Teutooni
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Posts posted by Teutooni
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36 minutes ago, Dman979 said:
What about asparagus or onion (Each inner stage is fed by an outer stage, which is fed by another, and so on. As apposed to aparagus, where usually 2 stages feed all the other ones, and then get dropped away.)?
Have you factored in the weight of the decoupler, too?
The way I understand staging is, parallel or onion staging is less efficient than serial (stages on top of each other, i.e. the normal staging method), but they benefit from all kinds of TWR considerations. Asparagus is one of the most efficient staging methods when considering delta-v, mass and TWR. TWR (or TMR) was left out of this consideration on purpose. In any onion or asparagus staging that preserves centre of thrust and mass, two fuel tanks need to be dropped at each stage. In serial staging only the dead weight of one near empty fuel tank needs to be dragged along until each separation, thus making it slightly more efficient in terms of delta-v.
Actually come to think of it I might be wrong on this, needs checking.
Anyway, in my calculations I used ~3 tons extra weight for each stage consisting of the engine, decoupler and any other stuff I might want to slap on, such as struts. This 3 tons is vanishingly small in large stages though and the actual final payload has a high impact on just the first few stages. Remember I considered rockets potentially trillions of tons in mass driven by a single 60kN nerva, so yeah...
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I remember seeing this thread a few months back. I had a few hours to waste in matlab trying to figure out what is the theoretical and achievable maximum delta-v stock KSP can achieve (you know, for excrements and giggles).
Single stage
Pretty straightforward, obtain fuel tank full mass to empty mass ratio (9 to 1 for most tanks in KSP), and plug it into Tsiolkovsky rocket equation. As your fuel tank mass approaches infinity, the total vessel mass ratio approaches this dominant fuel tank mass ratio:
dV = Ve * ln(m0 / m1)
For LV-N, it is around 17km/s.
Serial staging
Now it gets a bit more complicated. I figured there needs to be an optimal point for each stage that maximizes delta-v and minimizes mass. Pretty straightforward, divide delta-v by vessel mass and calculate maximum.
https://www.dropbox.com/s/6baik93mnluxl8w/dv.png?dl=0
This shows the total delta-v as a function of number of fuel tanks. In this example I used mk1 liquid fuel fuselages as fuel tanks, with total payload + engine mass of 3.3 tons, up to 100 fuel tanks.
This plot shows the delta-v divided by mass. There is a clear tipping point at 2 fuel tanks, after which it goes downhill. In fact, I discovered that for all subsequent stages, the delta-v-to-mass ratio tipped at around 5.98 km/s, no matter how far down the staging. Obviously this number depends on the engine and fuel tank mass ratio. This resulted in some interesting simplifications, namely that to get an optimal serial staging, each stage added roughly 6 km/s to the total delta-v and multiplied the total mass by about 2.5.
Now we can calculate some large numbers to get really high delta-v. Let's say interstellar travel would require 200km/s delta-v. 200 / 6 = 33.33 stages. This would multiply the first stage mass (8.3 tons) by 2.5^32, roughly. Which is about 45 trillion tons. Speed of light would be possible in theory (newtonian physics), but would *still* require a rocket with a mass of roughly 10^20000 tons. I think you'd have a hard time coming up with a multiverse theory that had anything in that kind of scale. Note that there is no true theoretical limit of delta-v, but the exponential mass curve will quickly shed any ties to reality.
In practice, serial staged rockets with LV-N can reach around 65 km/s with part count in the high 2000s. Obviously this massive ship would need to be assembled in orbit and would have an utterly useless TWR, requiring probably thousands of years to burn. But it's in the range that *could* probably be built in game with a monster PC.
Btw while ion engines have decent ISP, they have truly horrible fuel tank mass ratio of a bit over 2, so they are actually only about 2 to 3 times as good as LV-N for total delta-v. So for example for 200km/s, you'd need 15-22 trillion tons instead of 45.
An actually useful figure from all this could be the optimal stage delta-v for each engine type in serial staging. This can give you a rough idea what to aim for for each stage.
ISP optimum stage dV
300 2240 m/s
350 2616 m/s
800 5980 m/s
4200 15200 m/sThere is a possibility I missed something crucial, so any comments are welcome! The numbers do seem reasonable in my experience.
EDIT: Pffft how do I embed images?
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9 hours ago, DiamondExcavater said:
How much Delta V does this ship have? is it designed for most planets? Yeah and definitely OTHER, or if its big it can be BIIG Rockets
I owe you a bit more of an explanation do I?
