Flight of Kaotea: a Jool-5 mission report

[QF9E]

After my adventures on Eve (see https://imgur.com/a/di5MCog for the final mission, https://imgur.com/gallery/COm2aSI and https://imgur.com/a/fzHlZ44 for the opening acts) it is now time for another classic adventure in the KSP universe: the Jool-5 challenge. This is my first ever Jool-5, and I'm planning to post a series of mission reports of the mission as it unfolds, starting with the design and planning phase.

 

A. The plan

A few days ago I came across a very interesting way of doing Jool-5, with a single lander. After each landing, the craft ditches stuff it no longer needs and continues as the lander for the remaining moons. This mandates that the moons are visited from large to small. I arrived at the following order:

1. Laythe
2. Tylo
3. Vall
4. Bop
5. Pol

There might be a case for doing Tylo first, as it needs more delta-v than Laythe, but I found this order to work well: This way I don't need to carry specialized parts for atmospheric descent for longer than necessary.

I also decided to take the two-Kerbal Mk2 Lander Can as the core of the lander. While by no means optimal as far as payload mass is concerned, reports from past missions indicate that strapping Kerbals to a chair for years on end is not exactly beneficial to their long-term health. Single Kerbal capsules are a lot better in this respect, but can lead to near-suicidal bouts of loneliness. So a two-Kerbal capsule it is.

Since I don't want to bring any more fuel on my lander than necessary for each landing, I will do a Moon Orbit Rendezvous for each landing. A separate command and service module will stay in orbit, together with a fuel depot to refuel the lander to prepare it for the next landing. The CSM will include the Kerbin return vehicle, for which I am planning to use the Mk1-3 Capsule. It will also contain an interplanetary / intermoon stage powered by Nerv rockets to go from Kerbin to Jool and back and travel between Jool's moons.

 

B. The lander

My Jool-5 lander in its different forms. From left to right: the Laythe lander, Laythe ascent vehicle, Tylo lander, Tylo ascent vehicle upper stage / Vall lander, and finally Vall ascent vehicle upper stage / Bop and Pol lander.

It will use chutes and airbrakes to land on Laythe. These will be jettisoned for Laythe ascent, after which the nose cone will de jettisoned. After refueling, the remainder will land on Tylo, where it will land with a still partially filled lower stage. During Tylo ascent the lower stage will be decoupled once empty, and Tylo orbit will be reached with the upper stage only. This upper stage then becomes the Vall lander, where the process is repeated: during Vall ascent the lower stage of the Vall lander is decoupled when empty, and Vall orbit will be reached by the Vall ascent vehicle upper stage, which then becomes the Bop and Pol lander. Since Bop and Pol are so small and so similar in size and delta-v requirements, we will re-use the same lander for both.

Current status: design is being finalized. I test-landed it yesterday on all of Jool's moons, and performance was good to very good on all moons except Tylo. Delta-v totals for Tylo were pretty marginal, but we may be able to conserve some fuel by doing a more aggressive suicide burn.

TODO: 

• Test optimized descent and ascent profiles on Tylo;
• Test with bigger fuel tanks for the lower stage to get some delta-v reserve for the Tylo landing, if the previous test shows that this is necessary. This also means additional tests on Laythe, especially for buoyancy: after much fine-tuning, the current craft stays upright in Laythe's oceans, and I'd like to keep it that way;
• Test with ladders added on Laythe and Tylo. I haven't tested with ladders yet, and I'd like to know what these do to the balance of the rockets (since with ladders the craft is slightly asymmetrical) and the amount of delta-v on Tylo. I also want to know if a Kerbal can use these ladders, as I have had mixed results with ladders in the past;
• Test with partial fuel load on Laythe. Hitherto I've flown ascents from Laythe with fully fueled upper stages (and enabling cross-feed to use its fuel in the lower stage when needed) but with empty upper stages the lower stage should be able to comfortably reach Laythe orbit by itself.

I expect the lander to be finalized today.  

 

C. The command and service module

I haven't started the detailed design of the CSM. During launch the CSM should be on top, for safety reasons. After launch I plan to do an Apollo style transposition and docking maneuver to turn the CSM around and dock with the fuel depot, which will have docking ports at either end. The lander will be stored underneath the fuel depot during launch and dock with the remaining docking port on the fuel depot for refueling after each ascent.

