Parts: Struct

Decoupler

Drops a booster strapped to the flank. Put one between the rocket's side and each strap-on, and the strap-ons fall away when the stage fires.

It has two points, back to back on its flanks. The inner one bolts against the rocket's side; the outer one carries the booster. Only the inner one lets go, so the decoupler leaves with the booster.

Its part sheet offers Fire, greyed until the rocket has launched. It has no properties. Put it in a stage to fire it at the right moment instead of tapping it.

Pairs with a Solid Booster or a flank tank. Instead of the Separator, which cuts a stack in line rather than on the side.

Separator

Cuts a stack in two. Put it between a spent stage and the one above it, and one tap of STAGE leaves the old stage behind.

It sits in line, one stack point on top and one underneath, and both of them let go. Nothing is left holding it, so it blows itself clear in a small flash instead of tumbling along behind you.

Its part sheet offers Fire, greyed until the rocket has launched. It has no properties. In the staging list, put it in the same stage as the engine above it and the new stage lights as the old one falls.

Pairs with the engine of the stage above it. Instead of the Decoupler, which drops a booster off the flank.

Payload Bay

A hollow hull with clamshell doors. Mount instruments on the rails inside and they ride up out of the airflow, then open the doors in orbit to use them.

MASS, COST and CAVITY are quoted at the bay's shortest setting. Its properties sheet carries one slider, Length, from 48 px to 256 px, and all three grow with it. The slider is hangar-only.

It has a stack point at each end and three rails inside: the two inner walls and the floor. There are no rails on the outside, so a part dropped near the bay goes in it rather than on it.

Its part sheet offers Open doors and Close doors, worded by which way they are. Staging it swings them the other way, so one stage can open them and a later one shut them. The doors stay however you left them, so a satellite abandoned with its bay open is found open.

Pairs with a Thermometer, a Barometer or any instrument you want kept out of the airflow. Instead of a Payload Fairing, which is thrown away rather than closed again.

Docking Port

A latching ring. Bring it face to face with another one in orbit, slowly and squarely, and the two ships become one with their tanks plumbed together.

Its stack point sits underneath; the latching face is on top. That face takes nothing but another Docking Port, so it cannot be built over by accident. Two of them can be joined in the hangar, which is how you build a ship with a joint it can shed later.

The four DOCK rows are the latch's limits: how close the two faces must be, how slowly they may close, how far off square they may point, and how fast the two ships may turn against each other. Where the two ports differ, the tighter figure is the one that counts. Fuel and hypergolic propellant both cross the joint once it is made.

Its part sheet offers Undock, greyed while nothing is docked to it. Staging it cuts the joint the same way, and pushes the two halves gently apart.

Pairs with an RCS Thruster Block and a tank of hypergolic propellant, which is what the last few metres are flown on. Instead of the Separator, which cuts a joint and can never make one.

Payload Fairing

A shell over the nose of the rocket. What fits inside it rides up with no drag and no heating of its own, and the shell is split off and thrown away once the air is thin.

The shell is a stack of rings: a base the width of a tank, two rings you can widen or narrow, and a tip. Its properties sheet carries a Length slider from 64 px to 256 px and one slider per ring, Lower ring and Upper ring, from 16 px to 96 px each. The figures above are what the card reads at the settings a fresh one is placed with; MASS, COST, PAYLOAD and RINGS all follow the sliders. Mass and price go with the skin, so a taller or a fatter shell costs more of both. All the sliders are hangar-only.

It has two points, both on the base plate and both riding the Length slider: a stack point underneath, and a mounting point just inside it that the cargo sits on. Power and food reach the cargo through that point, so an instrument under the shell still runs off the ship.

Its part sheet offers Jettison, greyed until the rocket has launched. It splits into two halves, which are flown, not deleted, and they tumble down behind you. Whatever was on the mounting point stays behind on the part below.

Pairs with a satellite that will not survive the ascent bare. Instead of the Contoured Fairing, which has five rings for a payload this one cannot be drawn around.

Contoured Fairing

A taller shell with five rings instead of two: five places to bend the skin, so it goes round a payload the plain fairing will not.

Its properties sheet carries a Length slider from 96 px to 384 px and five ring sliders, Ring 1 at the base to Ring 5 at the nose, from 16 px to 96 px each. As on the Payload Fairing, the figures above are the settings a fresh one is placed with, and mass, price and the room inside all follow the sliders.

It attaches and it is thrown away exactly as the Payload Fairing is: a stack point and a mounting point on the base plate, Jettison on its sheet, and two halves left tumbling. The same warning applies, and so does the same hangar line when the payload stands through the skin.

Pairs with a wide or an awkwardly shaped payload on a tall rocket. Instead of the Payload Fairing, which weighs and costs less on anything it will actually go round.