Northstar1989

So, FreeThinker, are you going to try your hand at implementing this equation for the Thermal and Electric engines in KSP-I? Thrust = (Vacuum ISP) * (9.80665) * (Mass Flow Rate) - (Exit Area) * (Background Pressure) It's not really half as big and scary as it looks. I can even provide you with the Exit Area values for the existing engines if you really don't think you're able to do that on your own. The rest is just a matter of making the code reference variables that *CANNOT* be fixed-value because by their very nature they change based on the rocket's situation... If you can't figure out what the values mean or how the equation works after 20-30 minutes of study, what you *REALLY* need is to go back and educate yourself and make sure you have a solid grasp of the fundamentals of rocket-science... ALL of the terms are fairly intuitive to somebody who understands it... Regards, Northstar

FreeThinker you had some questions about the equation I posted above that you sent me by PM, and I answered them there- but I also want to answer here so others can jump in if they think they can explain things any better to you... You said: Yes you told me, but how to interper the the data, let's say I found it diameter is quivalent to a 0.3 diameter procedual part, now how shouls I use the 0.3m into the parameter? is it 0.3 or 3 or 30 or 300 or something else ... The units are already there in the equation. There's nothing you need to actually to do but make KSP find the right units. You don't need to add in any coefficients or multiples or anything like that (in fact, doing so would lead to an incorrect result...) Once again, it's: Thrust = (Vacuum ISP) * (9.80665) * (Mass Flow Rate) - (Exit Area) * (Background Pressure) Thrust is in kN. So once you plug everything in, it will spit out the output for what thrust level the engine should be producing under a given set of conditions. Vacuum ISP is in seconds. It's a known quantity for any engine- you can find it just by right-clicking already. It's a little harder with the Thermal Rockets than with the electric thrusters, because the Thermal Rockets have variable ISP based on reactor core temperature- and even some reactors (the Pebble Bed Akula-style reactors) vary in temperature based on how long they've been running and such... 9.80665 m/s^2 is a number. There's nothing that ever varies about it, or that you ever need to change. It's the only unvarying coefficient in the whole equation. Mass Flow Rate is in metric Tons/second. It must be calculated for an engine in real time based on its throttle level, etc. You need to find a way to write a code that can continuously monitor this and respond to it. The mod RealFuels already includes code that does *precisely* that to dynamically alter thrust in *EXACTLY* the same way we need to- in fact the only reason we don't just re-use that code is because it doesn't plug Mass Flow Rate into quite the right equation (the value for Vacuum ISP is missing, for instance.) Exit Area is in square meters (m^2) and needs to be configured for each engine. Basically, you need one for each of the diameters of Thermal Rocket Nozzle (once you figure out the Exit Area of one Thermal Rocket Nozzle size, you can just multiply it by the square of the relative diameter of the others- i.e. the 2.5 meter nozzle has 4 times the Exit Area of the 1.25 meter nozzle). In case I wasn't clear about this before, Exit Area is simply the surface area of the opening the the exhaust stream moves through and that it pushes on as part of the nozzle, or the size of the exhaust opening on an electric thruster, and is a physical property that can easily be geometrically computed for ANY nozzle and engine. So, let's say the 3.75 meter diameter Thermal Rocket Nozzle has a 3 meter diameter opening, and then a short nozzle that extends out 0.5 meters horizontally and vertically at a 45-degree angle. The Exit Area is just pi-r^2 = 9-pi (9 * 3.14159) for the opening, plus the surface area of the partial cone- which comes out to the surface area of a trapezoid with a top side of 6-pi meters (the circumference of the exhaust opening) and a bottom side of 7-pi meters (the circumference of the bottom of the nozzle), and a height of 0.707 meters (so 6.5-pi * 0.5). Things become a little trickier if the nozzle is curved rather than straight, but in that case we can probably just approximate the curve and look up the relevant equations for the surface area of the shape... Background Pressure, finally, is in kPa (kN/ m^2) and is just the atmospheric pressure at the altitude of the rocket engine. KSP assumes a simple atmospheric model where pressure just falls off exponentially with the Scale Height (i.e. it doesn't account for temperature-changes with altitude or suppose a Thermosphere...) If you don't know how to calculate atmospheric pressure under such a simplified model, it's just calculated from: Atmospheric Pressure at sea-level * e^ (-Altitude / Scale Height) Where "e" is the exponential growth/decay function... For Kerbin, atmospheric pressure at sea-level is the same as on Earth: 101.325 kPa. So, for a height of 10 km on Kerbin (where the Scale Height is 5 km) it's: (101.325 kPa) * e ^ (-10/5) = (101.325) * e^(-2) = 13.71285 kPa KSP already internally records atmospheric pressure somewhere, and utilizes it to apply the stock Atmosphere Curve to adjust ISP for ambient pressure (although not *NEARLY* as accurately as the formula I posted above- for instance fuel flow rather than Thrust changes with ISP in the stock Atmosphere Curve equation...) and to delete vessels on rails once they reach a certain atmospheric pressure, so it may even be possible to harvest this variable from wherever KSP has it recorded rather than make KSP re-calculate it for your own needs... All of this is math, and I'm re-posting it here so that more people can help explain it to you. We already know all the variables for any given engine- it shouldn't be that hard to calculate the thrust for any set of conditions... The hard part is the coding, *NOT* the math... Regards, Northstar

@NathanKell If you configure the Exit Area for an engine right, it should perfectly reproduce the sea-level ISP of any real engine. It's just a matter of determining the right Exit Area (which the simplest solution is to geometrically compute, but for a 100% accurate solution you have to make some corrections for things like boundary-layer separation, so you can always tweak it for a given engine until the performance at full-throttle matches the real thing...) The the equation I posted above is the one that describes real engine performance at different ambient pressures and throttle settings in real life, so as a rule it *HAS TO* reproduce the real performance, unless there are major deviations like, as I said, boundary-layer separation, or drastic over-expansion of the exhaust stream... Regards, Northstar

@NathanKell The point was to not only suggest use of a formula that corrected for throttling in-atmosphere, but also was set up to easily be a adapted to any mods that introduced deployable extended nozzles in the future... You're right about the F-1 (I think). I was getting a little confused from reading up no the Sea Dragon, which was proposed in the late 1960's (deployable extensible nozzles are *NOT* as new as you think) and unlike the Saturn V *DID* feature a deployable extensible nozzle on both the launch and upper stages... (the upper stage had a nozzle that would deploy to larger than the diameter of the launch stage, in fact!) Apparently, they decided a pressure-fed stage with a deployable nozzle was simpler and therefore cheaper (which was the whole point of the Sea Dragon, as a Big Dumb Booster) than a turbopump-fed rocket stage with comparable performance... Anyways, the F-1 engine wasn't really the focus of the discussion at hand... The formula I suggested *WAS*... The formula I suggested corrects for throttling. It corrects for deployable nozzles. *AND* if you come up with a good way to code it into KSP, we can re-use it for KSP-Interstellar for the electric and thermal rocket engines there (which utilize different engine modules than normal/stock rocket engines), which *BADLY* need a realism-pass to reflect the differences in sea-level performance of the different engines based on their Specific Impulse and Mass Flow Rates (it's possible in KSP-Interstellar to power a GW-scale plasma thruster with Microwave Beamed Power in-atmosphere, for instance- and at Mass Flow Rates that high, even an electric thruster gets good performance at sea-level due to the incredibly high Exhaust Pressure that results... Also, a Microwave Thermal Rocket utilizing Nitrogen or Carbon Dioxide should suffer from a *LOT* less atmospheric-compression that one utilizing Liquid Hydrogen, due to the much higher Mass Flow Rate involved- whereas right now *ALL* Thermal Rockets in KSP-Interstellar lose 40% of their ISP at sea-level regardless of propellant-choice, Mass Flow Rate, or Vacuum Specific Impulse...) Regards, Northstar