TODO:

• Make a detailed design of the CSM and fuel depot.
• Figure out the size of the fuel depot
• Figure out delta-v requirements for going to Jool and back and the fuel requirements for the interplanetary stage
• Test the CSM in LKO, with a dummy lander

 

D. The launch vehicle

To be determined after the entire rest of the stack is complete. I think it will be a Falcon Heavy type design, with two large liquid fueled boosters, a liquid fuel core stage and a vacuum-optimized upper stage.

 

Appendix I. The details of my KSP setup

For this adventure I am running stock KSP without the DLC (which I don't own). No modded physics or parts. While I do run MechJeb I am planning to not use its autopilots - I like to fly everything myself. I only use it for its information displays, particularly its trajectory prediction through Laythe's atmosphere. I also make heavy use of KER and Precise Maneuver. I've been using HyperEdit and VesselMover a lot during testing, but I will disable those for the actual mission.

Edited November 27, 2019 by QF9E

[QF9E]

A quick update from my Jool-5 mission:

I tested the lander again on Tylo and Laythe: this time I had 500 m/s to spare after Tylo, so I don't quite understand what I did wrong yesterday. I tested it on Laythe with reduced fuel load, which went way better than I had anticipated: I had more than 800 m/s remaining once back in orbit. I also tested the ladders, which turned out to work just fine. So with that, the lander is finished.

I also designed a command module, with a launch abort system (including boost protective cover, made from a fairing) on top. I tested the LAS both for a pad abort (ok, but hectic - looks remarkably like the pad abort test from SpaceX's Dragon 2 from a few years back) and a max-Q abort (goes fine - only remember to direct the craft retrograde after the abort and before decoupling the LAS tower. The LAS also decouples just fine once above the atmosphere.

Pad abort test. After this, you need to quickly stage a number of times: jettison the LAS and boost protective cover, deploy drogue chute, deploy main chutes and jettison heat shield. All while the capsule is tumbling through the air.

I then tested the heat shield, by doing a re-entry from an elliptic orbit around Kerbin all the way out to the edge of its SOI. This went without a hitch, making a direct re-entry from interplanetary trajectory possible.

I then did a dummy Kerbin orbit of the entire stack, with approximate tankage for the interplanetary stage and the fuel depot. I tested the transposition and docking maneuver, as well as undocking and re-docking the lander. All went without a problem, so the idea is sound. I noticed some minor stuff for improvement, such as not having a shroud on the CSM engine: during the test, the debris from the shroud got in the way of the transposition and docking.

Dummy spacecraft stack in LKO. From top to bottom: dummy interplanetary stage, command module, dummy fuel depot and lander

And finally I calculated the amount of fuel needed to refuel the lander and made a design for the fuel depot. It's not 100% finalized yet but it is currently in two parts: the bigger part contains the fuel for the Tylo landing, and can be jettisoned after refueling in Laythe orbit, while the smaller part supplies fuel for the rest of the mission. I even added a tunnel in the middle (from structural fuselage parts) to have a bona-fide route for Kerbals to transfer between the CSM and the lander.

Preliminary design for the fuel depot. Note the docking port on top: there's another one at the bottom, and both of them are connected via a tunnel through the middle of the fuel depot

To finish, I determined the delta-v requirements for all phases of the mission. For the moon-to-moon transfers I used the transfer window planner mod, but for the route from Kerbin to Laythe I put a test craft into LKO, plotted a route using the maneuver planning window and actually flew the route to see how much delta-v is required. For the return route from Pol to Kerbin I did the same. The following table summarizes my findings:

Kerbin to Jool SOI	2500 m/s
Laythe orbit insertion	600 m/s to edge of SOI; 1500 m/s to circular orbit
Laythe to Tylo	1500 m/s
Tylo to Vall	1100 m/s
Vall to Bop	900 m/s
Bop to Pol	500 m/s
Pol to Kerbin	1400 m/s without LKO insertion burn

Based on this and the known mass of my craft it should be possible to allocate fuel and engines for the interplanetary stage. However, given the ever-changing mass of the fuel depot and lander this is not entirely straightforward and I think it will take some time to get right.

[QF9E]

A final design update: 

I redesigned the lander. I wasn't happy that the docking port was underneath a fairing in the old design, and therefore inaccessible until after the Laythe landing. The new design has the docking port accessible at all times. This makes for a less aerodynamic vehicle during Laythe ascent, but given that I have a lot of fuel reserves for Laythe that is acceptable.

I also finally managed to get the interplanetary stage done. Powered by 7 Nerv engines I found it hard to estimate the correct amount of fuel. Eventually I built up the stack back-to-front: I started with the command module, adding fuel until it had enough delta-v to go to Kerbin from Pol; I then added the Pol lander to the stack and added fuel to the interplanetary stage so that it had enough delta-v to go from Bop to Pol, and so on. It was laborious but straightforward, and I hope I have got it right. There's no use testing it without also doing the landings, so I'm just going to do the real mission now.

