Stock Eve lander how to

[barsandcat]

 

Stock, no mods, version 1.2 pre release.

 

This post does not include Kerbin liftoff and Kerbin-Eve transfer!

Even more, basic task here is to get Mk1 pod to orbit of Eve! Rendezvous with rescue craft and trip back to Kerbin are not covered!

 

Mission overview

1. Deorbit

2. Inflate heat shield

3. After ship slows down to ~300m/s decouple rear stabilization heat shields

4. At ~4000m stage parachutes

5. At ~2000m when first set of parachutes opens, drop bottom heat shield, deploy landing gear

6. Land, deploy ladders, plant flags, do science, take data, get back in pod

7. Decouple landing gear, parachutes and start engines

8. When empty, drop radial attached stage, decrease thrust, to avoid burning in atmosphere

9. Drop core stage

10. Circularize orbit

 

Ascent dV and TWR calculations for curious: https://docs.google.com/spreadsheets/d/1PFvv3BKWl643dKuvvBaZ77RqYgSPDW2W9MFO_xK1qhg/edit?usp=sharing

This particular rocket has reached 93 km orbit from 300m altitude - imgur mission album: http://imgur.com/a/pq8dT

Craft file: https://kerbal.curseforge.com/projects/ksp-eve-lander

 

Design challenges

You have to drop 60t rocket and hit dense atmosphere at 3000m/s!

Solutions:

1. Use engines to kill velocity to ~1400. This has a downside - 1600 dv for 60t rocket is a lot! You’ll end up with a lot bigger ship, and still risky - some stuff may burn off.

2. Drop an empty rocket - use ISRU to mine fuel on planet - did not try it, but should work

3. Use heat shields - classical approach, but:

   1. Regular heat shields will run out of ablator, so only inflatable heat shield can be used

   2. Stability problem - heat shield adds a lot of drag, this make ship prone to tumble. And aerobrakes, wings e.t.c just can not survive contact with atmosphere at 3000m/s. Reaction wheels are too weak, and even best rcs engines can not hold your ship straight. So you got to use another heat shields to add drag to tail of lander!

4. Plane like design - try to keep your height above very dense atmosphere (~60km) until speed is down to acceptable levels. Should work, but I did not try it. May be very time consuming.

 

5pa pressure at sea level makes most engines useless

Most engines have 0 Isp at 3pa pressure. Only Vector (Twin roar and Mammoth), Dart and Mainsail are usable. Mainsail is big, but not as powerful, dart has no vectoring and weak, twin roar and mammoth have no bottom attachment node. Duh, Vector is best looking engine for the task.

Dense atmosphere causes a lot of drag

Basic rules of minimizing drag:

1. Drag occlusion works only for stacks: use same size and adapters. Yes, service bay does not occlude drag of its content.

2. Drag of radial attached part depends on their orientation, and not occluded. Even if you clip it inside of tank.

3. Bottom flat surfaces cause drag too: close bottom with cones

4. Physic-less parts add drag to parent: do not have to be mirrored

Separatrons do not work and decouplers can not push stages aside

High gravity and dense atmosphere literally tear away your radial stages when you activate decouplers. If they tumble wrong way - game over. And you really can not afford long rocket - without radial stage - it is a lot harder to land.

1. Spin before separation

2. Use TT-70 decouplers - they give more room

3. Design radial stage with some drag on outside - to ensure it tumbles away from core stage.

 

Kerbal has to climb quite complex rocket, but ladders are hard to place and add drag

To plant flag - you need to go down. And you have no choice but to put pod on top of the rocket. So you need ladders! But this is not as simple as it sounds: you can not put them on engine shroud, some engines a lot bigger than Telus-LV ladder, and all they add drag to your rocket. You can put another landing can at the bottom and use it to transfer kerbal to pod, and then leave it on planet. But you can not move data this way! Another way - build side ramp, but there is high risk that it will interfere with launch.

1. Use Pegasus I Mobility Enhancer - they add a lot less drag and can be spaced a lot

2. Put Telus-LV  on decouplers - to drop them before launch

3. Test your ladders - go all way down and back up on Kerbin

 

High forces tear your ship apart!

Aerobraking, parachute opening, landing, liftoff and decoupling of anything - all this actions on Eve put serious stress on your ship.

Only one solution - more struts!

In 1.2, with advanced tweaks on, you can use auto struts option on any part - use that, since this struts do not add drag!

Edited September 28, 2016 by barsandcat

[Vanamonde]

Looks like this was meant to be a challenge? And so, moved to Challenges. 

[Gaarst]

2 minutes ago, Vanamonde said:

Looks like this was meant to be a challenge? And so, moved to Challenges. 

More of a tutorial to me.

 

Seems basic but rather complete. Though some more details or explanations could be useful for a new player willing to get to Eve.