Thor Wotansen

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About Thor Wotansen

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  1. That landing was epicly casual, lol. The booster was like "man, I got this."
  2. Well, if you do design a separate service module for Dragon to dock to to go around the Moon, you could always add in a cabin, I mean, you're already docking to it. That way you wouldn't have to jeopardize the abort capabilities of the Dragon by loading the trunk with a full service module.
  3. It would be easier to launch a separate service module on the FH and then launch a Dragon on a F9 to dock in LEO before going on to the Moon. The 30ish tons of payload should be enough for a service module to put a Dragon around the moon and back.
  4. @kerbiloid and @Dragon01 what do you guys think about Thorium liquid sodium reactors? I know you guys have a lively discussion about nuclear treaties over in the SSTO thread, just thought I'd throw another element in the mix over here.
  5. I'm starting this thread as a place to discuss ideas and nerdy details for all forms of alternative energy, from nuclear reactors providing electrical power, to linear generators powered by the movement of a human doing human things to power personal devices. It seems nerdy discussions of the merits of various energy sources and their carbon footprint pop up in various places, so why not condense them into one place? To start off, I've had an idea kicking around in my head for a year or so now, for a linear permanent magnet generator built into something like a knapsack or backpack that charges a few 18650 cells for the purpose of recharging personal devices like cell phones and cameras. I've seen flashlights use these and achieve remarkable efficiency in the process. Something similar could also be built into a belt or something you can clip onto a belt, and your batteries could be arranged like the ammo belts of the wild west for that cyberpunk look. Another idea I had is a collapsible vertical axis wind turbine that can fit in a bag like the ones you stuff camp chairs into. There's a lot of options for outdoorsy types to recharge things with solar, but solar doesn't work so well under trees or at night. I haven't done any 3D modeling, but the geometry should work.
  6. From Wikipedia: The reaction is exothermic, meaning it produces heat. This means you can remove heat while still maintaining the 300-400 °C needed for the optimal reaction. Heat can be used for all sorts of useful things, like powering a sterling engine to run a generator to electrolize water for hydrogen, or liquefy air to extract pure CO2, with a cryocooler. So yes, as long as you don't let any methane escape into the atmosphere, you can have some of your lunch for free.
  7. I believe SpaceX is eventually planning to have a ISRU unit using the Sabatier process to make their own methane out of a bit of hydrogen and CO2 from the atmosphere. One benefit of this is that it creates a decent amount of excess energy that can be harnessed to do things like make electricity. I wouldn't be surprised if SpaceX was carbon neutral by 2030.
  8. I wonder if they're going to use the Roc to transport submarines or something.... I do hope it gets used for something, and doesn't just become another aviation record holder that slowly wastes away in a hangar somewhere where people pay $5 to see it.
  9. Sounds like it might end up being a net loss then....
  10. I have a very hard time imagining a serious spaceship design that includes 6 meter thick concrete anywhere, while still being something that can accelerate at multiple Gs. The reason we use concrete as radiation containment for reactors here on Earth is that it has a fairly high water content (hence hydrogen), it is a structural material that is easy to build with, it can be mixed with all sorts of things like pieces of lead, and it's very inexpensive compared to other alternatives. We also tend to worry about contamination of the surroundings of the reactor, something that's just not a concern in space. A spaceship with a fission or fusion reactor will have minimal radiation shielding compared to a ground based power plant, and it will not use 6 meters of concrete for any of it. There are plenty of materials and techniques for shielding reactors that are significantly lighter and more compact than concrete, not to mention easier to produce in places without limestone. A 10kg tungsten projectile traveling at 5km/s is remarkably good at poking holes in all sorts of things, since 10kg of tungsten is only 520 cubic centimeters, or a little more than half a liter (~1 quart, 22lbs).
  11. I you punch a neat hole in a nuclear reactor, how well does it work? Deigning armor to defeat a high energy projectile that shatters like that is challenging, but doable, especially if you use your armored outer hull as an oversized whipple shield and armor your reactor with a good slab of high strength ceramics with a reactive surface composite over top. It's much harder to design an armor system to defeat a solid slug that doesn't deform much on it's way through a nuclear reactor at a decent fraction of orbital velocity for LEO I know the writers of The Expanse aren't science nerds to the level folks like us are, and therefore I forgive them for writing a railgun that fires projectiles at relativistic speeds that can be mounted to a ship or space station. Let's be real here, it doesn't matter if you're firing a one gram projectile, if it leaves your barrel at "near relativistic" speeds, your ship/space station is being flung in the other direction with some alacrity, that is if it hasn't turned itself to plasma in the process of accelerating that slug. 5-10km/s in a vacuum environment with near-ish future tech is believable, but nothing short of a massive mass driver built into a moon is going to get anything to near relativistic speeds without some serious issues. The Lorentz forces on the rails from the energy needed for that kind of speed would overcome any structural material we can imagine, not to mention the sheer amount of electrical energy you'd have to put through the rails to achieve those forces. You'd be better off using a nuke as propellant for a big slab of something. A more sensible solution would be a staged coilgun with a barrel a good 100km long accelerating a 500kg hunk of steel to 20km/s or something, maybe even 30km/s is believable for a mass driver of that size.
