Flight Question Arriving at Mercury with PeA to high

[danmand]

Hi Folks

I'm new to orbiter and have been having a blast learning everything. I've read / followed quite a few tutorials and finally made it to Mars using the IMFD 5.5 full manual as a guide.

I decided to try a flight to Mercury from Earth using the Arrow (what an awesome ship!) with the idea that I would work my way back through the planets leaving refueling space stations along the way at each planet for future visits.

I started in orbit around the Earth and used IMFD 5.5 to plan a "source-plane" flight. The plan took me past the sun with my ApA between the Sun and Mercury's orbit then intercept Mercury on the way back.

I ejected from orbit, warped till I wasn't in Earth's SOI anymore and then did the first correction burn.
I did the plane transfer burn when Tn went to zero using the autoburn and after the burn Rin and dv both said zero.

The problem started when I got to Mercury. My ship arrived at Mercury's oribt well ahead of Mercury and my closest PeA was over 2G. The orbit insertion burn put me in a huge orbit above 1G outside of Mercury's SOI. I couldn't figure a way to get to the planet from there. I thought I could fast forward to a node and change the oribt lower but the ECC kept changing. Maybe because I was out of Mercury's SOI?

Did I do something wrong?
Is there a way to monitor and adjust your planned PeA during the trip?

Thanks for the help and I apologize if I got any of the terminology wrong. I'm still learning and feel free to correct me on it.

Dan

 

[TMac3000]

2G is waaaay outside Mercury SOI. Use the IMFD Map program. It will tell you what your closest approach to Mercury will be. The place has a gravity well the size of my computer chair, so your PeA needs to be <10M or you're screwed

 

[Loru]

I usually use "Planet Aproach" & "Orbit Insert" components of course program in MFD when I'm aproaching planet. You can set there desired PeA, Inclination, and even set autopilot to perform orbit insertion burn.

 

[sorindafabico]

You can plan a MCC with IMFD's Map and Course=>Delta Velocity screens to adjust the PeA.

There's a lot of guessing, but if you did a good Trans-Mercury Injection, the delta-v of the MCC will be low.

I'm supposing you know how to use the "Plan" option of the Map screen.

 

[danmand]

Seems like what I did wrong was to completely rely on autoburn. I haven't studied the map program in detail yet so I guess that's my next step.

I also like the idea of of the planet approach / oribt insertion combo. I thought about trying it when I was playing around with different ideas but the since the manual talked about using planet approach to bypass a planet, I put the idea aside. I'm going to try that method as well.

Thanks again for the help and I'm sure I'll have more questions as I move along.

---------- Post added at 07:53 PM ---------- Previous post was at 05:15 PM ----------

I did it! Thanks for all the help.

One question. When I orbit Earth and am on the map (regular, not IMFD) display, my position moves from left to right. On Mercury, it's moving from right to left. Is this ok?

 

[TMac3000]

It's fine, unless you are targeting a moon. But since Mercury doesn't have any moons, you should be okay. What happened was that you evidently approached the planet from the retrograde side. About one week before orbital insertion (604.2k s), check the inclination of your approach. If it's greater than 90*, you will insert into a retrograde orbit. This can be fixed by burning toward the other side of the planet

 

[garyw]

Even after all these years I STILL use encounter MFD for fMid course corrections. It has the best visualisation of how close an approach will be of anything.

[ame="http://orbithangar.com/searchid.php?ID=1823"]Encounter MFD[/ame]

 

[danmand]

Got it fixed. Thanks :thumbup: