Temstar

Let's not forget, there are plenty of landers out there that are not use once and throw away. Even with worlds as big as Duna it's simple enough to build single stage to orbit landers that can do a round trip down to the surface and then back up to orbit all in one stage. These landers are reusable and are usually left in orbit for the next mission to come along to refuel and go again. For such craft that are fuelled over and over again high Isp is a big advantage since it reduces fuel usage each time. The total saving spread out over multiple missions will soon exceed the extra engine weight. Obviously for the big reusable landers you want to use LV-N even if it involves some engineering in working around it's unusual form factor. But for smaller landers LV-909's 40s Isp advantage will still outperform 48-7S once the vehicle dry mass + refuel weight is added together over a few trips.

That's the general idea, but no it's like this: For an uranium bomb the isotope you need is U-235. Natural uranium is 0.7% U-235 with most of the rest U-238. To make a bomb you need weapons grade uranium which means around 90% concentrated U-235. To separate U-235 from U-238 is extremely difficult because they are the same element and so have the same chemical properties. You cannot use standard chemistry methods to separate isotopes, hence the use of a huge numbers of centrifuges to spin the two isotopes apart. For plutonium bomb you need Pu-239. When you breed plutonium in a reactor you create both Pu-239 and Pu-240 together. You cannot separate Pu-239 from Pu-240 with any method!, at least not with any practical method. However you can control the Pu-239 to Pu-240 ratio by controlling how long your fuel remains in the reactor. Once you're done the breeding you remove the nuclear fuel, use normal chemical methods to get rid of any other elements and the Pu that you get is what you have to work with. The higher the Pu-240 the more likely your bomb will fizzle instead of go boom. You don't need neutron source for either type of bombs, the fuel itself is radioactive so is always decaying slowing and producing neutron. That's your built in neutron source. The U-235 bomb (Little Boy) wasn't tested because it contained the entire world's supply of U-235 at time time in its core! There was literally no more U-235 around for the time being anywhere in the world to build another test bomb. However since that U-235 is enriched to weapons grade the scientist know that it won't fizzle. The U-235 is pure enough that you simple shoot a smaller piece of U-235 into a bigger piece with a hole in the middle with what basically is a small cannon inside the bomb and it will go off nuclear. With the plutonium bomb, because the reactor breed plutonium is contaminated with Pu-240 if you use the same simple design the plutonium will blow itself apart in a fizzle as soon as the little piece get near the big piece without there being time for the pieces complete the assembly. Initially the plan to deal with this is to use a longer cannon to shoot the plutonium piece so it flies into the target faster (the "Tall Man" design). But even this method wouldn't be able to complete assemble of the core fast enough to prevent a fizzle. So the final plan is what's called the "Fat Man" design. Basically you have a ball of plutonium with a hollow centre. You then completely surround this ball with a shell of high explosive. When you want the bomb to go off you set off all the high explosives at the same time and the shockwave compresses the plutonium ball so that the hollow centre collapses and the plutonium is squeezed into a much smaller solid sphere. This sphere will then be above critical and go off. This method of assembling a core is much more efficient (and safer) than the gun method of Little Boy since a sphere is the ideal shape (lowest surface to volume ratio for all shapes, so it keeps the neutrons inside for longer) and by squeezing it from all side you get a much much higher density of the core material. This method is so good that nowadays all bomb use this design, even if for some reason its fuel is U-235. Both types of bombs weigh the same. Plutonium bombs require a lot better knowledge of nuclear physics and explosive lenses control in order to work properly. But once you do know how to make plutonium bomb the actual plutonium is easier to breed than it is to enrich natural uranium. So that's why all the big nuclear weapon states use plutonium bombs. On the other hand for countries like Iran building their first bombs they don't have enough hands on knowledge to be able to build a plutonium bomb with Fat Man design, so they go for Little Boy style uranium bombs because it's a safer bet, even if producing weapons grade uranium is way more involved. That's only for the actual Little Boy itself, later uranium bomb also use the Fat Man design so they don't have this problem. It's a problem with the particular design rather than the fission fuel itself.

So how is getting upset at people declaring their ribbons are done with all stock or challenges with blanket ban on plugin considered reasonable? They're not trying to assert superiority, that's just how they choose to play.

