Duna crash course

[Odo]

Is it possible to get a course where you will crash into Duna, instead of just fly past it, where at that point you must burn to get into an orbit?

It takes so much fuel to get into an orbit around duna once you've entered its SOI and I was wondering if there was a way to set it up so your ship just crashes into it (Well not exactly, Id have chutes and things)

Thanks for any answers!

Edited September 13, 2013 by Odo

[Rage097]

You just got to play with manuver nodes until you get your encounter to have nearly no seperation.

[capi3101]

Yeah, pretty much you just work with the maneuver nodes once you're in the SOI until you've got an underground periapsis (it's a case where you might consider radial burns, much as they suck). Be prepared to do some serious braking on the way in...honestly not sure how much fuel you'll wind up saving.

[Odo]

I didnt mean like do a crash course once in its SOI, I meant to get it from Kerbin, a burn that launches me into a crash course.'

The idea was inspired by how Curiosity was delivered to Mars. It was sent on a crash course, and then drifted down on parachutes. Well and the whole sky crane ordeal, but you get the point.

Edited September 12, 2013 by Odo

[sal_vager]

Just get into an orbit with a periapsis below ground

[Odo]

Just get into an orbit with a periapsis below ground

Im asking how exactly to do that. Ive only ever been able to get into its SOI with a massive apogee and my course being a huge straight line. Its taken 14 minute burns with a nuclear engine to get out of said straight line course. I dont know if its me sucking at nodes that gets me to Duna that way, but I was wondering if I could just crash into it instead of doing a huge 14 minute burn.

Does anyone know what I might be doing wrong? Because I can never get any closer then a 3 million apogee and straight course

[Tw1]

I did something like this with my Curiosity replication. The trick was a biggish burn soon after I entered they SOI, with lots of mechjeb data for fine tuning, as you can see.

I recommend moving the trajectory so that you aren't going to be going straight down, but still have a fair bit if horizontal velocity when you get close, as Duna's atmosphere is so thin.

If you want ideas, this was the whole mission.

http://imgur.com/a/FAJCJ#OpRQHiz

[Odo]

I did something like this with my Curiosity replication. The trick was a biggish burn soon after I entered they SOI, with lots of mechjeb data for fine tuning, as you can see.

I recommend moving the trajectory so that you aren't going to be going straight down, but still have a fair bit if horizontal velocity when you get close, as Duna's atmosphere is so thin.

If you want ideas, this was the whole mission.

http://imgur.com/a/FAJCJ#OpRQHiz

So it cant be done before you enter SOI? that was kind of the point, to save fuel so you dont have to do a biggish burn.

[csanders]

You might just have to play with nodes more. Make sure you align your plane with Duna before you arrive, and try to make it so either the AN or DN is where you encounter Duna.

If the projected PE disappears (but it still shows an encounter) that means you're going to hit Duna.

[Geschosskopf]

Why are you having to do such a big burn to get into Duna orbit? And why do you think aiming for a collision would take less delta-V?

Let us assume that you have an intercept and will enter Duna's SOI, but your Pe will be like 1Mm high. Adjusting the Pe all the way down to the surface takes slightly more delta-V than bringing down to 11-12km above. Why stop at 11-12km? Because that's prime aerobraking territory. And aerobraking at Duna saves LOTS of fuel in establishing your orbit. With aerobraking, it shouldn't take more than about 1300-1400 delta-V in total to get from LKO to LDO. You spend about 1000-1100 on the transfer burn from Kerbin, you spend about 100 at most en route to Duna tweaking your Pe to the correct aerobraking altitude and getting your inclination correct, and you spend the rest circularizing in orbit after aerobraking.

NOTE: Aerobraking is different every time and there's no instrumentation that really helps so F5, try it at one altitude, and if it doesn't work how you want, F9 and try a slightly different altitude. You want to do your final Pe tweak when you're about 90km above the surface because otherwise it will move too much before you get there.

[Cartz]

So it cant be done before you enter SOI? that was kind of the point, to save fuel so you dont have to do a biggish burn.

It 100% can be done, I've done it many times. What it takes is a lot of patience in tweaking your nodes. What you want to do is burn out of Kerbin's SOI during a normal transfer window, following a node setup to give you an intercept. Tweak it to get the periapsis reasonably close, but as long as you have the intercept you're golden. Once you exit Kerbin's SOI, plan a maneouver node at the ascending or descending node (whichever is closest) and tweak that node until your periapsis is quite small, if it disappears alltogether, gratz, you're on a collision course. If you can't quite get it there/don't have the patience to get it there you can do a final correction burn when you're 10d or so from a Duna intercept, just make that periapsis disappear and you're Duna bound. That said, even with a near perfect initial interception burn, Duna is going to come screaming up behind you at over 1km/s and at that speed, the atmosphere won't slow you down much before you lithobrake. Your best bet for the cheapest Duna insertion is to aim for a Periapsis of 7-10km, this will keep you above most of the terrain and allow you to use the thicker parts of Duna's atmosphere to slow you down for longer. If you burn just long enough to close your orbit, repeated passes through the atmosphere will bleed off enough speed for you to reach a desired apoapsis. EDIT: seems that the forum is dropping all of my formatting... I apologize for the wall of text.

[Evrion]

You can do it. It's hard.

Essentially, Duna is a small target. Kerbin is far away, trying to actually hit that small target is really hard, and requires extremely fine tuning in a way that KSP is not really built for.

Cartz seems to have a good way to go about doing it though!

[SRV Ron]

Set up a mid course correction maneuver. Activate the encounter periapsis so you can see the changes in distance as you fine tune the direction handles. Since chances are you are not coming in to Duna on plane, play with the pink up down handles first to get the smallest value possible. The radical, blue, should be able to bring you into a direct encounter when the marker vanishes. Do the burn but don't be surprise if you are not on a collision course when done.

Once you reach Duna's SOI, you can set up another maneuver to fine tune where you want to hit Duna or do aerobraking into orbit. The closer to the SOI edge, the less fuel needed to get an aerobraking encounter.

[Odo]

Thanks for the answers guys!

Im just getting back into KSP from a 3 month break, so theres a lot I have to catch up to. I didnt know the Mun got retextured so that was a great surprise when I got a satellite orbiting it on my new save

So far all I've done is land an unmanned probe on the mun, orbit the mun with a manned craft and then come back. At least thats all Ive done thats mentionable.

Anyway heres the new rocket Ive just finished developing and working out all of the bugs. Its 3 stages and can pretty much get me anywhere. (I hope) First stage is 4 main sails, this gets you all the way into space. 2nd stage is 2 poodles, this gets you into an even orbit, and the 3rd stage is 2 nuclear engines with 1000 units of fuel. That is what will be taking me places.

http://i40.tinypic.com/2e0txte.jpg

It ended up looking like the Saturn V quite a bit so I cant say thats a bad thing (Also its 100% stock)

Im hoping this will take me to Duna. Do you guys think it can?

Edited September 13, 2013 by Odo