wumpus

I knew it was tidally locked, but forgot all the implications. Also while I've always found the "western horizon" to be when to burn, I'm not sure why. I feel you should be killing as much of your orbital velocity wrt to Kerbin, but I've done much better with a burn away from Kerbin (from orbit). You also don't need full orbit, suborbital will likely do (circularization burns don't help you get back to Kerbin at all) assuming you are on the "right half" (halfway around would justify orbit. I'd want less than 1/3 and ideally 1/4 of the way around to try a suborbital) of the Mun to get away with this. You just need to be traveling over the horizon of the Mun so you can set up a maneuver node home. Note that the ideal place for you maneuver node is as low as possible (for Obereth effect), presumably roughly near apogee (this isn't all that important, but don't be coming down fast) and most importantly have time to set it up and execute the burn. Best guess is that if you need to go fully into orbit, you already know you aren't going to make it home (how low were the orbits you were trying? You want them as low as possible, and try to put the maneuver node home where the orbit of your ship intersects the orbit of the Mun (see above) where the vessel is heading toward Kerbin. You might have to adjust the maneuver node a little, but it is close to there). Just get into a high orbit and wait for a rescue ship.

If you read to the end of the paper, you will note that it is a solution in search of a problem. The whole point of providing a spaceplane that can takeoff and land in most airports in the world is to provide a plane for suborbital hops. The catch is that suborbital flight requires only 3/4 of the fuel loaded up, while a vastly more common trip 1/4 around the world requires only 60% of the fuel. One key that the authors aren't remotely serious is that they never make the obvious decision to take off with all necessary H2O2 (which was slightly more than the dry weight of the spaceplane. Having an unmodified fueling plane plus only a single system of re-fueling would presumably lower logistics costs tremendously (H2O2 is an incredibly caustic, although probably not nearly as nasty as LOH, you would want to avoid refueling with it and keeping it out of your refueling planes if at all possible). I also suspect that they are really pushing the numbers of the dry weight of the spaceplane. With SABRE (and a free flight up to mach 5.5) you need 184,250 lbs of fuel. With a standard SSTO rocket, (cheating by using the same dry weight), it only takes 224,250 lbs of methane (hyrdrogen's density means the numbers won't line up at *all*) to go from 0-orbital (cheating again by ignoring drag (worse for so small a craft)). Do you really think you can get 3 passengers into orbit on a SSTO *smaller* than a Falcon? Oh yes, in case you missed it: 184,250 lbs of fuel (and note that due to H2O2's listed cost, it should cost twice that in lbs of kerosene to the buck) for 440lbs of passengers. Seriously expensive flight, even with "thousands of Skylons". Don't forget to pay for the entire crew of the fueling plane and all the pre/post flight maintenance.

This is a leftover from the broken aero model of <1.0. To leave the souposphere, you would throttle your engines down to terminal velocity for maximum efficiency. The current aero model is much closer to reality (although I assume that FAR is still somewhat better). You best bet is to simply lift off with TWR between 1.3 and 2.0 (preferably closer to 1.7) and let the rocket gain TWR as it burns fuel. Note that if you take off with a high TWR, you will probably need another high TWR second (insertion) stage as the time between the end of the first burn and apogee won't be all that long (high TWR lends itself to steeper trajectories). * Note that for subsonic speeds, there really isn't such thing as "too high a TWR". It's just that it suddenly becomes inefficient in a few seconds (and thus a bad idea to bring an oversized engine on the rest of your flight). If you really need to do such things, it is possible to recover "0-stage" boosters in stock KSP that are ejected under a few km. Expect to spend a great deal of time tweaking parachute parameters, tuning aerofins (expect to have tiny SRBs stopping the booster in flight and pushing it back to the launchpad). I can't image it being worth your time, but I did manage to do it once.

