Another Eve attempt

[Galane]

My latest test for a mission to send to Kerbals to Eve, land and retrieve them both.

Eve-test-flight by g_alan_e, on Flickr

The only image taken of this test. The crew was under orders not to take more during the trip as it was a test and KSC didn't want any pics around if thins went worng. Once the rest of the debugging is done and the mission is made in the "real" save, there will be plenty of pics.

The advent of the Kerbodyne parts and part changes in .24.x that screwed up the balance of my previous Gilly refueling lander, and the sheer number of parts in the previous assembly - forced a redesign of much of the vehicle.

The original plan, lacking the last two sidesaddle boosters.

screenshot8 by g_alan_e, on Flickr

Instead of docking a rover and a rover+lander atop the Eve lander, the new plan launches the original Kethane conversion rover with a pair of small drills added. The Gilly refueling lander is also launched on the same rocket, built atop a massive ThunderMaximus 288 tank.

The first assembly phase brings up all four sidesaddle boosters at once (coupled under a Kerbodyne scaled 1-to-4 adapter) then docks to the core so the boosters can be moved over one at a time. The same launch also brings up a pair of small Kethane scanning satellites to put into Eve orbit. The Gilly lander has scanners so it's its own satellite when not landed.

The booster carrier is deorbited so the Eve lander can be launched and docked nose to nose with the transfer ship. Much use is made of Quantum Struts, also Omni Docking ports to have 3 concentric docking connections.

After boosting to a high enough orbit to be able to attain high warp speeds, a couple of tankers top up the fuel, oxidizer and mono, then it's ready to go.

Test results were mostly as expected, since nearly all parts had been tested and developed multiple times using hyperedit to place the components in the correct locations to confirm proper operation.

The rover and lander for Eve use nowhere near the full capacity of their fuel tankage to land so I move enough to the ThunderMaximus tank so they'll be touching down nearly on fumes. The rover's tanks and engines must be emptied and jettisoned before raising the landing legs or the short drop will damage wheels and make some parts fall off. Solar panels must be retracted before making any movements with the rover!

I hesitate to reduce the tankage on the rover because without taking most of its fuel to the big tank, the core and can might not have been able to get to Gilly. But doing so might save some fuel going from Kerbin to Eve due to less mass to push. I am going to remove the RCS thrusters and mono tanks from the rover since it doesn't need to dock now. They are a vestige from the original plan.

The key to the successful ascent from Eve is the group of six Hooligan Labs inflatable "parachutes". MechJeb's default/automatic ascent profile for Eve is just flat out incorrect. I use a gravity turn start of 35KM, 52% shape, turn end 100KM at 0 degrees.

Ascent process, after refueling, EVA to repack radial chutes on lander can and remove/discard the ladder. Board then stage to dump the 6 chutes on top of the side boosters. Hit 0 to inflate the bags. Stage around 2KM to drop the landing legs. Wait until altitude reaches ~24KM and speed is still 100+ meter/second then engage Ascent guidance. About 2KM later stage to jettison the airbags then sit back and watch Mechjeb take it on up.

This works without Stock Drag Fix. I built the lander before that existed. However, with SDF the can makes it to orbit with some fuel left in the T800 tank instead of just a somewhat less than full T400 - so rendezvous is no worry with SDF. SDF also saves a bunch of fuel in the launches from Kerbin.

The one part that was a bit nail biting was getting the Gilly lander out from between the Eve lander and Rover/transfer. The Eve lander only has a total of 120 units of mono and RCS jets only on the core parts. I just used SASS to TGT+ on both and carefully scooted in to a manual docking.

The final test prior to launching the full mission was 'porting the core with Eve return stage on top to Eve then flying back to Kerbin. Somehow I managed to get a Mun encounter which screwed things up to where I was just able to get into a very high Kerbin orbit then send up a tanker. How it did that when Eve and Kerbin/Mun aren't in the same plane and I was coming in well off the ecliptic...

