herbal space program

It of course all depends on how many tons per engine you're trying to push, but if you're towards the high end, you definitely need to speed up to ~300m/s right off the runway at a very low climb angle, and then pitch up but never so much you go below maybe 280m/s. Doing that made all the difference for me.

That's what I was thinking of doing, or rather I was thinking of trying to use Laythe as a pre-braking step to lower the speed at which I'm coming into Jool's atmosphere. I thought maybe that if I could drop my speed to the point where I'm close to getting captured by Jool, I would just barely need to touch Jool's atmosphere to finish the job, and wouldn't have to come in nearly as fast.

Looks like you're on your way! My progress unfortunately got interrupted by the demands of real life, but I'm going to go back to trying now. I got rid of those bicouplers and it really helped. With a 4-engine, 60.5 ton ship I'm getting on orbit no with right around 5km/s dV in fuel now plus 250 units of oxidizer. I think I can probably improve that by adding just a bit more wing area, but the returns of hauling more fuel to LKO are starting to diminish as its own weight starts to exceed 20t. Those air brakes you have have gotten me thinking too. They might come in handy if I ever want to use Jool's atmosphere to slow down. Word on the street seems to be that aerobraking at Jool is pretty broken.

Oy. I guess I'm going to have to consider this for my supposed Laythe-and-back SSTO mission....

Thanks, I'll give that a try. It would also generate some lift where I need it, so I could drop some wing area. - - - Updated - - - Thanks for the tip. I think that what RIC suggested would be better than just making the whole outriggers MK2, because those MK1 fuselages now have a really good ratio of mass/drag. Perhaps I'll try it both ways...

Well, based on all that, It seems like I must have a drag monster on my hands. I'm at 14.75t/RAPIER, and while the high end looks fine, breaking Mach 1 has gets too time-consuming if I go above that ratio. Adding the shock cones to the backs of the engines did make a pretty noticeable difference though. Before I did that I couldn't manage more than 12.5t/RAPIER. Now I'm getting on orbit with 30.76% of takeoff weight in fuel, for about 4700 dV, 5100 theoretically if I convert my oxidizer to LF. I'm getting a total PF on orbit of 34%, which is not bad based on RIC's PF challenge thread but can clearly be improved upon. http://imgur.com/d7qFRLo

Thanks! That has exactly the information I was looking for.

Hmm..... Smells a bit of trickery to me, but I guess I'll have to try it now!

Hello all, I am working hard on making the most efficient SSTO I can, and of course minimizing drag is a key consideration in doing this. My problem is that I don't have a clear understanding at all of exactly how drag is modeled in 1.0.3/4, and I can't seem to find a good explanation of it sitting around anywhere. For example, are all wings alike in terms of lift vs. drag? Are wide wings draggier than narrow ones, as they would be IRL, or does it not matter? For non-wing parts, is the key consideration just cross section wrt oncoming air, or does the shape matter? If anyone has a link to a basic discussion of this, I would really appreciate it, because I'm basically in the dark about how to improve my design's aerodynamic performance right now. Thanks!

