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Any good Hint For Eyeballing/non Mechjeb Transfer to Duna...


Sirad
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Well. Im Planning a Caveman Journey to Duna & back.

So there is one Problem that is still unsolved.

I tried several Times to eyeball a Transfer Window to Duna. Dunno how many trys i made. There are several tools out there where you can enter Parameters and so on that put out the angle Duna has to be  and the start angle for your ship. How to eyeball Dunas angle of (lets say) 43.3° with no patched conics, mechjeb etc.

Any hints ?

Or is this just an endless row of trial and error (and noone should tell me he hits it on the spot the first time...)

Is it best to first leave Kerbin Soi to have that conic projected on Sun SOI or better relay on the tools and try to hit the numbers (starting from Kerbin Soi) ?

Maybe someone know best way ?

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You can try Planning Node - it's a pretty new mod that lets you use a maneuver node in Sun SOI and based on that it puts a 3d bullseye to aim for at the edge of the planet SOI you're escaping from. Gives a time to hit it and a dynamic deltaV display to get the speed right. Makes it much easier but doesn't do the burn for you.

PS I'm not sure if you're doing a specific challenge but the Caveman Challenge doesn't allow ANY maneuver nodes or even KER. So I expect that means Planning Node wouldn't be allowed either. 

Edited by Krazy1
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Are you going with optimal transfer windows, or are you leaving Kerbin on any given day? Do you have a rough idea of your ejection angle, or are you just picking a spot in orbit and hoping for the best?

I ask because your ejection angle will obviously change depending on when your launching, what your phase angle is, etc. Assuming you've done a bit of napkin math, and know what your ejection angle is,  it should be relatively easy to find the angle (from prograde) on the orbital map, and begin a burn about 1 min to 1m30s before the angle, and continue burning for about 1min to 1m30s after the angle. But frankly, the dV, the TWR, the phasing, these are all things that are going to affect the amount of time you're burning, so it's hard to be exact without having some bits of data.

Edited by DVQuill
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Hello DVQuill

I get exact Data from that Tool (angles of Planets and angle of descent)

But i wont draw some Lines on My Monitor to measure it out :-)

So is there something else i may have not noticed, except the navball at all ?

 

 

 

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This is web based:

https://ksp.olex.biz/

This is a chart I use religiously, here on the forums:

 

This is a time chart when to leave:

https://m.imgur.com/qvmUhBn

I myself have used the chart, and eyeballed approx angles, launched, and made sure I had extra deltaV for the correction burn.

 

There is a mod that has the transfer window ingame, i use that now

To elaborate, I would choose the system map look straight down on that map place curbing in the proper area on the right side about 3:00. Then I could take my hands and use them as an approximate angle finder if that makes any sense

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in fact, i believe you don't eyeball that transfer. what you do, you go roughly there, you miss the planet. but you count exactly by how many days you missed the planet, and you make a burn in solar orbit in the moment your orbit touches that of duna to change your orbital period and meet duna on the next pass.

it's much more expensive, but easier to do. and packing more fuel is not a big deal.

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5 hours ago, Sirad said:

Hello DVQuill

I get exact Data from that Tool (angles of Planets and angle of descent)

But i wont draw some Lines on My Monitor to measure it out :-)

So is there something else i may have not noticed, except the navball at all ?

 

 

 

I'm not sure if this quite answers your question, but there is a mod called Transfer Window Planner, and you can set it to display the ejection angles on you orbital map, based on the parameters you type in. See below: EwM1W1e.jpg

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10 minutes ago, DVQuill said:

a mod called Transfer Window Planner, and you can set it to display the ejection angles on you orbital map, based on the parameters you type in. See below: 

Thats the one I use, I could not remember the name. (Away from the computer)

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Here's how I eyeball it every time. This won't get you the perfect ideal transfer, but it will be very close.

In the Tracking Station,  fast forward until Duna is exactly "in front of" Kerbin.  If you imagine a line coming out of Kerbin's prograde direction, you want that line to intersect with Duna. Or in other words, if you visualize a line between the two planets, you want that line to touch the very edge of the circle that forms Kerbin's orbit. Perform your burn then.

         _____
        /     \
Kerbin-(  Sun  )
       |\_____/
       |
  Duna-v

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The lowest-energy transfer is going to be periapsis at Kerbin orbit, and tangent to Duna orbit.  If that gets you there a bit early, either adjust trajectory so you go more "outward" from Kerbol initially (will put the periapsis behind the launch point) or add more power and catch Duna on the way back down.  If you're a bit late, launch "inward" towards Kerbol (periapsis after launch point, you'll pass it on the way).  Both of those will also increase the size of the capture burn.

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1 hour ago, Krazy1 said:

You can try Planning Node - it's a pretty new mod that lets you use a maneuver node in Sun SOI and based on that it puts a 3d bullseye to aim for at the edge of the planet SOI you're escaping from. Gives a time to hit it and a dynamic deltaV display to get the speed right. Makes it much easier but doesn't do the burn for you.

I hope it's helpful for this, but the "Caveman Journey" part makes me think this might be an early career mode challenge with maneuver nodes not yet unlocked, in which case Planning Node's current release will throw exceptions if you try to use it. (I have the code changes to disable it figured out, but I put that on hold in the hopes that the next release could also include a fix for node labels showing through planets, but I haven't solved that one yet.)

Edited by HebaruSan
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