So, you're tasked with designing the power grid for a space colony... AC or DC? - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: September 16, 2017, 05:45:11 pm
content: Hi guys,I've gotten into a discussion on what kind of voltage/frequency would you choose for a completely new grid. Let's assume this situation:You are tasked with designing/choosing a power grid - from power source all the way down to the end user.There is no ancient history to be compatible with (no old lady's washing machine will explode on Switchover day, no vintage equipment will burn their transformers, no billions will be needed to install a second plug into every home, no elevators will shoot through the roof).You have the equivalent of current technology available (cheap switched power supplies available, converters of all sizes, frequencies and voltages available) - as such the grid may be as high tech as you like, but you should take into account things like price (or rather resource usage, availability, maintainability) in the long run.The standard requirements are assumed - you want it reliable, safe and capable of transferring enough power.Other considerations should be also taken into account, like resource usage (copper is fine, unobtainium fine mesh wires are not), practicality (waveguides will suffer low losses, but are impractical for a host of reasons)...The Space colony scenario is a bit specific in that you need to also consider the repairabilty and 'botch friendlyness' of the system - you can hand wind a transformer and a motor, but you need a semiconductor fab to make a rectifier diode. Lets assume that you can make replacement parts for everything at the moment - you can have a semiconductor fab equivalent as well as the means to create anything that can be created today.So, what would you choose?AC of a compatible frequency/voltage?AC of a custom frequency/voltage?DC?A temporary solution for the needs (say, high frequency 480V @ 22kHz AC, in which you get insanely small transformers with no extra components, but at the cost of not being very friendly for longer length power transmission) and when/if the colony grows you switch over to something more practical for a bigger settlement?It seems to me that DC might be the way to go in this case - the conversion system between local and long grid might be technologically difficult, but the efficiency should be greater. Or maybe, with the space colony scenario a temporary solution (ONE standard, not 500 different frequency/voltage/plug combinations) might be better, and when things have stabilized, move to DC.The advantages in DC at home are that you avoid rectification which currently used devices do to AC anyway, and if needed, convert back to AC at any frequency. And it's not as though there is no such thing as a DC motor... Switched power supplies operate internally with switched rectified DC anyway. From the available power sources you can get DC directly, so that removes one little step and you get better efficiency.As for DC for long range transmission, I'm not sure. HVDC (https://en.wikipedia.org/wiki/High-voltage_direct_current) is used for insanely high power distribution, but I don't know about the middle of the range (say, transferring 100kW - 1MW).What is your opinion?Thanks,David

author: SeanB
author_rank: Super Contributor
timestamp: September 16, 2017, 06:02:26 pm
content: Given that most of your power sources will be DC, solar panels, some form of battery for storage, using DC will be likely the most efficient to use. Drawbacks are they your protection devices will have to be a lot more robust, and that they will also have to be rated for operation from atmospheric to vacuum levels without arcing over internally, and operate and safely disconnect over that range. Same for switches and connectors, you probably will be wanting to have a low voltage bus for local distribution per module, and a higher voltage bus ( and DC DC converters) for interconnects, along with the interconnects at both ends able to operate as either step up to drive, or step down to convert, along with being robust, rugged and radiation hardened as well.You probably will be settling on a 48VDC rail, simply because of the plethora of switchers with 60VDC max input ability from the telecoms sector, and with this also having existing high volume protection devices as well, with the ability to break safely. Your solar arrays as well will easily do this as charge, and you will also have battery modules and charge controllers available in assorted chemistries, probably some space rated lithium or silver cells, as the biggest challenge will be mass and the cycle life. higher voltages pose a risk of corona discharge , and lower voltages the increased mass of copper, though you could get away here with silver coated wiring ( as most likely the wiring will all be either PTFE insulation either foamed or solid, and with polyamide there as well) or for large conductors aluminum busbars.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 16, 2017, 06:18:04 pm
content: 1M Watt at 48 volts is over 20,000 Amps. That's some massive copper. But it can be a spread system where every X inhabitants have a solar cell and a battery, at which case the wiring is much smaller.Also, if the inhabitants consume as much power as a US home today - I'd expect 48VDC to be a substantial fire risk (albeit one can have better connectors). For example, an 1800W space heater is almost 38A - a fire hazard.I think the missing components are:1. What is the size of the colony, and how large will you expect them to be during the lifetime of the system?2. What is the allowed/allocated energy quota per capita (do they need heating, AC, do they make Ice Cream....)3. What % is for overhead (government, public buildings, farming, etc).4. Distances - is it a colony spread over large distances or are they in a dome?An AC long haul system simplifies conversion and is vastly easier top maintain. Albeit it can be at frequencies somewhat higher than 50/60Hz to reduce losses in transformers. The rest probably DC.

author: IanB
author_rank: Super Contributor
timestamp: September 16, 2017, 06:27:09 pm
content: The important thing you have left unsaid is the size of this new "grid"? Is it the size of a large building, a neighborhood, a small town, a large town/city, or a group of cities? It is the size and scale that shifts considerations between a local distribution system and a geographically large transmission network.In the early days of electricity each city or neighborhood had its own local generating plant. This was phased out in favor of large, remote generating stations on a grid due to economies of scale, especially with coal fired plants. But these days with renewable energy the balance is shifting back to lots of smaller micro-generators.In a possible future where there is no history to worry about, local generation near to the point of use in small, unconnected islands might make sense. There is still the issue of needing medium voltages in the 10 kV range to convey power over more than very short distances, so step up/step down converters can't go away, and maybe transformers and AC will still make sense. Aircraft use a frequency of 400 Hz to keep down the size of transformers, and this could make sense for a new utility power system rather than the 50/60 Hz we are accustomed to.

author: woody
author_rank: Frequent Contributor
timestamp: September 16, 2017, 07:09:13 pm
content: Size doesn't matter (or so I'm told), because space is cold, So cold that you probably can use super conductivity. Thousands of amps over miles of AWG30

author: SeanB
author_rank: Super Contributor
timestamp: September 16, 2017, 07:29:09 pm
content: I would still use a DC interconnect for long distance, as even a 400Hz transformer is heavier than a 1MHz switcher, especially as you likely will want DC out, and high frequency smoothing capacitors are going to be smaller than the capacitance for 400Hz smoothing, plus your magnetics will be a lot smaller with higher frequency, and DC supplies will have a lot less EMI and RFI problems. You do not really want to have every power cable be a shielded low loss dual coax cable, much better to have the cable shield provide RF reduction and distributed capacitance to attenuate RF noise.As to superconductors, the main issue is that half the time your cable will be exposed to really bright sunlight, and then rotate around to 3K space, so insulation will be needed, along with active control of cooling. The biggest issue in space craft in LEO and generally inside the orbit of Mars is dumping heat, they use reflective films a lot to control incoming heat and reflect it off, plus active cooling of some sort to control heating of internal parts, more than heating parts up to keep them stable.Only past the asteroid belt is the solar radiation going to be such that you will want to grab all incoming radiation and actively heat parts rather than keep them cooled, and there you will have massive solar panels to get power, simply because of the distance from the sun. in LEO you have 4kW or so per square meter of power being input, and either you reflect it, or your surfaces rapidly head towards a temperature where they radiate it off as IR radiation, which will be very close to the melting point of most metals used in spacecraft, and not exactly room temperature where most electronics is comfortable. Solar panels need cooling, though often that is simpler as you are pretty much always going to aim them normal to the sun, so the shadow side will run cooler and being thin they can easily transfer the incoming energy to dump as radiation to space, converting a tiny part to electricity as it occurs.

author: rdl
author_rank: Super Contributor
timestamp: September 16, 2017, 07:34:22 pm
content: Space is cold but it is a near perfect vacuum, so the problem is getting rid of any heat generated. The inside of the Shuttle's cargo bay doors were covered by heat radiator panels for this reason.

