Timeline for Energy to "nudge" a planet to a smaller orbit
Current License: CC BY-SA 4.0
8 events
when toggle format | what | by | license | comment | |
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Aug 16, 2021 at 13:14 | comment | added | PM 2Ring | @J.G. Right. The vis-viva relation means that GPE gets converted into KE, which you then need to get rid of when you reach your destination. OTOH, you can save some energy if you don't mind ending up in an eccentric orbit. | |
Aug 16, 2021 at 12:55 | vote | accept | J.G. | ||
Aug 16, 2021 at 12:55 | comment | added | J.G. | OK. It looks like there's no way to turn lost GPE into angular-momentum KE to make a significant "nudging" saving. | |
Aug 16, 2021 at 12:52 | comment | added | PM 2Ring | I guess I should also to mention en.wikipedia.org/wiki/Delta-v#Delta-v_budgets "It is not possible to determine delta-v requirements from conservation of energy by considering only the total energy of the vehicle in the initial and final orbits since energy is carried away in the exhaust" | |
Aug 16, 2021 at 12:46 | comment | added | PM 2Ring | @J.G. Mine's a little smaller. ;) SE's $GMmr_i^{-1}/2$ is just the negative of the specific orbital energy of Earth, times $m$, the payload mass. My table gives that as ~443 million joules/kg. But we can reduce that by Neptune's $-\epsilon$ of ~14.7 MJ/kg to get the actual specific energy required, which is ~428.8 MJ/kg. (You get the same number if you add up the absolute values of the specific kinetic energy changes at the two burns). Sorry, I should've included that subtraction in my program & table. I'll update it tomorrow. | |
Aug 16, 2021 at 10:58 | comment | added | J.G. | How does this compare with the expense estimate in the other answer? | |
Aug 16, 2021 at 6:17 | history | edited | PM 2Ring | CC BY-SA 4.0 |
added 8 characters in body
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Aug 16, 2021 at 6:11 | history | answered | PM 2Ring | CC BY-SA 4.0 |