If you're building a spacecraft that's going to be landing on a planet that has an atmosphere, then you'd better equip it with a heat shield. Although some approaches to such shields can be heavy and/or complex, a University of Manchester PhD student has developed one that's simple, cheap and lightweight.

As a spacecraft plummets through a planet's atmosphere, the friction of the air against the rapidly-passing underside of the craft causes heat to build up. Heat shields serve to dissipate that heat, keeping it from damaging the spacecraft itself, while also helping to slow the spacecraft's descent by creating aerodynamic drag.

Presently-used shields include ones that inflate when needed, or that are mechanically deployed. Rui Wu, however, created a prototype that's a little different.

Made of a flexible, strong and heat-resistant material that folds down into a spiral shape when not in use, his shield automatically starts spinning like a samara-type tree seed when exposed to the onrush of air that a spacecraft would experience when dropping through a planet's atmosphere.

As it spins, centrifugal force causes its skirt-like sides to flare out, flatten and stiffen. This creates the drag needed to help slow the descent, while also providing a large protective surface for the dissipation of heat. No additional machinery, other than the shield itself, is required for its deployment.

"Since this prototype is lightweight and flexible enough for use on smaller satellites, research could be made easier and cheaper," says Wu. "The heat shield would also help save cost in recovery missions, as its high induced drag reduces the amount of fuel burned upon re-entry."