Yes from the look of things I'll probably wait for 0.22 for the upgrade so it comes up at the same time as stock subassembly. In the upgraded version all boosters are now controlled with 2.5m guidance package under the decoupler. I've had a few people asking for this feature since it turns out there's actually a non-negligible need for these rockets to lift payloads that don't actually have an upward facing control part (big rovers, whole surface bases, etc). One other bonus of relying on reaction wheel is that these rockets are now all fin-less as aerodynamic control surfaces are no longer required for roll control. I'll post a picture of the upgraded Nova when I get home.

Maybe maybe not. I kind of have difficulty imagining how Squad would do subassembly in a way that's radically different to how mods do it. But I suppose at the minimum file structures and that sort of thing will be different so I'll do a new guide. Subassembly aside, I did consider updating these rockets. The main update I'm thinking is to get rid of all the RCS systems on the boosters and replace them with reaction wheels for control and a pair of R24-77 pointed retrograde as deorbit engines. In fact I've already got a Nova with this new setup. The lift performance is a tiny bit better but most of the benefit is in the fact that it uses something like 30 less parts. I'm still wondering if that's a worthwhile change though. Does anyone actually ever use the RCS systems on these boosters for translation? Now that we can steer with reaction wheel we don't need steering authority from RCS any more. And with a pair of R24-77 for deorbit you can translate retrograde fine too. So really the only thing that'll be missing from the new build is the ability to translate forwards and sideways. But the only use I can think of for that is if you're actually attempting to dock a payload to something with the booster still attached.

Correct me if I'm wrong, but as pointed out Laythe doesn't have tides (at least not from Jool) because it's already tidal locked to Jool. So yes Jool's gravity still pulls on Laythe and the surface water layer will deform into a ellipsoid shape with two tidal bulges. But since these two bulges are stationary on the planet's surface instead of moving around like the moon-induced bulges on Earth there is actually no rise and fall of tides on Laythe. Since the tidal bulges are not moving, no mechanical work is being done and there is no conversion of Laythe's angular momentum into heat via tidal heating. In fact in the dim past when Laythe was not tidal locked to Jool it would have had tidal heating from the tidal bulges moving around on the surface. The fact that Laythe is tidal locked to Jool nowadays is precisely because Laythe has lost enough angular momentum via tidal heating that it's rotation has slowed down to match it's orbital period and therefore no further energy can be extracted into heat the planet via tidal heating? Of course other moons around Jool would pull on Laythe too, but surely those attractions are nothing compared to the overwhelming gravity of Jool itself and therefore don't deform the bulge enough to provide much heating effect?

What? As opposed to... using mods, but having the self-discipline to only use mods that are not game changing? Is that what you're trying to get at? If non-game changing mods are not "exploiting", then surely all stock is not "exploiting" either? This statement really bothers me because "compensate for KSP's shortcomings" could basically mean anything you want. "The lack of nuclear pulse propulsion in stock is a shortcoming!" I could say and insist that Orion drive should have been available in the stock game since it's 1960's technology here on Earth, never mind that fact that if Orion drive are available without restriction it renders almost all chemical engines obsolete. What one person sees as "shortcoming", another person sees it as a fascinating engineering challenged to be tackled with the tools available at hand. Before 0.20 everyone knew that stock helicopter was not possible and so required propeller mod, until one creative person looked at the issue, declared "no" and then built one with stock parts. Now everyone know that stock helicopters are possible and new ways of creating propellers out of stock parts continue to be invented (witness the recent breakthrough with reaction wheel powered propellers). This aspect of KSP where you solve problems previously thought impossible with creative engineering solution is very much the meat of the game in many people's eyes. Stock just happens to provide both an equal and comparable set of problems as well as an equal comparable set of tools to tackle these problems. That's why people are proud of things they've done in stock - because there are these engineering challenges open to everyone and they've come up with their own unique solution to the problem with the same tool that's available to everyone. What you see as "ridiculous craft fully of asparagus staging", others see fine pieces of engineering taken to an art form designed to push back the Tyranny of Rocket Equation using crappy rockets parts with such poor performance that no rocket engineer in real life would touch with a ten foot titanium pole.

If each to his own, then why does someone who put "done with pure stock" under their ribbon bother anyone?

Yes if you want efficiency you should always burn exactly prograde or retrograde in any sort of burn, unless you're doing an inclination change.

