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Post by walterscientist on Dec 30, 2018 0:40:40 GMT
I want to try out some orbital transits between planets. I wanted to try them in Orbiter, but doing it in CoaDE should be more straightforward. My problem is that it seems that in Sandbox I can include only one planet, so I cannot try transit like in mission Homecoming. I thought maybe I could make a suitable mission using Level Editor. I tried to, but when I open a mission, I seem unable to edit it. Maybe the default missions are read-only? Do I have to somehow make my own campaign? Any help is welcome.
My goal is to figure out a scheme how to efficiently move people, cargo and fuel around the solar system for purposes of a possible hard sci-fi fiction. The notion is to have a net of stations spread around the system with slow ships moving fuel from where it is harvested to the stations and faster ships using this fuel to move cargo between the stations.
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Post by airc777 on Dec 30, 2018 1:46:12 GMT
Youtube user 'Isaac Arthur' is a good resource for futurism.
What exactly the fuel is will limit where it can come from which will kind of define the logistical infrastructure, as will how optimistic the science of the engines you use.
Due to abundance Hydrogen nuclear thermal rockets and/or Hydrogen magneto plasma dynamic engines might be the most viable in the longest term if you aren't willing to consider fusion torches or black hole starships or alcubierre drives. Having said that NTR's or MPD's only seem to work on an interplanetary scale and not a interstellar scale. Nuclear pulse propulsion might be another viable option, but from what I can gather people who have tried to build nuclear pulse ships in this game haven't had much success making them efficient. Solar sails or Laser sails are probably the best bet by far for using today's tech to go interstellar.
Getting the fuel to orbit is something worth considering. Space elevators could easily work on lower gravity moons and asteroids but we might not ever have a material with the strength to do it somewhere like earth. Orbital rings (as described in great detail by Isaac Arthur) could work in higher gravity environments, but they are colossal and they are actively supported structures. Orbital rings might be able to be used to farm Hydrogen from the gas giants. Star lifting could be used to farm hydrogen from a star, but that's dependent on how far in the future your setting is. Titan has standing lakes of hydro carbons.
'Slow' mining ships and 'Fast' transports is maybe a weird way to word it. MPD's and solar sails and laser sails accelerate very slowly but can achieve very high speeds, so in the context of a earth to mars transit they would be faster then quickly accelerating chemical rockets or NTR's.
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Post by walterscientist on Dec 30, 2018 2:24:57 GMT
Well, ships using MPD in CoaDE seem to have almost non-existent acceleration. I cannot try it, because of mission time limit, but with MPD-propelled Belt Trawler doing an orbit transit from Themis to Mars would take about 3 years, while NTR-propelled Methane Tanker can make it in 1 year.
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Post by airc777 on Dec 30, 2018 2:34:04 GMT
No they are faster. Have pictures, did happen. There's a whole thread on the forum of people doing this far faster then I have.
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Post by airc777 on Dec 30, 2018 2:36:06 GMT
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Post by walterscientist on Dec 30, 2018 3:08:45 GMT
I meant the stock ships - I suppose one can build a ship that has huge number of reactors - it probably requires custom modules? I dunno, when I tried to build a faster going MPD ship I did not have much success.
Also question would then arise how feasable would really be to build a ship with a terawatt of reactor power. That is more power than all nuclear reactors currently on Earth AFAIK.
Btw, how about help with custom mission creation?
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Post by airc777 on Dec 30, 2018 3:29:35 GMT
I meant the stock ships - I suppose one can build a ship that has huge number of reactors - it probably requires custom modules? I dunno, when I tried to build a faster going MPD ship I did not have much success. Also question would then arise how feasable would really be to build a ship with a terawatt of reactor power. That is more power than all nuclear reactors currently on Earth AFAIK. Btw, how about help with custom mission creation? What you are describing is an economy of scale problem, not a possibility of technology problem. Technically it's not currently possible for us to build any of this hypothetical infrastructure due to economy of scale. The International Space Station is only 463 tons. All of this is reliant on us building more, better, more efficient launch infrastructure, or building the infrastructure to mine resources in space. But that's what we are discussing doing, is building more infrastructure.
Just building a ship with more reactors isn't a thing that we don't know how to do, we would just have to build more of them. The ship that I posted was only 100 GW, not one or more terawatt, and it had more then 700 km/s of delta V and only a 4 month burn time. That's still far more then enough to get anywhere in the solar system in a very short amount of time. You could build a much more conservative ship to achieve the same effect.
Oh, and I have no idea how to do custom missions.
