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Everything posted by metaphor

  1. In case anyone wants to replicate the newly "discovered" Planet Nine, in your RSSKopernicus.cfg file copy the entry for Neptune and replace the start of it with the following (you can change the name): name = Persephone finalizeOrbit = true Template { name = Jool } Orbit { // Target body name: // Center body name: Sun (10) // Center-site name: BODY CENTER referenceBody = Sun semiMajorAxis = 75900000000000 eccentricity = 0.58 inclination = 20 meanAnomalyAtEpochD = 148 longitudeOfAscendingNode = 100 argumentOfPeriapsis = 151 color = 0.19215, 0.33333, 0.56862, 1.0 } Properties { description = Discovered through its gravitational effect on the farthest bodies in the solar system, Persephone is slightly smaller than Uranus and Neptune. radius = 21000000 // adjusted below average to approximate height where pressure approaches 1000 Bar mass = 6E+25 rotationPeriod = 36000 tidallyLocked = false initialRotation = 0 isHomeWorld = false timewarpAltitudeLimits = 0 5000 30000 30000 100000 300000 600000 1000000 // FIXME add biomes ScienceValues { flyingAltitudeThreshold = 191000 spaceAltitudeThreshold = 3000000 } }
  2. Yeah, that happens sometimes. If you want to fix it, put a maneuver node down on the orbit after the encounter. This will force the game to compute the next orbit and should show you the second encounter.
  3. Giving a range is a good idea. Here's some new charts with a range of values:
  4. The mass of the real NERVA was about 6.8 tons, for a vacuum thrust of 333 kN and Isp of 850 s. There were also other nuclear engines in planning, like the SNTP (Space Nuclear Thermal Propulsion) program, which had an engine with a mass of about 1.6 tons, a thrust of about 120 kN, and an Isp of 930-1000 s. More info
  5. I just got a lander very similar to yours into 60 km orbit for about 1550 m/s from 2700m altitude. But you're right, the atmosphere of Duna is very thick now for small unaerodynamic craft, a lot thicker than in 0.90, even at 30 km altitude. edit: with the 1.0 aerodynamics it took about 1380 m/s to get into 60 km orbit with the same lander.
  6. Drag losses can be very different between large, thin rockets and small, fat rockets. Drag force is proportional to the surface area that goes into the windstream. The acceleration due to drag (i.e. delta-v losses) is drag force divided by mass. For example, a 1.25m ship will have twice as much drag losses as a 2.5m ship that has the same shape but scaled up.
  7. Yep. For ascent from atmospheric bodies, I just tried some ascents experimentally to come up with delta-v values. It depends a lot on the size and shape of your rocket (and on the heat tolerance of your parts), even assuming that you fly the perfect gravity turn. Orbital maneuvers in vacuum can be calculated, atmospheric maneuvers not so much.
  8. You can capture propulsively into Eve orbit for less than 200 m/s usually. (how to get to Gilly easily) Capturing at Jool also takes about 200 m/s or less, or can also be done for free by a gravity assist from Tylo or Laythe. Aerocapture is not performed in real life because it's usually just not worth it. The heat shield needed has similar mass to the amount of propellant needed for propulsive capture. It's only really worth it for missions to Uranus or Neptune or Titan orbit, it's borderline for missions to Mars, and counterproductive for missions to Jupiter, Saturn, or Venus.
  9. Mouse over it in map view. The maneuver has to be deselected (not have the colored handles showing).
  10. Yep, the turbojets have a significantly higher TWR than the rapiers off the pad, and they're not too bad at the higher speeds either. I also tried with a poodle upper stage, but it needed higher TWR to counteract the still-significant atmospheric drag.
  11. Aerospikes are the only engines with a nonzero Isp at 0 altitude on Jool. They have an Isp of 65 s there. That means their thrust is about 80 kN, so they can barely carry a small tank of fuel by themselves. I tried making a 900-part aerospike asparagus ship, but only got to about 5 km altitude on Jool. It's way harder than it was pre-1.0. Maybe the challenge should be how low can you go inside Jool's atmosphere and still make it back into orbit.
  12. Here's mine, updated some numbers for 1.0.2: And a more simplified version: An important disclaimer is that ascent delta-v varies significantly based on the size and shape of your rocket. Edit: changed maps to provide a range
  13. Here's one with 50.23% payload fraction (58650/116770), 8 rapiers and 4 turbojets on the first stage, 1 skipper on the second stage:
  14. Yeah, in fact as you get closer to the Sun below ~1,000,000 km the efficiency of solar panels actually goes down.
  15. The Skipper doesn't actually activate until all the aerospike stacks are depleted. There aren't any fuel lines on the ship. Here's a video:
  16. Here's a simple single stage rocket with 22.7% payload fraction:
  17. This ship can get to orbit from Eve sea level. It has about 8500 m/s of vacuum delta-v. Still have to find a way to land it...
  18. From a technical standpoint, the hard part was getting into orbit around a comet, which Rosetta was the first spacecraft to do.
  19. If anyone wants a heightmap for comet 67P for a Rosetta mission in RSS, there's some in this thread. It looks something like this when used on Gilly: This is part of my Rosetta mission I just put together quick and dirty before the landing tomorrow. Planning on doing the launch and gravity assists etc when I have more time.
  20. Because tidal forces are proportional to 1/R^3 while gravitational forces are proportional to 1/R^2, so closer objects will experience more tidal force compared to gravitational force. Tidal acceleration is dr*2GM/R^3. The tidal acceleration of the Sun acting on the Moon is about 1.3e-7 m/s^2, while the tidal acceleration of the Earth acting on the Moon is about 2.5e-5 m/s^2. The gravitational acceleration due to the Sun is 5.9e-3 m/s^2, and the gravitational acceleration due to the Earth is 2.8e-3 m/s^2. It's not really like Janus and Epimetheus since those two are on opposite sides of their Saturn orbit most of the time.
