Why does space hardware come apart during reentry?

Objects reentering the atmosphere often break up in stages.

Objects reentering the atmosphere often break up in stages.

On reentering the atmosphere, a large debris object will be subjected to extreme heating and loads caused by the interaction of the fast-moving object with the atmosphere (at the reentry point, the object is travelling more than 20 times faster than a bullet). At some point, the temperature of the object reaches a critical point, aerodynamic loads increase,¬†and the object will break up. Breakup could be caused by the failure of critical structural components as their temperatures exceed their melting points or, in a more extreme case, by an explosion of fuel or pressurized gas remaining in the object’s tanks.

Whatever the cause, the first major breakup event generally occurs at an altitude between 74 and 83 km. At this point, the object breaks into several smaller objects, and each continues to fragment or melt as long as sufficient heating and loads exist. When surviving objects have slowed sufficiently, the heat rate drops and a cloud of debris remains to fall and impact the ground.

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