Did first interplanetary trip, have some questions in order to improve

[phemark]

Hey all,

I started playing a few weeks back, but really starting to get into KSP just now.

I've build several ships that can go to and back from Mun/Minmus (with a few explosions and failed landings, but I guess that’s standard ). Yesterday I installed MechJab, and noticed that one of my crafts have deltaV of 9400 (in atmosphere), so I decided to fly to Duna.

Having read a bit, I knew that I needed a certain angle before I started burning. Having reached that angle, I checked with Mechjab if it’s ok (but I always use my maneuvers, and just used MechJab for checking). I then burned and transferred to Duna’s SOI with ~2200 deltaV remaining.

I thought that it will be a good place to use a couple of techniques that I read on the net. I decided to use both aerobraking and gravity assist to slow my ship down. (I saved here, because I had a feeling that might fail a few times ). Now this might be wrong, so please correct me, but this is what I've done:

I made a maneuver so that I hit Duna from the "right hand" side - the side that Duna is going forwards to, because I think that’s how gravity assists works for slowing down.

I also made periapsis to be ~15k, to slow me down a lot, but not land.

It worked fine and I ended up with orbit around Duna. (However, I tried this several times, as periapsis of 11k landed me in Duna, and periapsis of 20k just overshot me, so trial and error. Is there a way to know this?).

Having gotten to an orbit around Duna, I proceeded to go to Ide and land there. By doing this, I tried as much as possible to save enough fuel for going back, but the most I had was ~600 deltaV when I came back to Duna’s orbit. And that wasn’t enough for my maneuvers to get back to Kerbin (I even checked with MechJab, but it needed more deltaV too…). So I decided to land on Duna, gather more science. And wait. (Forgot an antenna, so couldn't transmit, doh...).

Next, I'm thinking of sending a drone with an antenna, to transfer science back. Then, I'll send a rescue mission for that Kerbal (haven’t done one of them yet). So yea, I’m starting to get some fun .

So, based on my story, there are a few things I'd like to ask.

1) Is anything I described above bad practice? What steps could be improved?

2) How to know how deep to go to aerobrake?

3) Was my grafity assisted slowing down done correctly? Is it noticeable?

4) What is the most fuel efficient way to land - go straight down and burn, or go horizontally and burn then?

4) Lifting up from moons and returning to planet orbit - do I do in one go, or do i get orbit, and then burn for another planet orbit? At what point to burn to use least amount of fuel?

5) What deltaV I need for a safe return trip to land on Duna and back?

Thanks!

Edited April 10, 2014 by phemark

[Champ]

Hi

I am not an expert but since noone answerrd...

1/ dont know

2/ trial and failure... Or use Google

3/ it is correct but i am not sure it is usefull if you are not going to another planet

4/ better to first get In orbit then do your burn to change soi : you lose less to grav drag. Also, better to burn In low orbit (oberth). But in your case, ike has too small gravity for à noyiceable difference

5/ check the wiki deltaV map

Sorry for spellimg errorS and bad english : french writing on a smartphone

[mhoram]

Welcome to the forum!

1) For landing you should orbit the planet in the same direction as it rotates (heading should be 90° and not 270°; same is valid for launch).

The reason is that in this way you need less dV to land as if you were going the other way round (this is especially important for planets without atmosphere).

2) Try and error or http://alterbaron.github.io/ksp_aerocalc/

3) Gravity assists only take effect when Sphere of Influence changes are involved.

Since you only want to stop at Duna, there is no gravity assist.

4a) http://forum.kerbalspaceprogram.com/threads/39812-Landing-and-Takeoff-Delta-V-vs-TWR-and-specific-impulse

4b) This is a very complex question - best answer I can give is: it depends.

But the question "At what point to burn to use least amount of fuel?" is more easily answered: The faster you go, the more you get from your fuel. It is called Oberth effect (explanation)

5) there are dV maps available:

http://www.reddit.com/r/KerbalSpaceProgram/comments/1iw30a/a_more_accurate_deltav_map/

http://wiki.kerbalspaceprogram.com/wiki/Cheat_Sheet

http://forum.kerbalspaceprogram.com/threads/25360-Delta-V-map

If no atmosphere is involved, then the dV for the return direction is equal to the departure direction.

[Jimbimbibble]

1. There is no obvious bad practice, but it seems like you could be more efficient with your interplanetary transfer based on your numbers.

