Aegolius13

I agree with that - I've never really looked at delta-v for jet engines. Total burn time is usually more useful. So delta-v on a spaceplane only becomes useful once I switch to rocket engines, at which point vacuum numbers apply. But it would be cool to have separate default settings available for each building.

One other thing to try - turn on "enable crossfeed" on all docking ports, decouplers, etc. There is also a setting somewhere in the difficulty options about allowing crossfeed along all part types. It could be the fuel coming out of your ISRU cannot feed to any of the tanks on your recipient craft.

Do you by chance have any fuel cells on any of the ships? They could be consuming fuel and converting to electric charge. Other than that, I can't think of any reason fuel would be disappearing without engines running. A bug seems very possible. You could run some quick tests by building another miner/refining rig (could do in a Sandbox game if you don't want to spend funds). If your settings are not on hard you can probably even mine the launchpad for ore.

I find it's hard to hit the predicted delta-v figures when going to Moho. Little deviations from the optimal transfer (including that wicked plane change) can make for very large increases in requirements. I think once I thought I had a pretty good transfer going, then got hit with a 5 or 7km/s burn required to capture. (That mission turned into a flyby.). With that in mind, I think that to maximize prospects of mission success, I'd go direct. Even if there is some minor difference in optimal delta-v budgets (and your numbers suggest there may not be), gravity assists add a lot more potential for things to go wrong. You also may want to look into the alternate method for direct transfers, where you launch at Kerbin's ascending or descending node w/r/t Moho, rather than at a certain phase angle. I find it cheaper and more accurate.

Does anyone know if there's a setting to make the delta-v readout in the VAB / SPH default to vacuum rather than atmospheric? I try to build rockets from the top down and thus nearly always want to see vacuum stats first.

Yep, that worked. My Kerbals thank you for the slightly safer VAB working conditions.

I noticed a couple new bugs with the NERV when building in the VAB (version 1.6). First, when I select the engine from the menu, it the model shows the exhaust plume (both before and after attaching it to a node). Second, even when I have ample liquid fuel, the stock delta-v readout shows zero. But once I launch, it looks like the readout works fine. Has anyone else run across this problem? If it matters, this is on a no-mod install with Making History. (This install used to have mods, but I deleted them all and re-verified local files through Steam).

I agree with @5thHorseman - I find it's not really worth using. You may or may not find that funds are tight, depending on the difficulty and how cost-efficient you build. But if you're flush with cash, converting to science is not a bad idea, since you always need more until you're maxed out. Very generally, I find the most effective techs to invest in are (1) new engines, and (2) more science equipment. The former let you reach some new science bonanzas (like orbiting or landing on the Mun or Minmus), and the latter increase the payoff for each such mission. But you may also need to grab a couple support parts as well, like fuel tanks, decouplers and electrics. I agree that plane parts don't offer a great return on your time. I usually leave these techs alone at first, and then backfill later.

I think I said this before in one of the "Wolfhound / Skiff Switched" threads, but there's just no way to be completely faithful to the historical stats, and still balanced for gameplay. As you say, the Apollo SPS engine was relatively low ISP due to hypergolic fuel and so forth, but thay was based on the need to store fuel in space and easily restart. The J-2 had much better efficiency, but that came with all the disadvantages of hydrogen (low fuel density, poor storage) etc. But since stock KSP does has only one kind of LFO and does not simulate fuel boil-off or part failures, none of those real-world distinctions would come through in the game. A faithful analog of a pressure-fed hypergolic engine would just be terrible compared to stuff like the Skiff, because the game models its disadvantages but not its advantages. (Kind of the same reason the Puff is virtually useless). To make make an engine worth using in an Apollo SPS-type role, they needed to to give it good stats for that mission, within the constraints of the game. Which basically means a good vacuum ISP. However, I am with you that the Wolfhound does have more mass and thrust than makes sense. The Cheetah probably fits better as an SPS analog if you're planning to use a Terrier / Spark lander. Maybe they amped up the Wolfhound because the small vacuum engine design space was getting too crowded, but it does seem like a head-scratcher.

