GoSlash27

FyunchClick, Sorry, I screwed up the challenge name. Here's the linky: http://forum.kerbalspaceprogram.com/threads/117415-SSTO-to-laythe-and-beyond Best, -Slashy

WingNutt, Deep breath. Spacing is hard and we've all been there. Step #1: Show us a picture of what you have at the moment. Step #2: Upload a craft file. Step #3: ??? Step #4: Profit! We will find what you're doing wrong, explain why it's not working, suggest better ways of doing it, and ultimately help you become a steely- eyed missile man. Best, -Slashy

JR, I'm afraid we're starting to go around in circles now I'm really not in a position to declare what's "OK" and what's not. I just try to figure out what "is" and how to make successful spaceplanes in accordance with that. What "is" is that struts (even nubs) make a lot of drag so they're best avoided in spaceplane designs in KSP 1.04. Maybe they could figure out a way to better- compute the drag, but then again maybe they can't without overloading the game engine. I don't know. I'm not a coder. Best, -Slashy - - - Updated - - - FyunchClick, For tips on maximum DV in orbit, I'd recommend the "single stage to Eeloo" challenge thread. Those folks are assassins. From what I'm seeing there they go with vertical launch designs, overpowered RAPIERs, weak LV-Ns for vacuum, and maximum streamlining. I personally don't have experience at that approach, since I only design for maximum economy and reliability to LKO and back. Good luck, -Slashy

That was my bad. I pulled the extra fuel lines and forgot to mention it. If you check the pic you'll see they're gone. Apologies, -Slashy

JR, The problem with that approach is one of gameplay balance. Back in .90 and earlier spaceplanes were so efficient that it didn't make any sense to use chemical rockets. We were doing all sorts of outlandish stuff with spaceplane parts. I had a vertical lifter that could carry a duplicate of itself into orbit as payload (LifterCeption) and I had a spaceplane that could do 3 round trips with passengers between LKO and the KSC without refueling (Groundhog Day). It was really pretty silly They've toned it down to the point where rockets make sense again. Personally, I think that jets are still a bit OP (see the leaderboard in the payload fraction challenge), but overall I think it's a reasonable compromise for balance and accessibility. Best, -Slashy

Well... the physics are what they are, for better or for worse. There's quite a few people who understand them better than I do. The important thing is to accept them as they are and just roll with it. There are some things that are easier in KSP than real life and some things that are harder. You have to account for the reality you're dealing with. The standard KSP mantra of "moar boosters" works well enough for rockets, but spaceplanes are all about efficiency so the reverse applies here. You always want less boosters, less struts, less dead weight... less stuff that's getting in the way and not adding anything to achieving the objective. Instead of thinking "what do I need to add to make this work", you want to think "what can I get rid of that's getting in my way". If you get into that mindset, spaceplanes are pretty easy. It's not really a matter of being smart so much as just having a proper state of mind. Best, -Slashy

Up to a point. IME you still want enough lift so that you can exceed 20 km altitude at 5° AoA. If you don't have that, then you're actually producing *more* drag than you would with more wings. Best, -Slashy

Actually, the "Rapier- spike" is a proven concept. It has to be offset so that it doesn't occlude the engine, but it's not really critical to success. Just ditch that for now and we'll revisit it later. Have you gotten rid of all the unnecessary control surfaces? *edit* better yet, do you have a .craft file we can play with? Best, -Slashy

JR, Ahh, but that is "real life" and we're talkin' KSP. "Basic physics are the same as real life such as gravity, but the rules are like those in any computer program. Some can be bent, others broken..." In KSP, every strut is a little parachute, even if it doesn't *seem* to be exposed to airflow. As has been shown here, even struts that *seem* to be aerodynamic really aren't and they can render an otherwise acceptable spaceplane incapable of achieving orbit. The moral of the story is to avoid struts if you're going to be spending time inside the atmosphere. If you must use them, triangulate to keep them at a minimum and ditch them whenever possible. "Do you think that my engines or my wings have anything to do with me being faster or more powerful in this place? Do you think that's air that your engines are breathing now?" Best, -Slashy

Nefrums, I think the confusion on my end was your mission to strip- mine Kerbin for science. It was pretty much undocumented, so I was like "wait... where'd all this science come from?" We actually have a caveman in the clan who never left Kerbin, so we know that this is possible. Sorry for putting you through this, and I'll get you on the wall as soon as I can. Congratulations and welcome to the clan! Best, -Slashy

Clipperride, The basic idea is you get it to the "ludicrous speed altitude" over Mach 2 in a shallow climb and "damn the torpedoes". Don't worry about shock waves or heating. Just get all the speed you can before the air breathers give out. This process begins at 16 km altitude for jets and 18 km for RAPIERs. and ends somewhere over 20 km. Best, -Slashy

Korthan, The stats changed a little, but what really changed is the physics. Engines now change their thrust with Isp. If you have crappy Isp (like the Terrier has at sea level), you will now have crappy thrust to go along with it. The optimizer has evidently not yet been updated to reflect this. Best, -Slashy

