Quincunx

No joke, I literally thought "hey, I wonder if camacju ever did that Moho mission?" And it turns out you posted the update yesterday. That is too perfect. And holy Christ! That's nothing short of amazing! I think you can truly be dubbed the king of orange tank efficiency now. You, sir, are a steely-eyed missile man. -Qx

Right... Derp... Completely obvious... How could I EVEn say that Moho was harder to land and return from? It's like I don't know anything about this game... my apologies! I think you captured the gist of my argument in your second sentence. Moho is pretty difficult to get to w/o GAs. But GAs change the whole story. Then the question is whether one orange tank is enough, and I agree a single-stage craft would be more difficult still. It would probably be easier to stage the plane parts off. Still, being able to land horizontally should save you some dV through braking, and taking off horizontally should save you some dV from gravity losses, so maybe attaching the landing gear to the orange tank would be advantageous. Then it can take off from Moho like a wingless plane. You showed that airless horizontal TO from Eeloo is possible, maybe it's still possible with Moho's gravity? And I agree, if you use GAs to get to your orbit, the only disadvantage of a Moho PE encounter (more fuel to get the encounter) is offset by your dV savings. That makes sense. I'm a bit busy to try such a mission myself, but I might give it a shot later on. I'm also looking at your numbers for Tylo. If a fully fueled craft with (without) all the plane parts is 6642 m/s (8619 m/s), then you could stage the plane parts in LKO leaving you 6755 m/s dV. Then: - 850 m/s for Jool capture with GA: 5900 m/s left - Minimum 4200 m/s for Tylo landing and orbit: 1700 m/s left - Minimum 1600 m/s for Jool escape: 100 m/s left (!) Maybe a return trip to Tylo is barely possible on a single orange tank? I don't know how good the TWR of the RAPIER is, so it might not be suitable for takeoff from Tylo. Sorry for my ignorance!

Do I understand you correctly? 1. LKO - Munar GA - resonant Kerbol orbits: 850 m/s 2. Kerbin - Eve - Kerbin - Eve - Moho capture: 1050 m/s 3. Moho capture - Moho surface: 1150 m/s 4. Moho surface - Moho orbit: 1100 m/s 5. Moho - Eve - Kerbin AC - Kerbin surface: 1050 m/s Firstly, these dV estimates add up to 5200 m/s, not 5150 m/s. Assuming they're correct, your burn to break Moho orbit would leave you running on fumes. But the wiki has Moho orbital velocity as 795 m/s, not 1050 m/s, and the dV chart shows that a Moho landing costs ~870 m/s, not 1150 m/s. This frees up 280 m/s on landing and 230 m/s on takeoff. The margins are still tight, and GAs are definitely necessary, but it should still be doable with your single-stage craft. All told the mission would cost 4700 m/s. And in fact you could save even more with the braking technique from before when landing on Moho. By my maths, you have enough for this mission with a comfortable margin for error. What do you think? EDIT: I did some poking around on the forums, and it seems the consensus is that Moho is actually the hardest planet to land on and return from. There also seems to be some disagreement about whether encountering Moho at periapsis or apoapsis is better: Sounds like a Moho landing on one orange tank is more complicated (and difficult) than I thought...

And with that, you have authoritatively answered the titular question of this thread. Thank you!