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Post by walterscientist on Dec 30, 2018 4:09:02 GMT
I am now pretty sure your ship requires much more efficient than stock modules - with stock modules my ship with similar weight as yours is orders of magnitude worse in both acceleration and delta-v. I searched for some kind of guide for better MPD, but found none and I don't have time to spare for experimenting. Attachments:
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Post by airc777 on Dec 30, 2018 4:42:52 GMT
I am now pretty sure your ship requires much more efficient than stock modules
Apophy's reactors are really efficient, but they aren't physically impossible and they aren't using processes that we don't understand. They are still just fission reactors. These particular fission reactors are using a lot of osmium, and they are designed with power to weight ratio prioritized over cost, but that's really not unreasonable. Osmium is 'rare' here on earth because most of it is in the earths core, asteroids don't really have that problem. Machining osmium is something that would be difficult because of how hard, and brittle, and heat tolerant it is, but iridium has similar properties and we use iridium for things as mundane as fountain pens. As soon as it is economically viable to use osmium for thing like tools then processes for machining it on a large scale will be developed. Real world reactors are big and heavy because we shield them with concrete because it's cheap, we aren't going to launch a concrete shielded reactor into space, lighter alternatives will be used.
These are still fission devices, not fusion devices.
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Post by apophys on Dec 30, 2018 11:12:12 GMT
I want to try out some orbital transits between planets. [...] I thought maybe I could make a suitable mission using Level Editor. I tried to, but when I open a mission, I seem unable to edit it. Maybe the default missions are read-only? Do I have to somehow make my own campaign? Yes, default levels are read-only. The simplest is to use a custom campaign with one level in it. I made one for you just now, with the important bodies up to Jupiter: UserLevels.txt (1.83 KB)Put this in C:\Users\YourName\AppData\Roaming\CDE Merge the content if you already have custom levels. (Be sure not to use Notepad, because it screws formatting. Wordpad is fine.) Propellant is cargo like any other raw material, imo (which is probably what most cargo trade will be). Fast ships would only be needed for human passengers or expensive priority cargo. In each case, you'll want MPDs (or other high-exhaust-velocity drives), just with different mass ratios on the craft. Slow transit would use very high payload fractions (large majority of the craft's wet mass being payload), and save propellant using slow but efficient orbital transfers (like bi-elliptic). Rapid transit would carry plenty of propellant and burn a few hundred km/s dV on fast near-brachistochrone transfers. What exactly the fuel is will limit where it can come from which will kind of define the logistical infrastructure, as will how optimistic the science of the engines you use. [...] Solar sails or Laser sails are probably the best bet by far for using today's tech to go interstellar. I like CO 2 or O 2 for ion drive propellant. CO 2 is easily siphoned from Venus or sublimated out of icy asteroids/comets. O 2 is a waste product of refining metal from rock, and can be processed from CO 2. H 2O or CH 4 are commonly considered due to their decent performance in thermal drives (but I don't see those as very relevant for interplanetary travel, only for surface liftoff to orbit... or for space combat). H 2 is very annoying to store (supercold, low density, & leaks out through walls), making the mass ratio of tanks terrible. For going interstellar, relying on only the sun for your sail is too weak & slow. Laser sails are good, though. Riding a neutral particle beam might be even better, due to the superior efficiency achievable. Combining the two may be possible, to improve focus over long distances (see PROCSIMA). I like air-breathing laser thermal for that purpose, because it's easily scalable, very cheap to operate once you've got the infrastructure, and the infrastructure can be multipurpose (asteroid sampling/defense, laser sail, interstellar comms, military, etc). I meant the stock ships - I suppose one can build a ship that has huge number of reactors - it probably requires custom modules? I dunno, when I tried to build a faster going MPD ship I did not have much success. Also question would then arise how feasible would really be to build a ship with a terawatt of reactor power. The important statistic is not the total power of reactors, but the specific power of the full system. That is: the electricity generated, divided by the mass of reactors + radiators. Yes, custom modules are needed, since stock reactors are horribly heavy and output heat at low temps (requiring oversized radiators). IMO, they are by far the worst-optimized stock parts ingame. You can do perfectly fine on merely 1 GW. More is always better due to the dead mass of the crew module, which doesn't scale up along with the power system. I searched for some kind of guide for better MPD, but found none and I don't have time to spare for experimenting. The wiki is woefully incomplete & a bit outdated, but: coade.wikia.com/wiki/Magnetoplasmadynamic_Thruster (written by me, btw) Or you can use the MPDs in my thread. I've got neon, CO 2, O 2, D 2O, CH 4, HD, & RP-1 from 10 MW to 100 GW. These particular fission reactors are using a lot of osmium, and they are designed with power to weight ratio prioritized over cost, but that's really not unreasonable. Actually, I prioritize low cost over low mass, within reason. Other people have made lighter but more expensive reactors than mine, e.g. Ianthe on Discord. Osmium + tungsten is just a bit better than tungsten rhenium + tungsten (if you ignore expansion stress by using multiple stages), which is what we use IRL for high-temperature thermocouples.
One major reason osmium isn't used much is that it creates osmium tetroxide (OsO 4) when exposed to air. Osmium tetroxide easily vaporizes and is extremely toxic. So you can't leave osmium metal exposed to our atmosphere. Not a problem in space, though.