So, as everybody probably knows, Squad reskinned the Spark, Terrier and Poodle engines in 1.6. This seems to be part of an overall trend of making parts look more realistic, including larger engine bells for the vacuum engines (requiring the Poodle to be split into two bells). My question /speculation is -- are these new engine skins supposed to resemble particular real-life engines, as we've seen with the Vector, RAPIER and all the Making History engines? Or are they just supposed to be generic, but more realistic-looking engines? I can't tell for sure, but a few ideas on possible identities: Poodle -- this could be a dual RL10 cluster, as found in some Centaur upper stages. That's the only real-life example i can think of that uses to smallish engines in this manner. But the thrust seems too high. KSP engines generally have less thrust than their real-life counterparts, but the poodle would have more than a pair of RL10s. Terrier - if the Poodle is not a pair of RL10s, the Terrier could be a single one. It's got about half the thrust of a real-life RL10, which is in line with some other examples, (e.g., Vector vs SSME). There's also some piping on the side of the engine bell that might be expander cycle plumbing. This could also be the Descent Propulsion System from the Apollo Lunar Module. Spark - my best guess for this one is the Lunar' Module's ascent engine. The LEM-like lander can from Making History all but requires you to use a Spark if you want to do a staged ascent. If true, this strongly suggests that the Terrier is the descent engine (an perhaps the reason that neither LEM engine was duplicated for Making History). On a tangent, I would not mind seeing a few more of the original engines re-skinned. For example, since the F-1 is represented by the Mastodon, the Mainsail has no real-life analog. (After all the F-1 was the largest single combustion chamber engine ever flown). The Mainsail design is just also a little blah, in my opinion. It might spice things up for Squad to rejigger it into something like the Russian RD-170 engine, which had four combustion chambers and bells, but more total thrust than the F-1. Similarly, the Rhino is kind of an odd outlier at the moment. It has a few things in common with the J-2X concept for the Ares / SLS, but the J-2 is now represented by the much smaller Skiff. And even more than with the Mainsail, the Rhino also seems too powerful for a single-combustion chamber engine. Perhaps they could also turn this one into a compound engine. One idea would be a Mammoth-like conglomeration of 4-5 Skiff-like engines, somewhat like the Saturn V second stage.

My quick thoughts on the new engines -- kind of a follow-up to my old MH Engine Round-Up linked below: Cub: After nerfs to thrust and vacuum ISP, the Cub is drawing closer to the Spark in performance, but is still generally a better option as long as you need the extra thrust. The main disadvantage continues to be that the Cub only gimbals in one direction, so you really need at least four of them for effective attitude control. I feel like radial engines are only used situationally anyway (e.g., in a lander or a ship that needs the back end free for docking), and for those uses this remains just fine. Frankly, this engine was just too good in vaccum for something that was to be used as a vernier for the Kodiak or Reliant at launch. Cheetah: The Cheetah used to be "two Terriers stapled together," was was generally an afterthought unless you needed something to fit a 1.875m stack. Now, however, its ISP is second only to the Wolfhound in terms of chemical engines, and thrust has received a nice upgrade as well. So the new Cheetah looks like a very attractive option for anything in that gap between Terrier and Poodle/Wolfhound sizes. It does not appear worthwhile to cluster Cheetahs, however -- the Poodle's superior TWR vs a pair of Cheetahs should outweigh the minor gap in ISP. Kodiak: The old Kodiak was practically indistinguishable from the Reliant, which made especially little sense given how far up the tech tree the new engine was found. Now, there is a pretty clear differentiation: the Kodiak is a superior launch engine, with better ISP and thrust than the Reliant for the same cost. The Reliant's only relative advantage is marginally better vacuum ISP, but that's not terribly important for what is still basically a launch engine. In other words, the Reliant, somewhat like its sibling the Swivel, is now a bit of a "tweener" that is unlikely to be your best option for either a launch or a later stage. Skiff: The Skiff is/was another "tweener" engine, suited for a J-2-style sustainer role that makes more sense in real life than in KSP. Prior to the update, this was more than made up for by its absurdly high TWR (tops in the game if I remember correctly). Predictably, the Skiff's mass was brought up in the update to bring TWR closer in light with the other engines. I worry that, between the unimportance of sustainer engines and this model's low thrust relative to its surface area on a rocket stack, it might not see a lot of use. More than ever, I think it's best viewed as an upgrade to the Swivel, and kind of a "jack of all trades, master of none" option. It could still be pretty good as, say, the core stage of a rocket in conjunction with some kind of radial booster. Bobcat: Of all the MH engines, the Bobcat seemed like the one that made the most sense from a design perspective, as it had a clear niche without being imbalanced. Squad seemed to agree, as the changes made in 1.6 were minimal. This remains a great launch engine for anything on a 1.875 meter stack, but works especially for radial boosters. Wolfhound: This seemed to be the most controversial engine (or probably part of any kind) in Making History, due to its absurdly high vacuum-ISP. It not only spawned a million arguments about accidental stat swaps with the Skiff, but it was just way too got. So not surprisingly, we see the ISP brought down to a (still very robust) 380, and a mass hit as well. I think these changes bring the engine in line with what we expected/wanted -- a low TWR, high ISP vacuum workhorse that bridges the gap between the Poodle and NERV. Mastodon: The community seemed to agree that the Mastodon was much too expensive in career mode, and generally upstaged by the more efficient and powerful Mainsail. Squad responded by cutting the cost to a figure that puts it right between the Skipper and Mainsail, and by giving a nice boost to ISP. As a result, the Mastodon now trails only the Vector and Mammoth in terms of launch efficiency. So it's very well-suited as a core launch engine for anything a little too small to make sense for a Mainsail or Twin-Boar. I still feel like the TwinBoar will make a better radial booster engine for most applications, due to its superb thrust and very reasonable cost. Likewise, I'm not convinced that clustering Mastodons, a la the Saturn V, will beat other options like the Mammoth (or just MOAR TWIN-BOAR BOOSTERS). But now it's nice that the game's analog to the legendary F-1 is now at least worth considering. Overall thoughts: I almost did a post on possible tweaks to rebalance these engines, it it came relatively close to what we see here. I think Squad has done a pretty good job of making these engines closer to their real-world analogs in terms of use cases, but having them still make sense in the game and in balance in comparison to the vanilla KSP engine offerings. As noted above, these changes have the potential to relegate some new engines to afterthought status, but in general I think this is a very positive step. My original (and now sadly obsolete) engine review:

