UmbralRaptor
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Posts posted by UmbralRaptor
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Because of design choices/limitations (see eg: no n-body, more limited mass ranges outside of the comets/asteroids, and lack of formation history), I'm unconvinced that it makes sense to apply IAU designations to attempt such a classification. Like, I'm unsure that there's enough consideration that Jool is a somewhat light Saturn orbited by what amount to 3 terrestrial planets. Or Gilly is in absolute terms more massive than Phobos.
Body Mass (kg) Mass (Earths) Body Mass (kg) Mass (Kerbins) Sun 1.99E+30 3.33E+05 Kerbol 1.76E+28 3.32E+05 Mercury 3.30E+23 5.53E-02 Moho 2.53E+21 4.77E-02 Venus 4.87E+24 8.15E-01 Eve 1.22E+23 2.31E+00 Gilly 1.24E+17 2.35E-06 Earth 5.97E+24 1.00E+00 Kerbin 5.29E+22 1.00E+00 Luna 7.35E+22 1.23E-02 Mun 9.76E+20 1.84E-02 Minmus 2.65E+19 5.00E-04 Mars 6.42E+23 1.07E-01 Duna 4.52E+21 8.53E-02 Phobos 1.07E+16 1.78E-09 Ike 2.78E+20 5.26E-03 Deimos 1.48E+15 2.47E-10 Ceres 9.38E+20 1.57E-04 Dres 3.22E+20 6.08E-03 Jupiter 1.90E+27 3.18E+02 Jool 4.23E+24 8.00E+01 Io 8.93E+22 1.50E-02 Laythe 2.94E+22 5.56E-01 Europa 4.80E+22 8.04E-03 Vall 3.11E+21 5.87E-02 Ganymede 1.48E+23 2.48E-02 Tylo 4.23E+22 8.00E-01 Callisto 1.08E+23 1.80E-02 Bop 3.73E+19 7.04E-04 Himalia 4.20E+18 7.03E-07 Pol 1.08E+19 2.04E-04 Saturn 5.68E+26 9.52E+01 Titan 1.35E+23 2.25E-02 Pluto 1.30E+22 2.18E-03 Eeloo 1.11E+21 2.11E-02 -
Or, I can think of 3 cases where this should be easy, but would like a tool to give me times/dates to launch to take advantage of them:
1) The off-plane intercept. Launch from KSC into ~0° orbit, and do a transfer to Minmus, timing things so that I meet up with it at an ascending or descending node. I know that Minmus has to be near the "top" or "bottom" of its orbit for this to work, and can fiddle around equations to work out ~how many degrees away from the nodes it has to be, but would like a way to get launch times in UT.
2) Launching into a 6° orbit. KSC crosses the nodes of Minmus' orbit twice each day, so I can launch on a 96° or 84° (ish) heading but I'd like a way that's not eyeballing things in map view.
3) Launching east from Dessert. Dessert launch site is ~6.5° south, so once a day, a launch just before crossing the ascending node should be very close to Minmus' plane. But this has the same timing problem as 2.
So... how? Can MechJeb or Kerbal Alarm Clock give me these times? Is there a table hidden away in the forums or reddit? A quick search was not the most promising.
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The Atlas V has nothing directly in common with the Atlas D. The Atlas V does use a Centaur which is a direct descendant of the ones used on slightly more recent Atlases, and the Centaur itself has some heritage in the design of the Atlas D's first stage tanks. Not sure how to count that.
I'm not sufficiently aware of the Ariane rocket family's history to comment much. I was going to say that there's nothing, but since both the Ariane I and Ariane 5 have hydrolox upper stages, there's a chance...
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Considering that the decadal survey shot down LUVOIR for cost reasons and ended up recommending something intermediate in size between HabEx and LUVOIR for the 2040s, I have doubts.
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20 hours ago, Spaceception said:
So this is really all in the title, but what limitations and challenges are there to using methods like radial velocity to find more planets in the solar system, like planet x, or other major bodies that might be far from the sun? I know radial velocity relies on the Doppler shift of a star's light, so are we too close for it to work? Or do hypothetical Oort cloud planets have too weak of a pull to really be noticeable? Either because of their extremely long orbits or comparatively small masses. What needs to change to make it feasible, and would it be worth our time - or would it make more sense in the end to continue observing as we always have, and simply send up more telescopes to cover the sky?
