What materials are commonly used to build the outer shell of a spaceship?

Spaceships are built from lightweight yet strong materials that can withstand high pressure, temperature extremes, and radiation. Common materials include aluminum alloys for structural strength, titanium for its resistance to heat and corrosion, and carbon fiber composites for lightweight durability. The outer surface often features heat-resistant tiles or ablative materials to protect against intense heat during re-entry. In some areas, multi-layer insulation (MLI) is used to prevent thermal loss and protect from micrometeoroid impacts. The design balances strength and weight because every extra kilogram increases fuel costs. These materials are extensively tested for performance under vacuum, radiation, and mechanical stress.