NathanKell, Starwasher, etc. Hi guys! I was doing some research on atmospheric-compression of rocket exhaust-streams for inclusion of a thrust-loss effect on electric thrusters at sea-level in KSP-Interstellar, and it turns out the formula you guys use in RealFuels to simulate the relationship between Specific Impulse and rocket Thrust across different Background Pressures (ambient atmospheric pressures) could use some work as well! The formula that describes the relationship between rocket thrust an ambient atmospheric pressure is: Thrust = (Vacuum ISP in seconds) * (9.80665 m/s^2) * (Mass Flow Rate) - (Exit Area in m^2) * (Background Pressure) Vacuum ISP, Mass Flow Rate [equals: (Fuel Flow in Liters) * (Mass per Liter of Fuel)], and Background Pressure are all easily-accessible in KSP. The Exit Area is a result of the thruster-geometry for any given engine, and is simply the size of the exhaust opening for engines without nozzles like electric thrusters... (whereas chemical rockets normally have nozzles to increase the Exhaust Velocity, which has the side-effect of increasing the Exit Area...) The Exit Area is unique to a given engine/nozzle combination, and generally remains constant throughout the flight (*unless*, like the Saturn V's F-1 Engine, you have a Nozzle Extension that deploys at higher altitudes to increase vacuum ISP; or you have some other variety of Extendable Nozzle). Notice this formula leads to the following effects: - Engines with high Vacuum ISP, but low Thrust, suffer comparatively-large losses of thrust at sea-level due to their very poor Mass Flow Rate. This matches the behavior of electric thrusters at low power-levels in the real world well... - Engines with high Mass Flow, and comparatively small Exit Area (such as a launch-stage chemical rocket engine) suffer a comparatively small loss of thrust at sea-level. This matches the behavior of first-stage chemical engines in the real world well... - Engines with medium Mass Flow, and comparatively large Exit Area (such as an upper-stage chemical rocket engine) suffer intermediate loss of thrust at sea-level as a fraction of their vacuum thrust. This matches the behavior of upper-stage engines in the real world well... - Cutting the Mass Flow Rate, without reducing the Exit Area, results in a proportionally-larger loss of Thrust (and thus a lower sea-level ISP). This matches the behavior observed when throttling-down a rocket engine in-atmosphere in the real world well... The biggest difference between the current formula in RealFuels and the one that applies in real life is that your atmospheric ISP declines when you throttle down a real rocket engine due to a reduction in the Exhaust Pressure (which is proportional to Mass Flow Rate, and factored out of the above equation entirely), whereas (as far as I know) it doesn't in RealFuels... Regards, Northstar

@FreeThinker GREAT NEWS! Turns out it was possible to get around all the messy calculation of Exhaust Pressure, and use an already-existing formula to calculate thrust-loss at non-zero Ambient ("Background") Pressure! The simplified formula is: Thrust = (Vacuum ISP) * (9.80665) * (Mass Flow Rate) - (Exit Area) * (Background Pressure) Vacuum ISP, Mass Flow Rate [equals: (Fuel Flow in Liters) * (Mass per Liter of Fuel)], and Background Pressure are all easily-accessible in KSP. The Exit Area is a result of the thruster-geometry for any given engine, and is simply the size of the exhaust opening for electric thrusters... (which don't normally have rocket nozzles to increase Exit Area) The easiest way to calculate the Exit Area for the KSP-I electric thrusters would be simply to hold up a Procedural Parts fuel tank of a known radius, and try to approximate the radius of the exhaust-opening for the electric thrusters currently in-game... Notice this formula leads to the following effects: - Engines with high Vacuum ISP, but low Thrust, suffer comparatively-large losses of thrust at sea-level due to their very poor Mass Flow Rate. This matches the behavior of electric thrusters at low power-levels in the real world well... - Engines with high Mass Flow, and comparatively small Exit Area (such as a launch-stage chemical rocket engine) suffer a comparatively small loss of thrust at sea-level. This matches the behavior of first-stage chemical engines in the real world well... - Engines with medium Mass Flow, and comparatively large Exit Area (such as an upper-stage chemical rocket engine) suffer intermediate loss of thrust at sea-level as a fraction of their vacuum thrust. This matches the behavior of upper-stage engines in the real world well... - Cutting the Mass Flow Rate, without reducing the Exit Area, results in a proportionally-larger loss of Thrust (and thus a lower sea-level ISP). This matches the behavior observed when throttling-down a rocket engine in-atmosphere in the real world well... - Engines with HIGH Mass Flow Rates *AND* Specific Impulse suffer *VERY* little thrust-loss in-atmosphere, even at higher Background Pressures. This matches the predicted behavior of a high-powered electric thruster in-atmosphere well... Some other thoughts: - A Microwave Thermal Rocket, in real life (and in KSP) is normally capable of maximum Mass Flow Rates that match or exceed a comparable-sized chemical rocket engine, while having more than twice the Specific Impulse. Thus, with enough Microwave Beamed Power, a Microwave Thermal Rocket should make a *SUPERIOR* launch-vehicle to a comparable-sized chemical rocket, as it is less vulnerable to atmospheric-compression of its exhaust stream (as the Exhaust Pressure is actually higher at comparable Mass Flow Rates due to the higher Specific Impulse...) - All this reading up on the relationship between Exhaust Pressure, Background ("Ambient") Pressure, net Thrust, and Exhaust Velocity also led me to another interesting relationship... Real life rocket nozzles exist in order to expand the flow of gasses leaving the combustion chamber of the rocket, and thus increase Exhaust Velocity at the expense of Exhaust Pressure and Exhaust Temperature... The Microwave Thermal Rockets in KSP-Interstellar all have Specific Impulse values that assume a linear flow of exhaust without expansion or compression. However, if you slapped a typical rocket-nozzle like one used on chemical rockets (one that expanded the flow of exhaust gasses from the exit of the heat-exchanger) on the bottom of a Microwave Thermal Rocket, you could increase the Exhaust Velocity (and Specific Impulse) at the expense of Exhaust Pressure (and Thrust). Thus, by simple mechanical manipulation of the exhaust stream, you can optimize a Microwave Thruster for Thrust and sea-level performance, or Specific Impulse and vacuum performance. The only difference is the nozzle shape/size and mass, yet you can get drastically different performance values by simply changing the nozzle... Since a Microwave Thermal Thruster is capable of Mass Flow Rates comparable to a similarly-sized chemical rocket engine with more than twice the Specific Impulse when using H2, and at a *significantly* lower Exhaust Temperature (the high ISP is due to the very low Molecular Mass of H2, *NOT* high Exhaust Temperatures...), there is a LOT of room for manipulation of the exhaust-stream to improve Specific Impulse. An expanding nozzle could be used to improve the Specific Impulse further at the expense of Thrust- for instance once could theoretically increase the Specific Impulse 41.42% and cut the Thrust in half to achieve an identical Thrust (before the effects of reduced Exhaust Temperature- which would cause Thrust to drop even further...) to a chemical rocket engine of comparable size for a lower engine mass and a whopping Specific Impulse of over 1200 seconds! (assuming a starting ISP of 850 s for Hydrogen and a starting Thrust twice that of a similar-sized chemical rocket: both of which can be achieved with current technology...) Such drastic increases in Exhaust Velocity are not possible with a Hydrolox chemical rocket because the Exhaust Temperature would drop below the boiling point of Water (the primary exhaust constituent) with such a drastic expansion of the exhaust stream... (this would also dramatically increase the vulnerability to atmospheric-compression at low altitude) But the boiling-point of hydrogen is *MUCH* lower, and thus a pure-H2 thermal rocket can safely expand its exhaust stream to a *MUCH* greater degree than a LH2/LOX chemical rocket... Bottom Line: I have provided a formula above that relates Mass Flow, Specific Impulse, and the effects of Ambient Pressure on rocket Thrust. There is also room for the inclusion of exhaust nozzles specifically geared towards vacuum or sea-level performance with the Thermal Rocket Nozzles... (It might be worth creating alternate versions of the Thermal Rocket Nozzle part that has a nozzle size-shape is optimized for vacuum operation, as the current exhaust nozzle is optimized for sea-level performance.) The Atmosphere Curve of the current Thermal Rocket Nozzle also needs to be *COMPLETELY* thrown out: it does NOT accurately reflect that whereas a fission nuclear-thermal rocket might be operating at very low Mass Flow Rates and thus operate poorly inside the atmosphere, a Microwave Thermal Rocket using the same Thermal Rocket Nozzle part may have as much as TWICE the Exhaust Pressure of a comparably-sized chemical rocket due to the very high Mass Flow Rate, and thus actually have *REDUCED* vulnerability to atmospheric compression vs. a chemical rocket... (the current Atmosphere Curve for KSP-I Thermal Rocket Nozzles means that they *ALL* have VERY HIGH vulnerability to atmospheric-compression, with seal-level ISP only 40% that of vacuum ISP, despite the fact that *AT SUFFICIENTLY HIGH MASS-FLOW RATES* a Thermal Rocket can *EXCEED* the sea-level ISP of a chemical rocket by a very large margin, and easily achieve more than 80% the sea-level ISP compared to vacuum ISP... Regards, Northstar