Earlier versions were lighter with mostly stock parts, ~50 ton vessel with ~4km/s delta v. They were for exploring Mun and Minmus mostly.
This is one of the latest with a lot of near future technologies unlocked, 100 tons, over 10 km/s delta v.
They were all designed to return to Kerbin orbit after each mission, dock with a crew capsule which returned science and crew to the surface. Then a fresh crew would fly up and dock with the ship, followed by a refueling drone, followed by possible lander or other mission specific thing. The lander would attach to the forward large docking port, preserving centre of mass relative to centre of thrust.
I will probably start experimenting with full blown arkships with ISRUs, full closed life support loops and such when some key mods are updated to 1.1.
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I recently did a career based around the multi-mission space exploration vehicle concept. That is, a modular reusable spaceship with the core ship being reused and customized with different mission packages (landers, extra fuel tanks and such). So, "other" I guess.
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17 minutes ago, HebaruSan said:
NASA administrator's job isn't actually fun
I'd imagine that's mainly down to the pressure to succeed, interpersonal drama, stress and deadlines and such. I doubt many people really like high pressure management jobs in their entirety. But it would be a game. Did you fail miserably in budgeting? You won't be fired, just start a new game. Distilled down to strategy and resource management without stress and drama, management can be quite fulfilling. This is one reason we play games instead of doing the real thing - no real consequences for failure.
You can argue that KSP should just focus on it's strengths which is building and flying rockets. It's why we're all here, we love building and flying the rockets we make. But that calls to question the point of the career mode over sandbox. I think it's entirely reasonable to expect a career mode to be a light management simulation. The game's called Kerbal Space Program, not Kerbal Rocket Builder or something.
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44 minutes ago, HebaruSan said:
Suppose they do add a reasonably accurate management simulation. Is it simulating something fun, like rocketry and astrogation? No, it's simulating being a bureaucrat. The more work they put into it, the better a simulation it will become of being a bureaucrat. And if your space program starts to tank, how will it feel if it seems to be happening because something's wrong with the modeling of wages? Better to focus career mode on driving engagement with the core physics gameplay via missions and some kind of tech progression.
Well I think there are two kinds of expectations for a career mode. One group just want a progression system. Another group is dissatisfied with the current career mode (contract slot machine grind) and would like more management aspects to it. Like I said some people actually enjoy management games or "bureaucrat simulators".
For me the current system is fairly pointless, save giving a sense of attachment to the crews and random mission ideas generated by the contracts. Which is why I play career much like sandbox. I've done the progression so many times it's pointless without an added management element to it.
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12 hours ago, regex said:
Ideally I'd like a career where rockets took time to build and roll out to the pad, science took time to research, and buildings took time to get built (KCT), where you set individual goals or designed missions and assigned part of the yearly budget to them, minding the upkeep for each project since they might run into the next year, where doing science didn't accumulate you points it instead earned you rep or additional funding for the same area of research, where rep determined your yearly budget, where parts were researched over time, where astronauts had salaries and buildings required upkeep. I wanted to run a space program.
This. There are entire games based around management which, though certainly not for everyone, can be quite fun. Building a legitimate light management game around career mode would certainly add a lot to KSP in my opinion. KCT is fantastic and adds the time aspect to things but doesn't touch other parts. What career mode needs imo is a much more interesting resource management on program level. Something a bit more complex than "do I have kredits to launch this thing?". Upkeep for things, wages, training programs, running R&D costs, etc. This might be a bit too much for what Squad has in mind for the base game, so maybe mod(s)...
One thing that always puzzled me was the science points. How exactly does knowing the composition of a mun rock help me develop a new guidance system? In my opinion science should be the success condition for contracts and/or be used to generate income by selling the data. This income would then be used to fund R&D programs. I know it's a game and games love all kinds of point systems, but still...
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What I like about career is the experience kerbals get. New kerbals are costly, and training them to be decent takes a good few interplanetary missions for each crew. Losing them actually matters. Sure you could (and should) try to ensure every crewmember returns safely in sandbox mode too, but there is this tangible extra bit of risk in career mode.
Another thing in career is the contracts, I usually look through available contracts and see if there are any that fit a mission I was planning to do anyway. Sometimes it adds interesting secondary goals to the mission I would not have originally considered, like bringing along a satellite to map planetary resources, or change a simple landing into a more permanent base, or pick up a new kerbal on the way.
That said, I play career mostly like I would a sandbox - do science and funds on a best-effort basis and focus on my own thing.
