Hotel26

A tour de force! Well done.

I think my personal yard-stick is total-fuel-to-orbit / Mission-Controller-wage-kerbucks: the most fuel for the least launch. But I know I am going to learn from your submission!

I will enter my Titan 3 'Kakophony' for this. Stats are: payload: 1,993t to LKO launch vehicle: 5,301t (7,294 - 1,993) part count: 279 (launch vehicle) + payload 72 = total 351 TWR: 1.89 (launchpad, KER) The real payload for me is: 308,000+ kallons of LFOX delivered to LKO, 1540t (I'm entering Kakophony simply to publicize this machine, of course! Now, nervously awaiting the entry of @Pds314... )

I'm very curious about this beautiful machine. Are those rotors tweak-scaled or do these super-large parts exist in some version later than 1.7.3? Also, I see that you have both sets "sunny-side up", i.e. with the paint markings visible on the upper surface. Yet they look reversed in the manner that would be consistent with them being contra-rotating. How did you do that? OK, I see you have a KerbalX site: https://kerbalx.com/Bob_Saget54. Any chance of posting this appealing machine?

A very nice machine! What's its speed & range?

Good on you! I myself hadn't forgotten about this and was still hoping to be only the second recipient of the Kerbin Helicopter Circumnavigation badge (after all the work I put into it!). You look set to beat me out for it. Go for it!

The advent of this mod is likely going to be the Imminent Cause of me finally upgrading from 1.7.3 to 1.11.x. Thank you, HebaruSan.

OK, so I finished my testing with the following variables being noted: target station at 100km altitude my launch vehicle was a Genesis Hotel26 at the controls (YMMV) And I found that a target phase angle of 335 gave me a 14.1 km intercept (which I ignored), an actual closest distance of 10km (while still performing the circularization burn) and a final lagging distance of 19km. (That's less than 5 secs of travel at orbital speed). If I were to do another test iteration i would try phase 333, which translates to a target longitude of 102W. Hopefully, it the above doesn't actually answer the OP's question, it details the methodology to self-determine it. (And I learned something myself in the process.)

So, just for fun, I've started testing this with regard to the OP's question. I'll describe the methodology and then publish some results when I get finished. Two things become clear at the start: Differences: different vehicles perform differently different pilots fly differently different days: different results (but hopefully this will average out) It should be possible on any standard launch to rendez-vous in one orbit. The conclusion of point 1 above is that everyone interested would have to test this for themselves. I used to fly a fairly high trajectory but find these days that I use a flatter, faster trajectory that gets me a lot further downrange before apoapsis. I've already found I need to wait later before launch. I put a small craft into a perfect 100x100km equatorial orbit as my reference target. When it hits the "mark" (nominally starting for me at this 36 degree uprange point) I launch and then fly the launch vehicle in a standard way: e.g. 60 m/s pitch-down 5 degrees and then fly SAS Sfc Prograde until AP becomes 100km . Circularize at 100km altitude and then note the distance to the target: before or ahead. Then tune the AP upward if ahead or PE downward (but no lower than 70 km) if behind. I do this looking also at the intersection markers in the Map View, tuning the nearest distance to a minimum. That should get me rendez-vous in one lap unless the launch window or flight trajectory was really wrong. Your closing dV as you initiate the target retrograde burn (times 2) is a measure of the inaccuracy penalty of your operation. Returning to the target distance at circularization, this is the amount to tune the target launch mark by. Note that 1 degree longitude is equivalent to 10.47km circumference (not quite the same as line-of-sight, but near enough for government work). It seems like this exercise is worth doing for each vehicle that one flies frequently. Knowing this launch point should similarly optimize the DL2RV (direct launch to rendez-vous).

Every interesting challenge KSP presents is fun to study and master. That's why I don't think this is either-or. It's good to start with exactly the question the OP is asking and the result is important when you have a minimal dV launch that fails if it is not efficient.[*] Then (as you say) it's fun and instructive to master the direct launch to rendez-vous. So master both. Then think of SpaceX and its "burn back" self-landing boosters. These CANNOT be optimally efficient in terms of orbital mechanics because the overall dV delivered to the payload (and upper stages) has to be less, as some thrust is reserved for the burn-back. Why does SpaceX do it? Due to the commercial/economic equation of fast recovery/recycling. Which sets us up then to think about how we play KSP. Once you've demonstrated the ability to do the super-efficient, tight-budget launch, do you want to repeat this for every launch for the rest of your KSP career? I'm referring to all the time for all of those finicky rendez-vous maneuvers. I finally decided I didn't. (Although I still have occasion to use both kind of launch.[*]) So: choose both. Double your fun. Maximize your own, personal playing efficiency. Life is short. [*] above. Titan 3 is exactly the kind of launch that I would normally do "super-efficiently" to a 72-75 km circular orbit -- with NO rendez-vous -- and just leave wherever it arrives. The client space stations simply then send nuclear tugs with a relatively large fuel capacity to come rendez-vous with the Titan; and then cart the fuel back to the space station. Or in some cases, directly to a client ship waiting in orbit for a refuel prior to interplanetary departure. A whale with pilot fish...

