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  1. Doesn't that effectively mean "at re-entry speeds near sea level"? Granted, aero losses of trains are dominated by the losses along the side (probably excepting the fastest and shortest trains), so this might not be as bad as it sounds. Like "ground launch to orbit", it sounds like something that might work well on the Moon, but probably not even Mars. I think the US has higher passenger rail deaths than air deaths, although that might have been during a spike of rail accidents and can't include general aviation but is almost certainly true on a per-passenger basis. Also note that while the US passenger rail service might appear miserable to other industrial countries, rail *freight* is heavily used (often much more than said other industrial countries) and typically has control of the rails and thus makes upgrading passenger rail next to impossible. That and Americans tend to drive further, and when its too far to drive go straight to planes. PS: getting back to the subject at hand, I remember hearing about an upper limit (on the order of the speed of sound) for this type of thing thanks to back EMF produced by the rail car. I've never seen what would cause it (I'm reasonably familiar with Maxwell's Equations), but it seemed taken for granted in a group of fairly well informed space enthusiasts.
  2. One slightly different approach to "the next big thing" could be an overhaul to our IP laws. Currently, the whole system makes a mockery of the whole concept of "supply and demand" as there is an infinite supply of each "IP unit" that can be replicated as needed to nearly everyone. But modern economics is built on artificially limiting that supply, and typically intentionally damaging (see any Intel CPU, or most microelectronics in general) said product to allow different prices for segregated markets (another example is that it is cheaper to make "loaded" cars with all options than to build "base" models without them, at least until you add leather interiors). Compare the price of "officially licensed" and "legally branded" products to their exact knock-offs (often made with less volume efficiency) and you get the idea of the price of all that IP. On the other hand, alternative methods are few and far between. Copyleft is making progress, largely because software is the most extreme example of the above effect, but rarely directly provides the support for programmers and other IP creators that the corporations hoarding their IP can. Purely socialist economies haven't done so well, but it isn't clear that a system that privatized commodities (or production in general) and socialized the IP might not work. It would run into tremendous international legal issues (to the point of banning discussion as politics), so could only be done by a country capable of working outside of the current international legal system (through either ostracism or political power/size). I really don't think 3d printers could niavely perform such a feat, although perhaps something like kickstarter and similar could evolve to match "microfactories" that print molds and whatnot and quickly do small runs of specific products would be a thing. Getting crafters to figure out "all the steps in between" would probably be interesting, and lead to even more gripes about failed projects than currently on kickstarter. It is certainly a far more political/legal issue than a technological one, although certain technologies (like software is now) might speed up the process. NOTE: an idea very similar to kickstarter was floated on rec.arts.sf-lovers way back when the internet was new and established authors thought the whole idea was crazy that people would fund sequels to otherwise unprofitable works that were a favorite of a small amount of readers. Or perhaps Patreon would be a better model if relatively few people shouldered the burden of getting otherwise unprofitable books written and published.
  3. I wouldn't count out the catching problem yet. I'd be surprised if there was much more to it than "the pilot let go when the flight dynamics didn't match the mission plan". Although I suspect an update to the flight dynami model, and further testing with the new, improved flight dynamic. Of course, if the actual load of the rocket is too much for the helicopter (possibly noticed in non-catching testing), don't expect another catch attempt. I think the real elephant in the room is the Neutron. Presumably the future of Rocket Lab, and there is no way that thing is going to be caught coming down.
  4. Bill Nelson may well publicly state that "cost plus is a plague on us", but that won't stop senators from making sure NASA maximizes the pork on pork-heavy spending bills. It might help try to eliminate any cost-plus contracts in the budget they send to the White House (who may have friends to add some in) and in turn sends the combined federal budget to the House. But nothing stops the congress from funding the projects as "cost plus". This has been your US specific civics lesson for today.
  5. From what I understand (at least this was true ~2010ish), CMOS sensors are fully sensitive to IR light and it is only the filters placed on the lenses that makes a difference (presumably how they handle color as well). I was building cameras for iris identification and we lit the eyes up with IR (with obvious safety considerations). The CMOS image sensors were ordinary black and white sensors, no particular IR labeling at all (I suspect the guy who choose them had to go through a few datasheets checking that).
