Cirocco

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About Cirocco

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    plain ol' engineer
  1. When you say Co, do you mean carbon monoxide or a Cobalt catalyst? Or something else entirely?
  2. I can't help you much beyond what has already been pointed out, what with english not being my native language, but I just wanted to point out this: This right here (as well as the entire 300 word essay that follows) is why I love the KSP forum-dwellers
  3. Absolutely, it depends on several factors including but not limited to: - the type of catalyst - temperature - time of exposure to the catalyst and therefore, flowrate through the reactor (higher flowrate = less time for the hydrocarbons to react) - hydrogen fraction in the mixture - isomerisation of the molecules you want to crack. Isomerisation means the degree to which the long carbon chains are branched. A hydrocarbon chain can consist of just a bunch of carbons in a line with hydrogens on the edges, but it can also be a line of carbons with a bunch of other lines of carbons branching off of it, kind of like a tree or a root system. High isomerisation means a lot of branching. (this isn't really a process parameter, but it also influences the type of product you get so I included it as well) Now as to how those parameters influence your process: The type of catalyst: catalysts are usually chosen for their activity. Intuitively, you'd think that high activity is good: high activity means more cracking which means more means more long-chainers broken down to short chains. Problem is that while this is true, your catalysts don't stop there. They'll crack everything they can get their hands on, including those nice new medium-length chains you just made. Therefore, current catalysts almost always have a trade-off: high activity means lots of stuff cracked but low selectivity (i.e. a lot of the stuff that comes out is too short and not usable) whereas lower activity means not that many long chains cracked, but more usable products. The currently used method is, if I recall correctly, to use a medium-activity catalyst, run a purification step, then another cracking and do another 2-3 consecutive steps like that to try and turn a maximum amount of heavier fractions into usable ones. It's energy-intensive but it works. But this problem is also why researchers are trying to look for more selective catalysts that still retain a high activity (like we looked for in my master thesis). Temperature: higher temperature means higher activity, more cracking (though again, often also less selective cracking) but also more coking. Coking is a problem where you essentially "burn" the carbon chains and turn them into soot ("cokes", in the jargon). These cokes then deposit onto the catalyst pellets and effectively clog up the pores into which the long chains insert themselves to be cracked. So again, it's about finding the balance between activity, selectivity and coking. You can regenerate the catalyst by literally burning off the cokes, but this is also detrimental to the catalyst. The less regeneration needed, the better. In short: high temperature means high coking, low selectivity and high activity. Low temperatures means less coking, less activity but higher selectivity. Exposure time (flowrate): As mentioned before: cracking catalysts tend to crack everything they get their hands on. So the longer a molecule spends in the reactor, the more chance it has to be cracked. by adjusting the flowrate and pushing the (gasified) long-chain molecules faster or slower through the reactor, you can favor a certain amount of cracking steps. In short: high flowrate: less cracking but also less overcracking and less useless methane produced. Low flowrate, high cracking, but also more overcracking and more useless methane produced. Hydrogen fraction: (hydro)cracking requires hydrogen: you break apart a C-C bond and stick a hydrogen on each end of the severed bond to get C-H H-C. As with any chemical reaction, you can push the reaction to one side or the other by supplying an overabundance or shortage of one of the reagents (in this case, either long chain hydrocarbons or hydrogen gas). Lots of hydrogen means less coking and more cracking but, as always, also more over-cracking and methane production. Less hydrogen means less cracking but also more coking. You also need to take into account that hydrogen gas costs money and it also has a tendency to activate any sulfur or other impurities in the initial mixture. Sulfur gets turned into H2S-like molecules and those absolutely murder your catalyst. You can literally render an entire reactor useless in minutes if you run highly polluted oil through it. Isomerisation: A bunch of long-chain molecules which are just a single line of carbons stuck together are extremely hard to crack down the middle, they'll just fragment at the edges. As a rule of thumb: the more "branches" a carbon chain has on a certain point, the easier it will break at this branching point. Because of this, the more modern processes of cracking are a two-step process: one reactor first branches (isomerizes) the long chains in the middle(ish) and the second reactor is the actual cracker, in which the long chains will be more easily be cracked in the middle instead of at the edges, because they have more branches down the middle. Petrochemistry is very much a story of percentages. It's almost impossible to get a nice, clean reaction A + B --> C. It's always A + B --> mostly C, but also a bunch of D, E and some F in various percentages. The trick is to try and get as much usable C as possible and minimise or somehow recycle the production of D, E and F. So in answer to your question: the process parameters influence mostly the degree of cracking of the mixture. And the degree of cracking influences whether you get short-chain gasses or medium to long-chain gasses/liquids. Lots of activity = lots of gasses such as methane, ethane and the like. Less activity = more molecules in the reagions of C10-15 (liquid, usable stuff). Whew! lots of text! but i was happy to once again dust off my petrochemical knowledge Hope it helps!
