GoSlash27

KSP Version: 1.1.0.1230 (x64) What Happens: Vehicles with fixed landing gear collide with terrain, skittering on the surface Mods / Add-Ons: n/a Steps to Replicate: Build a craft with fixed landing gear, launch. Result: Vehicle skitters on surface, cannot stop. May flip and crash. Fixes/Workarounds: None known. Should I just not try to use x64 for now? *edit* Same thing happens with the standard KSP game. Best, -Slashy

I'm just now downloading and installing 1.1, so this answer may be incorrect. In KSP 1.05, tech level 6 was sufficient to achieve orbit in a practical spaceplane. That's using the Panther, nacelle, and LV-909 or Poodle. Unless something's changed, that should still hold true. Best, -Slashy

Nich, Well... the fact that SRBs are cheaper is why we use them. As for the t/w, you're not liable to ever build a lifter with such dismal t/w that lighting a vacuum engine is going to improve matters. You see, the fuel consumption is constant. It's the *thrust* that varies with Isp, so the vacuum engine isn't adding much thrust... but it's going through a lot of fuel. The break- even point comes when the vacuum engine achieves the same Isp as the SRB. If the goal of lighting an engine on the pad is to save weight, then lighting an engine with poor Isp is actually counterproductive, because you have to add fuel for it to waste. The ship actually weighs *more* than it would've if you'd left the engine turned off. Best, -Slashy

Nich, I'm not sure which part you need the math for, so please pardon my response if it's overkill. The point of lighting engines off the pad is so that you're not carrying them as dead weight. If you do this, you can use a little less SRB and save some overall mass/ cost on the launch stage. In order for this to save any weight, the mass of the fuel expended by the lit engine must be less than the mass of the propellant that would've been expended by an equivalent SRB. This gets into the other side of Isp that we don't talk about as much. Isp*g0= exhaust velocity in m/sec ; "Ve" T= thrust in kN m'= mass flow rate in kg/sec m'=T/Ve m'*t= mass of fuel expended during launch. So as you can see, the lower the Isp, the higher the mass of fuel must be expended to produce the same thrust for the same period of time. If you're using an engine with a *worse* Isp than a SRB, it will require more fuel than the SRB would have needed to do the same job. This erases the benefit of lighting it. The Isp of a vacuum engine doesn't catch up to a SRB until around 3500 m altitude, so it's not worth lighting it before then. You can confirm this yourself by building a parallel staged booster with a vacuum core engine. Launch it first with the core engine lit, then try again with just the SRBs, turning on the core engine at 3.5km. The second run will leave you with more gas in the tank. Best, -Slashy

ibanix, Here's a cheap design that's good for 135t to LKO: http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/CnCRocketFactory/Cheep135 Best, -Slashy

the_pazter, Kerbin's sidereal period is 21,549.4 seconds. The period of a semi- synchronous orbit is 10,774.7 seconds. The formula for radius (or SMA) based on period is r= cuberoot(up2/4π2) r= 2,181,745 m This is radius from Kerbin's center, so altitude would be 1,581,745 m Best, -Slashy

^ And as an addendum, vacuum engines should never be staged right off the pad, even in a setup 5thHorseman describes. Their Isp is even worse than SRBs down there, so they waste more mass than is saved by turning them off. They break even around 3.5 km. Best, -Slashy

Well, if it doesn't then @Stoney3K May just have to work around the limitation. I generally use surface mount solar panels and perhaps an add-on battery. One could also use a fuel cell. Best, -Slashy

Does it have an alternator, though? I can't find a source that says it does. Best, -Slashy

Came looking for this, left satisfied -Slashy I tried that once. I was forced to spend a year dead for tax purposes

I like 1800 m/sec in the first stage. It may not be the most efficient staging point in terms of raw DV, but it allows staging to occur above 25 km. This means I don't have to worry about aerodynamic issues with the second stage. Best, -Slashy

John JACK, Oh, definitely no offense taken. I'm just trying to clarify what my argument is on the matter and what it is not. I never made an argument for 1.875m hardware on economic grounds. That's not to say that I disagree with the point, mind you... FungusForge, Again... I never said that. Not that I disagree, but it's not why I think we should have 1.875m boosters. I just want them because the 1.25m boosters are undersized for shuttle/ SLS replicas. So in this matter, it's more accurate to say that "I gotta agree with you" rather than the other way 'round. Best, -Slashy

John JACK, Lifter cost per tonne is definitely important to people who play career, but KerikBalm was the one who mentioned it in this thread. Best, -Slashy

Actually, It was *much* lower than that. the OP stopped maintaining the leaderboard. The best entry got under $600/tonne. Also, the first iteration of the competition required placing the payload fully in orbit, but those rules took the focus away from booster design. The difference between that and full orbit is 45 m/sec DV. Even if your argument is correct, the Buran still requires 1.875m boosters, so.... Best, -Slashy

The Buran doesn't use SRBs. We're talking about SRBs... Completely off- topic, but there's lots of fully disposable lifters under $700/ tonne here:

IIRC the only launch of the Buran/ Energia was at night in poor weather. This was also during the cold war, when the Soviets were actively trying to hide the details of their activities. I'm not surprised that no high quality images exist. Best, -Slashy

1) 100% stock 2) Don't kill Kerbals 3) Don't litter. 4) Do it cheaply and efficiently.

