Jool-5 Challenge Report - by norcalplanner and KABOOM (picture heavy)

[Norcalplanner]

This is the account of the first trip to all of Jool's moons for the newly renamed Kerbal Administration for Big Overpowered Orbital Machines (KABOOM). Our motto – "Why go small when big will do?" I believe that this mission log will meet all the criteria for the Jool-5 Challenge.

Meet the Jool Explorer:

Breaking up a transfer burn into two orbits is not my cup of tea, so this design is generally marked by being a) too large, and overpowered. But hey, it's in keeping with the KABOOM motto. This is also my first KSP AAR, so any tips on formatting or content are welcome.

Edited July 2, 2014 by Norcalplanner

[Norcalplanner]

CHAPTER 1 - CONSTRUCTION AND LAUNCH

To set the stage properly, here's what's going on behind the scenes -

Running 0.23.5, with Kerbal Alarm Clock, Editor Extensions, MechJeb, Kerbal Engineer Redux, and KW Rocketry installed. Kethane and KAS are also installed, but are not being used in this design. A total of three launches were used – the main ship, and two refueling tankers to top it off while still in LKO. Two other ships were launched to Jool during the same transfer window, but they didn't interact with the Explorer in any way.

And so the tale begins...

The Jool Explorer 4 was launched by the Kerbal Administration for Big Overpowered Orbital Machines (KABOOM) from KSC with Jeb, Desderry and Wilman Kerman on board. Their mission - land on all the moons of Jool and successfully return. The design of their ship is a bit schizophrenic, since it grew over time - the lifter uses seven 3.75m stacks, six 2.5m stacks, and two SRBs. In an alternate reality (er, previous career save) I had great success using allmhuran’s thrust plate concept, lifting over 500 tons to LKO on a regular basis with ARM parts and assembling an 800-ton space station in Mun orbit. In this save, I’ve decided to forgo thrust plates and have started adding nose cones to prepare for the day when I summon enough courage to install FAR.

As you can see in the photos below, the ship has retained the last three stacks of the lifter section. Originally these stacks were to be ejected, and the single 135 ton KW tank with the KR-2L engine was to be the Jool transfer stage. Then I realized that if I hung on to the last three lifter stacks and refueled them while in LKO, I could use them as the transfer stage. These three stacks were modified in this final design to use KS-25x4 engines (for their greater vacuum Isp and TWR) instead of two Titans and a Griffon XX as found in earlier versions of the Explorer. I had hoped to use three KR-2Ls for even better Isp and TWR, but the reduced thrust just made it too difficult to get the whole ship into orbit.

The old transfer stage was refitted with some new bits, and rechristened as the tanker stage. It now has the ability to separate from the rest of the ship and navigate independently as a tanker. It can also remain attached and serve as a transfer stage if needed.

Everyone raves about LV-Ns (including the data - never argue with the data), so I’ve relented and used them on the main Explorer mothership. To get a decent TWR, I’ve installed 8 on the main drive section, and two more on the drop tanks. Not the most efficient, and likely overkill, but no Hyperedit means no advance testing, and I’m going to err on the side of too much rather than not enough. MechJeb says the initial TWR is .4 – I try to stay above .5, so I’m already out of my comfort zone. The design is pretty conventional, with a single 3-person command pod and usual accoutrements. Role-playing real life concerns, the LV-Ns are not to be used in any atmosphere, and if discarded must end up in a location that Kerbals have no long-term interest in - Kerbol, Jool, or deep space.

The lander section features my new favorite engine, the KW Rocketry VR-1 Vesta. This is my first career save with KW installed, so this engine is a new addition to the parts catalog. In the same way that the KR-2 largely made the Mainsail obsolete, this engine has largely replaced the LV-909 in my designs. Compared to the LV-909, the Vesta has 2.4 times the thrust and slightly greater fuel efficiency, for the cost of .1 additional ton in weight and some additional engine height; the height can be dealt with by vertically offset side stacks and/or larger lander legs. It also compares very favorably with the 48-7S - it takes four of those tiny engines to match the thrust of a single VR-1, and they’re not nearly as efficient. Unless it’s a tiny ship or there’s ludicrously low gravity, the Vesta has become my go-to engine for small craft.

