Most efficient way to reach Low Kerbol Orbit

[Tigermisu]

Hey guys! I'm attempting to get a satellite as close to Kerbol as possible on a circular orbit but it is proving a nightmare to me.

So far I have a ship that somehow has 13k delta Vs left when in orbit, so what I did was to do a gravity assist in the moon that launches me to Kerbin's retrograde, then did a Hochmanns transfer to similar assist one in Eve, but it didnt go as well and I ended up having to burn 10k delta Vs retrogade and ending up in a low-ish orbit.

What's the proper day to do this?

Edited November 19, 2013 by Supernovy

[UmbralRaptor]

Uh...

You probably want a bi-elliptic transfer, rather than a Hohmann one. The Mun is all but useless for interplanetary gravity assists, and may have course corrections may have cost you more than you gained. Eve or Jool might work, but aren't strictly necessary and only save a few km/s. For circularizing, you're almost forced into using ions over the LV-N due to the 20+ km/s ÃŽâ€V requirement.

[Superfluous J]

You can't really get into low Kerbol orbit without expending a TON of Delta V.

The map I use suggests you need over 30k delta-V to actually get into low orbit around Kerbol, and there's no amount of trickery that will stop (most of) that. You can do whatever you want but at some point you're gonna have to BURN and BURN and BURN to lower your apoapsis down.

[Tigermisu]

ugh... I will have to spam xenon tanks then, thanks guys!

how do you tag the thread as answered?

Edited November 19, 2013 by Tigermisu

[Kasuha]

The best you can do to save dv is gravity assists off Eve and Moho. But they won't allow you to get the apoapsis below the planet's orbit and Moho is typically bad at providing gravity assists thanks to its low gravity (although when your speed is already low it might help a bit). Below Moho you're on your own dv.

Unless you use Planet Factory mod in which case you get Ablate, too.

[DrMonte]

One good thing - the near the sun, the better solar panels work. (If you'll use ion engines)

[KerbMav]

One good thing - the near the sun, the better solar panels work. (If you'll use ion engines)

See table here.

"Generated power will also decrease with increasing distance from Kerbol, but rather than following the real-life inverse-square law it experiences a spline curve of 3 piecewise cubics defined from 4 points:"

Do not know if this has been changed to a curve by now or if there are mods around doing this for the time being.

[numerobis]

The cheapest semi-practical way to low solar orbit is to go to Eve (~1 km/s), do a powered slingshot to boost your orbit to Jool (~500 m/s), use Jool to boost you to nearly solar escape; the higher the better, but beyond five orbits you don't have much less to win. At that very high aphelion, burn retrograde to sundive (~500 m/s). Total up to now: about 2 km/s.

Then you have ~25-27 km/s to kill in order to drop aphelion, and it's less easy to use gravity assists for that part. Still, this can all be done with nukes and some large staged tanks.

The burn times will be excruciating no matter what.

[UmbralRaptor]

Do not know if this has been changed to a curve by now or if there are mods around doing this for the time being.

They still use that weird 4 cubics system (at least in the part.cfg files). Mods for getting a proper inverse-square curve have existed in the past, though I'm not sure if there's anything current.

[Eadrom]

The interstellar plugin (KSPI) uses more realistic inverse-square law for solar power generation. You can get some truly massive power from solar panels in low Kerbol orbit with that addon. Just be sure to pack a couple radiators.

[Kasuha]

While four cubics may seem wrong, using pure inverse square law may be wrong as well. At certain irradiation the substrate becomes saturated and the production of electricity only converges to certain maximum value instead of groving over all limits. Also at very low irradiation you stop being able to extract any electricity at all.

[UmbralRaptor]

The thing is, the default curve diverges so far from the inverse square law so fast as to be all but unrelated. Providing adequate solar power out to Jool is trivial, as you get 50% effectiveness, rather than <4%. I'm less clear on the inwards curve, but should the panels saturate at 10x the Kerbin value?