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ESN-104 LEOPARD

ESN-104 LEOPARD (European Spacecraft, Nuclear powered, model 104: Lunar Economy, Orbital Platform Access, Reusable Delivery vehicle) is a high performance, easy-to-fly, 5-seat SSTO spaceplane for missions to Kerbin, Mun or Minmus orbit, filling the gap between LKO/MKO shuttles and larger interplanetary vehicles. Its small cargo bay/service bay gives it additional versatility compared with pure passenger spaceplanes.

Pure stock, no mods, no DLCs. 92 parts, root part is the Mk1 inline cockpit.
v1.1 changelog: fixed obstructed Mk2 crew cabin hatch. Nosecone color updated for KSP 1.10.

- dV stats: 1800m/s @ 85x85km LKO, 500m/s @ 100x100km Munar orbit, 250m/s @ 40km PE Mun-Kerbin direct reentry orbit.
- Cargo bay/service bay for max. 2.25t mission payload, e.g. nano satellite, robotic device, surface science instruments, Mk1 crew cabin (dV loss <100m/s compared with empty bay) or Mk1 liquid fuel tank for additional fuel, in which case its dV @ 85x85km LKO increases to 2300m/s.
- Balanced and almost constant CoM regardless of fuel consumption, great maneuverability and stability during the entire mission. No need to transfer fuel.
- Atmosphere-skipping and decent gliding capability.

[1] = CR-7 mode switch
[2] = LV-N on/off
[3] = toggle bay door
[4] = toggle solar panels
[5]
[6]
[7]
[8]
[9]
[0] = all engines on/off
Brakes = brakes+airbrakes

- It can be seen as a smaller version of the ESN-106 ALLIGATOR II. And no, this craft is NOT another April joke. I build it mainly for the look, but it turns out to be surprisingly capable for its role.
- Although not designed for interplanetary missions, they are totally possible with proper orbital refueling service. Manually open aft Mk2 fuel bay to ease refueling.
- Mk2 parts have horribly low lift-to-drag ratio which I do not understand. I see it as a development oversight. On my previous Mk2 SSTOs, this effect is countered by extensive use of non-Mk2 parts, notably big-S wings. But on the LEOPARD prototype, Mk2 parts took up a fairly large portion, making the craft very draggy (mostly because of severe induced drag when AoA > 0), like flying with airbrakes always deployed. In order to fix the issue and give it IMO reasonable flight characteristics, I have no choice but to double its wing surfaces. To justify my part clipping, I imagine the craft having a blended wing body design with thick wings that hold more fuel and generate more lift, much like the big-S shuttle wings.

Ascent: 5-10 degrees to space!
- Engage SAS, launch, Vr=100m/s (beware of tailstrike), pull up to 5 degrees pitch angle.
- Keep 5 degrees pitch until reaching 5km, stay away from pitch control, let it pitch up to 10 degrees while accelerating, keep this pitch.
- When speed hardly increases (~1540m/s @ 22km), press [1] to switch RAPIERs mode and [2] to fire LV-N. Keep 10 degrees pitch.
- At LOX burnout, lock prograde and continue ascent with LV-N only.
- Push AP to desired value, shut down engines, coast till circularization. 85km AP should be 5-9min away from engine cutoff.
- Press [3] then [4] to deploy solar panels.

Descent
- Burn PE to 40km above landing zone.
- If returning from Mun/Minmus orbit, it's difficult to predict reentry area and it may require atmospheric flight to reach destination, but PE should also be 40km.
- Lock radial-out to aerobrake.
- When estimated impact point draws near landing site, reduce AoA to 0-20 degrees. Minor change of AoA makes significant difference on its glide path which makes it pretty fun to fly. 10 degrees is good for most situations.
- You can also use air-breathing RAPIERs to fly to destination.
- Use big-S turns and airbrakes to bleed off speed. Touch down at ~100m/s, keep a low vertical speed. Deploying drogue chutes is optional.

Wish you enjoy and happy landing!