Hi Tnelluz, Your fusion reactor actually appears to be working correctly- it is currently in "Standby Mode" in the screenshot you posted, and thus only producing 20% of maximum thermal power. This is actually a GOOD thing, as it reduces your reactor fuel-consumption when it is not actively in use. In order to get the reactor to produce its full rated thermal power, you need to include some kind of draw on the reactor- such as running a Thermal Rocket Nozzle or a Plasma Thruster... Then the reactor will automatically dial itself up to meet the new power demand, with a maximum possible thermal power production of the rated capacity of the reactor. Keep in mind that if trying to produce electricity, you will NOT produce the reactor's rating for heat-production in electricity: generators in KSP-Interstellar (like in real life) actually lose the MAJORITY of the thermal power passed through them, and only manage to convert about 20-40% into electricity... Also, FreeThinker, I hope I didn't overwhelm you with all the math before. The basic, key formula you needed to know was: Thrust = (Mass Flow-Rate) * (Exhaust Velocity) + [(Exhaust Pressure) - (Background Pressure)] * (Exit Area) A plasma thruster has a small Exit Area (which reduces the loss of thrust when ambient pressure > exhaust pressure), but has an even lower Exhaust Pressure at low mass flow rates (which means it loses a lot of thrust when operating in-atmosphere at low power-levels). When dialed up to higher mass flow rates (which KSP indirectly records for all engines through "Fuel Flow"- multiply this by fuel resource-density and you have the Mass Flow Rate...) the Exhaust Pressure increases (the simplest way to reflect this relationship would be linearly for now...) and the effect of atmospheric pressure decreases... Once again, you can get plasma thrusters with *VERY* similar vacuum and sea-level performance with sufficiently high Mass Flow Rates... KSP already has *ALL* the relevant numbers recorded for an engine or easily derived from existing numbers (Exhaust Velocity in m/s is just Vacuum ISP * 9.80665, Background Pressure is already internally monitored and used to apply the stock Atmosphere Curve) *EXCEPT* for Exhaust Pressure. Figure out the Exhaust Pressure for any given engine, and you can figure out the thrust-loss for any given ambient ("Background") pressure... I'll post a simplified formula to approximate Exhaust Pressure for a given Thrust/ISP soon. Regards, Northstar P.S. One interesting effect of a realistic relationship between Exhaust Pressure, Background Pressure, and net Thrust is that you see a reduction in ISP when you throttle down an engine in-atmosphere... This actually occurs in real-life, and is something that is not currently simulated in ANY mod (including RealFuels), so you'll be breaking ground!

FreeThinker you might find THIS equation helpful for creating a thrust-ISP relationship: Thrust = (Mass Flow-Rate) * (Exhaust Velocity) + [(Exhaust Pressure) - (Background Pressure)] * (Exit Area) Where "Background Pressure" is the ambient pressure around the spacecraft, and Exit Area is the nozzle-size (it's worth noting that in a chemical rocket, increasing the nozzle-size increases Exhaust Velocity, but decreases Exhaust Pressure, due to the flow dynamics of the exhaust-stream...) Electric Thrusters normally operate in the regime where Background Pressure is negligible- outside the atmosphere. However, if fired INSIDE the atmosphere, the Background Pressure will typically overwhelm their anemic Exhaust Pressure (which is so low that electric thrusters usually don't even include a proper nozzle to provide extra Exit Area, as it's not worth the extra mass...) and the second term becomes negative, causing the electric thruster to lose thrust. The result is the effective Specific Impulse declines- the Mass Flow Rate does *NOT*, I repeat *NOT* change at all... And, with an electric thruster operating at very high power-levels (hundreds of Megawatts to Gigawatts), Exhaust Pressure no longer becomes insignificant, as Exhaust Pressure Increases with mass-flow rate (the exact equations that describe how are complex, but I'll leave it to Wikipedia, which says it best: "for a rocket nozzle pe is proportional to Mass Flow Rate"- note that I have substituted the word "Mass Flow Rate" for an "M-dot" symbol which is defined to mean "Mass Flow Rate"...) Exhaust Pressure also increases with the Exhaust Velocity, so a high-powered electric thruster with high Exhaust velocity should actually perform BETTER at sea-level (with less atmospheric compression) than a chemical rocket with the same mass-flow rate (once again, the issue in real life is that most electric thrusters have very low mass-flow rates due to the limited availability of electrical power...) I *highly* recommend the introduction-section of this Princeton PhD thesis for learning more about electric thrusters, which does a *VERY* good job of explaining the subject without over-complicating it... (the again, that's to be expected right? Princeton *is* the best school in the United States...) http://alfven.princeton.edu/papers/JZThesis.pdf If all this hasn't made it clear, the bottom line is this. There is NO DIFFERENCE between how atmospheric-compression affects a chemical rocket and an electric thruster. The *ONLY* reason electric thrusters perform poorly at sea-level with current technology is because they have INCREDIBLY low mass-flow rates, and thus very low Exhaust Pressure. Upscale the mass-flow rate enough (while keeping the high Exhaust Velocity), and you get an electric thruster that performs just as well or better than a chemical rocket at sea-level vs. in vacuum.., (you also end up with an electric rocket with a high enough Exhaust Pressure that it may be worth giving it a proper exhaust nozzle to increase the Exhaust Velocity even further at the expense of Exhaust Pressure, which allows for even higher Vacuum ISP levels at the expense of sea-level ISP...) This has never been done in real life, but it is *EASILY* possible in KSP-Interstellar with Microwave Beamed Power (on the scale of hundreds of MW to a single plasma thruster) or an Antimatter Reactor for the power-source for a high-powered plasma thruster... Regards, Northstar