author: SeanB
author_rank: Super Contributor
timestamp: September 16, 2017, 07:45:22 pm
content: Quote from: rdl on September 16, 2017, 07:34:22 pmYes, the problem is dumping heat, you either radiate it away, moving it from the point of generation using either conduction or an active method like a pump, or use thermal pipes to move it with constant temperature drop. Another method is to use a phase change material to absorb it and then use idle time to dissipate it, by potting the assembly in a paraffin wax that absorbs energy to melt, and radiate it away later on when power demand is lower. Last resort is to use a throw away mass for cooling, letting the expansion of a liquid to the vapour phase absorb the heat, though that really is only used on rocket engines to keep them from melting, as otherwise you have a thrust vector you have to compensate for.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 16, 2017, 08:09:02 pm
content: I like the DC with the ultra high frequency conversion. My only concern with it is reliability and availability of spare parts.Is it easy to build and maintain a 1MW 100,000Volt (or similar) DC-DC switcher?

author: ejeffrey
author_rank: Super Contributor
timestamp: September 16, 2017, 08:14:43 pm
content: Quote from: woody on September 16, 2017, 07:09:13 pmThats not true at all. While space is "cold", the thermal conductivity of vacuum is zero. The only way to dissipate heat is radiation, which is extremely ineffective at much below "room" temperature. Your equipment will generate heat, and without active cooling will self heat above superconductivity temperature.Anyway, my vote is for AC. Switching AC-AC or AC-DC converters are not much more complicated or inefficient than DC-DC converters suitable for grid style use, and you get the arc suppression capabilities of AC and longer lifetimes for mechanical switches and relays. Just because AC means you can use magnetic transformers doesn't mean you have to. I imagine you would use HVDC for longer range distribution and convert to AC at the "neighborhood" level for distribution to actual outlets.

author: Zero999
author_rank: Super Contributor
timestamp: September 16, 2017, 08:17:16 pm
content: With modern technology, I think DC is the better option. DC-DC converters are smaller than even 400Hz transformers, there's no skin effect and there's less risk of electrocution, than with AC, at the same voltage. It's true that switches and circuit breakers are more challenging to produce for DC but they will need to be pressurised and oil filled, to avoid arcing anyway, if they're operated in a vacuum. RCD/GFCIs can also be made for DC, using a Hall effect current sensor, rather than a current sensing transformer. The question is what voltage to use?How about +/-50V? That should be compatible with most telecommunications equipment and the 0V conductor can be small, as the positive and negative currents will balance out, on average. It would also be good for running an audio amplifier off. I suppose the disadvantage is the 0V conductor is an extra point of failure and could cause a device to get 100V, under certain fault conditions, so that's probably a bad idea.I don't think voltages above 350VDC for local distribution, would be a good idea, because there's an increased risk of arcing and electrolytic capacitors and semiconductors get pricey, beyond that point. It would also mean that existing switched mode power supplies, designed for AC mains would be unusable. I know that using existing technology/devices isn't a requirement here, but it will make it cheaper, if the system is comparable with them.120VDC might be the best solution, because it will work with most universal switched mode power supplies and is already used in some industrial settings, so equipment should be easy to get hold of. It's also the upper end of SELV (Separated Extra Low Voltage) so fewer safety precautions need to be taken, than with 120VAC or higher DC voltages.Quote from: Assafl on September 16, 2017, 08:09:02 pmWhat do you mean by ultra high frequency? By standard, that's 300MHz to 3GHz and there are no efficient switched mode power supplies which work at such high frequencies. Current switched mode power supplies use 3MHz, at most.QuoteI don't know. I believe higher power converters use lower frequencies <30kHz, as the switching losses become greater. Higher frequencies are also incompatible with high currents, as the skin effect prevents thick conductors from being used.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 16, 2017, 08:22:00 pm
content: I would not use AC or DC. I would use HC.

author: Marco
author_rank: Super Contributor
timestamp: September 16, 2017, 08:32:15 pm
content: Quote from: ejeffrey on September 16, 2017, 08:14:43 pmWith AC you'll always be stuck with PFC and PFC will always need sufficient storage capacity to bridge the troughs. 3 phase helps a little, but doesn't eliminate the fact.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 16, 2017, 08:40:09 pm
content: Quote from: Hero999 on September 16, 2017, 08:17:16 pmThat's a part of it. The main one is, devices are slower. You are limited to high voltage IGBTs (>2kV, rise/fall time a couple microseconds), and SCRs and similar devices (for MVA size systems; even slower).As the linear dimension of a component increases, so does its propagation delay, and all properties proportional to that. This includes the bandwidth of transformers, and their low frequency equivalent parameters (leakage inductance and parasitic capacitance). Even ferrite cores can't get larger forever: skin effect eventually affects performance. (IIRC, the skin depth is on the order of 10cm for 100kHz, for typical MnZn ferrite. Normally, if you're building a transformer that big anyway, you build it from 2.5 x 10cm bricks, glued together, so you might not notice anyway.) Similarly for bypass caps, bus bars and so on.Also, since we're still talking thousands of amperes and thousands of volts, the switching impedance is on the order of single ohms, while the characteristic impedance of those components is much higher. The result: stray inductance dominates.It doesn't make sense to use really fast transistors with components that can't handle it, so there's no pressing need for speed in the biggest parts.Oh, and, lastly -- there's economy of scale, hence it's not worthwhile to keep stacking high frequency converters, but rather to use big components. But, if you do need high frequency operation (induction heating, radio transmitters, physics), that's the strategy you need to use.Tim

author: daqq
author_rank: Super Contributor
timestamp: September 16, 2017, 09:19:33 pm
content: QuoteYou are right, the specification was a bit vagueI was thinking along the lines of a Mars colony, not a colony on an asteroid or something with no atmosphere (although Mars does not exactly have a thick atmosphere...).As to the size, well, that's the reason for theTemporary solution now, permanent lateroption is available - initially, I'm thinking that a colony would be a few hundred people max. In the long run it would grow to several thousands, beyond that it's impossible to guess. Initially, the people would be experts, engineers etc, with very specific equipment and limitations that they would have to conform to. Later on the situation would change. 3. and 4. I do not know.The 48VDC or similar solution seems nice for being as safe as it gets voltage (and arcing), but it's not practical for higher power transfers.QuoteWe already do this - the only way to get any heat off our planet is by radiation to outer space. The atmosphere in our case is thick enough to allow effective coupling from our heat sources and provide an "averaging" of the temperature in the world. So, radiation is an effective option, provided we can make radiators.I don't think superconductors are an option :-)QuoteWhat's HC?QuoteIf you mean the 20kHz one, that one would be probably usable only very locally, say, present in the outlet, converted down from some DC or lower frequency grid. A larger grid at high frequency would suffer greatly due to capacitance/inductance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 16, 2017, 09:59:24 pm
content: FWIW, Mars is about the atmospheric pressure where breakdown voltage is irritatingly low. So you need a lot of insulation whatever you do.Are we talking components shipped in, or components made locally? Resources will be very thin until a manufacturing base is created. Likewise, once manufacturing is possible, the scale will probably be large enough to demand, not only higher voltages, but protection systems -- a scale where, even if everything is still centrally controlled, it must be very carefully fault tolerant. Real world examples are mining machines and naval vessels: manned by thousands, producing many megawatts, and typically using AC power (at 400Hz if they have the option).So there will be three distinct phases:1. Shipped in. Stupidly expensive. Priority: absolute minimum weight and size. Extremely high reliability.2. Early manufacture. Not necessarily primitive materials, but definitely simple materials. Capability, and probably reliability, will be poor. Protective elements may have to be shipped in, and probably converters as well. Designed either to: extend the existing infrastructure (e.g., expanding the network but keeping it 48VDC or what have you); or to implement an intermediate stage (higher voltage DC, say?) or something that can be quickly adapted to the future system.3. Late manufacture: self-sufficiency. Most or all components are produced locally, and the network meets its final standards. The network operates safely and reliably, at a modest failure rate, and a low emergency rate (i.e., nothing is burning to the ground).Heh, incidentally: since atmospheric pressure is low, and conductors may become exposed, and CO2 is a mild oxidizer to most things: it could very well be the case that you have a "plasma fire" in or around some of these outdoor conductors. Sorry, Star Trek, plasma conduits still aren't a thing though.Tim

