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2017-11-24, 03:38 PM (ISO 8601)
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Which of these starship propulsion methods is best for an advanced society?
Which propulsion system has
Fastest travel time
is
Most efficient
Overall, which ship propulsion is "best" out of these choices
Ion Engine
Plasma engine
Solar sail
Antimatter rocket
Nuclear pulse
Black hole starship
Quark matter
Ramjet
Magnetic Monopole rocket
This may seem a bit opinionated but I just want the best engine possible that will allow interplanetary/interstellar travel quickly and safely.
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2017-11-24, 04:20 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
I mean, when it comes to Best it really depends on your story and how the technology works. Go read some Larry Niven stories, where he deals with the pros and cons of numerous technologies. the Known Space series (look for the Flatlander book of short stories) deals a lot with FTL drives. Protector uses Ramjets. Some earlier Known Space books about the Belters talk about how light sails are used. He's very good at explaining the technology simply while not getting bogged down in details, and they're quick reads.
For most efficient, the Solar Sail wins hands-down since it doesn't require fuel. It is hellaciously slow, though so these would mostly be used for travel within a system.
As for tech that we could theoretically build someday, a Ramjet is pretty darned efficient as well since it grabs its reaction mass from space, and should be faster than a sail. These should brush up to near light speed with enough acceleration room, so perceived travel time will actually be quite short due to relativity.
Everything else requires either magic technology or large amounts of reaction mass onboard, so they won't be as efficient.
ETA: I forgot to note that a Ramjet would be used in conjunction with another drive since they only start to work above a certain thershhold speed. So you'll use an ion engine or something to get up to speed, then kick on the Ramjet to really get moving.Last edited by monomer; 2017-11-24 at 04:22 PM.
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2017-11-24, 06:14 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
There is no simple answer here. These technologies either don't exist, or can't exist with our current knowledge of physics. Even with all these problems solved, non-magical interstellar travel will never be "fast". Flight times will start at many decades, move quickly to centuries, and only go up from there. That said, I have put some stuff below. If you want better answers, you need to provide more information about what you're trying to do.
I don't even know what you mean "black hole starship", "quark matter", or "magnetic monopole rocket". Magnetic monopoles aren't a real thing, quark matter could mean anything, and unless Hawking was very wrong small black holes aren't anything you want to be close to. I'd still like to know how you intend black holes to be used here though.
Ramjets don't work as well as first assumed, because interstellar space is really empty. There are still ideas like shooting fuel out along the intended path first, so you've actually got something to scoop.
Solar sails are efficient because like ramjets they don't need to carry all their fuel, but they'd be crazy slow. In theory you can boost them by using very big lasers fired at the sail, but that presents its own engineering problems. The lasers would have to be huge, draw immense amounts of power, and most of that power ends up as waste heat rather than useful laser beam. You might also need matching lasers at your destination solar system for braking. Personally I like the image of a massive laser array on Neptune, using the atmosphere as combined fusion fuel and heat sink, but I doubt it's actually viable.
If you're going for some form of rocket, antimatter is the highest density fuel source available, by a very large margin. The problems of making and storing it though are huge, especially when you also need that storage to be resistant to hitting an interstellar dust particle at 0.1 c or whatever your top speed is.Last edited by Excession; 2017-11-24 at 06:16 PM.
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2017-11-24, 09:01 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Clearly the black hole starship.
Cuthalion's art is the prettiest art of all the art. Like my avatar.
Number of times Roland St. Jude has sworn revenge upon me: 2
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2017-11-25, 05:27 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
FM radio car? Circular engine aeroplane?
If you want a breakdown of rocket engines from the real to the unreal and past that into total fantasy check out Project Rho.
Especially the Engine List.
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2017-11-25, 05:57 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
As a short answer, the less it accelerates you the more efficient it is, and generally also the higher total delta-v you can get out of it. I'm going to assume that torch engines (ones which accelerate at 1g for weeks or months on end) are completely and utterly science fiction, and look at them each in turn.
Ion Engine: as I remember this are insanely efficient, but very slow. Great delta-v though, and potentially worthwhile if you're using centrifugal gravity (ideally in a pair of counter rotating rings) because the thrust will be low enough that it won't register as any gravity. Not really breaking out of a planet's gravity well with them, but great in space.