2. MechJeb has an aerobraking calculator, but I don't remember what it's called. It only works with stock aerodynamics, so if you're playing with FAR there's no way to tell what Pe you should use.

3. Gravity assists only work to slow you down relative to the parent body of the planet (the Sun if you're assisting around Duna, Duna if you're assisting around Ike.) To slow down you must fly in front of the planet/moon relative to its orbit around its parent body. To speed up, you fly behind it. Practice this with the Mun. See if you can fly a free-return trajectory and a gravity assist to escape.

4. The best way to land on an airless body is to come in with a Pe as close to the ground as you dare go. Then, burn retrograde to slow down. You will gradually pitch up to stay retrograde. In the ideal landing, you finish killing your velocity just above the ground. With experience you will learn how low you can go. To takeoff, do the reverse. Basically, you want to burn as close to the surface as you can and always prograde/retrograde. Landing on a body with an atmosphere, use parachutes to slow down as much as you can. On Duna it should take <100 m/s to land. Mount parachutes on decouplers to ditch them after landing so you don't have to haul them back to Kerbin.

5. The theoretical most efficient way is to burn strait to escape, but this is impractical because you probably won't get the ejection angle correct (and waste dV.) Just get into a very low orbit and it's not too inefficient.

6. dV map is a good way to go. Also, keep in mind that you can refuel in Kerbin orbit if you need to. Efficient Duna designs don't need to refuel, though.

X. Consider using a separate lander for your Duna mission. Also, check out a mod called Protractor.

[Red Iron Crown]

3. Which side of the planet you approach from has no effect on the dV to capture, though it does affect landing dV. The only useful gravity assist for getting captured by Duna is entering Ike's SOI, but Ike's gravity is so low that it's usually not worth the effort.

[Starstrider42]

4. In between. The way mhoram and Jimbimbibble said is the most theoretically efficient, but the last time I tried to do a landing like that I nearly plowed into the side of a mountain. Burning to avoid said mountain ended up using more fuel than if I'd come in on a high approach to begin with.

5. I prefer http://forum.kerbalspaceprogram.com/threads/41652-A-more-accurate-delta-v-map to the Wiki's delta-V map (it's easier to read, for starters). Aside from underestimating how much fuel I used on launches and landings (metaphor said it was probably because my lander's TWR was too low), I've found it to be highly accurate.

Edited April 8, 2014 by Starstrider42
Deferring to people who know more about gravity assists than I do

[CaptainArchmage]

1. Depending on how soon you want to launch and how quickly you want to get to your destination, you might be able to save some delta-V. It is not, however, “bad practice†to use a sub-optimal transfer time that allows you to launch earlier or get to your destination faster. You might want to confirm the vacuum delta-v though. Were you using the LV-N nuclear engines?

2. It depends on which planet you are going to and how fast you are going to hit the atmosphere. One method people use is to quicksave on entering the SOI and run a few “simulations†to determine how to aerobrake. There’s also an aerobraking calculator here: http://alterbaron.github.io/ksp_aerocalc/ . 15k sounds reasonable for Duna if you are coming in from an optimal transfer. However, if you want to get to Ike, you should not reduce the apoapsis too low - anything below the orbit of Ike and you’re technically wasting delta-V. If you can aerobrake just enough to get a capture, you can then modify your periapsis using apoapsis burns to regulate further aerobraking.

3. Gravity assists can be used in KSP, but these are normally used to reach another planet or moon. When approaching or leaving Duna, you might be able to use Ike to do some of the work for you.

4. If there isn’t an atmosphere, the best way is to get the periapsis close to the ground, and when at periapsis, eliminate your horizontal velocity. Best not let the periapsis get too close to the ground because you might crash, though.

4b. The most efficient way to return to orbit around Ike is to lift off and burn sideways to get the horizontal velocity you need. Since Ike has some very high altitudes, you need to be careful. If you burn to escape velocity in orbit around Ike, depending on the ejection angle you will either add that velocity to the moon’s velocity, or subtract it from the moon’s velocity around Duna. This means burning to escape velocity around Ike, you may either end up de-orbiting yourself or at Duna escape velocity.

5. A Duna ascent requires 1500-2000m/s of delta-V. There is this Delta-V planner for launches: http://alexmoon.github.io/ksp/

This calculates around 1034 m/s delta-V from 100km kerbin orbit for a ballistic trajectory at an optimal time, but you should really allow for more delta-V than that. At a sub-optimal time you might need 2000+ m/s delta-v. With the new ARM pack, you can more easily launch a separate Duna ascent and descent spacecraft, and leave a capsule in orbit for return.