  6. Has SpaceX (or Musk) ever even mentioned mining anywhere (other than Mars for fuel)? If you are planning a colony, you'd think you'd want some sort of idea of what could justify such a thing.
  7. Aluminum is extremely abundant on Earth. Converting bauxite to aluminum is energy intensive to the point that sometimes aluminum is called "frozen electricity". When ever I hear suggestions in converting excess water (really methane) via electricity, I have to wonder if there is enough to not bother with aluminum. Perhaps the plants are sufficiently expensive (they also need a ton of heat, but the electricity keeps it expensive per kg of Al) that it doesn't make sense to run (or build to run) at less than max capacity. There are a lot of chemicals that need *lots* of electricity, H2 (especially from water) is just plane silly. Between the iron and the aluminum, that might do wonders for a lunar colony (for whatever reason you have one). I'd have to assume that thanks to various gravity wells, the asteroid belt is probably the only place worth mining for return to Earth. And the return to Earth will have some nasty politics all over it.
  8. Scott Manley had an interesting comment that the "paper" spinlaunch launch vehicle is roughly same size as Rocket Lab's Electron, and rough the same payload. But anything spin launch compatible needs to handle the g-forces. The tradeoff between rocket engines and heat shields doesn't seem to be a good one. He repeated that he didn't think that physics was Spinlaunches big problem. They will likely have far more economical ones. Granted, both fall under the category of "engineering".
  9. The sources they point to emphasize trading Isp for density. Not necessarily a bad choice for boosters (and possibly strap on boosters, but those love thrust which solids provide better), but they will almost certainly want something else for the second stage (and get most of the delta-v there).
  10. Also the stuff you really have to worry about goes away quickly on its own. It something emits a lot of radiation, each time it emits radiation an atom is decaying into the next (and less energetic) stage. If something is dangerous *and* has a long half-life, it is because it replaces atoms in your body and emits the radiation entirely inside the body. I also suspect that at some point fission will become more popular (presumably when it becomes hard to find places for solar panels and windmills) and there is a run on all the spent fuel rods to get that easily obtainable U235. I'd be curious to see if Jimmy Carter ever regretted his decision on banning reprocessing spent fuel (oddly enough, he was one of the few experts who got a chance to make a call on the political decisions based on technological problems).
  11. That's an order of magnitude lower than rocket fuel (although I suspect only a few times less once you add the mass of the oxidizer). You'll need large multi-stage fusion bombs to get back to the Isp you need to make Orion work. I'd strongly suspect that by the time such things got out of the lab [chemical ignition of fusion, multistage bombs exist. See Tsar bomb for a 3 stage monster] that some of the more accessible "fusion engines" (which don't necessarily require producing more power than input) would be available.
  12. I'm sure the politics inside the Pentagon and the Navy had plenty of admirals dead set that Navy would get plenty of nukes. And the many/most of them will be on *ships*, not *boats*. Submarines are classified as "boats". Not sure why. But putting your nukes on easily available targets doesn't seem smart (not sure how deep the armor goes on such battleships. Might want a nuclear torpedo to sink one, or just something with a lot of conventional kick as the armor rarely goes far below the waterline).
  13. I was just judging from the apparent mass when they lifted it. Of course, if they don't really want it to get off the ground it might have extra weights inside. Still wouldn't want to play with WFNA that way, I've read Ignition! as well.
  14. Originally I wanted to say "don't try this at home anywhere", but no strikethrough allowed in the title. https://arstechnica.com/science/2022/04/pythom-space-tests-its-rocket-with-questionable-safety-practices/ This thread links to some bozos testing a hypergolic fueled rocket. The article is extremely gentle to said corporation (the first comment in the discussion is the author stating he wrote the article for the "spicy" responses), but just watch the video. I can only hope that they fueled the rocket *after* transporting it there and lifting it into its vertical configuration. From the lifting sequence, it seems too heavy to be empty... I enjoyed my part in this thread: And I'd like to thank the KSP community for never considering hypergolics as an option for a major stage of said rocket. Not all the suggestions are remotely safe (there was talk of producing HTP at home), but nothing as bad as seen on this video. PS: also check out their plans on going to Mars. Now with even more chances to kill themselves.
  15. So just how complex is all this equipment you want to repeatedly nuke?
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