Plasma engine: can we be more specific? Of the ones I know, I believe we get more thrust but less delta-v than an ion engine. There's a variety of different theoretical types, and those vary a lot, so we'd need to know, but generally a high efficiency engine.
Solar Sail: good for travel going from inner system to outer, I'm not 100% sure if there's an equivalent of tacking in space that'll allow you to go inwards (I believe there's a way to angle your momentum though). Very efficient as well, because we don't need remass.
Antimatter Rocket: the ones I know of are basically an alternative to ion engines, low thrust high efficiency. I believe they're higher thrust than ion engines without losing significant delta-v, but don't go dropping remass tanks from your designs.
Nuclear Pulse: ah, the closest thing to a torch drive that I believe has promise. Plus: works just as well breaking out of a gravity well as in space, high in both thrust and delta-v. Minus: irradiated planets when taking off from them, need to store the nukes. (This is Orion Drive stuff, right?)
Black Hole Starship: as soon as we get too close to the even horizon we die. Otherwise, we probably can't steer the darn thing, likely have to feed the black hole, and need to deal with Hawking Radiation. Rated 6/10, because the editor won't allow a lower score.
Quark Matter: what's this about? Insert rant about how most of matter is made up of quarks here.
Ramjet: if you're going fast enough you can probably get enough hydrogen to get a little bit of thrust. But you also have to deal with the fact that interstellar hydrogen will be hitting your collector at relativistic velocities.
Magnetic Monopole rocket: we need to find the bloody things before we can make a rocket out of them.
Winner, near future interplanetary travel: hydrogen-oxygen rocket. They look promising, and as a bonus should be usable on surface to orbit craft.
Winner, interplanetary travel: ion drives and antimatter rockets. We're going to be using the same trajectories if we use high or low thrust rockets, so the efficiency provided by these drives means we need less remass to do so or can do so potentially quicker.
Winner, interstellar travel: cyronics. Alternatively some form of antimatter torch drive, but either way we're still building a ship that's 95% remass tankage at the edge of the solar system.
EDIT: I am not a rocket scientist, take the above with a pinch of salt. I'm also not sure what the exact status on H-O rockets are and if we have working ones yet, because I can't be bothered to google it.
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2017-11-25, 11:39 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
IRL (outside of Greenpeace rallies) you don't get to pretend that there are no construction/maintenance costs.
Just like wind generators IRL do not get energy out of thin air, but transform metal/plastic into electricity, so will Solar Sail not rely on solar wind alone, but will transform construction materials (and, probably, energy used to keep solar sail functioning) into motion.
Consequently, you can't claim that Solar Sail is "most efficient" since it doesn't use fuel. It does. The "fuel" is the Solar Sail itself. Wear-and-tear is how this "fuel" gets "burnt".
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2017-11-25, 12:21 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Yes, but depending on requirements the amount of construction materials for a solar sail might also be low.
But to be technical, the solar sail does a massive advantage. Not in not requiring fuel (you'll still need that to generate energy, although only for the crew and not the drive), but in not requiring reaction mass (remass from hereon out).
Now again, I am not a rocket scientist, I'm just a barely-degreed electronic engineer who really likes rockets, so any values I quote will likely be way off.
Most engines require three kinds of mass, the engine itself, it's fuel, and it's remass. These are the thing that's performing the reaction, the thing that's providing energy, and the thing that's being thrown out the back to provide thrust. A chemical rocket combines it's fuel and remass together, so fuel is correct assuming we're talking about chemical rockets.
A solar sail is the closest thing to a reactionless drive that we've developed (at least theoretically, I'm not sure if we've actually sent one up yet). In fact it looks like the closest thing to a reactionless drive we'll ever be able to develop, ramjets have a bunch of problems, the Dean Drive becomes fishy if you think about it's premise even slightly, emdrive looks like a bust*, and there's nothing to suggest artificial gravity is even possible at the moment. That leaves a handful of reactionless drives that I don't know much about but have either been disproven or we just can't test. Solar sails have an incredibly useful property of offloading both the drive's reactor and it's remass storage to the same place, the star you're using (note in this case your remass is the photons that hit the sail).
