Rockets on a spaceship don't actually melt metal. While they generate immense heat, this heat is primarily focused on the combustion chamber and nozzle of the rocket engine, where the fuel burns.

Here's why:

* Heat Source: The heat comes from the burning of rocket fuel, usually a combination of liquid hydrogen and oxygen, or solid propellants.

* Engine Design: Rocket engines are designed to withstand extreme temperatures. The combustion chamber and nozzle are made of materials like nickel-based alloys or refractory metals which can withstand thousands of degrees Celsius.

* Cooling Systems: Many rocket engines have elaborate cooling systems to manage the intense heat. This can include regenerative cooling, where fuel or oxidizer is circulated through the engine's walls to absorb heat before entering the combustion chamber.

However, there are some exceptions:

* Heat Shield: The heat shield on a spaceship, which protects it during re-entry into the atmosphere, does experience extreme temperatures and can melt. But this is a different part of the spacecraft and not the rocket engine itself.

* Thermal Damage: In some cases, extreme heat from the rocket engine can cause thermal damage to other parts of the spacecraft, especially if the engines are not properly shielded.

In short, rockets on a spaceship are designed to manage heat effectively and don't melt metal in the same way that you might see in a science fiction movie.