GoSlash27

Sardia, The way I figure it, jet engines are only useful as a first stage and first stages are considered disposable in a stock career game. So even though they use very little fuel and therefore get you more payload fraction, they aren't cost-effective. Cost- effectiveness is always the primary concern in my first stages, so I tend to go with cheap liquid fuel boosters in early career and SRBs once I unlock the BACC and Kickback. They weigh more, but they slash the launch cost. Best, -Slashy - - - Updated - - - Sardia, SRBs have limited DV due to their poor Isp. Putting wings on them and "flying" them increases the DV budget, which puts them at more of a disadvantage than they would otherwise be. Best way to use an SRB IMO is to employ it as a first stage in a conventional ballistic launch. Best, -Slashy

I remember 5thHorseman used one for the Caveman challenge. Best, -Slashy

51t payload, here's what I'd do: Booster: 1x Mammoth 2x S3-14400 Transstage/ orbital injection 1x Rhino 1x S3-3600 1x S3-7200 Best, -Slashy

Take a tip from HighGuard. Spacing isn't all that hard. As I recall he started small he had to flip a rocket or two. Best, -Slashy

^What Soulsource said. We don't just climb straight up to 10km and hang a right any more. We make a very gradual and constant prograde turn pretty much right off the pad. We don't use crazy- high acceleration. The rocket's easier to fly if you keep it under 2g. We don't build blocky flat-faced rockets any more. We streamline them. As for the targeting and maneuver nodes, you don't get those until you upgrade mission control and tracking. Getting to orbit is still workable in early career. As for science... did you know that each area of KSC has it's own biome? The rooftops too if you can figure out a way to get up there without collapsing the building. Best, -Slashy

FridaSpace, I'm not an astronomer and I don't play one on TV, so take anything I say with a grain of salt. IIRC, not every star is capable of going supernova. You want something that's 1)hot 2) big and 3) old. Ideally a group of blue giants in a globular cluster would be ideal by my understanding. They'll fit the bill. We have a few of those hanging around our galaxy outside of the galactic plane. Look for a spherical glob of blue- white stars with no clear structure away from the Milky Way and focus on that. Of course, I could be totally wrong Best, -Slashy

Case#2: The medium thrust upper launch stage The procedure for this is exactly the same as for the low thrust vacuum stage with 2 minor adjustments: The DV requirement is 1800 m/sec and the g requirement is .7g. Otherwise, same priorities apply. Light is more important than cheap because excess mass here increases the workload of our booster stage. Also, I like to make this stage recoverable in order to recoup some of the launch cost. We have a 22.1t payload going to orbit, to which we've added a decoupler and reaction wheel (.15 tonnes) for a total of 22.3t. acceleration requirement is .7g and DV is 1,800 m/sec The aerospike would be lightest and the poodle would be cheapest, but I'll analyze the Skipper. Step 1 The Skipper generates 650 kN of thrust in vacuum. at .7g minimum acceleration, this works out to 650/(9.81*.7)= 94.7 tonnes Step 2 using the reverse rocket equation for 1800m/sec DV and the skipper's Isp of 320 sec, 1800/(9.81*320)= 0.573 e^(0.573) = 1.774 Wet to dry ratio To convert this to fuel fraction, it's (1.774-1)/1.774= .436. 43.6% of this example rocket would be fuel. Step 3 Tank mass in this case would be .436/8=.0545. our fuel tanks comprise 5.45% of our total stage mass. Adding the fuel and tanks yields .491; 49.1% of our total mass is fuel and tanks. Multiplying this by our capacity yields (94.7)*.491=46.5 tonnes of tank and fuel and of course our engine is another 3t of mass So a single engine's payload capacity would be 94.7t (lifting capacity) - 46.5t (mass of fuel and tankage) -3t (mass of engine)=45.2 t payload. Step 4 This time we have the opposite problem; 1 engine is more than enough for this job. So we'll skip ahead to the next step and trim the unneeded fuel and tankage out of the design. Step 5 So now that we have our number of engines and required wet to dry ratio, we can calculate the tank mass for our actual stage. (1.774-1)(1*3+22.1) _________________= Mt (9-1.774) .774(25.1)/7.226 = 2.69t Our empty tanks weigh 2.69t. Our fuel weighs 8 times as much; 21.5t. Our engine weighs 3t Our payload weighs 22.1t All together, our stage with payload is 49.3t Plugging this into the rocket equation as a quick sanity check yields 1,800 m/sec DV Now... since I'm nowhere near the limit of what this stage can handle, I'll probably slap a control head on it and 6 parachutes (it weighs about 6 tonnes empty) and recover it while still barely suborbital to recoup some of the cost. - - - Updated - - - von Ziegendorf, This is no longer true for KSP post- 1.0. That has been corrected and the correct g0 is now 9.81 m/sec^2. Best, -Slashy - - - Updated - - - I have to get ready for the Hawkeye game, so I'll pick this back up afterwards. Best, -Slashy