I was about to post this in questions that don't merit their own thread, but I figured this might.
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.
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4 minutes ago, Mitchz95 said:
Nice to see the ice giants getting some attention. Would Starship be able to reduce the Uranus Orbiter's travel time?
My understanding on Starship vs SLS is on-paper no, but in practice Starship is likely to be rather more available / have fewer delays.
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The paper is open access: https://www.aanda.org/articles/aa/full_html/2022/02/aa42337-21/aa42337-21.html
QuoteWe detect a signal at 5.12 ± 0.04 days with a semi-amplitude of 39 ± 7 cm s−1.
Nice to see that the EPRV systems are hitting target precisions.
QuoteTo add to the 67 observations reported in SM2020, we obtained 52 new ESPRESSO spectra of Proxima, for a total of 117 observations spread over 99 individual nights from 2019-02-10 to 2021-05-06.
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.
2 hours ago, kerbiloid said:Captured hydrogen and native sodium.
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.
QuoteTo trace the star’s activity, we extract a number of activity indicators from the ESPRESSO spectra or from the CCF. The DRS calculates the CCF’s full width at half maximum (FWHM), contrast (i.e. the relative depth of the CCF), and a shape indicator called CCF asymmetry (see Pepe et al. 2021). Using actin (Gomes da Silva et al. 2018), we also measure activity indices based on the CaII H&K, HeI, Hα, and NaI lines.
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.
QuoteWith the small stellar radius, Proxima d has a transit probability just above 2%. Its equilibrium temperature may reach 360 K, assuming a Bond albedo of 0.3 (e.g. Seager et al. 2010). From the planetary properties and stellar parameters, we can estimate a planetary radius of 0.81 ± 0.08 R⊙ using the random forest model from Ulmer-Moll et al. (2019), leading to a transit depth of about 0.3% (approximately half that of Proxima b; Anglada-Escudé et al. 2016). A transit detection would allow a precise measurement of the planetary radius and could place constraints on the planet bulk density and possible atmosphere. However, a transit is unlikely given that Proxima b has not been found to transit (see Jenkins et al. 2019, and references therein) and that transit events at periods below 5 days and depths above 3 mmag have been ruled out (Feliz et al. 2019; Vida et al. 2019).
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15 hours ago, Spacescifi said:
UV Teleportals: Ultra-violet rays (short wave invisible rays) can be shot between teleportals aboard ships in real-time no matter the distance.
The effect is that now ships have a kind of real-time instant messaging via UV rays.
Such tech has not made the swarm telescopes obsolete, but it does make going boldly where no man has gone before with less infrastructure a bit more viable.
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.
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On 1/10/2022 at 3:02 AM, KSK said:
But in any case, I think (and please correct me if I'm wrong) that @UmbralRaptoris talking about using the automated ships to set up an astronomical interferometer.
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)
On 1/9/2022 at 7:29 PM, Spacescifi said:The setting will be 300 years after the development of star mapping by hyperdrive.
[snip]
What is an optimistic bubble radius of LY mapped from home system, and what would one where they ran into problems look like?
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.
On 1/10/2022 at 4:34 AM, KSK said:Well I wouldn’t expect obtaining navigation data to be a one-and-done exercise. I don’t know how far into the future one can reliably predict stellar positions but I’m not sure I’d be comfortable making a hyper jump on the basis of centuries old data. I would think those 300 year old relics would still be in use.
Yeah, presumably maps would get updates every so often.
On 1/10/2022 at 4:03 AM, Spacescifi said:[Extremely ambiguous world-building]
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?
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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...
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26 minutes ago, Spacescifi said:
Thanks... but I forgot to mention why going 7 LY would strand you.
The hyperdrive is powered by grav-batteries, batteries that literally charge off planetary or stellar gravitational fields.
A field of 1g would recharge the battery at a rate of 1 LY per hour, but you have to get within low orbit of a 1g world to get it. Lower than 1g has a longer charge time, higher shortens it.
When you hyperdrive 7 LY you totally drain your battery, which means hopefully you bounced off a star or planet because that's the ONLY way one will be nearby to recharge your hyperdrive.
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.
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10 hours ago, Spacescifi said:
But barring that... is there any realistic way to reliably aim for the next star over?
