Table of content
- 1 Setup of the ejection burn : timing
- 2 Ejection Burn
- 3 Injection burn at Moho
1 Setup of the ejection burn : timing
Moho is a small planet with a low sphere of influence. Its inclination is 7°. It’s not difficult to intercept it but it is really costly to be captured. For the planning, i have used the trip planner online tool of Alex Moon.
After a lot of search i found a thread on kerbalspaceprogram forum about the difficulty to establish an orbit on Moho. Alex Moon himself explains we have to forget phase angle for Moho…
The phase angle to intercept Moho from Kerbin is -251° but this value is good for a flyby, not for a capture. If we do our ejection burn at phase angle, the required dv to be captured will be terrible, could be about 7000m/s.
The Alex Moon Launch Window Planner will gives us a totally different result for a transfer followed by a capture.
I have used these parameters:
- initial orbit: Kerbin 500km (where we are)
- destination orbit: Moho 75km
- earliest departure: year 2, day 327
I have setup an alarm around year 3 day 83. Now, we have to wait for 180 days.
You can notice Ker gives me a total Dv around 3000m/s because the fuel can’t find a way from the refueler to the nuclear engines. I will transfer fuel when the conventional tanks will be empty.
Meanwhile, i have some spare time to de orbit the launcher stranded in orbit. For this, i used a small asteroid hopper docked at the Ganymede station.
2 Ejection Burn
We are 1 day before the ejection burn. Time to return and have a look to the window planner.
We add a node somewhere and move it until we are around 4h and precisely with a ejection angle of -72 on retrograde. (I could also use precisenode but it seems there is a bug in the version i use: it reset node values each time i swap between map and normal view…)
We can see the ejection angle in Ker (angle to retrograde)
Yes, thanks to nuclear engines, it will be a 30 minutes burn…
Almost perfect, we’ll need to do a mid course correction to match planes … and to correct what will going wrong…
So it’s BURN TIME:
I transfer fuel to keep a low torque.
3 Injection burn and circularization
The injection burn tooks about ‘only’ 1900m/s dv, thanks to a very well timed ejection burn!