Leganeski

Part 19: Argo and some large moons TGGT reaches Argo and continues its ever more systematic journey through the Ciro system. I'm beginning to run out of things to say about the mission, so I'll try to include fun facts about the bodies I visit in addition to commentary. I'll also compare the theoretical Δv cost of each leg of the trip (ignoring aerodynamic drag, TWR constraints, inclination, timing inaccuracies, and gravity assists) to how much Δv I actually spent. (Yes, Argo is the smallest body in this chapter. However, it's the only one that technically qualifies as a planet, so it got the chapter title.) (19.1) Argo Theoretical Δv cost (Icarus to Argo): 9307 m/s Actual Δv cost: ~6220 m/s (gravity assists at Niven, Niven, Niven, Gael, Gael, Tellumo, Gauss, and Nero) (19.2) Augustus Theoretical Δv: 2662 m/s Actual Δv: 3708 m/s (inefficient transfer, some aerobraking) (19.3) Catullus Ceti Theoretical Δv: 4723 m/s Actual Δv: 4120 m/s (drag at Augustus, but then two gravity assists at Tellumo) (19.4) Ciro Eta Gael Gauss Geminus Theoretical Δv: 3479 m/s Actual Δv: 2630 m/s (gravity assist at Tellumo) TGGT is now on the surface of Geminus with full tanks. The next target is Hadrian, which provides a temporary return to aerodynamic rather than orbital challenges. Gravity assists so far: 23 (6 performed this chapter) Flags remaining: 31 (4 planted this chapter)

Eeloo's SOI is pretty big; a maneuver of that size could be accomplished over the course of up to four hours. The craft has quite a few ion engines, which look like enough to achieve the necessary 0.9 - 1.0 m/s2 acceleration. Of course, if the burn starts before entering Eeloo's SOI, then there's effectively no time limit.

There seems to be a misunderstanding. The A1 orbit has more energy than the A3 orbit. An important point to remember here is that the gravitational potential energy is always negative, decreasing from zero as the position gets closer to the body from far away. In this case, the A3 orbit is deeper than the A1 orbit in Earth's gravitational well, causing its total energy to be more negative. This means that it is in fact a lower-energy orbit than A1. The straightness of the threshold lines demonstrates the fact that total energy is dependent only on the semi-major axis (the average of periapsis and apoapsis), and not eccentricity.

This is a great explanation! Conversely, on the opposite side of your planetary orbit, you're moving around the sun slower than the planet. This means you've effectively discarded a bunch of energy for free, helping you lower your solar orbit if for example you want to get to Venus or Eve.

Part 18: Thalia and Icarus Now completely unencumbered, TGGT has enough Δv (8840 m/s in total) to get past any problem that might come its way. For example: Icarus is hard to reach safely. However, I can avoid the problem by refueling on Eta, which is relatively close by. Thalia doesn't have any ore, so I can't refuel there. However, I can circumvent the problem by refueling on its moon Eta instead. Icarus orbits very close to Ciro, requiring a huge ejection burn to leave. However, I can mitigate the problem by ejecting only to Eta, and refueling there. Wait... that's not good. I can only refuel on Eta once. Maybe this is more of a problem than I was anticipating. However, the trip from Eta to Icarus costs quite a bit less than 8840 m/s. Maybe I can stick a Thalia landing in the middle. Getting back from Icarus can be accomplished using ... uh ... a lot of gravity assists, probably. (18.1) Eta (18.2) Thalia Due to the nature of Thalia, I end up encountering some of its features that can only really be discovered by actually going there. If you haven't been to Thalia yet and would like to avoid spoilers, you might want to skip this section. (18.3) Icarus (18.4) Leaving Icarus Now that I have a trajectory intersecting Tellumo's orbit, I have successfully made it out of the inner Ciro system. Tellumo is huge, so an assist can take me just about anywhere I want. In fact, that seems to be a problem with the rest of the mission: since I have no planes to worry about, I can go just about anywhere after each refueling stop. I could just go back to Niven with a more reasonable intercept speed, land on it and refuel, and then go to all the rest of the bodies in order. That would just be a bunch of outwards Hohmann transfers, and would get pretty boring. So instead of doing anything sensible like that, I'm going to land on all the remaining bodies in the Ciro system in alphabetical order, starting with Agrippina wait no I already went to Agrippina Argo. That will hopefully require more interesting transfers, and probably many more gravity assists. Gravity assists so far: 17 (9 performed this chapter) Flags remaining: 35 (3 planted this chapter)

This effect also appears in stock, or more generally in any system when ejecting from a relatively large body. For example, burning to Duna from a solar orbit at the same place as Kerbin's orbit requires 920 m/s, while ejecting to Duna from Kerbin requires only 130 m/s more than reaching Kerbin's escape velocity.