Except that burning straight up is going to be inefficient (you might get away with it on Minmus, but Mun is a harsh mistress). Basically you are throwing away 1/TWR (for munar weight) of fuel. What you really need is to wait until Kerbal is overhead and firing horizontally away from the Mun's rotation (of Kerbal. Mun is tidally locked and doesn't rotate so which side shouldn't matter). You still want to do a single burn, and keep burning until your perigee stops decreasing. Hopefully, you will still have enough fuel to set up a maneuver node that will get you into the atmosphere. If it is still close enough, you could get out and push, but that is *slow* and only works if you are really close (I'm hoping a single burn will get you there). If not, your best bet is to make a circular orbit as high above the Mun as possible and as circular as possible. If you care about calendar time, you might want to install kerbal alarm clock and send a Duna/Eve probe during this time, as docking in high Munar orbit is kerbal-time slow (faster and easier in human-time, but expect to be abusing time-acceleration. So slow in kerbal-time).

Looks like installing Kerbal alarm clock is overdue. Hopefully, someday squad will allow maneuver nodes for a landed ship (hopefully it is a Unity 4 thing, since mods can't seem to touch it, and will quickly disappear).

You know how some posters have mentioned that you ignore the big picture to include your favorite details? Here's a hint: there is simply *no* *way* you are getting a SSTO that uses H2O2 as a fuel (note that it won't even if you use an oxidizer, and your post implies a monopropelant which is absolutely hopeless). There is no excuse for complicating the launch of a vessel that has turbojet engines just to get 250 or less m/s. It will have enough problems with the issues that are handwaved away once it switches to "rocket mode", if it can't solve the 0-mach 6 issues on its own there is no possible future for SABRE.

That really kills the "gas and go" idea. Of course, the whole logistics of integrating a second stage with the first has always been far more than "gas and go", but expect a lot more work.

Did the shuttle ever run satellite recovery runs? While it seems to be designed to bring back a spy satellite (pretty much the only reason for half the design silliness), it never took off from Vandenburg, so presumably never entered a polar orbit and never launched or recovered spy satellites (presumably they would mention bringing back non-spy satellites). It did service the Hubble, but nearly all that available downward cargo was wasted all 100+ trips (the internal space laboratory presumably used the space and did come back down, but that could never justify the downward mass.

The problem isn't unplanned explosions. The planned explosions are bad enough (and need to be in the anarctic for minimal damage). "Plastic explosive lens": sounds like tech needed to make an Orion work properly (or at least without a ton* of plutonium) that didn't pan out at the National Ignition Facility. Obviously "we" (for values of humans with DOE/DOD assistance, or Russian equivalent) could build an Orion with plutonium detonators, but I'm wondering what these "plastic explosive lenses" are and if they have been shown to work. * might even be literal. Consider just how much plutonium is needed per [H]bomb and how many an Orion will need. This should definitely keep Orion on the ground purely on nuclear proliferation grounds (unless you can set of an H-bomb with lasers or similar).

Has anybody asked about how in the world they are going to repair the satellites? The only time this has ever been done is on Spacestations (pretty much full time towards Mir's end of life) and on the Hubble. All of which was done by humans. Are they sending a robot? Has anybody asked Goddard (or some other big satellite assembly location) about letting a robot play with their satellites (even in a gravity field)? It sounds like it is asking for trouble (refuel I could believe. Judging by what the Hubble repair involved, I don't believe robots are doing that any time soon). Scott Manley has a semi-recent tweet stating that "space station freedom" was originally pitched as a satellite repair location, but that it was impossible due to delta-v issues. Was that due to the ISS requirement that it have an inclination favorable to Kazakstan, or simply that the range of useful orbits even from KSC (and maybe Wallops) is just too wide to deal with (assuming "space station freedom" was launched to a maximum equatorial angle for the equinox (which is as good a place as I can imagine for a Florida-based repair depot). Finally, orbital most certainly is in the rocket reuse business, and has been longer than space-x. Its just that their idea of reuse is to take cold-war era surplus and integrate them into rockets capable of firing into space (like ULA/NASA (and the Russians) have been doing since day one, but with actual sitting-in-a-silo-for-years ICBMs). They might only get fired once, but they are being reused.

