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Everything posted by Piscator

  1. I was tempted to interpret "coolest" literally and pick Pluto, but then I chose Earth after all. It's where all the interesting biology is happenening.
  2. Is that a crewed demo of a landing or a demo of a crewed landing? In the second case, you wouldn't necessarily have to have people on board. It would probably suffice to have life support and so on working flawlessly.
  3. Yeah, it looked very different to me in the wide angle view as well. I guess both boosters slowing down so much before touchdown gave me a wrong impression.
  4. I'm not a 100% sure I remember this correctly (well, actually not even 90%), but the difference in timing of the two boosters might only seem more pronounced this time, because they accidentally showed footage from the same booster on one of the previous occasions. The external footage of the two boosters coming down didn't seem much different from earlier flights.
  5. It's also quite noticeable that Webb doesn't see just more, but also different stars than Hubble. The "blue" stars in the Webb image correspond to the "red" stars in the Hubble version pretty closely. But even the most prominent of Webb's "yellow" objects don't seem to show up in the other image at all. That's of course to be expected but it's still interesting to see.
  6. Luckily we don't need to worry about the environmental impact of methane as a lifting gas since it's completely unfeasible in this role anyway. Half the lifting capacity doesn't sound too bad at first, but simply building your airship twice as large is only a solution if you somehow manage to keep the structural weight the same. Which is of course impossible. Even if the square-cube-law works in your favour - and I'm not convinced it does in this case - you would likely end up with a monstrosity of a vessel just to get of the ground.
  7. Couldn't you basically cover the planet (or at least the tidally challenged parts) with subterranean artificial gravity generators to keep the water from falling into the sky? PS Would be possibly quite interesting to have a planet that would naturally self-destruct if there was ever a major power outage.
  8. Thanks for confirming my back-of-the-napkin calculations. I was using a dry mass closer to 100 tons but I also took the additional ~1000 cubic meters of payload volume into account. Since Wikipedia gives slightly higher surface densities for Venus' atmosphere at ground level (probably due to not being an ideal gas and/or being supercritical) and since it can also be assumed that the tank's contents will warm somewhat during decent, things might in fact even look a bit more favourably. Since Starship wouldn't have to be stripped down too much, re-entering form interplanetary velocities might not actually be much of a problem. That's what it's designed to do anyway, if I'm not mistaken. If push comes to shove, there should be a sufficient delta-V budget to slow down propulsively.
  9. If it’s light enough, large enough, and stiff enough, it will deorbit with just fine with minimal heat shielding required. Actually, we might be close to the point where we can try this. Depending on the final figures for dry mass, internal volume and how you pressurize said internal volume, Starship (usual disclaimers apply) might be just buoyant enough to float in the lower parts of Venus' atmosphere. It wouldn't excatly qualify as an airship and would likely have not practical value whatsoever, but it might not touch the ground for a while either.
  10. Using an alloy that's liquid or close to liquid at room temperature makes for a pretty lousy hybrid rocket, I'd assume. Probably depends on what your local room temperature is, though. That said, I can see a use case for metal/oxygen (rich) hybrid rockets on worlds without readily available hydrogen and low delta-V requirements like e.g. the moon.
  11. If I remember correctly, it was considered to send Dawn on a fly-by mission to a third object in the asteroid belt, but in the end they decided to do some additional cool stuff around Ceres instead. Also rovers regularly seem to find themselves with enough delta-Wheel left for an extended mission.
  12. Just figuring out all the launch windows until 2023 doesn't mean they intend to launch in 2023.
  13. Maybe they should switch to ethanol fuel then. Even friendlier to the environment and more fun to "eat the sledge dogs".
  14. Well, nitric acid is actually pretty friendly to the environment. The trouble is, it's rather less friendly to things running around in said evironment. At least in its concentrated form.
  15. Actually not a bad name for a first stage. Goodbye, "Denial", we hardly knew ye.
  16. Hm, looks like the Martians made it here first ...
  17. I assume this is less about an attack on SpaceX itself and more about keeping the Starlink network operational in regions where someone might want to restrict access to it. Hard to tell from one tweet though.
