phenomenon, dependent on where you are in relation to the sun. On the ISS (International Space Station), the side facing the sun has recorded temperatures in excess of 121 degrees Celsius, whilst at the same time its opposite side reached -157 degrees Celsius. That is a temperature differential of 278 degrees across a distance of around 103 metres.
This changes quite dramatically as you move further out into the solar system, and by the time you reach Mars it’s generally just pretty cold (-60 to -200 degrees C), so anything us humans send up there needs to be built to withstand the most extreme cold. Modern spacecraft & satellites use a mix of advanced building materials and self-generating heat sources such as solar panels to keep the cold at bay, but one thing that poses a potential threat is that of ice.
The world recently witnessed the remarkable landing on Mars of the NASA Perseverance Rover, the latest project to provide us with a clearer picture of our neighbouring planet. There is substantial evidence of ice formation at the Martian Poles, a mixture of water ice and frozen carbon dioxide, and winds can distribute this material across the surface of the planet. This means the Rover has to be built to last, composed of cutting-edge metal alloys and plastics that are tested to withstand an alien climate (the average temperature on Mars is around -60 degrees Celsius, and at the poles in winter can drop to almost -200 degrees Celsius).
Storms are a regular occurrence on Mars, which ordinarily wouldn’t pose a threat to a robust vehicle such as Rover, but it’s impossible for the craft to be in constant motion as it needs to recharge for hours at a time. During these periods of inactivity it is possible for debris (including ice) to build up on or around the vehicle which could result in critical components failing to restart.
The fact that the above has, as far as we know, not occurred with any other Mars Rover to date may lead us to believe that icing is not a problem after all; however NASA invests huge sums to ensure that all of its space vehicles are ice-protected, indicating that they believe it is a threat. Of course if you have billions of dollars to hand it’s possible to focus on creating specialist materials and alloys that work despite ice build-up. However, the commercial scale up of such materials for real world applications could prove expensive and challenging.
The work that organisations such as NASA undertake is still useful however. It demonstrates different ways to approach the issue of extreme cold and ice management, allowing the development of cheaper, more innovative approaches to these problems back here on Earth. In the main there are two ways of tackling ice build-up; prevention (anti-icing) and cure (de-icing), and these solutions can be vastly different dependent on a range of factors. These include the application it which it’s used, environment, underlying causes etc.
De-icing systems have been well established for some time, used extensively at airports around the globe, but anti-icing – and in particular passive anti icing solutions – are relatively new. The challenge with anti-icing is how to deal with the problem in the first place. Heating surfaces is an option but need to be ‘always on’ to prevent re-freezing and are expensive. Coatings are another way of dealing with ice build-up, and there is a project under way that focuses on the development of a ‘passive’ solution.
The ICELIP project (commercial name Icemart®) – led by a consortium** of British-based organisations and funded by Innovate UK – is focused on the development and commercialisation of a new, passive ice-repellent coating that prevents ice formation and adhesion without the need for active ice-management. It incorporates functionalised nano particles into an aviation-certified film forming matrix and could provide organisations – including the world’s leading space agencies – with an answer to the challenges posed by ice accretion.
** TWI Ltd, CAV Systems, LSBU, Innvotek, BAE Systems, Promethean Particles, Opus Materials Technologies
