Jump to content


  • Posts

  • Joined

  • Last visited

Everything posted by Terwin

  1. In the release version, you need to have specific transport containers to count for vessel transport capacity.
  2. Compared to a pure-fusion Orion as advocated by that article, a fission Orion is likely a better choice, as it is much simpler. On the other hand, the article was advocating for a deep-space fusion Orion because it could refuel from ice or any other hydrogen source. Should the technical hurdles be over-come, there is the argument to be made that a pure-fusion Orion would be superior to a fission Orion with regards to ISRU. On the other hand, compared to a more realistic use of fusion for propulsion(mini-mag, fusion torch, micro-pulses, etc.) any form of Orion is the lesser choice. A 50g fusion pellet will not have the same out-put as a 100lb fission bomb. Then again, a 100lb fission bomb weighs more than 900 50g pellets, so even if the pellet has two orders of magnitude less impulse, it may still have a higher isp. To the best of my understanding, we have not yet successfully demonstrated a sustained reaction in a tokamak style reactor, but we have demonstrated fusion pulses(NIF). While it would be an awful design, we could theoretically put a NIF style ignition, powered by an on-board fission reactor, to super-heat the reaction mass for a deep space(low-thrust, high ISP) vessel. This would not require anything we cannot do today, so I would argue that a fusion micro-pulse propelled spacecraft is possible with today's technology, but a continuous fusion torch is not yet in our grasp.
  3. Sort of replacing the combustion of a chemical rocket with little bits of fusion? If you have sufficiently rapid small-scale fusion events, that sounds a bit like a fuel-rich fusion torch set-up when running. When using an actively cooled chamber/nozzle, I do not think that the heat is the greatest problem, but the pressure-wave caused by the fusion blast would very much be a limiting factor, as the stronger the blast, the thicker everything needs to be to contain it without popping like an over-filled balloon. Ablative cooling works, so long as you have ablative left, but it does not help much against pressure waves. I think pressure waves would be a bigger issue than straight-up heating.
  4. Fission does not scale down below critical mass, while fusion can scale all the way down to 17.6 MeV (2.8 x 10^-12 joules). The only reason to use a pusher-plate is if you have no materials that can contain/redirect the blast out of a nozzle. As a thin layer of balsa-wood is plenty strong enough to contain the 'blast' from a single pair of hydrogens fusing into a helium, you would need some serious handwavium going on for a fusion powered pusher-plate vessel to make any sense. Because anything less than 42 gigajoules(10 tons of TNT, aka smallest fission bomb yield and roughly 2x10^13 times the size of the smallest workable fusion yield) will attract the giant space-beavers that will eat your crew-cabin, then use the rest of the rocket to build their space-dams.
  5. Why? This gives you all the complexity of pure fusion(which can scale down to single fusion events) with the scaling problems of fission(minimum impulse size limited by critical mass). Instead of a single large impulse every X seconds, do 100 impulses of 1% of the large impulse at a rate of 100 per x seconds. This lets you reduce the strength of just about everything involved by at least two orders of magnitude, greatly reducing engine weight and improving TWR. Take this to the logical extreme and you have a drive that is either continuous or has very small discrete fuel 'pellets' igniting many times per second. Also, with fusion, you do not need pre-packaged pure-fusion bombs, but can instead use the same ignition source and just pump in the hydrogen you want to ignite(possibly in a magnetic bottle or some such). Why would this form of engine create mushroom clouds when other engines that also shoot out super-hot gas do not? There is no huge fireball to ascend into the sky and provide that mushroom shape(unless something goes very wrong, and at that point your ship is no longer reusable). With fusion, you do not want discrete bombs, you have a single reusable means of igniting the fusion that you use either continuously for a torch drive, or for small discrete packages of fuel for a pulse drive. Ideally, your fuel is a large tank of hydrogen that you can refuel anywhere with easily accessible hydrogen.
  6. Also, all of that extra detail is something that should only even exist if it will be a significant plot point. With science fiction, the needs of the story drive everything else. Everyone needs air to live, but how often does a story mention a character breathing? Only when it illustrates or extends something directly important for the story, the rest of the time, it is a useless side-bar that usually detracts from the story as a whole. If pusher-plates come up as a critical dramatic point in the story, then you have pusher-plates, even if they make no technical sense. If they do not serve as a critical dramatic point, then the reader should be completely ignorant of those drive details. If the story requires that an apollo stack can get to alpha centari in less than 5 years, then it can. If the story does not come first, then nothing else matters because no one will read it.
