GoSlash27

"B" would be clearly more efficient every time. On an airless body, an orbit is merely falling around the body so quickly that you miss it. Since you have no atmosphere, there are no drag losses. There are only gravity losses. Therefore your most efficient solution is to burn horizontal with only enough vertical component to equalize gravity until your centrifugal force is equal to the centripedal force of gravity. Best, -Slashy

Pecan, The issue I see is that you are "a) wrong in your definition". It doesn't matter what a vehicle does after achieving orbit in order to qualify as an "SSTO". It merely has to achieve orbit without dropping parts. It could de-orbit, remain in orbit, or leave the system entirely. It's still an SSTO by definition. Best, -Slashy

I think you inadvertently answered your own question; there's nowhere you can go that makes the prograde burn worth it. If you're just trying to escape SOI or make a small orbit change, then it's pretty obvious that buying into the Oberth effect isn't worth the DV investment. But if you're going somewhere, then it's in your interest in the long run to do that retrograde burn. Best, -Slashy

Unless I'm mistaken, the OP said he was using stock aerodynamics. If that's not the case, please disregard everything I've said here. My advice only applies to stock aero. Best, -Slashy

I disagree. I have made all sorts of different kinds of SSTOs (and I refer to them as such) that execute all manner of missions once they've achieved orbit. Some of them are spaceplanes, some vertical lifters. Some fully reusable, some not. Heck, one of 'em doesn't use any fuel at all! If it gets to orbit without dropping any parts, it's an SSTO. Cheers, -Slashy

It achieved stable orbit without dropping any parts. Whatever else it may or may not be, it *is* an SSTO. Best, -Slashy

I have no idea what the "J parts" are, so the following might not be terribly helpful... 300-600 m/sec at 20KM up *is* a bit pokey. I can see how your controls would be railed nose- up trying to hold the attitude, then overwhelmed when you suddenly change the setting. You might try a shallower profile above 15KM and see if the extra airflow over your control surfaces and wings helps add stability. A good generic climbout profile would be as follows: 45* pitch to 10KM, 30* pitch to 15KM, 20*pitch to 20KM, then 10* pitch thereafter. You state that your fuel tanks are reasonably centered and from what I can see I have no reason to doubt you. Everything looks pretty well balanced to me. I think if you just fly it a little faster your problem will resolve itself. Good luck! -Slashy

Not that this is an invalid argument, but it *is* a minor point of contention which has no bearing on this discussion. An SSTO doesn't have to perform any act whatsoever in order to count as an SSTO other than 1) achieve orbit and 2) not drop any parts on the way. It matters not a whit what individuals choose to do with them once they're up there (at least from an engineering standpoint). This particular discussion is simply about intakes for jet/hybrid SSTOs. Best, -Slashy

"Should" is a subjective word. That statement is true for anyone who uses SSTOs to put payloads in orbit without regard to any other consideration, but is false for everyone else. Any SSTO *I* use will not only need to deorbit, but also match inclination, intercept, rendezvous, and dock with something else while in orbit. It's also a plus if it has some fuel reserve to land under power. Others often use SSTOs as an interplanetary vehicle. I don't personally, but for those that do the DV is pretty critical. Having said that, what people use SSTOs for *after* they're in orbit is immaterial. What matters is how we go about getting our SSTO into orbit with minimal fuel, expense, and unnecessary mass. Best, -Slashy

Something to keep in mind is that the intakes are not only a source of additional drag in this regime, but are the *primary* source of drag. This is why adding intakes quickly becomes detrimental; You get a small increase in thrust with a huge penalty in drag. Best, -Slashy

I'd like to have a definitive answer on that also. I got my numbers from the config files for the parts, but I can't be certain I got the *correct* parts because I have duplication of parts due to the patch and I'm not 100% certain which is the latest 'n' greatest. Best, -Slashy

Something I'm trying to puzzle out now that's worth sharing: https://github.com/numerobis/KSP-scripts/blob/master/jets.py#L122 You mean intake area? My info shows the intake volume to be equal. My info also shows the intake area of the XM-G50 as .04 rather than .06. But my point is that they actually conducted that test, and the structural intakes still lagged behind the others despite the massive cumulative intake volume. So that clearly can't be the overriding factor. The best performers had high volume and the worst performer also had high volume. Puzzling... Rank/Type/ area-mass ratio/ area / mass / capacity 1 XM-G50(2) .320 .008 .025 1/2 2 Shock Cone .440 .012 .027 .4/.8 3 ram air 1.00 .010 .01 .2/.2 4 Circular .727 .008 .011 .2/.2 5 Structural(2) .238 .005 .022 1/2 Best, -Slashy

I would've thought so as well, but then the structural intakes perform relatively poorly in the same tests, and have the same intake volume. Even equalizing the intake area between them and the XM-G50 isn't enough to put them on equal footing. There's something odd going on that the math doesn't readily suggest... Best, -Slashy