Sorry for the misunderstanding. I replied as I did because the actual TWR bottleneck in 1.0.3 is at the bottom of your flight profile not the top, so you definitely don't need more engines at the top vs. 1.0.2. Based on what you said, I'd say what you need is more intakes and not more engines, because 25km is too low to be switching over. My best current plane is 50.2t runway weight with 4 RAPIERs (i.e. 12.5t/engine) and a nuke. I think based on what RIC posted I could actually go somewhat higher, to maybe 15t/engine. The best ascent profile I have been able to come up with for that goes something like this: Hug the ground after takeoff for 15-20 seconds, building speed to >200 m/s, then pull the nose up to ~25-30 degrees, for a low atmosphere climb rate of ~80-100m/s. I maintain this attitude until ~12km, then pitch down to 5-10 degrees to go transonic. Once my speed gets to >425m/s, I pitch back up to maybe 20 degrees, until I get back to a climb rate around 100m/s, usually around 14-15km. I then put my nose right in the middle of the prograde marker and burn until I hit my maximum air-breathing speed, around 1450-1460 m/s at around 21km. I then pitch up to around 20 degrees again, letting my velocity drift down to around 1400 m/s at 25km. At that point I engage my nuke engine for a little extra thrust. Holding in that attitude I can typically get to 29-30km on air, with right around 1300m/s velocity and maybe 175m/s of climb at switchover. I then burn rockets at 20-35 degrees pitch until I get to maybe 33km, then nose back down to 5-10 degrees and try to get to >1900 m/s before cutting the RAPIERs. If I do everything right, that gets me to an apoapsis of around 60km, which I try to circularize with the nuke such that my apopapsis reaches 70km just before my periapsis does. If I convert the oxidizer I schlep to orbit into fuel, a good ascent following that profile would theoretically get my ship on orbit with around 4500dV remaining. RIC just recently managed 5000, so clearly there is still room for improvement from that.

Wow, that's a lot of dV on orbit! With 5 km/s, I think you could do it going straight there, although the ejection burn with that one nuke is not going to be very efficient. One useful thing about doing the multi-assist route for a plane like this is that you can do a much smaller initial ejection burn. It was looking to cost me about 1400 dV to get to Jool that way, which is only a 600 m/s savings over a direct route nominally, but I suspect that with that long last burn a direct route will cost significantly more than 2km/s. It will be interesting to see how cheaply you can pull it off. I also note that you have no oxidizer left. Do you think you can make Laythe orbit again without burning the RAPIERs at all in rocket mode, or do you intend to trade off some dV for oxidizer in the final version? I've always assumed I needed to be shipping at least a couple hundred units of oxidizer on LKO for that purpose.

FWIW, after claiming haughtily that the new aero nerfs rather than improves SSTO performance, I was humiliatingly shown a 1.0.4 SSTO plane with a higher payload fraction on LKO than anything I was able to make in 1.0.2. Going back to the drawing board, I found that hugging the ground for the first 20 seconds of so after takeoff and before pulling up made all of the difference. In 1.0.2, my takeoff speed was such that I could just pull up to 30 deg right off the runway and motor into the sky with 4 RAPIERS pushing 47t. Now that's just a no-go, and what would really work best is another km or two of runway to gain speed on the ground with those wimpy engines, but grazing the water for half a minute before pulling up seems to do the trick well enough. You just want to get your speed north of 200m/sec before particularly pointing your ship towards space. You also want to do your flaming hyper-thrust transonic acceleration lower down than before, at maybe 17km instead of 19.With those two changes and some moar wings I was also able to get to a better deltaV on LKO than I could in 1.0.2. - - - Updated - - - Moar wings and less climbing right after takeoff is what you need.

I voted "the game is finally perfect" because I'll say ANYTHING to keep them from changing the aero model yet again!

I thought maybe with the Mk2 parts even if it wasn't a space plane you could pull that trick, but if you don't have enough control authority to pitch up against the aerodynamic forces I guess there really is nothing you can do. I feel your pain. I had a fleet of 4 SSTOs in the middle of a Laythe-and-back mission that involved four consecutive gravity assists, and they all turned into pumpkins right before the final one. I can't begin to estimate how many hours went down the drain there.

My first impression of this new air is that it was terrible, but after learning how to build and fly planes for the fourth time, it's looking quite a bit better to me. The "rebalanced" RAPIER engines now require quite a bit of nursing at low speeds and altitudes, and the lowered jet ISPs mean you really can't waste any time at all getting up there. But if you learn how to deal with all of that, the better high-end performance seems to more than offset the low-end nerfing. Anyway, I hope this is the last major overhaul of the aero system for a good while. Starting from scratch over and over again is getting rather tiresome, and I would really like to start flying my planes someplace besides to LKO over and over and over again soon. - - - Updated - - - I found that when I was de-orbiting a MK2 plane at Kerbin in 1.0.2, pitching up hard as soon as the atmosphere starts to bite would allow me to skip like a stone across the top of it, losing lots of speed without heating very much. I could re-enter from LKO without even generating any flames. And going up to orbit in with an SSTO 1.0.4, it seems like my problems with heating are now significantly less and not more. Do you have no choice but to come in very steeply?