The cost and density are quite reasonable for GASEOUS CO2. But as I pointed out, liquifying CO2 is absolutely trivial compared to liquifying something like N2 or even O2... Currently, the resource density is less than 1/40th the density of the Liquid Nitrogen resource, when it should be HIGHER. The trade-off when using CO2 vs. N2, besides resource-availability, is that CO2 is much denser (so you can fit more mass of it in the same size/mass tank) and incredibly easy to store as a cryogenic liquid, but N2 has a significantly higher ISP... An appropriate resource density of liquid (cryogenic) CO2 would be: Density = 1.200 kg/liter, i.e. 0.001200 mT/L (KSP uses metric tons/liter for resource-density, right?) Cost = 0.000020424 (I suggest rounding down to 0.00002 for simplicity) The density comes from a minor extrapolation of THIS table, by the way, which lists density down to about -50 degrees Celsius (CO2 won't form a liquid until -57 degrees Celsius at 1 atmosphere of pressure- however on Earth it is commonly liquified at higher temperatures by simply pressurizing it... This would be a poor idea in space, however, as pressurizing a cryogenic liquid and storing it at higher temperatures will *REDUCE* its density while requiring a *MUCH* higher tank mass, as pressure vessel tank mass is directly proportional to the pressure difference between the exterior and interior...) I suggest using 1200 kg/m^2 (i.e. 1.2 kg/liter or 0.001200 mT/L) as the density because it is a nice clean number and approximately equal to the density at -60 degrees (the density of a cryogenic liquid can be *increased* by lowering the temperature further below the boiling point, the density can be *decreased* by raising the temperature and increasing pressure to keep it from boiling, so we have a *little* flexibility as to the density we use...) CO2 is stable as a liquid down to about -78 degrees, where it starts freezing into a solid (dry ice) which is EVEN DENSER... (dry ice has a density of 1.4-1.6 kg/L, as compared to 1.2 kg/L for liquid CO2...) As for the cost, a metric ton of liquid CO2 currently costs an average of about $128 for bulk purchasers such as Liquid-CO2 retailers (who then package the CO2 into cylinders and then re-sell it for significantly higher cost). Converting the cost to 1965 dollars using THIS inflation calculator, as the convention of cost in KSP is that 1 Fund = $1000 1965 dollars, we come up with a resource cost of $17.02 per metric ton, or 0.00001702 Funds/kg. Converting this back to Funds/liter, we get a cost of 0.000020424 Funds/liter (for reference, Liquid Nitrogen is currently set to 0.00006 Funds/liter, and Liquid CO2 is *significantly* cheaper to manufacture and store than Liquid Nitrogen in real life...) Currently, the density of CO2 is based on its gas phase, and the resource has *no cost* set in KSP (it is free). I suggest adding in a Liquid CO2 resource or replacing the existing definition with the liquid CO2 stats... (the only reason Nitrogen needed a separate gas and liquid resource was because RealFuels already utilized the compressed gas for RCS- which is *NOT* an issue with CO2...) Honestly, I have no idea why Fractal_UK didn't just utilize the density of cryogenic CO2 for his Community Resource Pack to begin with... Honestly, I would suggest just re-using the textures for the Liquid Methane tanks. They seem quite stylish, and any tank capable of holding Liquid Methane should certainly be able to hold (much less cryogenic) liquid CO2. Note that I wouldn't recommend simply re-using the Methane tanks wholesale- their volume needs to be adjusted for realistic densities, based on their actual physical dimensions; and I would suggest smaller fixed tank sizes anyways (as CO2 is meant to be used as an electric propellant or an ISRU propellant for thermal rockets on/around Duna...) Currently the stock KSP-I Liquid Methane tank has significantly lower volume-capacity that its actual dimensions as the stock KSP-I Liquid Methane resource is *MUCH* denser than the real thing (this was probably done to make it competitive with LiquidFuel, and to give it a similar feel in terms of volume capacities, as players wouldn't know just how far off the density used really was, and would otherwise assume the Methane tank held much more mass than it did based on their experiences with LiquidFuel, if a more realistic volume/density were used...) However since we're using *REALISTIC* densities for CO2 (it's much simpler than trying to come up with an arbitrary value that feels "right" for the game- even Fractal_UK used a realistic value for the density of the gaseous phase CO2 in the CRP...) we need to correct the volume so the tank holds more. A good rule of thumb is that a fuel tank should have about 5x the resource capacity when moving to a realistic resource-density (unless you seriously think stockalike fuel tanks should have a utilization of less than 20%) Or, just used a Procedural Parts tank stretched to exactly the same dimensions as the fuel-tank to figure out the approximate correct volume... (the default utilization of 86% is fairly good for a stock-balanced tank) Whatever solution you want to implement long-term. I just wanted to caution you that the main reason besides running out of time to do it that Fractal_UK said he *didn't* include N2 or CO2 as usable propellants (despite apparently already having a resource definition included for CO2 in the Community Resource Pack- although he really should have used cryogenic liquid rather than gaseous densities and included a resource-cost...) was because he didn't want to overwhelm players or their RAM with too many different preset tank-types. The response to which was a deluge of suggestions by numerous players (including myself) that he just include a tweakable tank like in B9/Firespitter (although these responses reached him too late- as he had just begun a long period AWOL from KSP-Interstellar, little to my or anyone else' knowledge...) Any solution that reduced the total number of parts players need to deal with- whether it's a universal-tank of some sort (the idea that a given tank could hold any number of propellants is not new to KSP, but nobody's figured out how to code a tank that can hold any of several resources but *ONLY* one at a time just yet...), or a tweakble tank that uses the same airframe/model for any of a number of different internal fuel tank setups, will be good with me and probably good with Fractal_UK. Personally, I'm just going to delete the preset tank from my GameData folder anyways, as I have done with *ALL* my cylindrical preset tanks, and replace them with Procedural Parts tanks on my rockets... (not fueled conical adapters, though- as FAR seems to play nicer with these than Procedural Parts tanks in conical shapes...) Speaking of which, you *REALLY* need to create ModuleManager patches for RealFuels and Procedural Parts so that players can generate Liquid Nitrogen (and soon Liquid CO2 or a re-balanced CO2 using liquid densities) tanks in these mods. Right now, the only usable way to store Liquid Nitrogen is in the Liquid Nitrogen Cryostat tank parts you released... (for reference, the KSPI_RF config already includes code to do this with KSP-I Water using Kerosene as a reference resource as it has the most similar properties to water- you could do the same using Liquid Oxygen as a reference resource for Liquid Nitrogen and Liquid CO2 to make these tanks available for any tank-type that can store Liquid Oxygen...) RealFuels includes a general fix for *ALL* parts with engine modules (which may or may not apply to the KSP-I electric thrusters, as they utilize a different type of engine module than stock engines), such that the nominal thrust is the vacuum-thrust of that engine (I *think*, although it might have been set to the sea-level thrust...), and the variation of Specific Impulse between sea-level and vacuum creates a change in Thrust rather than a change in Fuel Flow. This is *EXACTLY* how rocket engines behave in real life: an engine operating in vacuum doesn't consume less fuel at full-throttle than one operating at sea-level, it just generates more thrust... If you want to *REALISTICALLY* simulate how an electric engine behaves at higher atmospheric pressures, you'll do the same thing. Electric Thrusters don't perform poorly at sea-level because they have lower fuel-flow, they perform poorly because they have terrible Specific Impulse (ISP) at sea-level. The actual reason for this is because electric thrusters typically have VERY low exhaust-pressures (they rely on accelerating a very small number of molecules to a very fast speed instead of a lot of molecules to a slower speed), and thus suffer a LOT of atmospheric-compression of their exhaust stream at sea-level... Which brings up an EXTREMELY interesting point- a sufficiently high-powered (probably multi-GW) electric thruster operating on a low molecular mass fuel such as Hydrogen should actually have a very GOOD sea-level Specific Impulse, as its exhaust stream would have a quite-high pressure compared to the atmosphere (and thus the thruster would operate nearly as well at sea-level as in vacuum). The increased fuel-flow of a high-powered electric thruster doesn't just improve its thrust in vacuum, it also increases the density of its exhaust stream (and thus makes it perform better at higher atmospheric pressures). Theoretically you could have an electric thruster with a sufficiently high power-level that its ISP-curve was almost completely flat from sea-level to vacuum: that is its exhaust trail was so high-pressure that it was virtually unaffected by the surrounding atmosphere in low-altitude flight... In short, the reason electric thrusters perform poorly at sea-level is because the operate at very low fuel-flow rates (and thus exhaust stream densities). If an electric thruster's fuel-flow rate even started to remotely approach that of a chemical rocket, the curve between its sea-level and vacuum ISP would actually be FLATTER than that of a chemical rocket (that is, it would be LESS affected by higher atmospheric pressure) because its much higher exhaust-velocity leads to a much higher exhaust-pressure for the same mass-flow rate... Regards, Northstar