The question is, does the size of your sail to achieve meaningful acceleration have to be large enough to render the lack of remass and engine fuel storage meaningless? I honestly don't know. Of course it will have to be repaired, but so will the entire hull of the ship. So the question is does the sail give enough extra surface area exposed to space that repairs will cost more than fuel and remass would be. I don't actually know, but I believe the general consensus is that they're better than chemical rockets cost-wise but worse than ion drives and plasma drives.
Now, bare in mind that it looks like no reaction drive is truly 'optimal'. I fully expect realistic space forces to include both efficient ion/plasma drives and high thrust rocket boosters.
*(although I use it in stories I'm using a hyperspace dimension with a strong magnetic field, run your hyperdrive on low and you can get up to about 0.5g thrust from your emdrive, run it enough to transition and you'll be able to accelerate up at several gs to a theoretical ~10c.)
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2017-11-25, 03:17 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
There is no "but". You are not contradicting my point (which is "solar sail is not inherently the most efficient") in any way.
No, solar sails doesn't have any advantages other systems can't offer. Reactionless drives are not limited to Solar Sail (see Alcubierre drive, for example of qualitatively different concept). Alternatively, mass can be gathered en route, making ramjets effectively reactionless.
Also, you are wrong about "not requiring fuel" (understood as "not requiring energy"), since Solar Sail might require quite a bit of energy to operate (magsails, for example; alternatively, self-repairing solar sails from smart materials).
On a miniature scale: IKAROS (Japan in 2010; 14m wide). In theory, we were supposed to have Solar Space Cup in 1992 (race to the Mars on solar sails), but only Soviets post-mortem presented something (Znamya 2 in 1993; on a proof-of-concept level, but still larger than IKAROS - 20m wide sail).
At the moment, there are no practically applicable solutions (capable of deploying square kilometres of sail to haul several tons of mass somewhere in less than a century).
EDIT: to put things into perspective, current solar sail technologies could be compared to paper ships.
Either way, we are not comparing existing technologies.
Only teleportation is.Last edited by Lazymancer; 2017-11-25 at 03:35 PM.
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2017-11-25, 04:55 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
YEs, sorry, I was more concerned with pointing out that remass also can have considerable costs (both tanks and the remass themselves, as well as the chemical boosters used to get remass back to the bottom of the tank).
No, solar sails doesn't have any advantages other systems can't offer. Reactionless drives are not limited to Solar Sail (see Alcubierre drive, for example of qualitatively different concept). Alternatively, mass can be gathered en route, making ramjets effectively reactionless.
FWIW a solar sail isn't reactionless, you're just offloading your reaction to the star you're sailing from.
Ramjets, while good in theory, suffer from a bunch of problems. First you have to have the remass tankage to get up to a minimum speed until you're hitting enough hydrogen within a short enough timeframe to achieve decent acceleration. Then interstellar hydrogen seems to be much rarer than assumed when ramjets were first designed, so either we need an even bigger scoop (requiring more materials or more likely more power to generate a magnetic field) or we need to be going even faster, and both of these require more remass. They're a neat idea, but just look impractical if you can actually hit the speeds to make them worthwhile.
The only pseudo-ramjets in fiction I even like are the Lighthuggers from Revelation space, and it's not explicit if they actually use interstellar hydrogen (not read the sequels yet, but they're essentially a piece of applied phletonium to allow ships to acclerate at 1g for years without massive remass tanks, and most human worlds seem to be in a cluster where lighthuggers only take about a decade to travel between stars EDIT: crew time, not observer time). Sure, for the same level of handwave Reynolds could have used a warp drive, but that's why it's fun.
Also, you are wrong about "not requiring fuel" (understood as "not requiring energy"), since Solar Sail might require quite a bit of energy to operate (magsails, for example; alternatively, self-repairing solar sails from smart materials).
On a miniature scale: IKAROS (Japan in 2010; 14m wide). In theory, we were supposed to have Solar Space Cup in 1992 (race to the Mars on solar sails), but only Soviets post-mortem presented something (Znamya 2 in 1993; on a proof-of-concept level, but still larger than IKAROS - 20m wide sail).