  7. Orion only works in atmosphere if you are ok with melting the whole thing and irradiating your cargo while you do so. (Atmosphere can reflect both heat and radiation, space not so much. This is not even considering the atmospheric shock-waves) All of the hardest parts of fusion rocketry are also required for a pure fusion orion. If anything they are made harder by having more space and an extended pusher-plate between the ignition sources and the ignition target. Fission is generally safer then fission, yes, but you may still have more radiation because your nuclear reaction is not inside of any sort of containment vessel.
  8. I was referring to liftoff, but an atmospheric retro-burn would likely be at least as bad, especially once you get sub-sonic.
  9. And this is why you cannot launch using ORION: anything strong enough to get it off the ground will melt your ship to slag. A pusher-plate will *not* shield you from atmospheric heating.
  10. They are in the save file. But it does not save modules, just the effects of the modules. So you will need to manually reverse the effect of any modules you want to 'remove'
  11. 5th percentile female is 4'11" 95th percentile male is 6'2" Just another place that being a statistical outlier is annoying (6'6")
  12. General relativity says that there is no absolute frame of reference. Everything is only relative to a specific point of observation. I had a physics professor that claimed he would define his house as the center of the universe. It may make some of the math more complicated, but it all works out. It is also just as technically valid as any other possible 'center-point'. That is also how you define an immovable object: that object is your reference point, so no matter if it is closer to Earth or Jupiter, it is still your origin point, and thus, by definition it has not moved.(but the math on the rest of the universe may get a bit complicated if a force is being applied to your immovable object...)
  13. Due to expansion, this would allow multiple objects that are at 'absolute rest' even though they are traveling at close to C relative to each other if they are far enough apart.
  14. You propose a definition of absolute rest to be going at a speed that is the average of your observable universe? Wouldn't that mean (possibly rapid) acceleration every time something left your observable universe? I think I would have difficulty agreeing that a state is 'absolute rest' if I can be pulled out of that state due solely to a very distant object moving beyond my detection range.
  15. To be fair, there may be 100x as many people working on tesla mass energy storage(Tesla wall?) as there are working on Starship, and I cannot see it mentioned in the news, especially here. There was also mention of converting atmospheric co2 into methane for Starship. If we are launching 1000 fully fueled starships towards mars every 26 months, that sounds like a lot of carbon that will be not only long-term stored, but physically removed from earth(some will come back, but I expect that most of it will not once out of earth orbit). I could even see the efforts towards buying twitter as an effort towards trying to prevent/limit civil warfare, especially around his research/production areas.(Assuming he could make discourse more civil on a large social platform that thrives on conflict(conflict increases engagement which in turn increases revenue))
  16. For an observer, they can seem to be moving faster than 300,000km/s, but that is only because as you approach c, the amount of time it takes for your subjective seconds to pass gets longer and longer. If you are going 290,000 m/s, each of your subjective seconds takes 3.9448 seconds for someone at your origin point, giving you a subjective speed of ~3.8c If you are going 295,000 m/s, each of your subjective seconds takes 5.615 seconds for an observer at your origin point, giving you a subjective speed of ~5.5c So you *feel* like you are going faster and faster as you approach c, but only because time is slowing down for you. Of course trying to figure out how this works when your origin point is traveling close to c compared to a reference point then you accelerate to bring your velocity close to that of this reference point, is beyond my simplistic understanding.
  17. Nothing can go faster than c (speed of light in a vacuum = 300 Mm/sec) Cherenkov radiation is due to particles going faster than light in a medium(usually water which is 225 Mm/s). So any particle that is shot though water at a speed higher than 225Mm/s will give off Cherenkov radiation. No need to go faster than c for this.
  18. So for the first few prototype launches they are using as small of a door as they can manage because that makes it easier to seal while they continue to iterate on the design. Once they have a more final design it will likely be more worth-while to spend the design time needed to have a larger opening.
