I want to get to Duna... How?

[Jollyranger]

So in my Sandbox I have been to the Mun and Minmus. Now I want to get to Duna, but there are so many ways, Like an Orion/Apollo style, The Martian style with a mothership, A simple giant rocket, etc. What is the Most efficient way? Or the Easiest?

[Geonovast]

I think the most important question that needs to be answered is: Do you want to come back?

[Plusck]

It's possible (but quite difficult) to go to Duna, land and return to Kerbin with the stock "Kerbal X" craft, with a couple of minor tweaks (adding drogue chute, removing ablator mass). The Kerbal X is therefore a handy yardstick giving the minimum for a 3-man there-and-back mission.

So from that point on, the question is what you want to do with your people or probes when they get there... or how much more safety margin do you need? In other words, how much bigger do you want to make it?

If you were doing career, then a science lab orbiting Ike is a great way to get science points and level up your crew members, so you'd be highly recommended to send a lab and relay satellites and whatnot at the first transfer window.

Duna isn't really a good stepping stone to anywhere else, so a mining lander and fuel transfer craft isn't going to be massively useful in the long term, but it'll let you do lucrative mining contracts and lighten the load for subsequent missions if you feel like sending all that heavy equipment.

Edited March 4, 2018 by Plusck

[Jollyranger]

1 hour ago, Geonovast said:

I think the most important question that needs to be answered is: Do you want to come back?

Yes, I think coming back would be nice.

36 minutes ago, Plusck said:

It's possible (but quite difficult) to go to Duna, land and return to Kerbin with the stock "Kerbal X" craft, with a couple of minor tweaks (adding drogue chute, removing ablator mass). The Kerbal X is therefore a handy yardstick giving the minimum for a 3-man there-and-back mission.

So from that point on, the question is what you want to do with your people or probes when they get there... or how much more safety margin do you need? In other words, how much bigger do you want to make it?

If you were doing career, then a science lab orbiting Ike is a great way to get science points and level up your crew members, so you'd be highly recommended to send a lab and relay satellites and whatnot at the first transfer window.

Duna isn't really a good stepping stone to anywhere else, so a mining lander and fuel transfer craft isn't going to be massively useful in the long term, but it'll let you do lucrative mining contracts and lighten the load for subsequent missions if you feel like sending all that heavy equipment.

I haven't made much progress in career, so this is a sandbox mission. I would really just like to land there, plant a flag, and come home just so i could say I was there. For a career mission I would do something bigger. I tried building a mothership and going to Minmus once and it got stuck in an elliptical Kerbin orbit on the way home... in a retrograde orbit. I would prefer something lighter and easier to use/build so that doesn't happen again. I really just came here to see what the easiest and quickest way to land and return is.

[Foxster]

Coupla tips...

It's a lot easier coming back. You can almost ignore Duna's atmosphere when going to orbit and the gravity is a lot lower. So a smallish lander can also be a Kerbin return craft without messing about with an Apollo-like mission.

Conversely, Duna's thin atmosphere does not help brake nearly as much as Kerbin's. So some air-brakes, drogue chutes and main chutes will likely be needed for a 0dV landing.  

 

[Jollyranger]

3 hours ago, Foxster said:

Coupla tips...

It's a lot easier coming back. You can almost ignore Duna's atmosphere when going to orbit and the gravity is a lot lower. So a smallish lander can also be a Kerbin return craft without messing about with an Apollo-like mission.

Conversely, Duna's thin atmosphere does not help brake nearly as much as Kerbin's. So some air-brakes, drogue chutes and main chutes will likely be needed for a 0dV landing.  

 

So basically one giant rocket?

[Foxster]

9 hours ago, Jollyranger said:

So basically one giant rocket?

Depends how many crew and how much junk you want to drag along. Keep the payload small and it doesn't need to be giant at all. But, yes, a single craft is very do-able and a lot simpler than messing about with docking. 

