Figuring out very long transfer burns.

[Requia]

I've got a very low thrust (45cm/s² so still better than real world, but low) nuclear-electric system I'd like to try to do some interplanetary travel with. I've figured out fairly efficient arrival on an earlier system (transferred with chemical arrived on plasma). I've figured out A way to do it, by spiralling out to 7000m so that the orbital period is long enough the burn is practical, but I wonder if anybody might know a more efficient way I can finagle such an interplanetary transfer (this one will take an extra ~1300 dv, which I have cause wheee plasma, but I figure there must be a better way). Time is a minimal concern I'm happy to let it run in the background, it's only if I need a ton of different burns with large time gaps between them things come up cause I know of no way to automate time warp).

(While I haven't yet messed with kOS I'm willing to do so to pull this off)

Edited August 30, 2015 by Requia

[JTpopcorn]

Unless you set up some modded autopilot system you will have to manually do the burns.

Remeber to quicksave!

[Starhawk]

Perhaps you may want to take a look at this thread.

Hope this helps.

Happy landings!

[Brainlord Mesomorph]

See the tutorial in my sig.

[Falkenherz]

Ok, I did not do any interplanetary transfer yet, I do not like the "precise-node" mod and want to use just stock maneuver node options, so let me see if I can translate and understood the tutorial from both links correctly (very helpful links, thanks a lot!);

- start 11,5 days before the transfer burn must happen (this is the time it takes to complete all "precomputed burns" ie. "perigree kicking burns" from the link to RedIronCrown´s tutorial)

- set a standard "one burn" maneuver node to destination planet

- eyeball a second maneuver node at ~10 radial degrees *after* the first one and use it for the "precomputed burns" from the link to RedIronCrown´s tutorial (this takes into account the different position Kerbin will have in relation to the target planet after 11 days)

- make sure orbital angle of the second node is aligned to your target planet the same way as with your first "one burn" node

- delete the first maneuver node and start the precomputed burns

- you have to manually again set up each of the precomputed burns after having executed the preceding one, at the same location (second node)

- check if at any point of the precomputed burns causes an unwanted intersect with Mün or Minmus (if yes, you need to miss a round and will have a not so optimal transfer anymore)

- final burn must never start more than 90 degrees radial orbital angle before the maneuver node; rather adapt course then later when in solar SOI

- may have to adapt orbital angle later in sun SOI because could not perfectly eyeball the shift in orbital angle resulting from the 10 degree orbital radial difference of the second node compared to the first one.

(I can do the same procedure if doing the Mangalyaan maneuver, the difference basically just is that it does not reach out so far as 31,930km, but only 900 km, and thus does not risk interference from either Mün or Minmus)

Would that work out?

Edited August 27, 2015 by Falkenherz

[Warzouz]

I successfully did some on these when transfering to Jool, Duna or Eve. But when I tried for Moho, I never found the encounter. So I changed my interplanetary stage to add huge chemical boosters to help the LVN. Success.

[Red Iron Crown]

Ok, I did not do any interplanetary transfer yet, I do not like the "precise-node" mod and want to use just stock maneuver node options, so let me see if I can translate and understood the tutorial from both links correctly (very helpful links, thanks a lot!);

*snip*

(I can do the same procedure if doing the Mangalyaan maneuver, the difference basically just is that it does not reach out so far as 31,930km, but only 900 km, and thus does not risk interference from either Mün or Minmus)

Would that work out?

That's not exactly how I do it (using my own precomputed burns), but if it works for you then that's great. My method (using PreciseNode or KER or any mod that shows node angle to prograde):

1. Set first maneuver node as close as possible to 11 days before the ideal window, with the correct offset ejection angle. (Angle is more important than time)

2. Complete the burn, ensuring that the semi-major axis is correct (i.e. the sum of Ap and Pe is the same as the computed Ap+Pe, this is critical for timing).

3. Set next maneuver node at periapsis.

4. Repeat steps 2 & 3 until all kicks are complete.

5. Set ejection node at periapsis.

6. Execute the ejection burn.

I successfully did some on these when transfering to Jool, Duna or Eve. But when I tried for Moho, I never found the encounter. So I changed my interplanetary stage to add huge chemical boosters to help the LVN. Success.

Burns toward an inferior planet (i.e. closer to the sun) are very time sensitive, and increasingly so with increasing difference between planetary orbits (try a Jool-Moho transfer sometime ). If I must do so with a low-TWR ship, I execute the ejection as planned and correct to get the encounter after exiting the first planet's SoI. Combining antiradial and prograde or radial and retrograde burn components can adjust your time of arrival, a useful method to get a tricky encounter or to refine one when you need to encounter a moon at the right place.

[Requia]

Thanks everyone