How cool are the Tims?

Luca Parmitano at European Astronaut Centre answering #AskLuca questions on Twitter. Credits: ESA–J. Harrod CC BY SA IGO 3.0

We had this blog entry prepared and were about to publish just when Friday’s spacewalk was terminated, so it got forgotten…

With ESA Luca Parmitano answering questions on Twitter (using only his mobile phone!), one question keeps returning: do astronauts feel the temperature change when going from darkness into sunlight every 45 minutes? The question is relevant as the temperature difference between sunlight and shadow can be up to 300°C, so obviously the astronauts need some kind of protection.

Spacesuit controls with temperature control on the right. Credits: Wikipedia

Tim Peake and Tim Kopra are wearing NASA-issued Extravehicular Mobility Units that are nothing less than complete spacecraft with their own battery power supply, lighting and temperature control. The suit is water-cooled with water looping from the ankles to the shoulders. Each astronaut can turn a knob to change the speed at which the water circulates – the faster it circulates the cooler the astronaut will be. The dial has a scale from 1 to 10 and Luca reports setting it to 3 for the most of his spacewalks in 2013.

Some astronauts on a spacewalk are constantly fine-tuning their spacesuit thermostats each time they go from sunlight to darkness and back. They also need to regulate the temperature depending on the work they are doing, heavy work or exercise demands a cooler working environment.

How does this feel? Luca says that it is a gradual change in temperature up to 15°C. Luca compares it to how you regulate and feel temperature changes while skiing. You need to keep warm when you are waiting for someone in the shade of a mountain, or waiting in a ski lift, but trekking up the mountain in deep snow in sunlight or entering a heated restaurant you would often open your jacket to let the heat escape and keep yourself at a nice temperature.

Luca Parmitano at European Astronaut Centre answering #AskLuca questions on Twitter. Credits: ESA–J. Harrod CC BY SA IGO 3.0