totm nov 2021 Eve Landing and Return in Caveman Style

[king of nowhere]

10 minutes ago, EveMaster said:

Do you have any more info about this problem, when it happens and how to avoid it or perhaps links to discussions about it?

No idea. With my penchant for huge, complex motherships and multi-decade missions, I faced this problem a lot, and i talked about it many times in my mission reports. But it's not a specific discussion, just a few bits here and there in the middle of everything else. "and here i almost failed to get the astronaut back on the rocket because the ladder got misaligned", "and here the ascent suffered much greater drag because parts got misaligned", "and here the rockets got pointed sideways and I had to use alt-f12 to get a new rocket", "and when i reloaded the game, the parts were perfectly aligned again, miracle!".

But tring to condense my experience with it:

- the more parts you have in a linear arrangement, the more likely you are to face this bug. My previous mothership was a very long cylinder, and at times it became more similar to a banana. My current mothership is a large circle of fuel tanks, and the bug never manifested

- it is more likely to strike when your ship faces heavy forces. flying in atmosphere is most likely, I've never managed an eve reentry without skewing my propellers, but a hard docking also could do the trick.

- even if you do nothing wrong, it can still strike at random

- sometimes, it spontaneously reverts upon reloading the game. I wish I knew how to replicate that feat,  but no idea. I just know that every once in a while my banana-shaped mothership would become a cylinder again.

[EveMaster]

I found a solution to my ladder problem! 

11.1 introduced the feature that Kerbals stop at the end of a ladder. This feature has a bug that you cannot get from one ladder to the next after reloading. Thankfully there is an option to disable this in the general KSP settings. I can now continue with the mission in low Eve orbit without having to redesign the craft. However, I cannot continue with the current save on the surface of Eve because the elevation of the landing location is to low to get back to orbit.

[EveMaster]

Part 15: Transfer to Low Eve Orbit

Now that the problem with the ladder is sorted out, here is the mission report about getting from low Kerbin to low Eve orbit.

I used alexmoon KSP Launch Window Planner to calculate the burn needed for the transfer to Eve. Without maneuver nodes at hand I used the stock delta-v display to time the duration of the burn. I guessed when during the orbit I had to start the burn so that I get ejected from Kerbin retrograde in respect to the orbit around the sun. I do not do any staging for this burn because I do not want to produce any orbital debris.

After exiting Kerbals SOI I can see the orbit around the sun.

Before correcting my orbit, I use Valentina's Jetback to get her back to the craft. This time the drift was less than 1km. I generally try to keep the drift below 100km so that I can easily find the way back to the ship by using the target indicator.

Valentina is back at the craft.

I do a combined prograde/retrograde and radial/antiradial burn to get the values of apoapsis and periapsis match the value of the launch window calculator.

About half way to Eve, I cancel out my relative inclination to Eve's orbit. That is less efficient but makes it easier to get an encounter with Eve.

Entering Eve's SOI. I need to burn radially to get my periapsis down and normal or antinormal to reduce my inclination. I aim to get into an orbit with around 3° inclination around Eve because my intended landing position is close to the equator but not quite at the equator.

I got the periapsis down to below 20 km before undocking unneeded engines and fuel tanks to make sure they get deleted when encountering Eve. I notice that I can only undock the enigines and fuel tanks at the very back and not the fuel tanks docked directly to the structure holding the heat shields. This is a bug that often happens when doing complex docking operations where you undock and then dock back to the craft using another docking port.

To limit the drifting of Valentina, I get her to a position where she can bounce off in all directions and switch of the EVA jetpack. This uses a bit more EVA fuel than just letting go from the ladder but the velocity relative to the main craft is much lower then.

When approaching the periapsis I get Valentina back to the craft. The undocked parts that are not needed any more are on a lower trajectory and will get deleted soon when going into Eve's atmosphere.

Retroburning at Eve's periapsis to get capured into an orbit around Eve.

The captured orbit is very eccentric because I plan to spent about half an Eve year there before lowering it. This is because I want the part where the orbit passes over the northern hemisphere to be on the day side because that's where the projected landing area is.

Doing a retroburn at periapsis, spending the remaining fuel on the skipper engines side. The remaining Skipper engines with the attached fuel tanks are deorbited half an orbit later.

I continue to lower the orbit further using the Poodle engine. Here I undock the small fuel tanks to deorbit them. Unforunately from here on I cannot undock any further empty fuel tanks because of the undocking bug.

In a 90km x 119km orbit I have spent all the fuel planned for the transfer. Not being able to undock all spent fuel tanks increased the fuel consumption.

There is however still fuel in the two smaller fuel tanks that are radially attached. I don't need all that fuel for the transfer back to Kerbin so I can continue the burn using that fuel.

I got to a 92km x 92km orbit. The 2km above the atmosphere give me some time so that I won't directly hit the atmosphere when doing the deorbit burn of the lander.

