Eve landing and return in 1.2.1 (stock parts)

[Plummet]

Hi all

This was a huge challenge for me so I thought I'd write it up for posterity.

I used:

- 1.2.1 with stock parts - apart from MechJeb for dv calculations and landing predictions (no autopilot)

- Hyperedit - just during development/test, not for the full-up mission

- Kerbal Alarm Clock

- Precise Node

As many have noted the two big challenges are:

1. Getting enough dv (and TWR) to get back in to orbit

2. Getting the whole thing down on the ground safely through the intense heating effects

The ship

From reading other posts I found that at least 7500 dv is needed to launch from the highest Eve elevations, and far more than that is needed for a sea-level launch. 1000m difference in elevation equates to a huge difference in the required dv.

I eventually built a ship with an impressive sounding 10,000 dv - but on testing found it wouldn't even leave the ground! You have to get sufficient TWR at each stage of the launch/ascent too.

Experimenting with various engines showed that the Aerospike works well in the Eve atmosphere. But, my attempts with Aerospike-only builds weren't successful - partly due to low launch thrust and partly as I couldn't get enough steering control.

So, a central Vector surrounded by Aerospikes was my eventual solution. The Vector has excellent gimbal control plus plenty of thrust - I use it a lot.

There are 6 Aerospikes on an outer ring, feeding fuel in to another 6 Aerospikes on an inner ring. The outer ring is the first stage to drop, taking the landing legs with it.

The remaining lower stage of 7 engines then drops off, leaving a higher ring of 6 Aerospikes surrounding a final central Aerospike. So, that's 18 Aerospikes and one Vector (plus some RCS thrusters)

Eventually all that is left is the central Aerospike on top of FLT-800/400 tanks.. it flies straight and true like a Minuteman missile!

I tested the Eve ascent using Hyperedit. I've landed on and returned from every other body in the system without using Hyperedit for testing, but I honestly think I would never have managed this challenge without being able to test the ascent (and the thermal entry) before the full-up mission.

The final ship had 8500 dv - and I found that's enough to get in to Eve orbit from an elevation of 5000m+. From sea-level it can barely take-off.

5000m does limit the landing sites significantly, but I found (from another post by Brotoro) this site at 6500:

2 49 57 S
171 24 03 W

I missed it..but still ended up at over 5000m so was able to get back.

Landing entry

I used Mechjeb landing guidance but found it fairly inaccurate with my craft. So, it became a game of trial and error - I saved my de-orbit manouver details and then tweaked by a few m/s until the landing was close enough to my target.

Thermal protection - 'The Flower'

This was really tricky! Coming in to Eve is like hitting a brick wall, especially around 46000m. Others had success with airbrakes, but in the end I went with a ring of 6 inflatable heatshields I call 'The Flower' to act as a an airbrake and to keep the ship retrograde-oriented. They are held back from the ship (to keep the centre of drag behind the centre of mass) using a system of girders.

I then had another pair of inflatable heatshields at the bottom to actually provide the thermal protection.

It works pretty well - as long as you come in shallow from a low orbit. No SAS/RCS needed to keep the ship oriented. Sometimes at 46000m things get a little wobbly, but it soon settles down and after that point (once speed drops below 1800m/s) the heat quickly dies off too.

The harder part is getting rid of the damn shields. If they touch anything they produce a huge explosion, destroying your craft. Getting rid of 'The Flower' wasn't too bad - just decouple it from the base of the girders once you're through the heat and generally the whole thing just disappears.

Getting rid of the lower two is harder, I think because they tend to bump in to each other (they overlap). I found the best results came from jettisoning 'The Flower' and then letting the drag from the two heatshields flip the whole vessel nose-down. Wait until a fairly low level (e.g. 10000) where the speed has dropped off significantly and then jettison them one at a time.

After that - pop the 6 drogues and the 6 radial chutes. They lower the speed nearly enough for landing - but a last second burst from the Vector allows a landing with almost full fuel tanks and with all the legs intact.

EVA

No major dramas, although it took a while to arrange all the ladders and I didn't do a great job of it so getting back up was fiddly. Others had used a MK1 pod at the base to avoid this issue.

Ascent

This took a few attempts. I found that going max thrust and not worrying about heating/aero affects had the best results. A careful gravity turn has to be flown to achieve orbit, but not too steep as you want to get out of that thick, soupy air quickly.

Rescue

Finally, I sent a simple pod to bring Jeb home. He stopped off at Gilly on the way...I really like Gilly, getting in to orbit and rendezvous with your ship using jet pack alone is fun!

If I went back..

I'm not sure I will as it was really hard... but if I did I think I'd spend even more time in the VAB trying to squeeze out more dv so I could return from lower levels. I'd also experiment more with Airbrakes and with some other solution for the lower heatshields.

 

I hope this is of use to some of you - good luck with your mission to Eve!.

[Geschosskopf]

Nice job!  Eve is a she-dog no doubt, no matter how you do it.  Congrats on the successful mission.

[Cydonian Monk]

Very nice. I like the heatshield "flower".

I need to revisit Eve sometime. Haven't landed there since 0.90. 

[MaxL_1023]

If you can manage Eve, try Tellumo in Galileo's planet pack. It has roughly the same gravity (1.9 G) but with 10 atmospheres on the surface. It also has a very annoying moon which rotates faster than its orbital velocity, meaning your ship will literally be thrown off. 

[Plummet]

Thanks for the tip MaxL_1023 - I'm using GPP now and just managed to complete a landing and return from Tellumo. It is similarly challenging to Eve, although the ability to use air-breathing engines changes it a bit. I used a smaller lander than my Eve lander - 2 stages with 2 Vectors and 6 Rapiers in the first stage, then 5 Aerospikes in the 2nd stage. Quite a tricky launch - took a lot of experimentation to find the right time to switch to air-breathing mode, and what ascent profile to fly.

GPP is a really great pack, I'm enjoying it.

[obney kerman]

So for eve ascent all you need to do is add more boosters? OK.