You need to make sure the Mass Driver and payload are separate vessels. The Mass Accelerator won't work right if it tries to accelerate something that's part of the same vessel (it will do nothing or likely explode). Take a look at this album (which I was planning on posting anyways for more examples for the players) to see a successful launch. Note that in the 2nd screenshot, you can clearly see from where the camera is centered that the Mass Driver and rocket are two separate vehicles. I did this by placing a small separator-style decouple between the two (one of the ones that detaches at both ends) and then firing it off (you don't see it in the 2nd screenshot because it exploded upon falling off the rocket and onto the launchpad...) Although, I suppose you could also try and build a crawler with rover wheels (or tank treads from a mod) and roll your rocket over from the Runway to the Launchpad, a throw-away separator is probably the easiest way... Other things to note: - The power-level is reduced to 49% on this Mass Accelerator stack. By (lots and lots of) trial-and-error I determined this to be the maximum safe power-level for this particular rocket and Mass Driver stack. The maximum safe power-level for any rocket and Mass Driver combo will vary based on the size and mass of the rocket, the length of the Mass Driver stack, the level of structural reinforcement (struts, launch clamps, KAS ground-pylons, etc.), and the aerodynamic design of your rocket (see below). - It is important that your rocket is not only streamlined, but aerodynamically-stable. This means you need most of your mass up top, and most of your drag towards the bottom of your rocket (PRO TIP: landing legs and/or stabilizer fins at the base of your rocket help IMMENSELY for this). As drag is tied to mass in the stock aerodynamics model, making an aerodynamically-stable rocket is quite difficult in stock (no, there's nothing *I* can do about this: it's one of the shortcomings of the horrible current placeholder aero model... The same difficulty in maintaining aerodynamic stability can be observed with long/tall stock rockets with very high liftoff Thrust-Weight-Ratio...) however in FAR you can design aerodynamic-stability into your rocket simply by keeping the Center of Mass high (placing denser fuels such as hypergolics in the upper stages makes this MUCH easier if you are playing with RealFuels) and the Center of Drag low (even adding lander-legs so you can recover the launch stage will add drag to the bottom of the rocket in FAR, which is *precisely* where you want it...) If your rocket is NOT aerodynamically-stable, it will tend to flip over after exiting the Mass Driver, and will make some pretty fireworks when it crashes into the ground (or tears apart due to aerodynamic forces in FAR), but won't get you into space... - Make sure your Mass Driver has enough electricity to operate- the acceleration isn't free! (Mass Drivers respect conservation of energy and all that...) Attaching lots of batteries to the Launch Clamps (or ground-pylons, etc.) holding the Mass Driver in place helps with this, as does simply attaching more Launch Clamps (each launch clamp produces electricity at a set rate) or solar panels, etc... - Make sure your Mass Driver is well-supported. They *DO* experience recoil, although currently the recoil appears to be in the wrong direction (in the same direction the payload is firing- which is why some players have noticed the Mass Driver rings, batteries and all following their rocket into the air...) I am hoping to fix the recoil-direction bug in the future, but either way you will have to deal with recoil in one direction or another- so make sure you have plenty of launch clamps, pylons, or struts! As always, I hope you guys enjoy playing with the Mass Driver mod, and let me know if you have any problems with it! Regards, Northstar P.S. As always, my example screenshots are from a Career Mode install with Real Solar System 64K (which adds difficulty by up-scaling the planets and thus increasing Delta-V requirements to orbit, and is one of the reasons Mass Drivers are particularly pragmatic for my space program in the first place...), MechJeb2 (for the informational displays), FAR, Deadly-Re-Entry, Realfuels, Procedural Parts (which helps *immensely* with producing a nice streamlined shape for my rocket that is stable at high speeds), Procedural Fairings (also helps with streamlining), and NovaPunch2 (adds some useful engines- such as the one I used in the SSTO featured above...)

The maximum survivable splashdown speed of the Sea Dragon was 300 ft/s- which equates to about 329 km/h, not 360. However, I agree that it's a rather impressive number. The thing to remember about a rocket is that it's already built to survive substantial g-forces anyways: just normally rockets are very light and thus the total forces survived aren't that great in magnitude (for analogy: a needle can survive far more g's than a large wooden block, but the block can survive greater *magnitudes* of force...) However the Sea Dragon was *VERY* sturdily built, and unlike a boat, has very little mass besides the structural elements (which were quite heavy for a rocket) once the fuel is burnt-out. I have little doubt that a hollow metal tube the size of a battleship could survive a 328 km/h splashdown (that's a little over 91 m/s, for reference) if it didn't have *ANY* cargo or fuel mass weighing it down...) There *were* provisions for minor repairs to the structure after splashdowns (the Sea Dragon was designed for easy repair), however, and they did design a drag-skirt to reduce splashdown speed to something like 20 or 30 m/s- so they clearly weren't expecting to push the maximum structural tolerances on a regular basis... As for cargo-mass, the Sea Dragon would have been *quite* useful as a fuel-tanker or for launching large fuel-depots to LEO. The payload-capacity of the Sea Dragon was less than twice that of the Saturn V, despite being more than four times as massive on the launchpad: and the vast-majority of mass necessary for missions beyond LEO is fuel- so it's not like you couldn't have burned through that fuel mass in a fairly small number of missions (*especially* if you were using lower-ISP storable propellants like Kerosene, instead of cryogenics, and launching mission vehicles with only the necessary LOX onboard...) It also could have launched the ISS in just a handful of launches, for a *fraction* of the total cost of the Shuttle (or even using Saturn V rockets to launch the ISS). Regards, Northstar

FreeThinker It's great to see another release of the KSP-I Extension Config we've been working on (with you doing all the coding of course!), a few questions: (1) Where did you get the current cost and density for Carbon Dioxide? (I take it you used the figures I provided for what the ISP and efficiency should be, but I never provided any for resource density/cost...) Based on the absolutely trivial amount of cooling or insulation necessary to store it as a cryogenic liquid (its boiling point is -57 degrees Celsius, which is warmer than the boiling-point of Liquid Oxygen and Liquid Methane, and only *slightly* warmer than the ambient temperature of approx. -40 degrees Celsius in Low Earth Orbit...) its density and cost should almost certainly be based on its liquid form. (2) How are players currently supposed to store harvested CO2? It's *not* a pre-existing resource in RealFuels like Nitrogen is (and thus can't be stored in RealFuels or RealFuels/Procedural Parts tanks), and Procedural Parts requires a ModuleManager patch to allow existing Procedural Parts tank types to store it (look at how the RealFuels/KSP-Interstellar integration config adds Water storage to every tank type that can hold Kerosene- something similar should work using Oxidizer and Liquid Oxygen as the reference resource for the stock Procedural Parts, and both procedural and non-procedural versions of RealFuels tanks, respectively...) and there should almost certainly be a tank type native to KSP-Interstellar (like the Nitrogen Cryostat tank- except without any electricity consumption requirement, similar to the KSP-Interstellar Methane tanks...) for those players who use neither RealFuels nor Procedural Parts... There is, as always, the risk of tank-spam: which is why I suggested integrating all the new (and some of the existing, such as methane) KSP-Interstellar fuels into a single tweakable tank type similar to the tweakable tanks in Firespitter or B9 Aerospace... (3) The thrust-reduction of the electric engines at higher atmospheric pressures: is that done the realistic way (like RealFuels does with its ISP/TWR fix, where fuel flow remains fixed and ISP changes- thus affecting Thrust with atmospheric density) or by some other, unrealistic method? (where ISP remains fixed and fuel flow changes...) I can see potential problems with RealFuels-compatibility if it uses an unrealistic method, as you might end up compounding BOTH methods and create an overly-strong reduction in thrust with atmospheric density... Regards, Northstar