That was crunchy! You were right. This plane weighs 50 tons on the runway and has 4 RAPIER and 1 nuke engines. The trick for me was to build speed for maybe 15 seconds right above the ground before really pulling up at all. If I did that, then I could get the engines to the point that they would sustain a quite reasonable rate of climb without losing too much fuel. It almost seems like there's some sort of ground effect with acceleration, but maybe it's just that it's critical not to lose any of your takeoff speed with this weaker low-end thrust. In 1.0.2, I was able to power straight up to 12km in short order, but my takeoff speed was >200m/s. It's much lower in 1.0.4, so now how I fly it in the lower atmosphere matters. I also stuck a few more canards on it. I was interpreting my low speeds on the runway as too much wing drag, which is why I thought I couldn't slap any more wings on. It was actually just about the weak thrust. With that one change, I was able to go back to having 270+ m/s speed and >50 m/s ROC at 12km, which allowed me to go transonic quickly and with hardly any altitude loss. It seems like best altitude for the flaming fury phase is a good 2km lower in this version too, maybe around 17km. This plane made it to orbit with almost 30% of takeoff mass in propellants and just over 4000 dV, which is the best I've done on dV and close to the best on PF. Presumably I can do better with more practice in this new and improved-for-the-third-time air. Anyway, I'm sorry I scoffed, but I really did spend a lot of time trying to get back to what I could do in 1.02 without any success. Having to change everything over and over again is making me cranky.

Well completing missions is fun too. I guess I should have had my ear to the ground more before getting in so deep with what I was doing, but getting it all erased by this update was a real drag. So are they planning on doing this again in another month?

How many hours have you spent testing that pronouncement? I have put in a good 10-12 hours testing it for 1.0.3 at this point, and I conclude that payload fraction for space planes has most definitely NOT increased. Moreover AFAICT everybody on this forum who has actually spent a significant amount of time time trying it concurs. It makes no difference at all how well the new RAPIER engines work at the top of the envelope if they can't get up there in an efficient way in the first place. My 47 ton interplanetary plane used to sail right up to the transonic realm with 4 RAPIERs and a nuke, using very little fuel, and now no matter how I tweak the amount of wings and/or intakes, it struggles to climb to 12km sub-sonically. This significantly reduced thrust at the low end, combined with the HALVING of their ISP, has severely nerfed the PF of the RAPIER-only designs. In 1.0.2, I was able to get a PF on LKO of 32.5% overall, 30% in just fuel, with 4km/s deltaV remaining. If you show me a plane that can do that in 1.0.3 I'll eat my space helmet!

They really need to fix the placement of maneuver nodes in interplanetary space. Half the time I can't put a node anywhere between my ship and it's next SOI change. It typically takes me several minutes of very tedious clicking and dragging to get a node an hour in front of my ship if I'm on an interplanetary trajectory. I usually have to place it in my next SOI first, then wiggle and jiggle endlessly to get it to snap to the previous one. Very, very, very boring.

Twice now in as many months all of my space planes have become useless. Many hours of my precious free time have gone completely down the drain, meticulously designing planes that I can't fly now in the missions they were intended for. This is not fun! Please stop it Squad. Decide how the air will be modeled and then release it once and for all!

I don't know about that particular craft, but I was able to get to the Mun and back with an SSTO in 1.0.2 with fuel to spare. I'm not so sure I can do it in 1.0.3.