But before we light this candle, there's one very important thing left to do.

 

The Christening

"I christen this ship Kaotea, the White Cloud. Like its namesake, the great canoe Kaotea that brought the first Kaori people to our beautiful island, may it keep its crew safe during its mission to the moons of Jool." -- Jacinda Kerman, prime minister of the remote island nation of New Kerbinland.

Kaotea

 

Edited November 27, 2019 by QF9E

[QF9E]

Launch day

The launch window I will be using. I started a new sandbox game for this mission, with Normal difficulty

Dawn breaks on launch day. Time to roll out Kaotea and do some pad checks

Kaotea on the launch pad. I will launch once the KSC is in full daylight. Jeb, Val and Bob are strapped in, waiting for liftoff, apprehension on their faces: it is not every day you sit on top of 250 tons of explosives. They can take comfort in the fact that Kaotea has a fully functional launch escape system ready to take them to safety if the need arises

[QF9E]

Launch

10 ... 9 ... 8 ...7 ...6 ... 5 ... 4 ... 3 ... 2 ... 1 ... Ignition and liftoff for Kaotea, on a voyage of discovery to the moons of Jool!

Kaotea in flight. One of only a few good-looking screenshots I took from the launch: I like to have a side-on view when flying rockets but this launch is almost directly towards Kerbol, so most of the craft is in shadow when viewed sideways on. Fortunately I had some time during the 2nd booster burn to find a better camera angle.

Kaotea in 75 x 75 kilometer LKO. The different parts of the craft can be easily discerned: from left to right we have the launch vehicle core stage (which still has 300 m/s delta-v left, so I am not discarding it yet), followed by the Kerbin departure stage (which is powered by a Rhino - I wanted to have decent TWR for my trans-Jool injection (TJI) burn to prevent a laborious multiburn), the lander, the fuel depot in orange and grey, the interplanetary stage (7 Nervs and a lot of fuel) and the command module. After TJI I will decouple the command module with the interplanetary stage and dock it in reverse with the fuel depot. Not only does this more closely resemble operations with Apollo, it also enables my Kerbals to use the rest of the living space in the ship: the tunnel through the middle of the fuel depot and the lander.

Spoiler

I will put details of each phase of the flight inside spoilers, in an effort to not create overly long posts. This spoiler contains a blow-by-blow report of the launch into LKO.

1st set of boosters separate:

2nd set of boosters separate

MECO-1

Planned circularization burn

Fairing and launch espace system jettison. I would have liked a picture of the LES flying away but it was too fast...

MECO-2 in a 75 x 75 kilometer LKO

At this point I realized I still had the Hyperedit and VesselMover mods enabled. I will disable them right away, and I hope that this detailed report of the launch is proof enought that I did not use them to cheat on the way to LKO.

 

Edited November 27, 2019 by QF9E

[QF9E]

To Jool! (And Laythe...)

Goodbye, Kerbin!

Hello, Jool! The dark silhouette on the left is Laythe

Orbit insertion burn around Laythe. This shot was taken a bit earlier than the previous one

 

 

At one point I ran out of electricity due to a probe core that had not gone into hibernation, but I managed to get the batteries recharged. The craft was tumbling at that point, and enough sunlight hit the solar panels that I could stabilize the craft and point the solar panels to the sun to fully recharge.

I also forgot to turn the CSM around to re-dock with the fuel depot and give the crew some more living space. I rectified this situation once the electricity crisis was over, and before Laythe orbit insertion:

Spoiler

In this spoiler, a series of screenshots of the maneuvers I performed to arrive in Laythe orbit.

First the Trans Jool Insertion burn, both as planned:

And realized:

Plane change burn to get a closer encounter with Jool and its moons:

And the planned encounter with Laythe:

And the realized encounter with Laythe:

The electricity crisis:

And its resolution:

Course correction to lower Laythe PE:

And the result:

Laythe capture burn as planned:

And the resulting orbit:

 

 

Edited November 27, 2019 by QF9E

[QF9E]

Landed on Laythe

I've successfully landed on and lifted off from Laythe. This turned out to be a lot harder than anticipated: the aerodynamics of my craft were a lot different (read: less stable) compared to testing. I tested my lander in an old sandbox, maybe Laythe or its atmosphere have changed in the meantime? The consequence of this is that I needed all the fuel in the lander to get back into orbit. I had hoped to build up a fuel reserve but that hasn't materialized. This should not be a problem if my calculations have been correct, but an extra reserve of fuel would have been nice.