author: cdev
author_rank: Super Contributor
timestamp: September 16, 2017, 10:21:53 pm
content: EMP from solar flares, might become problematic if you're out in space. For example, on planet Earth, which exists in space.lets not make the same mistakes twice.So my vote is DC, generated close to the point its used from solar cells - joule thief devices and localized DC-DC converters to change voltages.Otherwise, there is a risk whenever long wires are involved.A one in eight risk every decade (ESTIMATE) of a Carrington-class event.https://en.wikipedia.org/wiki/Solar_storm_of_1859http://science.nasa.gov/science-news/science-at-nasa/2010/16jul_ilws/http://news.bbc.co.uk/2/hi/programmes/newsnight/9020059.stmhttp://www.mne.psu.edu/Motta/News/NAS_Fukushima_2014.pdf

author: nctnico
author_rank: Super Contributor
timestamp: September 16, 2017, 10:30:54 pm
content: Quote from: IanB on September 16, 2017, 06:27:09 pmI agree. If it is just one tent then going for DC makes sense. When entering the 10's of kW territory I'd go for AC because it is easier to switch, easier to step-up/down and you can also use a lot of commercial off-the-shelve equipment. The days they made everything for use in space from scratch are long gone. Look at the number of laptops they have in the ISS.

author: BrianHG
author_rank: Super Contributor
timestamp: September 16, 2017, 10:34:08 pm
content: Do not start you colony until you have cheap superconductors...Run everything at a medium DC voltage like 120v.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 17, 2017, 12:06:34 am
content: Quote from: blueskull on September 16, 2017, 10:34:14 pmWas*Although to be fair, thereallybig stuff (many MVA) will be with us for a long time. Partly just because the power electronics industry is very slow moving.One thing that modest power, medium voltage converters have going for them: the impedance is modest. 100 ohms is a very favorable switching impedance, and it gets you 65A for a solid 1MVA capacity. Such things may be economical to stack in parallel because of materials reduction in the magnetics. Will be nice to see (just, it'll take a good 20 years before we see it adopted for any infrastructure).Tim

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 12:44:43 am
content: In 1859, a huge solar storm hit our planet and caused massive voltages to be induced in all conductors.http://articles.adsabs.harvard.edu//full/1859MNRAS..20...13C/0000013.000.htmlLuckily, this was before humanity depended on electricity to the degree we do today.If such a storm occurred today, itcould cause massive destruction of essential components of our power gridand quite possibly extended power outages, as many components of power systems had to be replaced.The accident at Fukushima suggested that if power was knocked out in a large area and it was unable to be brought back in a fairly short time frame, there would be an unknown but substantial risk of nuclear meltdowns due to a lack of ongoing cooling capacity for spent fuel at nuclear power plants (which must be continually kept cool by flowing water).A so called Carrington Class event could cause multiple nuclear meltdowns all at the same time. Would it? We don't know. We're trying to make nuclear power plants more impervious to this "loss of the ultimate heat sink" issue but the problem in some respects is inherent to the type of design we use more often than not so the best we can do is attempt to provide them withmultiple redundant sourcesof cooling water, because thats what they need. And try to give power generation and transmission facilities as much warning as possible when a solar event is detected. And hope for the best.Similar risks exist in space for similar reasons except outside of the Earth's magnetic field (this is why when you're in orbit,equatorial orbits are bestfor long term human habitation) there is even less protection.Here on the Earth, apart from secondary effects of loss of the power grid - possibly for years in some areas, and the possibility of loss of the ultimate heat sink for nuclear power plants,loss of electricity usually doesn't cause an immediate threat to lifein quite the same manner that it would in space because essential life support systems, carbon dioxide scrubbers, etc. all depend on electricity.So those systems have to be able to withstand the effects of solar storms, and in every possible way, be resilient and fail-safe.So, given the risk to everybody is arguably much greater if the system is lost, maybe the best solution is multiple different solutions in parallel?

author: EEVblog
author_rank: Unknown
timestamp: September 17, 2017, 12:55:27 am
content: The problem with DC is that it requires DC-DC converters which are complex electronics, and a space colony probably has limited complex electronics manufacturing capability.But given all the complex electronics that would be there anyway, I guess that's the least of their problems.Power sources like solar and maybe even nuclear TEG will all be DC, so DC makes sense.Unless you also have turbine based generators like hydro (unlikely of course!), wind, or gravity based drops trains or some such, those will be AC.But even then would still make sense to have a DC system in a small colony at least.

author: Ampera
author_rank: Super Contributor
timestamp: September 17, 2017, 01:55:35 am
content: I see a fundamental flaw in this thought experiment.What resources are available in this space station?Take for example Federation vessels/stations in Star Trek which transfer energy by conduits carrying superheated plasma to power various other systems besides the warp drive.I mean if we had all the resources to our hand to build the ultimate space station, we would (ideally) use some type of local power generation in small form, and allow the manual configuration of the power type for compatibility with various electronics (no power conversion needed afterwards). Something like a panel on the wall that would allow you to set the Mr. Fusion to output whatever power you needed to run what device you required.There will obviously be a need for a centralized power system for station functions, however, and the best idea I can think of would be a DC system, as even though it is more expensive to handle, the resources at hand for a space station would likely make that cost negligible, or perhaps it might not. Maybe when we develop space colonies we are using an alternate form of energy that can be transmitted more efficiently through other means, and then be directly converted to regular electricity at the tap, in which case the discussion is mute.

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 02:08:18 am
content: I suspect they would have some kind of small semiconductor fab and a recipe book.. DIY semiconductors.For power generation they will certainly use solar and possibly also use small scale nuclear energy.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 17, 2017, 02:22:20 am
content: One thing that may tip the balance to AC is reliability. When you are on the end of a space supply chain you really don't ever want to have to replace components. Transformers have lives measured in decades even when abused, while the capacitors in switch mode power control have lives measured in years. And while the colony may have its own manufacturing capability, it will be taxed to support all of the many requirements - from diapers to replacements for the sand blasted face plates for mars suits. Transformers are easier than capacitors.Of course this whole argument is moot when pocket fusion generators come on line. Which will probably be only a couple of decades after the big fusion generators come on line. Which they have been promising us since the 1950s.

author: CNe7532294
author_rank: Regular Contributor
timestamp: September 17, 2017, 02:28:51 am
content: Without reading here. DC for solar panels. AC but not 50 or 60 Hz. Airplanes and even boats use 400 Hz. The reason being is because of weight. Same factor to apply if you want to liftoff from a planet. The question is too broad. Need to specify where the said colony would be located. The colony could be a place with no sun but high in high energy resource (similar to oil or coal) or could be in space within view of the sun. Another factor I'm not sure is distance away from the sun. Say like Voyager 1 and 2. I voted temporary since I don't know where this colony would be or if it would be permanent.

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 02:40:18 am
content: The Moon, Mars, Earth orbit or one of the Lagrangian points?

author: BrianHG
author_rank: Super Contributor
timestamp: September 17, 2017, 03:03:07 am
content: How much power do we need?I can imagine most will be for mining equipment, second by atmosphere (includes heating/AC) processing and hydroponics, lastly cooking. Powering these items would be centralized around your generator. Everything else in the colony would be designed around absolute minimum power use possible. Don't believe that in a space colony, everyone will have apartments with fridges and stoves with running hot water. They will have minimal air, light and there will probably be centralized shared bathrooms. As for food and eating, there would be a single large cafeteria, too small for all the colonists to use at once, where all the food is prepared & the colonists cycle through on a schedule to serve everyone.We are not yet at any point close to dealing with luxuries in a space colony. Everything will be constructed on minimal energy wastage.Even if you have fusion, every drop of hydrogen fuel you waste might one day bite you in the ass if there is an emergency.

author: EEVblog
author_rank: Unknown
timestamp: September 17, 2017, 03:12:52 am
content: The TV series Terra Nova had a chip printer machine. It could just spit out new processors or whatever chip you wanted.

