Free plotting interplanetary transfers?

[Dave Kerbin]

I don't play with any mods and after my first landing on Eeloo I've found myself in a bit of a bind. I don't have a lot of experience with interplanetary transfers and up until now what I've done is use Launch Window Planner to give me an idea of when there will be a good planetary alignment for transfer and the approximate ejection/insertion delta-v I should be expecting. Without mods the rest of the information doesn't seem to be useful to me and I just plot a maneuver freehand knowing. Sometimes I think I end up with something close to what the transfer the planner intended while other times the travel time would indicate I ended up with something else.

My problem comes with me trying to get from Eeloo down to Dres. After quick saving I've warped all the way to year 5, day 29 but I can't seem to get a transfer lined up - I got one that looked sort of ok, but it used lots of delta-v and would have taken me through the surface of Eeloo. I do think I know what my problem is though - my orbit around Eeloo is backwards and I'm on an inclined orbit.

Apart from mods are there any tips or tricks to plot an interplanetary transfer by hand, or alternatively even some tips or tricks to adjust my orbital inclination without a point of reference (in Kerbin orbit I can just target the Mun since it lies at 0 degrees).

Edited November 26, 2013 by Dave Kerbin

[purpletarget]

The direction of your orbit around Eeloo doesn't really matter. You can just eject yourself backwards from Eeloo's SOI by driving your ejection clockwise instead of counterclockwise. The velocities will remain the same, you just need to adjust your ejection angles accordingly.

Similarly the inclination may or may not be relevant....depending on how inclined, and where the An/Dn axis is. If the An/Dn axis is pretty much inline with the direction of Eeloo's orbit when you want to escape, you're golden. Otherwise you may suffer some inefficiencies, and that will be dependent on how much the inclination is. If you're only a few degrees, it won't matter much at all. If you're in a polar orbit with the RAAN (An/Dn axis) aligned with Eeloo's radial directions...you're going to have a trickier time.

If you're inclination is above 60 degrees, and you have some time to spare (you may want to backup a bit from your launch window to give some time) then you can try a series of 3 burns to and see if they provide better results.

1. Push your Ap up close to Eeloo's SOI. (This is the part that you probably wanted to do a while before your transfer window). Do this burn near the Sunrise terminator so the Ap is near the retrograde side of Eeloo.

2. At the high Ap, do your inclination change.

3. Back at Pe, conduct your ejection burn for Duna.

If your RAAN is closer to Eeloo's radial, then you'd be looking at having to torque the orbit instead...and that might again put the dV required out of reach.....then you might also just check if it's less dV to just push just outside of the SOI, and then conduct your maneuvers from Solar orbit. (You may loose some oberth advantages, but it may still be less than all the orbit fixes.)

Another option may be to see what dV would be required to land on Eeloo (on or near the equator), and then take off again into an equatorial orbit. (Not likely, but might be easier to execute)

Without some better details about the actual inclination, and relation to Eeloo's trajectory, it's hard to give you anything too definitive. (Screenshots can assist as well)

[Smidge204]

Eeloo to Dres is probably one of the hardest things I can imagine. They are both in inclined orbits with respect to the galactic plane as well as with respect to each other.

Here's what I'd do:

1) Set a maneuver node and plot an escape from Eeloo, but just barely. Since you're headed for Dres (inward bound) you want to do this so you exit Eeloo going the opposite direction as Eeloo's orbit, so you're going slower. Do not wait for/execute this burn yet. (Should have a few days to wait before this node is due)You should get a projected new orbit around Kerbol/Sun. Set Dres as your target and you'll get Ascending/Descending markers with Dres' orbit. You'll be about 10 degrees off I think.

2) Set a new node at the Ascending/Descending node point (whichever is closest). use the magenta handles to tweak your orbital plane to match Dres' as close as you can... should be able to get +/-0.1 with a combination of tweaking the magenta handles and dragging the whole node back and forth very carefully. Do not wait for/execute this burn yet.

3) Set one more node anywhere on the orbit matching Dres' inclination, and plan a deceleration burn to bring your Pe down to Dres' orbit. Drag this node around and play with the green handles (pro/retro burns) until you get an encounter.

Might look something like this when you're done:

Node 1: 6.1 m/s - Leaving Eeloo from a 53,000km orbit

Node 2: 754.4 m/s - Inclination match

Node 3: 525.0 m/s - Lowering orbit for Dres encounter

With the arrangement shown, Dres encounter is 5y, 236d, 12h out. Your time may vary of course.

Sadly I couldn't get a 4th node on the encounter to get the dV for getting captured around a Dres orbit. It'd probably be few thousand m/s though.

