Jump to content
  • 0

Target-time-to-ascending-node


Go to solution Solved by Waifu Art Thou Romeo,

Question

Is there a way to display orbital info like time-to-ascending-node for an arbitrary body? I know about the target section in Kerbal Engineer but it doesn't have all the information I want.

I am playing RP-1/Principia, and I want to aim for the lunar L4/L5 points, but I really don't want to manually calculate my launch window since it seems like the information I need is probably already calculated somewhere. Do I have to just bite the bullet and make my own estimates?

Sorry if this is a duplicate. All my searches kept giving me things about the vessel's orbit info relative to the target body instead of the orbital info of the target body itself.

 

Mission info in case it's necessary:

Launch a sat to LEO from Svobodny (~51° inclination), maneuver to the moon's AN/DN with the earth, arriving ~5 days before the moon does, burn retrograde (earth-moon barycentric) and hang out at the lagrange point

Edited by Waifu Art Thou Romeo
Additional info
Link to post
Share on other sites

4 answers to this question

Recommended Posts

  • 0
  • Solution
Posted (edited)
6 hours ago, OHara said:

I see.  If you want to use a marker craft, you could place it on the Moon's orbit, 60° ahead of the Moon.  There is a configuration file somewhere to define the orbit of Moon for Kopernicus, so you can copy those orbital elements into the 'set orbit' mechanism in the debug menu (a.k.a. cheat menu) except add π/3 = 60° to the MNA, and set your marker craft into the desired Lagrange point.   Then you have a direct target for your real craft.

Thank you. I'm gonna explore a code-based solution first (I think I can extend either Engineer or Mechjeb to display the info I want), but if I can't get that, I'll just use a dummy vessel

 

Edit:  I got Kerbal Engineer to display it with a little bit of coding. They have a lot of internal code for viewing the fine details of something's orbit, though it looks like it's mostly nonsense in stock. So far RSS/Principia's results seem plausible though.

Edited by Waifu Art Thou Romeo
It was the answer
Link to post
Share on other sites
  • 0

I am fairly sure there is no way to show the time to a target's AN/DN directly.  (Sometimes I cheat a 'marker' craft into an orbit so that I get the markers that I want.)

Myself, from what you described, I do not understand why you want to time any burns relative to the Moon's AN/DN relative to the Earth.  Is that a separate goal to reaching L4/L5 ?

To reach the Earth-Moon L4 point, I think you can launch from 51°N into an inclined low Earth orbit, place a burn at your AN/DN relative to the Moon to raise apoapsis to touch the Moon's orbit, make that burn on whichever orbit has you reach the apoapsis 60° (5 days ) before the Moon does, and then zero your velocity in the rotating Earth/Moon frame when you reach apoapsis.   The zero-ing burn would be at the craft's AN or DN  through Principia's Earth/Moon-barycentric reference plane, but I don't see any link to the Moon's AN/DN relative to either Earth's rotation or the ecliptic. 

Edited by OHara
Link to post
Share on other sites
  • 0
37 minutes ago, OHara said:

I am fairly sure there is no way to show the time to a target's AN/DN directly.  (Sometimes I cheat a 'marker' craft into an orbit so that I get the markers that I want.)

Yeah, I see that. I finally found this post which essentially says you have to code it yourself.  I'm looking into doing that now.

40 minutes ago, OHara said:

Myself, from what you described, I do not understand why you want to time any burns relative to the Moon's AN/DN relative to the Earth.  Is that a separate goal to reaching L4/L5 ?

To reach the Earth-Moon L4 point, I think you can launch from 51°N into an inclined low Earth orbit, place a burn at your AN/DN relative to the Moon to raise apoapsis to touch the Moon's orbit, make that burn on whichever orbit has you reach the apoapsis 60° (5 days ) before the Moon does, and then zero your velocity in the rotating Earth/Moon frame when you reach apoapsis.   The zero-ing burn would be at the craft's AN or DN  through Principia's Earth/Moon-barycentric reference plane, but I don't see any link to the Moon's AN/DN relative to either Earth's rotation or the ecliptic. 

I think you're right that I don't need to, but I don't see how. In hindsight, I'm having a hard time arguing how it was going to work.

My logic was that I would line up the vessel's AN/DN relative to earth with the moon's AN/DN relative to earth. By using the moon's time-to-AN/DN, I would have a specific point I was targeting, and knowledge of when the moon would be at that point. That way I can target any point in the moon's orbit, which is all I really want.

Link to post
Share on other sites
  • 0

I see.  If you want to use a marker craft, you could place it on the Moon's orbit, 60° ahead of the Moon.  There is a configuration file somewhere to define the orbit of Moon for Kopernicus, so you can copy those orbital elements into the 'set orbit' mechanism in the debug menu (a.k.a. cheat menu) except add π/3 = 60° to the MNA, and set your marker craft into the desired Lagrange point.   Then you have a direct target for your real craft.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...