[Skorpychan]

Best practice for a Duna landing is to pack chutes, and go in at a shallow angle.

Personally, I tend to pack a lander and a separate interplanetary cruise stage with nuclear engines on, and plenty of fuel.

[Kryxal]

I can't say for sure where, but either your launch from Kerbin or your Duna transfer used more delta-v than they should ... 5600-5800 should be enough to take off AND make the transfer, and a fair bit of that's going to be in vacuum (so likely more efficient).

[phemark]

Thanks for the answers guys, really appreciate it.

So, I created a probe, and sent it to the stranded Kerbal to allow him to send some data. However, when I walk to the probe, I cannot do anything apart Deploy Shute, or raise legs:

Was I wrong to think that this would allow to transmit data?

(There is some electric charge there, and antenna retracts fine)

[Sirrobert]

Congratulations on your trip to Duna.

First of all, check out this DeltaV map if you hadn't already. It will tell you rhoughly how much delta V you need for each trip.

Looking at the map, 9400 deltaV in atmosphere (which would be higher in atmosphere), should be enough for a roundtrip, but not by as much as you'd expect.

First to remember: It costs 4500 deltaV to get into low Kerbin Orbit. And that's IF you have an optimal gravity turn. Since you are new, and it seems like you did everything manual, you probably did not have an optimal gravity turn. (Mechjeb can do a pritty good gravity turn for you, if you get bored of take offs). So looking at the numbers in the map, if you lose 5% (number pulled out of my hat) efficienty on each manouver (since you did it by hand, it would not have been optimal), you'd might indeed end up with your current situation.

That said, 600 MIGHT actually be enough, if you can get a Kerbin encounter that is in the atmosphere. As long as you get such an encounter, you can land. Might be worth a try.

That said, on to your questions:

1) Not to bad. Could probably have been more efficient, but that simply comes with practice.

2) Mechjeb can actually tell you this. The lander guidance has a checkbox that will predict your orbit after aerocapture (I can't remember exactly what it was called, but you'll recognize it when you see it).

This option does a few things: For starters, it will tell you your ACTUAL landing spot if you are landing somewhere with an atmosphere (it takes into account drag, and paints a big target on the map to see where you'll come down)

The option you need here, is what it will tell you when you are in the atmosphere, but not deep enough to land. It will give you an orbit prediction after aerocapture. So simply dip your rocket in atmosphere, option the landing guidance, and fiddle around with how deep in atmosphere. The guidance will tell you in real time what your predicted orbit is, if you were to aerobreak at your current periaps.

If you don't want this, you can always google it. I believe the wiki has information on each body with atmosphere, and how deep you need to be for a capture.

3) Gravity assist does not actually slow you down the way you seem to understand it.

You will only notice gravity assists' effect once you leave the SOI of the body again.

When you enter a body's SOI, you will be pulled along by it's gravity (or pulled back if you are going in oposite direction as it is).

Now I can't actually explain it properly, but the base line is that gravity assists don't matter when you stay in the planet's SOI, only when you leave it.

4) The most efficient way is a suicide burn. Just drop down and burn at the very last moment, so that you lost all your velocity when you reach the ground.

In KSP, that means saving, trying, loading, starting abit higher, loading, trying abit higher, ect until you find the sweet spot (or loading and starting lower). If you use Mechjeb's autolander, it will actually use a suicide burn, but Mechjeb can calculate it exactly. You could to, but that's boring.

So ignoring that, the easiest way is to rhoughly zero out your horizontal velocity, so that you drop straight down, and slowly bleed off speed. Mechjeb can again help you, by giving you the ACTUAL altitude (so how far down until you hit solid ground, instead of how far down until you hit sea level. You've probably noticed already that you often land somewhere with your big altimeter saying there is still 1km to go). Knowing that, you can see how far you have to fall, and how much speed you have to lose per 10 meters to land safely. When you have that number, it's easy to open the throttle a little bit and glide down. Or free fall a little and break later.

This way is the easiest because you won't have to worry about horizontal velocity when you are landing. If you have to much you'll tip over when you touch the surface.

4 again) Get into a very low orbit around the moon (as low as you dare) is probably best. This way you have full control over your orbital transfer.