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 03:44:02 am
content: To get to other star systems that might offer some hope of having Earth-like planets we may use suspended animation.Which may be right around the corner.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4060059/

author: CopperCone
author_rank: Super Contributor
timestamp: September 17, 2017, 04:17:51 am
content: you probably don't want magnetic fields but you also really don't want electrocutions due to the fact that injury out there could seriously impact morale and operations.How about a higher voltage at a frequency that's difficult to kill with but also easier to shield? Last thing you want to do is take out a doctor or communications tech etc.its really not the place to be saving money. I shudder thinking about the cheap bullshit people will come up with however.Oh, the transient from that thing just happened to open an airlock. Also you don't want fires. High current = heated junctions = fires.

author: CopperCone
author_rank: Super Contributor
timestamp: September 17, 2017, 04:24:01 am
content: Quote from: BrianHG on September 17, 2017, 03:03:07 amhello space slum lordwill you have hoes, pimps and drug dealers at your fine ghetto? Do you work for Weyland Yutani perhaps?At least you can go outside in the somalian hood lolScary enough though, your probably right, when a medium small company establishes a mining operation on titan or something, its going to be exactly like this, probably get thrown out of the airlock if you complain.. or after your work contract is over (such a company does not like actually paying the employees).If you work for such a fine establishment, you should be thinking, i wonder what probability of destruction the return ship was set by the board of directors....I see serious fuckin problems colonizing something that does not have a atmosphere because of corporate human nature................ its like deciding one day, yea, ima go live the rest of my life on an oil rig??? I can't see something thats not a planet without atmosphere actual becoming anything more then some kind of workplace similar to an oil rig.

author: BrianHG
author_rank: Super Contributor
timestamp: September 17, 2017, 05:15:33 am
content: Quote from: CopperCone on September 17, 2017, 04:24:01 amYes, just keeping no longer functional people alive on a colony where you use power for every breath of air and food, ships used to return the mined goods would probably be outfitted to at least transport 1 or 2 humans in cryostasis which would be cheaper than keeping them on the colony till the end of their life.

author: BrianHG
author_rank: Super Contributor
timestamp: September 17, 2017, 05:27:57 am
content: Quote from: EEVblog on September 17, 2017, 03:12:52 amThat's ok for low power electronics and control electronic. As long as you chip printer doesn't die, and if you have many, can they be powered separately from everything else & create what you need before you die of suffocation.Ok, this is a silly point, obviously the technology will improve in speed and capability. But it will need to be able to create some serious IGBTs for power distribution circuits & heat sink mount them for that 1 critical solar flare storm which will knock out your primary parts and you are running on your backups just as the next surge may hit at any time.We'll get there... Just not in time for Musk's putting man on Mars for, what's his current planned ETA, 2024? I doubt the current machine would survive the rocket launch and mars landing.

author: Someone
author_rank: Super Contributor
timestamp: September 17, 2017, 05:34:47 am
content: Quote from: CatalinaWOW on September 17, 2017, 02:22:20 amAlso DC systems have corrosion problems, and in a large probably mostly conductive object you would want to have lots of galvanic isolation available and rigorously eliminate any currents flowing through the structure. AC at a high frequency is a good contender for the hypothetical problem and with modern core materials you can build low loss transformers that weren't possible when the electrical standards were forming. Cabling could be a creative application specific design such as a flexible hose with conductors spiralling slowly around the inside surface to minimise losses, and doubling as a dry gas transport/storage system.

author: tom66
author_rank: Super Contributor
timestamp: September 17, 2017, 07:49:18 am
content: Use DC. It's more efficient and less weight required for transformers, which would have to be taken by rocket. .For distribution, 1600V or 2500V. It's within the rating of high-performance IGBT modules so can be DC-DC converted easily. Cables rated at 100A or so would be sufficient for most demands (100's of kW).Local distribution, 28V DC or 110V AC 400Hz for compatibility with existing milspec equipment. 42V DC as a possibility for some higher power equipment.

author: BrianHG
author_rank: Super Contributor
timestamp: September 17, 2017, 09:27:02 am
content: Quote from: tom66 on September 17, 2017, 07:49:18 amAt this point, you might as well use 48vdc, being compatible with a lot of telecom DC-DC converters and battery backup units where power redundancy is crucial.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 17, 2017, 09:45:00 am
content: Quote from: Assafl on September 16, 2017, 06:18:04 pmThis ^^^Interesting and challenging subject, except the most important specifications were left undefined.

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 03:05:44 pm
content: Al Globus, who has been writing and speaking about the practical aspects of living in space for a long time, has alarge body of stuff on space settlementon his web page. very much worth checking out as he's really put a lot of thought into it.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 17, 2017, 04:59:16 pm
content: Quote from: cdev on September 17, 2017, 03:05:44 pmLots of really interesting stuff, but I didn't see anything on the topic of this thread or any of the other nitty gritty issues of colonization. Provides a number of options for the colony architecture (size, location, general configuration) which at least answers some of the environment questions. That is fine because there is no question that there are a number of workable solutions to the power distribution problem. As with other fields it will be actual operations that finally determine the best (or at least near best) solution. There are bound to be problems that crop up that we don't currently envision that will modify the final answer. And the arguments will likely continue about what is the best solution long after the original colonies are abandoned or completely built over. Just as there are continued arguments about voltage and frequency in the terrestrial distribution systems.

author: donmr
author_rank: Regular Contributor
timestamp: September 17, 2017, 05:30:03 pm
content: First a totally new grid needs a very different approach than today's terrestrial grids.Our current grids are based on a design that began as a single generator sending power to some users.The power injected into the grid had to closely match the power removed at all times.When more generators were added they had to synchronize themselves. The complexities of managing generator output have caused or amplified many of our famous large outages.A "modern" grid needs very different behavior. Power production and use will both be widely distributed in distance and time. It should be possible for each node (generation and use) to be somewhat adaptable in a short amount of time. Both should have enough storage to last while they change their power production or use.Some method is needed to communicate the overall availability of and need for power. It seems to me that a DC system where the voltage is allowed to vary over some range is very good for this. Both ends can adjust the current they pass to keep the voltage within the specified range. The whole problem of synchronizing to an AC voltage is avoided.How do you start up an AC system in isolation? How do you then connect 2 such systems. What if the connections come and go between several sub-system?

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 05:45:04 pm
content: A lot of the design decisions likely revolve around energy storage as much as generation. We will almost certainly have far better (batteries or whatever) ways of storing generated energy than we do today by the time we are building a space colony.It makes sense to pretend we do, define them and then hypothesize how best to deploy them using simulation.-----Also, propulsion -exhaust velocity(and mass) determine how fast a space vehicle can be accelerated.We likely will need electricityfor propulsionthrough long distances in space. (Link is about ion propulsion)See chart athttps://en.wikipedia.org/wiki/Spacecraft_propulsion#Table_of_methods

author: BBBbbb
author_rank: Unknown
timestamp: September 17, 2017, 05:49:35 pm
content: Some nice thoughts that could apply to a colony idea were mentioned in a recent Amp hour episode regarding huge server rooms:https://theamphour.com/357-an-interview-with-rick-altherr/