Low propellant-fractions is the WHOLE POINT of a Big-Dumb Booster. You save more in manufacturing-costs with the wider engineering margins than you incur in costs from needing a larger total rocket. The very fact that the mass-fractions were bad makes the rocker MORE feasible (they aren't trying to push the limits of technology, NOT less... The fact that you are criticizing this shows you haven't been readings my posts at all, just behaving rudely and offensively, and in a manner that should not be permissible on the KSP Forums. I suggest you take a little more care to be respectful of your fellow KSP-er's... Your numbers are wrong (the F-1 has a sea level ISP of 263 seconds, not 262 seconds; J-2 had an ISP for 421 seconds, not 418 seconds, so ISP would be 19 and 12 seconds lower- small differences like this mean a LOT in rocketry), and you are skewing the numbers to try and make your point seem more valid... The chamber pressure for the Sea Dragon's first-stage engine would be 300 psi, compared to 1015 psi for the F-1 engine. That is *NOT* an "order-of-magnitude" difference (generally defined as a 1:10 ratio or more), the pressure difference is only 1:3. Not only that, but 242 seconds is an entirely reasonable ISP for a chamber pressure of 300 psi, *especially* given that the Sea Dragon had an 8-year technology advantage over the F-1 (the F-1 was proposed and designed in 1955, whereas the Sea Dragon first-stage engine was proposed in 1963...) and relied on a much more expandable nozzle (expands from 7:1 to 27:1 as the engine climbs, compared to 10:1 to 16:1) which allowed for better performance at high-altitude. The formula for exhaust-velocity, by the way: Ve = SQRT[(2*k/(k-1))*(R'*Tc/M)*(1-(Pe/Pc)(k-1)/k)] Or, alternatively, a simplified version: [1 - (pe/pc)(k-1)/k] / (k-1) Notice the term "Pe/Pc"? This is the *ONLY* term in the entire equation where chamber-pressure comes into play- and even then not directly. What determines exhaust-velocity (and thus Specific Impulse) is not the chamber-pressure, it is the ratio between the chamber pressure and the exhaust pressure. This is determined by nozzle-ratio. The Sea Dragon design had an initial nozzle-ratio of 7:1, with an expandable nozzle that could expand up to 26:1 in the upper atmosphere. The Rocketdyne F-1 engine (the launch stage engine of the Saturn V) had a nozzle-ratio of 10:1, with an expandable nozzle that could expand up to 16:1 in the upper atmosphere. In neither case is the exhaust-stream ever over-expanded, but the Rocketdyne F-1 exhaust stream loses a lot of potential Isp in the upper atmosphere by having a lower nozzle-ratio. The Sea Dragon was TSTO (Two Stage To Orbit), so a higher maximum nozzle-ratio was designed in despite the extra weight as the launch stage would be flying higher into the atmosphere than the 3-stage Saturn V... The larger expandable nozzle; a "drag skirt" specifically designed to reduce the terminal velocity of the Sea Dragon's launch stage to under its maximum designed crash-tolerance of 300 ft/s during re-entry, such as to allow first-stage recovery with a purely drag-based landing in the ocean; and several design features that allowed the Sea Dragon to survive immersion and erection (being stood on end prior to sea-launch) in the ocean without ill-effects, all contributed to the "low" mass-fraction of 88%, as did the much wider engineering-margins and *MUCH* sturdier design (corrugated-steel, which as already stated, allowed the rocket to survive splashdowns at up to 300 ft/s without damage to any of the rocket's components) to allow for cheaper construction... All other terms in the equation besides nozzle-ratio cancel out when comparing the Sea Dragon and Saturn V except for Tc (chamber temperature), as they are based on the fuel used, which is the same (RP-1/LOX) in both cases. Thus, the only factors that differ which affect Isp are the nozzle area-ratio (which is 7:1 instead of 10:1 for the Sea Dragon main engine vs. the Rocketdyne F-1 engine...) and the chamber temperature. Regards, Northstar - - - Updated - - - With all due respect, you're wrong: Work on the 14D21 and 14D22 engines started in 1986, with a preliminary design completed in 1993. The RD-107A and RD-108A are improved versions of the original RD-107 engine (originally designed in 1954-1957) that were designed from 1986 to 1993. They: incorporate a new injector head design to increase specific impulse. Theses engines were first utilized in May 2001 to launch a Progress cargo spacecraft to the ISS, according to Wikipedia. Hardly sounds like a 1950's engine to me... Regards, Northstar

Impaler, your posts are consistently rude and offensive, and totally off-base... You also mis-represent my posts. For instance, I said: The Russian rockets are actually LOWER performance (as measured by mass and payload fractions) than American rockets. Note the words *as measured by mass and payload fractions*. ISP is entirely separate than mass/payload fractions. I am well-aware that Russian rocket engines have the best hydrocarbon-ISP in the world (thanks mainly to more advanced metallurgy, and higher chamber pressures). That is *NOT* the same thing as having good mass-fractions. In fact, one way to IMPROVE specific impulse, while HURTING mass-fraction is to make use of a higher-chamber pressure in your rocket engines. This in turn requires thicker engine walls, which requires an engine to have higher mass. You may get better stage Delta-V (up to a certain point) due to better ISP, but you actually hurt the stage mass-fraction... Hard Numbers: Saturn V payload-fraction: 4.6% Soyuz-FG payload-fraction: 2.3% The Soyuz-FG has a launchpad-mass of 305 metric tons (305,000 kg). Its payload capacity is 7.1 metric tons (7100 kg), meaning its payload-fraction is *just* above 2.3%. The Soyuz-FG made its first flight in 2001, whereas the Saturn V had its maiden flight in 1967. The Soyuz-FG has the advantage of 24+ years of technological progress on its side... Regards, Northstar

