Complex sentence: Some high temperature metal alloys can withstand reentry heat, they simply get hot and re-radiate the absorbed heat (an approach called "heat sink" thermal protection), a technique that was planned for the X- 20 Dyna-Soar winged space vehicle.
Split into simpler sentences: Some high temperature metal alloys can withstand reentry heat, and simply get hot and re-radiate the absorbed heat. This approach is called "heat sink" thermal protection, and was planned for the X- 20 Dyna-Soar winged space vehicle.