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 17, 2017, 06:06:45 pm
content: Quote from: donmr on September 17, 2017, 05:30:03 pmWhy?Today's grids are a solved problem. They work! Your post is mostly hypothetical, while practical counter-examples surround us. So, er...Your mention of large outages remains a good point, though. Avoiding systems collapse type situations would be very important, especially when electrical power may be the only means of providing life support in an inhospitable environment.There could be a few methods to deal with this. Centralized control, redundant grids, local/distributed backup systems, etc.For example, it seems likely that solar power would be the dominant source; batteries are needed to maintain power through the night. If it is mandated that all loads must be self sufficient for at least a day, then the grid would have distributed backup in it. If the grid collapses, loads simply disconnect, making it trivial for the grid to restart without having to move huge loads in the process.It's quite possible that nuclear (fission or fusion) could be a suitable base load. Moreso than here on Earth. With practicalities winning over politics, and an entire planet available to pollute (not to suggest it should be done irresponsibly -- but needless to say, selection of a waste storage site will be far easier!), it could be a big winner.Tim

author: tszaboo
author_rank: Super Contributor
timestamp: September 17, 2017, 07:13:54 pm
content: I'm gonna go with 100Khz-1Mhz RF. It is AC, so no problems with DC stuff. You can use steel for the cabling, not copper, which makes it easier to mine (on mars). Distribution box needs to be smart. But that is actually a benefit, you just moved all the bulky electronics from the device to the wall. Ripple current is smaller. Making a ceramic capacitor, a bumch of coils, and a diode is a lot simpler than FETs and controllers for them. And RF does not kill you (might burn you though).

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 07:27:55 pm
content: When you're outside of the Earth's magnetic field, the effects of space weather are substantially higher than they are here on earth.There is a very substantial shortcoming to our current grid system and thats it has a vulnerability to damage caused by huge currents induced by solar storms. A huge solar storm equivalent to or greater than the one which occurred in 1859, (a "Carrington class" event" its called) would likely cause a huge amount of damage to the terrestrial grid, possibly knocking large parts - We dont know how much of a storm the Sun is capable of- just what we have seen happen with evolving science and what happened in 1859, which was before we had most of the technology we have today. Had it happened now, it likely would have destroyed a good chunk of the technology we count on for our day to day lives, in large areas, for quite a long time.(Source:https://science.nasa.gov/science-news/science-at-nasa/2008/06may_carringtonflare/)A huge CME would knock out the power grid, to an unknown degree- but its likely that in an event of 1859's magnitude, likely a lot of it would fail."The Earth would be picking up the pieces for a long time".Potentially a very great many transformers - if not taken off line before it hit, would arc over and parts of them would melt or explode.Much of the solid state electronics in critical infrastructure all around the globe would be damaged from something quite similar to ESD, something we understand - but much more of it!(Its much like the EMP caused by nuclear explosions. In fact, it is quite similar in its origin, coming as it does from the Sun.)Knocking out (how much?) The papers whose covers I put images of below attempt to estimate.If there was no warning (less likely all the time) perhaps all of the Earth's distributed power nets might be knocked "off the grid" unless they had been protected in some way- Typically, transformers bear the brunt of it and fail.. large and expensive transformers.. Even these custom built expensive pieces of equipment could be replaced, if the damage was limited to a few of them, but it could occur to thousands of them all around the globe, if there was not enough warning or the warnings were not heeded..Obviously, essential human activities like for example, the pumping and purification of drinking water, the lighting of buildings, increasingly, transportation, also perhaps most importantly, the cooling of spent fuel tanks in nuclear power facilities. There is a fear that were power backup not available when the grid was taken down that power to cool power plants might cease and a situation called"loss of the ultimate heat sink"might occur in multiple locations around the globe, which progresses if not addressed into a problem of water not being there when its needed, or boiling away, not being replaced and then a potential nuclear meltdown.Thats what happened at Fukushima. the problem is inherent to the kind of nuclear power reactors in use in most of the worlds nuclear power plants now.We're unlikely to use water in reactors in space thankfully, but grids off of planet earth are susceptible to the same problems, if hit by a CME. A planet's magnetic field greatly reduces the strength of the induced energy so where the magnetic field is less powerful then there is more problem.To a large extent, if we have a few years before the event occurs (we have absolutely no way of knowing) assuming we started a worldwide effort to make our power generation systems resilient today, this is a solvable problem here on Earth. that is to sayIF we face it rationally.A few years ago, I thought it was starting to happen but as its only come to the attention of policy makers in the last decade or so and they have been slow to react to it, and as it seems other problems are not getting the attention THEY needIn the interest of not discussing "politics" I'll leave it at this. We could go a great way towards reducing the risks but nature and people are unpredictable.Remember, multiple systems will be failing. Solid state electronics maybe failing everywhere. Hardware is not designed for this situation currently.So, efforts are being made to provide both a warning to power generators (so that the grid could literally be taken off line before the electromagnetic pulse reaches us, we might have only a very short warning)They need multiple backup systems for cooling that are prepared to run for extended periods of time in the context of a global disruption of virtually everything civilization normally provides. Even if they are provided with years of diesel fuel and redundant solar power farms and everything else, in the likely chaos following such an event, rational thinking might be in short supply.The key fact to take away is, our current technology has this big big problem. A huge solar storm could - with only minutes of warning, could knock out the entire global grid. causing a huge setback for civilization that could be multiplied greatly - if we dont provide redundant power that successfully keeps spent fuel cool, by additional nuclear catastrophes that would become economically almost impossible to fix. They could render areas uninhabitable.We need to step up to the challenge, because we cant afford to 'cross that bridge when we get to it' in this case..Imagine this problem occurring in space?How likely all this would be depends on something we don't know, what is the largest solar storm thats possible, and how often do they occur. We can only guess.This is why I cringe when I hear the word "grid".So, lets not make similar mistakes when we can plan from the beginning not to. What happens to the space colony's grid when the inevitable CME hits?Luckily, a CME seems to be directional, a space colony might escape a CME that hit the Earth. thats a compelling reason for building more space colonies.Quote from: T3sl4co1l onTodayat 12:06:45>Quote from: donmr onTodayat 11:30:03Why?Today's grids are a solved problem. They work! Your post is mostly hypothetical, while practical counter-examples surround us. So, er...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 17, 2017, 07:57:14 pm
content: Quote from: NANDBlog on September 17, 2017, 07:13:54 pmErr...QuoteErrrrrr...Tim

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 08:02:09 pm
content: There is a very very very wide variation in how much energy people use around the globe..People can live a full lifestyle and use a tiny fraction of what most of us use today. More than any of us have ever had to deal with, energy conservation will likely be extremely important in space.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 17, 2017, 08:34:16 pm
content: Quote from: cdev on September 17, 2017, 07:27:55 pmDo you know the operational mechanism of that failure?Is it just, a huge input of energy to the system, and it goes boom?Or is it something specific, to which transformers are susceptible, and which a quirk of our wiring methods exacerbates?There's also a very interesting difference between Earth and Mars (or the Moon, or what have you). Earth has a magnetic field, so all that solar radiation gets funneled around. Moving charge is current, current makes magnetic field.What's happening is, the field from all that current is inducing EMF in the power transmission system. The dB/dt is very small. It changes slowly over time, practically DC. The loop area must be extremely large to get anything of consequence.So what loop areas are affected? The loop between hot and earth. Not between hot and hot, or hot and neutral. It's common mode interference!The problem is, since transformers are grounded everywhere, there's a common mode current return path through the Earth. This is what damages infrastructure.No magnetic field? No problem!Well, almost. Maybe. CMEs have some magnetic field of their own. I don't know how much. It must be less than Earth's magnetic field (otherwise it wouldn't be pushed aside by the Earth, it would reach right down and touch the surface).Mars, not having a magnetic field, does not move solar currents, and so the risk is considerably less. Add to this a slight change in wiring design, and it would take a truly freakish event (like the Sun going into red giant phase??) to cause problems.And anyway, will grounding on Mars even work? Is the planet's surface conductive enough for that to be meaningful? (A quick look suggests it might, actually.https://earth-planets-space.springeropen.com/articles/10.1186/1880-5981-66-85On the other hand, a grounding rod might have to be driven quite deeply to get there. They were much more pessimistic in Viking times:http://onlinelibrary.wiley.com/doi/10.1029/GL001i003p00141/abstractNow that the soil is known to contain quite a bit of adsorbed moisture and perchlorates, it may well be quite reasonably conductive, after all!)What's great about all this is, academics have been curious about these questions, for decades, and have sent probes and instruments to help figure them out! All that research is just looking to be found. No need to speculate about it!QuoteWho's launching nukes at Mars?Nuclear EMP is similar to ESD, just stronger over a wider area. There's a fast pulse (some nanoseconds), a slower tail (microseconds), and slow plasma / planetary magnetic field interaction (milliseconds to seconds).Solar activity of course only has the latter. It's rather blobby plasma, diffuse, not an explosion.I don't think there should actually be much need of transient protection in space; cosmic rays manifest as random charges and increased leakage current, but not ESD (at least until something sparks). There's no terrestrial lightning on Mars.I think hazards would largely resemble automotive EMC standards: short transients due to switching and sparking, larger surges due to load switching and faulting.To get the reliability needed, it would still be quite desirable to use large TVSs or MOVs on power input connections, maybe to use isolation frequently as well (another point in favor of AC). There is precedent for this on Earth: undersea telecom cables are studded with booster amplifiers, supplied through a high voltage at either end of the cable. Each amplifier runs from the same current, dropping what voltage it needs. If a discharge event occurs, powerful and rapid transients are transmitted along the cable, at least for several amplifiers' distance. They used GDTs to absorb these, preventing damage to the precision vacuum tubes inside (referring to the earliest transatlantic cables, specifically, which were tube based).Tim