  12. Tungsten is a remarkable material, it is incredibly dense and is one of the toughest metals we have. A solid slug of it won't really deform, even at thousands of Gs acceleration. The biggest problem with railguns is getting the slug to transmit all the power without welding itself to the rails. This is normally done by getting it going at a good clip before it reaches the rails. The other big problem is heat. This can be mitigated by using a high temperature superconductor like a Yttrium/Barium conductor at a temperature of around 77°K to transmit the power to the rails. We might even be able to use the superconductor as the rails, but I don't think that's been tried yet. Basically, with better materials and a longer barrel, as well as the fantastic thermal properties of a vacuum, it should be possible to make a railgun that fires a smallish tungsten projectile at a good 5km/s, more than enough to overcome whatever armor you'd be inclined to wrap your reactor in. Most reactor armor will be geared toward defending against more conventional guns, like PDCs, since they'll be more common in the battle space. If someone makes a railgun that can fire a 10kg slug at 5km/s there's really no point in trying to armor something to withstand it, especially if you want that something to move.
  13. The form and organism takes is highly dependent on it's diet. For the most part, I would expect that most, if not all, species that achieve intelligence and sentience to be omnivores. Large carnivores are, by nature, very territorial, and they are unlikely to develop agriculture or fire, since evolution would have given them a digestive system that obviates the need for plant crops and cooking. Without agriculture or fire, the species won't advance to the stone age. A herbivore might be able to pull it off, but most herbivores go for either big herds for safety in numbers, or for large size (or both). They also tend to have no need of cooking, and will instinctively fear fire, as well as a lot of other things. Their digestive systems require a lot of intake to provide the energy they need, and in general, high energy foods like grains and starches, are quite unhealthy for them. Omnivores, on the other hand, aren't specialized in eating any particular thing, which means their digestive systems kinda sucks at a extracting energy from a good portion of their diet. This means that cooking is a massive advantage, and therefore, taming fire is more likely. This means that our species must have some way of easily manipulating things. Humans evolved from apes, who were optimized for life in trees, although the larger apes evolved to work better on the ground. Humans are the pinnacle of the ground apes, having evolved to have absurdly high stamina, which allowed our ancestors to chase down game like antelopes and deer until they literally died of exhaustion. Our ancestors that lived in trees gave us thumbs and an upright posture, as well as large brains and sharp eyes for calculating jumps between branches. This means that Humans are uniquely specialized in pretty much nothing, but our stamina allowed us to develop all sorts of things. Any technological race, therefore, will have a similarly convoluted evolutionary history, since evolution won't just crank out a big-brained creature that can eat just about anything, with huge stamina reserves and spare appendages for grabbing and carrying things. Instead it will tend to optimize for other things. The creatures that evolve to a technological level will come from tiny niche environments that are sufficiently isolated to allow time for evolution, and sufficiently rich in resources to allow a non-optimized creature to succeed. This rules out any extreme environments and probably also any large biomes. Essentially and technological species will be similar to humans in form, baring any variation in ancestral lineage regarding numbers of limbs and whatnot, although I'd expect four limbs to be pretty common, since more limbs means more muscle and bone for not that much more benefit. That's not to say they won't look really alien, they might have their noses in weird places, or have a prehensile tail. The largest variations will likely be from their planet's gravity and atmospheric density, as well as the nature of the environment they came from. On a planet with lighter gravity (unlikely because of a number of things, but not impossible) they may still live in forests to titanic trees and use their lower limbs as their "hands". On a planet with higher gravity, they might indeed have six limbs and be very squat and muscular. It is very unlikely, though, that any race from a planet with higher gravity achieves space flight. The gravity of Earth stretches the limits of what is possible with chemical fuels, and any planet with higher gravity will require too much ΔV to get any meaningful payload into space. In summary, the most useful feature for a humanoid race of sentient, technological beings is probably a home planet with an orbital velocity of around 7km/s, an orange dwarf as a sun, and a large moon with a molten core that helps their planet maintain a very strong magnetic field to keep the solar wind of a more active star at bay. A thicker atmosphere might also help, but it could also be a hindrance.
  14. That's fair, although it might be more cost effective to just send 150t of starship ring sections curled up tighter in the cargo bay, and weld it in situ into whatever you need. Insulating it will consist of shading it from the sun and any reflected or re-radiated energy and sticking a little cryocooler on it with a big honking radiator. Even a fairly low powered unit would be very effective in an application like that. With 150t of soft landed cargo you'd be ale to get far more in the cargo then you'd get from the ship itself.
  15. The problem with railguns will always be that they punch neat holes through things. If I were designing a spaceship for the kind of combat we see in The Expanse, I would engineer the railgun projectiles to punch through the crew compartments exactly like you see in the show. The reason is that the railgun is meant to take out things like drive clusters and reactors, and seriously damage the structure of the vessel, and if it was built to shred the crew compartments, it wouldn't to squat to a reactor with it's heavy shielding and (presumably) armor. I would even go so far as to say that taking out the crew compartments isn't even a priority. Sure, the PDCs and railguns will poke holes in them, and any crew in the way, but the real targets in a fight like that are the crucial systems of the ship, not the crew. This is why I'd have the PDCs firing 20mm armor piercing incendiary rounds, so they wreck any surface mounted equipment like thruster clusters, PDCs and launch tubes, as well as doing damage to the underlying structure of the ship. Missiles would be either nukes or would be designed to take out the main drive systems. The railguns are to poke holes in the reactor(s) and reaction mass tanks from farther away then PDCs can do.