It might help to post a screenshot of some of the maneuver nodes leading you from Jool to Kerbin. But the short answer is yeah, you can probably reduce the 6,000 m/s with a different approach. Assuming an optimal Hohmann transfer, it takes around 2,000 m/s to transfer from Kerbin to Jool. The same is true in terms of the excess velocity you'll need to shed to capture around Kerbin off of an optimal Jool transfer -- meaning the lowest possible velocity at perikee is something like 4,200m/s. So the extra ~1,800 your experiencing suggests there is something suboptimal about your approach - either your periapsis around the sun is inside Kerbin's orbit, or (more like) you're not coming in perfectly tangent to Kerbin. [EDIT] Or you're coming in at a high inclination, retrograde, or something other than the optimal equatorial orbit. One other thing to keep in mind - once you've captured around Kerbin, you can aerobrake at your leisure to get back to LKO, or capture and reenter. So you really only need your velocity at perikee to be about 3,200 m/s. If fuel is limited, it's most effectively to use it to help capture, then rely on aerobraking for the rest (but save a tiny bit of fuel to adjust your periapsis during aerobraking).

It might help to have a screenshot of your current craft, and/or more detailed description of what you're trying to do. For example, by going to Duna, do you just mean going to Duna orbit, or actually landing on Duna? The latter is going to impose a lot of more requirements than the former. As @Pluscksays, a Duna mission is not that different in terms of total requirements than a trip to the Mun, but due to the extra steps and time requirements, it['s a lot easier for something to go awry. But in a general sense, if you need your rockets to go farther, I think the best framework to work around is the Tsoilkovsy Rocket Equation. (Not sure if you're familiar with this, or with the concept of delta-v). There's quite a bit of math involved, but in general, the Rocket Equation says a rocket's total delta-v (i.e., effective range) is a function of only three things: the dry mass, the wet mass, and the engine's specific impulse. So, to get more delta-v, you can do a few things (these are very general tips, so they might or might not be applicable to your current issue): Reduce dry mass. This means getting rid of any parts you don't absolutely need, including excess engines. Increase wet mass. This simply means adding more fuel. But of course, adding fuel hurts your TWR and adds dry mass in the form of empty tanks, so it can hit diminishing returns pretty quickly. Increase specific impulse. Assuming you're able to get you ship to orbit, this means picking engines with good vacuum specific impulse. For a Duna mission, NERVs, Poodles, Terriers and Sparks are all decent choices, depending on your craft size. Make your staging more efficient. (Technically outside of the Rocket Equation) This is a bit more of a complicated topic, but generally you probably want each stage to have about the same total delta-v. As a general rule of thumb, if a new stage has 1/4 to 1/3 the thrust of the previous stage, you're probably in the right ballpark. For example, it;'s common to have a Poodle powered stage, followed by a Terrier, followed by a Spark. Or, if all else fails, add MOAR stages, starting at the top/end of the rocket and moving downward. One other thing that will help extend range on a Duna mission - on the way in, use Duna's atmosphere to aerobrake (i.e., slow your ship enough to get into Duna orbit without needing an engine burn). You'll probably have to use a little trial and error to figure out the right periapsis to aim for.

