KerbalX

Details

• Type: SPH
• Class: spaceplane
• Part Count: 75
• Pure Stock
• KSP: 1.12.3

Sittang SSTO

A stock spaceplane built with 75 of the finest parts; its root part is mk3CargoBayM.

Built in the SPH in KSP version 1.12.3.

The big sister of the Skipjack SSTO, this is a medium-lift autonomous cargo spaceplane based on the Skylon design. Early versions of this design had a distressing tendency to explode on landing, but I’ve put in a lot of work to make it more robust and reliable and it can now be landed safely on the KSC runway even without parachutes. Most of the time.
Despite these challenges I use it extensively in my career mode playthrough for launches, orbital rescue, and parts recovery. The self-deploying arm is a big help and can be fitted with the Claw (as in the craft file) or with a decoupler for launches.

Manual

At launch, lock engine gimbals (0), throttle up to maximum and stage to ignite the engines. Pitch up hard from about 120m/s until you lift off, then free gimbals (0), retract landing gear, and aim for about 10° above the horizon. Once you reach 400m/s climb to 10-11km and pick up as much speed as you can, then gently pitch up again to 20°-25°. When the RAPIERs’ thrust starts to dip, switch to closed cycle mode (1) and pitch up to 30°-35°, burn until your apoapsis is clear of the atmosphere, then shut off engines, hold prograde, and coast to your circularisation burn.

Once in orbit deploy the solar panels and docking port shield (2). You should have 1600-1700m/s of ΔV from LKO.
To deploy the payload or claw, unlock the hinges (6) and play the KAL-1000 sequence (7). To retract, reverse the sequence (8), play (7), then lock (6) once the doors are closed. If you’re grabbing another craft or part I strongly recommend using ‘Control from’ the claw - and remember that your cargo space is limited to 4.5×2.5×2.5m. The smaller hinge and piston would give you more room, but in practice they’re too flimsy for safe re-entry.

Sittang behaves best with a very gentle re-entry, aiming for a little way short of the landing site. A burn of about 150m/s from LKO is enough. Once you’ve made your de-orbit burn, retract the solar panels and fins (2), then angle about 10°-15° above the horizon and use stability assist to hold that attitude. Deploy airbrakes (B) if you need to. Below about 25km you should have enough authority from the lifting surfaces to control your descent pretty well. Sometimes it suffers from pitch oscillation, which you can deal with by turning off pitch authority on the front canards (9).

Landing is the hardest part of practically any Sittang mission because the 70m/s impact tolerance of the landing gear is very close to the stall speed, and the RAPIERs’ mediocre subsonic thrust won’t help much. I recommend coming in at about a 15°-20° angle, keeping your speed steady at 150m/s or so, and deploying landing gear and airbrakes (B) at the last minute. If things look bad, stage to deploy the parachutes.

I hope you enjoy flying Sittang, whether for its practical uses as a launch and rescue craft or for the sheer adrenaline rush of trying to land the damned thing in one piece!