

iHateLadders
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Bottle Rocketeer
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Has .90 buffed planes or did I just accidentally design my best stock parts SSTO and fly it into orbit without trying by pure luck? Seriously, this thing is loaded down with science parts and not at all designed for getting to 200km AP/46km PE while I'm not even paying attention. I've spent ages trying to build the optimal SSTO with stock or FAR/pWings in older versions and I've only had one success like this after many hours of testing and tweaking. Has anyone else noticed how easy this is compared to previous versions? Also, I lied about the cake. Not sorry.
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Ya, I have a ton of ASAS on the center of the wheel. It certainly improves my base efficiency tests. However, I have found that after an initial increase in rotation, it drops off almost entirely. So what I do is begin with using ASAS and then switch over to ion torque. The washer I use is part of infernal robotics. I don't know if it implements friction or if some other game mechanic is effectively doing it but I have found that ASAS seems limited. Maybe I just need moar ASAS. Either way, you are correct. All my base tests can be improved by ASAS. Does this apply to a set up where the fuel is not stored on the thing being moved? What I mean is, I have xenon on the base of my Kerbal AcceleratorTM that does not not add to the mass of anything rotating on the arm. This works because Xenon has Flow Mode = Everywhere, like electric charge. So while my first test had a mass of one kerbal + the arm being rotated, the total xenon available was like 15,000 units and nothing stopped it from being 150,000 units except for fps drop due to part count. Either way though, that is an awesome graph.
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Really appreciate all the help, guys. The effective Isp now makes more sense. It was the change in mass part of the equation that confused me because I was only counting the poor kerbal and not the fuel used. With that formula, I've been able to ...formulate the range of dimensions where this contraption is more or less efficient at putting things in the orbit. Small things only require a small amount of thrust so using this huge rotational arm and spending a whole lot of time getting it up to speed isn't optimal. However, I've found large objects do much better. The following is a second test: leaver arm = 45 m additional length to CoM of vessel connected to end of leaver arm = 8 m rotational frequency at launch(measured) = 73/60 Hz velocity(calculated) = cf = r*2pi*f = (45 + 8) *2pi *73/60 = 405 m/s xenon units spent = 2100 units vessel mass = 12 t The effective Isp of this test was given by dangerous beans(thank you sir) as Isp = 405 /(9.81*ln(12.21/12)) = 2380s And the comparison to the dV of the ideal case is given by yasmy and streetwind(again, thanks guys) as dV = 4200 * 9.82 * ln(12 / 12.21) = 715 m/s The notable gain here is from the fact that even for larger payloads, the rotation does eventually get up to about the same frequency as for lighter loads. So it seems that there is a sweet spot of using rotational arms of mass and torque proportional to the payload mass. I'll have to fiddle with R or matlab to see if I can find what that precise optimal solution is. The one thing that I'd like to also calculate is how much dV from the ideal case is lost to idling, working against gravity by thrusting normal to the surface rather than horizontal. Whats tripping me up is the range of TWR I could choose from for this hypothetical vessel. I still think there may be some range of vessels where it is more expensive to launch them normally, I need to figure out what that range is.
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I don't see much agreement between topics on Isp in KSP. The equations often don't even agree on the dimensions of the value. So, here goes another thread on the subject. I have a contraption which places a balanced rotating horizontal beam on top a free spinning washer just off the ground. It gets torque from ion engines near the end points. It has connection points at the end points which can release objects(kerbals or vehicles). I'm trying to determine its fuel use efficiency as a function of its rotational frequency(which increases with diminishing returns as it picks up speed even in vacuum planets). The goal is to find out when it becomes too costly to keep building up additional rotational speed relative to other solutions. I have run the following test with Bill. The test was to strap him to an external seat and launch him into mun orbit and definitely not into the ground. The results: leaver arm = 45 m rotational frequency at launch(measured) = 5/4 Hz velocity(calculated) = cf = r*2pi*f = 45 *2pi *5/4 = 350 m/s xenon units spent = 900 units and lastly, he did survive. He had to use about 2.4 units of his personal fuel to get orbital after his initial launch. Yay Bill! You live to see another experiment. So, what I'd like to find is the effective Isp of this set up or alternatively I'd like to be able to solve for the deltaV of a simple ion vessel spending equal amounts of xenon(900 units), supposing the vessel was idealized to just the ion engine, 4 6x1 solar arrays, a kerbal, a seat, and 3 xenon tanks for a total mass of .7 t. I appreciate any help with explaining how to solve the two questions above. Ideally, if I could understand the Isp equations, I could determine how to optimize this solution. Some obvious questions concern increasing the radius or adding more torque. The limiting factor on torque is rotational frequency because a single revolution must be slow enough for human reflexes to aim the release in the right direction. The initial purpose of this 'accelerator' was to overcome TWR issues by building up speed perpendicular to the pull of gravity while relying on the device to maintain elevation until release. This permitted less idle time for ships fighting gravity while also trying to speed up. I'm trying to figure out what ranges of different variables make this solution more viable.