GoSlash27

Judging by the pic, your rudders are too close to the center of mass. Try moving them back to engines 2&5. Also, they should not be actively controlled surfaces, but rather plain old fins. Best, -Slashy

Bingo! That would explain it. Thanks, -Slashy

Highest speed I've attained in-atmosphere during an SSTO launch is over 2,400 m/sec on turbojets. I was surprised I could do that, since mathematically the turbojet is supposed to have zero thrust at 2.4 km/sec. Best, -Slashy

Mathematically, you'd aim for whatever you calculate. 1,568 km is the center-apex distance from which a 45* cone will lie tangent to Kerbin's surface. Realistically, I'd round the answer to 1,570 since I always round to 3 digits. Going higher than that will just waste radiated power by shooting some of it past the surface off into space. Best, -Slashy

RainDreamer, I concur with jimbimbibble. A cone with an apex angle of 45* will lie tangent to Kerbin's surface at 968km altitude. Perhaps something's off in the tutorial or specs? Best, -Slashy

Honestly, I doubt anybody *could* do the math on this. Simply too many interdependent variables. The phases of the launch aren't determined by the t/w, wing loading, or intake area, but rather the rate of change of atmospheric density. They would be handled using the same philosophy, even if your turbojet SSTO doesn't have any wings at all. 0-15km is the "soup" phase. High drag, terminal velocity doesn't change much, Isp isn't very good, thrust isn't very good. The best thing to do here is climb out of it as rapidly as you can without inducing a lot of drag by high angle of attack. 15-25km is the "cork" phase. Everything is improving at an increasing rate, and it's easy to end up too high and too slow. The climb rate must be limited to keep this from happening. 25-32km is the "wall" phase. Air is thin enough that generating lift is a problem. AoA must be managed to ensure that the wings are operating at their most efficient point, which is 22* AoA. If you have no wings, you need adequate thrust to keep you climbing (barely) and near terminal velocity. Pitch angle will peak out around 30* without wings. >32km is the "runway" phase. Angular momentum becomes the major contributing factor of lift. The wings are no longer useful, and although thrust is miniscule, so is drag. Climb rate must be managed to ensure maximum velocity occurs before flameout. Best, -Slashy

Rodyle, A lot of individual points in your response, and I probably can't address them all... No, Sir. Executing that phase on jets means that the losses are trivial due to the high Isp. "Sufficient" merely means "climbing" in that situation. Again, no Sir. You will not ever overcome insufficient lift with more intakes, particularly in the "wall" and "runway" phases. Sorry, but no. Ultimately, you make the same thrust from a given intake area/ altitude/ airspeed regardless of the number of engines. You could shut down engines and throttle up the others, or just throttle down all the engines. It works out the same way regardless; you have too many engines. Having more engines merely means that you have more mass and drag. Where you need the thrust is in the "wall" phase, where your engines are fully- fed and you're exceeding your induced drag to allow you to continue climbing. A bad philosophy for spaceplane design. More power or more wings or even more intakes isn't how you need to be thinking. It's "less pork". Spaceplanes are all about balance. You need "enough" of each attribute, not "more" of one at the expense of others. No doubt it was, but shutting down engines and dragging them along as drag and cargo is hampering your efforts. That costs you way more time and fuel than simply getting rid of them and feeding one engine. To each his own, but in that case you're asking a question that's impossible to answer. You're building a spaceplane that's not efficient by design and then asking how to fly it to make it efficient. The short answer is that you can't. You can fly it in a less inefficient manner, but it will never be "efficient" because you didn't design it to be capable of efficient operation. Personally, I always design my spaceplanes to be efficient and then let form follow function. Elegant designs tend to have their own aesthetic simply from having been designed to be efficient. Best, -Slashy

Kesa, Pure rocket SSTOs are very do-able; I've made plenty. I look forward to seeing what you come up with. Remember that it will be ranked by cost to produce and operate, and must be capable of delivery to a station in LKO with return to KSC. Best, -Slashy