This is also true for small enough moons, such as Lili from Galileo's Planet Pack. Lili is on a very tight orbit around a much denser planet which it is tidally locked to, causing it to spin faster than orbital velocity at its equator. However, only the top 1-2 km of the equatorial ridge is actually above the synchronous orbit altitude, so the rock's internal strength can hold everything together. As @tomf said, land near the poles. I've done it successfully on Lili without much difficulty.

Unfortunately, if I understand it correctly, HeatShifter is an important part of GEP, and required for the atmosphere of Toutatis to work properly.

Part 17: Catullus TGGT goes to Catullus, and visits its moon Tarsiss along the way. The last part on the craft meant to be used during the mission, a stack decoupler in the methane plane, finally performs its function for the first (and only) time. (17.1) Back to the Ciro system (Agrippina) (17.2) Tarsiss (17.3) Catullus descent (17.4) Catullus ascent Ending with a satisfying crash into the surface of Catullus, TGGT's preliminary mission of carrying specialized rockets and planes across the system is finally complete. Now in low Catullus orbit with all three crewmembers, some ore, and full fuel tanks, it can start its true mission: landing on every single remaining solid planet and moon!

I encountered the same problem, which I ended up fixing by manually overriding the first DIV/0 cell in column D (temperature gradient) to an arbitrary value (even zero seems to work), waiting for the rest of the values to update and get rid of the errors, then undoing the change so that the original formula in that cell is restored.

At 2.5x scale, the orbital Δv requirements are multiplied by √2.5 ≈ 1.5811, or perhaps slightly more because low orbits are closer to the bodies compared to their radius. The ascent/descent Δv requirements are a complex combination of the surface gravity, orbital velocity, rotational velocity, TWR, and (if there's an atmosphere) the atmospheric characteristics and even the ballistic coefficient of your rocket, so they generally need to be determined experimentally. They're usually somewhat less than √2.5 times the value at 1x scale, especially if there's a thick atmosphere.

I don't know enough about VAB mechanics to be confident in my explanation, but my guess is that the priorities of the outer tanks were set when the tanks were first placed on the decouplers, and then never changed after the fuel lines were added, so the central tanks retained the highest priority. If it is in fact an issue with tank priority, you can fix it in the VAB by manually changing the priorities to what you want. Edit: I hadn't considered the effect of crossfeed on the decouplers. @jimmymcgoochie's answer is probably right. Also, I don't think you need the fuel lines from the converters to the center tanks. From the KSP wiki: This certainly seems true from what I've seen: my current ship has just one converter and no fuel lines at all, and it routinely refuels across both decouplers and docking ports with no issue.

Part 16: Kerbin TGGT returns to Kerbin and drops off the oxygen plane. Yes, I remembered to go to Laythe first. (The landings on Laythe and Kerbin were so similar that I combined them into one chapter.) No, this isn't the end of the mission. I went to Kerbin because it's a planet too! I need to land on it and return to orbit just like on all the other bodies. (16.1) Laythe descent (16.2) Laythe to Ike (16.3) Kerbin (16.4) A perfectly ordinary SSTO The oxygen plane has now completed its mission, bringing astronauts to the surface of Kerbin, Laythe, Gael, and Nodens, and back to TGGT. It has been recovered safely on Kerbin. It was a bit hard to steer but very effective at doing everything else, and I would totally use a similar design again. TGGT has not completed its mission, and is currently in low Kerbin orbit with all three crewmembers, the methane plane, and a lot of fuel. Now that the oxygen plane is gone, it is 23 tons lighter, and can go farther between each refueling stop, with a total Δv budget of more than 8500 m/s. (The exact amount depends on the fuel level and availability of the fuel tanks in the methane plane, which both vary over time.)