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 09:08:20 pm
content: There is lots more research going on on this. A lot of very smart people are thinking deeply about this problem. There has been a lot of research on how we might cope with it, most of it is not very accessible to non-scientists in terms of understandability but it is understandable by engineers. The conductivity of the earth is critically important to resistance to solar storm damage. Areas where there are so called igneous rock formations - where the underlying earth is not so conductive, are particularly prone to problems. (I live in an area with this problem)During the Carrington event innumerable newspaper accounts described auroral displays stretching way down to the tropics that lighted up the predawn hours so brightly people could read by the light. Basically the entire sky turned into a light display all around the world.Telegraph wires (the only long distance conductors at the time) were arcing, so much that the sparks started fires in telegraph offices. The telegraphs sounders went berserk even after being disconnected from any batteries.What happens - technically, and how can it be addressed/prevented better?There has been a lot of research on this issue - its definitely being done. Its not so hard to find.Specifically on power systems as might be found in space, not on Earth, and what might be postulated would happen to them, that is I suspect a narrower body of work but I would be surprised if nobody had not attempted to answer the questions, so I think searching will find more.lets see what we can find!Quote from: T3sl4co1l onTodayat 14:34:16>Quote from: cdev onTodayat 13:27:55Do you know the operational mechanism of that failure?Is it just, a huge input of energy to the system, and it goes boom?Or is it something specific, to which transformers are susceptible, and which a quirk of our wiring methods exacerbates?There's also a very interesting difference between Earth and Mars (or the Moon, or what have you). Earth has a magnetic field, so all that solar radiation gets funneled around. Moving charge is current, current makes magnetic field.What's happening is, the field from all that current is inducing EMF in the power transmission system. The dB/dt is very small. It changes slowly over time, practically DC. The loop area must be extremely large to get anything of consequence.So what loop areas are affected? The loop between hot and earth. Not between hot and hot, or hot and neutral. It's common mode interference!The problem is, since transformers are grounded everywhere, there's a common mode current return path through the Earth. This is what damages infrastructure.No magnetic field? No problem!Well, almost. Maybe. CMEs have some magnetic field of their own. I don't know how much. It must be less than Earth's magnetic field (otherwise it wouldn't be pushed aside by the Earth, it would reach right down and touch the surface).Mars, not having a magnetic field, does not move solar currents, and so the risk is considerably less. Add to this a slight change in wiring design, and it would take a truly freakish event (like the Sun going into red giant phase??) to cause problems.And anyway, will grounding on Mars even work? Is the planet's surface conductive enough for that to be meaningful? (A quick look suggests it might, actually.https://earth-planets-space.springeropen.com/articles/10.1186/1880-5981-66-85On the other hand, a grounding rod might have to be driven quite deeply to get there. They were much more pessimistic in Viking times:http://onlinelibrary.wiley.com/doi/10.1029/GL001i003p00141/abstractNow that the soil is known to contain quite a bit of adsorbed moisture and perchlorates, it may well be quite reasonably conductive, after all!)What's great about all this is, academics have been curious about these questions, for decades, and have sent probes and instruments to help figure them out! All that research is just looking to be found. No need to speculate about it!QuoteWho's launching nukes at Mars?Nuclear EMP is similar to ESD, just stronger over a wider area. There's a fast pulse (some nanoseconds), a slower tail (microseconds), and slow plasma / planetary magnetic field interaction (milliseconds to seconds).Solar activity of course only has the latter. It's rather blobby plasma, diffuse, not an explosion.I don't think there should actually be much need of transient protection in space; cosmic rays manifest as random charges and increased leakage current, but not ESD (at least until something sparks). There's no terrestrial lightning on Mars.I think hazards would largely resemble automotive EMC standards: short transients due to switching and sparking, larger surges due to load switching and faulting.To get the reliability needed, it would still be quite desirable to use large TVSs or MOVs on power input connections, maybe to use isolation frequently as well (another point in favor of AC). There is precedent for this on Earth: undersea telecom cables are studded with booster amplifiers, supplied through a high voltage at either end of the cable. Each amplifier runs from the same current, dropping what voltage it needs. If a discharge event occurs, powerful and rapid transients are transmitted along the cable, at least for several amplifiers' distance. They used GDTs to absorb these, preventing damage to the precision vacuum tubes inside (referring to the earliest transatlantic cables, specifically, which were tube based).Tim

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 17, 2017, 09:23:51 pm
content: While energy conservation will be real and mandatory, energy consumption will be more like earths first world than like those in the third world who use little or no energy.Things like fans to move the air around are not optional.

author: cdev
author_rank: Super Contributor
timestamp: September 17, 2017, 09:25:20 pm
content: We're in luck, there is a substantial amount of stuff onNTRSabout CMEs generally and the ways they cause disruption in particular.I just downloaded a sampling of it. Just go to NTRS and enter in search terms like CME and Carrington and you'll find a lot of stuff.What would be good search terms for the effects of CMEs outside of Earth's magnetosphere?In space, On spacecraft, the lack of large conductors might mean its less of a problem?One thing, here on the Earth, good ground conductivity,does good grounding reducethe risk?----------------------------------------------------------------Here are several useful looking ones.. There are lots more on NTRS."Sun-Earth Connections: How the Sun Knocks Out My Cell Phone from 150 Million Kilometers Away--------------------------------Integrated Science Investigation of the Sun (ISIS): Design of the Energetic Particle InvestigationNTRS Full-Text:Click to View[PDF Size: 14.6 MB] (Use this link)------------------------------------------------------http://hdl.handle.net/2060/20150023298Radiation Engineering for DesignersNTRS Full-Text:Click to View[PDF Size: 5.10 MB]External Online Source:https://nen.nasa.gov/Author and Affiliation:Pellish, Jonathan A.(NASA Goddard Space Flight Center, Greenbelt, MD United States)Abstract:This tutorial provides an overview of the natural space radiation environment, an introduction to radiation effect types, an overview of EEE parts selection, scrubbing, and radiation mitigation, and an introduction to radiation testing.Publication Date:Nov 30, 2015Document ID:20150023298 (Acquired Jan 04, 2016)Subject Category:SPACE RADIATION; ELECTRONICS AND ELECTRICAL ENGINEERINGReport/Patent Number:GSFC-E-DAA-TN27833Document Type:Oral/Visual PresentationFinancial Sponsor:NASA Goddard Space Flight Center; Greenbelt, MD United StatesOrganization Source:NASA Goddard Space Flight Center; Greenbelt, MD United StatesDescription:131p; In EnglishDistribution Limits:Unclassified; Publicly available; UnlimitedRights:No CopyrightNASA Terms:AEROSPACE ENVIRONMENTS; EXTRATERRESTRIAL RADIATION; RADIATION EFFECTS; RADIATION HARDENING; TRAPPED PARTICLES; RADIATION DOSAGE; SINGLE EVENT UPSETS; RELIABILITY ENGINEERING; RISK ASSESSMENT; SOLAR ACTIVITY EFFECTS; GALACTIC COSMIC RAYS; COSMIC X RAYS; GAMMA RAYS; DESIGN ANALYSIS; FAILURE ANALYSIS; AEROSPACE ENGINEERING; EDUCATION; NASA PROGRAMSOther Descriptors:RADIATION EFFECTS; NATURAL SPACE RADIATION ENVIRONMENT; RADIATION MITIGATIONMiscellaneous Notes:For release on the NASA Engineering Network website