Interplanetary mothership design vary a lot depending on where you want to go. A Duna round trip mothership is going to be very different from a Moho round trip mothership for sample. Conversely using a Moho capable mothership for a trip to Duna is a huge waste of fuel and your computer's CPU clock cycle. So tell us where do you want to visit and what do you want to do there and we can get a better idea on what kind of mothership you need. For inspiration, here are three generations of my interplanetary motherships with payload attached. Each of these conducted a manned landing a return to both the target planet and their moons (other than Jool of course).

If we had ABS brakes on our rover we'll have people complaining "how come the brakes are so weak when I try to stop my rover on Gilly? Fix it!" and suggest options for "ABS override so I can brake as hard as I want!" in the suggestion forum One trick is to modify your brake action group so that front wheels do not stop when you slam on the brakes, this greatly reduces the rover's tendency to pitch forward.

PE kick is probably not necessary for a 24 minute burn. Remember once you actually start burning you are increasing your orbital altitude and thus your period. As long as you burn prograde and eject in the correct direction you are still nearly 100% efficient in converting your delta-V budget into actual delta-V. For a long burn this is what I do to ensure correct ejection angle: 1. Make a quick save 2. Take the length of the burn, start the burn at half of the burn time before the ejection point, so for a 24 minute burn I will start 12 minutes before the ejection point 3. Very import: follow your prograde marker at all time! 4. Once the burn is complete look at the ejection orbit if ejection path shows I will be dipping down inside Kerbin orbit it meant I started the burn too late, load the save and start the burn earlier if ejection path shows I will be leaving Kerbin at some positive radial velocity relative to Kerbol it means the burn was started too early, load the save and start the burn later if ejection path shows I will eject almost exactly on parallel with Kerbin's orbit around Kerbol it means the ejection angle is just right. When this happens your PE should be exactly on Kerbin's orbit for going to superior planet, or alternatively your AP should be exactly on Kerbin's orbit if going to inferior planet When you eject from Kerbin, once you leave the near vicinity of LKO your orbit will be nearly a straight line due to your enormous velocity. For the "just right" ejection angle compare your orbit to Kerbin's terminator, if they are exactly parallel then you've nailed your ejection. As long as your burn is all done prograde (instead of following the unmoving blue marker) and your ejection angle is correct then you're about 100% efficient, even if your burn is done over a wide arc. It's only when your ejection burn is measured on the order of month that you start to lose out big on not taking advantage of oberth effect. But even then the advantage of an extremely efficient engine might offset that loss. Von Braun once designed a Mars mission called Stuhlinger Mars 1957 which used crafts using ion engine powered by onboard nuclear reactor resulting in extremely poor TWR but extremely high Isp. The spacecraft will spend 4 month! burning prograde in a orbit that looks like a gradually wider and wider spiral until it's finally built up enough velocity to achieve Earth escape velocity.

What the blue node is telling you is you need to instantly add (correct me if I'm wrong) 2300m/s to your velocity for Kerbin-Jool transfer PROGRADE at that exact spot on your orbit. Both the "prograde" and "at that exact spot instantly" are important. The orbital projection after the burn assumes your burn is impulsive, meaning the delta-V is added nearly instantaneously. For a interplanetary transfer a burn of maybe a few minutes is close enough to be called "instantaneously", but as you already know if your craft has low TWR and it takes 30 minutes to perform the burn then we must modify the process, meaning burning earlier as you already know. But once we've modified how we perform our burn the blue marker for prograde direction is no longer useful for steering. Remember the velocity change you need to do your interplanetary transfer is calculated "prograde" and not just "in that direction". The blue marker just shows what that direction is if you are able to complete your burn instantly. If your burn is stretched out in an arc on your orbit then you need to burn prograde and not just follow the blue marker. When you perform a burn for hohmann transfer you really only care about the velocity added to either prograde or retrograde direction. Because over a period of 30 minutes your blue marker will drift significantly as your orbit curves a lot of your thrust at the start and end of your burn goes into changing your radial velocity (negative radial at first, then positive radial, so they cancel out and is a waste of delta-V). That's why dv counter down is moving so slowly despite your absolute velocity increasing at normal rate - your thrust is not in the correct direction to add 100% of the vector in prograde direction. Imagine in the extreme case your perform your burn on the wrong side of the planet so that the blue marker is exactly on the retrograde marker. You do a 2300m/s burn in the blue marker's direction and instead of heading for Jool you find yourself falling back down to Kerbin and now your delta-V required to reach Jool is 4600m/s. Even though you've spent 2300m/s you've actually increased your delta-V required to reach Jool because you've pointed your engines in exactly the opposite direction of where you need to add velocity, despite following the blue marker.

