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  1. If basically any part of the pod fails, it doesn't matter if the parachute works or not, you will die before you can come down, if not on the way up. And you can absolutely pin-point what part in the pod is responsible for the failure, that's part of what telemetry is for. Even for a dumb chasis (which a pod very much is not) it is still larger and hence requires more material and a larger workforce to construct, and so should cost more.
  2. Yeah. As much I would like a total overhaul of the entire game balance, that is a lot of work. Part cost should be one of the easiest to rebalance since its basically self contained, which is why I focused on it.
  3. Its not the actual cost of the vehicles, and this is arguably just to not hinder new career mode players. The prices of parts are weird in relation to each other. That is true, but that also applies to every other part in KSP, not just engines. Relative pricing should still hold if all parts are manufactured at equal rates. The engines in cars and aircraft are good examples of this in action, as both are very much mass produced and engines still make up a large fraction of the total cost. The actual material costs should be minimal in comparison to the manufacturing process. Rolling cone shapes also isn't that much harder than a cylinder. You'll need a new form, but that goes for tank diamters as well, so itsn't likely to increase the cost that much. Yes, parachutes would be expensive to certify. But the same goes for a command pod, which is also larger and much more complicated. Not really, and that's kind of the point. You'd expect the price of your vehicle to be more than a passing thought in a gamemode about paying for your rockets, both for the players and the developers, but that isn't really the case right now.
  4. Part cost isn't something that is normally brought up with regards to balance or realism. Part cost is only important in Career, and even in career, it isn't really that big of a concern, so its understandable why it isn't brought up that much. Still, it is very much a part of the game that should be looked at, as there is a lot that can be improved upon. Before diving into KSP costs, it's good to look at the costs of components in real launch vehicles. Now, pricing launch vehicles is surprisingly difficult, but fortunately just relative costs for parts is all we need for now. For the planned Vulcan launch vehicle, it is estimated that the engines and related components are around 65% of the cost of the first stage. For the Falcon-9, propellants only make up around 0.3% of the costs of the launch vehicle. Now of course, we need to keep in mind that these values might not be accurate for all launch vehicles, especially things that are not conventional rockets, but hopefully its good enough to give a rough idea. From this, it seems engines are the most expensive part of the launch vehicle, and particularly the first stage, with fuel being only a minor contribution. Looking at the first stages of various stock and dlc vehicles, engines only comprise around 15-55% of the first stage cost, lower than what one might expect. Fuel costs are much higher than expected, between 5-30% of the first stage. These two departures from realism could be resolved by simply reducing the cost of liquid fuel, oxidizer, and probably also monopropellant for good measure. In fact, liquid fuel is currently 4.4 times as expensive as oxidizer (0.8 funds/unit vs 0.182 funds/unit), so even just reducing liquid fuel and possibly also monopropellant would work (monopropellant has a cost of 1.2 funds/unit). Now you may have noticed that those price fractions varied a lot, and the reason for that is aerodynamic parts, with control surfaces in particular. As a point of comparison, the smallest and cheapest control surface is the Elevon 4 (the small one), which has a steep cost of 400 funds. This is more than a LV-909 Terrier (390 funds), and two-thirds the price of a Mk1 Command Pod (600 funds). Now, Elevon 4 costs the exact same as an Elevon 1 (the normal one), so its really only tied for cheapest control surface, but that should show that something is wrong with these prices. The Elevon 5 (slanted one) is more expensive than the Elevon 3 (large triangle one), despite giving less lift and being unlocked in the same tech node. The AV-R8 winglet costs more than the Tail fin, despite the Tail fin giving more lift and deflection, and being unlocked in a tech node of the same price. Now, these are not the only oddly high prices with regards to aerodynamic parts. Wings are slightly less expensive than control surfaces, but not by much. The AV-T1 in particularly is especially crippling, costing a whopping 500 funds for a small wingless. This is 5 times the cost of similarly sized wings unlocked not soon afterwards, so they are clearly a rip off. Now, the probably-too-high costs of some of these wings can be excused by the fact that they are capable of withstanding reentry heat, not something most aviation wings need to handle, which can be seen with the cheaper but less capable FAT-455 series of parts. Nosecones, especially the smaller ones, are also probably a bit to costly, with costs approaching those of engines in the same size. Moving to structural parts, for the most part they are rather inexpensive, which would be expected, but there are some oddities. The Structural Fuselage actually costs more than the Mk1 Liquid Fuel Fuselage its based on (when empty), despite it presumably being far easier to manufacture without an integrated fuel tank. The size adapters are also pretty costly, being around as expensive as nosecones. The multicouplers have some odd prices too. The 1.25m tri and quad couplers are both more expensive than their 2.5m counterparts, with the TVR-2160C Quad-Coupler costing 2000 funds, compared to the TVR-400L Quad-Adapter costing just 800 funds. There are more examples of oddly high/low prices. Mk16 parachutes are nearly as expensive as the Mk1 command pod, radiators cost close to or more than the ISRU parts they are designed to cool, J-90 Goliaths are less than twice the price of the J-33 Wheesly while having a built in air intake and side mount, the Clamp-O-Tron Jr. being over twice as expensive as the regular Clamp-O-Tron, the list goes on. Hopefully this is enough to clearly show that prices need some revisions, if not a total overhaul. It would nice if this would be done in KSP, but knowing this community, I'm sure people would much rather the time be spent on something more exciting.
