Need Help on Efficient Duna Planet Transfer...

[Kilo_60]

Everytime I wait for Duna to be in the correct orbital position to Kerbin (1:30 Duna 3'oclock Kerbin) and launch, it still takes about a year's time and halfway throough Dunas orbit around the Sun before I get to the planetand tons of wasted fuel...

Shouldn't it only take about 6 mos if I lauch at the correct window?

Also, MechJeb seems to want to spaz out at times and wait another year to do the transfer. Or worse keeps giving me Errors or messages when trying to let it plot a Hormann Transfer. Says not in SOI of Duna or not in circular orbit or not on same inclination although I do a burn and get to 0 inclination just before... Any other planet transfer via MechJeb puts me horrably out in Duna's Perapsis and I have to retro burn like a madman not to escape...

What do I need to do to get an efficient fuel and time wise manual transfer to Duna and what the heck do I have to do to coax MechJeb to do it automatically?

Thanks!

[Vernibob]

Hey dude,

Too be honest im no expert but i have been duna a few times but i never EVER used mech jeb.

what i do is use KErbal Alarm clock to give me "windows" at first i would take off just before the window in a high orbit. Normally if i had time and thought it was nessearry i would send up a pilotless rocket to refuel whilst it was up there, just as a top up an then i planed my transfer manually. Just sat and plade with the nodes for about 10 15 minutes.

since then i have made a little space station around Mun, that basically is a flying fuel tank (if your not using mods yes you have to fill it up). but once its full and you can lunch your craft to mun, re fuel and then plan it manually again. uses a bit less fuel.

I know its not using mechjeb but it is another way around the issue.

[invision2212]

http://steamcommunity.com/sharedfiles/filedetails/?id=1103965370

http://steamcommunity.com/sharedfiles/filedetails/?id=1103968757

[Jupiter3927]

It only takes about 2.5km of dV to get to Duna and another 2.5km to get back without any gravity or aerobraking assists.
Your transfer window for Duna is about 45 degrees ahead of Kerbin.
Make sure you set Duna as your target so you'll get close aproach markers.
It will always take more than half a year Kerbin time and less than half a year Duna time to do the cheapest transfers.

Once you get to Duna, you can get anywhere since all the planets follow the same transfer physics.

If you want to practice transfering but don't want to wait forever, you can try going from the Mun to Minmus and back.
It has the same concepts as interplanetary travel but it's all in the Kerbin system.

[GeneralVeers]

Originally posted by Kilo_60:

What do I need to do to get an efficient fuel and time wise manual transfer to Duna

Usually it's a tradeoff. A more fuel-efficient transfer will take longer.

The only exception I know of is a slingshot maneuver. If your mission to Duna starts from Minmus (and gets its fuel tanks topped off by a tanker ship) with Minmus ahead of Kerbin and inside Kerbin's orbit, you can escape Minmus retrograde, skydive to 71km periapsis above Kerbin, fire your transfer burn at that periapsis, and intercept Duna for a grand total of 350 delta-V.

(that does include the delta-V you use to escape Minmus and do the skydive)

[maj.solo]

There are no tricks.
You want to spend least fuel you have to pay with time.
You want to save time you need to pay with fuel.

If this was not true you could go to Mars at any date.

If Duna is ahead of kerbin you go more inwards toward the sun ( cost fuel ) to cut inside Dunas circle. When you arrive at Duna your orbit will be more eliptical so to get cospeed with Duna cost more fuel then if you used the launch window.

If Duna is behind then just forget it. You will be paying in both fuel and time when the kerbals could have played pool in the astronaut complex. To not pay with time but save time your craft have to be lobbed outside Dunas orbit.

Just check first paragraph, I belive it is true always.

I do fire when not in launch window but I think it cost a lot of fuel. I think the fuel cost for inter planetary missions is high as it is even if you use a launch window.

[Jupiter3927]

I do all my interplanetary burns from high Kerbin orbit between the Mun and Minmus so my numbers are going to be really high.
It makes it a lot easier to plan manuevers from that altitude.

[Kilo_60]

Alrighty, Thanks!