Impossible transfer?

[Jas1126]

Hello, I'm attempting to transfer from Eeloo to Jool but after an hour and a half of testing positions (via node tweaking and time warping) I haven't come across anything viable. I activated the MechJeb mod to see if it could find anything and it just wants to send me on an escape course of the entire solar system.. Is such a transfer possible at all?

Thanks.

Edited May 15, 2014 by Jas1126

[Dhan]

You need to transfer when the planets are aligned in the proper phase angle. I'd suggest the mod Kerbal alarm clock to help you in figuring out when the correct time to transfer is.

[Jas1126]

You need to transfer when the planets are aligned in the proper phase angle. I'd suggest the mod Kerbal alarm clock to help you in figuring out when the correct time to transfer is.

That's what I had thought as well until I saw even MechJeb fail at doing so (seriously, the path it wanted to take was absolutely absurd). Unless the mod wasn't programmed to handle the transfer then I don't know what's up. I'll try the alarm clock. Thanks.

[AlexinTokyo]

The ever excellent Launch Window Planner for KSP says that the following is the optimal transfer.

Selected transfer details

Departure:      Year 31, day 158 at 0:14:24
Arrival:        Year 40, day 244 at 2:48:00
Time of flight: 9 years 86 days 2:33:36

All in Kerbal, not Earth, time.

If you're already after year 31, then you'll need to use the advanced settings on the planner to find your optimal transfer.

[Jas1126]

The ever excellent Launch Window Planner for KSP says that the following is the optimal transfer.

Selected transfer details

Departure:      Year 31, day 158 at 0:14:24
Arrival:        Year 40, day 244 at 2:48:00
Time of flight: 9 years 86 days 2:33:36

All in Kerbal, not Earth, time.

If you're already after year 31, then you'll need to use the advanced settings on the planner to find your optimal transfer.

I'm at year 14. It's going to be a long wait. lol I think I'm just better off heading to Duna first and then heading off to Jool. Well, At least I know it's possible. Thanks.

[Sean Mirrsen]

Why settle for optimal transfer when you can do better and sooner, just with more dV?

Try a straight transfer and see whether you end up ahead or behind of Jool. If you're ahead, half-Hohmann to a (much) higher orbit, pick a fitting point, then transfer back to Jool. If you're behind, do the opposite - drop below Jool orbit, then come back up. It's doable, it just takes more fuel and more time in flight - but less time waiting.

[Jas1126]

Why settle for optimal transfer when you can do better and sooner, just with more dV?

Try a straight transfer and see whether you end up ahead or behind of Jool. If you're ahead, half-Hohmann to a (much) higher orbit, pick a fitting point, then transfer back to Jool. If you're behind, do the opposite - drop below Jool orbit, then come back up. It's doable, it just takes more fuel and more time in flight - but less time waiting.

All too true but I was just curious if a straight transfer from planet to planet was possible. Less hassle and fuel. But, that wait time is very unappealing. Besides, I'm already sitting on Ike grabbing some Kethane. XD

[DeMatt]

The ever excellent Launch Window Planner for KSP says that the following is the optimal transfer.

Selected transfer details

Departure:      Year 31, day 158 at 0:14:24
Arrival:        Year 40, day 244 at 2:48:00
Time of flight: 9 years 86 days 2:33:36

All in Kerbal, not Earth, time.

If you're already after year 31, then you'll need to use the advanced settings on the planner to find your optimal transfer.

I'm at year 14. It's going to be a long wait. lol I think I'm just better off heading to Duna first and then heading off to Jool. Well, At least I know it's possible. Thanks.

It's worth noting that the Launch Window Planner goes for the UTTER PRECISELY TOTAL OPTIMAL solution when it picks one. In this case, that means the 3083 m/s transfer listed above. If you're willing to spend a mere 1000 m/s more, then you can get an earlier - and quicker! - transfer:

Selected transfer details

Departure:      Year 14, day 49 at 2:43:12
Arrival:        Year 21, day 205 at 4:48:00
Time of flight: 7 years 156 days 2:04:48
Total ÃŽâ€v:       3,919 m/s

Selected transfer details

Departure:      Year 17, day 273 at 3:02:24
Arrival:        Year 24, day 8 at 4:24:00
Time of flight: 6 years 161 days 1:21:36
Total ÃŽâ€v:       4,078 m/s

My advice is to go play with the Launch Window Planner - put in your current situation details and the transfer you want, then click around on the resulting graph and look at different potential transfers. Launch windows are not "open-and-shut" affairs... they are continuous functions, and the mathematical minimum might be over-optimized for your needs.

[Kasuha]

Don't forget that you can aerobrake in Jool system and save a lot of dv on that. If you click on the No Insertion Burn option you'll get way lower dv numbers. And slightly different transfers, too.

Departure: Year 14, day 1 at 0:00:00

Arrival: Year 22, day 312 at 5:21:36

Total ÃŽâ€v: 536 m/s

Set up parameters in the calculator - current date and latest date when you want to depart (in advanced parameters), then it will find you optimal transfer. Or you can just click inside a plot to some bluish/greenish place and get transfer parameters for that points.

[Vanamonde]

It's not clear if you're aware of this, but in case it needs to be pointed out, Eeloo and Jool do not orbit on the same plane. You may actually be plotting a course that is adequate in the horizontal planes (on mapview) but missing vertically. Rotate the view angle to see if you are passing above or below the target, and try plotting a mid-course adjustment to correct for that.