  5. Two things I noticed about the FX-2 and FX-3 fusion reactors that may not be the intended behavior: 1) D-He3 mode consumes 10 times as much fuel as D-D mode, but only puts out twice as much power. 2) Assuming I did the math correct, the specific energy of the D-D and D-He3 fuel cycles are less than that of enriched uranium in the NFE reactors. For this, I used a two part formula. One for finding the energy per unit of fuel (generated power/ fuel use), and the other for converting in game units to kg (mass/units) - The NFE reactors give fuel specific energies between approximately 78 to 131 GJ/kg, varying between the reactors (which interestingly gives electrical efficiencies of around 3-5% for 3.5% enriched uranium) - In D-D fusion mode, the FX2 and FX3 have fuel specific energies of 23 and 28 GJ/kg respectively, between a third and fifth that of NFE reactors. Interestingly though there is still a use case for the D-D reactors despite their lower specific power (not counting radiators) and fuel specific energies than the NFE reactors, and that is that their fuel is comparatively inexpensive. - In D-He3 mode, the FX2 and FX3 have lower fuel specific energies of just 7.3 and 9.1 GJ/kg, although the high specific power makes them useful either way. Hope this helps
  6. A relevant method for reducing thrust without throttling down http://www.projectrho.com/public_html/rocket/realdesigns.php#id--Basic_Solid_Core_NTR--Cascade_Vanes This design was considered for use in solid core nuclear rockets, but some magnetic equivalent might be feasible for more energenic propulsion systems.
  7. You can get the same effect by using the moon itself as a gravity tractor for earth. This simplifies the design, and saves both the tides and venus. A large solar laser could be used to push the moon, or even the earth itself, further simplifying things and allowing for much faster timescales.
  8. A relevant video by Isaac Arthur on the logistics of moving planets Hope this helps.
  9. Well yes, but actually no. Like all things, it's complicated. So first off, my one and only defence what you were watching. We can do a pretty good job correcting for observation bias, as its something scientists know about going into things, and they have to work around it on a regular basis. When correcting for the planets we know we can't observe, and using the planets we can see to gauge their likelihood, we still find that most exoplanets are larger than Earth. That being said, there are still a lot of assumptions and misconceptions that can be unpacked here. Most of the exoplanets we've found were found by the kepler spacecraft, which was geared towards looking at K, G, and F type stars. These only make up 20-30% of all main sequence stars. The remainder is almost exclusively M type red dwarf stars. So we still lack a good census of what planets are like around these smaller, more abundant stars, which the TESS spacecraft and JWST will hopefully address as time goes on. From what we do know, it seems that planet mass may be loosely correlated with star mass. So worlds around these smaller stars will generally tend to smaller. In a further miscommunication, there is actually a frustrating amount of ambiguity in the compositions of exoplanets (even those with well defined densities). This is most apparent with mini-neptunes, which could either be rocky worlds with an extended hydrogen atmosphere, or water rich ocean worlds with little or no hydrogen. For smaller planets below about 1.5 Earth radii, where hydrogen is almost certainly not present, their compositions are slightly easier to pinpoint. As we don't know for certain how much iron an exoplanet has, or how much of that iron is oxidized, there is a lot of room for volatiles like water and carbon dioxide to sneak into a "rocky" planet's composition. In the small fraction of rocky planets with known and well constrained densities, most can allow for anywhere from 0 to 10% of their mass in water (for comparison, only 0.02% of Earth's mass is water). This doesn't seem bad, until you realize that an earth mass planet (or larger) only needs to be ~1% water for it to have a global ocean with a seafloor covered in high pressure ices, which would remove the rock-water interface which is thought to be a key requirement for abiogenesis. Also these ocean worlds have much smaller habitable zones, quickly going from frozen iceball to boiling steamhouse, much like the faucets in most buildings. What makes things worse, is that larger rocky worlds may also be unsuited for life. Planets larger than 2.5 earth masses will likely lack tectonic plates, and possibly magnetic fields as well. While neither are strictly required for life to develop (Earth's magnetic field and plate tectonics likely started after life developed), they are very very nice things to have for a developing biosphere. The thick atmospheres these worlds will have will likely make up for the lack of a magnetic field for surface life, and the larger masses of these planets will prevent atmospheric escape in the habitable zone. Hope this helps.