Case #1: The low thrust vacuum stage. I have 10 tonnes of payload going to Duna and back. Assuming aerobraking at both ends and a 10% DV reserve, I want 2 km/sec DV total. Minimum acceleration is .5g For the interplanetary stages, the most important considerations are stage mass, cost, and simplicity in that order. Low mass here means the booster and injection stages will have less payload to lift to orbit. Cost is always a factor in career mode, and simplicity may give you a friendlier payload to shove into orbit. Plugging theseinto my spreadsheet shows that the LV-N would be lightest and the Poodle would be cheapest, but for this demonstration I'll work out the LV-909 Terrier. The process goes like this: 1) How much total mass can a single engine move at my required minimum G? 2) How much of this mass would need to be fuel in order to hit my DV goal? 3) How much payload would this theoretical rocket be able to handle? 4) How many engines do I actually need to handle my payload requirement? 5) How much fuel and tankage? 6) What does it cost? Step 1 The LV-909 generates 60 kN of thrust in vacuum. at .5g minimum acceleration, this works out to 60/(9.81*.5)= 12.2 tonnes Step 2 using the reverse rocket equation for 2km/sec DV and the LV-909's Isp of 345 sec, 2000/(9.81*345)= 0.591 e^(0.591) = 1.806 Wet to dry ratio To convert this to fuel fraction, it's (1.806-1)/1.806= .446. 44.6% of this example rocket would be fuel. Step 3 Different fuels have different tanks to hold them, so you need to check the mass of your representative tanks when full to their mass when empty. For LF&O tanks, they weigh 1/8 of their fuel. Tank mass in this case would be .446/9=.0558. our fuel tanks comprise 5.58% of our total stage mass. Adding the fuel and tanks yields .502; 50.2% of our total mass is fuel and tanks. Multiplying this by our capacity yields (12.2)*.502=6.12 tonnes of tank and fuel and of course our engine is another .5t of mass So a single engine's payload capacity would be 12.2t (lifting capacity) - 6.12t (mass of fuel and tankage) -.5t (mass of engine)= 5.58t payload. Step 4 But of course we need to move 10 tonnes in our actual lifter, so we would need 10/5.58= 1.79 engines. And since there's no such thing as a partial engine, this rounds up to 2. Step 5 So now that we have our number of engines and required wet to dry ratio, we can calculate the tank mass for our actual stage. (Rwd-1)(NMe+Mp) _______________ = Mt (Rfe-Rwd) where N = number of engines Me= mass of 1 engine Rfe= the ratio of our fuel tank's mass when full to mass when empty (9 for LF&O tanks) Mt= mass of empty tanks (1.806-1)(2*.5+10) _________________= Mt (9-1.806) .806(11)/7.194 = 1.23t Our empty tanks weigh 1.23t. Our fuel weighs 8 times as much; 9.84t. Our engines weigh 2*.5t= 1t Our payload weighs 10t All together, our stage with payload is 22.1t Plugging this into the rocket equation as a quick sanity check yields 2,031 m/sec DV Step 5 We would need 22 FL-T100 tanks to hold this fuel, which is 2 FL-T800s, 1 FL-T400, and 1 FL-T200. Plus the cost of 2 Terriers. This would work out to about $4,080.

