Pick a rocket or satellite, snap the real parts together on the launch pad, then launch or deploy. Every part card is factual engineering.
First orbital-class booster to land and re-fly. 9× Merlin, RP-1/LOX.
Methane burns cleanly (no soot inside the engine), can be produced on Mars via Sabatier, and gives a good balance of specific impulse and density. That's why Raptor, BE-4 and Zhuque all chose it.
Starship uses 301 stainless — cheap, weldable, and stronger at cryo temperatures. Rocket Lab's Neutron uses carbon composite for weight. Both are correct answers to different problems.
Flight computers run in triple modular redundancy. Each solves the same GNC problem; a voting circuit picks the majority. If one lies, it's outvoted and quietly ignored.
A rocket without steering is a very expensive missile that falls over. Gimballing the engine ±5–10° gives control authority to fight wind shear and the gravity turn.
Δv = Isp · g₀ · ln(m₀/mf). To reach LEO you need ~9.4 km/s of Δv, so you throw away empty tanks — or you land them and reuse them.
Re-entry heat comes from compressing air in front of the vehicle, not friction. Heat shields either ablate (Dragon) or radiate the heat away (Shuttle, Starship).
In vacuum you can't push against anything. Reaction wheels store momentum; when they saturate, thrusters or magnetic torquers desaturate them.
Modern GaAs multi-junction cells hit ~30% efficiency — nearly double silicon. Deployable arrays produce kW; ISS produces ~120 kW at end-of-life.
Voyager talks to Earth at 22.5 W across 24 billion km. It works because DSN's 70 m dishes have gain of ~74 dBi and the noise floor is near 3 K.
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