The lander has 7 of the Vestas. It hasn’t been tested on Tylo, but it can make it from KSC to LKO without dropping any of the stages. With proper staging on Tylo, I’m pretty sure I’ll be OK. The lander also has a real lander can, not some exterior seat. I only used that trick once (to rescue Jeb from a botched Eve mission) and I felt dirty for doing it. KABOOM executives have decreed that there are to be no external chairs except for Slim Pickens-type photo ops.

There are a few chutes on the lander, but not enough to slow it down to a safe landing speed. I’ll need to do a small retro burn on Laythe right before touchdown.

This one lander will be used to land on all five moons. It should be able to ascend intact from both Laythe and Vall without staging. On Tylo, it will definitely lose 2 stacks, possibly 4 stacks, during the landing and ascent. The reduced size 3-stack lander is ridiculously overpowered for Bop and Pol, and may even be sufficient for Vall should the need arise.

The overall plan is to leave the tanker stage in high orbit, possibly even skipping certain moons (such as Vall) altogether. The main Explorer mothership with the LV-Ns will double as a tug to put the lander into a lower orbit prior to final descent, at least for Laythe, Vall, and Tylo. Again, not the most efficient, but it should work.

Here's the first photo gallery showing the Explorer and the tankers used to fill her up in LKO. There are also some pictures of two other ships which went to Jool during the same launch window. We'll see closeup shots of each section of the ship later in the mission report.

Javascript is disabled. View full album

Edited July 2, 2014 by Norcalplanner

[Kamuchi]

Use: [ imgur ]HtAu8[/ imgur] (remove the space between [ and imgur ])

The tags will parse the album into that neat slider

MechJeb is great, but it has some awkward moments that you need to kick it and take control lol

[Norcalplanner]

Thanks! I think I've got it working now.

[Norcalplanner]

CHAPTER 2 - DEPARTURE, ARRIVAL, AND LANDING AT LAYTHE

I'm putting more of the narrative in the captions for the photos, so feel free to jump to them straight away if you want.

Final count is 257 parts and 860 tons for the Explorer. When the transfer window arrives, the three ships launch, with the Explorer leading the way. The other ships wait a bit so that all the ships don't arrive at the same time at the other end. The main transfer burn to Jool only takes 3 minutes.

The tanker / station is second to depart. The plan is to park it around Laythe initially, but it may transfer to Tylo if the tanker stage on the Explorer doesn’t have enough to fill up the mothership and the lander after the Tylo ascent. Long term, it will stay around either Laythe (for colonization prospects) or Vall, Bop, or Pol for future kethane mining opportunities if and when a kethane-harvesting ship finds its way to Jool. Tylo is out of the running for any future colonization or kethane mining – I plan to ignore it as much as possible after planting a flag on it.

The fleet delivery ship is last to depart. All the small ships will stay latched to their mothership for the duration of the Jool-5 mission. No kethane will flow until after Jeb and friends have departed back for Kerbin.

I'm coming to realize that MechJeb was very efficient with the transfer maneuver, plopping the Explorer in front of an onrushing Jool with hardly any velocity to speak of. Even though the Explorer is heading straight for Laythe and bypassing Jool proper, it's still coming in really hot - over 6,000 m/s. I check an online calculator, which says 18 km for aerobrake. 18 km? That can't be right – nudge it up to 20.

18 was correct. 20 km aerobrake results in needing a 1,200 m/s burn after the aerobrake is over. Being the wimp that I am, I hit F9, reload, and do it again going down to 18 km.