Like take Earth for example? We should know EXACTLY where Proxima Centauri is given how long we have neen watching it, and getting back to Earth would be eady since we would have Earth's sun's orbital path already in our navigation computer.
Yet from Alpha Centauri onward it starts to get harder. Could we aim for reliably in reasonable amount of time? I am willing to allow weeks to a month at most to reliably calculate the position of the next star to aim for at most.
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.
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I can confirm that this is still broken (and needs the same workaround) in 1.12.3
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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.
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18 hours ago, NFUN said:
considering the JWST, I can't say I blame them for being skeptical of the feasibility for such an ambitious telescope, at least to be finished anywhere remotely near budget and deadline. We'll see if Starship can change the math on that by the end of the decade
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.)
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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:
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19 hours ago, HebaruSan said:
They may be waiting for a response showing that someone is there before asking their real question. IRC doesn't make it easy to tell whether everyone is idle.
I guess, but putting an extra barrier to asking their question still seems silly.
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We can't do anything if you don't contribute
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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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Sorting by manufacturer (Jeb's) does appear to work, as does sorting by tech level (2).
And yes, the advanced construction training mission is bugged since you don't get an LV-T45 in the obvious place.
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1 hour ago, jinnantonix said:
Hi all,
A question for those good at calculating orbital mechanics.
NASA advise that the following is the schedule for the transit to Jupiter:
- launch in October 2024 - 21-day launch window.
- Mars in February 2025
- Earth in December 2026,
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arriving at Europa in April 2030.
So 50 days from LEO to Mars? And then 1 year and 9 months back to Earth?
It should end up being rather longer on the outbound leg, since November+December+January+February is 122 days, but might be worth messing with GMAT or something for exact trajectories.
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I want to say that number of stages is not amenable to an analytic solution, so you need to iterate over a few designs. For a two (or I suspect N) stage design you can figure out the optimal fuel distribution with some constraints.
There are some somewhat messy formulae in the stage sizing link in my signature that are hopefully related. (In general you want larger mass ratios in the high Isp stages, but can easily hit TWR limits)
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1 hour ago, JoeSchmuckatelli said:
Can you do jumps like this to 18 Sco?
Not without a lot more effort.
- I'd need a catalog with parallaxes that's complete out to 15 or 20 pc (possibly some sort of combination of several -- there are a fair number of stars that aren't in Hipparcos or Gaia)
- There are enough jumps that I'd probably want some sort of algorithmic approach instead of throwing this into Excel and manually noting the distances less than ~7 light-years.
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1 hour ago, Spacescifi said:
A casual google search reveals that average distance between stars is between 4-5 LY in the Milky Way, but is less toward the center.
Things may be better connected than I thought, though there's a possibility of winding paths and limited hubs. After fiddling a bit with the data in a 10 pc catalog, I get the following:
Sol with Alpha Centauri, Barnard's Star, and Luhman 16 (brown dwarf)
Alpha Centauri with Sol, Barnard's Star, and Luhman 16 (brown dwarf)
Barnard's star with Sol, Alpha Centauri, Luhman 16 (brown dwarf), WISE J085510.74-071442.5 (brown dwarf), Wolf 359, Lalande 21185, Sirius, UV Ceti, Ross 154, Epsilon Eridani, HD 217987, Ross 128, EZ Aquarii, Procyon, Tau Ceti, YZ Ceti, and Luyten's Star
Luhman 16 with Sol, Alpha Centauri, Barnard's Star, WISE J085510.74-071442.5 (brown dwarf), Sirius, Ross 248, 61 Cyg, Goombridge 34, Kruger 60, and maybe DENIS J104814.6-395606
The nearest stars that are going to take actual effort to find a route to are Struve 2398, DX Cancri, and Epsilon Indi.
Aircraft Losing Velocity At Higher Altitudes
in KSP1 Gameplay Questions and Tutorials
Posted
Honestly, it seems like a reasonable design for what it is. The primary flaw is that it's arguably overweight/has so much fuel, so unless you want to go a very long ways in-atmo, you should drop a tank or two from the design. Other lightening can be done by draining the cockpit of monopropellant, though that doesn't matter much. I'm also partial to disabling the reaction wheels by default to give a more aircraft-like feel (especially with your rather well-defined control surface choices)
Note that for completing high altitude contracts, a common trick is to bring some rocket engines along so an aircraft can (briefly) get much higher.