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So while waiting for 1.1 I decided to give making a flag a go - never done any logo stuff or graphical design. Absolute Horizon Aersopace (AHA):
Somehow the full name just made the flag too crowded so I settled for Absolute Horizon.
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Made this vanguard-esque rocket carrying a 85-kg sputnik-ish thing to orbit. It is a bit of a tricky one to fly. Needs pretty decent gravity turn and the last stage is this silly solid booster stack with no guidance and 20-45 TWR - in order to get to orbit, it needs to point exactly prograde and be fired at apogee almost to the second. Still, it's just 23.4t and needs 2 nodes unlocked, I believe that is a score of 46.8? The real vanguard had only a few kg payload I believe, which could bring total weight down to historical ~10 tons. However, I thought it would kinda break the spirit of the challenge to send a structural part or something, so I took a lot more massive thing that beeps...
Oh and btw I hope procedural fuel tanks are ok? They are not strictly required by RO I believe...
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Finished the first part of RO/RSS recreation of what the constellation program lunar landing might have looked like. Some screenshots (most of the material is in raw video):
Currently sitting in orbit, testing power/lifesupport systems for a few days before TLI.
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12 hours ago, XpertKerbalKSP said:
Congratulations, mate! Also, thanks for putting so much time into this. It's more than I can ask for!
Cheers mate! Honestly this is something I have been wanting to do for a while, this challenge provided the push to just go and do it. So thank you for hosting the thread!
I am actually planning to do a followup mission imitating what the Constellation program lunar landing might look like - this time entirely in IVA/Map view (some external cosmetic shots). Possibly in video format. No promises though.
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17 hours ago, XpertKerbalKSP said:
AMAZING!
It takes a lot of skill to pull something off like that it RSS (You must have a rlly good computer too, mine crashes whenever I load big craft in RSS........).
Just to let you know, you need to post both of your entries in the same post
Thanks! Added the second part (Apollo 14). Finally managed to iron out the issues with the craft. Spent way too much time figuring out I had some earlier prototype versions of J-2 engines with ~15% lower thrust - I just couldn't get it to orbit reliably. How I managed to do that on the Apollo 4 I will never know... Anyway, after swapping to the correct engines it was easy enough to fly.
I think RSS has a bit of a reputation but it's not that much more difficult than Kerbol. The Saturn V I used which was mostly constructed out of ready RO parts had enormous margins. Almost every stage had 200-500 m/s leftover delta-v. I can share the craft file if there is interest - just beware it needs a ton of mods. I think module manager reported 15k patches.
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I don't think I have ever done a proper lunar orbit rendezvous mission profile with either the Mun or Moon. Always used direct ascent. So I thought, why not do the real thing?
Here's the first part, RO/RSS recreation of Apollo 4. I always simulate/test my more complicated rockets with a mission that doesn't do anything that requires too much effort (like planning manouvers) and see if the staging and systems work. Apollo 4 seemed like the perfect mission to imitate and test my approximation of Saturn V.
I will try to recreate Apollo 14 once I work out some issues with the craft, mainly related to how the lunar module is housed and how it tends to go all wibbily wobbly in time warp.
EDIT:
And here's the promised Apollo 14! Direct link.
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Probably not a winning entry, but decided to tweak one of my heavy SSTO lifters for this challenge (master level). It's a 8 rapier 4 nuke closed drone. It has enough oomph to lift 36t orange tank to geostationary, mun or minmus orbit. It also has a solar panel, 3 docking ports, 8 RCS ports, and many control surfaces, so one could easily get the part count down some.
Weight: 122,015 t + 36,22 t payload for a total of 158,235 t.
Parts: 62 + 3 payload for a total of 65.
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My latest Tylo landing was a bit more tight than I liked. The lander was a 6.8-ton external seat lander with full science, and just barely enough delta-v to make it if the landing was close to optimal. Descent went fine, but ascent was a horrible mess. First the ascent stage had a slight centre of mass issue, making the thing a nightmare to keep on course. Second I had to launch on a slightly inclined orbit to make rendezvous. Ended up running out of fuel 3/4th the way up. Went EVA, picked up the science and finished circularizing with the jetpack. I think I had ~5% EVA fuel left after succesfully grabbing on to the mothership.