Of these, only SETI bothers to mentions how contracts work with the new tech tree (and recommend less money for the same thing, presumably more grind). SETI also looks like what you want, and is based around the idea of "unkerballed before kerballed". CTT sounds impressive assuming you want to work in a lot of mods, while ETT sounds like a more logical system (engineering wise). This type of things sounds obvious for a science career, but working into the current contracting scheme may involve some painful grinding. Most of the systems (especially CTT) center around endgame, not so much deciding to do an Apollo-style landing vs. a direct descent. - note: while command chairs might not be anywhere near early enough, I encountered a bug that didn't like vessles that had kerbals in command chairs (with octoprobes but no capsules). Couldn't save, couldn't see the vessel on the map (but could see the orbit and target nearest approach). Command chairs appear to be the best way to approach building a separate lander, but might be buggy.

KSP. Revert early, revert often and boldly (as boldly as you can while hovering over F9) go where no kerbal has gone before.

I was looking at it and suspecting a logical progression of Munar orbital science lab, polar Minmus science lab, polar Munar science lab. I thought about it, then decided that it probably made more sense to send two science labs to Minmus and simply abandon one when it is full and fill up the second with another round of Minmus data. I would assume a suborbital (with powered landing) will be at least 560 m/s (maybe better if you do a "travelling salesman" routine to the 15 biomes). I'm guessing this is a mech-jeb only strategy (of course, I have no hope of landing a polar Minmus observatory with constant kerbollight without mechjeb). Even simply hitting all biomes and returning (without the lab) would likely require mechjeb (at least for me).

I'm pretty sure the car in question had fuel injection. Probably OBD-II (if not, certainly OBD-I) compliant. It might significantly more efficient over carburetors, but they don't really appear to have much chance at getting better. One of the big problems is that most of the few remaining ways to increase efficiency do so at the expense of emissions. Running a bit lean will increase power for the same amount of gas, but also create a bunch of nitrogen-oxygen compounds. Honda used to sell cars that would do this (with three different catalysts to break things down), but I'm not sure if that is even possible with current (US) standards. My understanding is that the current thought is to use much smaller engines (like most hybrids) to move the "sweet spot" down to where the car is typically used, then allow the turbocharger to produce (with horrible efficiency) more power when [rarely] needed. This works fine as long as you drive like the official standards (or more efficiently), but lead footed drivers whine all over the internet. It also isn't quite as effective as a hybrid, but is typically much cheaper to build (I'm still wondering why Toyota hasn't made a Lexis that marries a prius engine with a more powerful (not quite Tesla, but you get the idea) electric engine).

My point was that you could build the facilities and assemble the rocket on Cape Canaveral without too much danger (I doubt that such things are all that safe, but presumably the workers would simply find similar work with similar dangers). Building the facilities and assembling the rocket in an extreme environment such as Antarctica would presumably add more danger than simply "driving a car". Having your dexterity limited by parka, getting concrete to set in extreme cold, and the difficulty of inspecting welds (can only be done when you can safely remove face cover and googles, presumably "winter"*)? I really don't know what the dangers are for polar launch. It seems that not enough people take an Orion launch seriously to bother looking into it. *winter for the northern hemisphere

Eh? I guess ~2000 deliverable warheads (down from 30,000+) means its no longer "bounce the rubble" time. But assuming more than a few hundred survive in any one place, the whole will bounce back in a few centuries (citation: what if?). The big problem is that the technology will *never* return, largely due to resources requiring 21st century (roughly) heroics to get to. But the whole "death and destruction bit" wasn't that the Earth would be destroyed, but that the Earth would suffer the *all* the fallout from every explosion used to lift the Orion until at least lunar interception (and probably then some, assuming the fallout is heading toward Earth). The original Orion calculations assumed that most of the fallout would miss Earth and that it would be fairly safe, and those conditions are only true for an anartic (or arctic) launch.

