GoSlash27

Laie, The proof would be in execution. If you actually place a satellite in orbit at 300km and set up a transfer burn to Jool, You'll find that it doesn't actually save DV compared to 70km unless you retroburn to reduce Pe first. Best, -Slashy

Laie, the amount of kinetic energy you end with will be the same regardless. What matters is how much kinetic energy you have to add to get there and thus how much kinetic energy you start with. Starting at low altitude gives you more kinetic energy to start with due to your higher orbital velocity. Starting at higher altitude gives you more potential energy, but less kinetic energy. There are a couple important equations left out of the write-up. The one I suspect is in error is escape velocity as a function of altitude. I suspect that this chart is roughly accurate *if* it involves an initial burn to lower Pe followed by the transfer burn (what Hotaru refers to as the "Oberth maneuver". We had a really good write up on this subject a few months back. I'll see if I can dig it up. Best, -Slashy

OhioBob, In addition to needing more DV to achieve the higher orbit, I also need to point out that orbital velocity is lower at higher altitudes. The Oberth effect exists because kinetic energy is what actually gets you from place to place and DV is a nonlinear measure of it. since Ek=1/2*M*V^2 involves the square of velocity, a change in Ek is proportional to (V2-V1)^2 where V1 is starting velocity and V2 is ending velocity. (V2-V1)^2= (V2-V1)(V2-V1)= V2^2-2V1V2+V1^2. Starting the burn at a higher V1 means that a change in velocity will add more kinetic energy than a burn at a a lower V1. Best, -Slashy

ChiefJohnson, No, it's not quite that simple. I didn't show the entire process. The entire process would be 2.8 tonnes of not- fuel and 2 tonnes of fuel. 4.8/2.8= 1.71 Rwd. The natural log of 1.71 is .536 .536*9.81m/sec2 (standard g0)*320s (the engine's Isp) = 1,683 m/sec DV So while it's not quite that simple, it's not really complicated either. What I find really useful about the rocket equation isn't this form, but instead it's backward form. instead of 9.81Ispln(Rwd)=DV which says what the thing you have built can do, working it backwards e^(DV/9.81Isp)=Rwd which says what you need to build to do what you want. The first form is a good spot check of what you have already built. The second form is used to design your ship so it'll do what you need. If you get handy with this equation, you don't need an add-on and don't have to worry about being misled. If you get *really* slick, you can build a spreadsheet that will do your designing for you and tell you at a glance which design is cheapest or lightest for what you're trying to do. Best, -Slashy

LordFerret, I can't compare it to Falcon 4.0 since I've never flown it. I was strictly a naval aviation guy. A lot of the other pilots compared it to the A-10 Warthog sim favorably. Superbug combined with Tac- Pack is far and away the most faithful reproduction I've ever seen. It can be flown IAW the actual NATOPS for the type and performs as predicted. It even models failures from incorrect operation. Best, -Slashy

I always do LKO first if I'm rendezvousing with something. If it's just a plain ol' sat contract, I launch right into it. Going to LKO first costs some DV (usually marginal) but gives a lot of flexibility. Shooting direct saves some DV, but it demands a tight launch window. For spaceplanes... I go to LKO first every time. They take longer to get to orbit, so there's more variation in their time to orbit. This means it's less likely you'll launch directly into a rendezvous. Best, -Slashy

^ What Padishar said. There's no way 1.78t accounts for the engine, empty tanks,decoupler, crew module, and additional stuff. It would account only for the engine and empty tanks, so MJ must assume that the decoupler is the payload. I can't come up with an accurate figure without an idea of how much all that stuff above the crew module weighs, but it looks like at least another tonne. If that's the case, it's 2.8 tonnes of not- fuel and 2 tonnes of fuel. 4.8/2.8= 1.71 Rwd. That would yield 1,700 m/sec (assuming this is an LV-T45), which won't make orbit. And honestly it's probably heavier than that. The moral of the story: Never assume that MJ figures are correct. It's fine to use it as a sanity check, but you should compute the DV yourself (or with a spreadsheet). How are you set for monoprop? If you have enough, you might be able to use it to circularize. Best, -Slashy

Tex, I've never used any control other than the numpad + and - for zoom. Best, -Slashy

LordFerret, This was several different pilots working with Superbug before TacPack was released. We had modeled Mk.82s with retarders and daisy-cutters for this shoot. You can drop those right down on the deck. The drops with the CCIP pipper were remoted from my ship. Not all of the pilots had worked out the full avionics suite at that point. Best, -Slashy

Right, It's related, but much more loosely. The main source of DV loss in spaceplane design is drag, so there is an advantage in designing a spaceplane to be aerodynamically cleaner. So how does lift help? Well... There are 2 kinds of drag in KSP; induced drag and parasitic drag. Induced drag is a by-product of creating lift. Parasitic drag is the result of pushing a mass through the air. It so happens in KSP that wings only produce induced drag while everything else produces parasitic drag. It also happens that induced drag is *much* lower than parasitic drag in KSP. Using wings to create your lift instead of structural panels, body lift, or raw thrust means that you will create dramatically reduced drag during the launch. This means less DV wasted to drag and cosine losses, which means less DV required to achieve orbit. Best, -Slashy