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Post by AtomHeartDragon on Dec 30, 2018 11:41:23 GMT
I meant the stock ships - I suppose one can build a ship that has huge number of reactors - it probably requires custom modules? I dunno, when I tried to build a faster going MPD ship I did not have much success. I have an abortive attempt at laserstar using stock stuff and xenon propellant. It doesn't seem to work well.
With custom MPDs and reactors the main issue seems to be pumping gigawatts into at most dinner plate sized thrusters - I do expect this kind of power density to cause... interesting engineering problems CDE's equations for MPDTs aren't really equipped to deal with (even stock MPDTs are way beyond any existing applications AFAIK). OTOH you could reasonably plaster the entire rear of your ship with more reasonable MPDTs - huge arrays of redundant components shouldn't really have maintenance costs scale up like they currently do.
For just moving around solar system, with required infrastructure in place, you should look into beamed propulsion. If you aren't fighting or venturing into great unknown, you might as well leave your bulky powerplant back home.
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Post by walterscientist on Dec 30, 2018 14:09:42 GMT
With custom MPDs and reactors the main issue seems to be pumping gigawatts into at most dinner plate sized thrusters - I do expect this kind of power density to cause... interesting engineering problems CDE's equations for MPDTs aren't really equipped to deal with (even stock MPDTs are way beyond any existing applications AFAIK). That is rather relevant. How effective MPDs can be expected from applying tech currently in development? I intend to have as starting point technology we know can be built.
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Post by apophys on Dec 30, 2018 16:36:59 GMT
With custom MPDs and reactors the main issue seems to be pumping gigawatts into at most dinner plate sized thrusters - I do expect this kind of power density to cause... interesting engineering problems CDE's equations for MPDTs aren't really equipped to deal with (even stock MPDTs are way beyond any existing applications AFAIK). That is rather relevant. How effective MPDs can be expected from applying tech currently in development? I intend to have as starting point technology we know can be built. "The device has been operated with currents up to 300 kA and power levels up to 200 MWe. These values are among the highest levels reached in an magnetoplasmadynamic thruster."
"A time-dependent, two-dimensional, axisymmetric magnetohydrodynamics code is employed to model, validate and extend the experimentally-limited performance characteristics of a gigawatt-level plasma source that utilized magnetoplasmadynamic (MPD) acceleration for gas energy deposition. [...] They also allow examination of the device as a very high power MPD thruster operating at power levels in excess of 180 MW."
You can build such things. Note that you need enough active cooling of the waste heat, or you're limited to very short pulses (not modeled in CoaDE, sadly).
"The MPDT has a unique place among electric thrusters in its ability to process megawatts of electrical power in a small, simple, compact device and produce thrust densities (thrust per unit exhaust area) of O(105) N/m2. However, this major advantage of the MPDT has also been the disadvantage to its development. Since high efficiencies (greater than 30%) are only reached at high power levels (exceeding 200 kW), MPDTs require power levels that are an order of magnitude higher than what is currently available on spacecraft in order to be competitive with other propulsion options. Therefore, research on MPDTs was largely sidelined, in favor of thrusters that have higher efficiencies at lower power levels."
CoaDE's MPD modeling seems to be quite good, since I have seen this effect when designing them. Thus why my lowest-power standard MPDs are 10 MW for most propellants, or 1 MW for HD.
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Post by airc777 on Dec 30, 2018 18:17:49 GMT
I like CO 2 or O 2 for ion drive propellant. CO 2 is easily siphoned from Venus or sublimated out of icy asteroids/comets. O 2 is a waste product of refining metal from rock, and can be processed from CO 2. H 2O or CH 4 are commonly considered due to their decent performance in thermal drives (but I don't see those as very relevant for interplanetary travel, only for surface liftoff to orbit... or for space combat). H 2 is very annoying to store (supercold, low density, & leaks out through walls), making the mass ratio of tanks terrible. For going interstellar, relying on only the sun for your sail is too weak & slow. Laser sails are good, though. Riding a neutral particle beam might be even better, due to the superior efficiency achievable. Combining the two may be possible, to improve focus over long distances (see PROCSIMA). On the one hand I dislike the idea of using the biomass sustaining bits of atmosphere as reaction mass, on the other hand this means spacecraft with just have kilotons of atmosphere with them half of the time.
Couldn't you build a double hulled tank for storing H2, with something like a mercury vacuum pump or some other extremely low pressure pump process recollecting the leaking H2 from the outer hull?
Stellaser sail? Stellaser sail. Perfectly good reason to build a Dyson swarm, I mean Mercury's mass currently isn't doing anything else useful.
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Post by walterscientist on Dec 30, 2018 22:41:12 GMT
I tried building an MPD-equipped ship as light as practically possible - got this, seems pretty nice: Attachments:
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