The part that did NOT go well was refueling at Gilly. The larger lander was still too small VS that giant Thunder Maximus tank and due to the warp limits and Rendezvous Autopilot having some issues at such tiny orbit diameters, it would've taken a week of realtime to refuel. I saved the VAB folder and mercilessly deleted that mission folder rather than use hyperedit to fill the return vehicle, since I already knew it could make it back.

Since I didn't drop the second pair of sidesaddle boosters until circularizing into an orbit just outside Gilly's Apoapsis, I'm going to attempt to equip them with more docking ports and lander+kethane parts on top to move to their sides to convert them into a pair of very large fuel tankers so the big tank can be filled in far fewer flights. I'll then be able to directly dock the Eve lander to the rover and won't have to get a lander out from between.

I'd thought about dropping parts at Gilly to convert the entire core into one massive, self refueling, lay-down lander, but that's perhaps a bit too crazy. Or perhaps Kimball Kerman is actually a Lensman and such massive ships landing on planets are an everyday thing... 'Course then he'd have an inertialess spacecraft drive and the whole trip would only take five minutes.

[Galane]

Rather than begin modifications on the existing crafts, I did some experimenting on big landers for Gilly, specifically converting the side boosters.

screenshot29 by g_alan_e, on Flickr

Despite being heavy towards the engine end when empty, it was able to land without too much drama. When all full the COM is pretty close to the center of thrust of the landing assembly. Thus it was able to lift to orbit even easier. There's a radial decoupler stuck on the bottom of the Rockomax as a block to stop Ascent Guidance from activating the big engine.

With the success of the one, I tried to double up and land the entire ship to see if it would be possible to refuel all in one go.

screenshot31 by g_alan_e, on Flickr

That almost worked. It's tail heavy but MechJeb was managing it until the suicide burn which made it rotate and it couldn't recover before one side crashed down. I was using TAC fuel balancer on everything. Should have used it to keep the cone shaped adapter and other tanks at the front full as a counterbalance. I forgot to save prior to starting the landing so to try again I'll have to reassemble it.

I tried doing a rendezvous but with Mechjeb's iffy piloting around Gilly, that wasn't working so well. It misses nodes with the big craft, uses too much thrust on the unbalanced landers and insists on doing multiple plane matches that it shouldn't need to do.

For the actual mission I'll get into Gilly orbit and dock the landers together after dropping them so only one rendezvous will be needed to assemble the whole thing for landing. That is assuming in tests I can land the huge thing without crashing.

Might have to move the docking ports aft a bit. Would be nice if MechJeb could do automatic differential throttle control on engines.

[Galane]

It dawned on me that I could balance the lander by pointing the big engines in opposite directions and with two of the tallest Kerbodyne tanks I'd double the fuel capacity. Not quite as convenient as landing the whole ship but far less dangerous.

Here it is after assembly testing in Kerbin orbit, ready to warp to Gilly. To assemble I first undocked one converter and docked it to the outside port on one booster then decoupled it from the big tank. Then I undocked the other converter with the center piece and docked that to the side port of the first booster. Next I undocked the second converter and flew it back to get the second booster. Finished up by docking that to the other side of the center piece.

MechJeb's docking autopilot handles awkward and off-balance crafts quite well, but I'm going to add more RCS thrusters that should make it easier.

Unfortunately this still requires temporarily separating the Even lander from the transfer core, but I'll be able to fully refill all the tanks before going down to Eve, which should relieve any fuel anxiety for the return to Gilly. (Might even chance a legless landing there with the can to plant a flag.)

screenshot34 by g_alan_e, on Flickr

I also figured out how to launch the side boosters already attached so I can skip the launch to bring them up and all the time docking. The downside is they have to be mounted on TT-70's because I could not find a way to assemble them onto radial mounted docking ports.

For the trip to Eve they'll be moved to the sides of the big tank, nestled between the side boosters. (Note to self, do not forget to mount Kethane scanners somewhere where they can be put in Gilly and Eve orbits.)