[radonek]

11 hours ago, Jollyranger said:

So basically one giant rocket?

Direct ascent is quite possible, but I'd advise against it. It requires more complicated lander than Mun/Minmus, more delta-v, more precise ejection burns… if you can handle these safely, you don't need to ask in a first place. I always say - get a solid handle on rendezvous and docking before going interplanetary. Being able to meet tanker ship can get one of lots of sticky situations. This is even more true for direct ascent scenarios, as those tend to operate with lower margins. 

[Guest]

Craft-wise, going to Duna (and back) isn't much more difficult than going to the Mun (and back). You only need a couple hundred more m/s to get there and you'll be able to get most of that back if you want to risk an aerocapture.

You need to make a few adjustments to the lander: it needs a bit more TWR because of the higher gravity, but if you pack a couple of parachutes you'll be able to make do with more or less the same dV because you'll barely need any on the way down, just the burn to get yourself suborbital and another one for the last 20 m/s or so.

Taking off is just like from the Mun except you should go the first stretch a little more vertically and a little slower because of the atmospheric resistance -- there's not a whole lot of it, but it's enough to mess you up if you completely disregard it.

You do need to know when to go though. Use alexmoon's launch window planner for that: https://alexmoon.github.io/ksp/

A note about aerocapture -- you don't need a particularly robust craft for this when coming from Kerbin (heat shields are usually not necessary, as long as the surface you're presenting to the atmosphere doesn't have anything super sensitive on it), but it's very hard to know beforehand exactly what altitude you need for it, and getting it wrong will likely mean either a total loss or not getting captured at all. So if you're not into quickload abuse, it's safer to go with a propulsive capture.

[Scarecrow]

I created a thread a while back that showed, with a few modifications, a craft you used to get to Mun could also make it to Duna and back.

Thread is here

if you are interested

[Jollyranger]

4 hours ago, radonek said:

Direct ascent is quite possible, but I'd advise against it. It requires more complicated lander than Mun/Minmus, more delta-v, more precise ejection burns… if you can handle these safely, you don't need to ask in a first place. I always say - get a solid handle on rendezvous and docking before going interplanetary. Being able to meet tanker ship can get one of lots of sticky situations. This is even more true for direct ascent scenarios, as those tend to operate with lower margins. 

I would say I am quite skilled at docking, but it still takes me about 3 or more extra maneuvers to get an encounter. This little ascent vehicle would have to have a huge margin of error for me (maybe 200 m/s) so i can screw around with my orbit. As for return, I usually just aerobrake.

[Guest]

9 minutes ago, Jollyranger said:

I would say I am quite skilled at docking, but it still takes me about 3 or more extra maneuvers to get an encounter. This little ascent vehicle would have to have a huge margin of error for me (maybe 200 m/s) so i can screw around with my orbit.

It's easy to build a lander with about 2000 m/s on it. That'll give you more than your 200 m/s safety margin, if you're using parachutes on the way down. You'll be using about 1500-1600 on the way up and maybe 100 on the way down, so it'll leave you 300-400 to tool around with in orbit.

Moreover, you can build an orbiter/return module with a similar safety margin, so as long as you can get your lander back in orbit, you'll be able to RV. Just meet it halfway with the orbiter.

So yeah, basically: whatever you used on the Mun will work on Duna, if you just add parachutes. More or less.

Edited March 5, 2018 by Guest

[radonek]

1 hour ago, Jollyranger said:

I would say I am quite skilled at docking, but it still takes me about 3 or more extra maneuvers to get an encounter.

You are doing something Wrong. Outside of speedmatching burn, I can dock completely on in-can monoprop.