For anything smaller than Duna / Tylo, the dv requirements for a round trip are small enough that there's not much point to staging. Plus once a support infrastructure is set up, it's nice to have fully reusable landers, which of course requiers SSTO. However, if I'm doing a direct ascent style mission, sometimes a break between stages will occur during the "lander" phase of the mission. (E.g., one stage might do the munar insertion and injunction burns, land, take off, and then a second stage might complete the ascent and return to Kerbin).

I gave it a quick try. At least for me, the landing gear worked fine, and kept the plane straight on the runway up to like 140 m/s, which should be more than enough speed. The bigger problem seems to be the difficulty taking off. A couple points here: You've got your center of thrust well above the center of mass, due to the engines being placed high on the craft. I think this is causing your nose to torque down. You may want to try extending the forward landing gear down a bit, so the plane sits nose-up on the runway. This helps it want to point up and lift off. You might be light on wing area for a plane this size. You might also try rotating your wings so that they point up a bit when the plane is level (this is called angle of incidence, and helps generate lift). Your control surfaces are probably too small for a plane this size. But the bigger issue is that they're in the middle of the plane, so they generate next to no leverage for pitch. Mounting at the tail or the front (as a canard) will help. One other point - this is not as directly related to taking off, but abrupt changes in form factor (e.g., Mk 3 to 2.5m and the like) generate tons of drag. Your plane will perform much better if you smooth these out. For example, I would get rid of that 2.5m monoprop tank in the middle, and put it in a spot with the same form factors. (Or get rid of it entirely - you may have enough monoprop from just the cockpit). Similarly, I would stick a Mk 3 to 2.5m converter on the back of your plane, before the coupler for the nukes. EDIT - one additional thought. I think once you tweak some of this stuff, you'll find that you have more engines than you need to take off and get to space. So you may be able to trim down further, which can provide a cleaner design, and so forth in a virtuous cycle. At the extreme end, you can check out posts by @GoSlash27, who is a master of making clean, low-drag planes that work with minimal engine power.

Can you post a screenshot of the existing craft? That would help a lot in terms of figuring out what your specific issue is and how to fix it. This is often due to wheels not being set perfectly (the game is insanely picky on this). Click your wheel with the rotate gizmo, choose "snap" mode and "absolute" rotation ("F" key I think), and make sure they stick straight down and face forward. Best to check all three axes of rotation. Other wheel things to try: Turn steering off on the back wheels. Increase friction on the back wheels, and/or decrease it on the front wheels. Try larger wheels if you have a heavier craft. You may be overloading it. This could also be related to your other problem re: taking off. If the plane has to go too fast on the runway, or has unexpected forces pushing it down in front, etc., strange things can happen. That sounds like... a lot of Rapiers. Rapiers are not great at low speeds, but unless your plane is enormous, sounds like something unexpected is going on here. Difficulty taking off could be caused by, among other things: Insufficient wing area for your weight (add more wings, or lighten the plane). Insufficient pitch authority (add more control surfaces, use bigger control surfaces, and/or put them at the very front or back of the plane for better leverage). Center of mass too far forward relative to center of lift (move wings forward, or adjust design to shift mass backward). Rear landing gear too far backward (slide forward, but watch out for tailstrikes if you go too far). Unbalanced thrust making the plane want to pitch down (adjust engines so the center of thrust aligns with the center of mass). The "RCS Build Aid" mod is great for checking engine torque. Again, a screenshot would do wonders for a diagnosis, preferably in the hanger with the Center of Mass and Center of Lift indicators on.