Hey, look, it lands great! (The 6x1 panels have been upped one notch in size with tweak scale.)

screenshot35 by g_alan_e, on Flickr

And it lifts off when full!

screenshot36 by g_alan_e, on Flickr

But it will need more RCS jets. Even with two of the Kerbodyne upscaled reaction wheels and the wheels in two RGUs and the various RCS jets installed it handles terribly when all the tanks are full. Empty it whips around with speed and precision.

With it full, Rendezvous Autopilot and Maneuver planner were unsuccessful at pretty much everything. I tried just a simple plane match and it finished a few degrees off and somehow after starting from a circular and centered 42KM orbit it got into a slightly elliptic orbit with periapsis below 40KM and apoapsis almost 43KM. So I tried to circularize at apoapsis. It got a bang on perfect circle, but with the periapsis now at only 38 KM. I want to keep things over 40KM because below that it's like watching molasses run in the middle of winter.

I've also run into these circular but off center orbits with MechJeb around Ike, Mun and Minmus. Seems the smaller the body and smaller the orbit, the more iffy it gets.

Edited September 9, 2014 by Galane

[Galane]

Another test launch then stuff moved around.

screenshot32 by g_alan_e, on Flickr

I'm going to add a duplicate of the center piece for the lander and dock it to the side of the big tank like I have here. One of them will be a throw away but I can't think of a better way to shorten up the ship by docking the Eve lander directly to the top of the rover. Shorter will also remove some or all of the flex I was getting, even with quantum struts.

The two satellites can either ride along on the outer docking ports on the side boosters or on the ends of the Gilly lander centers. On the centers will make it easier to fuel up prior to jetting away from Kerbin to Eve.

Another thing I need to check. I have four of the quad chamber engines on short Kerbodyne tanks under the big tank then use the fuel balancer after they drop. Upon reaching orbit I pull all the fuel into the big tank - just over 49% full. I need to do a launch doing fuel balance all the way to see if it uses more or less fuel keeping those higher thrust engines. If it's more efficient this would be my most massive SSTO rocket.

Edited September 10, 2014 by Galane

[lajoswinkler]

I've never seen something so grossly big on Gilly. LOL

[Galane]

Since Alan Aerospace Recycling and Packaging (usually) disdains the use of parachutes, our spacecraft tend towards the large sizes. Eve proved to be a bit of a challenge so the R&D focused on just using a minimum amount of parachutes.

There are none on the unmanned rover. During testing I tried a single chute and two chutes but it caused bad oscillations and crashes during the suicide burn. That may have been fixed somewhere in the many builds of MechJeb since. No need to go back to chutes since the rover can land without them.

With the big Gilly lander only using the tiny radial mount Kethane tanks, I'm thinking of doing away with the large tank on the rover and just drilling, converting and pumping simultaneously. That will make the whole assembly shorter. Shorter = faster turning. Faster turning saves mono!

[xtoro]

Eve is a harsh mistress! As for mining on Gilly, go big! You can get some massive full tanks off of the surface with little power, so send some huge tanks, lots of them! Just make sure all the tanks are empty for the Kerbin->Gilly trip to save yourself some delta-v.

[Galane]

That's why I'm repurposing two of the upper stage side boosters for the lander. I'm going to try a way to get rid of the big engines on them to make it more nimble at turning because MechJeb's rendezvous autopilot overcontrols it with RCS so it wobbles back and forth a lot when full instead of smoothly rotating and stopping on the correct heading.

[xtoro]

In MechJeb you can set it to not use RCS for rotation and only use the reaction wheels. In the MJ menu, open up RCS Balancer, turn on "Smart Translation" and turn off "Use RCS for rotation". Then RCS will only be used for translation, and not for rotating. Saves some RCS fuel too. If you find your ship is much too heavy to rotate using only the reaction wheels, then add another stronger one to your ship, and make sure you have enough power to use it.

[Galane]

Or just shut off RCS completely with R. I need to go see if there's another MechJeb update. The last one I downloaded has a problem with SASS where it's not relinquishing control to the ONE part set as control from here.

[Galane]

The problem was KSP suddenly having a fit with Quantum struts mounted on Oscar B tanks, as if they're no-physics parts.

Final, complete mission report here.