At the moment, there are no practically applicable solutions (capable of deploying square kilometres of sail to haul several tons of mass somewhere in less than a century).
EDIT: to put things into perspective, current solar sail technologies could be compared to paper ships.
Either way, we are not comparing existing technologies.
Only teleportation is.
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2017-11-25, 06:34 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
I am well aware of this.
Since most of your post is dedicated to proving Solar Sail to be more realistic/practical than the other technologies (often - in less than acceptable ways), it has to be important. However, I don't see what you are trying to prove and, consequently, consider any attempts to refute your arguments to be pointless.
Yes - the term "reactionless" was wrong. Propellantless would be more appropriate. Also, "reaction" gets "offloaded" to the radiation, the star is unaffected.
I do not wish to compare drives as such, since OP is irredeemably flawed. The "best drive" is determined by three factors: available technologies, available resources, and the problem that needs to be solved. Since none are known, no reasonable answer could be produced - only incoherent flame wars, fueled by differences between interpretations of the non-question by participants.
In this case, the argument is rooted in the fact that I did not interpret OP in a way that implies "feasibility" as something I should concern myself with - while you consider otherwise.
Then you agree that the point was not missed (provided that the feasibility of teleportation is irrelevant).
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2017-11-25, 09:56 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Look, you guys are missing the most obvious argument here.
Black. Hole. Starship.Cuthalion's art is the prettiest art of all the art. Like my avatar.
Number of times Roland St. Jude has sworn revenge upon me: 2
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2017-11-26, 12:26 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Alternatively, Transhumanism in certain forms. Robot bodies need far less maintenance than living humans, and digitally uploaded people can be stuffed into a freaking starwisp if you want. Even with cryonics, you have to bring all the messy stuff necessary for humans to survive in space in the short term, and that eats into your payload real quick.
Realistically, regardless of how you build the engine, with known physics we can reasonably postulate a rather massive starship that does some single digit percentage of the speed of light getting to another star with a payload of some triple digit metric ton payload. That's enough to send robot crew, some landing craft, and whatever sort of nanotech fabrication you need to get up to speed in situ from locally available rocks and gases so you can repair and refuel your starship and go somewhere else.
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2017-11-27, 07:07 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
The only pseudo-ramjets in fiction I even like are the Lighthuggers from Revelation space, and it's not explicit if they actually use interstellar hydrogen (not read the sequels yet, but they're essentially a piece of applied phletonium to allow ships to acclerate at 1g for years without massive remass tanks, and most human worlds seem to be in a cluster where lighthuggers only take about a decade to travel between stars EDIT: crew time, not observer time). Sure, for the same level of handwave Reynolds could have used a warp drive, but that's why it's fun.
Aaaanyway, digression aside. Maximum, I'm getting the impression you are asking about these drives without really knowing what they mean. Your question, to me, seems a bit like this:
"What's the best kind of transportation: skis, bicycles, sailing ships, oil tankers, high speed mag lev trains, flying carpets, a mountain or the boglovit?"
To which the answer would be "One of these is not transportation, but an obstacle , one of these we've never heard about, one is impossible fiction and the rest are used in different environments for different purposes."Resident Vancian Apologist
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2017-11-27, 07:16 AM (ISO 8601)
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2017-11-27, 08:09 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
I've got more RS universe lined up for once I've finished the first The Expanse book and/or I'm working somewhere where I don't expect my Kindle to get nicked. Might look into Galactic North, it'll be a toss up between that and Redemption Ark.
Aaaanyway, digression aside. Maximum, I'm getting the impression you are asking about these drives without really knowing what they mean. Your question, to me, seems a bit like this:
"What's the best kind of transportation: skis, bicycles, sailing ships, oil tankers, high speed mag lev trains, flying carpets, a mountain or the boglovit?"
To which the answer would be "One of these is not transportation, but an obstacle , one of these we've never heard about, one is impossible fiction and the rest are used in different environments for different purposes."
But yeah, good overview of it. Much more concise than my rambling 'this is a brief overview of each engine' post.
Speaking of asking about things without really understanding them, as this thread is here I don't think starting another space drive thread would be worthwhile.