What's wrong with this? There are mods that make the stock game harder, but there are even more mods that make it easier. Even if mod parts are balanced against stock the fact that they exist gives you more options in designing your sure than all stock. So someone who's earned a whole load of ribbons all stock indeed have earned a bigger achievement than say, someone who earned the same amount of ribbons using Orion drive in addition to all the stock parts. The two achievements are just not comparable. So the guy who did it all stock certainly does deserve more props. My ribbons are earned with the help of KER and protractor, I'm not going to argue that "oh but these two are information only mods and therefore my achievement are as great as if I did it all stock" - I freely admit that whoever can earn these ribbons all stock had done something more impressive than me. On the other hand I'm not going to lose sleep just because someone can proudly boost that that they earn ribbons stock where as I can't. Challenges banning mods are all fair game, since that's the whole point of having rules in challenges - you play by the rule and try to score the highest points so that high scores can be compared. Challenges are not about trying to bend the rules so your existing craft can enter them with no additional effort required, if you don't like the rules of the challenges don't enter and start your own.

For Kebin the most accepted ones are apokee/perikee, some people really really hate those names though. None of the other orbits are used often enough to have commonly agreed upon unique names, I suppose if we go by how often the orbits are used the next two would be Kerbol orbit and Mun orbit. I would suggest: Kerbol - apkerblion/perikerblion Mun - apomune/perimune

Implied elitism? Now that's going a bit far don't you think? Yes I'm sure there are stock purists that bash mod users due to insecurity. But at the same time if you're going to interpret any statements along the lines of "oh I'm not aware of this roll issue with my craft because I don't use mechjeb and launch by hand" as an attack on mod users, is that not also a sign of insecurity projecting onto others?

For me, the centre engine is a LV-T45: Using aerospike causes your rockets to be aerodynamically unstable due to their lower than average drag. That's why I have so many winglets on the centre stage to provide control authority to overpower the aerodynamically instability. The top stage is powered by two R24-77. Since these little rockets are designed to be vernier engines they actually have vectored thrust, so there's plenty of steering. Even if the engines are not firing the craft is small enough that the probe core can easily turn the craft. I used ladders because seats were not yet available when I did the mission. The landing site for my lander is just under 5km in altitude, land it higher and you can shave off even more delta-V. I don't use mechjeb and I'm not so confident on my pin point atmosphere landing precision, plus back there there wasn't any really high detailed elevation map of Eve, so I decided to overengineer the lander and wing it. I don't use the kerbonaut's MMU packs as the final stage, if you do you can shave off another 500m/s off the lander's delta-V budget. For a two man lander it's kind of hard to do so I decided not to go for it. With two full MMU packs in orbit I decided to jet pack over to the mothership instead of attempting to do a docking without RCS:

I always advice people to attempt manned Eve landing and return last because it's the ultimate challenge of the full range of KSP skills for a player. Once you know all the tricks of the game you will be able to conduct this mission in a reasonable way. For example, the smallest possible two man Eve lander could be built to under 20 tons using a range of tricks like extensive asparagus staging (including vertical asparagus via radial engines) and using ladder/command chair instead of pod. Landing the lander on top of a mountain top also cuts down the delta-V to return from orbit from 12,000m to as low as 7,500m. Once you've cut down this most difficult part the rest of the mission would be easy. For example here is my lander at around 30 tons: With a lander this light I can then do my mission with style. Along for the ride I had a rover for Eve which landed separately and drove the crew around on the surface to explore Eve, including visiting the ocean: And also a two piece Gilly lander Here's the whole mission assembled around the mothership: The whole thing together is probably around 150 tons assembled in LKO over 5 launches (including one for tanker). http://forum.kerbalspaceprogram.com/showthread.php/30909-Two-men-Eve-landing-and-return-%28image-heavy%29

