Physics KS3 / GCSE: Demonstrating heat shield material
Kevin Fong explains that a space capsule like the Soyuz heats up on re-entry not from friction with air molecules, but because it compresses the air in front of it.
He demonstrates this by compressing the air in a glass tube using a plunger and the increase in air temperature is sufficient to ignite some cotton wool in the bottom of the tube.
The heat shield on the Soyuz capsule is made from a solid silica foam which is mostly air and thus has a very low thermal conductivity.
A cube of this heat shield material is removed from a kiln at 1100 degrees Celsius and after cooling for only a matter of seconds, Kevin picks it up with his bare hands.
It is still red hot in the centre, but its material properties prevent the heat from conducting out to the edges of the cube, which have already cooled down.
This clip is from the Royal Institution Christmas Lectures 2015.
Key Stage 3
After watching this clip, you could ask students to research some of the materials that have been developed for space programmes around the world.
They could investigate what these materials are used for now.
Key Stage 4
Students can research materials with low and high thermal conductivity and complete calculations on the amount of thermal energy transferred across them when one side’s temperature increases to that typical of re-entry.
This clip will be relevant for teaching Physics.
This topic appears at KS3 and in OCR, Edexcel, AQA, WJEC KS4/GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland.