KSP: Tubby X Cargo Spaceplane

Another crosspost. Always wanted to make a spaceplane with a central cargo bay, finally succeeded after discovering a few extra laws of physics. Presenting the Tubby medium-duty cargo spaceplane:

(Freshly deployed station core.)

More info, pictures, and craft files after the break.

More pictures: http://imgur.com/a/cVKUh
Pictures are of an earlier revision, but aside from gear location and fitiment they’re basically the same.

Craft files (4): http://ridetheclown.com/downloads/TubbyX.zip

86 parts – STOCK

Fueled weight: 27.8 tons
Payload capacity: 9 tons
Payload dimensions: Roughly orange fuel tank + a bit left and right
Propulsion: 4x Turbo-jet (10 intakes), 2x Atomic, 6x Sm. Radial

200 monoprop
450 LF (jet fuel)
720 LF / 880 OX

Center of mass should be around the end of the rocket fuel tanks.

Flight profile:

– Rapid climb to 22km on 90 degree heading, 60 degree inclination.
– Slow climb to 24.5km

@ 1525m/s airspeed: engage main engines (2) and boosters (3); Zoom-climb at 55 degrees

– Jet engine shutoff at 29km (1)
– Booster shutoff (3) when Apogee >= 34km. May be reduced in duration or skipped entirely if payload is light.

@ 50km: burn at 15 degree angle until Apogee is > 80km
@ Apogee: burn at 0 degree inclination towards 90 degree heading until orbit circularized

Climb angle may need to be increased if near max of payload capacity.


In orbit, should have 33% of jet fuel (150/450) and 15-70% of rocket fuel (dependent on load) remaining.

Slightly wiggly with no payload and full fuel load. Returns to kerbin with no issues after payload delivered. Tendency to nose down below 1km at full load, but is fine afterwards.

Make sure to watch air intake and reduce throttle accordingly when executing zoom climb maneuver. This is the most crucial part of the whole exercise – if you flame out and start spinning, you will likely lose too much time if lifting a heavy payload.

Watch that you don’t clobber the engines/payload on take off.

9 tons is the max limit for having any sort of orbital maneuvering ability, such as docking with a station at 100km. You might be able to sneak 10 tons into a 70km orbit, but no fuel for any orbital stuff would be left.

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