You don't have to necessarily hit 45 degrees pitch. In fact, the exact pitch angle early on is not critical. Maintaining airspeed is. If you have insufficient lift, it's not going to hamper you in the early climbout, it's going to kill you in the 25-32km "wall" phase. You're never getting past it without enough wings, which is why it's referred to as "the wall". More engines or more intakes aren't the answer there. In fact, they'll just make the problem worse. What you need is proper wing loading, which means either ditching excess weight or increasing wing area. Best, -Slashy - - - Updated - - - That'd be "my" intake/ engine ratio, and no, it's 1/3. .024 m^2 per engine in my tutorial design vs. .0213 per engine in yours. And as I said, it will actually work fine down to .018. Rule #1: Engine/ intake ratio is meaningless. The extra engines aren't using the air from "their" intakes when you shut them down. What you have here isn't insufficient intakes per engine, but rather excessive engines per ton of aircraft. You need 2 engines and .36m^2 of intakes. That extra engine is nothing more than a boat anchor when you've got it turned off. And honestly, you could probably save a few tons by ditching 2 engines/ structure/ intakes/ fuel, allowing you to fit in the range where 1 engine is adequate for the job. You need 2 and you need to keep them lit. Also check my tutorial on multiengine spaceplanes and how to fix asymmetric flameout issues. I'm not familiar. I just know how to efficiently get spaceplanes into orbit. 2 turbojets and 1 LV-N are adequate to get you to Laythe and back with passengers if done correctly. I guarantee you were if you're starving for air at 30km. You want to transition to rockets about 500 m/sec faster than that. You solved your problem in the first sentence. The best remedy for an efficient launch with a poorly designed aircraft is replacing it with a properly designed aircraft. After that, it is as I said; fly it to efficiently build speed and use the rockets as little as possible. Best, -Slashy

That design isn't airhogging at all. It's got .024 m^2 intake area, which is a little over 1/3 of what you're using. In fact, you could use 3 of those radials and they'd be fine with a single engine. It is assuming that you have an adequate intake area and adequate wing loading. 1 turbojet is marginal for 17 tonnes of aircraft; you should really be using 2. 3 would be overkill. You said you're disengaging "some of" your engines? If that's the case, you have way too many engines for a 17 tonne aircraft. The basic idea of getting to orbit efficiently is that you get all the speed you can from the turbojets instead of rockets. It's not a matter of getting to altitude quickly, but rather getting to *speed* without flaming out. The fact that you're running out of air at 30km tells me that you're climbing too rapidly and don't have enough speed. Increasing intake area will keep your engines fed, but so will increasing speed at a given altitude. Don't worry about low acceleration at the bottom end. Ditch the extra engines; they're dead weight and drag. You want at least .018m^2 intake area per engine, 1.0 Cl worth of wings per tonne of aircraft, and 1 engine for each 15 tonnes of aircraft. Once you meet those requirements, you have to fly the plane differently in different phases of the launch to maximize your efficiency. Phase 1, 0-15km: Climb as steeply as you can while maintaining a minimum of 100 m/sec airspeed. Phase 2: 15-25km: Reduce your climb rate to maintain NMT 100 m/sec climb rate. Phase 3: 25-32km: Maintain a pitch of NMT 22* and let the plane build speed. Phase 4: 32-38km: Throttle back as necessary to keep the engines lit while maintaining NMT 100 m/sec climb rate. Once airspeed is no longer increasing, transition to rockets and pitch up 45* to establish apoapsis. Best, -Slashy

Air breathing engines have a pair of atmosphere curves in their config files. One sets the Isp as a function of pressure (and thus altitude). The other sets the thrust production as a function of speed. Basic jets don't really flame out earlier. They just can't hit the speed to pack as much air in the intakes, so they run out of air earlier with the same number of intakes. If you intake-spam a basic jet, it can stay lit all the way up to 70km... provided you can get it up there with so little thrust and speed. Best, -Slashy

