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Post by EshaNas on Jun 27, 2017 15:21:29 GMT
Any recommendations for hard sci-fi that takes a deeper look into mature interplanetary/interstellar civilizations' cultures, societies or communities? While there are some sci-fi books that look deeper into this, the only hard sci fi I've found that goes in this direction is the three body trilogy, but even in this series truly mature civs are only mentioned in passing in the third book. 2312 and Blue Remembered Earth? Though the latter has been called 'Libertarian Africans in SPACE', so there might not be much variety there, including an all pervasive security net sans one 'totally rad and free anarchy city on the Moon'.
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Post by EshaNas on Jun 25, 2017 22:40:08 GMT
You need more thrust than a resistojet to get out of the gravity well, otherwise your stuck spiraling thru a deadly band of radiation! I think no matter what, Hohmann orbits are going to be used for interplanetary travel for a long time. Nobody wants to be stuck on an orbit careening out of the solar system! With propellant depots that makes efficient but theoretical engines like MPDTs superfluous. We have a hundred years of experience with chemical rockets <3 Its like terraforming - by the time we have the technology to do something like that, we don't need it! MPDT's are not theoretical. And terraforming is not only hard, it's simply a less efficient use of mass than O'Neill cilinders. Spaceships are expensive, so you want them to make their trips quickly, so you can earn back your investment swiftly. You'd also want to limit the radiation exposure of your crew and passengers. People also prefer being stuck in tin cans for as short an amount of time as possible. Therefore, there are economic, health and comfort reasons for using high specific impulse drives (like MPDT's or Hall effect thrusters). And resistojets might not have the thrust to take off from the surface of the Earth, they have plenty of thrust to get out of a gravity well if you give them sufficient power. A 1 GW methane resistojet can have more than 3.41 MN of thrust. So you recognize that people don't want to be stuck in tin cans...and then say that it's more efficient in the long term on a thread of making humanity multiplanetary for people to live their whole lives in floating tin cans. Maybe some would prefer that, but I'm sure enough would be 'dirtside' to not care about the 'inefficiency'. Definitions like 'hard', 'efficient', and 'expensive' also change drastically with levels of spatial infrastructure, advances in technology, and even levels of government. A hyper-libertarian society chugging around with corporate or even personal rockets most likely wouldn't see terraformed worlds, but a mixed-economy hyperpower or even a collectivist union might at least try with their collective resources and capabilities, even just to the 'Okay, we can walk around without gear for a few thousand years and have a few standing million kilometers of water and a heavy ad-hoc ozone and Co2 atmosphere to help with radiation and heating' point, with further improvement thereof down the road if possible in the case of Mars or even just turning some ice-moons like Callisto or Enceladus into massive water-balls. But I think in the end that the major problem isn't even anything to do once we're in space. The main problem is getting to space in the first place, again and again and again. We can't blast antimatter or nuclear fire out of our lifters off Florida or Guiana, we're stuck with chemical reactions for that. And the best we have for that is theoretical metastable metallic hydrogen and some variants thereof. And let's hope the universe is so nice that such things could ever be exploitable.... This doesn't bar more 'stationary' infrastructure such as laser launches or launch loops or even magnetic fountains (though Earth so far prohibits Terran-based space elevators - lucky Luna and Mars!), of course, but if we're talking about doing things ASAP those things still require far more investment and maintenance than various disposable, partially reusable or fully reusable lifters. Getting to space constantly and efficiently and with numerous options for a myriad of roles is what's needed, thereof, nearly anything works with what we have now, if applied numerously enough, from nuclear to chemical to solar to antimatter.
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Post by EshaNas on Jun 25, 2017 8:49:17 GMT
Winchell Chung's 'Control Pillar' design might fit the bill. See here, scrolling towards the bottom of the page.
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Post by EshaNas on Jun 25, 2017 4:00:45 GMT
Again, the problem with MPDs and stuff like VASIMR is the power plant. They're great, they're environmental, but they need huge amounts of power for manned missions in a timely manner. That points us to nuclear reactors. Civilians on Earth handle nuclear reactors now, I see no reason to bar them for space civilians. If you're barring nuclear *motors*, that's a bit different, but even then, why? Even that can have a civilian version using lesser enriched fissiles while the military hogs the 80-90%+ enriched stuff.
