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UmbralRaptor

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  • About me
    Nihilopteryx
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    Outer Dark
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    Space, science, stabbing, the usual.

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  1. HARPS-N has a solar telescope, and regularly takes RV measurements of the sun. Somewhat infamously, you can see Jupiter in the data by eye, but it has yet to detect eg: Venus. But more generally, my response to trying to use it for distant planets is "lol, lmao". Weirdly enough, the period of a planet in our solar system isn't too important (so you don't need hundreds of years of data), but the sorts of distances would make the semi-amplitude (which scales roughly as mass/sqrt(distance)) negligible. Assuming my math is correct: Planet Semi-amplitude (m/s) Jupiter 12 Saturn 2.8 Uranus 0.30 Neptune (NEID is about here assuming no stellar activity) 0.28 Earth (goal for upcoming RV surveys) 0.09 Venus 0.085 Mars 0.078 10-Earths at 400 au 0.045 Mercury 0.008 Hence KBO/Oort cloud/Planet 9 surveys using direct imaging.
  2. My understanding on Starship vs SLS is on-paper no, but in practice Starship is likely to be rather more available / have fewer delays.
  3. The paper is open access: https://www.aanda.org/articles/aa/full_html/2022/02/aa42337-21/aa42337-21.html Nice to see that the EPRV systems are hitting target precisions. I think is is a pretty typical number for these spectrographs around M-dwarfs? It sounds in line with those CARMENES (plus some HARPS) planets. The rest of the data analysis (dealing with different offsets, gaussian processes for stellar activity, etc) sounds pretty typical. Please don't ask me about cross-correlation vs template matching. The hydrogen, helium, sodium, and calcium lines are all from the star, and are fed into the gaussian processes to make sure that stellar activity isn't causing a spurious planet detection, etc. No measurement of the planet's atmosphere has been done at this time, and actually doing so would likely be difficult: transiting is doubtful and direct imaging as out as the planet (at 22 marcsec) would be inside the inner working angle of a typical starshade mission.
  4. I'm vaguely reminded of EE Smith's shenanigans with spy rays, ultrawave stuff, etc. That his stories were in settings that mostly rejected GR (and sometimes SR) are probably also relevant to the FTL stuff.
  5. Nothing so fancy, just trying to use geometry to do some surveying of positions and RVs. (And I guess proper motion, given sufficient time. Precision is assumed to be faster/easier from the available propulsion systems) Depends wildly on details. My expectation given the above is that once you can get to one system, you can accurately map stuff out to at least 10s (and optimistically over 1000) ly. So given 300 years, most of the galaxy? Though the fact that getting to the core from here would take ~3 years probably matters somewhat. Yeah, presumably maps would get updates every so often. I don't know, there are all sorts of other questions of what technology is in this setting and what people want that haven't been answered. Does it work like a "normal" space opera in terms of interstellar trade?
  6. I mean, I was expecting intra-system movement to be sublight. And if I need a longer baseline to start doing interstellar flights, the automated ships can give me a 14 light-year one. Yeah, it'll take about a decade for them to come back and the data to be assembled, but after that...
  7. I see two complementary options: slower/more methodical targeted missions, and more wild fully automated ones 1) If you can reliably get *anywhere* (and α-Cen is more or less a given for this exercise), you can start doing long baseline measurements with crewed ships, and then chain off existing routes to new ones. If Wolf 359, Lalande 21185, Luhman 16, and/or WISE 0855−0714 is workable, so much the better. At some point, the expanding surveys should "run-away", and you'll get everything reasonably bright within thousands of light-years. 2) Send out some (4? 40,000? Depends on the tech/cost) automated craft in a more or less spherical pattern from an existing place, and have take data and fly back. A few of these succeeding should do wonders baseline stellar position/velocity information, though it's probably not needed if a few systems are already available.
  8. We have information on the 3D motions of a very large number of stars thanks to things like Hipparcos and Gaia, though presumably this drive would let one get outside of the range of existing surveys. I suspect that pointing precision would present a lot of problems since aside from red giants, stars are small (call the sun 1.2 μarcsec across at 7 ly). Hand-waving the aforementioned precision, an error in the sun's tangential velocity of 6.3 m/s will result in a 1 solar-diameter mismatch at the maximum distance, so doing a bunch of mapping before-hand is in order. If you can do a bunch of 7 ly jumps, you could get some pretty long baselines on apparent position/parallax, and with speed of light delay motion. Also if your spacecraft has a decent spectrograph, RVs from different directions. I'm under the impression that stuff in the 1 km/s relatively fast/cheap/easy, and 1-10 m/s is, while, non-trivial, something I can imagine a good survey ship could do just by extrapolating from existing 1-4 m telescopes with gas-cell spectrographs. Figure, jump, spend a day observing stars, jump. Repeat until you have a bunch of good survey data and go home.
  9. I can confirm that this is still broken (and needs the same workaround) in 1.12.3
  10. Okay, after reading a bit more of the report: All Great Observatories get R&D, though technically none are actually selected. IROUV (I'm going to insist on calling it this) is to be a flagship circa 2045, so hopefully that gives NGRST plenty of time. I guess I we can justify fancy ground based RV surveys to find a lot of planets/make direct imaging be more about characterization than detection in the interim. It's cool that it gets the highest priority, but seeing as the 2000 and 2010 highest priority telescopes are still on the ground... Both FIR and X-ray missions are supposed to get probe class craft, presumably one in 2030 and one in 2040. (Probe class being something in between Explorer and Flagship with a 1/decade cadence). I don't have a good handle on which previous missions are FIR. There are still a fair number of X-ray telescopes up, though they're all getting old. (Hitomi getting all of one science observation hurts) Some missions outside of NSF/NASA get mentioned (eg: VRO, Athena), and there's discussion of need for collaborations/data archives and curation. "mid-scale" ($4 million to $120 million) for various ground-based instruments with an emphasis on 4-10 m class. While not hugely specific, considerations of diversity, sustainability, and outreach are mentioned. GMT and TMT are supported as the highest priority ground based programs, though they waver a bit as to the TMT being in Hawaii or the Canary Islands. Various gravitational wave, CMB, radio, neutrino, and balloon projects. I'm a bad person to comment on these, and will defer to someone else. Recommend that SOFIA end operations in 2023 (ow). Solar physics is mentioned as important, though no specific programs are recommended for or against.
  11. JWST being JWST along with NGRST getting somewhat downs-coped to keep costs in line probably factor into IROUV's size and timeframe. I feel bad for the FIR and X-ray proposals, though. (Probably probe-class missions in 10 years.)
  12. It's a bug in version 1.12.2. You can work-around with the advanced part selection (select the arrow at the upper left corner of the parts menu). I'll suggest going to sort by tech level and then selecting tech level 2. Also linking an earlier thread where this problem occurred:
  13. It's just a visual thing, and might no longer accurately describe what those parts look like, given the various revamps that have happened since it appears to have been added (2013).
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