Just my 2-cents: I don't know why people keep demanding Heavy Lift vehicles for a Mars mission. We could do manned Mars missions with current launch-vehicles. It would just require multiple launches- i.e. you launch the crew compartment on one launch, and the transfer-stage for the crew compartment on another. You can also perform orbital refueling to break it up into even more launches- although that's never been done before for cryogenic propellants (it *HAS* been done with non-cryogenic fuels between a pair of specially-designed unmanned satellites, as a proof-of-concept, however...) WITHOUT orbital refueling, you can still break up a Mars-orbiter mission as follows: Launch #1: Mars Return-stage (transfer stage to return from Mars, docks with manned module in Mars orbit) Launch #2: Mars Return-stage Transfer Stage (carries return-stage to Mars orbit) Launch #3: Manned Module (carries crew from LEO to Mars orbit and back) Launch #4: Manned Module Transfer Stage (carries crew from LEO to Mars Orbit) A "Fylby" mission in the literal sense (free return from Mars to Earth) is actually MORE expensive than a Mars-orbiter mission (one that captures into Mars-orbit and then returns), as it requires you basically launch into a Cycler Trajectory (5 month outbound trip, 15 month return trip), which requires significantly more fuel and prevents you from breaking the mission into multiple smaller launches (to avoid the *ENORMOUS* cost of developing a new Heavy Lift Vehicle) unless you do the following: (1) Launch the Manned Module into Low Earth Orbit (2) Launch three transfer stages. Dock all 3 transfer stages with Manned Module (Transfer Stage #1 inline, #'s 2 and 3 side-mounted to Manned Module) (3) Use Transfer Stage #1 (attached inline) to carry Manned Module to a highly-elliptical orbit around Earth (likely over multiple periapsis-kicks), and detach now-depleted stage. (4) Use Transfer Stages #'s 2 and 3 to carry Manned Module to an Aldrin Cycler-orbit (basically, an orbit that will pass by Mars after 5 months and return to Earth after 20 total months) via a burn at the next Earth periapsis... The Aldrin-Cycler orbit requires significantly more (50-70% more) Delta-V in Earth orbit to place the Manned Module on the cycler-orbit in the first place compared to a typical Mars Transfer Orbit (one with an apoapsis that just barely reaches Mars, where the Manned Module captures into orbit...), but benefits from not needing to perform a return or capture-burn around Mars, thus reducing the total mission Delta-V requirement. There may be a third option, one that allows for a Mars Flyby and Earth-return WITHOUT utilizing an Aldrin Cycler or Venus-crossing orbit, but if there is, it would require a number of adjustment burns outside of Earth's sphere of influence- it would NOT be a simple free-return trajectory in the sense we make them around the Moon... Regards, Northstar

I'll just give a list with short notes, because in-depth explanations of the value of each would take several pages (you can ask me about specific responses if you'd like, though) Space Infrastructure that will help mankind conquer the "final frontier": 1. Orbital and surface-based Mass Drivers (optimized for cost-effectiveness, i.e. 1 km/s exit-velocity is much more worthwhile than 4 km/s; useful on Luna/LLO etc.) 2. Mountaintop Launch Sites (tiny reduction in Delta-V requirement, large increase in TWR/ISP due to reduced atmospheric pressure) 3. Microwave Power-Transmission Stations (better TWR/ISP, can be combined with Mass Drivers *and* built on mountaintops) 4. Reusable low-maintenance Spaceplanes (wide engineering margins reduce need for refurbishment/maintenance, can be Microwave-powered for better ISP/TWR...) 5. Cryogenic, actively-cooled Orbital Propellant Depots 6. Propulsive Fluid Accumulator satellites (Microwave-powered) 7. Orbital Tugs (Microwave-powered) 8. Microwave Power-Relay satellites (similar to comm satellites, but relay microwaves instead of radio wavelengths...) 9. Manned "recuperation" and limited orbital-manufacturing/assembly space stations (similar to what the Russians are planning) 10. Cycler Ships (paired- one for outbound and one for return journey to/from each celestial body) 11. Off-world ISRU stations (Sabatier Reactors on Mars, regolith and water-electrolysis on the Moon, etc.) 12. Fully-reusable landers and fuel-ferries (designed to carry fuel and crew to/from the surface of Luna, Mars, and other celestial bodies) All of these types of infrastructure can also be built on other planets/moons, and some of them are more useful there: Mass Drivers on bodies without an atmosphere (such as the Moon), for instance... Regards, Northstar

Wait, so the KSPI_RF file (the one that was just pointed out before) is the *ONLY* ModuleManager file to use the "&" symbol? Regards, Northstar

Well, hopefully I made you think about it! That was kind of the point. Although, you don't use the interceptor-ships as landers. The whole point of this Mission Architecture was specialization for efficiency and re-usability. You have a specialized ship for Earth-Mars transfers and another for Mars-Earth transfers: each of which you only need to accelerate to a Mars/Earth-crossing trajectory ONCE (and then can perform minor course-corrections each cycle with electric thrusters and Solar-Sails...) You have a specialized reusable lander that you can send down to the Martian surface and back again over and over... You have a specialized lightweight interceptor-ship that ferries crew to and from the Cycler Ships in relatively cramped and/or unpressurized conditions. You may even have specialized Nitrogen-tankers from Earth, or even better yet Propulsive Fluid Accumulator satellites that scoop CO2 from the Martian atmosphere and use THAT for propulsion around Mars and to the Mars-Earth return-journey Cycler Ship... (it might even make more sense for the Cycler Ships to rely on CO2-electric propulsion for course-corrections, as it takes less Delta-V to rendezvous withe the Cycler Ship near Mars than near Earth, as it is moving more slowly there...) Mass Drivers (electromagnetic catapults) fill just *ONE* niche in this infrastructure-driven paradigm. And there are a LOT of potential uses for them. To de-orbit landers around Mars, and assist with the ejection of interceptor ships towards rendezvous with the Cycler Ships (the Mass Driver can accelerate itself with de-orbiting landers, solar sails and CO2-electric engines: and eject the interceptor-ship prograde near periapsis of an elliptical orbit- thus reducing the Delta-V requirements the interceptor-ship needs to meet on internal fuel). To assist with launch of reusable landers from the Martian surface (even a few hundred m/s of initial speed helps dramatically), or assist in the launches of payloads from Earth for that matter (once again, the most cost-effective Mass Drivers only provide a few hundred m/s initial boost...) Or even, as I pointed out, to utilize garbage as reaction-mass for course-corrections aboard the Cycler Ship... Space infrastructure is cool stuff. Really cool stuff. It's a shame we have none of it- because often one type of infrastructure enables another (simple orbital propellant depots around Earth that allow larger satellites to reach Geosynchronous orbit by splitting their orbit-boosting fuel and the satellite itself into separate, smaller launches; in turn develop experience and expertise in transferring cryogenic fuels in orbit that will be useful/necessary for Propulsive Fluid Accumulators, for instance...) Regards, Northstar

Your response had be scratching my head in all kinds of ways (and not because it was that thought-provoking!) How could you possible compare space exploration (to some, the antithesis of religion) with religion? Space exploration is NOTHING like religion. Rather than pray that things work out and taking it on faith, we try to plan for every possible eventuality. Rather than seeking to gain perspective by looking inwards, we seek to gain perspective by looking outwards (or heading outwards, and then looking back inwards- aka. Earth from the Moon...) Rather than seeking the blessings of a mysterious and loving being, we seek the blessings of cold, hard, unloving science. I'm a scientists in real life, and honestly I have no idea how you Science & Technology Studies types can come up with such obscure/crazy ideas about the nature of science... (I've taken courses on the subject, by the way, so I'm not speaking out of ignorance...) There's nothing vague or undefinable about the benefits we gain from space exploration. The benefits to our technological progress have been very clear and concrete. And the physical benefits of mining some of the rare resources only found in space (Iridium and Platinum-group rich asteroids containing more of these elements than mined in all of human history, Helium-3 on the Moon, etc.) Not to mention the more mundane benefits of large-scale solar-farming if we can reduce launch-costs enough to make it competitive with current power-generation strategies (we'd need at least a 1000x fold reduction in costs for that, but I do believe we'll get there some day...) Space is the future. Space is God's promise to mankind (if you believe in Christianity/Judaism- there are certain passages that can be interpreted to mean the stars are our destiny...) Space holds more possibilities than you can imagine. And the sooner we get out there, the more the benefits of off-world colonization will snowball into even greater benefits still... If we start today, we might start colonizing Mars in 50 years instead of 100, and the benefits of that 400 years from now are too great to even imagine... Regards, Northstar P.S. Colonizing Mars isn't as crazy as it sounds. Human beings have lived in submarines and on ships for years at a time without going crazy- and even worse conditions were endured back in the Age of Sail. Do you think being limited to only a small pressurized habitat where you can go without an EVA suit on (remember, you can always still go and explore outside) would be that much worse than being in a tiny, smelly tin can deep underwater? At least on Mars you will have living/growing plants to attend to inside greenhouses... And we can afford/achieve it too: remember what I said about Space-X planning on selling $500,000 one-way tickets to Mars in 30-40 years...