The lander itself has no way to deorbit itself because its engines are covered in heat shields, so I have to push it into a suborbital trajectory and then quickly get the orbital stage back into a stable orbit.

Valentina is now also back at the craft. She is not in a command module, so I have to get her back on the ship after every time warp and you cannot time warp with a Kerbal on a ladder.

Next I have to deorbit the lander in a way that it lands at a location higher than 6km. This requires exact timing because the unmanned lander has nearly any control with a relais networks impossible around Eve.

[EveMaster]

Part 16: Landing on Eve

The  Eve lander and Valentina will land seperately because otherwise it would be too hot for Valentina even if she were protected by a heat shield. Jeb will have to stay in orbit because the lander only has one seat.

I deorbit the lander using the Poodle engine. Periapsis is around 68km to save fuel. The lander would survive a periapsis of 0km or even below that.

After doing the deorbit burn I decouple the orbital stage and quickly get it up into a stable orbit. When that is done I switch back to the Eve lander.

I do not have to worry much about the ship during reentry because it is well protected by heat shields. The lander even survives 4x pyhsical time warp during reentry. The amount of ablator on the heat shield is tuned to the amount needed to avoid unneeded mass. The seven large fuel tanks behind the heat shields are all empty. They were not intended to be on the lander but I could not undock them because of a bug. They do not cause any problems however. I disable SAS during reentry. This way the ship wobbles more, but I found that leads to more reproducible landing locations. The lander is designed to passively stabilize in the correct orientation because by the drag of the components.

After decoupling, the lander begins to tumble around 20°-30° from retrograde. If I were to redo this mission I would probably add a reaction wheel to this stage to better control this tumbling. All the reaction wheels have been decoupled with the heat shield, only the integrated reaction wheel of the probe core and the command pod remain. By timing the decoupling, I have a little bit of control over the landing position. I also activate SAS when the lander tumbles in a the correct direction for body drag to direct me towards the landing position.

At first, I deploy only one parachute. The asymmetrical parachute configuration gives me another few meters of drift towards the landing location.

Then I deploy the other parachutes and decouple all heat shields.

 

Landed at an elevation over 6000m. This took me around 50 tries. For more then half of them I targeted the wrong mountain. Then I used the small lakes to correctly identify the correct mountain for landing.

I deorbit the empty  fuel tanks and the Poodle engine and dock the remaining parts together again.

Valentina stores her jetpack in the orbital stage to save on mass before deorbiting.

The deorbiting stage can only hold prograde because the  probe core has no connection to the KSC and Valentina can't directly control it while standing on a ladder. However, she can control the craft in the pro/retrograde, radial/antiradial direction by walking up or down the ladder against a solar panel. This generates a force that rotates the craft. The craft started to burn with a radial component so it nearly raised to nearly 100km height. To get into the atmosphere, Valentina rotates the craft to burn more radially.

Most of the orbital velocity has been cancelled out. Waiting to drop a bit further into the atmosphere before burning up the rest of the fuel.

Then Valentina jumps of the craft. She quickly falls to denser parts of the atmosphere so she slows down and does not overheat.

Valentina uses her parachute to fly down to the Eve lander.

Valentina arrives at the Eve lander. The Eve lander has a mass of 42 tons as it stands now on the surface of Eve. That's more than twice the launch mass limit of the KSC launch pad in caveman mode.

Another screenshot with Valentina and the Eve lander, this time without GUI.

Valentina goes up the ladder to fetch an EVA experiment from the command pod. Planting flags is not possible in caveman mode, so instead she plans to do some experiment.

Valentina having fun with the EVA experiment which is teeing off a golf ball.

The next task is to get her back into orbit and dock with the orbital craft.

[EveMaster]

Part 17: Getting Back to Low Eve Orbit

Once Valentina has entered the command pod, I decouple all ladder elements.

Then I prepare the staging. I use aspargus staging with decoupling two opposite fuel tanks at the same time. The priority of the fuel tanks is set up in a way that each stage first uses the fuel in the top half to improve stability. In the first stage there are 6 Reliant engines for better performance and one Swivel engine in the center for gimbal. I also open the window for the Terrier engine already because I have to switch on this engine manually later on. The staging does not switch on this engine on due to the way I assembled the craft. The root part is not the command pod, but the central fuel tank. This central fuel tank is also the fuel tank that is only partly filled, what I only noticed when departing from low Kerbin orbit.

I launch up vertically with full throttle. I have the SAS set to hold position, but I have to constantly give manual input as well to stabilize the craft. Half a second without input and it would tumble out of control. The craft has no control surfaces and only the reaction wheels integrated in the command pod and one engine with gimbal for control. But I think the main problem is that the craft is no longer perfectly symmetrical because of parts migrated due to saving, reloading and time warp. However, I can keep the craft steady and decouple the first two side engines and fuel tanks.

When decoupling the second stage, the craft rotates to the wrong side.

But I am able to regain control. I now start with the gravity turn.