I use a spreadsheet to design my stages before I build them so that I am assured they are the lightest and cheapest designs for the job. I've been asked to explain how the process works and have some free time this morning... so here goes. I will demonstrate the process in 4 specific cases: 1) low thrust vacuum stage 2) medium thrust upper launch stage 3) high thrust liquid fuel booster stage 4) high thrust solid propellant booster stage I will try to explain the unique considerations for each This will take a while, so please bear with me... a little background: This method relies heavily on the reverse rocket equation , converting thrust to lifting capacity, and adjusting Isp & thrust for atmospheric density. The rocket equation: DV= 9.81Ispln(RWD) where DV= change in velocity in m/sec 9.81= g0; the standard conversion in m/sec2 Isp= the engine's specific impulse in s ln(x)= the natural log function and RWD= the stage's wet- to- dry ratio; it's mass when fully fueled divided by it's mass when empty. The reverse rocket equation: RWD= e( DV/9.81Isp) where e= Euler's number; approx. 2.718 Converting thrust to lifting capacity T _____= M g0*gr where T= thrust in kiloNewtons g0= local surface gravity, 9.81 m/sec2 on Kerbin gr = minimum acceleration requirement in gs M = lifting capacity in tonnes Adjusting thrust for surface atmospheric density: SurfaceIsp*T ___________ = surface T VacuumIsp Adjusting Isp for a booster stage: I always assume that the booster stage will work in an average atmospheric density of 50%, so... (Ispsurf+Ispvac) ______________= Booster Isp 2 Converting Rwd to fuel fraction (Rwd-1)/Rwd= fuel fraction Figuring out tank mass in the final design (Rwd-1)(NMe+Mp) _______________ = Mt (Rfe-Rwd) where N = number of engines Me= mass of 1 engine Rfe= the ratio of our fuel tank's mass when full to mass when empty (9 for LF&O tanks) Mt= mass of empty tanks a final note before I get into the demonstrations: This process works fine by hand if you've already narrowed down the candidate engines (or have a limited set of options), but it would get tedious to do it by hand for all possible engines. This is why I use a spreadsheet to do the job. By comparing the results in mass and cost, I can quickly pick the best option for the stage. Best, -Slashy

CAKE99, That would be the simple solution, but I don't use mods. What's the size and mass of the station segment? Best, -Slashy

MKI, If you just want to spam intakes, the shock cone is a good choice. It's one of the most aerodynamic things you can put on the front of a spaceplane. But you don't want to add forward facing surface area just to have more shock cones. Considerations for drag reduction: 1) Present a clean transition from one part size to another. No sudden changes. 2) Minimal frontal area. Don't build short and wide if you can build long and thin. 3) Avoid surface mounting parts as much as possible. batteries, RCS tanks, struts, etc. And "clipping" them doesn't hide their drag. 4) Wings are a lot less draggy than other parts, so don't be afraid to use them. You exhibit the least total drag when your nose is lined up into the slipstream, so design it to fly that way at Mach 1 and above. 5) Some parts are cleaner than others. ex. The linear RCS port is much cleaner than the RCS block. Some parts are cleaner when mounted in a certain direction. ex. Landing gear are cleaner when mounted backwards. Some parts should just plain never be used. ex. The "mobility enhancer" folding ladders are absolutely awful. If you can get your spaceplane past 360 m/sec in level flight, you can get it hypersonic at high altitude. The objective is to use as few engines as possible to do it. This makes less dead weight for your rockets to push to orbit, and therefore less fuel required. Best, -Slashy

UV Radiation, I couldn't load it. It has non- standard parts. "IRHingeTallNDScaleable" Best, -Slashy

Pretty much my take as well. It's one thing if you're presenting a case to someone who's on the fence. Quite another when you're bickering with (or ostracizing) someone who doesn't want to listen. I'm not above debunking someone who's putting out false information, but I'm not the type to argue with people just because they don't believe what I believe. Best, -Slashy

Bandus, If I were to design a lifter for that payload it would look like this: http://wikisend.com/download/962642/MAGDY EnviroSat Mk3.craft Improvements... I designed the Mk3 lifter mathematically before I built it. Upper stage was the lightest solution for a minimum acceleration of .7G, 2.2t payload, and 1,800 m/sec DV. Lower stage was the cheapest solution for 5.6t payload, 1.4G minimum acceleration, and 1800 m/sec at 50% average atmospheric density. It's amazing what you can do when you flip the rocket equation backwards AFA how I was able to work with your lifter... I left the throttle at 50% and handled it very carefully with the SAS turned off. As Harry Rhodan said, it has way too many reaction wheels, active gimbaling, and active fins. I launched it vertically at 50% throttle until it hit 90 m/sec, then mainly steered it through the prograde gravity turn by modulating the throttle. Best, -Slashy