Would I be right in thinking that current designs for ion drives would be giving us thrusts in the realm of thousandths of a g and plasma drives in hundredths of a g? I'm planning a science fiction story set within the solar system at the moment, and as it's mainly set on a ship with one of the two I was wondering if assuming the thrust was low enough not to significantly impact a 0.5g centripetal gravity ring.
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2017-11-27, 08:38 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
I guess the question is if you prefer the story or the setting. Chasm City, the Prefect and Galactic North are better stories in the same setting, but Redemption Ark continues the same story.
You might still want Galactic North first, though, as the characters who show up in the second book get very little introduction, as I remember it.Resident Vancian Apologist
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2017-11-27, 09:16 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Warhammer 40,000 Campaign Skirmish Game: Warpstrike
My Spelljammer stuff (including an orbit tracker), 2E AD&D spreadsheet, and Vault of the Drow maps are available in my Dropbox. Feel free to use or not use it as you see fit!
Thri-Kreen Ranger/Psionicist by me, based off of Rich's A Monster for Every Season
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2017-11-27, 09:47 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
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2017-11-27, 06:04 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Acceleration is going to depend on the mass of the ship, the thrust of the engine, and how many engines you use. Put enough small ion engines on something and you can get whatever acceleration you want (ignoring the weight of those engines). You could also distribute them around the ring to and get less structural stresses than a big engine in the middle. A bigger engine might be lighter for the same thrust and efficiency, or even more efficient, which would be good, but I don't know anywhere near enough about the engineering to be sure about that.
Multiple small engine also has the advantage of redundancy. If one engine fails, just adjust the others for balance and you're still good. You can also throttle by switching whole engines off, which may be easier than building an engine that can run at different levels.Last edited by Excession; 2017-11-27 at 06:10 PM.
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2017-11-27, 06:57 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
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2017-11-28, 06:57 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Interesting point on the engineering, I'll have to give it a think. Could lead to more of a 'spinning wheel' spaceship than I had originally intended, but I'd still likely want to include a second centripetal ring just to make sure forces roughly even out. I'm going to have to sketch it.
With regards to mass/engine size, yeah, I hear you. I'm more looking for rough orders of magnitude, the current design I have is roughly 10% engines to 10-20% crew quarters to at least 60% remass.
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2017-11-28, 09:11 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Cuthalion's art is the prettiest art of all the art. Like my avatar.
Number of times Roland St. Jude has sworn revenge upon me: 2
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2017-11-28, 10:50 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
I'd actually say that with a Black Hole, mass is one of your biggest worries.
Resident Vancian Apologist
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2017-11-28, 11:00 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
How the heck are those supposed to work? I can't get into the black hole in a state where I'm able to turn that matter into a starship.
Plus when somebody is mentioning that they're using low thrust reaction engines, 'you can solve all those problems with this idea that probably won't work and that I won't describe' is bad form.
Well it depends on the size, if it's small enough it'll radiate that mass away before you have to worry about it
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2017-11-28, 11:26 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Interested in MitD? Join us in MitD's thread.There is a world of imagination
Deep in the corners of your mind
Where reality is an intruder
And myth and legend thrive
Ceterum autem censeo Hilgya malefica est
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2017-11-28, 01:19 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
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2017-11-28, 01:36 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
The only way I could conceive of a black hole starship would have to use a particular kind of black hole, called a Kugelblitz. Depending on how the physics turns out to work beyond that singularity, the "black hole made of light" could have the gravitational pull of say, Earth, without any inertial mass. You could magnetically push in front of your hull (for practically no energy) and then fall towards it to wherever you needed to go.
It would also absorb or deflect a bunch of the space dust and radiation that makes relativistic travel a deadly problem."The error is to be human"
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2017-11-28, 02:16 PM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Well that's just silly. Clearly, you put the black hole in your starship. Now, black holes are difficult to move, so the best thing is to build the starship around the black hole, then have the universe move around it.
It's delightful knowing my work is appreciated.Cuthalion's art is the prettiest art of all the art. Like my avatar.
Number of times Roland St. Jude has sworn revenge upon me: 2
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2017-11-29, 07:18 AM (ISO 8601)
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Re: Which of these starship propulsion methods is best for an advanced society?
Aren't Romulan ships in Star Trek supposed to use some type of black hole technology for their energy reactors?