Understanding orbital mechanics

[Delusional Poet]

Hi there.  New space explorer here.  So far, the extent of my KSP success is about at the Apollo 8 level.  I have managed to orbit Mun and return.  I currently have a mission on the way out to Minmus and another going to Eve with the same game plan.  I’ll deal with landing later.

Right now I’m having 2 issues.

1.  I’m having a Devil of a time getting reasonable intercepts of Minmus using nodes.  I’m basically getting into circular orbit of K, then tossing a node down, setting apo to about 46Mm, and screwing around with norm/a-norm and whatever the blue ones are called and moving the node around my orbit trying to get an encounter more or less randomly.  There has to be a more intelligent way for me to plan this thing so it doesn’t take me 20 minutes to get something that only kind of works.

2.  My spacecraft isn’t fantastic at reentry.  If I set per to 58km, I hit the surface before chutes deploy.  Once I got chutes to deploy at 150m above surface for all the good that did.  Only way I have landed safely has been a big retro burn on the way down, and I want to use that fuel for other stuff.

 

Anyways, thanks for reading all that.

[18Watt]

4 minutes ago, Delusional Poet said:

I’m having a Devil of a time getting reasonable intercepts of Minmus using nodes.

It's much easier to match inclination before you burn for Minmus.  It's a small target to hit, having the inclination match as closely as possible while in circular Kerbin orbit helps greatly.  I recommend that.  Later on, you can start launching directly into Minmus' inclination.  But that's a different discussion.  For now, try getting to Kerbin orbit, then matching inclinations, then burning (or setting a node) for Minmus.  

7 minutes ago, Delusional Poet said:

My spacecraft isn’t fantastic at reentry.

A screenshot of your reentry craft might help here.  I suspect your reentry vehicle is not draggy enough.  Normally once you get deep in Kerbin's atmosphere the drag will slow you to safe 'chute speed long before you hit the ground.  If that's not the case, your vehicle is too aerodynamic.

One common problem is if your reentry vehicle tends to point into the wind, which makes it not draggy at all.  If your reentry capsule is pointing down naturally on reentry, that probably will not work.  That is a CG versus center of lift/drag issue.  Again, a screenshot of your reentry vehicle would likely help greatly in troubleshooting.

Good luck, and welcome to the KSP forums @Delusional Poet!

[Blaarkies]

Once you reach low Kerbin orbit, move the map view over to Minmus and select it "As Target". This adds a bit of extra info, like these yellow tags on your orbit line. These yellow AN / DN tags are the Ascending Node, or Descending Node. They mark the point where the 2 orbital planes intercept.

If you do the trans-Minmus injection burn at one of those nodes in low orbit, you will end up having your Apoapsis at an intercept point of Minmus' orbit. The trick is to time that so that the craft and Minmus reach that spot at the same time.

This is where maneuver nodes help out a lot. You can click "add orbit" in the node, which tells it that you plan to do that burn 1 orbit later (or 10, or 15, .etc). Set the maneuver node until it intercepts Minmus itself, or gets a close approach (you can always set a correcting burn midway to fix that if you prefer)

[Nazalassa]

Welcome @Delusional Poet! I wanted to give some advice but what I wanted to say has already been said :)

[Vanamonde]

Try adjusting your orbital inclination at the half-way point of the transit. This requires less dV. Here's a guide I made which I haven't updated for a long time but which should still be helpful. Skip to the part about getting to Minmus, if you like. 

A re-entry with 58km periapsis shouldn't be dangerous. I often set mine to 32kms without trouble. Maybe there's a problem with your ship design? What does it look like? 

[Delusional Poet]

I’m not really sure how to post a picture.  Do I hit print screen to take a screenshot?

[Vanamonde]

1 hour ago, Delusional Poet said:

I’m not really sure how to post a picture.  Do I hit print screen to take a screenshot?

In the base game, F1 takes a screenshot and puts it in a screenshot folder. If you don't already have that folder it creates one at that time. You can then upload the picture to a service like Imgur.com, and copy the link they provide into your posts here. The BBCode version works best, from Imgur. 

Also, welcome to the forum.

[BodyHacking]

What on earth are nodes? I'm a fresh player who probably needs to  google more. It sounds like there are some elements that would make stellar transit easier than point&pray!

[Maria Sirona]

12 hours ago, BodyHacking said:

What on earth are nodes? I'm a fresh player who probably needs to  google more. It sounds like there are some elements that would make stellar transit easier than point&pray!

Manouver nodes are a feature of KSP that lets you plan manouvers.

[Delusional Poet]

One of the tutorials gives a brief overview on how to use them, but it really only scratches the surface.

[Bej Kerman]

On 1/18/2023 at 3:30 AM, Delusional Poet said:

Hi there.  New space explorer here.  So far, the extent of my KSP success is about at the Apollo 8 level.  I have managed to orbit Mun and return.  I currently have a mission on the way out to Minmus and another going to Eve with the same game plan.  I’ll deal with landing later.

Right now I’m having 2 issues.

1.  I’m having a Devil of a time getting reasonable intercepts of Minmus using nodes.  I’m basically getting into circular orbit of K, then tossing a node down, setting apo to about 46Mm, and screwing around with norm/a-norm and whatever the blue ones are called and moving the node around my orbit trying to get an encounter more or less randomly.  There has to be a more intelligent way for me to plan this thing so it doesn’t take me 20 minutes to get something that only kind of works.

2.  My spacecraft isn’t fantastic at reentry.  If I set per to 58km, I hit the surface before chutes deploy.  Once I got chutes to deploy at 150m above surface for all the good that did.  Only way I have landed safely has been a big retro burn on the way down, and I want to use that fuel for other stuff.

 

Anyways, thanks for reading all that.

Without a screenshot of your craft to know what's wrong, I can't give you much advice.

For the chutes problem, I suspect you're setting the deploy altitude to something too low. You want them to deploy above 1000m aka 1km.

[Delusional Poet]

46 minutes ago, Bej Kerman said:

Without a screenshot of your craft to know what's wrong, I can't give you much advice.

For the chutes problem, I suspect you're setting the deploy altitude to something too low. You want them to deploy above 1000m aka 1km.

Thanks, was able to get payload design sorted.  Solved reentry issues completely.

[Bej Kerman]

Just now, Delusional Poet said:

Thanks, was able to get payload design sorted.  Solved reentry issues completely.

Just don't change the default settings unless you have a good reason to