Bandus, I just downloaded your problem child and fired it up. 1) First issue is it's way over- powered. It's hitting 3G off the pad and that will make it tough to control in a hurry. 2) The upper section is crazy- wobbly over the boosters. It flies like Lamar's javelin in Revenge of the Nerds. You'll have to tone down some of the control responses to iron that out or find the weak point and shore it up. Nevertheless, I was able to orbit it with fuel left in the central booster stage. I think it's a lot more rocket than is actually needed for this job. Best, -Slashy

RIC, I'm sure this is the case as well. Executing multiple Apoapsis kicks can maintain high efficiency with ridiculously low t/w ratios, but working out timing for transfer windows gets ugly in a hurry. Errors in timing the transfer add a whole other source of inefficiency. I'm afraid it all gets subjective at this point Best, -Slashy

Der Anfang, What YNM said. You know what the angular velocity is for both bodies in circular orbit and you can easily calculate the transfer using the Vis-viva. The tricky part is knowing the precise angular separation in KSP. For problems like that, I use periodic orbits so that the longitude of a body is a function of time, but as a practical matter I'd simply use the maneuver node. Dial in the prograde to match the target apoapsis, then drag it around my orbit until I have an intercept. Is there some reason that's not an option? Best, -Slashy

OhioBob, This is why I design my vacuum missions with a minimum acceleration of .5G. I've noticed that the DV budget grows exponentially below that. Best, -Slashy

Xannari Ferrows, I can answer this accurately enough. It was simply cold war politics. The Soviets launching Sputnik scared the crap out of the American people and there was a lot of nuclear tension at the time. The Soviets were way ahead of us in this area and we wanted to show that we could "beat them" at something. The only endeavor we thought we could get to first was a manned moon landing, so that's what we did. That's why we did it. Best, -Slashy

Sampa, Thanks, but that's not the question I'm asking. I know why we went to the moon and why it was important (or at least why we thought it was important at the time). My question is why would it be important to us as individuals to make sure that other individuals don't subscribe to conspiracy theories? If Joe Blow believes the moon landings were a hoax, what's it to me? Why should I convince him otherwise or even care what he believes? Best, -Slashy

FungusForge, The AoA lift and drag charts are in there. They're referenced by sinô rather than angle. Best, -Slashy

FishInferno, "Shun the non- believer" isn't a very rational argument IMO. This raises a question: Why is it important to any of us whether or not somebody else believes the moon landings actually happened? Best, -Slashy