  21. So from the data I've looked at there are really two families of moons. The moons in prograde circular orbits that start out small near the planet and get bigger up to a point, and the (usually) retrograde irregular orbit moons that are much smaller and farther away. There is a large gap without moons between these two regions. The prograde closer moons probably formed together with the planet, while the irregular outer moons probably were probably captured. Jupiter's moons. The outermost regular moon, Callisto, is at 1.9 Gm, while the innermost irregular moon, Themisto, is at 7.5 Gm. Saturn's moons. The outermost regular moon, Iapetus, is at 3.6 Gm, while the innermost irregular moon, Kiviuq, is at 11.1 Gm. Uranus's moons. The outermost regular moon, Oberon, is at 0.6 Gm, while the innermost irregular moon, Francisco, is at 4.3 Gm. Neptune's moons. Neptune has Triton, which is retrograde and probably captured, but still in a circular orbit close to equatorial, at 0.4 Gm, while the innermost irregular moon, Nereid, is at 5.5 Gm. It seems like planetary moons have this kind of size distribution:
  22. Yeah, the rocket would only need to have about 4 km/s of delta-v to get into Mars orbit, which is very possible to do single-stage. The MSR proposals I've seen have a total payload to the surface of about the same size as Curiosity or a little bigger. The ascent rocket would be only a few hundred kg, with a ~1 kg sample onboard (that's without ISRU since it's not really needed with such a small rocket).
  23. That's true for big rockets, but for smaller rockets the air seems thicker. The rocket gets smaller, but the size of the incoming air molecules stays the same. Smaller rockets have higher surface area-to-mass ratios, and so have a higher drag. That's why as you go down in rocket size, a rocket's payload mass ratio gets smaller (the Saturn V was one of the most efficient rockets with respect to payload mass ratio). A rocket the size of a person would have too much drag to get into orbit.
  24. It's a measure of how long it takes a body to clear its orbit, and is based on easily measurable parameters (mass and orbital radius). For moons it doesn't really work well since there's other important forces that determine a moon's orbit, like solar tides. We're trying to see if there's a good way to subdivide natural satellites into classes instead of lumping them all together (which I guess is what you mean by hierarchy option?).
  25. Hmm, the equation for the Stern-Levison parameter is L = M^2/a^(3/2)*k, where M is mass and a is semi-major axis, and k is a constant. It seems that if you express mass in Earth masses and semi-major axis in AU, k is about 1.5e5. Applying that to moons, and dividing by the square root of mass of the primary compared to the mass of the Sun, you would get something like this: [table=width: 500] [tr] [td]Satellite[/td] [td]Stern-Levison parameter[/td] [/tr] [tr] [td]Moon[/td] [td]3.0e2[/td] [/tr] [tr] [td]Phobos[/td] [td]5.5e-10[/td] [/tr] [tr] [td]Deimos[/td] [td]2.7e-12[/td] [/tr] [tr] [td]Metis[/td] [td]6.7e-9[/td] [/tr] [tr] [td]Amalthea[/td] [td]1.3e-5[/td] [/tr] [tr] [td]Io[/td] [td]6.9e3[/td] [/tr] [tr] [td]Callisto[/td] [td]1.1e3[/td] [/tr] [tr] [td]Himalia[/td] [td]1.1e-7[/td] [/tr] [tr] [td]Sinope[/td] [td]1.2e-11[/td] [/tr] [tr] [td]Pan[/td] [td]6.6e-11[/td] [/tr] [tr] [td]Mimas[/td] [td]2.3e-3[/td] [/tr] [tr] [td]Enceladus[/td] [td]1.3e-2[/td] [/tr] [tr] [td]Tethys[/td] [td]3.1e-1[/td] [/tr] [tr] [td]Dione[/td] [td]6.7e-1[/td] [/tr] [tr] [td]Rhea[/td] [td]1.8e0[/td] [/tr] [tr] [td]Titan[/td] [td]1.7e3[/td] [/tr] [tr] [td]Iapetus[/td] [td]6.3e-2[/td] [/tr] [tr] [td]Phoebe[/td] [td]1.9e-7[/td] [/tr] [tr] [td]Puck[/td] [td]1.7e-5[/td] [/tr] [tr] [td]Miranda[/td] [td]4.8e-3[/td] [/tr] [tr] [td]Ariel[/td] [td]1.1e0[/td] [/tr] [tr] [td]Umbriel[/td] [td]5.1e-1[/td] [/tr] [tr] [td]Titania[/td] [td]2.2e0[/td] [/tr] [tr] [td]Oberon[/td] [td]1.0e0[/td] [/tr] [tr] [td]Proteus[/td] [td]2.6e-3[/td] [/tr] [tr] [td]Triton[/td] [td]1.2e2[/td] [/tr] [tr] [td]Nereid[/td] [td]4.1e-6[/td] [/tr] [tr] [td]Charon[/td] [td]6.0e-1[/td] [/tr] [tr] [td]Hydra[/td] [td]6.6e-9[/td] [/tr] [tr] [td]Hi'iaka[/td] [td]9.9e-6[/td] [/tr] [tr] [td]Dysnomia[/td] [td]1.7e-2[/td] [/tr] [/table] Here's a graph: The yellow line is where the Stern-Levison parameter equals 1 with respect to the Sun. Moons are all on the top of the black line. There should be a lot more moons to the left of the yellow line, but I didn't graph the smaller ones.
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