Landing in Laythe's ocean under parachutes:

Ascent from Laythe. We took a surface sample of the water. I also tried swimming to shore to plant a flag but that took too long.

Rendez-vous with the mothership. Yes, the lander was running on fumes by this point.

Discarding most of the fuel depot after refueling the lander:

More details in spoiler below:

Spoiler

In this spoiler the details from my orbital, landing and surface maneuvers on Laythe

Planned entry burn: note the discarded Kerbin departure stage on an escape trajectory (white line).

The landing zone, as predicted by MechJeb's landing guidance. I chose to land just past an island, in the hope of staying close enough to land to be able to swim there.

Undocking the lander:

Atmospheric entry. Heating was much higher than I tested with due to my elongated parking orbit.

Deploying chutes once past the island. I hoped to be able to fine-tune the point of landing by choosing the correct moment for chute deployment, but this turned out not to work very well:

Chutes fully open:

Landed! One of my design goals for the lander was that it would stay upright once landed in the ocean. I only partially succeeded: I found that I needed SAS radial out to keep the craft upright. I usually aim for passive stability in my designs.

Bob attempts to swim to shore to plant a flag. This took too long, so I decided to cut the attempt short and return to the lander.

Discarding the ring of parachutes. This arrangement worked really well and functioned as an airbrake during atmospheric entry. The previous version of the lander had actual airbrakes but these turned out not to be necessary. I used two sepratrons to boost the ring away from the lander. I had limited the thrust of one of the sepratrons so that the ring would not launch straight up and risk a collision with the lander.

Liftoff!

Once out of the atmosphere I jettisoned the no longer needed aero surfaces

Initial Laythe orbit of the lander. I had way less fuel remaining than anticipated based on testing, so I was unable to raise the lander to the mothership orbit.

I therefore decided to raise the lander orbit as high as it would go and lower the mothership orbit to go pick up the lander.

lander in sight:

Docking imminent:

Docking complete:

Refueling the lander in preparation for the Tylo landing:

Jettisoning fuel depot #1:

The remaining spaceship, with fuel depot #2 still attached. Yes, this is all the fuel I need for Vall, Bop and Pol. Tylo really is that much harder to land on.

Visual proof that fuel depot #1 is now completely empty. I deliberately designed fuel depot #1 to be a little on the small side, in order to not have to carry fuel that I would ultimately not use. The plan called for jettisoning the fuel depot before flying to Tylo to save weight, and if I had had any fuel remaining in the fuel depot I would have had to jettison it non-empty. 

 

Edited November 30, 2019 by QF9E
added details of Laythe orbit operations

[QF9E]

Laythe to Tylo

Laythe to Tylo escape burn:

In Tylo orbit. Lander undocked in preparation for the landing:

Tylo surface operations. Val's lighthearted comment woke the Kraken...

... which decided to destroy the lander during staging on ascent:

But fortunately I was able to keep the mission alive by reloading and jettisoning the interstage fairing before staging. Note, by the way, the center engine: that is the engine of the lander's third stage, which is firing through a decoupler and the Doughnut tank in the center of the 2nd stage. This way I got a higher TWR, which improved the lander efficiency during Tylo ascent, without the mass penalty incurred by an additional engine. It's basically the same as asparagus staging but with inline stages.

During subsequent orbital maneuvers I only used the 3rd stage center engine, as it is a Spark, which has higher ISP than the Twitch engines of the 2nd stage.

The disadvantage of this technique, however, is that the game's delta-v calculator does not understand what you are doing and gives erroneous numbers or none at all.

Back in orbit, overflying the landing site:

Goodbye, Tylo! Part of the interplanetary stage had run empty by this point and was jettisoned, together with two of the engines:

I've decided not to do spoilers anymore with mission details. I've got the pictures on imgur anyway, so I'll just link to that for the detailed mission report: https://imgur.com/a/CPiMpJ9

Edited November 30, 2019 by QF9E

[QF9E]

Tylo to Vall

Hello, Vall!

De-orbit burn

Surface operations. Jeb is not afraid of the Kraken, despite what happened on Tylo:

Staging during Vall ascent. Probably my favourite picture of this entire trip. The lander second stage is also the part of my craft that I enjoyed designing the most. Its "extended doughnut" design meant that the lander could be very compact.