Much better the second time. I've only been to Jool once previously, and I burned a lot more fuel to get there with manually adjusted maneuver nodes. Arriving with fuel to spare is a new and pleasant experience.

The tanker stage detaches from the rest of the Explorer. The Explorer mothership brings the lander into a lower orbit, and Desberry puts the lander through her paces on the way down to the shores of Laythe. Well, he tried for the shore, but ended up being a few kilometers away. The ascent and redock to the Explorer was uneventful, and they still have so much fuel that the tanker stage bypasses Vall and heads straight to Tylo.

Here's the visual record of that portion of the journey:

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[Norcalplanner]

CHAPTER 3 - VALL AND TYLO

More and more of the narrative seems to be finding its way into the descriptions for the photos, so feel free to jump straight to them.

The Explorer departs Laythe and arrives at Vall, and Wilman jumps into the lander. He fills up the fuel tanks in the lander and undocks. However, in his enthusiasm, he forgot to fill up the RCS tanks. He sheepishly redocks, grabs some monoprop, and then departs again. Landing on Vall is uneventful, except that Wilman goes for a moderately high altitude EVA with his RCS pack, foreshadowing events on Pol and Bop. The lander comes back up and redocks, but doesn't take on any fuel to reduce the amount of mass flopping around at the front of the Explorer.

The Explorer transfers to Tylo, and docks with the tanker stage up in a 1,000 km orbit. Only a partial load of fuel is transferred, since the plan is to come back to the tanker stage again after the Tylo ascent.

With Jeb in the lander, the hardest landing on the mission goes off without a hitch. There's enough extra delta V on tap that KABOOM mission control directs him to hang on to two of the empty side tanks, since the landing platform is a bit more stable with the two extra landing struts.

The lander meets up with the Explorer mothership, which then goes back up to 1,000 km to redock with the tanker section. All the tanks are filled up in the lander and the mothership, but there's still fuel left over in the tanker stage... because Jeb forgot to hang on to the side tanks and ejected them back at Vall. Whoops. The tanker stage, with the remaining fuel left on board, remains in orbit around Tylo to act as a fuel depot for any future visits.

Here's the visual record of that portion of the journey:

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[Norcalplanner]

CHAPTER 4 - POL AND BOP

The Explorer arrives at Pol. Bop is temporarily bypassed so that the big orbital inclination change with its hefty delta V pricetag only has to be done once.

Desberry hops in the lander, trusting on MechJeb to make the landing. All lander engines are shut off except for the center one, which is thrust limited to 25%. As the lander comes in on final approach MechJeb takes a hint from the other MJ (Yow! Sha-mon! [grabs crotch and spins]) and puts on an unbidden aerial display, somersaulting out of control while still partially throttled up. Desberry spits out his Tang, quickly disconnects the landing computer, and finishes the landing manually.

Alas, Desberry was not to be long for this world. While on high altitude EVA, the system glitched and he disappeared forever. The F9 key was reluctantly pressed, and a resurrected Desberry conducted a manual landing. He quickly grabbed a surface sample, planted a flag, took some readings, then shook the Pol dust from his boots and departed that accursed place.

Wilman jumps into the lander for the last descent down to Bop, after Jeb transfers orbits. Something that looks like an anomaly is seem from space, and Wilman is sent down to investigate. He makes it down safely, but the anomaly is actually a graphical glitch at Bop's north pole. While Wilman is checking it out on EVA, the system glitches again, and he turns into an unresponsive rag doll. The F9 is pushed again, Wilman is resurrected next to the lander, and any thought of investigating anomalies is promptly squashed. Similar to Desberry, he finished his task and then blasted off from that horrible place.

It's time to go home.

Here's the visual record and color commentary from that portion of the journey:

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[Norcalplanner]

CHAPTER 5 - THE JOURNEY HOME, AND THE FATE OF THE OTHER SHIPS

All the comments for this final chapter are embedded with the photos. I'll post one more wrap-up soon with observations, a critique of the ship design, and future plans for KABOOM. Enjoy.