Decoupled the last side stage. The Swivel stage burns only very shortly because the fuel tank of this stage was already nearly empty on launch.

I decouple the Svivel engine and now fire the last stage which is powered by a Terrier engine.

Now holding prograde and continuing to build up speed.

I decouple the nose cone when leaving the atmosphere and a align the direct approach to the ship in orbit.

The trust to weight ratio of this stage is so good that I don't have to burn the engine all the time. I reduce my relative speed while approaching the ship in orbit.

Now the orbital stage is in sight and 34m/s of delta-v are left which is enough for docking. The ascent was not the most efficient. If I just tried to get up in any stable orbit without direct rendezvous I could have saved a bit of delta-v. 

Docking was more difficult than expected. I aligned perfectly and just would not dock together. For small crafts like this docking without RCS should not be a problem. Then I noticed that I had turned the docking force down to 0 for the last redocking in orbit to avoid the parts from drifting away. I turned the docking force back up and then the docking succeeded instantly.

Now I just have to get Valentina and Jeb safely back to Kerbin to finish off this mission. Two things make this more difficult than planned: I used up some of the fuel of the extra fuel tanks already for deorbiting the Eve lander. And I also forgot to bring solar panels for the return stage. The engines of this stage also produce no electricity. Fortunately I don't have any probe cores on this craft that constantly draw energy. I just need the energy for SAS. I will have to turn the strength of the reaction wheels down and conserve as much electricity as possible.

[Guest The Doodling Astronaut]

Came here looking for usual good stuff from Evemaster

Then I found gold content from @EveMaster

 

[EveMaster]

Part 18 and Final Part: Return to Kerbin

To know when the transfer window back to Kerbin is, I again consult the launch window planner. I go rather late in the transfer window because then Eve and Kerbin are closer together, so I arrive rather too early at Kerbin. When arriving too early I can correct for this by first going higher than Kerbins orbit, when arriving late I can only try to get a Kerbin encounter several orbits later. I don't directy eject back to Kerbin but go into an elliptical orbit first. For that I just guess the time when I have to start the burn to later get the correct ejection angle.

The top fuel tank is now emtpy and I decouple it in a suborbital trajectory.

I raise the periapsis again to be above the atmosphere and do the ejection burn at the next periapsis. I don't count delta-v this time but just guess when to stop the burn. From previous Eve missions I know that after getting an ejection trajectory from Eve it only needs a small burn to get to a Kerbin transfer trajectory.

After leaving Eve's SOI, I notice that I still have to burn a bit prograde to get an Eve encounter.

By trial and error I find out that I have to go a bit higher than Kerbin's orbit to get an encounter when crossing Kerbin's orbit the second time. To make it easier to get an encounter, I eliminate my relative inclination to Kerbin about halfway to Kerbin.

When I reach Kerbin, my trajectory goes outside of Minmus' orbit.

I burn radially to get an encounter with Kerbin for aerobraking. The altitude for aerobraking that I go for is higher than in this screenshot. If found out that 49.5 km works best.

Aerobraking at Kerbin into a retrograde orbit. The altitude is as low as I can go without exploding. The Terrier engine gets very close to its temperature limit.

After aerobraking, I only need a small retroburn to get captured in Kerbins orbit. In this screenshot it looks as if I'm already in a stable orbit, but I still need a small bit of retroburning. Without patched conics it might seem that you are in an orbit, but you are actually not because the apoapsis is outside the sphere of influence.

With the apoapsis at the height of minmus orbit, I should be safe.

Correcting the inclination of my orbit to 0 using Mun's orbit as a guide line.

Aerobraking into a lower orbit over multiple orbits.

Passing Bill's ship with a relative speed of 4620m/s because Bill is in a prograd orbit and we are in a retrograde orbit. Bill has been in low Kerbin orbit for all of the Eve mission because I forgot to bring him down.

So I deorbit Bill's craft and come in for a landing close to the KSC.

Landing Bill in the ocean next to the KSC.

Preparing for the landing of the ship that has been to Eve. Only a small amount of fuel and electricity is left.

The deorbit burn has been performed. There still it a tiny bit of fuel left in the part of the ship that has been on the surface of Eve.

Approaching the Kerbal Space Center from retrograde direction. Burning the last drops of fuel.

Now the ship has slowed down. I still wait a bit deploying the parachutes.

Gliding down to the Kerbal Space Center.

The craft landed on the side of the runway.

Valentina and Jeb seem to be happy being back on Kerbin and pose for a photo in front of the Eve return craft.

The same screenshot without GUI.

Screenshot of the mission report for recovering a ship that has been on the surface of Eve with the un-upgraded buildings or the Kerbal Space Center in the background.

The caveman style mission to Eve's surface and back has now been successfully completed.

I hope you had as much fun reading this mission report as I had playing this mission.

[Vanamonde]

Well, that's an impressive feat. 

[CastleKSide]

Dang impressive

[Kerb24]

Impressive.