Glad you're enjoying it! I for one am extremely pleased with the response and participation. Fertile ground they are indeed - but my chief impression is that you can get really good at this game if you happen to enjoy orbital mechanics calculations (which I do), so there's hope for me yet. It has been said, by me, in the OP I had another think (thinks are easy to have when first you take your mind off things!) and it occurs to me that there is another aspect that can be optimized. For a landing on Minmus with a spaceplane rather than a rocket, one doesn't actually need to come to rest before landing. This saves some dV and suggests the following pipe dream: 1. From an encounter trajectory, perform an orbital insertion burn around Minmus, then deorbit and use brakes to slow down. (Standard procedure) 2. After orbital insertion, instead of deorbiting, burn to lower PE to the surface of Minmus, then use brakes to slow down more. (Is this commonly done? It seems harder but appears to use less dV) 3. Instead of orbital insertion, encounter Minmus with PE just above the surface of Minmus, and burn once to an almost-circular orbit with PE on the surface. (Only one burn and dumping fuel in the gravity well - sounds good, but also harder still) 4. (Unrealistic?) Encounter Minmus with PE just below the surface of Minmus, and use only brakes to slow down. (Landing on Minmus for 0 m/s dV?!) I sincerely doubt KSP has brakes that can decelerate from a Minmus escape trajectory to orbital velocity at the surface. What I think is more realistic is this: 4*. (Less unrealistic) Encounter Minmus with PE just below the surface of Minmus. Use only brakes to capture into an elliptical orbit, and make multiple passes until velocity is below orbital velocity at surface. I think 4* will be the most fuel-efficient way to land on Minmus (heck, and Ike for that matter). At the risk of getting carried away, let's say we have 700 m/s dV to spare, assuming near-perfect execution of all burns and GAs. In camacju's mission plan there is already an Ike encounter (assist). If the above "tangential lithobraking"-type strategy is realistic, we can land on Ike for ~0 m/s dV. Taking off and getting back to Duna's SoI will cost (390+180+30) m/s = 600 m/s dV, whence you can escape Duna's SoI using camacju's strategy. We still have 100 m/s left over for corrections. I think it is possible to take an orange tank to land on Duna, Ike, and Laythe while having encounters with Jool, Vall, Tylo, and Eve. That would be an incredibly difficult mission, though. Thanks again for answering my questions and participating; this has been very informative - and entertaining!

Apologies for the bump, but I just had a think, and I think Duna orbit -> Laythe surface should be possible in <400 m/s. I just applied the same reasoning as you with the Kerbin orbit -> Duna surface calculation -- you can use Ike the same way you used the Mun. I'm not sure how many Ike GAs you need, but ideally you should be able to use one or more Ike flybys to get kicked out of the Dunan SoI and then spam resonant orbits again. 360+30 m/s to get an Ike encounter, and maybe ~10 m/s to set up the multiple GAs, and you should be good. Duna->anywhere in 400 m/s. Let's say your Kerbin orbit->Duna surface was 50 m/s more than the ideal, Duna orbit->Laythe surface 150 m/s more, and Laythe orbit->Kerbin surface 100 m/s more. That's 300 m/s, and with the 423 m/s dV you brought home, you'd have more than 720 m/s extra. According to the dV chart, it costs 860 m/s to go from Kerbin to the Minmal surface and land at Kerbin (assuming aerobraking at Kerbin to get the Minmus encounter and later AC during reentry). Darn, looks like Minmus is still just out of reach. Maybe with a better ascent from Duna or Kerbin one could save the remaining 140 m/s? I don't honestly know if what I'm proposing is possible, but that SST Duna and Laythe with landings at both is still crazy awesome. Well done again, camacju!

I think if you do a single Mun gravity assist and burn at Munar PE for Duna, you lose out on the Oberth effect from Kerbin and therefore actually cost dV relative to a direct insertion rather than saving it. Multiple Munar GAs can be used to eject you from the Kerbin system, whence further GAs (executed like camacju did) will add to your savings. I'm sure if you give it a try, you will confirm that a direct insertion is more efficient than K-M-D, and multiple GAs are the way to go.

Apart from Moho, Eeloo, Bop, and Pol, basically a grand tour of the old Kerbolar System. On one orange tank. ... "You, sir, are a steely-eyed missile man." If this were a (n active) reddit challenge, you definitely would get some sort of flair thingie. I guess the best I can offer you is a quote (for your sig if you like): Camacju, you took a single orange tank on the greatest road trip of its life. You have beaten hardereresterestest mode. ... actually, now that I think about it, I could probably learn a lot from your mission, especially in terms of dV. Can you clarify the order in which you visited (regardless of assist/flyby/landing status) the bodies? I'd like to analyze the dV savings with your GAs relative to what is expected according to the dV map.

Thanks, that would be awesome! I don't know if your mission is still running, but if you're taking requests, would you be interested in flying around some more (Ike, Mun, Minmus or whatever)? Your posts in this thread have been both informative and entertaining.

Do you have the thread link? I suspect such a discussion would have addressed many of my questions (including ones I don't yet know I have).

