Eve and back with Ferram Aerospace mod., KSP v1.1.3

Starlionblue · September 11, 2016

After incautiously checking out some KSP news and feeling inspired, it was back in the deep end. I challenged myself to an Eve mission with Ferram Aerospace mod. My constraints

Single launch to Eve surface and back to Kerbin orbit.
Jeb must plant a flag on the surface.
Ferram Aerospace installed, i.e. "realistic" aerodynamic effects in Kerbin and Eve atmospheres.

Ferram made things both easier and harder. On the one hand aerodynamic effects are much less forgiving. On the other hand aerodynamic shapes behave as expected. This allowed me to design a vehicle that could enter Eve's atmosphere without any steering inputs, simply relying on natural stability to keep the heatshield in the direction of travel.

I designed and tested the whole thing "backwards". First the Eve ascent vehicle. Once that was done I figured out how to get it from Low Eve Orbit to a soft landing at Eve sea level. Finally the easiest part, which was getting everything from the Kerbal Space Center to Low Eve Orbit.

The ascent vehicle weighs in at 187 tons and consists of three basic stages, with the lower stage having external boosters with asparagus staging.

Lower stage. One Spike and two Vector engines. Three asparagus boosters with one Vector each.
Mid stage. Three Spike engines. Three fins placed on i-beams far aft of the engines for aerodynamic stability.
Upper stage. One Terrier engine.

For Eve descent, the goal was to make the vehicle aerodynamically stable. I first experimented with active fins and RCS at the top of the stack. This worked in the upper atmosphere but below about 40000 meters the vehicle started wobbling and spinning uncontrollably, eventually leading to either heat-induced or aerodynamic breakup. On a hunch I tried re-entry with no steering and it worked. Most of the weight is at the bottom and the aeroshell can withstand some heating on the side as the vehicle returns to center. The three main features of the descent enclosure are:

Parachutes on struts which are jettisoned after landing.
Inflatable heatshield.
A massive aeroshell encasing most of the ascent stage.

Kerbin booster and Eve transfer. Brute force approach with nothing very complex. 13 asparagus stacks with Mammoth engine to start and Rhino engines on the last ones. I relied purely on engine power to enter Eve orbit, since aerobraking directly from interplanetary speeds inevitably led to burnup. Even starting from an atmosphere skimming orbit with apoapsis of 91km and a periapsis of 80km, the heat shield went up to 90% of maximum temperature.

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