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The history of Eve SSTOs and reusables


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Well, some kinks still need to be ironed out, but after several weeks I managed to put an Eve SSTO repeatedly to orbit. Will be put on KerbalX once polished and time permits. Hope you don't mind posting it prematurly.

XE-01 Apex Mk VI Eve SSTO

Our RnD-Team spent literally weeks in reverse-engineering crafts by realseek, Kergarin and Chargan to escape the hellish boundaries of Eve’s thick atmosphere and high gravity in an SSTO.
The Jool SSTA from Lt. Duckweed and Stratzeblitz also gave some input.


As drag is a major issue with getting up to Eve orbit, several measures have been taken to minimize drag:

  • overall craft is highly streamlined

  • many fuel tanks have been clipped inside a fairing. 1.875m form factor was chosen as a compromise between part count and drag.

  • propellers are inside 1.25m service bays. Once rocket motors are ignited, service bays are closed.

  • As weight for ISRU / Crew / landing gear is almost consistent, switching to the larger 4 vector / 3 Nerv approach compared to realseek's 3 vector / 2 Nerv version offered bigger margins in term of TWR and dV.


Crew and Control

MK1 Lander Can inside a fairing offers seating for a Pilot (or Engineer during mining). Two additional crew members can rest comfortably in the womb-like confinements of an inflatable airlock.

Access is provided by the trademark MMA “frontal airlock in a servicebay” technology

Remote Control capability is provided by a RC-001S Remote Guidance Unit and a single RA2- Relay Antenna.


Propeller flight

Six service bays host a total of 12 medium sized motors with 5 R25 propeller blades each. The 1.25m service bay is sufficient to shield the propellers from drag when closed.

The propellers are powered by a total of four fuel cell arrays near the front. 

The fuel cells toggle with the same key as the motor power (action group 1).

Motor lock and propeller deploy status is bound to action group 2.

When deployed, propeller deploy angle can be modified with the main throttle.

For takeoff, do the following:

  • Toggle deploy state and motor lock (AG2)

  • Activate motor power and fuel cells (AG1)

  • disengage brakes

  • use main throttle to adjust prop angle for maximum propeller efficiency.

  • take off 

For transitioning to rocket flight, do the following:

  • disengage rotor power (AG1)

  • Activate brakes

  • Toggle deploy state and motor lock (AG2)

  • Close service bays (AG10)

Rocket flight

Propellers will bring you to about 15 km above sea level on Eve.

Try to gain as much velocity as possible with rotors. Engage Vectors and stow away the propellers.

Ascent can be divided into several phases:

  • 15.5 km ASL: use vectors together with a very small climb (about 5°) to gain enough speed and to break the sound barrier. At around 500 m/s, engage Nervs as well.

  • Pitch up: pitch up very gently to about 25°. Try to minimize drag by flying mostly in prograde direction

  • Max Q: at around 39 km above sea level, velocity and air pressure put the highest amount of stress on the craft. Use the indicator for overheating on the frontal fairing to reduce thrust if overheating is reaching critical levels. When overheating gets down, throttle up again to maximum thrust. Turns out, that throtteling down near max Q resulted in a higher velocity when oxidiser ran out.

  • Fly prograde and getting suborbital: after passing max Q and being back on max throttle, fly prograde for the rest. You should reach almost 2.800 m/s when oxidiser runs out and an Apoapsis of 110-120 km. Anything lower than 2.700 m/s is really hard for the circularization.

  • Circularize: continue flying with Nervs and try to complete your circularization burn.


Known bugs

When using Hyper Edit to teleport craft onto the surface of Eve, the impact from landing gear combined with the huge amount of clipping can get you explody results. For this, I used the cheat menu to increase joint strength and prohibit damage.
Remember to uncheck them again for take-off. The craft flies nicely without them.

Reaching almost max flight level before rocket ignition.


Out of oxidiser with 2.800+ m/s. The Nervs will do the rest of the circularization. The higher TWR of this layout compared with a 3 Vector / 2 Nerv appraoch made circularization easier.


Circularization achieved.

Test of ISRU complement on the runway. Craft was launched empty and refueled with a small converter and a large mining drill powered by fuel cell arrays. Level 5 Engineer onboard.

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  • 2 months later...

Well, I guess my design may fit this thread.

I guess the innovation here is that I've got a RoRo payload bay.

I've already tested a mining rover that can roll on and off, so with that module, the entire thing becomes self sufficient.

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@Mephisto81 thanks for your post. And sorry for my late reply. 

That SSTO looks really cool and is quite an achievement!

But in my opinion the amount of clipping on this craft is a little to high to be considered legit. Especially fuel tank and engine clipping brings a lot advantage. I'm very sorry, but I hope you don't mind that decision?

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  • 10 months later...

I hope this isn't too much of a Necropost, but I just released my video of a single stage to Eve sea level (under 150m) and back to Kerbin: 

This is 1.11.2, Stock + Breaking ground.

I have had the design mostly fleshed out for several months, but a couple weeks ago I finally just sat down and banged it out.

It carries a full suite of science experiments (save for the science Jr.), a full suite of scanning equipment and solar powered isru, and a small selection of breaking ground deployable science experiments, along with a somewhat cramped (but much better than it could be) living space for its crew of 3.

It uses a combination of vectors and nervs to ascent back to orbit, then uses ion engines to perform a series of pe kicks, combined with a small reserve of liquid fuel used to assist on the final ejection kick.


Some technical details on the craft:

3050 m/s Vector vac dv

1650m/s Nerv vac dv if used after vectors (they actually burn them together, igniting at the same time, so realistically its a couple hundred meters a second less than this)

Total ascent dv of about 4500 when used in a single stage, a very small amount of which is reserved to assist with the final ejection back home.

Approximately 1800 m/s dv on Ion engines (a tad less but don't feel like looking up the exact number atm)

88.75 tons per Vector.  44.375 tons per Nerv

Wing loading of 4.4 tons per wing area with 3 degrees incidence.

Ignition is at 16.5km at electricity exhaustion, vector burnout is at about 2450m/s orbital speed with an angle between 15 and 20 degrees over the horizon ( I follow pure prograde until reaching the high atmo, once prograde drops to 15 degrees, I swap to SAS hold).

5.5 tons per large ducted fan blade, 1.26 tons per kNm of rotor torque.

Edited by Lt_Duckweed
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