author: tszaboo
author_rank: Super Contributor
timestamp: September 17, 2017, 10:14:05 pm
content: Quote from: T3sl4co1l on September 17, 2017, 07:57:14 pmWell, I mean this:It has less drawback than copper, right? And the length of the cables are in tens of meters, not hundreds of kilometers. Steel cables for a planet like mars makes much more sense. Plus as I said, transformers are small, and no complicated silicon.And sure, there are several ways to die with electronics. But pulmonary failure because your hearth follows the phase at 1MHz is not one of them.Also, I like actual discussion better than "hurr durr you dumb".

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 18, 2017, 03:38:50 am
content: Quote from: NANDBlog on September 17, 2017, 10:14:05 pmYou know what skin depth is based on, right?Skin depth is less when the resistivity is smaller (good) and the permeability is higher (not good).Iron is doubly bad for precisely this reason.If nothing else: even if mu = 1 (which occurs at >1MHz range, for most alloys), the resistivity is simply ~5 times higher. The resistivity does not, and cannot, get any better at lower frequencies.QuoteI'm not sure how to read this... (translation error?)QuoteMaybe it's not your direct fault, but in that case, whoever it was that told you skin effect corresponds to efficiency, is at a "not even wrong" level of wrong. It's hard to guess where to begin a discussion, where assertions like that are found.Tim

author: cdev
author_rank: Super Contributor
timestamp: September 18, 2017, 04:03:32 am
content: Yes, whenever astronauts are doing videos from ISS you can always hear the CO2 scrubbing/ventilation equipment going, its a constant presence.Quote from: CatalinaWOW onTodayat 15:23:51

author: tszaboo
author_rank: Super Contributor
timestamp: September 18, 2017, 08:43:07 am
content: Quote from: T3sl4co1l on September 18, 2017, 03:38:50 amResistivity is irrelevant. Somewhat irrelevant. What you need to have on a planet far away:Easy to get resource for the "low tech parts", like a cable, which can be manufactured on site. It does not matter if copper is better, because you cannot mine copper on mars, while all the rocks contain iron. So steel cables.Small size and weight for the high tech parts, like electronics, which is shipped in. If your frequency is higher, electronics is smaller. At 1 MHz, a transformer is fraction of the size, and does not require complicated electronics to make any voltage DC from it.Quote from: T3sl4co1l on September 18, 2017, 03:38:50 amOf course it is, I ment to write fibrillation (shouldn't write forum posts at 1AM). You never get that with high frequency.Quote from: T3sl4co1l on September 18, 2017, 03:38:50 amI dont know, where you got that. High frequency transmission is wrong for efficiency. Skin depth makes it even worse. It is just less worse for the steel cables, than copper cables.And for once, I dont think that efficiency of the power transmission is going to be an issue. Everyone imagines, that a Mars base is going to be with a bunch of solar panels and windmills. No, I dont think so. It is going to be a nuclear reactor, capable to work on peak efficiency for at least 30 years.Just imagine, you need a lot lot more energy to keep people alive there. CO2 scrubbers, heaters, farming, 100% water recycling, probably a supercomputer, antenna array, all these will take a lot of power. And power keeps you alive.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 18, 2017, 02:28:47 pm
content: Quote from: NANDBlog on September 18, 2017, 08:43:07 amOh, your argument has also incorporated assumptions about availability? That helps explain things, I guess.But again, why make assumptions when you can look things up?https://upload.wikimedia.org/wikipedia/commons/2/21/PIA16572-MarsCuriosityRover-RoverSoils-20121203.jpgMartian soil is richest in aluminum; iron is actually quite a small part of it! It just looks like a lot because Fe2O3 has such a strong color.Magnesium is also well represented, not that lightweight structures are exactly needed over there.Nickel being so highly represented is strange; that's a fantastically good ore body, here on Earth! It wouldn't take much processing to obtain that (e.g., soak soil in acid; electrowin nickel and other noble and near-noble metals; neutralize tailings and deposit back on surface).The abundance of lime and silica is also good news for making concrete.But even better:https://en.wikipedia.org/wiki/Ore_resources_on_MarsBased on what we already know about Martian geology (vulcanology?), there is absolutely, positively no reason to doubt that differentiated ore bodies exist: there should be everything from basalt lava flows to pegmatite intrusions. We know Mars had lots of water in the distant past, too, so it's reasonable to assume we will find hydrothermal deposits, ranging from beautiful quartz geodes and agates, to sulfide ores and native metals (copper, silver, gold, platinum, etc.).It'll all be there for the taking, it's just a matter of doing geological studies: seismic profiles, drill cores, magnetic and gravitational anomalies (of which we already have a good map, just a, shall we say, high level overview -- low resolution, as it was collected from orbit:http://all-geo.org/highlyallochthonous/wp-content/uploads/2010/07/marsglobalmagl.jpgmagnitude,http://all-geo.org/highlyallochthonous/wp-content/uploads/2010/07/marsglobalmagl.jpgradial component;https://www.nasa.gov/sites/default/files/thumbnails/image/mars_grav_tharsis.jpggravitational), all the cool stuff we've done here on Earth while looking for things!They're already gearing up for the next round of Martian probes, that will include deep drilling capability. I'm hyped!Anyway, as for ferrous coax: to use a very basic example, RG-58 is already about -1dB per 100 meters at 1MHz. That's pretty crap efficiency, and about as far as you'd want to go with the stuff. If you need to go farther, you really should just put a generating station closer by. It's like Edison's low voltage DC, but worse. Make it out of iron instead, and you're talking -1dB per 20 meters, or less. You might as well walk a battery pack back and forth, it'll be more conductive!Yes, coax can be made with larger conductors for greater efficiency, but now you're talking ever greater amounts of material. Say, 10cm+ dia. pipes, plus all the insulation. Insulation is required. Either you fill it with a hard vacuum (which is not a bad idea, I'll admit) or high pressure CO2, in which case the assembly has to be air-tight, making connectors difficult; or it's some sort of solid insulation you've managed to cook up. A solid insulator must fill the entire space, because voids at atmospheric pressure will be ionized constantly.(Oh and, there are plenty of lower loss cables, like 300 ohm pair. That helps, but it makes the voltage even higher still.)The low atmospheric pressure also makes open-air wiring rather inconvenient. I think they'd be using cable all the time, which is another point in favor of lower frequency AC.QuoteThis is nearly true --The transformers and filters can be quite small, but at a distance of more than a few meters, at that frequency, you must observe impedance matching.That means either: you have a nominal amount of power available and you simply use whatever you need (the rest is reflected back to the source, which deals with it somehow; your DC load voltage varies from 50-100% and you just have to deal with that), or the load expects a certain power demand, and it must communicate this to the source, so it can deliver the desired amount of power (in which case, you have tons of smarts on both ends, which kind of defeats the purpose).The nice thing about low frequencies is, you don't have to worry about transmission line effects except for extremely long (100s km) links. And even then, they aren't fractional wavelength, you just need a few reactors or capacitors, and tap changers, to deal with it.QuoteNo one mentioned windmills before now, IIRC. That would be silly. Solar is the most readily available. It will be a long time before NASA constructs a fission reactor they're sufficiently confident about to launch into space (let alone convincing everyone else that it's the right thing to send up on a huge stack of controlled explosives -- a rocket), and which is usefully powerful for a colony. Of course, it will be a long time before we have colonies needing megawatts, so perhaps that will work out nicely in the end!https://en.wikipedia.org/wiki/Nuclear_power_in_space#Fission_systemsTim