I'm actually pretty convinced that they're worse and not better. While the performance of both RAPIERs and TJs at the high end of the air-breathing envelope is indeed significantly improved, the lowered ISPs and weak thrust at the low end have more than canceled that out in my experience. I was getting on orbit in 1.0.2 with 30% payload fraction in just fuel, giving me a whopping 4km/s deltaV on orbit, and now the best I can do seems to be closer to 3km/s and a 24% PF. I am continuing to redesign my planes to try to get back to where I was, but right now it's not looking so good. - - - Updated - - - Seriously! I am getting pretty fed up with spending hours and hours designing space planes and then just having to throw them away! I was actually going to start a thread in the Suggestions sub-forum just to complain about this.

RIC: "Not well. I tried the 1km/s route to Jool a few times, but could never get the second gravity assist right. So I went back to refining my design, which got me to 4km/s of dV in orbit, which I thought might squeak out a return if I could catch an assist from Tylo on the way out from Jool, but now I think it won't get to orbit with that much dV. I may have to give up on the return. :/" Yes, I feel about the same. I was able to thread the pork chops reasonably well after a couple of very time-consuming false starts, and although I never actually went past the second Kerbin encounter, it looked like my best launch was going to get to a Jool encounter for around 1400 dV all told. Starting with around 4Km/s at LKO, which was the best I could do in 1.0.3 after countless ascents and re-tweaks, it seemed like I could just maybe pull it off. Unfortunately, 1.0.3 has now broken that space plane completely, and with a redesigned plane I can't seem to hit orbit with more than 3-3.5 km/s using just RAPIERs. They're just too weak (and thirsty too!) at low speeds for me to do the sort of rapid ascent profile that I've found key to conserving fuel. Last night I spent a fair bit of time trying with 2 RAPIERs plus 2 TJs, and that plane's initial ascent to transonic territory looked great, but it just poops out too soon at the high end. I'm losing a good 100 m/s of speed and 50 m/s of ascent rate at a 29km switchover altitude vs. all RAPIERs in 1.0.2. The ideal ratio of engines for this rig seems to me to be 3 RAPIERs, 1 TJ, and 1 nuke, but building that is not so easy. My patience for this endless exercise is statting to wear thin, but I think maybe tonight I'll try putting 1 TJ, 1 nuke, and 1 RAPIER canted outwards on a tri-coupler in the middle, with 2 more RAPIERs on the outside. The resulting plane is sure to look ugly and fly even worse, but I think it might be able to find the deltaV sweet spot that way. Maybe I'll try a honking Mk3 design with 2+2+6 as well. At least that one won't require placing engines crookedly...' ...So after spending another evening learning how to fly my plane again, it looks like I can actually get the same deltaV on LKO I could before or maybe even better. It took lots of changes to both the design and the ascent profile, but now it seems to work pretty well again This plane has >4km/s dV on orbit, so I guess I can try again with this Laythe thing now...

I guess I should clarify that when I say harder I mean less efficient. I am trying to make the longest-range SSTO I can, and while I have to admit I have only spent a couple of hours working on it so far, the best I have been able to until now is 24% fuel payload fraction on orbit. My previous model in 1.0.2, which could get 30% on a good climb, barely flies at all in 1.0.3. Adding wings and removing intakes, I've found that the RAPIER engine does seem to be able to go a bit higher than it could before on air, but its nerfy thrust at lower elevations and the lower ISP has my air-breathing climb sucking up substantially more fuel than it did before. Maybe I still just need to re-find the optimal lift-drag balance for 1.0.3, or else revisit shipping a TJ engine instead of just RAPIERs, but my experience so far has been somewhat discouraging.

.....D'OHHHHH!! The new aero regime in 1.0.3 completely broke my Leythe-and-back space plane. It's basically a brick now. They were half way there, rounding Kerbin for the first time, and now I have to start over. I suppose I could revert my version to finish the job, but what's the point if that's not reality anymore? And since the change I haven't been able to get to orbit with nearly as much PF in fuel as I could before. Maybe 24% vs. a whopping 30in the previous version. It seems like the lift and engines got nerfed out of proportion to the lessened drag and air requirements. How is everybody else doing?