. There is a special trick to getting from a moonn to it's planet, that can save you alot of fuel (and most people don't know unless someone tells them)

5) well based on the deltaV map from the start:

1000 for Duna encounter, aerobreak for land, 1348 for takeoff to orbit, 480 for Kerbin encounter, aerobreak to land again

For a total of 1828m/s. Ike costs an extra 1830m/s if you want to land there and back. Offcourse this is the bare minimum, and you should take 10% extra atleast, probably more

Note that I did not include takeoff from Kerbin. That's because I always design my interplanetery ships to assamble and refuel in orbit. Now I'm not sure if you can dock yet (that's the most difficult of everything in KSP, noone gets it right on their first try), but once you can, interplanetery stuff will become MUCH easier

[phemark]

Good news!

I managed to land or Duna, next to my first ship! I picked up Kerbal and lifted to Duna orbit. I am now at 70km circular orbit, and have 1200 deltaV. Is this enough to get back home? Or will I need to send another ship?

P.S. I had a lot of science on stranded Kerbal, however now, when I check him, he doesnt have anything - where did all science disappear?

[Starstrider42]

So, I created a probe, and sent it to the stranded Kerbal to allow him to send some data. However, when I walk to the probe, I cannot do anything apart Deploy Shute, or raise legs

Was I wrong to think that this would allow to transmit data?

(There is some electric charge there, and antenna retracts fine)

I assume you're trying to get your kerbal to load their science into the probe? You can only do that with manned command pods, not probe cores. Your probe should be able to transmit its own data (e.g. from its seismometer) just fine; is that working?

[Claw]

Good news!

I managed to land or Duna, next to my first ship! I picked up Kerbal and lifted to Duna orbit. I am now at 70km circular orbit, and have 1200 deltaV. Is this enough to get back home? Or will I need to send another ship?

P.S. I had a lot of science on stranded Kerbal, however now, when I check him, he doesnt have anything - where did all science disappear?

If he went into a capsule, then he left all the science there. You can walk him over to the pod and right click. An option will come up that allows you to remove reports so you can take them with you.

[Kryxal]

Good news!

I managed to land or Duna, next to my first ship! I picked up Kerbal and lifted to Duna orbit. I am now at 70km circular orbit, and have 1200 deltaV. Is this enough to get back home? Or will I need to send another ship?

P.S. I had a lot of science on stranded Kerbal, however now, when I check him, he doesnt have anything - where did all science disappear?

All that science is probably still on the surface ... but the good news is that you should have PLENTY of delta-v for the trip back (chart places it at about 750 from LDO to Kerbin intercept, and you can just aerobrake).

If you are able to dock to the ship you have there, it might be worth sending a fuel tank or two, if not then I'd just come back again later.

[phemark]

Thanks for all the answers everybody! I really learned a lot!

As for science, it's a pity that it was left on the ground capsule. But it will be an opportunity for me to make another trip to get it back:) (and practice quite hard landing on the exact same spot on Duna - more practice for me).

I now understand gravity turns, aerobraking, landing, launch much better thanks to you all.

1) However, I still cant read those deltaV maps. For instance here: http://i.imgur.com/UUU8yCk.png . I understand everything up to Kerbin escape. But then it says that it needs only 130 to get to Duna's SOI and another 250 to orbit it. Do I understand this correctly? Is this true then? Would I only need that little deltaV if I were to transfer from Minmus orbit? (I always transfered from ~600km orbit (so to fastforward faster), but it took much more than 130 to get to Duna's SOI).

And to end, couple of in-game questions:

2) Can I move camera freely? I know how to change focus to different objects, but how can I change focus to Apoepsis, or some other points in space?

3) Can I fastwordard faster at lower orbits? For instance, I have to make Kerbin orbit at 600km+, to use 100k x fast-forward.

And also, is 1000k x fast-forward available?

Thanks!

P.S. In the future, KSP should allow transmitting of data using unmanned pods and antennae (I thought it would work, but it didnt, as one of you explained ).

[wasmic]

Thanks for all the answers everybody! I really learned a lot!

As for science, it's a pity that it was left on the ground capsule. But it will be an opportunity for me to make another trip to get it back:) (and practice quite hard landing on the exact same spot on Duna - more practice for me).

I now understand gravity turns, aerobraking, landing, launch much better thanks to you all.

