foamyesque

@Triop: Could I have a definitive statement on whether stage-level save/loads are acceptable? Because if they aren't I'll need to rethink things.

Without seeing a picture of the plane in question I can't say for sure but this issue is almost always caused by an interaction between your aerodynamics and your wheel placement. Your center of drag is ahead of your center of mass, and the usual cause for that while on the ground is your rear gear losing traction and your front gear being pressed down. Fire up some screenshots

The real trick is recovering the airbreather, in a pure-stock non-autopilot scenario; craft below 25km altitude and outside the physics range of the focus object will be autodeleted. It might be possible to do a relatively high-angle ascent and spike the carrier's apopasis high enough that, in the time it takes to fall back under 25km, the shuttle vehicle can push it's apoapsis high enough to let you then turn around and land the carrier, but honestly it's a bunch of faffing about when a much simpler process would be to simply go SSTO, or at least single-stage to suborbital.

Time is observably discontinuous. One need simply build a large spacecraft to notice this!

This would be a lot easier if I was willing to go slower :v Those extra 9 seconds over 6min annoy me. It's purely because I screwed up my braking and overshot, so I had to circle back.

They're independent lists; that's why the second one has a minimum payload requirement. So if A were to enter one thing with 110ts to orbit and an operating cost of 100 funds/tonne-to-orbit, B launched one with 200ts to orbit and an operating cost of 120 funds/tonne, and C made something that put 50t in orbit at 80 funds/tonne, the lists would look like so: MAX TONNES: 1. B (Jumbo 8, 200t) 2. A (Try Harder 4, 110t) 3. C (MIssing The Point, 50t) EFFICIENCY: 1. A (Try Harder 4, 100 f/t) 2. B (Jumbo 8, 120f/t) Make sense?

Okay so, lots of people can make spaceplanes these days; there's plenty of tutorials, good parts, and so on. But in general those planes can't carry as much mass into orbit as some guy who slapped some stuff on top of a Mammoth, for various reasons. This leads to a lot of "put an orange tank into orbit" challenges and the like. I'm tired of them... So here's a challenge to build spaceplanes that can carry the biggest, heaviest payloads into orbit. The rules are as follows: 1. Horizontal takeoff; 2. No decoupling (or undocking, or explosive staging), with the exceptions of deploying the payload or jettisoning fairing covers; 3. Payloads must be a single unit that doesn't contribute to the vehicle's flight (i.e. no thrust or fuel can be consumed from it; electricity and reaction wheels are acceptable); 4. The craft must be able to land, intact, on Kerbin after payload deployment (landing at KSC not required, landing need not be horizontal); 5. The payload must be deployed into at least a 100x100km orbit around Kerbin; 6. Payloads cannot include ore (empty ore tanks are acceptable, but not ones with anything in them); 7. For purposes of fairness, only stock craft are legal, but flight info and autopilots (e.g. KER, MechJeb) are fair game. 8. No refuelling of the vehicle is allowed; 9. FAR users get a separate result table. There will be two kinds of scoring: A. Raw tonnage to the 100x100km orbit; B. The per-payload-tonne cost of all consumables used during the full flight (i.e., until the vehicle is landed on Kerbin). The minimum payload to be listed here is 100 tonnes. Happy launching

I meant find a specific navball pitch angle, not AoA. AoA varies, as it should; you want higher AoAs for max lift on takeoff and, as speed builds and you start generating enough lift to actively climb, your prograde vector will pull up to your noses' pitch, at which point you proceed to go supersonic. Then your nose stays pitched under your prograde heading to keep your climb rate under control so that your airbreathers have enough time to build speed, until the air thins out enough that your prograde marker starts dropping back down to match your nose again, which is about when you're in your final climb-with-minimal drag phase of the speed buildup. Somewhere around 21-22km the RAPIERs will cease to accelerate the craft, which is my cue to swap to rockets. Now, granted, this is how I fly the spaceplanes I design, and I design them to fly the way I like to, but when I've borrowed planes from other people's posts on here, I've generally found the same approach works. The precise angle I choose depends on the thrust, lift, drag, and thermal balances of a craft, but 5-15 degrees is generally the band, with high TWR crafts hitting the upper end and lower TWR ones the lower. A non-trivial problem with low-TWR spaceplanes IME is spending too long in the 20-25km area, where drag is still significant. A 5 degree climb rate pushes you through that area with 130m/s+ (depending on your horizontal velocity), which is about the minimum I consider acceptable. My powered flight (excepting circularization) generally ends with 105x5km (or so-- the periapsis varies by a couple of kilometers) as the orbital parameters, at an altitude of 30km or so. There's enough vertical speed that drag will only pull it down to 100x0km - 100x-5km, which is a trivial circularization burn (I have in fact completed it with TWRs at or under 0.05 :v).

@AeroGav: It's been my experience that absolute maximum speed level flight is easier to achieve on the deck with RAPIERs: the Mach limit at which they hit 0 thrust is much higher in absolute speed because of the faster speed of sound. I also have tended to find that the best spot to pile up speed is the 10-15km region, where your wings can support you as you racket up from 1000m/s to 1500m/s. As I get up to 20km+, unless carrying way more wings than needed anywhere else, there's not enough lift+engine thrust to keep a steady (or accelerating) climb rate whilst simultaneously accelerating. I tend to have 95% of my maximum speed by 15km. This also aids in a very simple flight pattern of finding an angle that works, and just holding it. Faffing about with squeezing every last possible erg on the airbreathers can take forever, too. You can get the vast majority of a spaceplane's efficiency savings without needing an hour-long flight to orbit; with a non-minimalist TWR and good drag characteristics, powered flight can be five minutes or less, which is right there with rockets.