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[Norcalplanner]

CHAPTER 6 - POST MISSION EVALUATION, OBSERVATIONS, AND CRITIQUE

I. Thoughts about the Jool-5 Challenge:

I liked it. It’s ambitious, but not overly so, and I think that most players who’ve made it successfully to another planet and back should eventually be able to complete it. It gives people an incentive to explore more of the Kerbol sytem. Thanks go to Ziv for coming up with the idea in the first place, and for creating the nifty graphic for putting in people’s signature lines.

II. Observations about the KSP program and mods:

1. MechJeb is five parts helpful, one part infuriating. While it was great at maneuver planning and performed very well on Laythe, Vall, and Tylo, it screwed up (or tried to screw up) landings on Pol, Bop, and Kerbin.

2. KW Rocketry is great. The tanks and engines are just a little better than stock, which gives designs using KW parts a bit of an edge without seeming horribly overpowered. This trip reinforced my admiration for the Vesta engine, which performed very well. Its high TWR, low weight, and Isp of 400 is one of the primary reasons my lander had so much delta V.

3. Poles and/or high altitude EVAs can be glitchy. I’m still not sure what happened on Pol, but I’m pretty sure the "anomaly" I was investigating on Bop was a graphic glitch at the north pole where the textures come together. I’ll be staying at least 10 degrees away from all poles in the future, and will limit EVAs to more reasonable altitudes.

4. Even though LV-Ns are the most fuel-efficient thing around, the KR-2L on the tanker stage is still a heck of an engine. Vacuum Isp of 380 and 2500kN of thrust in a single 6.5 ton part is hard to beat, especially if part count is a concern. I figure I can get the tanker stage down to about 15 to 17 parts, as long as it retains the KR-2L. If I switch to LV-Ns, the part count for that stage will jump up to at least 40.

5. Detailed textures on parts are great. I’d like to offer a big thank you to those part designers who include rivets, paint, and other visual cues on their rocket parts. Having these cues and reference points in the VAB makes rocket assembly easier and more accurate. This is especially important when it comes to attaching struts, which can induce wobble or rotation if not placed evenly.

6. Orbital height really matters. As I noted in one of the photos, the delta V for orbital capture around a moon without an atmosphere is greatly reduced if the orbit is higher up. The tanker stage saved a lot of fuel by parking in a 1,000 km orbit around Tylo instead of a 100 km orbit as originally planned.

II. Critique of the ship design:

1. The Explorer’s design had a lot of fat. Without radically changing the design, I think I can cut out about 5 or 6 tons from the lander, and 6 to 8 tons from the Explorer mothership. Part of these changes involving going from 8 LV-Ns on the mothership down to either 6 or 4, and removing two Vestas and shortening the side stacks a bit on the lander. The lander in particular was overpowered, being able to hang on to the two extra empty side stacks while ascending from Tylo.

2. Refueling those three monster lifter stacks while in orbit around Kerbin was overkill. [but it sure looked cool. - Ed.] With a lighter lander, mothership, and tanker stage, and a slightly modified lifter, I think that a revised Explorer should be able to make orbit with a single mostly full center lifter stack. That single stack can then handle the majority of the interplanetary transfer duties without any refueling.

3. I should convert the tanker stage to use LV-Ns, probably eight of them. If I do, I’ll likely need some supplemental regular engines to complete the initial transfer burn to Jool in a single orbit, which is a non-negotiable mission requirement as far as I’m concerned. Initial thought is to put on 2.5 m side drop tanks tanks with Vestas or some other efficient engine attached, then drop those engines once the initial burn to Jool is complete and/or the side tanks are empty.

4. The side drop tanks on the Explorer mothership were too big, and need to be either reduced in size or eliminated. With conversion of the tanker stage to LV-Ns, it makes more sense to have the fuel stay in that stage as long as possible for more efficient transport.