LordFjord, This is the million dollar question, and I don't think anyone has gotten it pinned down yet. Here is a test that shows there are differences, though exactly *why* remains a mystery. http://forum.kerbalspaceprogram.com/threads/97615-0-25-KSP-air-intakes-compared I haven't found any correlation between the specs in the config files and the results of this test. And yes, the idea that the XM-G50 "stops working at high altitudes" is indeed an old wives' tale. Finally, keep in mind that the most efficient SSTO designs will rely on using as little o2 and rocket as possible, which means achieving or even exceeding orbital velocity on jet thrust alone. It's not enough to just hit 32KM up and then make up the rest with rockets. That will get you there, but your resultant SSTO will wind up larger and heavier. Thanks for starting this thread. I'll be keeping an eye on it! -Slashy

An example I just knocked together to illustrate: This one just transfers 4 kerbals to LKO with a 2 kerbal flight crew and a docking port. It's close enough to perfectly balanced that no control surfaces are necessary. It uses just 80 KG of fuel and 35 KG of oxidizer to do the job with plenty of DV for rendezvous and docking and a powered landing back at KSP. Best, -Slashy

I've been researching this subject this week. Looks to me like the optimal number/ type of intakes is 4 of the XM-G50s per engine. Any more than that, and the gains from air are erased by the drag losses. Put 'em as far aft as you can. One engine per 13 tons of spaceplane and roughly 1.0 of lift coefficient per ton of spaceplane. Porkjet strakes are the best wings to use. This is all a rough preliminary estimate and is therefore subject to change. Best, -Slashy

There's a point where the performance will plateau. The additional intake area stops providing additional performance, while the additional mass and drag hinders you. After sorting out how much intake area you need, you want to look at how much mass and drag each intake type is costing you per square meter of intake area. Those little structural intakes are pretty darn good! Best, -Slashy

Question #1) I have absolutely no experience with mods, so I have no idea what you're referring to when you talk about "cranes". Assembly in orbit in the stock game is really just a matter of intercept/ rendezvous/ dock. Lots of videos to explain how we do it, and this one helped me out tremendously early- on: https://www.youtube.com/watch?v=5ciFCKgyx48 2) Landing on each body is a unique process. Most do not have atmospheres, so it's a retroburn. Your lander needs to be able to achieve 1G local (check the wiki) when full and the process is fairly straightforward: Keep your nose pointed retrograde and follow a rule of 10s similar to docking. As you get close to landing, it's easy to get disoriented when killing your lateral speed. The way I do that is to start the deorbit burn inverted and backwards. By the time I'm slowed to a near- hover, I'm viewing the lander from behind so control responses are where I expect them to be. I'm sure there are good tutorials out there on retroburn landings, but I've never seen one. You're on the right track so far. Success in this game will require 1) an ability to rendezvous and dock in orbit, 2) an ability to pull off a retroburn landing, and 3) an ability to land close to a desired point. And of course 4) being able to design the entire mission within the delta v budget before launch. Good luck! -Slashy

My first smartphone was a Galaxy S3, and I was thoroughly impressed. The big thing to watch out for now is updates. The S3 is nearing the end of it's service and probably won't get the OS upgrades of the newer phones. Other than that, the S3 is a well- designed and constructed phone. Removable back, replaceable/ upgradeable battery, upgradeable memory, and very intuitive user interface. Best, -Slashy

Honestly... nerfing the RAPIER has helped, but in my experience the combination of turbojets and 48-7S still yields a larger payload fraction overall. While the RAPIER would seem to provide lower engine mass and simplified construction over a hybrid system, in practice it's performance hit requires more fuel and structure to do the same job. It's closer than it was, but not quite there yet. Best, -Slashy

Yes, it's a necro, but I grew really fascinated by this subject this weekend. What is "mystery goo"?? It will escape if opened in water. It will gravitate towards water if exposed near it. It hates the desert. It's very comfortable in space. Is it alive?

DO'H!! That deep-sixes my expedition. That's what I get for not paying attention...

http://i52.photobucket.com/albums/g13/GoSlash27/KSP/KerbiLab/KerbiLab2_zpsa90a556b.jpg And we're on our way. http://i52.photobucket.com/albums/g13/GoSlash27/KSP/KerbiLab/KerbiLab3_zpsad7ae1b7.jpg Collecting science in the Kimilaya highlands. All science collected for each biome includes EVA report, goo observation, temperature, pressure, seismology, and gravioli detection. http://i52.photobucket.com/albums/g13/GoSlash27/KSP/KerbiLab/KerbiLab4_zps5cd4b242.jpg Frodos and Obbert collecting science in the Kimilaya mountains. And fervently hoping they don't get devoured by a Bambatta fuzzbeest in the process. Daylight's running low, so they'll camp out here tonight. Day one, 2/6 biomes monitored.

I think we've got enough bugs worked out to give this a go. Our flight crew is (l-r) Science Technician 1st class Obbert Kerman, Chief Science Officer Frodos Kerman, Mission Pilot Burfrid Kerman, and Mission Commander Hadoly Kerman. They will hopefully be able to acquire science from six unique biomes on a single mission using the KerbiLab and it's dedicated rover "Beagle 1". Wish me luck! -Slashy