Part 15: Huygen As you may have guessed from the chapter title, TGGT goes to Huygen. If you're familiar with the JNSQ system, this may be somewhat different from the Huygen you're used to, as it has been scaled down to match the scale of the GPP and GEP systems. This particular part of the mission could have been easily accomplished at JNSQ's default 2.5x scale (Huygen is still not very big there), but the Eve and Nara planes would not have been able to get back to orbit. (15.1) Descent (15.2) Ascent (15.3) Aden TGGT has made it back to its home stellar system, and is now in orbit around Aden. Next time, I'm going to Laythe for real.

Part 14: Cernunnos Wait, what? Why does Cernunnos get its own chapter? Cernunnos is arguably a planet, and I'm trying to have each part title be a new planet I went to during that part. It might be a dwarf planet (and most of the other dwarf planets* will likely not get a separate chapter), but it ended up being more interesting than a routine refueling stop. *In particular, Dres, Hamek, Celes, and Argo. I'm counting Celes and Argo as binary planets, which makes them dwarf planets since they're nowhere near big enough to be major planets. (14.0) Mod update I added some more mods. As always, they don't affect the mission. This time, they do affect the gameplay, and one changes the behavior of physics warp slightly. However, none of the changes provide an advantage beyond making things faster for me. (14.1) Cernunnos (14.2) Rosmerta This concludes my grand tour of the Grannus Expansion Pack! The system was really fun to explore, and the bodies looked amazing both from space and from up close. Not only that, but I did not encounter a single bug anywhere in the system. None of my planes crashed due to bouncy terrain (unlike on Eve), and the drill always worked when it should (unlike on Prax). The system was incredibly realistic and yet still provided a very interesting challenge. Thank you, @OhioBob, for making such a wonderful mod! The mission is not over, though. I still have 45 (if I counted correctly) more bodies to land on across two star systems. My next goal is to go to Laythe and Kerbin so that I can leave the heavy oxygen plane behind.

I just did the math to try to confirm this, and got a complicated expression that I can't simplify by hand. I graphed it with Desmos, and found that this is indeed the optimal relative speed (when SOI issues are ignored). The resulting trajectory around the assisting body has an eccentricity of 2 and a deflection angle of 60 degrees.

Part 13: Sirona (well, its moons) Sirona is a gas giant, so no landing is performed there. However, TGGT does get some great pictures of it while exploring the rest of the planetary system. (13.1) Belisama (13.2) Airmed (13.3) Damona (13.4) Damona, done correctly this time TGGT is now in low Damona orbit with plenty of fuel left. The initial stage of its mission is finally complete: it now has all of its reusable components (two planes and three crewmembers), and nothing else. (There is a single decoupler above the ore converter, but it is only for a hypothetical emergency situation and is not meant to ever be used.) I could leave the Grannus system now, but there are only two bodies remaining (Rosmerta, which I specifically set aside as an exit point for the system, and Cernunnos), so why not go to them first?

I haven't tested it directly, but this has certainly been my experience when exploring GEP (particularly the inner planets, which orbit their star really fast, leading to the same problem when trying to use them for gravity assists). To make sure I wasn't just imagining it, I ran the numbers for Mun, and found that when coming to Mun from LKO via a direct Hohmann transfer (that is, an intercept speed of 365 m/s), an assist can change the craft's velocity by more than 500 m/s. It's not in the optimal direction, but it is still enough to get to Minmus. In contrast, for an intercept speed of 3000 m/s (for instance, when coming from Jool), the change in velocity is only 200 m/s. (If this assist is performed on the way to or from LKO, it's not in the optimal direction either, which might explain why you're only saving 100 m/s.) Of course, as @Terwin pointed out, if your relative velocity is too slow, you can't get as much out of the gravity assist either. It seems that the intercept speed (at SOI entry) that maximizes the total change in velocity is equal to the orbital speed at the periapsis altitude, resulting in a change in velocity equal to that amount. (For Mun, that's about 560 m/s.) I have no idea why it works out so nicely, but it appears to get more and more accurate the larger the SOI is.