  4. My bad, I misremembered and wasn't clear enough in my description: yes, a lot of the reactions are exothermic, but they still need high temperatures to happen at a reasonable rate. Essentially: the reaction produces heat, but it only starts happening at a reasonable rate at high temperatures (200°C and up). So you still need to heat the reactor all the time because even though the reaction is exothermic, you lose heat because you are constantly evacuating the heated products and pushing fresh, "cold" reagents into the reactor. If those reagents are not heated then the reaction slows down and falls to a n ear standstill. As for recycling the energy: it's possible to recycle some heat using heat exchangers, but it's not worth it to try and re-introduce it into the process: it adds too much complexity for very little gain. It's far easier to just burn a bit more gas. That being said, using the waste heat to heat people's homes or some other process that doesn't require super high temperatures is perfectly feasible. Well there's your problem. Waxes are reeeeeaaaaaally hard to crack properly into usable fractions. Heavy hydrocarbon chains, sure, you can crack off a couple carbon atoms from the edges and turn them into lighter fractions and gas (which is usually just burned with a large torch on top of the refinery). But with waxes, you need to selectively crack the heaviest ones down the middle without breaking up the rest of the chain and without cracking the lighter ones. And that is exactly what is so hard: cracking long chains without cracking the small ones into useless, short-chain gasses. Add to that the energy requirements being so restrictive, and there's your explanation for why this process isn't widely used. It's simply still cheaper to just drill it up.
  5. Okay, I just only now discovered this thread (very sad about that btw) so I haven't read everything here, but I believe I can be of service here. Here's why: I graduated about 6 years ago as a catalytic engineer. Half of my education was basically geared towards petrochemistry and my master thesis was about trying to find a suitable catalyst and process to selectively crack long parafins (such as the ones from a FT-reaction) into diesel-length molecules. For those interested: we tried a process where we first tried to isomerize the parafins in the middle by running it over a zeolite (ZSM-22 if my memory serves me correctly), and then trying to selectively crack them over a Pt /sulfated zirconium-silicate catalyst. Results were partially successful. So, with that out of the way, here's some difficulties that you encounter in the process and hidden costs which I believe have not yet been accounted for: - FT product distribution is heavily skewed to the long-chain parafins in absolute numbers. Yes, the peak of the distribution can be pushed more towards the diesel range by tweaking the process parameters and choosing the right catalyst, but when you look at the volume beneath the curve (which gives you an idea of the volumes produced) that tail end is still huge. Economically speaking, I don't think FT reactions are viable on a large scale (yet) due to the immense amount of by-products and energy required to perform in and purify the product. To make this economically viable you need to (as I believe has been discussed in this thread already) find a way to break down the long-chain fraction into usable, shorter chains. Which leads us to a second problem: - Long-chain parafins have high melting points and therefore have a nasty tendency to congeal and clog up your reactor vessels and tubings. This stuff is not easy to work with, I speak from experience. Back when I did my master thesis, I was told there weren't that may reactors in the world that could handle these waxy parafins because any cold spot in the reactor or tubing thoroughly messes up everything. - Any chemical reaction, especially petrochemical ones, always yields a slush of different chemicals. Sometimes the slush is very, very skewed to one side but in FT reactions, it is not. You need to purify it, usually through distillation. But distillation requires energy. Which leads us to the biggest hurdle: - Energy: any FT reaction is an endothermic reaction. Even low-temperature FT synthesis requires temperatures above 200°C, with high-temperature FT sometimes going up to 400 or even 600-700°C ranges. That means a LOT of heat which is usually obtained through burning natural gas. Simple thermodynamics will tell you that in practice, you will always need to invest more heat into making something than you can extract from it by breaking it apart. The energy required to maintain the heat for the FT reaction and the distillation of the products is far and away the biggest cost in the process. In summary (TLDR): - FT pocesses always produce a large fraction of waxy, long chain parafins. These are almost worthless from an economic standpoint, clog up your reactor something fierce and need to be distilled off. Cracking them and turning them into usable substances is not a bad idea and has been the subject of quite a lot of research already. Nothing I know of can do it selectively and cheaply enough though. - FT processes and the distillation required afterwards require huge amounts of heat. Far more heat than the useful energy you can extract from your produced bydrocarbons by burning them. This is the big hurdle: if you can find a way to cleanly and cheaply produce energy, you can turn this process into an economically viable thing. However "cheap and clean energy" is basically the holy grail of energy production. If you find a way to do this, then you've basically solved the global warming problem as a whole. I believe this is also the big hidden cost you have not incorporated into your calculations. And that is not mentioning the heat it will require to extract CO2 and turn it into methane/syngas. I do apologize if what I said has been discussed already, like I said, I haven't read the entire thread, but this topic of synthetic oil production is one that was very alive (and has been for years and years) in my faculty. I listed the two main arguments for why it doesn't work (yet) above. If economics change through scarcity of oil reserves and technological advancement in catalytic technology and energy production, then it could work. Just not yet.