  19. I don't see why not. You would need something to hide your plume from the surface while braking from orbital velocity towards a speed where you would not have significant friction heating.(Presumably you would do this over the day-side of the planet so scattered sunlight would reduce your visibility) Then do a controlled reentry where you keep your speed down and your radar-reflective surface intact until you are low enough for aerodynamic flight, at which point you can be just as stealthy as a B2 as you come down to land on a platform extended above the surface of the ocean by your secret underwater base.
  20. Drones and autonomous transport/navigation are both currently in periods of rapid expansion. Transportation might well be the next industry where we go from 'most people participate' to 'a few specialists take care of everyone' like happened with farming. Sure there will be hobbyist drivers, just as there are hobbyist gardeners, but I could see a 'self-drive' license become a rare thing for which most people have little need. Automakers from Tesla to GM are working hard on autonomous driving, and drones are becoming both cheaper and more capable. (I think GM even had an 'autonomous personal transport drone' in their super-bowl ad for point and click in-city autonomous air transport) I would be surprised if these technologies were not a game-changers at the very least.
  21. To me, that looked like a re-play with close-up specifically added to the tweet, not part of the original broadcast, so any audio would have just been a repeat of what was just said.
  22. If you get the habitation up to 5 years(I think, might be 50 for non-pilots) then the home and habitation timers stop. At that point it is considered a full colony and adequate for long-term habitation. Colony supplies can still be used in the medbay to bring back unhappy kerbals, but at that point the only reason to run the colonization modules is if you have reproduction turned on. As far as I am aware, the exact ratio of colony supplies to additional time has not been published(and is likely dependent on your hab-time/seat configuration). 3.75m has a 'time multiplier' of 6 and a rate of 0.000833 colony supplies/sec 2.5m has a multiplier of 2 for 0.000278 CS/sec This may or may not be related to their crew capacity which matches the time multiplier, but as 278*3=834, it looks like the efficcency may be the same between them. At first glance it *looks like* you may be getting 2 seconds of additional hab-time per 0.000139 colony supplies, but this would need verification.(it might only be 1 second, especially if your timers are stopped) This would be roughly 1 CS per seat for every 2 hours(or 3/day per seat), giving possibly 2 or 4 hours of additional hab-time per unit of colony supplies. Note: med-bays only work on disgruntled kerbals, but look to use roughly twice as many colony supplies per seat/time multiplier, but may also be affected by the number of stars the scientist has, potentially making it more efficient than a colony bay with enough stars. note: these numbers were taken from a 1.4.1 release of MKS
  23. Starship HLS plans to use "high‑thrust RCS thrusters located mid‑body to avoid plume impingement problems with the lunar regolith" when within 100m of the lunar surface. Not really mushroom shaped, and will still need elevators and such, but it sounds like even half way up Starship should be enough to avoid the primary issues. One thing we do not want, would be plume impingement on the body of the rocket itself, which is something that looks highly likely if we were to return to rockets with the fuel tank directly under the engine.
  24. Do you like to eat? Personally, I am quite content for the people who are growing my food to focus on how to do that the best way possible and not waste time worrying about the (often) made-up problems of the people who want to eat it. There are a *lot* of rules and laws already in place for food producers, and agricultural technologies are constantly advancing. Even for a full-time farmer or rancher, that does not leave a lot of head-space to worry about the behaviors of all those people who *need* that food to survive.(not unless they want to neglect their livelihood which *always* has things that can be done to repair, maintain, or improve the results) If your greatest pathogen exposure is spending one hour per week with your family in a room with perhaps 20 other families who also have trivial levels of exposure, your concerns over something like COVID will be different from that of someone who spends 8+ hours each day in an office with people from 50-100 other families, each of which has children in different schools giving exposure to hundreds of other families with a potential transmission delay measured in minutes or single digit hours. TLDR: If you want someone to do something for *your* piece of mind that will not meaningfully benefit them, then you are the one that needs to do the convincing.
  25. Can you provide any references/examples for bombs with multiple sequential fusion events? This is something outside of what I would expect and would like to know if I am mistaken. The reason fission is used to kick-start the fusion, is because you cannot fit other forms of ignition on a plane or missile. (the National ignition facility is large enough to hold 3 foot-ball fields for example)
  • Create New...