=Smidge=

[allmhuran]

The most efficient way without actually knowing the launch window in advance will be as follows:

1) Find the ascending/descending node. To do this, go into map view and tilt the camera so you are looking through Eeloo's orbital plane into the sun. Now pan the camera around until Eeloo's orbit line crosses Dres' orbit line. Make sure you find the node that is closer to the Eeloo's apoapsis, this will reduce the delta-V required to drop down to Dres.

2) Wait for Eeloo to reach this point

3) Launch from Eeloo and apply enough delta-V so that your escape trajectory is in a solar retrograde direction and your periapsis is at the altitude of Dres. This should also be at or very close to the ascending/descending node through the orbit of Dres.

4) enter solar orbit.

5) Set Dres as target and look at the "closest approach" indicators. If they are almost right on top of each other add a manoeuver just in front of your current position and tweak to get an intercept.

6) If the closest approach is a long way away, warp around to the intersection and then put a manoeuvre node slightly BEHIND your current position in your solar orbit. This represents a manoeuvre almost one complete orbit later. Do not touch the handles, just plonk the node down.

7) The closest approach indicators will now move to represent the closest approach as a result of that "manoeuvre", ie, on your next orbit.

8) If the closest approach gets slightly closer, add ANOTHER manoeuvre node further behind the first one. This now represents "two orbits ahead".

9) Repeat step 6 through 8 until the closest approach is very close.

10) Now adjust the handles of the *first* node you put down until you get an intercept.

Now, if you repeat steps 6 through 8 and the closest approach "jumps" a long way past the point where the orbits cross it means your orbital periods are such that it will take a very long time until you get a close approach (or possibly never!). If this occurs perform a small burn at the intersection point. This will change your orbital period without changing the intersection point. Then repeat steps 6 through 8.

Edited November 26, 2013 by allmhuran

[Dave Kerbin]

Eeloo to Dres is probably one of the hardest things I can imagine. They are both in inclined orbits with respect to the galactic plane as well as with respect to each other.

Here's what I'd do:

1) Set a maneuver node and plot an escape from Eeloo, but just barely. Since you're headed for Dres (inward bound) you want to do this so you exit Eeloo going the opposite direction as Eeloo's orbit, so you're going slower. Do not wait for/execute this burn yet. (Should have a few days to wait before this node is due)You should get a projected new orbit around Kerbol/Sun. Set Dres as your target and you'll get Ascending/Descending markers with Dres' orbit. You'll be about 10 degrees off I think.

2) Set a new node at the Ascending/Descending node point (whichever is closest). use the magenta handles to tweak your orbital plane to match Dres' as close as you can... should be able to get +/-0.1 with a combination of tweaking the magenta handles and dragging the whole node back and forth very carefully. Do not wait for/execute this burn yet.

3) Set one more node anywhere on the orbit matching Dres' inclination, and plan a deceleration burn to bring your Pe down to Dres' orbit. Drag this node around and play with the green handles (pro/retro burns) until you get an encounter.

Might look something like this when you're done:

Node 1: 6.1 m/s - Leaving Eeloo from a 53,000km orbit

Node 2: 754.4 m/s - Inclination match

Node 3: 525.0 m/s - Lowering orbit for Dres encounter

With the arrangement shown, Dres encounter is 5y, 236d, 12h out. Your time may vary of course.

Sadly I couldn't get a 4th node on the encounter to get the dV for getting captured around a Dres orbit. It'd probably be few thousand m/s though.

=Smidge=

Thanks, this helped me a lot. Getting out into solar orbit meant I could I could treat it like I would a transfer within Kerbin's own orbit (Mun/Minmus) which I do have more experience in.

I was in a lower orbit (PE 8km) so it cost a lot more Delta-v to escape, but I ended up with very similar numbers and a similar picture. The only change I made was that I made my inclination change at the ascending node instead of the descending one, which meant a longer wait (almost 2 years to reach the other side) but cut about 200m/s from the cost (had I done it at the descending node the cost was about the same as you got).

My final delta-v was:

247 m/s - Leave Eeloo from 30x8km orbit

550 m/s - Adjust inclination at ascending node (after 2 year wait)

517 m/s - Brake for Dres encounter (after half year wait)

And then only 2 years until the Dres encounter. The mk1 lander can sure has a lot of snacks.

[Kasuha]

Variant approach without inclination adjust

1/ place a maneuver to exit Eeloo SOI while staying on its orbit

2/ put a maneuver to AN/DN node whichever is closer and pull retrograde there until your orbit intersects with Dres orbit.

3/ put a maneuver to the point of intersect and pull retrograde to get an intercept in the same point one orbit later. If one orbit is not enough and you would need to pull it below Dres orbit, put a null maneuver on the orbit to see what happens in two orbits and make it two orbits. You can also try to eject from the other of Eeloo/Dres AN/DN nodes

You will then probably end up on inclined orbit around Dres. You can make it equatorial during the braking burn if you care.