1) However, I still cant read those deltaV maps. For instance here: http://i.imgur.com/UUU8yCk.png . I understand everything up to Kerbin escape. But then it says that it needs only 130 to get to Duna's SOI and another 250 to orbit it. Do I understand this correctly? Is this true then? Would I only need that little deltaV if I were to transfer from Minmus orbit? (I always transfered from ~600km orbit (so to fastforward faster), but it took much more than 130 to get to Duna's SOI).

And to end, couple of in-game questions:

2) Can I move camera freely? I know how to change focus to different objects, but how can I change focus to Apoepsis, or some other points in space?

3) Can I fastwordard faster at lower orbits? For instance, I have to make Kerbin orbit at 600km+, to use 100k x fast-forward.

And also, is 1000k x fast-forward available?

Thanks!

P.S. In the future, KSP should allow transmitting of data using unmanned pods and antennae (I thought it would work, but it didnt, as one of you explained ).

1: That simply means that from Kerbin Escape you only need 130 extra dV to get to Duna - if you burn from ~100 kilometers. If you escape Kerbin and then burn for Duna, you'll need an additional ~1000 m/s of dV. You should always do the transfer from LKO, as you'll save a lot from the Oberth effect.

2: You can use tab to change your focus, in this order: Ship, Maneuver Node #1, Maneuver node #n, Sun, Moho, Eve, Gilly, Kerbin, Mun, Minmus etc. You can't focus on your apoapsis, but you can make a node at apoapsis and then focus on it.

3: No, you can't - at least without installing plugins. What I do is that I send my ships up to a 125x125 km orbit (you can do it at 75*75 for maximum Oberth). Then I launch a rover from the launchpad, and time-warp with it just sitting there. When it's landed, you can timewarp at max, that is, 100k. Also, press the little button next to the MET (mission elapsed time) in the upper right corner, to change it to Universe Time (UT). Thus, you can see when you have to stop time-warping. Bear in mind that since 0.23.5, time is measured in Kerbin days and years, not Earth days and years. This means that a year is 426 days long, but a day is only six hours long.

And by the way, this is really useful for going interplanetary.

[phemark]

1: That simply means that from Kerbin Escape you only need 130 extra dV to get to Duna - if you burn from ~100 kilometers. If you escape Kerbin and then burn for Duna, you'll need an additional ~1000 m/s of dV. You should always do the transfer from LKO, as you'll save a lot from the Oberth effect.

2: You can use tab to change your focus, in this order: Ship, Maneuver Node #1, Maneuver node #n, Sun, Moho, Eve, Gilly, Kerbin, Mun, Minmus etc. You can't focus on your apoapsis, but you can make a node at apoapsis and then focus on it.

3: No, you can't - at least without installing plugins. What I do is that I send my ships up to a 125x125 km orbit (you can do it at 75*75 for maximum Oberth). Then I launch a rover from the launchpad, and time-warp with it just sitting there. When it's landed, you can timewarp at max, that is, 100k. Also, press the little button next to the MET (mission elapsed time) in the upper right corner, to change it to Universe Time (UT). Thus, you can see when you have to stop time-warping. Bear in mind that since 0.23.5, time is measured in Kerbin days and years, not Earth days and years. This means that a year is 426 days long, but a day is only six hours long.

And by the way, this is really useful for going interplanetary.

Thanks for very useful tips for 2 and 3.

For 3, if I switch to rover, then I wont see those exact figures that I need before the maneuver (like time until I need to make it)? How do you time it?

And sorry for asking about this again, but I still dont understand 1 - you say 130 deltaV in one case and 1000 deltaV in another case, but to me they sound like the same cases, just different deltaVs - what am I misunderstanding?

[Red Iron Crown]

And sorry for asking about this again, but I still dont understand 1 - you say 130 deltaV in one case and 1000 deltaV in another case, but to me they sound like the same cases, just different deltaVs - what am I misunderstanding?

You have to add the delta-V costs for all the segments between the two nodes between which you wish to transfer. So, from 70km low Kerbin orbit to 60 km low Duna orbit is 680+180+70+20+130+250+30+330=1690m/s of delta-V. This can be reduced a fair bit by aerobraking at Duna, but if you did the maneuver by rocket burn only this is a good estimate.

[Sirrobert]

Thanks for very useful tips for 2 and 3.

For 3, if I switch to rover, then I wont see those exact figures that I need before the maneuver (like time until I need to make it)? How do you time it?

And sorry for asking about this again, but I still dont understand 1 - you say 130 deltaV in one case and 1000 deltaV in another case, but to me they sound like the same cases, just different deltaVs - what am I misunderstanding?