Agree. I think the existing ion engine is a decent compromise between realism and playability. It's wimpy enough that you typically have to mission-plan around it, but powerful enough that burns can happen in a scale that works for the game. Doesn't it have to scale this way, for balance reasons though? If you had an ion engine with more power, but less electricity required, it would kind of destroy the other engines in terms of balance. Unless you turned the specific impulse way down or something... at which point the revamped ion is starting to resemble the NERV. Put another way, an in-game version of a real-life ion engine is not going to be well-suited for heavy lift, or landing, or those kind of tasks. You might want to check out the Near Future series of mods - they have several types of electric propulsion motors (VASIMR, etc) with enough thrust to work in "normal" gameplay. The power consumption is correspondingly huge, but the mod also offers gigantic solar panels or (more practically) nuclear reactors to deal with that.

To answer your first question - yes, aerobraking is absolutely a worthwhile way to lower your orbit. It will always take a little bit of fuel to to raise your periapsis back out of the atmosphere, but this is usually much, much smaller than the amount it would take to lower your orbit without aerobraking. However, I'm a bit confused about the "accelerate out of the atmosphere" part. You should NOT need to burn engines while in the atmosphere -- that kinda defeats the purpose of aerobraking, which is to bleed off speed. You will need to do that final burn to finish into the target orbit, but that burn always happens in space. Perhaps the issue is that you're dipping too low in the atmosphere, which is bleeding off more speed than you want, which is making you burn to compensate. That 10m heat shield generates orders of magnitude more drag than smaller parts. I would suggest trying the aerobrake up higher in the atmosphere, and seeing where that gets you. There's also nothing wrong with doing the brake over a couple orbits (and that's sometimes necessary to avoid burning up).

Are you sure you had all the engines on, and in the same mode (jet vs rocket) both times? I can't see your stats on the image, but 8 rapiers seems like it shouldbe enough to accelerate a plane that size pretty well.

You could also look at using a gravity assist from Ike to help with the inclination change. I have not tried this at Duna but it works great in the Jool system.

I find that if you do a big braking burn from LKO, you reenter steeply, but the parts so not get all that hot- because you've already lowered your orbital speed, and if you keep your plane pitched up you should not regain much speed. But a shallow descent usually works too. Where are you reentering from when youget this issue? If coming from somewhere higher than LKO, you mat want to bring your apoapsis down first, such as by making a few aerobraking passes.

It's not quite the same thing, but you could always set your opening altitude for pretty high, but wait to activate them via staging until you know where you're going to land. I.e., stage them earlier if you're coming down over mountains and later if coming down over water. You could also do a similar thing by creating an action group to disarm / arm them.

I'm not sure I'd call it a "launch" engine without running it at high throttle from the start, but that's just a question of semantics. I've done similar stuff with engines that are mediocre to poor at sea level, like the Swivel and Rhino. But I still don't see why the Wolfhound would NOT be just as good (or better) as a sustainer or vacuum engine. Yeah, its thrust may be overkill for smaller spacecraft, but that's true of the Poodle, or any engine for that matter. Just a matter of fitting the right size engine for the right ship (or clustering Wolfhounds for the really big stuff).

I would prefer things to go in the other direction -- more (and more balanced) differentiation from the existing engines. I bought MH largely for new gameplay features. It's a little lackluster in that department, but reducing new engines to just re-skins would only exacerbate that problem. I don't have a great idea on exactly what I'd like to see, but I think it would involve giving each engine a clearer niche. E.g., maybe the Kodiak should be more efficient than the Reliant, but more expensive and higher tech--or vice versa. I guess some of the problem is that these engines were probably designed to work with replicas of the historical rockets, rather than to mesh well with the existing engines. Kind of the same "realism vs. gameplay" argument pervading the Skiff v. Wolfhound discussions. And while the old engines could potentially be tweaked without upsetting any replica business, that might not sit well with non-MH players. Gotta disagree with that last bit. The Wolfhound doesn't have the TWR or atmospheric ISP to work well as a launch engine. I think it's a vacuum engine, just optimized for bigger craft than a Poodle.