Build a jet

Put a jet together from the Planes tab, an intake at the nose and a jet at the tail, and take it off the runway.

A jet is an aeroplane whose engine breathes through an intake. It is built and flown like the propeller aeroplane in Flying an aeroplane, with four parts swapped in. Why each part behaves as it does is on Aeroplanes.

• You own the Aviation and Jet Flight tech nodes (Buy a tech node).
• Your Launch Pad is at level 2 or higher. A jet with a fuselage long enough to carry its fuel is longer than the level-1 runway's 20 m, and the hangar says so under the ship's mass (Upgrade a building).
• An astronaut is free to sit in the cockpit.

Steps

1. Open the Planes tab and build the stack from the nose down. An AI-1 Air Intake at the top, a CK-1 Cockpit under it, an FS-1 Fuselage under that, and a JT-1 Jet Tail closing the end. Stretch the fuselage to about 16 m: a jet is thirsty, and the fuselage is its only tank.
2. Lay an SW-1 Supersonic Wing on the fuselage's face at the centre of mass. Drop it where the ship balances; the root joins wherever you let go.
3. Hang two LG-1 Landing Gear on the flank opposite the canopy: a main wheel just behind the centre of mass, a smaller one under the cockpit.
4. Seat an astronaut in the cockpit on its sheet, then tap Fly. The readout under the ship's mass says it takes off from the runway.
5. Open the throttle all the way. The jet winds up over about five seconds, so the roll starts slowly and then pulls hard.
6. Hold the nose-up pitch button as the speed passes about 55 m/s, until the nose is about 9° up, then fly the climb. The jet leaves the ground at about 80 m/s, so do not wait: the tyres burst past 85 m/s.
7. Raise the gear once you are climbing (Raise and lower the landing gear).

Breaking the sound barrier

Climb to about 12 km, level off with the nose only a degree or two up, and leave the throttle open. Low down the air is too thick: the jet built above stops just short of Mach 1 near the ground. High up it goes on through it, past Mach 1.6. Too high and the engine runs short of air: above about 14 km it cannot push the jet through. Mach 2 needs more: the jet tail's Thrust slider turned well up and a bigger intake to feed it, and even then it is a dash, because a long fuselage flown that fast heats up (Aeroplanes).

What you should see

An orange flame behind the nozzle while the jet runs, and the speed climbing past the speed of sound high up. If the throttle is open and the jet stays dark and pushes nothing, the ship has no air intake: My jet's engine runs but it will not move.