5. I brought along way too much monopropellant. At the end of the trip, both the tanker stage in orbit around Tylo and the Explorer mothership back at Kerbin had over 2/3 of their monoprop left. Although the part count will increase slightly, I should put in a few of the .75 ton cylindrical tanks and ditch the 3.4 ton inline tank in the Explorer. The lander should switch from the .55 ton inline tank to one or two of the small spherical tanks. Only the tanker stage will retain the big inline tank with 750 units of RCS fuel.

6. If I want to reuse ships, I need to use more docking ports instead of decouplers. The Explorer’s main drive section is still perfectly useable, but there’s no way to re-attach a command capsule to a decoupler that I’m aware of. I haven’t used KAS all that much yet - if it’s possible for Kerbals on EVA to remove the decoupler from the drive section and put on a 2.5m docking port instead, the ship may yet come back to life. Otherwise, it will lie dead in its parking orbit for the foreseeable future.

7. I need to put one or two more reaction wheels on the tanker stage, and/or use the RCS thrusters more. Watching the ship slowly turn was majestic in a Stanley Kubrick sort of way, but it added a lot of unnecessary real-life time to the journey.

8. I’ve decided that any future journeys of more than a month’s duration must carry along at least one Hitchhiker container for additional living space. I think even the stoutest Kerbal would go a little stir crazy after being cooped up in a 3-person command pod for more than a year.

9. Science was lacking on the lander. No material bays or goo canisters made it down to the surface of any of the moons; only massless detection gear was attached to the lander. If I do something like this again, I’ll try to make some modular science packages docked radially around the mothership that can be pulled off by the lander, taken down to each moon in turn, and then re-attached to the mothership.

III. Evaluation of myself:

1. I used MechJeb too much. This is my first career save with MechJeb installed, and I leaned on it too heavily. It took some of the fun out, and I spent more time than I anticipated just watching the screen as MJ did its thing. For future landings, I might let it go so far as to do the initial de-orbit burn, but then I’ll turn it off and take the lander in manually. For docking, I’ll probably let MJ get the initial orientation correct with the lander perpendicular to the target docking port (which I’m not great at), then do the approach and translation myself.

2. I’m developing a grudging respect for LV-Ns, and will use them more in the future, but I still don’t like them. They’re heavy, awkward, and weak. Ships using them tend to have much higher part counts, which increases lag. Transfer burns can take a really long time, and may need to broken up into multiple orbits (which I hate). And I don’t like the engine sound, which is coarser and raspier to my ear. (I also dislike the sound of the 48-7S, but that’s a different topic.) All of those negatives are offset (barely) by their phenomenal Isp of 800. I also feel like I have to impose some real-life limitations on their future use that many other players do - no atmospheric operation, no staging where they drop into an inhabited atmosphere, etc. I’m thinking that once I get KAS figured out I’m going to go back to Vall to retrieve the two drop tanks in orbit, which each have an LV-N attached, and de-orbit them into the crushing depths of Jool’s gravity well.

3. I need to trust the aerobrake calculator more. Twice I added a bit of additional height as a safety margin for aerobrake maneuvers, and both ended up not being orbital captures. If I add a "safety margin" for aerobraking in the future, it’s going to be only a few hundred meters of periapsis height.

4. I need to be smarter about fuel use. The lander headed down to both Laythe and Vall with full tanks, and ended up burning more fuel just to bring the unused fuel up into orbit again.

5. Shifting around fuel manually is only interesting the first few times you do it. After that, it becomes a chore. I need to try out TAC or some other fuel management mod.

6. I’ve concluded that I cannot keep track of multiple ships in hyperbolic orbits while performing planetary operations. If I ever launch multiple ships again during a single transfer window, I’m going to wait until all ships are in stable orbits at the target location before doing anything. Starting the Explorer’s mission with trips down to the surface and plotting transfers to other moons while the other two ships were still inbound ended up being a bit of a disaster.