But back to ion drives of all types. Zubrin, for instance, knows that the math on the VASIMR is solid, but because NASA doesn't have nuclear power plants on hand to churn out 10 MW, we're not going to Mars in 30 days and until NASA churns out capable nuclear tech all money into VASIMR is basically wasted, in his words, a 'hoax'. Last I checked, the nuclear space reactors we've made and tested are as follows:
SNAP 10A - 590 watts SNAP 2 - 3.5 kilowatts TOPAZ-I - 5 kilowatts TOPAZ-II - 10 kilowatts SP100 - 17 kilowatts SAFE 400 - 100 kilowatts Some Los Alamos Design, light nuclear fission reactor of some type, apparently 1 negawatt.
There are also some nuclear submarines which are 'light', I think my criteria was under 10,000 tones for total tonnage, but those reactors are well, for submarines, not spaceships, and conversion might not be worth the hassle. And because they're often military, numbers on the reactors themselves are hard to come by. The NR-1 apparently clocked out 144 kilowatts, the French K48 around 48 megawatts, and the American? S2C around 1.8 megawatts. Other subs might have 'small' nuclear reactors but their total tonnage conceals the tonnage of the reactors themselves.
Keep in mind these might be watts thermal or electric, I didn't note down which.
Of those, only the French sub reactor is useful for VASIMR, or 10 of those Los Alamos reactors, which I couldn't even find a number for. But putting the space reactors with a NERVA, or Project Timberwind or whatever came out of Project Prometheus or the Nuclear Cryogenic Propulsion Stage Project or the RD-0410 nuclear motors? Now there's something promising and relatively available.
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Post by EshaNas on Jun 25, 2017 3:13:15 GMT
Well, due to some practicalities of space "fast" has different metrics for travel and combat. In travel, you want to get from A to B in the shortest time possible. This means taking the shortest route possible, with the highest average velocity possible. So, the fastest thing would be something with very high dV so it can take a straight shot torch-ship style, burning half its dV accelerating and the other half decelerating so they don't overshoot the target. For acceleration, they just need enough acceleration to burn half their dV before they reach the half-way point of their trip (so they have time to turn around and burn the other half). So in this situation, the higher your dV, the faster you get from A to B so long as you have enough acceleration to make use of it. If you don't have enough dV for a torch-ship trajectory, things get much more complicated and it becomes a matter of orbital mechanics. For example, if the timing is right that extra 6km/s of dV could maybe allow you to take a shorter trajectory by cutting inside with an elliptical orbit, then circularizing and braking for a capture when you arrive. Burning it at the wrong time on the other hand, could cause you to miss your target entirely. The straight-line distance won't matter here, because you're not taking the straight-line route. The majority of time savings will come from reducing the distance you have to travel, rather than traveling that distance at a higher velocity. In combat, you're trying to overtake another ship and you'd probably prefer to do so before either of you runs out of fuel. So dV is a bit less important, though you'll at least want to have a bit more than your target so you don't have to worry about running out of fuel before they do. But acceleration will be much more important, because if you have much higher acceleration than your target you can quickly overtake them without having to run them out of fuel first. In this scenario, acceleration is basically your "speed", your ability to perform maneuvers more quickly, and dV is your endurance. You can catch someone by beating them on endurance of course, but you'd probably prefer not to. Thanks. The part I bolded is especially interesting. Though I guess something like the Antimatter-beam core designs do fall to Torch-Ship levels....
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Post by EshaNas on Jun 24, 2017 22:40:34 GMT
So we open up our files and just put this in somewhere? Neat.
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Post by EshaNas on Jun 24, 2017 7:50:57 GMT
I'm sorry to necro, but Astrogator, did you keep working on this, with the bi-propellant and updated shield?
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Post by EshaNas on Jun 24, 2017 7:19:43 GMT
How does one even go 'faster' in space anyway? Burning more D/v? Say I take my 'Fast' Courier with 20 km/s capability (mass ratio nearly 10), for a Mars trip from Earth orbit to Martian Orbit, that's around 12 Km/s needed, if I burn 6 more, would that cut the travel time by a fourth or so...and that's calculated by literally measuring the distance between Earth and Mars and translating the km/s to days/months?
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Post by EshaNas on Jun 22, 2017 11:12:34 GMT
IIRC, it doesn't make a black hole, it just explodes as a burst of gamma rays and high-energy particles when stopped - akin to a high-speed boat thrusting water onto a pier when it stops suddenly, while also taking on some water during transit. And that comes from no real paper or citation, just from a pop-science site.