My Kod, camacju. That is simply amazing. [:O] I bet I can learn quite a bit from those images you posted, too. EDIT: You say your first Mun encounter was suboptimal as in > 850 m/s. I'm looking at your remaining dV and it seems you went from 4859 m/s dV to 4008 m/s dV, i.e. an 851 m/s burn. Am I missing something or were you just being that literal? And you got from there to Duna in an additional 21 m/s. Wow. That's even more incredible to me considering the route you took was...let's see... K-M-M-M-K-M-D? The original mission plan I had in mind was to land on Ike, get a Duna flyby, and return to Kerbin, but as it is you could probably land on the Mun and maybe Minmus with fuel to spare! Another thing I'm wondering - if you start this mission using air-breathing engines, can you dump oxidizer to get into orbit with even more dV to spend? EDIT 2: Contemplating about a Mun landing on the way back got me thinking: How fast are you moving on a return from Duna? Should one attempt to get a Mun encounter instead of a Kerbin encounter, or is it more efficient to AB around Kerbin and get a Mun encounter that way? All things considered, I'm still a newbie, so forgive the potentially dumb questions!

No worries, I guess this chart is lost to the aether. Now I'm starting to wonder if GAs in the reverse direction can be done to get to Eve, for a follow-up GA to Duna. Clearly there are a lot of possible mission plans to consider. Some of them make sense (i.e., they are provably better than a direct insertion), and some of them don't (they are provably worse). Most of them look really difficult, though. Perhaps a challenge could be to attempt some of these GAs to Duna and see how much dV each of them costs. Anyone interested? EDIT: On page 16 of the community dV map thread, in response to Benton: Snark replies: In addition to those problems, GA-based dVs are basically Markov chains - previous states (such as whence you come) affect how much dV they cost. Still, it would be nice to estimate them for these missions. Also, before anyone comments on it - I am fully aware that lining up multiple GAs not only is extremely difficult, but also requires the assisting bodies to be configured correctly to permit the assist in the first place. Since right now the discussion is theoretical, I'm assuming that all assisting bodies are correctly positioned for whatever GAs that mission requires. Incidentally, does anybody know how to calculate multiple GAs with KSPTOT? Maybe there is a tutorial somewhere, but I haven't found it yet. EDIT 2: Looks like FF does what I need. EDIT 3: Wait no. I don't have info on Munar/Minmal GAs. I guess I'll still have to do that with KSPTOT. ... I'm obsessed with gravity assists. -Qx

Thanks VoteSquid, but I already looked at this chart and don't see any mention of GAs (which is the rather salient point here). Please correct me if I'm wrong. Also, referring to this thread, it seems I may have this all wrong. Maybe I want an Eve GA for these purposes.

Thanks for the advice, Gargamel. In the meantime, though, I would still really like to ask my theoretical question: What is the minimum amount of dV required to get to Duna from LKO? I'm envisioning several scenarios based on the above discussion: Kerbin-Duna (because...yeah) Kerbin-Mun (burn at PE)-Duna (this seems to cost dV because we lose out on the Oberth effect) Kerbin (burn in LKO perfectly)-Mun-Duna (this seems good, but potentially hard?) Kerbin-Mun-Kerbin (burn at PE)-Duna (get the benefit of the Oberth effect again) Kerbin-Mun-Minmus-Kerbin (burn at PE)-Duna (does this eject me from Kerbin's SoI altogether? If not, should be better than 4.) Kerbin-Mun-Kerbin-Mun (burn at PE)-Duna (if one is good, two must be better) Kerbin-Mun-Kerbin-Mun-Kerbin (burn at PE)-Duna (I'm not sure if I'm still in Kerbin's SoI at this point) What he suggested-Duna Again, if anyone knows where to find the chart that has these data, that would be stellar.

Because I'm a cheapskate who got KSP back in the bad old days and don't know how to update it.