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 18, 2017, 04:30:06 pm
content: Quote from: T3sl4co1l on September 18, 2017, 02:28:47 pmActually, NASA has already sent one into space (SNAP-10A) and the soviets sent quite a few (at least a dozen). Convincing everyone it is safe (enough) is a problem continually getting more difficult, and has moved from the solved to the unsolved category. The reasons for that change are partly emotional and could change over time. There is also the possibility that boosters will get more reliable. Back when SNAP was launched they really thought that they might be approaching multiple nines reliability. Now we know the real number is 98-99%, but there is no fundamental reason that cannot improve.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 18, 2017, 04:54:47 pm
content: Quote from: CatalinaWOW on September 18, 2017, 04:30:06 pmYeah, and those examples were in the link; that's why I added "which is usefully powerful for a colony", i.e., megawatts at least. AFAIK, reactors like SNAP were relative toys: for sure, hundreds of kW of thermoelectric power is itself nothing to bat an eye at, but scaling that up for whole cities would demand a proper heat engine, like the usual terrestrial power plant uses.And who knows, maybe molten salt reactors will get more consideration, when such a time as this becomes important. They were originally being considered by the Air Force for their light weight potential!Launch reliability, as a factor in what kind of cargo is acceptable for launch, is an interesting facet. That, along with cost effectiveness, might be a big driver in the future of electromagnetic launch systems.Tim

author: cdev
author_rank: Super Contributor
timestamp: September 18, 2017, 08:49:27 pm
content: You wont find me voting for any new fission anything. Fusion however I think has a very bright future.

author: cdev
author_rank: Super Contributor
timestamp: September 18, 2017, 09:09:07 pm
content: Space elevator made of carbon nanotube fibers is an interesting concept.If it could be accomplished, once online it would reduce the cost to put any given mass of payload into space by several orders of magnitude.Really, the likely weight of any interstellar expedition (i.e. finding new Earths to colonize) would require a space elevator or something like it to be possible.Right now, even if Mars was made out of solid gold or really almost anything, (Even the mythical "unobtainium") the costs of sending any mission to Mars to get it and then bring it back render the proposition economically pointless if viewed strictly financially. I think that viewed in the larger context it is worthwhile, but I think taht even under the most favorable conditions (lots of interesting science to do) the fact that it and all other places we know of in space are and likely would remain inhospitable enough to make it very costly to even just be there, makes it likely that few would could choose to live there permanently.A space elevator would change all that if it could be built.Which is a big "if".But if ...Suddenly we could become a spacefaring planet.

author: tszaboo
author_rank: Super Contributor
timestamp: September 18, 2017, 10:53:26 pm
content: Going to space isnt expensive. NASA budget: 18 billion, USA millitary budget: 598 billion, Spacex budget: about 2-300 million. Just place your priorities elsewhere, and suddenly we could have 60 space station, launches every day with a fleet of spacecrafts. It is just steel, a lot of water and some engineering. And engineering is the expensive part. If the production numbers go up, there is nothing expensive about it. Of course, if you ignore the Nasa way, were a single bolt costs 1000 USD, but there are so many layers, that nobody can actually find the real cost of things.

author: m98
author_rank: Frequent Contributor
timestamp: September 18, 2017, 11:05:01 pm
content: I think the power grid of such mars colonies would mostly consist of island systems so the power distribution will be mostly internal to the spacecraft the structure consists of. The standards will, therefore, be dictated by the different interfacing spacecraft. Because systems like the SpaceX Dragon or Orion all use an unregulated 28 VDC bus and still have to be compatible with the unregulated 120 VDC bus of the ISS, the systems on a Mars colony will probably use a compromise of those. Higher voltage is obviously beneficial for the efficiency of large solar arrays as they would be used on the surface of Mars. So power generation and storage will be unregulated at Vmpp with a regulator providing steady 120 VDC to a secondary bus.Just as on the ISS, there will be an outlet system like the Utility Outlet Port using mil-spec round connectors for portable equipment and suitable racks providing connections for stationary equipment.

author: BrianHG
author_rank: Super Contributor
timestamp: September 18, 2017, 11:47:54 pm
content: Quote from: cdev on September 18, 2017, 09:09:07 pmOn orbital ring would be far superior to a space elevator. It releases you from the need for rocket fuel to get to mars and it requires far less tensile strength than nano-tube, though carbon nano materials like graphene and nano-tubes would still help...See here: Arthur makes a dead obvious clear cut case to forget about wasting time on a cheap space elevators and go straight to orbital ring if you want to get to other planets with any heavy duty hardware and vehicles.

author: Old Don
author_rank: Regular Contributor
timestamp: September 22, 2017, 01:01:01 pm
content: A space colony more or less exists on earth now, in fact several of them. Antarctica is a good example of what is needed on a distant planet and the solutions will be what's worked , and hasn't worked, for there.The space colony will expand slowly at first and a local solution for each building/housing unit would be best for redundancy in case of failures. As one gets further away from a solar source solar cells work at lower and lower efficiency and nuclear becomes a good short time solution. Heat generated doesn't have to be dissipated into space since the planet or object can be used to absorb the heat if it isn't trapped and used to heat the colony. I think as the colony expands that fiber optics would connect new sub-colonies and more local generation of power could continue to make sense. Depending upon local conditions, going subterranean would make sense to isolate the colony from surface conditions. The reason for the colony, in the first place, would most likely be for mining or the cost to support the colony from earth won't make any sense. So mining equipment will be there and can be used to construct living chambers out of old mining tunnels. Mining itself will need lots of power and return trip rockets would return the mined materials to earth after delivering new or spare parts and people to the colony. Finding a local source of nuclear fuel would also make sense in the long run.

author: cdev
author_rank: Super Contributor
timestamp: September 22, 2017, 05:59:48 pm
content: I totally agree with you that going into space should not be seen as prohibitively expensive.I wanted to say that I don't think NASA is at all expensive as government spending goes, considering what it returns in knowledge, I think its a bargain.So much technology is developed at NASA, the mind just boggles. We should realize a good thing there and not let politics and ideology get in the way of common sense. What I mean is that privatizing, ironically, often increases costs a great deal. Which may often be its intent, in a sort of covert-aggressive way.Once something is privatized, more and more things are made almost impossible to de-privatize by foreign involvement and all sorts of treaties. It can become a burden - because a veto on laws (which they call "transparency") becomes a form of forced deregulation.I think we lose a lot of intangible things (as well as control over costs) when we contract out services - And once lost, national capabilities are hard - in some cases, arguably impossible to re-create.. I'll leave it at that because otherwise I would start ranting.Its a very important subject. let me return to NASA.NASA and space related public and quasi public entities use a wide range of materials and the spending decisions they make are probably arguably FAR more rooted in common sense than those made by most (all?) other US government entities at all levels of government, including state and local governments.When they use expensive parts and hardware, there is likely a reason, like, its the only way to get high reliability.Also, and this is important, they areconstantlytrying to think creatively ofcheaper and more COTSways to accomplishhigh valuethings.Quote from: NANDBlog on 2017-09-18, 16:53:26Of course, if you ignore the Nasa way, were a single bolt costs 1000 USD, but there are so many layers, that nobody can actually find the real cost of things.