  6. I'm fairly certain this is common practice but I haven't seen it on this thread yet. Similar to what g00bd0g does: put one flag on each side of the runway and name them "runway sea side" and "runway land side" or similar. You can use them to line up properly as well as get an idea of the distance to the runway.
  7. European webcasts are indeed different from american ones. NASA has been televising their launches and operations for a lot longer than ESA, so they have a lot more experience with it. American broadcasts are usually commentated by PR people, ESA more often puts engineers and scientists directly in front of the camera. US broadcasts also tend to give more concise, bite-sized bits of information. ESA wants to say everything correctly and with all the explanations around it, which means it comes across as much more stuffy and forced. It's also a difference in style I suppose but personally, I prefer the American style of broadcasts. This, in my view as a European, is a field where we can definitely learn a thing or two from our American colleagues. Although the French do have an awesome word for "liftoff" in my opinion EDIT: looks like a successful liftoff
  8. Hey all, just a thread to let you all know that ExoMars (joint venture of ESA and Roscosmos) is launching today. Launch is scheduled at 9:31 a.m. GMT (which is one hour from posting of this thread). You can watch the webcast here: http://www.esa.int/Our_Activities/Space_Science/ExoMars/Watch_ExoMars_launch arrival on the red planet is scheduled for 2018. cheers, Cirocco just noticed that there's already a thread for this, my bad. Mods, feel free to kill/lock/merge this one.
  9. correct, I wasn't clear enough on my meaning, I meant "edible parts as big as possible", but even that is not entirely right. The most correct would indeed be something along the lines of "most yield". Thanks for the correction. Bioreactors! Oh god such memories to my time at university. Good times, good times... Thanks for that
  10. On the whole mildew debate: while we do indeed breathe bacteria 24/7, I tend to agree with the fact that in a completely closed environment there's a risk of elevated concentrations. People on earth don't live 24/7 in an enclosed area with what are essentially a bunch of incubators. There are a bunch of micro-organisms that are totally harmless in low concentrations might become a problem in higher concentrations. That being said: mildew is a fungus and any airborne fungus could easily be filtered out of the air with high-efficiency particle air filters. I believe there also exist certain catalysts that can be used to kill any bacteria and fungi that are caught by the filters (they break down the membranes). They're currently being investigated (and possibly even already used) in air-conditioning systems of large office buildings to combat "sick building" syndrome. So while mildew and other possible pathogens can be a concern and certainly merit attention, I don't think that there's much there that can't already be solved with currently available technology. (semi-)isolating the greenhouse and running air filters seems like a perfectly acceptable solution. In response to the OP: 1) As to what kind of achievement this is compared to the cabbage and tomatoes: well, any plants that we can grow is good news. Not sure why zinias were chosen, you'd have to ask the project engineers at NASA 2) for long-time journeys: there's definitely something to be said for growing your own, fresh food on month-long away missions, both for psychological and nutritional reasons. I don't see fresh gardens becoming the main food source on long missions (way too much stuff to and weight required to send up into space and push around), but they could definitely be a supplement. Maybe like something the astronauts would eat once every few weeks. 3) what kind of traits would we need to change to grow in zero-g? Not that much I think. We've managed to grow pretty much unaltered (to my knowledge) cabbage/lettuce on the ISS, so just to grow it I don't think much alteration would be required. What we do might need to do is optimize the growth rate and yield. Grow stuff as fast and big as possible with as little space and weight as possible. But that's also kind of already a goal here back on earth: make better crops with less energy invested.