Planning the transfer from Vall to Bop. This turned out to be quite hard due to the difference in inclination. But with the phase angles drawn in I managed to find a launch window that coincided with the line of nodes.

Once again, a more detailed mission report can be found at https://imgur.com/a/CPiMpJ9.

 

[QF9E]

Bop

Hello, Bop!

Jeb could not contain himself, as the trip was becoming routine. He just had to show that Bop's low gravity means that he could jump over the lander. Meanwhile Bob had planted a flag and collected a surface sample.

Docking with the mothership after Bop ascent:

The Bop to Pol transfer orbit:

once again, a detailed mission report for this part of the mission can be found at: https://imgur.com/a/CPiMpJ9

Edited November 30, 2019 by QF9E

[QF9E]

Pol

Hello Poll! And Jool!

Our initial landing spot. Much too steep for comfort ...

So I decided to find a better spot, where Val and Bob plant the final flag for the mission and collect the final surface sample:

One last time, our intrepid duo ascends into orbit from the surface of a Joolian moon:

... before docking with the mothership for the fifth and final time. After docking, Bob performs a short EVA to move the surface samples to the command module:

[QF9E]

Back to Kerbin

Kerbin transfer burn, and a final close-up view of Jool.

Back in LKO:

Splashed down in the ocean. Note that I only have 4 surface samples: I somehow lost the Laythe sample after doing multiple quick loads. As I've written above, the Laythe ascent proved to be very difficult, much more so than I had anticipated.

And only four flags, as my Laythe landing happened too far from shore. One other significant object shown here is the Kaotea lander in LKO. I took the Pol lander back with me to Kerbin as I had plenty of delta-v left. Plans are being made to retrieve this priceless spaceflight artifact, the first lander that has been to 5 different moons to make it back to Kerbin.

The other objects shown here are bits of the fuel depot that I discarded in the Jool system. 27 other bits of debris are not shown here: the parachute ring discarded on Laythe accounts for most (16) of them; among the other bits of debris are several highly radioactive pieces of the interplanetary stage. One of which has crashed on Kerbin's Highlands...

More details here: https://imgur.com/a/FDwQkG0. Imgur was acting up, so I had to split my detailed mission report into three different imgur albums. For completeness' sake, these are the links to all three:

1. https://imgur.com/a/3HRkZNj
2. https://imgur.com/a/CPiMpJ9
3. https://imgur.com/a/FDwQkG0

 

[QF9E]

And as a final post, let me thank @JacobJHC for running this excellent challenge.

Jool-5 is one of THE classic KSP challenges, and I am proud to have finally completed it. However, if I am completely honest there's also a lot of repetition involved, which makes me rate Jool-5 a little bit below Eve Rocks, which has been my favourite KSP challenge to date. It also did not help that the mission architecture that I chose, with a separate lander and mothership / fuel depot, means you have to do quite a bit of extra work in the form of rendez-vous and dockings. And to make it even more repetitive, I've done something very similar before: during my career playthrough I visisted all the biomes of the Mun in one mission, also with a separate lander and a fuel depot / mothership in orbit.

TL/DR: I enjoyed myself with this mission, but you won't see me do another Jool-5 any time soon.

Edited November 30, 2019 by QF9E

[QF9E]

Postscript: retrieving the lander

As I wrote previously, I planned to retrieve the lander that was stuck in LKO. I built a retrieval vehicle, a rocket SSTO, with a cargo bay to go get the lander. This turned out to be harder than expected, as I found it pretty hard to maneuver an object that can no longer be steered into a cargo bay. But with a bit of luck and patience, I succeeded. I tried to use MechJeb's landing guidance to re-enter and land on the KSC but despite my best efforts to get the landing point on the KSC I landed a few kilometers short. My guess is that MechJeb does not deal correctly with airbrakes. But as a first try I am quite happy with the result.

Liftoff of Waka ["ship" in the Kaori language] on its way to retrieve the Kaotea lander. 

The Kaotea lander safely inside Waka's cargo bay. This turned out to be a lot harder than expected, as the lander cannot be controlled without crew. It took a lot of patience and some gentle nudges to get the lander in the cargo bay with its docking port aligned to the docking port of the cargo bay.

Waka under parachutes, with the lander safely stowed inside. I aimed for the KSC but came up short. KSC visible in the distance.

Landed. In my imagination the lander was then loaded onto a truck and paraded all across Kerbin.

More detailed mission report: https://imgur.com/a/TYgtHxF

Edited November 30, 2019 by QF9E

[JacobJHC]

Most impressive! Especially the lander recovery!

[KerballingSmasher]

Noice!