This video shows vessel which doesn't have engines behind heatshields:
Chech what happens for same vesel with heatshield covered engines:
Play both videos same time, check altitude and match videos so you can see results at same height.
What you see is Thermal protected vessel explodes faster, first its Mainsail II engine is destroyed, tank behind it is destroyed. Unprotected vessel that middle tank is saved from heat.
Next protected vector engines explode