Actually, yeah... I think it does. As long as we have a shuttle cockpit, shuttle cargo bay, shuttle wings, shuttle tail, etc. etc. we oughtta have the parts to build a shuttle stack that looks like a shuttle stack. Trust me... we are all aware that we *could* build a STS with an undersized tank, 4 undersized SRBs, and a Rhino in the back if that's what we wanted to do. That's not really the point. Best, -Slashy

Oh, my apologies then... I'm sure, but it appears to me that Squad is adamantly against implementing procedural parts, while they're not averse to adding new parts. If the stock game implements procedural parts, I'll happily use them with a vengeance -Slashy

4b) BadS="True", period! I love to use orbits that appear overhead KSP on a regular schedule whenever possible. My favorite is the 36 minute schedule, which passes overhead KSC 10 times a day. Since Kerbin rotates 1 time per day itself, this means our orbit will need to occur 11 times per day in the sidereal frame. Kerbin's sidereal period is 5 hours, 59 minutes, 9.4 seconds. That's 21,549.4 seconds. Our desired orbital period would therefore be 21,549.4/11= 1,959.04 seconds. r= cuberoot(up2/4π2) r= cuberoot(3.433x1017) r= 700,212 m Subtracting Kerbin's radius leaves an altitude of 100,212m If we put something into this orbit, we will know precisely when it will appear overhead KSC simply by looking at the clock. It will pass overhead once every 36 minutes. Not only that, but we will know precisely where it is in it's orbit around Kerbin at any given time. It's always moving East at 10° per minute, 1° every 6 seconds. If we mark it's passage overhead KSC, we know where it is simply by the clock on the wall. This allows us to use launch windows to intercept stations in this orbit from KSC, pinpoint the longitude of interesting landmarks on the ground, use windows to set up resonant transfer orbits and intercepts for the Mun and beyond.

John FX, In most cases I'd agree with you, but... PorkJet went to the trouble of giving us realistic "lego blocks" we need to construct a STS replica. The only thing we're missing is a properly sized SRB and big orange tank to go with it. It seems a shame to me that we don't have those parts. ^ Undersized SRBs, apollo-style tank, and overpowered LF engines. Besides... The SLS architecture is heavily- based on the shuttle hardware. If we're going to model that, we'll need the right SRBs. Best, -Slashy

^ This. If calculated to high precision and adjusted for sidereal rotation, the actual DV to orbit is 580.6 m/sec. Apologies for taking a couple days' hiatus from this. There's a lot more material to cover. Best, -Slashy

DStaal, If you eject the scanners at the mid-point of the interplanetary transfer, the DV required to get them polar vs. equatorial will be so slight as to be inconsequential. You can adjust with tiny burns to get a polar intercept, then barely close the orbit either by retroburn or aerobraking. If you leave a high Ap, corrections to the inclination will be very cheap when you reach Ap because your velocity will be so tiny. Finally, circularize the polar orbit either by aerobraking or retroburning. Good luck! -Slashy

OhioBob, I thought about how to convey uniform circular motion in a technically correct way, and I can't figure out how to not make it confusing. The reason the satellite maintains it's altitude is because it's got enough horizontal velocity to "miss" the surface, but it's difficult to put into a simple picture and explain the math. So even though I know that invoking "centrifugal acceleration" isn't technically correct...I'm afraid I'm going to have to keep it for this tutorial because it's an easier concept to grasp and the math still works. Plus (and I know this is extra-silly)... the pictures are more clear and intuitive with the arrows going the wrong way. If you can come up with a graphical and mathematical representation of what's really going on, I'll be happy to plug it in there. I know I suck -Slashy

4) Applied single- body mechanics 4a) Jeb launches from the Mun! Launching from the surface of an airless body requires 4 distinct phases: 1: Burn horizontally (without losing altitude) to establish orbit at sea level 2: Burn horizontally to get enough velocity to establish your desired apoapsis 3: Go eat a snack until you reach apoapsis, and 4: Burn horizontally at apoapsis to circularize your orbit. For step 1, we must figure out what velocity would put us into a circular orbit at sea level. The Mun's mass is 9.760x1020 kg and G is always 6.674x10-11, so u = MG = 6.514x1010. Our sea level orbital velocity would be sqrt(u/r) and the Mun's sea level radius is 200km. 6.514x1010/2x105=3.257x105 sqrt(3.257x105)=570.7 m/sec. For step 2, we must define the SMA of our transfer altitude. Let's say our desired orbital altitude will be 14km. This means our Ap will be 14km plus the Mun's sea level radius of 200km =214 km. Our periapsis will be sea level, or 200 km. Our SMA will therefore be (214+200)km/2=207km Our velocity at periapsis in this elliptical transfer orbit is defined by the vis-viva equation. Vpe=sqrt[u(2/Pe-1/SMA)] Vpe=sqrt[6.514x1010(2/2x105-1/2.07x105)] =sqrt[6.514x1010(5.169x10-6)] =sqrt(3.367x105) Vpe=580.3 m/sec We will lose speed as we sit there eating snacks, so we need to know how fast we will be going when we reach Apoapsis. This is figured the same way as we did Vpe. Vap=sqrt[u(2/Ap-1/SMA)] I'll skip the figuring this time. Vap=542.3m/sec Finally in step 4, we need to increase this speed to a proper speed for orbit at Ap; 214km. This is figured the same as step 1. Vorb=sqrt(u/r)=551.7 m/sec. So we started at zero. We increased our speed to 570.7, then increased it further to 580.3. Our speed dropped to 542.3 as we coasted, and finally we boosted it to 551.7 m/sec. Our total change in velocity was 580.3+(551.7-542.3) m/sec, or 589.7 m/sec. Since the Mun rotates clockwise at 9 m/sec, We could subtract that if we launch East, yielding 580.7 m/sec DV. This is the DV required to reach orbit from the Mun.