I only just started a normal career as a forum thread test (landed on Minmus, probes to Duna) and things were going great (I tend to obsess about low cost rockets and like to use SRBs). If I run out of money on my main career, which is in the doldrums due to overly ambitious planning, I will probably just bring up the cheat menu so I don't have to transfer all my ships to sandbox mode. Career mode just seems like "the main game" (mostly so keeping costs down makes some kind of sense, plus at least you can do science) to me, but I am no longer interested in grinding contracts.

Of course, there is the issue of why [US] commercial flights of sufficient distance don't refuel mid-air. Certainly US-Asia flights could be re-fueled over Hawaii for a considerable savings of weight over the course of the flight. Certainly nearly all US commercial pilots (especially the ones flying the big jets to and from Asia) have experience in mid-air refueling. Somehow I don't see the FAA allowing such things for passenger (and presumably Fed-Ex as well, do they do any refueling?). I really have to question the direction this thread has gone. If a turbojet's efficiency isn't enough to propel a rocket, you have bigger problems than the Isp of the turbojet. If mach 5 isn't fast enough (the rocket has to carry too much fuel for mach 5-"mach" 25), then you are very unlikely to fix the problem by increasing the Isp of the turbojet's performance <mach 5. I still wonder if burning liquid oxygen in combination with a scramjet would help at all. Before playing KSP, I thought it was a much better idea, but it might have promise. The idea is that while scramjets appear to work above mach 5 (and prototypes have proven so), they are lucky to provide as much thrust as they experience drag. Assuming (the big if, and why KSP dashed my dreams) is that this number *must* be positive or the whole scheme collapses. If it is positive, then adding additional thrust (from a liquid oxygen oxidized rocket) would increase efficiency, decrease the time it took to accelerate to maximum airspeed (presumably cutting the length of time it has to withstand brutal temperatures) and hopefully increase the fuel spent to accelerate (kind of like increasing TWR to decrease drag losses, only with drag losses* instead of gravity ones). If the number is negative, then you are better off setting your gravity turn to accelerate out of the atmosphere. Also note that the Isp of such a jet-rocket would be miserable compared to the SABRE (and maybe 50-100% better than a hydrogen rocket). The idea is to make it up by extending the speed you can use air at. * yes, I know going faster will increase drag losses. But going faster is the entire point of the exercise. The point is to get going as fast as possible while still breathing air.

Nope. Two problems with Orion: You can ignore the revised safety issues which were mainly "I become as Death, the destroyer of worlds" and spew death and destruction all over Earth. You can build the Orion on Antarctica (don't count on the arctic ice to support you over the summer) and avoid all the issues involved with that (and have roughly the same safety assumed with the original Orion calculations that ignored the [undiscovered] magnetosphere). You can't seriously claim that building an Orion on Antarctica is safer than driving a car (at least for the construction crew). On the whole, I'd admit that building an Orion on Antarctica is still safer for the ground crew than building a 1959 designed prototype, but it isn't safer than driving a car.

Car energy "waste" is pretty complicated. Basically, it takes about 30hp to maintain a fairly aerodynamic car at highway speeds (double or triple that for light trucks). Also note that most cars do more poorly driving around city streets accelerating and decelerating, so obviously that is typically done in an inefficient way. If you are driving something like a prius that has a ~60hp (gas) engine, your engine will be relatively efficient producing 30hp. For everyone else, producing 30hp isn't something they are all that good at. Oddly enough, larger engines are (technically) more efficient at producing power, the problem is that they tend to produce power efficiently at 100hp or more (which is great if you are going 100mph+, otherwise it will simply accelerate you until you are going 100mph+). A graph of Brake-specific-horsepower is shown below. The red part is the area where the engine is most efficient, and the dots indicate random samples of the car's driving. From poor memory, I think the car was an early saturn, which had around ~120hp. Expect modern engines to have islands twice as high as seen in the graph (but the dots only slightly higher, although modern cars are *much* heavier than plastic saturns). My understanding of fossil fuel plants (at least the more recently built ones) is that they are pretty close to Carnot efficiency (meaning that there is *no* *way* to increase efficiency beyond that while burning the fuel). This means they should be about as good as possible for turning motors in machinery, but that you should avoid using them for direct heating (heat pump efficiency depends largely on the heat source they are pumping).

