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One small gripe I currently have is the lack of MK2 to small diameter adapter for methane-only fuel tank when building airplanes. There's a decent selection of methalox adapters so really just having methane and structural (e.g. no fuel) versions of those adapters would be nice, as currently the only option is to use a methalox with no oxidizer. Fairly minor but also seems like it could be pretty easy to add. Edit: also I realize tubes do offer a good "procedural" adapter solution for structural only. So definitely those are nice.

I am very interested in finding out more details of the Mars physical generation plant that will make the Methane fuel' for the return journey. How Efficient is the sabatier process? will it take years to generate the amount of fuel necessary for a return journey? what are the power requirements of the process? Will you need acres of solar panels or just a few square feet. What amounts of regolith are necessary to produce the required amount of Fuel? volume of water/cubic meter? Does anyone know who (what company) is working on this hardware? are there already working prototypes? I know that the ISS has one working now but it is small not the size necessary to produce the fuel for a return from mars mission . I have been following the discussion about mars missions for years and i have not seen any answers to these questions. I hope someone out there can point me in the correct direction! thanks

I want to add methane to Laythe's atmosphere, but i don't know if the kerbals could breathe in an enviroment with that much methane gas. Could they breathe?

Hello! I have some questions about FFSC, Methane and their combination in the Raptor engine (and it's vacuum version) SpaceX develops right now. First some links of my sources: http://www.scienceforums.net/topic/81051-staged-combustion-rocket-engines/ http://space.stackexchange.com/questions/3161/why-is-spacex-considering-methane-as-fuel-for-their-next-engine-the-raptor https://en.wikipedia.org/wiki/Staged_combustion_cycle#Full-flow_staged_combustion_cycle https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines https://en.wikipedia.org/wiki/Liquid_rocket_propellant#Bipropellants So, methane gains about 10s of specific impuls over rp-1 and has just about 20% less bulk density. If you have a look at the comparison of orbital rocket engines and sort it by highest pressure and have a look on the RD-180 1st stage engine: It has a atm isp of ~310s and a vacuum isp of ~340s but "just" uses oxygen-riched staged combustion with RP-1/LOX. So the isp of the Raptor engine should gain 10s from the higher isp of the fuel and 10s for using FFSC compared to the RD-180. So, if SpaceX optimizes the 1st stage version of the Raptor engine, they should get an isp of ~330s atm and ~360s vac, maybe even 370s. So i think the official isp of 321s atm and 363s vac are estimations for the first version or maybe for their tests and will be increased in the later versions. But as far as i know there is no official isp value for the upper stage version of the Raptor engine. So, let's have a look at the RD-0124. It uses the same combustion cycle as the RD-180 but has nearly half the camber pressure, a vacuum nozzle and uses RP-1/LOX. It has a vac isp of ~360s. I don't know why they used such low chamber pressure, maybe because they wanted to reduce weight. So with the full chamber pressure of oxygen-riched staged combustion it should get an vac isp of ~380s (compare Merlin 1D (280s/310s) with RD180 (310s/340s) and Merlin 1D Vacuum (~350s) with RD-0124 (~360s) --> +20s with full pressure). So, if they do FFSC with full pressure they should get around 400s vac isp for the upper stage Raptor engine. If they could archieve that, this would be the first chemical non-LH2 engine that reaches the 400s isp mark and nearly getting the same isp of some early LH2 engines. So my question: Is that a realistic calculation i did there? Or won't they use the full pressure of an FFSC (~31MPa)? And could you please list all advantages/disadvantages of Methane and FFSC compared to other propellants/engine cycles?