Timeline for Time dilation on a heavily oblong planet
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 10 at 12:20 | comment | added | Syndic | @ChristopherJamesHuff Ah, I misread that part, my bad. Teaches me to read more thoroughly! | |
| Apr 10 at 11:50 | comment | added | Christopher James Huff | @Syndic only in that the orbital velocity and surface gravity are both functions of mass and distance from the center. And I specifically stated that orbital velocity was the main problem. | |
| Apr 10 at 5:26 | comment | added | Syndic | @ChristopherJamesHuff please correct me if I'm mistaken, but doesn't higher gravity of the planet mean higher orbital velocity, meaning more delta-v required to reach that orbital velocity, and thus more fuel required too? And at that point the rocket equation would apply? | |
| Apr 8 at 12:29 | comment | added | Christopher James Huff | @Syndic the rocket equation doesn't say anything about acceleration, it relates delta-v, mass ratio, and specific impulse. Increasing the acceleration decreases the required delta-v because gravity losses are reduced. Any increase in mass is due to the increased structural requirements or because you had to use a lower performance rocket to achieve the needed thrust, neither of which have anything to do with the rocket equation. | |
| Apr 8 at 7:41 | comment | added | ErikHall | I dont think frame dragging is significant here for these types of measurements. Mesklin is huge and having worked with the Kerr Metric, it seems questionable that this effect would be relevant outside of years long observations. | |
| Apr 8 at 6:34 | comment | added | Syndic | @ChristopherJamesHuff without looking up how to do the math, I assume the main issue with the 3g and lifting stuff off the planet would be the tyranny of the rocket equation. Currently, we can reach orbit with a rocket the size of... the rockets we know. At 3g, the rocket wouldn't have to be three times as big but much, much bigger - which might either be incredibly expensive to build and fuel, or impossible if the materials needed to build and control rockets that big are not available. | |
| Apr 8 at 2:43 | comment | added | Christopher James Huff | I also doubt the Lense-Thirring effect will be significant compared to the precession caused by the planet's equatorial bulge. This is very, very far short of the conditions around a black hole or neutron star where such effects become important...a millisecond pulsar is nearly 1500 Jupiter masses, is about 20 km across, and rotates nearly a thousand times per second, and black holes are even more extreme. Meanwhile, even Earth's tidal bulge is enough to allow sun-synchronous orbits that precess once a year by purely Newtonian effects. | |
| Apr 8 at 2:39 | comment | added | Christopher James Huff | "3 g of surface gravity makes it virtually impossible for modern-day chemical rockets to lift stuff off the planet": rockets can accelerate at hundreds of gravities. It's not the surface gravity that's the problem, it's the orbital velocity you need to reach...somewhere around 100 km/s. | |
| Apr 8 at 2:31 | comment | added | Loren Pechtel | And why should 700g preclude any human probes? We can certainly build things to stand up to 700g--that's far, far below gun-rated stuff and we were putting electronics in shells in WWII. | |
| Apr 8 at 2:08 | comment | added | controlgroup | Of course you're right, precise navigation systems have to deal with time dilation, but we're also dealing with launching satellites into stable orbits from 3 gs at the ground; while it's certainly going to be an issue the bigger issue would be how to stabilize the satellite orbits. | |
| Apr 8 at 1:25 | comment | added | Swift | for humans 60 milliseconds per day doesn't matter. For computer networks, or precise navigation it does. Albeit if they could reach Mesklin, land and even take off from it, they likely had ways to deal with issues. And yeah, whole "Mission"was because there was no comms with errouneously landed probe. Currecntly our IT have problems with Moon's 58 microseconds, they need updated protocols :P | |
| Apr 8 at 1:22 | comment | added | Swift | I think, much later he published corrected gravity values (and other model parameters). Someone helped him with calculation or he had access to a computer. Yeah, with anything non-spherical the shell therem stops working, even for Earth it doesn't work perfectly - "shells" start appear in 80-100 km above surface - but today we have methods of integrations Newton couldn't use. | |
| Apr 8 at 1:18 | vote | accept | Swift | ||
| Apr 7 at 23:21 | history | answered | controlgroup | CC BY-SA 4.0 |