KerbalX

Description

A prototype air launched rocket capable of putting a small payload into orbit. It forms the orbital-rocket portion of the Hastur-1 and Hastur-2 vehicles, and can be attached via any standard hardpoint or radial decoupler.

A stock subassembly called Yellow King. Built with 55 of the finest parts, its root part is fuelTank.long.

Built in KSP version 1.11.1.

Details

• Type: Subassembly
• Class: lifter
• Part Count: 55
• Pure Stock
• KSP: 1.11.1

The Yellow King is composed of three main parts, plus the payload (here a Small Secondary Satellite).

The aft skirt, a hollow tubular structure (to accommodate the main engine’s exhaust), serves as the mounting point for the four solid-fuelled launch motors and the aft control fins (the latter are mounted in a box-fin configuration, which is more compact than the typical radial arrangement). The launch motors fire as soon as the Yellow King is dropped from the launch aircraft, propelling it forwards and away from the aircraft, while the fins help maintain the high pitch attitude necessary to keep the rocket’s trajectory from drooping too low early in first-stage flight. Once the rocket’s flightpath is such that the aft fins are no longer needed, the skirt is decoupled.

The aft end of the first stage has a single Dart aerospike rocket motor that provides most of the stage’s thrust, as well as a pair of Cub vernier motors for pitch and roll control and a sextet of bipropellant RCS thrusters for pitch and yaw control. The forward portion of the stage holds the Yellow King’s midbody control fins, which provide additional roll control throughout first-stage flight. Additionally, the first stage holds most of the struts that help secure the rocket to the aircraft prior to release.

RCS should be turned on just prior to release from the launch aircraft. At release, the verniers light immediately, with main-engine ignition delayed until clear of the launch aircraft. When carrying a payload similar in mass to the provided sample, if flown well, the first stage should push the craft’s apoapsis almost all the way up to 75-80 km by the time its fuel runs out.

The Yellow King’s second stage is much simpler than the first, comprising solely a fuel tank, a single Terrier engine, a protective aerodynamic fairing for the payload, and a decoupler to separate the stage from the payload when the time arises.

During a nominal launch with a payload similar in mass to the example provided, the second stage should initially be fired very briefly (for no more than about a second or two) upon first-stage separation, so as to push the rocket’s apoapsis up to 80 km or just above; there then follows a prolonged period of coasting until out of the atmosphere and up around at least 76-78 km altitude, when the payload fairing can be blown off and the Terrier reignited for the circularisation burn. A considerable quantity of propellants (and Δv) should remain after circularising in orbit, unless flying with a payload considerably heavier than the example Small Secondary Satellite.