A night-time launch; couldn't be helped. (Tremendous screw-up @ 5:55, but survived.) Critique: I should have selected Retrograde immediately after selecting Target Mode. and waited for attitude stabilization before S2 separation out of habit, I used a long, flat trajectory which delays the rendez-vous, resulting in a bulging apoapsis (121km) for a target at 90km altitude. It does demonstrate, however, that this approach is quite resilient to noise in the inputs. All that matters is a) how close you get, b) how prompt you are on triggering that target-retrograde burn and c) your inclination is not too far off (as that will be the final arbiter on accuracy).

tldr: many adhere to the rule of thumb of when your target is over the nearest southern tip of the desert to the West of KSC and over one body of water. That's 110W or 36 degrees uprange [KER Rendezvous display Phase Angle 324 deg.]. I find KAC, Better Burn Time and KER indispensable for a "direct launch to rendez-vous". If the initial phase of the launch goes well, it's easily possible to tune the apoapsis directly from the KAC "Closest Approach" display for "within 1 orbit". With practice you can get a rendez-vous at or near launch apoapsis within a few kilometers. You really need Better Burn Time due to the massive closure rate for this rendez-vous to know when to fire. This maneuver will be performed Target Retrograde. And it's performed in place of circularization, so it's an alteration to the typical launch pattern. To be clear: your lift-off burn continues until you get the closest approach indicated (rather than a particular apoapsis). Then instead of circularization (if everything works out), your target retrograde burn completes the rendez-vous (zero relative velocity) and you are hopefully much closer to your target than 10 km! I know of no maneuver or operation in KSP more exhilarating than this one: stopping within several kilometers directly at the end of launch (precisely because, until the very last couple of seconds, you remain in complete disbelief that you will be stopping in time!). [You beat me to the punch, @bewing!]

The Incremental Refinement Dept has been at work today -- on my Zephyr workhorse lifter. Fine-tuning the weight & balance for easy return to KSC... and "canning" the procedure for replay every time Final descent rate is 9.8 m/s... too much for the Rhino or fuel tanks -- but OK for the nose gear and tail fin Inspection confirms full recovery. I doubt it's rated for water landings, but when you can pinpoint your touchdown to within a hundred meters or so, who would want to land in water?

My very first envoy to Eeloo will be arriving in 1h 50m to top up fuel for departure (in 7d), so KX1 Pole Star has begun preparation... [Translation from Kerbalese: "all KSC Mission Controllers are instructed to change wallpaper on all mission-critical monitors"]

I've been playing a 1.7.3 world, Orbit, since January, 2018. I have an iron-clad no-warp-past-30m rule, so it's moving at about the same pace as NASA. Footholds on Gilly and Ike, so far. I booted up a parallel, 1.7.3 world, Splice, a couple of weeks back. So breezy to run a world with only a few craft. Anything that doesn't go well gets torpedoed immediately. Debris is fine. Missing Kerbals?? "We have no record of that." Warp speed ahead. (I have to watch the old habits carefully, though!) I have 3 ships in the final orbit for Moho, all looking good. (One of those slid by as close as 67,000 km with Moho in plain sight but I wisely elected to go the extra orbit to get actual capture.) Jool and Duna transfers open up in between arrival at Moho, though. So I am preparing a brace for Jool. Here's JT1 Tetrahedron, a relay ship [in the background], about to get a get a final top-up of fuel from KC1 Crab: I fit everything out with 2.5m docks as standard, but the Tetrahedron in the background has no docks exposed. The Crab will use its Spear to accomplish the dock. It's always so finicky to dock two largish ships with a claw, though, don't you find? [Click & Arrows for comic strip] "So Spear detaches from the scrum... It goes deep... WHERE'S Defense?!! aaand... Touch Down; right around CoM!" With Spear docked with the target, it is commanded to "adopt the pose", docking port facing the Crab supply ship. The Crab slides down the "fire pole"... Only two large tanks to fill and the infusion of rocket lifeblood is all over in a minute. Crab retains plenty to return home to KX1 Egg space station. Oh, yeah. Why is this new, parallel, 1.7.3 world called Splice, I hear you ask? Very good question. Stay tuned.