Right, I don't know if anybody's made them yet, but it wouldn't be difficult. DRAG_TIP { key = 0 1 0 0 key = 25 1 0 0 } DRAG_SURFACE { key = 0 0.02 0 0 key = 0.85 0.02 0 0 key = 0.9 0.0152439 -0.07942077 -0.07942077 key = 1.1 0.0025 -0.005279571 -0.001936768 key = 2 0.002083333 -2.314833E-05 -2.314833E-05 key = 5 0.003333333 -0.000180556 -0.000180556 key = 25 0.001428571 -7.14286E-05 0 } DRAG_TAIL { key = 0 1 0 0 key = 0.85 1 0 0 key = 1.1 0.25 -0.02215106 -0.02487721 key = 1.4 0.22 -0.03391732 -0.03391732 key = 5 0.15 -0.001198566 -0.001198566 key = 25 0.14 0 0 } DRAG_MULTIPLIER { key = 0 0.5 0 0 key = 0.85 0.5 0 0 key = 1.1 1.3 0 -0.008100224 key = 2 0.7 -0.1104858 -0.1104858 key = 5 0.6 0 0 key = 10 0.85 0.02198264 0.02198264 key = 14 0.9 0.007694946 0.007694946 key = 25 0.95 0 0 } DRAG_CD { key = 0.05 0.0025 0.15 0.15 key = 0.15 0.0225 0.3 0.3 key = 0.25 0.0625 0.5 0.5 key = 0.35 0.1225 0.7 0.7 key = 0.45 0.2025 0.9 0.9 key = 0.55 0.3025 1.1 1.1 key = 0.65 0.4225 1.3 1.3 key = 0.75 0.5625 1.5 1.5 key = 0.8 0.66 2.3775 2.3775 key = 0.85 0.8 2.733777 2.733777 key = 0.9 0.89 1.1 1.1 key = 1 1 1 1 } LIFTING_SURFACE_CURVES { LIFTING_SURFACE { name = Default lift { key = 0 0 0 1.965926 key = 0.258819 0.5114774 1.990092 1.905806 key = 0.5 0.9026583 0.7074468 -0.7074468 key = 0.7071068 0.5926583 -2.087948 -1.990095 key = 1 0 -2.014386 -2.014386 } liftMach { key = 0 1 0 0 key = 0.3 0.5 -1.671345 -0.8273422 key = 1 0.125 -0.0005291355 -0.02625772 key = 5 0.0625 0 0 key = 25 0.05 0 0 } drag { key = 0 0.01 0 0 key = 0.3420201 0.06 0.1750731 0.1750731 key = 0.5 0.24 2.60928 2.60928 key = 0.7071068 1.7 3.349777 3.349777 key = 1 2.4 1.387938 0 } dragMach { key = 0 0.35 0 -0.8463008 key = 0.15 0.125 0 0 key = 0.9 0.275 0.541598 0.541598 key = 1.1 0.75 0 0 key = 1.4 0.4 -0.3626955 -0.3626955 key = 1.6 0.35 -0.1545923 -0.1545923 key = 2 0.3 -0.09013031 -0.09013031 key = 5 0.22 0 0 key = 25 0.3 0.0006807274 0 } } LIFTING_SURFACE { name = BodyLift lift { key = 0 0 0 1.975376 key = 0.309017 0.5877852 1.565065 1.565065 key = 0.5877852 0.9510565 0.735902 0.735902 key = 0.7071068 1 0 0 key = 0.8910065 0.809017 -2.70827 -2.70827 key = 1 0 -11.06124 0 } liftMach { key = 0.3 0.167 0 0 key = 0.8 0.167 0 -0.3904104 key = 1 0.125 -0.0005291355 -0.02625772 key = 5 0.0625 0 0 key = 25 0.05 0 0 } drag { key = 0 0 0 0 } dragMach { key = 0 0 0 0 } } LIFTING_SURFACE { name = SpeedBrake lift { key = 0 0 0 0 } liftMach { key = 0 0 0 0 } drag { key = 0 0.01 0 0 key = 0.3420201 0.06 0.1750731 0.1750731 key = 0.5 0.24 2.60928 2.60928 key = 0.7071068 1.7 3.349777 3.349777 key = 1 2.4 1.387938 0 } dragMach { key = 0 0.35 0 -0.8463008 key = 0.15 0.125 0 0 key = 0.9 0.275 0.541598 0.541598 key = 1.1 0.75 0 0 key = 1.4 0.4 -0.3626955 -0.3626955 key = 1.6 0.35 -0.1545923 -0.1545923 key = 2 0.3 -0.09013031 -0.09013031 key = 5 0.22 0 0 key = 25 0.3 0.0006807274 0 } } } The curves that end at 25 refer to Mach and the curves that end at 1 refer to atmospheric density. Best, -Slashy

Honestly for me the "learning how" is the entire point of KSP. How many folks here would understand rocket science as well as we do if it wasn't for this game? Best, -Slashy

RainDreamer, Dreams are a very fascinating manifestation of the wiring of your brain. Here's the way I think of it: Your brain is actually composed of several subsystems, and dreams come from the "lizard- brain" that rules your emotional responses. When your lizard- brain is wrestling with a problem that it's unhappy with, it will occasionally babble incoherently about it and flag it "urgent". Your human brain will then take these babblings and attempt to transcribe them into something it understands by assigning symbols to them (situations, objects, and actions). You *personally* know what these symbols represent to you, so it's often possible to assign meanings to them and puzzle out the message. The key is that your interpretation is yours alone. You assign emotions to symbols that are unique to you in your situation, so nobody else can decode it for you. So at the risk of sounding overly- guru-ey, this question is one that only you can answer and you *do* have the answer. What are the major stressors in your life? How do you feel about the symbols in this dream? How do the feelings and symbols relate to the stressors? Once you sort that out, it's fairly easy to decode the message. It's usually something along the lines of "I'm worried about such- and- such problem, and I'm not dealing with it in a productive manner". Best, -Slashy