KerbalX

High Lift Duna Spaceplane

Tired of planes that require a quadzillion quickloads to successfully land on Duna? This SSTO spaceplane is designed to be reliably landable on Duna, even under Hard Career conditions and it has a long glide range. It also handles extremely well in Kerbin’s atmosphere.

It should be noted that this spaceplane is basically specialized for Kerbin to Duna operations. While you could adapt it for carrying payload into LKO it would be sub-optimal for such a task. OTOH it should be pretty suitable for visits to any low-gravity world like Ike or Dres and deals superbly with rugged terrain.

Features:

• Carriers 6 Kerbals: Plenty for tourism or a cough rescue mission
• High lift for low speed landings and a long glide range
• Aerodynamically stable, maneuverable, no unwelcome torque from engines
• Quad landing gear widely spaced for safe landings on bumpy Duna, plus extra landing gear for good luck
• Slight downward pitch when landed to glue the aircraft to the ground - no bouncing around on landing
• Integrated ISRU setup for refueling (5 to deploy, 6 to retract)
• Has a nose-mounted docking port so can be used as a push-tug
• Uses some mild offsetting abuse - the wings partially overlap and there are wings under the Mk1 Fuel Fuselages to protect them from heat - but they also add to lift, so it’s liftier than it looks

Ascent:

Since it is designed to glide well, this plane skimps on engines to keep it light - it pushes the engines to the very limit of what they can get into orbit. It requires an esoteric ascent trajectory:

• Fly off the end of the runway - due to ground-pinning it can’t actually lift off from a level surface
• Fly level across the ocean until going at roughly 250m/s (this raises the mach multiplier to a level allowing ascent at this speed)
• Pitch up to 20 degrees an ascend to above 5000m
• Level out and pitch down to about -2 degrees
• Activate the LV-N engines to push the plane from 350m/s to 400m/s: then disengage them (Action Group 2 toggles LV-N), the Mach Multiplier should now be high enough that the plane continues to accelerate
• (Alternatively instead of igniting the LV-N’s you can also follow prograde and gently swoop down to break the sound barrier, I’m not really sure which is more efficient as with the latter approach you lose several 1000m of altitude)
• Having broken the sound barrier, continue to fly level or slightly down until flying at 600m/s, then pitch up to 10 degrees
• Once above 10000m engage the LV-Ns again
• When the RAPIERs start to die off toggle them to rocket mode (Action Group 1) and pitch up to 25 degrees
• Complete the orbital insertion using LV-Ns

With some levelling out at 12000m you can get up to 1400m/s or so on air breathing RAPIERs. This is fancier than required as the RAPIERs in ClosedCycle mode give enough of a kick to get into orbit even from 1100m/s. It’s actually possible to get into orbit with liquid fuel alone but I believe it’s more efficient to bring and use oxidizer.

Deep Space Use:

You should be able to get to orbit with 1300-1500m/s of dV remaining. It should be enough to transfer to Duna or to transfer to Minmus to refuel there. You can also do in-orbit refueling using the shielded docking port if need be.

The total vacuum range is roughly 3500-3800m/s depending if you load Oxidizer or not (having Oxidizer is recommended, as 300m/s of high quality thrust is pretty handy).

Landing on Duna:

For descent set the control surfaces Authority Limiter to 150. You can flail the plane around to bleed of velocity, it is not prone to get into spins or tumbling.

Ideally you should land nearly empty at low altitudes (i.e. Duna’s Midland Sea). The thicker air makes the landing a lot easier.

It’s also possible to land when nearly full and/or at higher altitudes. This requires pitching up and using the LV-Ns to zero out the vertical velocity. This is handy if you can’t refuel where you need to land. Overall it’s a lot less safe than a near-empty landing though.

You may find landing to be more pleasant if you lower the friction control on the wheels.

Ascent from Duna:

Use the LV-Ns to build up as much speed as possible while still supported by the wheels. Ideally lift off using a hill as a ramp. Because the LV-N’s only provide a TWR of ~1.1 gravity drag is pretty severe during flight, it is advisable to ignite the RAPIERs in ClosedCycle mode at lift off (pitch up to 30-45 degrees). Between wheels and RAPIERs it should be possible to get halfway to orbit velocity making the low TWR of the LV-N’s not a serious problem.

Landing in a Vacuum:

Land tail first. When the engines touchdown, tip forward onto wheels (keep the thrust going).

If you’re feeling brave this plane is also highly capable of high speed horizontal landings on vacuum worlds.

Taking Off:

Because of ground pinning (the engine thrust tends to press the plane to the ground) you want to use a ramp to get off the ground. You can also toggle the RAPIERs on for a moment to kick the plane off the ground through thrust vectoring. Finally the plane has some extra wheels, you can retract the big rear landing gears and it will then have a slight positive pitch.

Built in the SPH in KSP version 1.3.1.