Race to the Jool (and back)

[adammada]

So, munolith on Mun sent strange signal in direction of Jool. Kerbals have to go to Jool and check it ASAP.

Rules;

1. Only stock parts + mechJeb + information tools like AdamKSP etc allowed.

2. You need to launch without waiting on launchpad (start new profile, launch asap, don't wait for correct phase angle). You can always wait on high orbit and warp.

3. Jool is reached when you will be on less than 200 000 m altidude.

4. You have to go back to Kerbin!

5. Time of flight showed on upper lef corner of screen counts.

6. Show screens, write about your strategy.

Two categories:

- fastest to Jool and back (time of land on Kerbin counts)

- fastest to Jool (not important how slow you will go back, time of reaching Jool counts)

[adammada]

Mine result:

- total journey time = 561 Days, 4 Hours, 39 Minutes, 20 seconds

- time to Jool = 297 Days, 15 hours, 41 minutes

Photos: http://imgur.com/a/ci1tT

Strategy:

I used Protractor Mod ( http://kerbalspaceprogram.com/forum/showthread.php/21544-Plugin-Part-17-Protractor-Planetary-Lunar-Rendezvous-Mod ) to calculate / show angles and MechJeb to help piloting (but not used any mechjeb transfers, just Ascent and SmartAss).

After launch I went to 620 000 m Kerbin orbit (maximum warp requires over 600 000 m altitude). Then i waited for good phase angle. Because high orbit is pretty slow, i didnt get excatly phase angle, because i wanted good ejection angle.

I fired prograde and waited until I saw that ship would be entering Jool SOI (got caught by Minimus SOI on way...). Then i warped until about half of way and then corrected inclination (go up), also made periapsis close to Jool. Warped again until entering Jool SOI. I saw that i would orbit Jool clockwise, which is not supported by Protractor Mod, so i changed course to go counterclockwise and periapsis about 131 000 m, cause i wanted aerobraking. Jool atmoshpere starts at about 137 000.

By trial and error i discovered that lower than 125 000 periapsis guarantees to much aerobraking (no going orbit again), thats why i used 131 000 .

That aerobraking gave me higly elliptical orbit.

I also saw, that i'm few degrees from good phase angle to Kerbin, and angle is getting worse. I tried to circularize orbit to make good ejection, first made retrograde to have orbit less elliptical, then at apostatis burned to make it circular at higher altitude (didn't want to wast to much speed), it required lots of dV. When i reached ejection angle I fired engines.

I watched my orbit on MAP, and got worried cause it crossed Kerbin orbit, and there was no hit. But when it crossed some more, i got hit (better be to early than too late ). I warped until about half of journey and corrected periapsis (inclination and retro burn to go straight to Kerbin).

I hit atmoshpere really fast, but aerobraking + some engine thrust was enough to lower speed (but max G is 72 ).

Edited September 24, 2012 by adammada

[Oggula]

I'm in the process of return from a 140km circular Jool orbit at the moment, but it won't be record breaking by the time it gets back to Kerbin because I delayed leaving Jool to make sure my landers from Bop and Vall got back

[adammada]

140km circular Jool orbit

Edge of atmosphere, better dont dive your landers few km below...

Anyway, i'm looking for faster transfer ways than Hohmann orbit, cause fuel isnt really an issue ( Nerva rulez )