Astroturf

( @K^2 , reason for not producing your results ) I have terrible version control and I wrecked one of my models. I'll have to get back to this later, sadly. I'll try to use a more systematic approach (I'm not an engineer! ) I remember that. this might be useful if it turns out that a multistage approach may be better (eddies caused due to sudden change in diameter, ie, the exhaust makes it unaerodynamic) well, a) it's no fun if it exists already, and b) the intent with this is that you could hypothetically make an infinitely long rocket, maybe even bootstrap a space elevator by having a bazillion stages that fire simultaneously. unless I'm misunderstanding you. could you provide a drawing on how to attach the lower stages to your breathing shroud?

a lot of good feedback, thanks guys i'll get back later to it but for y'alls (and my) references here's a lavalish (eyeballed geometry) nozzle with ~3km/s output (6km/s in chamber) @ 2200K animated: https://gfycat.com/SnappyPortlyDegus now this kinda shows you how a dyson fan/vacuum works! breddy cool if I dare say so myself. sorry for potato quality but I'm still new to this stuff. bottom boundary surface with engine on: Local Parameter Minimum Maximum Average Bulk Average Surface Area [m^2] Pressure [Pa] 100281,2453 101497,2783 101321,0811 101270,2163 655,7328423 Density (Fluid) [kg/m^3] 0,074390084 1,205116759 1,160990033 0,554836263 655,7328423 Velocity [m/s] 0 1414,377315 22,15909103 449,8063345 655,7328423 Velocity (X) [m/s] -19,37759152 26,30267251 -0,060125633 -1,216657183 655,7328423 Velocity (Y) [m/s] -1414,12439 4,627844849 -19,86051311 -447,9727883 655,7328423 Velocity (Z) [m/s] -27,89804162 31,35409891 -0,019769064 0,440334467 655,7328423 Mach Number [ ] 0 1,155443032 0,024356665 0,418744205 655,7328423 Temperature (Fluid) [K] 293,1999933 4695,396954 369,594359 1831,531807 655,7328423 Relative Pressure [Pa] -1043,754687 172,2782917 -3,918892942 -54,7836935 655,7328423 Integral Parameter Value X-component Y-component Z-component Surface Area [m^2] Mass Flow Rate [kg/s] -969,4566667 655,7328423 Volume Flow Rate [m^3/s] -12895,09482 655,7328423 Surface Area [m^2] 655,7328423 -5,15261E-14 655,7328423 -4,26089E-16 655,7328423 Total Enthalpy Rate [W] -8459255428 655,7328423 Uniformity Index [ ] 0,094985986 655,7328423 Area (Fluid) [m^2] 655,9346166 655,9346166 bottom boundary with engine off: Local Parameter Minimum Maximum Average Bulk Average Surface Area [m^2] Pressure [Pa] 101325 101325 101325 101325 655,7328423 Density (Fluid) [kg/m^3] 0,609022284 1,203010699 1,179019768 0,92837813 655,7328423 Velocity [m/s] 0 0,017849372 0,00041043 0,006948162 655,7328423 Velocity (X) [m/s] -0,00051274 0,000203903 -3,94771E-06 -8,27855E-05 655,7328423 Velocity (Y) [m/s] -0,01784011 6,24284E-05 -0,00034236 -0,006933303 655,7328423 Velocity (Z) [m/s] -0,000338888 0,000133815 -2,05226E-06 -3,11429E-05 655,7328423 Mach Number [ ] 0 3,72843E-05 1,01455E-06 1,57724E-05 655,7328423 Temperature (Fluid) [K] 293,2 579,49684 300,0733601 403,0617121 655,7328423 Relative Pressure [Pa] -2,35741E-09 8,0734E-08 -6,43164E-10 -1,44566E-10 655,7328423 Integral Parameter Value X-component Y-component Z-component Surface Area [m^2] Mass Flow Rate [kg/s] -0,182005847 655,7328423 Volume Flow Rate [m^3/s] -0,224813941 655,7328423 Surface Area [m^2] 655,7328423 -5,15261E-14 655,7328423 -4,26089E-16 655,7328423 Total Enthalpy Rate [W] -80684,23777 655,7328423 Uniformity Index [ ] 0,204215928 655,7328423 Area (Fluid) [m^2] 655,9346166 655,9346166 ----- Now question about methodology: to calculate efficiency of the rocket, I would multiply Mass Flow Rate [kg/s] * average Velocity (Y) [m/s] to get a force in Newtons. I'll divide the value from the other nozzle by the laval nozzle value to get an efficiency factor. does that sound sound? -19.86051311 kg/s *-969.4566667 m/s ≈ 1.1 × estimated force of a bite from a great white shark (Carcharodon carcharias) (≈ 18 kN ) (19.2539068 kilonewtons) no it's not. I'll try and see if I can get an integral of air momentum or something. ----- couldn't find it, went ahead and remodeled the thing anyways with #realistic boundry conditions. initially, the solver failed so I ramped up the mesh resolution. Initially I assumed that the eddies at the edge were just artifacts because of sharp corners in the boundry. But aaa... ... IDK what is going on. these actually gigantic torrents are taking up a huge chunk of the airflow, and everything is just messed up. But I'm glad the exhaust sticks to the body. Buuuut, that doesn't mean a whole lot: @Steel you might find this one interesting: (these last two were done under the exact identical conditions.) It almost looks like the airflow here is better... sigh... this is hard... And I should work on my actual thesis which has absolutely nothing to do with this :V

Yes and no! With internal reflection (similar to an x-ray telescope) and the interaction with the outside atmosphere, the hope is that there isn't actually that much efficiency lost. look at the 2d pic: while initially it looks like half of the propellant is going straight out, it surely enough is redirected downward, and some of it even back towards the rocket! Yes, you could say the rocket is fired while the stage is still attached. But if the stage decoupler handled the rocket exhaust like this, it wouldn't be that big of a deal!

I think I mentioned this back in 2013, but there wasn't much science behind the concept. Basically I propose an inline rocket engine (nozzle). It's an upside-down inline aerospike (only noticed that after functionally modeling it) that let's you stack tanks or other engines directly behind it. Back in the day IIRC we didn't have radial thrusters yet, so I realize that three years later the utility is a little lost, BUT, I still think it's interesting that it may actually work, and may potentially be used to reduce surface drag. In any case, it would have helped with regular staging in lieu of the abominable asparagus staging that is so common nowadays. This idea was motivated by the concept of aerodynamic skin effects (IDK what they're actually called, I'm just a pretend engineer) Well anyways, let me share with you my findings, and you can let me know what y'all think: the nozzle: now to validate this thing a little I ran a couple sims. here's a 2d prototype: and here's the thing in 3d. although I think the 2d cross section is more useful. The boundry conditions here are all the walls at 1atm pressure, and the spigots in the engine shovel 1kg/s of air through the engine. Color is temperature. Now in the 2d pic we almost see an airstream that stays under sqrt(x). that would mean that the efficiency on these things (given the right geometry) could be really good! What I really didn't expect to find was this low pressure area/hourglass air density around the nozzle. that surprised me, but it's possible that I set up the boundaries wrong. (not a real scientist). So I was wondering if y'all had any opinions on the concept, or if someone was willing to independently verify this. you think this type of engine would be a nice addon for ksp? PS: a name for this thing would also be nice, if it doesn't already exist.