#1: It's really just a matter of moving the landing gear as close to the CoM as you can and moving your pitch control as far from the CoM as you can. Just maximize your leverage to get it to rotate. If you have a design that can't be rotated, then you can "cheat" it by building in some angle of attack. Just rotate the wings up slightly and it'll take off while still level. #2: Spaceplanes all follow the same basic profile regardless of size, but it must be adjusted for the thrust to drag, engine type, and t/w of the closed cycle engine. First step is to get it supersonic at around 10km altitude. Jets have an easier time doing this than RAPIERS. If you have high thrust- to- drag, you may blow through Mach 1 in a steep climb. If you have a very low t/d, you may need to do it in level flight or even a dive. But in any case, it should happen around 10 km altitude. Next, get to your acceleration altitude and build speed in a gentle climb. For jets, this is about 16 km. For RAPIERS, it's about 18km. Get the nose down and let it build speed in a shallow climb. velocity is cheap here, so get all you can before you're over 20 km. Once you're over 20 km and the air breathing is no longer adding velocity, you switch to rockets. If you have powerful and inefficient rockets you want to climb steeply to get over 43km and out of the drag as rapidly as possible. If you have weak and efficient engines, it's important to limit your climb rate so that your apoapsis remains at least 45 seconds ahead. Otherwise, you will fall back ballistically before you've had enough time to establish orbit. These are the important checkpoints. Some SSTO designs can burn right through them in a single climb and others stairstep very slowly, but they all hit these marks. #3: Several people have hit on this, and I just want to really stress it: The stock SAS/ control surface system sucks. It's too powerful and too laggy and *that's* why your spaceplane bobs around like an epileptic duck. You need to balance the plane so that it needs very little control authority to keep it flying straight, and then disable as many control surfaces as you can get by with. A lot of my small designs have no active controls whatsoever because the SAS/ reaction wheel is adequate to keep them in line. For most light/ medium spaceplanes, a single pair of control surfaces for pitch and roll is all you need. It's counterintuitive, but it's all those control surfaces that make it uncontrollable. Good luck! -Slashy

A_Name, Just grab one and go for it. Remember, you only get one shot! Good luck, -Slashy

Well... I use struts when I have to, but I minimize their numbers. Good struts are really more about geometry than numbers. If you do use struts, be sure to root them on the part that's getting discarded. It's the root node that makes all the drag. And of course... I don't use struts if I can avoid it. Best, -Slashy

Alshain, A RL orbiter vehicle weighs 75 tonnes, while in KSP it's closer to 25. It'd be unreasonable to expect an orbiter to lift nearly it's entire mass as cargo. A RL stack weighs 2000 tonnes, while a KSP stack weighs about 250. It would be unrealistic to have a shuttle that can do in- game what the real shuttle did. If we try to include real life engines in the game, they'll break it. Best, -Slashy

Nefrums, Thanks, that would be really helpful! Best, -Slashy

llanthas, Afraid so. Any mod that makes it easier to complete this challenge is strictly verboten. Ideally, it would be 100% stock in all cases, but we do allow mods that don't directly affect game play, such as radio chatter, lighting for filming, etc. Sorry, -Slashy

Ahh, but remember that was here on Earth. If you give that sort of ability to something in this game, you'll end up with something that can escape Kerbol's SoI entirely. Gotta maintain balance with the other parts and not create something that has no relevance in the context of the game. Best, -Slashy

Proof of concept The old running joke for the F-4 Phantom was very similar; "You can make a barn door fly if you put a big enough engine on it". Best, -Slashy

Nothalogh, Ain't nuthin' wrong with that. FAR is more realistic than stock, so it demands consideration of details that normally wouldn't apply to a stock install, like ventral fins, area ruling, etc. But I have absolutely no experience with FAR, as I never use any mods whatsoever. This is so whatever info I manage to figure out (or more likely need) will always be applicable to as broad a range of users as possible. But yeah... ventral fins make perfect sense where real life physics like airflow occlusion apply. Best, -Slashy

^ This. It's crazy- overpowered for a Kerbin- appropriate shuttle engine as it is. Mimicking a Skipper is adequate for a Kerbin shuttle analogue. 3 clipped Skippers for SSMEs. Best, -Slashy

FWIW, I disagree with this part. Space planes are all about mass- efficiency, and IME you can get by with low t/w ratios once the jets starve out and still come out ahead due to the Isp bump. I generally design for .5 t/w and have gone as low as .35. It really depends on how aggressive the initial climb is. Agreed. In fact, I *never* design spaceplanes to do any more than LKO with rendezvous and docking. Any more than that and you're best- served by not using something with wings/ landing gear/ etc. Also agreed here. Aero fins are really just drag and mass that you have to shove into orbit, so "less is more" so long as you have enough to keep it pointed where you want to go. This design would fare better without them IMO. Best, -Slashy

Congrats on your first practical SSTO! Lookin' good. It was actually a sound design the whole time. The only thing that was holding you back was the struts. Best, -Slashy

Nefrums, Sorry but I've got to call shenanigans on this entry. You were collecting way more science and achieving way more objectives per mission than I'm accustomed to seeing. I'm going to need a lot more documentation before I'll be comfortable accepting this one. Apologies, -Slashy