7. Kerbal Alarm Clock is great, so long as I remember to use it EVERY TIME. Forgetting to activate it a few times led to undesired results, especially with the two follow-on ships.

8. The roleplaying aspects just sort of manifested themselves as I was writing captions for the photo albums. The Kerbals started to develop distinct personalities, especially Wilman. This turned into an unexpected outlet for creativity, and ended up being fun.

9. I liked my over-the-top acronym for the space organization launching the rocket (KABOOM), and I may use more acronyms on future reports and/or career saves. Next on the list is the National Association for Development of Impressive Rockets, or NADIR.

10. I spent too much time flying this mission and writing up the mission report over the last week. It’s time to put the game down for a while and spend more time with the family. When I do pick it up again, if I try another big challenge (such as the kethane variant of this challenge) it will be stretched over a much longer real-life timeframe.

If you've made it this far, thanks for reading! I've had a lot of fun with the writeup and the photo albums. Enjoy!

Edited July 3, 2014 by Norcalplanner

[bobcook]

Thanks for a really detailed writeup and evaluation, this should make for good reading for anyone else planning the Jool-5 Challenge.

I understand what you are saying about LV-N engines but honestly nothing in the stock inventory comes close to their efficiency for deep space operations. For interplanetary travel I usually use the LV-N engines from high Kerbin orbit, exiting the Kerbin SOI in advance of the transfer window. Then, when my ship is in the same orbit (more or less) as Kerbin itself I can then plan the final transfer burn many days in the future, as required. This maneuver makes it irrelevant for the time or angle of departure from Kerbin SOI, meaning you don't necessarily need to burn in multiple orbits (just burn until you exit). Yeah this isn't as optimal as it might be, but easier and simpler. Just don't get recaptured by Kerbin's SOI.

I've also been thinking of re-doing the challenge but this time following the Kethane Expedition variant. The scoring system heavily penalizes huge ships so I've been prototyping a single lander design and much smaller "main ship" (really its just the interplanetary booster and spare fuel tank). The penalty for using LV-N engines is pretty harsh but I think I'm going to have to use them. There are so many different ways to achieve points, I've been putting way more effort into planning than I did for the original challenge. Should be fun!

[Norcalplanner]

Thanks for a really detailed writeup and evaluation, this should make for good reading for anyone else planning the Jool-5 Challenge.

I understand what you are saying about LV-N engines but honestly nothing in the stock inventory comes close to their efficiency for deep space operations. For interplanetary travel I usually use the LV-N engines from high Kerbin orbit, exiting the Kerbin SOI in advance of the transfer window. Then, when my ship is in the same orbit (more or less) as Kerbin itself I can then plan the final transfer burn many days in the future, as required. This maneuver makes it irrelevant for the time or angle of departure from Kerbin SOI, meaning you don't necessarily need to burn in multiple orbits (just burn until you exit). Yeah this isn't as optimal as it might be, but easier and simpler. Just don't get recaptured by Kerbin's SOI.

I've also been thinking of re-doing the challenge but this time following the Kethane Expedition variant. The scoring system heavily penalizes huge ships so I've been prototyping a single lander design and much smaller "main ship" (really its just the interplanetary booster and spare fuel tank). The penalty for using LV-N engines is pretty harsh but I think I'm going to have to use them. There are so many different ways to achieve points, I've been putting way more effort into planning than I did for the original challenge. Should be fun!

Bobcook,

Thanks for the kind words. I did exactly what you described in terms of leaving the SOI of the planet when it was time to leave Jool and come back to Kerbin, but somehow I never thought of doing it on the outbound leg.

I think I'll also give the Kethane variant a try. Not sure about the surface hoppers, and it may be a month or so before I finish it (which may mean that it gets done in 0.24) but it's in the queue of future activities at this point.

Norcalplanner