That 1000 is what you need to escape from Kerbin

What you do with the deltaV maps is you add the numbers from where you start, to where you want to end.

However if there is an arrow pointing TO that node (or any node you pass), you can ignore it, because a good aerobreak can do the same (without costing deltaV)

Ofcourse always remember that those are optimal numbers, so make sure you to bring extra.

For time warping, I suggest Kerbal Alarm Clock

What you do with it is you plot your manouver node, save it in the alarm clock, and go do something else (like warp on the launchpad). Than when your manouver node is coming up, it will stop timewarp and warn you, so you can switch back 5 minutes before the node (or 1 minute, or an hour, or whatever you pick).

It will also save the manouver node for you, so you don't have to fiddle with it again

[phemark]

I think I didnt understand at first, that by burning from LKO i pass all of the other nodes in that diagram. Just one thing still bugs me - where I should be in space, that I would only need 130 deltaV to transfer to Duna's SOI? I'm guessing that if I would leave Kerbin's SOI at a right time, then I would I only need 130 deltaV to get to Duna's SOI, is that correct?

And thanks a lot for the mod, will definitely install it.

Could you all suggest me some other useful mods, that would be helpful to me to learn or ease tedious tasks?

(I still want to control everything I do, create maneuvers/ships etc, but mods like MechJab (information section) and this Alarm mod are really helpful).

[Red Iron Crown]

I think I didnt understand at first, that by burning from LKO i pass all of the other nodes in that diagram. Just one thing still bugs me - where I should be in space, that I would only need 130 deltaV to transfer to Duna's SOI? I'm guessing that if I would leave Kerbin's SOI at a right time, then I would I only need 130 deltaV to get to Duna's SOI, is that correct?

You need to be 70 km above Kerbin, carrying enough speed to escape Kerbin's SOI. If you wait until you actually escape Kerbin's SOI, the delta-V cost will be greater.

[Sirrobert]

I think I didnt understand at first, that by burning from LKO i pass all of the other nodes in that diagram. Just one thing still bugs me - where I should be in space, that I would only need 130 deltaV to transfer to Duna's SOI? I'm guessing that if I would leave Kerbin's SOI at a right time, then I would I only need 130 deltaV to get to Duna's SOI, is that correct?

And thanks a lot for the mod, will definitely install it.

Could you all suggest me some other useful mods, that would be helpful to me to learn or ease tedious tasks?

(I still want to control everything I do, create maneuvers/ships etc, but mods like MechJab (information section) and this Alarm mod are really helpful).

Actually, asuming you get a correct escape trajectory, you need all those nodes at the same time, and a single burn will get you on an encounter with Duna (excluding minor course corrections along the way, to fine tune your encounter)

As for mods: Mechjeb can do an incredable amount of things. You could for example plot your own manouver node, and than let Mechjeb excecute this node. Usefull for when you need exact, very small burns. (for example only 1m/s deltaV, which is the kind of burn you need when you make corrections far away from an encounter. To get that accurate, you'd need to burn half a second at minimal thrust. That's almost impossible to get right by hand, but Mechjeb can do it).

You can also use Mechjeb to make precise changes to manouver nodes (with the manouver node editor), by entering numbers, instead of dragging the points on the node itself. Also very usefull if you want to to finetune encounters.

Edited April 9, 2014 by Sirrobert

[phemark]

Coming back for that 130 deltaV - where I should be in space, that by doing that 130 burn, I would end up in Duna's SOI?

I need to be at 70km LKO and travelling towards end of Kerbin's SOI, and then that additional 130 would move me towards Duna's SOI? Do I understand correctly?

[Red Iron Crown]

Coming back for that 130 deltaV - where I should be in space, that by doing that 130 burn, I would end up in Duna's SOI?

I need to be at 70km LKO and travelling towards end of Kerbin's SOI, and then that additional 130 would move me towards Duna's SOI? Do I understand correctly?

You have to do it all in one burn from a 70km orbit of Kerbin for the numbers to be valid. If you do a burn of 950m/s, you've spent enough dV to escape Kerbin's SOI. If you burn another 130m/s immediately, you can get a Duna encounter (assuming your angles are right). If you wait until you're further away from Kerbin, you'll need to burn more than 130m/s to encounter Duna.

Edit: More precisely, you need to do all the burning at 70km altitude, it is possible to split the burn up into smaller burns, each done at the 70km periapsis.