Timeline for Why would a slow spiral from a C3 of zero take about 2.4 times as much ΔV as an impulsive maneuver?
Current License: CC BY-SA 4.0
11 events
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| Aug 7, 2018 at 17:06 | history | edited | Mark Adler | CC BY-SA 4.0 |
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| Jul 14, 2018 at 2:47 | vote | accept | uhoh | ||
| Jul 12, 2018 at 18:59 | comment | added | Mark Adler | This discussion about getting to escape, in which case all that matters is the final C3. | |
| Jul 12, 2018 at 18:27 | comment | added | Bob Jacobsen | There's more to the difference between "spiral to height H in a close-to-circle" and "reach H with an extremely elliptical orbit" than just Oberth-effect-at-different-altitudes because the two cases result in different energy final states: The 1st has a higher speed at H compared to the second. | |
| Jul 12, 2018 at 15:46 | comment | added | Loren Pechtel | @MarkAdler Yeah, if your probe didn't die before the burn was done. | |
| Jul 12, 2018 at 14:41 | comment | added | Mark Adler | @LorenPechtel You do the with ion engine. It's just that you chose to spiral out, so you are raising your radius throughout the maneuver, reducing the Oberth effect. You could choose to only operate your ion engine at only one point in the orbit, which becomes the periapsis, and leave it off the rest of the time. Depending on how short your firings are at periapsis, you will get all the same Oberth goodness. However it will take a really long time to escape. | |
| Jul 12, 2018 at 14:07 | comment | added | Loren Pechtel | And a simple explanation for why: When you burn a big rocket you do it low and get a big benefit from the Oberth effect. With an ion engine you don't. | |
| Jul 12, 2018 at 4:34 | comment | added | uhoh | I've just asked Spiraling out from circular orbit to escape via low thrust, what is γ and why would it be 31° at the end? | |
| Jul 12, 2018 at 4:23 | comment | added | uhoh | excellent, bingo, perfect, etc. I remember now what you explained there. Paraphrasing; if you are moving at a speed v in a circular orbit, then in the limit of very weak prograde propulsion, a delta v equal to that v will get you to infinity. | |
| Jul 12, 2018 at 3:58 | history | edited | Mark Adler | CC BY-SA 4.0 |
reference other answer
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| Jul 12, 2018 at 3:08 | history | answered | Mark Adler | CC BY-SA 4.0 |