Ooo... FSX screen shots? I've got some! I actually planned and led this strike (K6952) /Superbug rocks! More goodies: I'm #2 on this shakedown of the FSX Blue Angels Hornet Carrier traps with various aircraft Best, -Slashy

Also... When he was stripping the MAV and chucking stuff overboard I visibly winced. Especially when he wrestled the airlock overboard to tumble down the side of the stack . All I kept thinking about through that scene was http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543 Best, -Slashy

ibanix, Yeah, which is why I said "almost never". That was also one of the most endearing moments in the film. I think it needed more of that and less "everything's conspiring against me, but I always know what to do". Best, -Slashy

One gripe I have is that Watney's self- inflicted setbacks were almost never covered. This was part of the charm of the book that I think was missing from the film; Watney screwed up as often as not, but never gave up. The movie portrayed him as a guy who always knew what to do and this made him a little less relatable IMO. Best, -Slashy

A mechanical or electronic barometer isn't going to be sensitive enough to register such low pressures, but a pressure column could do it. You would have to keep it vertical and not jostle it around too much. Just set up a scale next to the column and take pictures every now and then. Also, the fluid doesn't have to be mercury. You just want something that will remain fluid throughout the flight. I think ethylene glycol (automotive antifreeze) would do nicely. Best, -Slashy - - - Updated - - - ^ "Export restriction mode". I had a run- in with that once. If your cell phone exceeds 60,000' altitude, there's a better than even chance 100% certainty that it will refuse to track it's location via GPS for at least 15 minutes. You might lose the whole thing if you don't have a backup plan. Best, -Slashy

It was thoroughly enjoyed by my nerd- gaggle. Thinkin' about it... Anybody who's reading the KSP off-topic forum is *going* to see this movie, so there's not much point in reviewing it. Best, -Slashy

Also a shameless plug: http://forum.kerbalspaceprogram.com/threads/102809-The-reverse-rocket-equation-explained Best, -Slashy

I'm running Windows 7. Other than that, nothing odd about my setup I can think of. *edit* Moesly Armlis' trick seems to work for me. If I go straight to the VAB and look it's not there. If I load a vessel, send it to the pad, and then revert, it appears. Best, -Slashy

You know... NASA is a government agency, not a for- profit enterprise. They will not put an unnecessary payload on an exploratory mission just because you want it there, even if you can pay for it. *BUT*... If it's for educational purposes and has enough political backing, they will not only do it, but they'll do it for free. If this were done as part of an initiative to promote STEM education in America with the backing of a few key senators and congressmen, it could be done without raising any money at all. Best, -Slashy

I disagree. If it were that simple, pure market forces would hold sway and we'd have dirt- cheap launchers with a decent chance of success. Companies pay these agencies to "deliver" their packages to orbit. Insurance is expensive and the whole business model hinges on an agency's ability to deliver the payload 1) reliably and 2) cheaply. In that order. Reliability is many times more important when human lives rely on the success of the mission. Optimizing for cost while skimping on reliability is theoretically good, but nobody's willing to pay to take that risk. This holds true even in the more mundane world of ground shipping. For inconsequential packages, it's probably fine to go with a cut- rate method with an iffy chance of success, but people will pay a premium when they want to be sure of delivery. Best, -Slashy

I read the spoilers and I take full responsibility for that. A couple of them, I'm mighty disappointed about, but it's a movie and they have to keep the pace up. Gonna see it tomorrow with my nuclear nerd- gaggle. Best, -Slashy

Alternatively, a radial burn can adjust both simultaneously. If you're mid- way between Pe and Ap, a radial burn will adjust both at the same time. If you're climbing from Pe to Ap, a radial in burn (pointing straight down) will raise your Pe and lower your Ap at the same time. If you're descending from Ap to Pe, a radial- out (pointing straight up) will equalize them. I use a mix of throttle and radial along with my prograde burn to make nice circular orbits from launch. Best, -Slashy

nothalogh, No, it's not stupid. It's got high caloric content so it'll burn. Lots of problems with it, though. It's not going to want to flow or atomize well and will gum up the piping. Best, -Slashy

Actually... I have to swing the other way on this. They are far from perfect for what they are. The object lesson they currently convey is "a .90 craft doesn't work in 1.04" and everybody knows that. A properly designed stock craft for 1.1 would be close to working, but have a flaw that can be repaired with a good knowledge of 1.0 physics. Best, -Slashy

^ I'd agree with both posts above. They're not necessarily mutually exclusive. I think we could have community- designed stock craft, then have somebody "break" the final version in such a way that it can be fixed. Best, -Slashy