KerbalX

Description

The Hibaru SSTO is a 100-ton class tandem-wing design spaceplane, capable of carrying 6 kerbals and 3.5-tons payload to a 75km orbit with 3900m/s dV remaining, and 4350m/s with no payload. This craft is well suited for small probe/satellite launches, space-station crew transfers, and small capacity missions to nearby bodies. You could flip the cargo bay and carry a small ISRU + drill for extended range.

The Hibaru prototype was designed much earlier than the more refined and expanded Niyaama series. However, thanks to the designer’s aesthetically-motivated decision to keep the craft’s profile as low as possible, it was found to have teething stability issues (fixed now!) during re-entry. This was considered unacceptable for downloaded production, though these problems were (mostly) ironed out with MOAR FINS and shifting the wings up and down, along with changing the anhedral + angle of incidence. Now the craft is considered very easy to fly by it’s pilots. Included are two aerospikes to help with vertical takeoffs/landings on the Mun and Minmus (and potentially Duna).

Built in the SPH in KSP version 1.4.3.

Launch Profile

The profiles are almost exactly the same with or without payload in the cargo bay. The main differences are climbing after lifting off the runway, and getting past 400m/s during the early stages (very important).

Hit space to activate the Rapiers. Rudder inputs will be required to keep the craft centered, hold the elevator full up to make this easier. The craft will lift off just under 100m/s near the end of the runway, do mind the tail on rotation! Afterwards, maintain a low altitude below 200m and start accelerating, tap F to keep your vertical speed as close to zero as you can. The craft will seem to struggle until 400m/s, past this point the Rapiers kick in and you get some good acceleration. Above 450m/s, start bringing the nose slowly up, targeting 10 degrees by 500m/s. You will get a rather rapid climb from here on. Maintain 10 degrees pitch until 7km, then tap F to lower it to 7 degrees-ish. Try to hit 1450m/s before 20km, at 10 degrees nose up.

At 20km, press 3 to activate NERV’s, and wait until the speed stops increasing (usually around 22.2km) then press 1 & 2 to engage ClosedCycle mode and close the intakes. Pitch up to 20 degrees and hold it until the apoapsis reaches 60km; at this point press 4 to shut off the Rapiers and pitch to 15 degrees. Hold until you reach 75km Ap, then pitch down as required to maintain 75km Ap while still burning. Once the Periapsis reaches around 70km, you can safely circularize as required.

If all’s done well, you should have around 3900m/s +dV remaining. As always, highest speed on the rapiers is key, as well as minimizing ClosedCycle burn time.

Experiment with different launch profiles and you may be able to squeeze some more dV from the craft.

Re-entry from LKO (for 72 tons mass)

A good point to aim for on re-entry is the old airfield, with a shallow path. Pitch attitudes of around 5-15 degrees will increase your range, while 20-30 will decrease it. Adjust your profile as required to reach the KSC runway. If required, hit 7 to deploy the rudder-airbrakes.

While most of the Hibaru’s instabilities have been ironed out, it still has a tendency to uncontrollably pitch over if you raise the nose too high above prograde. It’s highly recommended to not go beyond 30 degrees nose-up. If you do end up pitching over, quickly hit prograde on the SAS and engage RCS. The craft should stabilize again quickly (easier at higher altitudes). Below 20km and 1300m/s, you can pitch DOWN quite a bit if you want to reach the runway quicker (do this with care though).

Set the brakes on before landing; target touchdown speed is 70-90m/s. Deploy the rudder-airbrakes and try to keep the nose up for as long as possible (without lifting off again) to slow down quicker.

At lower weights, you can follow steeper trajectories (mostly subject to trial-and-error). The CoM does move aft as you drain the fuel, but will always remain in front of the CoL. If you do find the craft pitching over violently, try transferring the remaining fuel to the forward-tanks!

Known bug

Due to the way the landing gear is mounted, exiting timewarp with the craft stationary on the ground will cause the gear to tilt 45-degrees sideways. Quicksaving and quickloading will fix this