GoSlash27

Val, I like the Skylon! Best, -Slashy

xendelaar, Thanks, but it's not really any big deal. It takes less mathing than what you've already done. The equations are here and the constants are here. It's like anything else; if you have the equations and constants, it's just a matter of using algebra to manipulate it to suit your needs. Good luck and I'm very interested in seeing what you come up with! -Slashy

Captain H@dock, I dunno. I'm sure it'd be more difficult to see the change if you have poor resolution, but it's still the same fixed amount per "click" (mouse movement of 1 pixel). I'm not playing at a high resolution (1280x720 window) and I can see the movement okay. Best, -Slashy

selfish_meme, He's talking about a solar retrograde orbit, not Kerbin. Don't worry, I've made the same mistake once or twice... Solar retrograde is gonna be expensive Best, -Slashy

^ This. I ignore the atmosphere entirely for everything above 8km. A single "booster" stage that operates in that region is calculated at 1/2 atm. Generally for a 2 stager (which is all the staging I ever do on Kerbin), the lower stage is 1800 m/sec DV at 1/2 atm and the upper is 1600 m/sec at vacuum. Anywhere beyond 75km apo with atmospheric per is another stage and is all payload for launch purposes. I do something similar to what it sounds like you're doing; I run a reverse rocket equation to simulate each engine simultaneously for the payload, t/w, and DV requirement. From there I can pick my best option for a stage by minimum mass, lowest cost, or simplest construction. Best, -Slashy - - - Updated - - - Steelsunoa, Oh, yeah. I have spreadsheets for calculating DV budgets for orbital transfers, burn timing, resonant orbits, transfer windows... All the basic maths work in KSP. Best, -Slashy

I knocked together a quick and dirty "cheat sheet" for RAPIER powered spaceplanes. Lower payload per RAPIER makes a very fast trip to orbit and less emphasis on clean aerodynamics. Higher payload per RAPIER means that being aerodynamically clean is much more critical and the trip will take longer, but has higher efficiency. So for example: You have 20 tonnes of payload and decide to use 5t per RAPIER; 4 RAPIERs. You would refer to the chart for jet fuel and multiply that number by your payload. .43*20= 8.6t of jet fuel. Same for rocket fuel. 1.2*20= 24t of rocket fuel You would build this, then note the total mass. (somewhere around 80t) multiply this by the lift value (.14) to get the total lift value of wings; about 12. This is rough, but should get you in the ballpark. Best, -Slashy

Gooru, The ratio of parts required varies with the parts you're using. An early career passenger shuttle with Mk2 parts is a different beast than a late career tanker with Mk 3 parts. For a simple early career crew shuttle it goes like this: for every 5t cargo (everything that isn't either engine, fuel, oxidizer, tank, or wing) you will need roughly: 1 Whiplash 2 LV-909s 10t lf&o to feed the rockets (450/550) 400 fuel to feed the Whiplash (about 1.76t) Put that all together as aerodynamically cleanly as you can (don't forget the ram air!) and then total up your mass. You should be around 19t per 5t payload. For wings, there's a surprisingly wide range of ratios that can work. The important thing isn't so much "lift to mass", but rather "zero nose incidence at Mach 1". You can do this with small wings at high incidence or large wings at low incidence. A good starting point would be mass/3 with 2° incidence (3 clicks of fine rotation). This is good for roughly 26% mass efficiency (payload/ total mass) High tech tanker to follow... - - - Updated - - - for a High tech Mk3 tanker/cargo design: 1 RAPIER for each 10t cargo 1 shock cone per RAPIER 1t LF&O for each tonne of cargo (err to the high side a little). 2.8t jet fuel per 10t payload Same deal with the wings; it's all about the angle of attack. It's more important to minimize wing panel count to avoid strutting than worry about an exact wing/ mass ratio. You can make up for small wings with incidence... up to a point. mass/10 at an incidence of 10° will work, or you can do larger wings at lower incidence like mass/3 at 2°. As you move away from these "extreme efficiency" designs towards higher t/w designs, wings and aerodynamics in general become less critical, but you will need to increase the ratios of jet fuel, rocket fuel, and engines to payload to compensate. This is good for roughly 31% mass efficiency At the other extreme, the high t/w vertical RAPIER lifter. One RAPIER for each 1.5t of payload 2t LF&O per RAPIER .75t jet fuel per RAPIER and of course wings are unnecessary. This yields roughly 23% mass efficiency. Best, -Slashy - - - Updated - - - Rizzo, Just for you, here's how I evolve a design: First off, all rules of spaceplane construction apply. You want balance, low drag, minimal strutting/ piping, etc. You can expect roughly 4 tonnes of spaceplane for each tonne of payload (varies with efficiency), so just scale it up. Decide what combo of engines you want and plan accordingly. Now here's the trick: Build the entire thing out of fuel tanks. No payload, just fuel. The objective is to get it supersonic, then hypersonic at altitude, then finally into orbit. See how much mass you can get on it until you can't do it anymore, then back it off. You always want to find ways to improve efficiency and eliminate unnecessary weight and drag rather than adding engines or fuel. Whatever mass of fuel and oxidizer you have left in orbit (minus your reserve for orbital maneuvering and deorbit) is how much payload that design can handle. Once you're satisfied, take note of all the ratios you used to accomplish it and build another with actual payload replacing the unused LF&O. Best, -Slashy

Claw, Thanks for this. It answers all my questions! -Slashy

Vist, The main problem is in getting them into orbit from KSC. wide payloads generate a lot of drag on the ascent. For landing and launch from the surface of airless bodies, they are ideal. Best, -Slashy

