KerbalX

Description

A stock rocket called Cassiel. Built with 134 of the finest parts, its root part is probeStackSmall.

Built in the VAB in KSP version 1.10.1.

Details

• Type: VAB
• Class: lifter
• Part Count: 134
• Pure Stock
• KSP: 1.10.1

The Cassiel* is my KSP recreation of the real-life Kistler K-1 fully-reusable launch vehicle, which was developed in the mid-to-late-1990s and early-to-mid-2000s, but was cancelled in October 2007 (at which point the prototype vehicle was approximately three-quarters complete) due to Rocketplane Kistler’s failure to attract sufficient private funding. It was to have been a two-stage design, with the first stage being dropped before reaching orbit and landing under parachutes, while the second stage, carrying its payload inside a can making up the forward section of the stage, would go into orbit, deploy the payload (letting it out of the payload can by swinging open a lid covering the top end of the can), and then deorbit itself (being protected from the heat of reentry by a heatshield on the forward surface of the payload-can lid) and soft-land.

True to the K-1 design, the Cassiel has three engines in a row side-by-side on the bottom of the first stage (Rockomax RE-I5 Skippers on the Cassiel, Kuznetsov NK-33s on the K-1), and one engine of the same type mounted on the flared lower end of the second stage. The first stage shuts down and separates partway through ascent; while the second stage ignites to push the vehicle onto a suborbital trajectory, the detached first stage turns around and performs a retrofire burn using its center engine and a small reserve supply of fuel and oxidiser. (This reserve propellant is locked out during the first stage’s ascent burn; following staging, immediately switch to the first stage, set SAS to retrograde-hold mode, press 2 to shut down the side engines and unlock the reserve propellant, and fire up the engine. By the time the first stage runs dry again, the Cassiel’s second stage should have its apoapsis up to 90-100 km, which just so happens to be a good cutoff point; switch back to the second stage and zero the throttle for the coast up to space.**)

Once the Cassiel is in space and nearing apoapsis, the second stage’s main engine comes back to life, and another pull of the staging lever activates the four Cub vernier engines making up the second stage’s orbital manoeuvring system (OMS); once the circularisation burn is complete, the stage’s main engine shuts down (press 3 to do this), with all subsequent thrusting being performed using the OMS and\or the vehicle’s RCS thrusters. After reaching the desired orbit for payload deployment, the payload-can lid’s mounting hinge unlocks, and the lid swings open (press 6 to unlock the hinge, and 7 to open the lid), allowing payload deployment; when the payload is well clear, 8 swings the lid shut again and 5 locks it back in place. The Cassiel’s remaining fuel, oxidiser, and monopropellant can then be used to deorbit the stage (if the deployment orbit is fairly high, it will usually be necessary to make one or more aerobraking passes through the upper atmosphere to bleed its speed down to a safe value for reentry). Remember that the heatshield is on the nose of the vehicle, so it reenters facing prograde, in contrast to the vast majority of spacecraft intended to survive reentry (which reenter facing retrograde).

Finally, once the second stage has slowed to a sufficiently-low speed, its parachutes open and bring it down to a gentle landing.

*: Named after one of the angel characters in the webcomic Misfile.

**: This works best if, like me, you edit your physics.cfg file to increase the unload and pack distances for atmospheric and suborbital flight to something much larger than their default values (for atmospheric flight, the default unload and pack distances are 22.5 kilometers and 25 km, respectively, and the unload and pack distances default to 15 and 10 km, respectively, for suborbital flight, while I generally play KSP with the unload and pack distances for these two flight regimes set to 750-1000 kilometers), so that detached stages and whatnot remain subject to physics (and quick-switch-to\from-using-bracket-or-Alt-bracket-able) long enough for them to land (rather than going on rails and being automatically destroyed when they fall too low in the atmosphere).