I think that what's going on here is that if your trajectory around Jupiter meets Ganymede at periapsis, the assist can change your velocity vector (relative to Jupiter) by 900 m/s, but almost all of the change is perpendicular to the velocity. This is perfect for a plane change, but it doesn't change your speed by very much, so it's not very helpful for a gravity capture. If you intercept Ganymede away from periapsis, then the change in velocity can be aligned with the initial velocity vector. However, the intercept speed (relative to Ganymede) is much faster, making the total change in velocity much smaller (i.e. the assist is less effective because the craft spends less time in Ganymede's gravity well). This problem is particularly relevant for the moons of Jupiter because they orbit so fast. For example, Ganymede's escape velocity (~2730 m/s) is quite small compared to its orbital speed around Jupiter (~10880 m/s). In contrast, Titan has a comparable escape velocity (~2370 m/s) but orbits Saturn much less quickly (~5570 m/s), meaning that overly fast intercept speeds are not as much of a problem there. In summary: the variability in gravity assist effectiveness between moons of similar sizes is likely caused by their different orbital speeds around their planets, with very fast-moving moons not being as effective because intercepts with them are faster and therefore don't spend as long near the moon. (If I'm right, this should also appear in OPM, although at a much less important location: Eeloo is about the same size as Mun but orbits almost four times faster, which means that it should be less effective for gravity assists going to or coming from interplanetary space.)

Part 12: Nodens TGGT goes to Nodens and finds that it's actually a pretty nice place. The oxygen plane successfully performs its most difficult task: landing there and returning to orbit. (12.1) Capturing at Nodens (12.2) The surface (12.3) Ascent TGGT and the oxygen plane are now docked in low Nodens orbit and will head to Belisama to refuel.

Part 11: Toutatis TGGT swings by Nodens in order to go to Toutatis. Due to a miscalculation, Valentina comes with Bill but ends up waiting in orbit with the oxygen plane. (11.0) Lighting update (11.1) Reaching Toutatis (11.2) Landing TGGT (11.3) Ascent and rendezvous TGGT and the oxygen plane are now docked in low Toutatis orbit, ready to go back to Nodens. Jebediah is still waiting in the methane plane in Brovo orbit.

Part 10: Sucellus (also featuring: Nodens) TGGT presses on inwards towards Grannus. (10.1) Sucellus (10.2) Caireen (10.3) Leaving for Nodens (10.4) Meanwhile on Brovo... TGGT is now orbiting Grannus and is ready to reach Nodens. Jebediah's vacation on Brovo is over, and he has returned with the methane plane to low Brovo orbit.

I have personally found that Grannus Expansion Pack and Explodium Breathing Engines both work really well with JNSQ, and fit right into JNSQ's theme of preserving realism without disrupting the gameplay. (If you use both, they won't interfere with each other, but they won't interact either. However, adding support between them isn't particularly difficult.)

Part 9: Brovo Jebediah rejoins TGGT at Brovo, where the atmospheric capabilities of all the remaining modules are tested. (9.0) Note on illumination The journeys of the Taranis transfer vehicle and TGGT to Brovo overlap significantly in time, so for clarity, they are described separately here rather than in chronological order. (9.1) TGGT to Brovo (9.2) Return from Taranis, the finale (9.3) Landing the planes (9.4) Landing TGGT (9.5) Rejoining the oxygen plane Valentina and Bill are on TGGT in low Brovo orbit, ready to continue further into the Grannus system. Jebediah has decided to take an extended vacation on Brovo, and will remain there until TGGT comes back to Sirona.

Hello! I think I might have found a very minor cosmetic bug in JNSQ_Rescale_1X: the distances in Sun's IntensityCurves are 10 times larger than what they would be if scaled from the default values. This causes Sun to provide illumination up to 36.864 Tm away; in particular, it illuminates all of the Ciro and Grannus systems when using GPP_Secondary (and Scatterer, although I don't know if that's relevant). The result certainly looks interesting, but I don't think it's the intended behavior. As an example, here's a picture of (my craft and) Brovo (from GEP) at night when Sun is overhead: (For context, Brovo is normally orange.)