Big S parts are the spaceplane delta, strake, elevons, and tailfin. You're thinking of the FAT ones.

Say what? They have the same 2400K tolerance as the wings you were using.

Such designs don't have a TWR > 1. If they did they'd be able to take off from the runway, too.

I don't agree. I am also no particular stranger to large aircraft. In my experience, the XL landing gear are plenty large for just about every purpose (I at one point had a 2000t craft launching on them) and the length of the runway doesn't actually make as much difference with mass as you might think; it's a question of thrust:mass, thrust:drag, and lift:mass ratios, not absolute mass. It's easier to get higher ratios for smaller craft because the structural considerations (joint strength, etc) are so much simpler to deal with, but dial down a Juno to 0.25 TWR and watch how long it takes a light plane to take off

Engine thrust keys on Mach number. The same Mach number ASL corresponds to a higher indicated airspeed, and the thrust curve of the rapiers is such that their thrust increases faster than drag as you get closer to sea level as a result of both that and the altitude adjustment.

Hey, that's nice of you to say @GoSlash27. For what it's worth, even when we disagree on things, you're one of the people whose thoughts I pay attention to.

As low as possible for your capture burn, but inclination changes are best done as slow (i.e. high) as possible.

You use more fuel per second, yes, but: 1. Drag losses (both aero and gravity) accumulate with time. Shorter burns lessen the time they have to work; so if for example you have aero drag losses of 1000kN and a thrust of 2000kN, you only get 1000kN of force going to acceleration; if you have a thrust of 3000kN, you get twice as much acceleration for only 50% additional engine mass. Since planes and SSTOs generally have high dry:wet ratios and much higher aero drag losses (compared to staged rockets) this is much less of a penalty than it is with rocketry for a much larger benefit. 2. The additional speed above 1500m/s on the airbreathers, if you can get it, saves you a giant pile of oxidizer (or, for nukes, a long, slow, draggy acceleration), and hence saves weight overall.

Make sure they're behind your CoL, though, or you'll tend to lift your rear gears off first, which will cause spinouts. Says you. I've hit Mach 1 on the runway

Bah. Me, I design and fly my planes very differently than most of the above. 1. Thrust is life. I wouldn't drop below more than one RAPIER per 25 tons of craft; you can get away with even less, but unless you're hyperoptimized for drag, its really, really painful. More thrust means you have more acceleration low down, so you spend less time getting to speed, and it means you have more speed higher up, which means you need to run your less efficient rockets much less. Better TWR also means you waste less dV against drag and gravity when you punch it for orbit on the rockets. Adding more engines can and often does increase your payload capacity, provided you can handle the thermal loading. 2. Contra @GoSlash27, I design my spaceplanes to be agile, with either relaxed stability (CoL in CoM) or sometimes even dynamic instability (CoL ahead of CoM). I do this not for ascent -- though it means almost no control deflection is needed to steer, which helps drag-wise -- but for re-entry and landing, where being able to generate large AoAs quickly is very useful. 3. Balance is crucial. You want to eliminate longitudinal CoM shift if at all possible, so you get consistent flight dynamics regardless of if your fuel tanks are full or empty or you have anything in your cargo bay. 4. You don't need many air intakes. One shock cone can easily feed six RAPIERs throughout flight; if maxing your throttle on the runway doesn't cause flameouts you've got more intakes than you need. 5. Nothing fancy is required for ascents. Point your nose to 5-20 degrees, depending on your TWR, drag, and thermal balances, and just maintain that until your apoapsis hits the orbit you want. Swap to closed-cycle once your airbreathers stop accelerating you, usually around 22km for RAPIERs. I like to aim for an apoapsis of 105km; drag will usually round that off to 100km.

That's what I'm answering

Nah, it's thermal effects that are the killer. Also you burn fuel like crazy. :v

I haven't built one specific to this challenge, yet. I've been poking at the El Cano ground circumnavigation one for a while, and I've tested out various concepts for high speed travel. because I'm an impatient person. I kept circling back to a Panther-powered large jet rover, for the ability to kick on afterburners for slope climbing and its TVC for steering, and landing gear as the only wheels that can survive heavy shocks and also be able to reduce water drag. Since there's no water on this course I may try other approaches.

Going low, to take advantage of the higher speed of sound. The trouble is that the RAPIERs overheat...

I hadn't thought of exhaust blocking. Otherwise the jet spooldowns wouldn't be way too slow to respond except on the very longest of long jumps. EDIT: Junos are for chumps though. :v Heh. You can actually work out mathematically the sharpest circle you can crest and still keep ground contact, and the trouble is, the crests of the hills around KSC need massive amounts of it :v

In principle it is possible to launch from 0 altitude on Kerbol, with ignore-max-temps turned on. I don't believe it's possible to achieve orbit without further cheating, though.