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Post by EshaNas on Jun 21, 2017 19:35:32 GMT
Well, the main ship may not necessarily be designed for re-entry (although you could design the crew module for re-entry and eject it, like we do now). Of course, a crew module large enough to hold 80 people might be difficult to land without some absolutely massive retro-rockets. Though maybe we can make parachutes that big, I don't know. It still is pretty much only useful if you're in orbit of a habitable (or inhabited) planet of course. There have been designs for 100-strong SSTO VTVLs (the Kankoh-Maru) and even for Marine units (USMC, the RHOMBUS), but again, those are shuttles in our parlance, not really detachable modules, which would be more akin to the fictional command/primary hull separation stuff of Star-Trek, such as the Wasp class or more famously the Galaxy class's capability. Then again you can just give everyone an inflatable heat shield and hope you're close enough to re-enter, ala MOOSE. But in all probability in a battle 1) your crew won't survive as the crew capsule might be hit during the battle, 2) can't be rescued because enemy units are still in the area and will shoot anything down, 3) or can't be rescued because the battle was a joust in deep space next to nothing and the crew is whizzing away at solar escape velocity anyway.
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Post by EshaNas on Jun 21, 2017 0:33:41 GMT
It's no secret that we, daughter/son of the Madame President, whizz around the solar system in at most a 60kw nuclear fission rocket, from the Moon to Pallas to Mercury and beyond.
My question is: what's the math for this? The time-frame? I don't think we're spending two years waiting for Mars-Earth sweetspots or the like. Pardon me if this has been done before as well - I did a quick cursory search and found nothing.
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Post by EshaNas on Jun 20, 2017 20:37:32 GMT
At that point you don't need escape pods. Any small SSTO VTVL shuttle will do, like the Phoenix-S design which could already be shoved into inflatable modules. (Speaking off, where are the aux craft in COADE?) And in all cases, you'll be at the mercy of the enemy. If you land, it's probably because they wanted you to land.
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Post by EshaNas on Jun 20, 2017 19:14:07 GMT
You could do artificial gravity by rotating the crew compartment at relatively high speeds, granted that needs power and/or some sort of engine to keep the crew compartment rotating, if you don't want to spin the whole ship. This takes place in the year 5525, keep in mind. Though there ARE some ships that use centrifugal gravity to save on costs or if the required technology is unavailable. 5525 is really far. So far that only two main 'verses' really go that far: Asimov's Galactic Saga, where 5000 AD is the first dark ages (and overall has fallen to hard zeerust), and Orion's Arm, where the Inner Sphere era is ongoing, and anything not a damn AI basically exists at the whim of the AI who we can't even comprehend nor harm (generally dislocating and boring to average consumers), where the most recent thing was that a Middle-Sphere world colonized by people of South African stock had fallen to genetic plague (I'm not kidding). Are you sure you want that to be your year? Even besides the dearth in fiction, it's just hard to see oneself in. Though, hell, even anything beyond 2100 or so looks very hazy and becomes more and more generalized, at least if you want to stick somewhat with science and predictions and growth thereof.
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Post by EshaNas on Jun 20, 2017 11:14:09 GMT
The Alcubierre drive need not be FTL. If you could fold space to .9c, that'll still be something of massive interest. Like how Orion's Arm does it, none of their warpships breach 1c, they just get close to it.
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Post by EshaNas on Jun 20, 2017 11:10:40 GMT
I've been on a Space novel/book binge of late.
These are the ones I've read recently. No FTL travel or comms and at the least plausible tech.
On To The Asteroid by Travis S. Taylor and Les Johnson. A bit awkward, and the dialogue isn't going to win any awards, but a very mundane scifi work about asteroid mining and deflection. Some nifty tech appears, such as using superconductors as a radiation shield, which interested me a lot.
Coyote by Allen Steele is a veteran by this point, the collage of tales of plucky scientists and their families who flee the oppressive future theocratic United States by hijacking its vanity project of a spaceship and colony-project to the eponymous Coyote, a (fortunately) habitable moon around a Gas Giant.
Crowded Orbits: Conflict and Cooperation in Space by James Clay Moltz brings one back to reality with the current affairs of the space right around Earth: our satellites, space-stations, and the geopolitics behind them.
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