Thank you, camacju, for your participation! To be perfectly honest, rather embarrassingly, I am still on KSP 0.22 and I did not even realise the Rapier is stock... I've been trying to do this using two nuclear engines and a pile of jet engines with a whole stack of intakes (plus aerospikes if they help). Since you roundly crushed the original challenge, are you (or is anyone else) up for hardereresterestest mode with these engines only? As for your suggestion, let me confirm what you proposed: LKO - Mun encounter - Kerbin orbit (?) (with high eccentricity) - Mun encounter - ... - Kerbol orbit (6:5 resonance with Kerbin) - Duna transfer Versus what I had in mind: LKO - Mun encounter - Minmus orbit - Minmus surface - Minmus orbit - Kerbin encounter - Duna transfer The main issue I had with the approach you advised is that I thought a prograde Munar flyby (not the kind used for free-return trajectories) would eject me from Kerbin's SoI and then it would be very hard to get further GAs. If one Munar flyby only kicks me into an eccentric Kerbin orbit (without burning at periapsis) then that definitely makes sense. I guess my real question is this: What is the minimum amount of dV needed to get to Duna from LKO? Apparently there is a chart somewhere that shows dV for GAs but I have been searching for it to no avail. Referring to the community dV map, which I'm assuming is not outdated, a direct burn to Duna starting in LKO would cost about (930+130)m/s or 1060 m/s (direct insertion). According to the thread I linked before, a Mun - Duna GA would cost 414 m/s while a Minmus-Kerbin-Duna GA costs 306 m/s. Now, I'm not sure where either of those start from, but Slashy indicates LMO to Duna costs 467 m/s for him, and looking at the chart it's already 860 m/s to get a Munar encounter in the first place. So except for that really rare scenario where you set up a burn in LKO that encounters the Mun and goes on to encounter Duna (with maybe a few small corrections), it seems that a Munar GA to Duna is more expensive than a direct burn. In any event it's not possible to save more than 200 m/s, the delta between dV to Duna (direct) and dV to a Munar encounter (d^2V?). Not that it's easy, but I'm starting to think that in terms of dV the most efficient path to Duna is through repeated Mun encounters. The perfect no-burn Munar GA definitely saves some dV, but not the full 200 m/s because the burn in LKO also has to line up the Duna encounter afterwards. If repeated flybys can get you to a 6:5 orbit for the price of a Munar encounter, that may be better. Honestly, I don't know. Is the aforementioned GA dV chart still around? I don't think my question is much about actually carrying out the mission so much as theory now.

Hi! Quincunx here. I'm a physics PhD student and long, long time watcher, first time writing. I have a deep love of orbital mechanics and rocket science in general, so KSP was the perfect fit for me. I know this is daring for a first post, but I have a "mission idea" fueled by so much curiosity it compelled me to make an account. The one thing that always got to me about KSP was the Rockomax Jumbo-64 fuel tank. It can hold an awful lot of liquid fuel, and if you design your rocket appropriately, that much dV can get you far. So I wondered: How far, exactly? To my delight, there was a reddit challenge and Scott Manley video featuring this very question. The challenge was, using only an orange tank, stock parts, and no RCS, to bring a probe with the accelerometer, thermometer, magnetometer and gravioli detector for a Munar flyby and return safely. Hard mode was to land the probe safely on Duna instead. And, of course, Scott executed "hardererest mode" with a landing on Duna, then on Ike, and back home (almost) safely (and Desolution did even better) - but he also mentions having pondered a possible visit to Minmus as part of the trip. I checked out this old question on the most efficient way to get to Duna, and it seems like the consensus (among at least two people) is that the minimum dV is expended by getting a gravity assist from Kerbin after a Minmal encounter (when Minmus is closer to Kerbol than Kerbin is). This makes sense, since one gets the benefit of the Oberth effect from executing a transfer burn inside Kerbin's gravity well. And, of course, we can do the reverse with Ike and Duna to come home, going the other way around to get kicked into a lower Kerbolar orbit. I am also aware that, when the Mun is properly positioned, a gravity assist from it can save fuel en route to Minmus. All this to say: Is the following "itinerary" theoretically possible with a crewed single-orange-tank craft, even if it takes a master to perform? Take off from Kerbin, and get into LKO. Burn for a Mun encounter, and get a flyby gravity assist to Minmus. Land on Minmus. (Wait there until Minmus is in the right position and a transfer window to Duna opens up.) Take off from Minmus, and burn at the Kerbin encounter to transfer to Duna. Aerocapture, aerobrake, and land on Duna. Take off and land on Ike. (Wait there until the transfer window back to Kerbin opens up.) Get one final gravity assist off Duna and return to Kerbin. (Land safely.) Now, I'll admit I haven't done the dV estimation, though not for want of trying - while I'm familiar with the celebrated dV map, I just can't find an application to calculate dV for gravity assists, and I don't know how to make KSPTOT 1.6.7 do the maths for me. However, by my estimate, if 1-4 is not actually cheaper than a direct burn to Duna from LKO, it should only be slightly more expensive. So is this insane mission even possible with a single orange tank? If necessary, it would be okay to drop the scientific gear, use a probe, and even nix the Minmal landing if absolutely necessary. I'd be happy with a definitive answer based on how much dV you can squeeze out of an orange tank with nuclear and jet engines. And if anyone could actually fly the mission, they would be Jebediah simply amazing. Sorry for the text wall. :)