Congratulations. New name fits on one line, etc, etc. Very nice & tidy.

Go here and request:

(I was just starting to update my post above to abbreviate/make it more helpful/productive -- and clearer about Snark being correct -- but I'll let it stand.) In the general case, a bi-elliptic is simply a series of two Hohmann transfers, but linked at the common apoapsis/periapsis. I think a bi-elliptic to a lower orbit is always high-energy (meaning, more than a Hohmann). And a bi-elliptic to a higher orbit is mostly always high-energy (and a waste of time because you could have waited at home for the window and got there sooner), except in the special case described in Snark's reference, in which it works out better (making it "low energy", as an exception). I think Snark's term may fit the maneuvers you describe more closely (especially given your description, "cochlea"). But maybe "high-energy transfer" describes the intentions, trade-off and costs usefully.

Great tip in your post, by the way, Snark! My reading of the bi-elliptic transfer is that it is a low-energy transfer in a particular case, in fact, in which it takes longer to arrive but pays off by using *less* energy than the Hohmann. It would have its own transfer window, so wouldn't be the way to "go anytime Therefore, I think you may be right. The above statement from the poster is the litmus test. Everything else in the maneuver sounds more like a high-energy transfer. We'd have to ask the poster whether the intention in his case was to "go anytime" or arrive cheaper. But he does also say this: "it's more expensive than launching in the window". Perhaps the resolution is that "bi-elliptic transfer" is, like, "high-energy transfer", a very generic term, implying nothing detailed about application. Your reference does say: may, in certain situations, require less delta-v than a Hohmann transfer maneuver"; keyword being 'may'. However, it does also specify that the entry to the second eliipse is performed at the apoapsis of both. In a HET, you have the option to ride around the inner trajectory (lowering AP below the target orbital altitude) for a while to catch up, which is its value. We got to discuss both, so that is good. (More on HET: Banish transfer windows.)

This one sounds like a high-energy transfer...? (I can't find a better reference for the moment.) It spends energy (more than the Hohmann) to get there sooner than waiting for a transfer window.

An interesting approach (and I am by no means an expert on Moho). If I understand you correctly, noting that Moho and Kerbin share a mutual AN and DN (of course), you depart Kerbin at one of those, lowering your PE (at the opposite node) to the orbital altitude there of Moho. Burn there to reduce AP to get an intercept with Moho one orbit later. At this point you've made no inclination change (except possibly trying to incorporate one in the Kerbin departure burn (very difficult to judge)). The idea then is to enter the Moho SOI and handle the inclination there (at much lower relative speed)? Have I understood that correctly? If so, I would add the following: one of those nodes has a lower solar altitude than the other and the relative speeds at intercept will be quite a bit lower than at the node at the higher altitude. (In fact, intercept at Moho's perihelion is the optimal point.) And since Moho's orbit is 102d, it'd only be a max of another 51d to wait for the better node. However, this does not detract from you general point, esp. as Dres and Eeloo have much longer orbits. The interesting take-away is to stage the intercept without bothering to remove the inclination beforehand??

Granted although I wish anybody knew what was just asked and granted. Something bad is bound to happen! I wish everyone knew that 2 microns is 1,000 times larger than 2 nanometers. Then all of us could all breathe again.

This requires greater energy for manufacturing. Granted. Now the sun shines 24 hours a day in your country and the wind speed never diminishes below 32 km/h. The tides have also picked up, so there is some risk of flooding in the lowlands. Now you have all the electricity you need. Oh yeah, I wish I could be 2 microns tall in order to do as I please and escape attention.

I'm a one-game addict but the previous addiction was Minecraft and, yes, lately, I've been working a little Minecraft into the mix again. I love the Operations Research aspect to the game. Diamond mining sure does feel like the one-armed bandits in a casino, though. I had a grand-scale project for a while to link all villages in a 10km x 10km map together in a rail network. Wrote programs to compute the minimal nets and to compute the XY gradients to route elevated track over the desserts, tundra, through mountains etc. Thousands of hours.

OK, to be constructive, you are asking a very difficult question about an extremely complex operation. Bravo for taking it on. I think the only person in the forum with any chance of helping you with this would be ... @Snark