  18. Iron particles in the blood would very likely kill you. The iron contained in your blood and the iron that's attracted by a magnet are two rather different things.
  19. A more fundamental problem might be that the whole concept of a warship in space is probably obsolete. As long as your most effective weapons are limited in range it makes a lot of sense to put a bunch of them on a vessel and drive them where they're needed. In space, range is not really an issue. There is little need to send a ship to Mars to launch a lot of warheads if you can just launch the warheads from Earth.
  20. That was the passage I was referring to and I came to the same conclusion pretty much. Which is why I didn't consider the source overly reliable. I was thinking about the topic quite a bit after my last post and I'm not sure that this is really how it works. Please correct me if you find a flaw with my line of argument, but as I see it, the essential part of boiling vs evaporation is that the pressure throughout the liquid needs to be lower than the current vapor pressure for boiling to occur. Only if this condition is met, cavities or instabilities that form inside the liquid for whatever reason would start accumulating gas from their surroundings instead of collapsing immediately. Or looking at it from a slightly different angle, a vapor bubble in a liquid wouldn't be stable unless its internal pressure (the vapor pressure) is greater than the pressure of the surrounding liquid. If the total pressure is too high for bubbles to form inside the liquid, the only place where a phase change would occur is the surface of the liquid, where the vapor pressure of the substance might be able to overcome its partial pressure in the gas phase, or in other words evaporate. Since bubbles form at the bottom of a pot of boiling water and would still form if you covered the surface with a layer of oil for example, this explanation seems to fit the observations rather better. If my line of reasoning is correct so far, the question regarding vacuum exposure would be less whether a liquid is exposed or not, but rather whether it is enclosed by a membrane able to provide the necessary counterpressure. As mentioned, blood vessels are certainly able to do this but I have no idea how regular cell membranes would compare. Since you would at least expect some readily findable results of animal experiments if bloating was a real concern, my guess is that it probably doesn't happen. I would still consider it imaginable though at this stage.
  21. Copper seems most likely. Raptors apparently use quite a lot of it. It's also far easier to vaporize than tungsten.
  22. I was worrying about this point as well, but have a bit of a problem finding out why this would be the case. I'm of course aware of the Kittinger incident, but I'm not sure how much of the (apparently quite painful and debilitating) swelling was caused by the low pressure per se and how much was caused by the difference between the pressurized and unpressurized parts of the suit. After all, you can easily imagine body fluids accumulating in the only body part that's not pressurized. Source link [2] in your quoted passage mentions water in your tissues beginning to boil as a cause, which sounds plausible enough. While your blood may be protected by vessels designed to withstand the pressure differences of a beating heart, other liquids in your body might be not so lucky. Then again, the descriptions of pressure chamber accidents don't seem to mention this effect. Does it take a while to develop? I'd really love to find a good source.
  23. I'm a bit hazy on the subject, but doesn't "high humidity" just mean that the partial pressure of water vapor in the atmosphere is close to the vapor pressure of water for a given temperature? In other words, you'd have to have at least the Armstrong pressure in water vapor to achieve saturation, which means that below that pressure there's no such thing as "high humidity". On the other side, we probably wouldn't have to worry about adding water vapor to our breathing mix (in the loose sense) since our lungs would autogenously pressurize. If my math checks out, you would need as little as 50mg of water per litre of internal cavity to reach Armstrong pressure, which seems quite manageable. I guess, that's where a mask does come in handy. As has been established, all this would of course rely on finding another way to oxygenate your blood, since the oxygen partial pressure would be too low for your lungs to be much of a help.
  24. Why would a mask matter? Exposing your lungs to actual Martian atmosphere or to pure oxygen at Martian ambient pressure is - by definition - no difference pressure-wise. That said, I was less worried about your blood starting to boil and more about the drying-out of exposed lung tissues. I'm not quite sure how much this would actually impede the function of the lungs, but a complete evaporation of the water in your exposed mucous membranes would be very uncomfortable to say the least (especially if you take evaporation cooling into account).
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