Before we start, let's have a look at two pictures: Here we have the Saturn V burning its first stage. The first stage is powered by five F-1 engines burning kerosene and liquid oxygen. The presence of carbon in kerosene results in the blindingly bright orange exhaust that turns into a sooty smoke trail. F-1 have a sea level Isp of 263s with a thrust to weight ratio of 94.1. Here we have the space shuttle orbiter firing its engines. The three SSMEs are cryogenic engines burning liquid hydrogen and liquid oxygen, resulting in a nearly invisible clear exhaust. The SSME have a sea level Isp of 363s due to much more energetic fuel but has a lower thrust to weight ratio of 73.1. Currently in KSP almost all of our liquid fuelled engines use the same blue SSME-like exhaust. Now I understand that we don't really want to separate liquid fuelled engines into three types (the other one is hypergolic fuel) and have triple the amount of fuel tanks we already have in game dedicated to each type, that's just too much trouble for very little gain. I'm happy enough with the generic "LiquidFuel" and "Oxidizer" for bipropellants. However as a compromise we should at least modify the exhaust so that the lower Isp higher thrust engines give off the orange "hydrocarbon" exhaust while the high Isp low thrust engines better tuned for upper stage retains the clear "cryogenic" exhaust. Solids aside, the orange exhaust in fact is already in the game: Back in 0.17 days the aerospike had an unique orange exhaust that gave it a lot of character. I propose that this exhaust effect is reinstated for the big Mainsail and Skipper engines, suitably upsized to fit their nozzles of course. The result will be: Cryogenic exhaust: (current blue exhaust) LV-T30 LV-T45 Poodle LV-909 Aerospike LV-N (exhaust is pure hydrogen) Hydrocarbon exhaust: (orange exhaust) Mainsail Skipper Rockomax 24-77 Rockomax 46-7S (funnily enough these two already have a miniaturised version of the turbulent orange exhaust) LV-1, LV-1R and Rockomax Mark 55 are clearly hypergolic fuelled engines owning to their low Isp and their form factor encouraging deep space usage. Hypergolic fuelled engines produce a clear exhaust very similar to cryogenic engines: So it's probably fine to leave them be. Although in the future if we could fine tune the colour so it stands out a little bit from the cryogenic engines would be good. This way I feel that it gives new player an intuitive feedback on roughly what the roles of the engines are, before they can make sense of Isp and TWR.

Get Jeb to come out and push the capsule retrograde with his MMU pack. When the pack is nearly empty jump back into the capsule to refuel and repeat. Once your PE is low enough hope in and ride the capsule home.

Yes it's a bad suggestion. When the ejection/phase angle calculator first came out there wasn't logic in place for going to inferior planets with prograde launches so the calculator always tells people to launch retrograde. There was a bit of an uproar that caused that logic to be put in. But the damage was done.

Your flight plan doesn't seem that far off so I'm still thinking it may be a technical issue. Anyway the way I fly it: 1. Go straight up until 10km. Usually this is around 2nd pair of booster separation, though lately I've been sending lighter than specified payloads to the Mun using the core stage as the TMI stage, in which case the 2nd pair will still be attached when I start the gravity turn at 10k. Turn your heading to 45 degrees 2. At 30km ap, dip down to 30 degrees 3. At 40km ap, dip down to 20 degrees 4. At 50km ap, dip down to 10 degrees 5. At 60km ap, go down to horizontal and burn until 74.5k ap 6. Circularise at 75k orbit A curve like this is a bit more efficient than having only two turning points, but I'm not sure if it's sufficient to explain that much of a difference. PS: if you're doing retrograde orbit then you need to reduce payload, going retrograde incurs a 350m/s delta-V penalty compared to prograde.

It's working fine for me for real payloads too: Payload mass 41.91 tons, Zenith V's maximum payload mass to LKO is 43.13 tons Delta-V with booster: Payload in orbit: With subassembly I'm told that Subassembly Manager has the exact same problem saving subassemblies as the old Subassembly Loader, so yes save manually and copy your craft over.

I can't seem to replicate the issue: Zenith VII: Nova: Both KER delta-V read out and experimental evidence point to them working as well in 0.21.1 as they did in 0.20.2

There are some specialised purposes that Ion engines are uniquely suitable for. For example: This low Kerbolar orbit observatory has 8000m/s of delta-V in its final ion stage. At this distance from Kerbol the two solar panels generate phenomenal amount of power that could easily drive three ion engines (and then some) continuously. So for this use the ion engines give 8000m/s of the total 18,000m/s at launch for very little payload mass.