So... Can we get about fixing all the files that this broke in RealFuels then? Regards, Northstar

I might release a smaller Mass Driver (the current one has a 3 meter aperture) if this mod becomes popular enough. It should be a simple matter of using the re-scale factor in the config and adjusting mass/force accordingly. I'd need to do some research on how Mass Driver power levels scale with size... But you can ALREADY use the Rock resource as reaction mass (if I can get the recoil working correctly)- just fill a container with it and eject it in the opposite direction you want to travel. Of course, right now recoil ISN'T working properly all the time, so that doesn't really work so well... You might end up pushing your ship in the wrong direction. Regards, Northstar

Same installation instructions as before? Easy numbers to calculate compared to some of the other calculations I had to make for Thermal/Electric ISP... Nitrogen fraction is just atomic (NOT molecular mass of N2) mass of Nitrogen divided by molecular mass of Ammonia: (14.0067)/(17.03052) = 0.822446995159 = 82.2447% Carbon Dioxide fraction is a tiny bit harder. The Sabatier Reaction is CO2 + 4 H2 --> CH4 + 2 H2O, but KSP-I automatically couples it with Water Electrolysis (much to my disliking, since H2O is actually *MUCH* more storable in RealFuels than O2- as RealFuels assigns it no boil-off: though it *should* as temperatures climb high enough when you get as close to the sun as Moho...) This means the NET reaction (and the one you need the mass-fraction for) is CO2 + 2 H2 --> CH4 + O2, so... (Molecular Mass CO2) / [(Molecular Mass CO2) + 2 * (Molecular Mass H2)] = (44.0095) / [44.0095 + 2 * (2.01588)] = 0.91607713869 = 91.6077% Summary: Haber Nitrogen mass-fraction: 82.2447% Sabatier CO2 mass-fraction: 91.6077% As you can see, the gasses that were not previously present as resources in KSP-I are the major mass constituents in each reaction. So it's not really practical to carry them from, say, Kerbin to Jool to act as seed mass for reactions with the H2 there, but it *IS* practical to harvest them from the edge of the atmosphere of Kerbin or Duna (using a Propulsive Fluid Accumulator- which can operate off N2 or CO2 for electric propulsion) and react them with Hydrogen launched from Kerbin's surface for some *MAJOR* mass-leveraging... Oh, by the way, I think I said something silly earlier about Propulsive Fluid Accumulators not being possible on Duna. That was *BEFORE* I did my research and discovered that not only is CO2 a viable electric propellant, NASA is working on a spacecraft that would essentially act like a Propulsive Fluid Accumulator on Mars *NOW* (both collecting CO2 and using it for electric propulsion) in order to obtain imagery from a lower orbit (due to their insistence of relying on solar cells, however, they had to optimize for Thrust with a Hall Thruster, and thus end up with *VERY* low ISP/efficiency compared to what is possible with ISP-optimized plasma thrusters: no exact ISP value was given in the NASA study, but it appears to be less than 1200s, meaning they only just cut even with the rate of CO2 gathering vs. drag...) So Propulsive Fluid Accumulators should *DEFINITELY* be possible using CO2-fed plasma thrusters (ISP of 2465.56 s) powered by nuclear reactors or beamed-power (MUCH better ratio of power to drag than solar cells) on Duna (20x thicker atmosphere than Mars, meaning useful CO2 densities for scooping can be found at much higher altitudes than on Mars), especially since PFA's operate at higher altitudes than the satellite being studied by NASA (which is meant to fly as low as possible so as to obtain closer imaging of the Martian surface) where orbital velocities should be lower (this is why solar-powered PFA's were shown to only be profitable in Earth orbit only at higher altitudes than nuclear-powered variants: because orbital velocity is lower in higher orbits, and atmosphere is thinner- meaning you can operate with larger scoop inlets without saturating the scoop, and have a better ratio of inlet flow to drag...) Thus, using PFA's to feed Sabatier Reactors in Duna orbit should certainly be profitable... Regards, Northstar

So, recoil is only simulated when you control the slug rather than the accelerator thanks to how KSP physics work? Now I'm confused... I guess that would explain why I always experienced recoil with my vertical launches, though- I always made sure to control the rocket at liftoff rather than the Mass Accelerator... Regards, Northstar

Awesome! By the way, on the RealFuels side of KSP-Interstellar/RealFuels integration, I noticed some more lines of code using the "&" symbol that aren't functioning correctly as a result (these lines of code were supposed to allow "LqdWater" to replaces "Water" and "Argon" to be storable in any tank that could hold XenonGas in RealFuels...) //Add water tank using KSPI water. (TO-DO: integration with TACLS water without trampling KSPI or TACLS) @TANK_DEFINITION[*]:HAS[@TANK[Kerosene]&!TANK[LqdWater]]:NEEDS[WarpPlugin]:FOR[RealFuels] { +TANK[Kerosene] { @name = LqdWater } } //Add Argon to all tanks that have XenonGas, as they function & store similarly. @TANK_DEFINITION[*]:HAS[@TANK[XenonGas]&!TANK[Argon]]:NEEDS[WarpPlugin]:FOR[RealFuels] { +TANK[XenonGas] { @name = Argon } } I've brought this particular issue to attention on the RealFuels thread. It might be worth submitting a pull request to fix these lines of code, though. I can't find any other use of the "&" character in the KSPI_RF config file (aside from the lines about the Methane Tank you caught earlier), so once this is fixed I suppose all the KSP-I/RealFuels integration code should be working correctly. Also, FreeThinker, would you have any interest in helping me wrap up the other issues (you commented on altering the rate of Ammonia consumption to match the change in resource density in RealFuels, but none of the other issues) with the KSP-I/Realfuels integration that I never got to before when working with Dreadicon? (specifically the issues you didn't comment on are: the KSP-Interstellar dedicated Ammonia tank needs to have its capacity increased when used to store RealFuels LqdAmmonia due to the lower resource density; the ISRU Refinery needs to produce Hydrazine instead of Monopropellant when the RealFuels module ModuleRCSFX is installed, which replaces "Monopropellant" with a variety of realistic monopropellants such as HTP and Hyrazine; and the ISRU Refinery's built-in tanks need to be insulated) Feel free to reply to me by PM, because I know how difficult it can be bouncing around a million threads trying to catch everything that is going on... Regards, Northstar

Darn. Also, some more lines of code that need "&" replaced with "," (if I am understanding this correctly- they're not working in 0.90 with the "&" symbol anyhow...) //Add water tank using KSPI water. (TO-DO: integration with TACLS water without trampling KSPI or TACLS) @TANK_DEFINITION[*]:HAS[@TANK[Kerosene]&!TANK[LqdWater]]:NEEDS[WarpPlugin]:FOR[RealFuels] { +TANK[Kerosene] { @name = LqdWater } } //Add Argon to all tanks that have XenonGas, as they function & store similarly. @TANK_DEFINITION[*]:HAS[@TANK[XenonGas]&!TANK[Argon]]:NEEDS[WarpPlugin]:FOR[RealFuels] { +TANK[XenonGas] { @name = Argon } } This code comes from the KSPI_RF config file. Given how widespread this problem seems to be, it might be worth searching the entire RealFuels code for any use of "&" in any of the files, and fixing it now so that we don't keep getting a trickle of bug reports about it... Regards, Northstar