  11. Strangely, this is not the first time I've considered martial arts in zero-G. For the sake of argument, I'm assuming that the only factor here that is different from earth-bound martial arts is the gravity. This means the fight is performed indoors, spacesuits are either not worn or sufficiently supple to allow (almost) complete freedom of movement, life support is either not an issue (indoors with the entire room/station under life support) or sufficiently small and fortified to the point that trying to disable it bare-handed is futile and no RCS thrusters or mechanical means of movement are possible/allowed. Everything is done through your own human strength. I'm basically imagining a normal dojo/training room inside a station where the participants wear normal sparring outfits suited to their discipline. Only gravity is different. Alright, now that we have that out of the way: I think that a martial arts contest would consist of the two (I'm assuming 1v1) combatants hopping around the edges of the room, vying for a good position, and at times go in for grappling bouts. Those bouts can then be broken up by one the combatants pushing off hard against the other to send them both flying in opposite direction, after which the whole thing starts over. free-floating grappling bouts may occasionally occur, but fights at the edges of the arena seem like they would occur most commonly. The main thing to note in zero-g is that newton's third law is very much still in effect: ever action has an equal and opposite reaction. Every punch you throw sends you backwards as well. That also means that your punches hit a whole lot less hard then on earth. On earth, when you throw a punch, the fact that friction and gravity keep you and your opponent in place means that a whole lot of the energy in the punch is translated into deforming the opponent's body rather than pushing it away. In space, that friction and gravity isn't there (assuming you're both floating) so a lot more energy will be put into moving the opponent and less into deforming (hurting) him. It's kind of comparable to hitting a falling bowling ball with a baseball bat vs hitting a pingpong ball with the same bat. In case of the bowling ball, stuff breaks. In case of the pingpong ball, it flies away relatively intact (this comparison is not ideal by ANY means because the reason behind it is inertia instead of friction/gravity, but it's the best I could come up with). So how do you punch someone in zero-g? you hold him by an extremity with one hand and hit the center of mass with the other (or another body part, but center of mass seems most efficient at first glance). This way you stop him from moving away and all the energy you put into the punch is translated into trying to deform the opponent's body: one impact on the stomach, the other is a pulling force on his arm. Spinning someone is a very interesting idea as it uses the opponent's mass and inertia against him. Disorientation and dislocating joints is a great way to exploit zero-g environments, but there is one problem: if you try to spin him, you'll spin in the opposite direction just as fast unless you have something to brace against. So disorienting by spinning only works if you can get him to spin without doing so yourself. And that, again, means bracing. TL;DR: In conclusion: there's two very important things (according to me. I'm in no way an expert on zero-g fighting, I could be wrong on this): 1) bracing yourself: if you are braced against something and the opponent is not, you have the advantage. You can push and twist the opponent around, and he can't do the same to you (providing that whatever you are bracing against is heavy enough to slow down your inertia by a whole lot, like the room/station wall). 2) no straight up punches (unless you want to separate from each other): any punch thrown without holding the opponent will result in both of you flying in opposite directions. Grappling is key when you want to hurt him, getting out of his grapple and punching/kicking off is critical when you are in a bad spot and want to reset the fight. There's actually a manga that i've read once that does quite a lot of theorycrafting on martial arts in space and zero-G. I think it's called "battle angel alita" in the english translation. Don't let the title put you off, it's actually quite an interesting read. Enjoyed it quite a bit. whew, lots of text. Hope if was interesting though EDIT: one thing I totally forgot: weight (or rather, inertia) of the fighters is a HUGE deal in zero-G. a lightweight fighter can be as strong as they want, there is no way in hell they'll do much to a sumo-wrestler. The reason for this is, again, every time they try to throw a punch or spin the opponent, they'll spin or be thrown back too. Only, if the inertia of one of the two fighters is significantly lower than the other, that one will spin/fly a whole lot faster. So if they're freefloating, a lightweight and sumowrestler trying to spin and disorient each other will result in a fast-spinning and motion-sick lightweight and a gently rotating sumowrestler. Lightweight MUST try to brace, sumowrestler can just go in without bracing. Strength isn't really a big factor since all movements can be done at a fraction of the effort they would cost on earth. So yeah, space martial artists would benefit from being heavy. Space sumowrestling is the future ladies and gentlemen.
  12. ah, the old "is X cheating?" question. I refer you to the helpful diagram I use for all these threads: Is X considered cheating in KSP? a handy guide: do you yourself consider X cheating? --------yes-------> X is cheating. --------no--------> X is not cheating.
  13. stage separation success and second ignition is confirmed. Damn That was tense for me...
  14. T minus 1 min. I can't believe I stayed up till 2:30 am for this...