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We shall see, the pace of my journey did grind to almost a halt in the Jool system. Mainly related to the ion tug not having enough power and therefore TWR to perform necessary manouvers while in a moons SOI. It has the delta-v, I just underestimated the TWR needs of transfer manouvers, only considering them for landings.I would say "let the space race begin!" but I only have time for 2 landings a week, so it is likely you will finish first.I should have enough delta-v even if I use the MS to perform the insertions at Laythe, Vall and Tylo. So far I have landed and returned from Laythe and Tylo, sitting at low Tylo orbit. The far lander is parked in low Vall orbit with not enough fuel to land. I discovered it could not survive Laythe aerocapture, so I separated it and redirected it to Vall. I need to refuel it with the MS, land on Vall, then continue to the smaller moons as planned. Most of the time I am at altitudes below 20km, so no time warp. Couple that with 0.01-0.1 TWR, and it takes a looooong time to perform manouvers.
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Whoa, that small lander can really return from Eve? I'm impressed!
Spent the better part of a day trying to get the weight down on a working Eve return lander. Someone managed to get it down to ~33 tons but I couldn't replicate his results, so I settled for a 40-ton lander I knew I could reliably get to orbit.
Cool!I want to do a grand tour some time
I thoroughly recommend one. Once you have all the basics down (transfers, rendezvous, constant altitude landing, gravity assists, aerocapture) it's just a matter of combining the techniques to achieve an efficient enough mission. It's actually not that hard. I haven't completed one though (currently in Joolian system), so take this with a pinch of salt.
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With current configuration most do need to dock with either the ion tug or the mothership, but you are both right. Redesigning to get rid of most RCS would probably be better.Do you really need to re-dock these craft? You can have a Kerbal EVA, grab the science from the capsule and take it to the mothership, discarding the lander then. -
So this is my last nod to Tsiolkovsky, a final great mission of the old style where you bring everything you need with you. The goal is to land on every landable body in the Kerbol system, no refueling, no ISRU. 1.0 brings new challenges by nerfing most engines across the board, bringing aero heating etc. Still, should be doable just fine with a bit of planning.
KSP version is 1.0.4. Mods used are transfer window planner and kerbal engineer redux. Parts, aero, etc. are all stock.
The mothership has room for 5 kerbals with a comfy pressurised cabin. All the landers have stock science gizmos with them. Although this is a sandbox game, I'll be doing the science experiments just to demonstrate. You can find the landers at another thread. The mothership weighs 518 tons in orbit and has ludicrous amounts of delta-v which is a bit hard to calculate exactly, because parts of the payload get dropped along the way. I'd guesstimate about 20km/s.
First half of the journey is completed, visiting Mun, Minmus, Eve, Moho, Gilly, Duna and Ike:
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Actually, a single solar panel at Moho will generate 100-125 energy per tick, depending on the phase of Moho's elliptical orbit. Should actually slap some more engines in there, the TWR is too low for comfort.
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Good luck man! I love how the mothership really looks like it is designed for heavy aerobraking with the custom fairing heatshield. The way my mothership was built aerobraking at Eve was a nightmare. It took hundreds of passes to bring apoapsis down, and the initial aerocapture was not possible, had to burn some fuel. Your design should have easier time I reckon.
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Thanks! I know sitting in an external seat for years is indeed kinda fishy. Actually, sitting in a tiny single seat pod would probably not be much better, realistically. I might redesign the Moho part at some point, since it happens early in the trip it might be reasonable to bring a dedicated lander, instead of slapping more fuel and engines on the sides of the tug.
The RCS tug is a great idea too. The reason the reusable landers have RCS is some landings actually need them for that little bit of extra TWR and delta-v to make landings on Moho/Vall/Mun even possible. I did the Moho landing, TWR was 1.00-1.02 with the ions, the RCS brought it up to ~1.1, which made the landing possible. I reckon redesigning most of the landers so they don't need RCS and to have a separate RCS tug would probably make total mass a little lower and be more convenient.
Regarding the Jool-5, does it matter if the interplanetary transfer in a seat does not actually involve any part of a normal Jool-5 mission?
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Doing a grand tour. So far visited Mun, Minmus, Eve, Moho, Gilly, Duna and Ike. Currently sitting in low Duna orbit, preparing to transfer to Jool.
Maximum Delta-V rocket
in KSP1 Discussion
Posted
Yeah I think my initial assumption that maximizing delta-v to mass ratio for each stage does not get optimum total delta-v. I reckon truly optimal staging would be 1 engine, fed by drop tanks arranged in an asparagus-esque pattern, with somehow optimizing tank weight vs decoulper weight. So potentially having a decoupler for each tank and thousands of stages. Like someone pointed out, theoretically even better would be to have a single kerbal detatch each fuel tank manually with KIS/KAS, so every single fuel tank could be jettisoned when empty with no decoupler mass cost.