Where are the flying pancakes? Why didn't you figure out that .23 had no aero model to speak of, and flying pancakes were the way to go? I knew when I joined that I would miss the mad science of KSP once the fixed the aero, but I only want to go back to visit, and play most of my KSP here (or 1.1, although I'm not terribly interested even with a AMD thread-needy processor).

The milestone system has basically saved career mode for me. I've gotten to the point where contracts exist to pay extra for things that are already planned (with the occasional side job that sounded worth doing or otherwise picking up free money (test on pad)). My best guess is that this was what career mode was meant to be (with the sliders letting people who just have to grind have their grinds), but was too hard to calibrate across all players with just contracts.

I started up a new career mode to check a few things for a thread and kept coming back to it. I think something like my 6th mission went to Minmus (without an orbital depot), hit 6 biomes (some of it was luck, hitting slopes and midlands, and I definitely needed to save and reload a bunch of times) and brought back 3000 science. It was a bit much. The flip side of this is that *landed* science labs appear to be a bit of a problem. After sending 2 probes and 2 kerballed missions, I've finally located a place on Minmus with constant Kerbollight. This whole project is just too ambitious (and requires too much un-kerbal planning) and keeps me away from the game (training up all the scientists was *not* fun). Once I get enough science returned to Kerbin* (and capsules *way* too full of science) I will finally be able to land my science labs (plural highly not recommended, which has plagued me the whole project). * I need to unlock mechjeb to land on the right spot. Roving to full Kerbollight has not proven successful. However much I avoid mechjeb, I will need it for this mission.

+1 to doing Minmus first. You can drain Minmus dry in a single launch if you use a small, light science lander and a big fuel tank which you leave in orbit. The key to the lander is to keep it low, light, and squat. My typical early-career lander is a Mk1 lander can, with a pair of the 1-ton LFO tanks mounted on the left and right sides of the can. Engine is either a single Terrier under the can (with fuel lines) or, if I have them unlocked, a pair of Sparks (one under each tank). Science Jr goes on top of the can, with probe core and junior docking port on top of that. Micro landing legs, mounted on the front/back of the tanks. A pair of goo canisters slung front/back on the bottom edge of the can, and the little science instruments beside the hatch. The whole shebang comes in at around three tons including fuel. It can handle one round trip from Mun orbit to the surface, with a single very short surface hop thrown in. On Minmus, it can do a round trip from orbit plus multiple biome hops. It's so low and squat that it's virtually tumbleproof; it can land on any slope that it doesn't actually slide downhill. It's also extremely nimble to rotate, especially on the pitch axis, due to the mass distribution. Note that according to the ksp wiki, if you can do surface samples you can transfer fuel (that doesn't match with my play, but I could be wrong). You do need clamp-o-tron [jr]s if you want an orbital fuel depot, and that will cost you 90 science (but let you easily hit all the biomes on Minmus. Hitting multiple biomes on Mun likely is an exercise in planning and mapping (plus having an orbital depot)). I'd still prefer to go to either without docking, but that is mostly habit. Assuming you don't care too much about calendar time, I'd recommend probes to Duna/Eve (before any kerballed flight beyond orbit). They don't require much more than to Mun, and bring back a ton of science.

One thing they would get from this attempt (without damaging the barge) is the effects of using 3 engines. I'm guessing this would have something like a TWR >6 (one engine at 60% throttle is still greater than 1). This might be useful as a pre-landing-burn before starting the "proper" suicide burn (or simply have the burn end such that the center engine could adjust the throttle as needed depending on how much delta-v the other engines provided). No idea how much fuel reserves you would need to make sure both engines would last through such a "preburn", but you would at least avoid a certain amount of gravity losses. Initially, I thought that a 6g+ burn might put a significant strain on the rocket (and it probably does), but the whole thing can handle rocket+fuel at >1g, so 10% of that mass at 6g+ isn't going to be nearly as hard (on the main structure. Some parts are going to feel all of it. That's certainly one of the reasons why they needed to at least try a recovery).