  10. Fusion rockets are in fact easier to achieve than fusion power. This is because a fusion power plant needs to break even, making more energy than it uses. On the other hand, while a self sustaining fusion rocket would be very good to have, especially one that could be tapped for power, they aren't necessary. There are some designs for fusion rockets that use a fission reactor to provide power for their operation.
  11. Well yes, but actually no. You could, but it wouldn't be an ion thruster anymore. Ion thrusters specifically use electricity to energize their propellant, rather than through heating by use of fusion or antimatter. In principle, you could use an ion engine powered by a fusion reactor and antimatter fuel cell, but it would be better in almost every circumstance to just heat a propellant through fusion or antimatter instead. Thermal propulsion would be lighter, simpler, and would give higher performance. The only downside is that these thermal systems wouldn't be able to change throttle as quickly (needing to heat up an entire reactor versus using ultracapacitors to regulate power) This might make fusion/antimatter electric propulsion feasible for RCS, but not for a main drive.
  12. Realistically, any form of space elevator, space tower/space fountain, launch loop, or orbital ring will be more environmentally friendly in the long run as no propellants are needed, and all components are multi use. But, its nonsensical to say that any of these methods are "propellants". The original question was about the most eco-friendly propellant, not the most eco-friendly surface to orbit transportation system, or even the most eco-friendly rocket design. These are all complex and intertwined questions for sure, and the question is framed in such a way that some pollution will be unavoidable from the production of the launch vehicle and the propellants. It is even fair to assume that a "nuclear space faring civilization" is one that uses nuclear propulsion (either in part or exclusively), which may make any chemical propellants considered irrelevant if that is the case. Based on all of this, and trying to pool everything together, here are 4 answers previously suggested that could be valid answers. LH2 would be the cleanest nuclear propellant, if only the impact of the launch itself is considered. H2O (water) would be the cleanest nuclear propellant if the impact of propellant production is considered, with minimal effort to produce. It remains a possibility for LH2 to be cleaner than water if there are significant advances in how its produced, but currently this is not the case. Hydrolox would be the cleanest chemical propellant, ignoring the impact of propellant production. Either methalox or hydrolox would be the cleanest chemical propellant if the impact of propellant production is included. As methane is more naturally abundant than hydrogen, and hydrogen typically being produced from methane or water, methalox may be cleaner overall. But this also depends on how these technologies would develop.
  13. First off, if a civilization's goal is to preserve the environment, monetary cost will be a non-issue. And biogas isn't even cheaper than minning, thats why we still mine. Secondly, Biogas is biologically produced methane and methanol, as are all fossil fuels. What makes biofuels "cleaner" than petroleum fuels isn't that they're a different chemical, its that biofuels are made from the carbon already in our atmosphere, rather than carbon which has been stored in the ground for hundreds of millions of years. Burning biofuels simply returns the CO2 that was used to make it back into the atmosphere, whereas burning natural gas adds more in. Third, the Kværner process is another way of turning methane into hydrogen. The difference is the waste product. Steam reforming creates ten times as much CO2 as it does hydrogen. The Kværner process produces no CO2 as a waste product, and so less greenhouse gasses. The kværner process instead creates carbon dust, which can be stored and removed from the carbon cycle. When taken as a whole: CO2 is taken from the air by plants to produce biomass. Some of this biomass is burnt, generating power and turning it back into CO2. The rest is put through the kværner process (using the power generated from before) and converted into hydrogen and carbon. The carbon is not returned to the air, so there is an overall net decrease in atmospheric CO2.
  14. Which is why I suggested running it off of a biogas powerplant rather than natural gas. Also its abilty to sequester carbon in elemental can reduce, or even give it a negative carbon footprint. Interestingly, the Kværner process is very similar (and possibly identical) to what happens in a nuclear rocket when you use methane as a propellant, only the carbon soot builds up in the engine, which can cause blockages or affect the neutron moderation in the reactor, and isn't desirable in that situation.
  15. Introducing the Kværner process, which converts natural gas or biogas directly into nearly pure carbon and hydrogen. A carbon neutral biogas powered and biogas fueled system could be implemented relatively easily by any eco-conscious future civilization if so inclined. As a bonus, the carbon could be used in ceramics, composites, or high strength carbon allotropes like carbon nanotubes and graphene. So technically it would be a carbon sink, rather than simply carbon neutral. Much more broadly speaking, an eco-conscious space fairing future civilization could migrate all power, manufacturing, and living space off of Earth to preserve its environment. As I mentioned previously, though in a less serious way, you can't pollute an environment that isn't there. Because of this, any environmental impact caused by the manufacturing of any of the rocket's systems (fuel, structure, power, electronics) could be disregarded entirely.
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