Tylo isn't all that difficult. I demonstrated a pinpoint technique and vehicle in a tutorial here. You can do it with a much smaller and lighter lander if you're not worried about your exact landing location. Best, -Slashy

It is arbitrary, but immaterial AFA the math is concerned. It's like fretting over computing speed and distance in m/sec vs. miles per hour or furlongs per fortnight. The answer will be correct in the convention you assumed. Best, -Slashy

This is all true, but this competition isn't about merely making an SSTO. It's about making an affordable , safe, and economical SSTO that's useful for delivering payload to orbit. The difficulty is in not using turbojets or RAPIERs to do it. I have supplied a ramjet (which is proving difficult so far), but nobody says you have to use it. If you'd prefer to use aerospikes or mainsails/ whatever, I'm curious to see what you come up with. Best, -Slashy

I'm solidly with the majority on this one. It's not that the LV-1 is bad, but rather the 48-7S is too good. This is also aggravated by the lack of fuel tanks in the proper range to feed an LV-1. In the rare situation that the LV-1 is the most attractive choice, the heavier and more expensive tanks in it's range wind up tipping the balance back in favor of the 48-7S. Best, -Slashy - - - Updated - - - Agreed. Even on Tylo, the 48-7S yields a smaller and cheaper ascent stage than the LV-909. Assuming a 1 tonne payload the 48-7S can do the job for 1.63 tonnes and $1,235. The LV-909 needs 2.02 tonnes and $1,424. Best, -Slashy

Politics, same as today. Getting funding meant keeping senators happy and keeping senators happy meant spending funding in their districts. http://www.houstonchronicle.com/news/houston-texas/houston/article/A-worthy-endeavor-How-Albert-Thomas-won-Houston-4815595.php#/0 Best, -Slashy

Well of *course* there's organic compounds on Mars. There's organic compounds all over the place. That doesn't mean there is or ever was *life* on Mars. Not fussing at you, FishInferno, but rather at the media. They've really overblown this story IMO. Best, -Slashy

That's true, but a ram intake also lacks the surface area to do the job with just one intake, which means you'll either need 2 (which is overkill) or assist with the XM-G50. More importantly, it conflicts with drag balancing, which demands intakes in the back. The stack mount intakes are really good, but I don't recommend bothering with them unless you're dealing with a multiengine design. They tend to have unused real estate that's perfect for stackable intakes. Best, -Slashy

First attempt was a bust. I established orbit and deorbited/landed fine, but it really doesn't have the DV necessary for orbital intercept and rendezvous. I need to deliver my Kerbals to the station, not just take them sight-seeing. I have room to plug in more oxidizer and fuel, but it's also right on the edge as it is for t/w and wing loading, so I may need a complete redesign. Best, -Slashy

PTNLemay, Glad you found this helpful. It's always gratifying to hear about the success stories! The XM-G50 intake is actually pretty unremarkable AFA it's stats. The reason it tends to fare well is because it doesn't require additional structure to mount. All the stackable intakes require a flat forward facing surface, which means more structure, which means more weight and drag. I also put together an intake comparo if you want to check it out. Best, -Slashy

All, Thanks for the kudos, though as several folks have pointed out I haven't actually made anything new here. I would've done this as an MM edit, except for a couple minor snags: #1: I don't know how to do an MM edit #2: I don't know what an MM edit is. So there's that... As it is, we're playing with this new toy over in the challenge section to see how much it has de-nerfed the turbojet WRT the other offerings. Best, -Slashy

Much more difficult this way. The RAPIER is actually attractive. I look forward to seeing you complete a shuttle mission with it! Best, -Slashy

Orbit established. I have my proof of concept, so hopefully I'll have a complete mission tomorrow. I've got room for 8 passengers and it'll probably be over $40,000 before it's ready. /That *sucked* ! -Slashy

This is harder than I expected it to be.... Still trying to establish orbit.

I agree, but where else would I put it?