RIC, Some advice: When you're trying to get through Mach 1, you can choose to add thrust or reduce drag. While adding thrust is very "kerbal", it tends to quickly run into diminishing returns. The advantages of reducing drag, OTOH, tend to reinforce themselves. One of the advantages is lighter, simpler, stronger assemblies that are easier to fly. Best, -Slashy

Oh, okay. Thanks for clearing that up! -Slashy

Brainlord Mesomorph, Hey, more power to ya It's your game and there's no wrong way to play it. But we're just gonna have to agree to disagree on the difficulty of making cargo spaceplanes. I can design and build spaceplanes that haul cargo just as easily as spaceplanes that haul supplies (see earlier photo). It's all the same to the plane whether the payload is kerbals in a passenger compartment, fuel in a tank, or cargo in a bay. It's the same engineering exercise, so I don't know why you would find one more difficult than the others. for me, this is no more or less challenging than this or this There are a lot of aspects of design that would make one spaceplane more challenging than another, but I don't think the type of payload would be one of them. All that aside, I'll be interested to see what you pull off. Best, -Slashy

SanderB, Yeah, I actually do understand what you're saying and I take that into account as well. The extra time required to put recoverable SSTOs into orbit and the time spent recovering them is pretty small compared to the time spent actively controlling an intercept, rendezvous, and docking. But of course if you're not doing all that then it is a lot quicker and easier to just use a disposable lifter. Best, -Slashy

Oh, I disagree. It's not that it's any more of a challenge to lift cargo with spaceplanes, it's just that it makes no sense (at least in my program) to do that. My current tanker carries more fuel than the orange tank and it's certainly not any easier to accomplish that. Using spaceplanes for cargo means I have to limit the dimensions and mass of the payload to what the spaceplane can handle and any particular spaceplane design wouldn't be used often enough to justify the R&D time. Shuttling kerbals and transporting fuel, OTOH, is something that I do regularly. If it's not a job that 1) spaceplanes are best at and 2) I'm going to need to do often, I just plain don't design a spaceplane to do that job. Best, -Slashy

I don't know about "a lot", but it definitely takes more time. If you're just putting a chunk of cargo in orbit, then yeah. But if you're actually docking with something else, the difference in total time spent is pretty small. Best, -Slashy - - - Updated - - - Agreed. Higher payload fraction, minimum stage mass, and minimum cost are worth optimizing for. DV isn't. But still and all... people do need a good guesstimate of how much DV they need for the job for design purposes. Best, -Slashy

^This. I don't lift cargo with spaceplanes, I lift supplies. I did, however help somebody sort out their cargo lift spaceplane and it carried a big orange tank, so I guess that counts *shrug* Best, -Slashy

I haven't named many land features or continents and those that I have named are pretty uninspired. I call the home continent "Africa" and the next one west "India". The peninsula to the East is "Korea". There's also the Crater Basin and the Badlands crater. Other than that I haven't named anything. Best, -Slashy

All, Thanks to the Clawerator, I was able to understand how the wing lift is computed in KSP. It basically takes the lift rating of the part, adjusts it IAW the spline curves in the physics.cfg for Mach and attack angle, then proceeds normally with density and airspeed. I *THINK*... But drag has me stumped. What value does it begin with for drag calculations? Do all wings with the same lift rating generate the same drag? Does it start with the wing's lift rating, or drag box value, or something else? Thanks, -Slashy

Geschosskopf, Maybe your mouse, but not mine. I have no problem rotating parts in discrete "clicks" in free mode. This is how I'm setting inclination angles lower than 5°. Best, -Slashy

Geschosskopf, This is actually what I'm talking about, but it's not truly analog it just has fine steps. Best, -Slashy

Val, I believe that each click of fine rotation is around 3/4°. I alter the incidence depending on the ship's mass/ cumulative lift. Best, -Slashy

Val, I'd agree with most of this, but the difference in mass between larger wings at low angles and smaller wings at high angles is a pretty tiny percentage of the mass of a spaceplane. My point is if you already have adequate lift from a design, rotating the wings up as was done here isn't going to have much benefit if any. Best, -Slashy

RocketBlam, There's a closer desert biome on the same continent as KSC. You didn't have to cross the ocean. I also hit up the Kerbin biomes in early career to jump- start my tech tree. Best, -Slashy

ajburges, I'd really have to see some pics of what you were working with. If you have an adequate design without incidence then adding incidence doesn't benefit you much if any. Adding incidence is really about 1) getting the nose aligned with airflow during the critical transsonic region and 2) getting lift out of wings that are really too small for the job. It's part of an entire integrated design philosophy, not something that you can just tack onto an existing design and expect it to work better. Best, -Slashy

haha you've clearly got me confused with someone else! Bonus: You've just confirmed that the intake volume mass still applies in 1.04. So that settles it then? There's no demonstrable benefit to closing intakes in 1.04? I hadn't tested to see, I just never noticed an advantage one way or the other. Best, -Slashy - - - Updated - - - Capt. H@dock, That's an interesting question, and one I've never attempted to answer. Seems like it'd be worth an experiment (hint hint). Subsonic is pretty slow for that altitude, so not only would you be dealing with insufficient lift, but also insufficient airflow for the engines. At the other extreme (if you get that far) you've got a whole lot of velocity and heating. You would pretty much have to see a swing in the AoA in that test *but* that doesn't represent an actual launch profile. The way I do it is I run the whole profile and note the AoA throughout the whole thing. if I'm carrying AoA (especially at Mach 1.1 in level flight because that's the really important part) then I need either more wing or higher incidence. Opposite means I need less. When it's dialed in the prograde and forward markers are aligned the whole time. Best, -Slashy