1. Any helpful  course change not done by lander itself is cheaper (don't have to haul fuel down and up the well). Minimizing eccentricity will make course matching easier, zeroing inclination will spare you big inclination changes (if you stick to equatorial zone), lowering orbit shave overall d-v for lander.
2. Match inclination as closely as possible before planning rendezvous burn. Midcourse plane change is in theory more efficient, but it's not worth the fuss for small changes.
3. With close to zero difference in inclination, you should be able to plan burn that will bring you within 400m of target.
4. Do fine correction immediately after rendezvous burn. Bring up map view, right click on rendezvous marker to keep it visible and just play with RCS and see what it does to encounter distance. Even if you waste some fuel to get it right, it is well worth it. With small, nimble lander you shold be able to get within 300m of target. I often get under 100m.
5. If you somehow still  end too far from target vehicle, be gentle with chasing burns. 50m/s burn may take you there fast, but you will have to kill that velocity in the end. Timewarp is free.

[Gilph]

I had never seen the @Scarecrow tutorial, that was really well done.

Unless you are trying a challenge, Duna is easiest when you have a separate lander and transport and use orbital rendezvous. The ships Spaceport uses are highly efficient and low cost.

I have always approached Duna as a place where I wanted to go repeatedly. So I sent a station with a lot of surplus fuel, a lander, and a 4k deltav ferry to go back and forth between Duna and Kerbin. I would refuel the ferry in Kerbin orbit. Eventually. I would mine fuel on Ike and shuttle to the station around Duna to fuel the lander.

[Jollyranger]

56 minutes ago, Gilph said:

Unless you are trying a challenge, Duna is easiest when you have a separate lander and transport and use orbital rendezvous. The ships Spaceport uses are highly efficient and low cost.

I thought that an Apollo style mission would be the best. I already have done one on the Mun and I have a few Ideas for a Duna Rocket, and now I have KER so I can build the best rocket for it.

[jrolson]

What engine and how much fuel is required to get off of Duna and into orbit?

[Not Sure]

14 minutes ago, jrolson said:

What engine and how much fuel is required to get off of Duna and into orbit?

Ships arent measured in units of fuel and engine. Look up KSP dV to get an idea of how space maneuvers work

[SnailsAttack]

1 hour ago, Not Sure said:

Ships arent measured in units of fuel and engine. Look up KSP dV to get an idea of how space maneuvers work

@jrolson yes, it's kind of like the universal "how far can I go" number.

[jrolson]

Looking up delta-v made me even more confused. Guess i'll just wing it and hope for the best...

[Jollyranger]

19 hours ago, jrolson said:

Looking up delta-v made me even more confused. Guess i'll just wing it and hope for the best...

Delta-v is basically the amount of acceleration your ship can produce before it runs out of fuel.  Say you were in deep space with no gravity or drag affecting you. if you had 1,000 m/s of dV, you could reach a speed of 1,000 m/s before running out of fuel. 

Edited March 6, 2018 by Jollyranger

[Mikki]

All the best for your Duna mission!

Aim for low elevation (Basins) and some chutes can save you some dV for ascend...

Oh well and you can go quite deep and perform a brute aerocapture with your vessel, saves weight, looks allways good too!

Up to 1000dV is possible if you dare to glow hot. Or burnup. 

Cheers!

[Jollyranger]

21 minutes ago, Mikki said:

All the best for your Duna mission!

Aim for low elevation (Basins) and some chutes can save you some dV for ascend...

Oh well and you can go quite deep and perform a brute aerocapture with your vessel, saves weight, looks allways good too!

Up to 1000dV is possible if you dare to glow hot. Or burnup. 

Cheers!

I have practiced aerobraking on mun returns and Duna probes, but the only thing i'm concerned about is hauling a massive heat shield over there.

But I can always add more boosters!

[LameLefty]

3 hours ago, Jollyranger said:

I have practiced aerobraking on mun returns and Duna probes, but the only thing i'm concerned about is hauling a massive heat shield over there.

But I can always add more boosters!

Aerobraking at Duna from Kerbin-transfer is rarely likely to require much of a heat shield. You're more likely, in my experience, to dive too deep into the atmosphere in an aggressive attempt to get ENOUGH drag at all, that you smack into a mountain. Except in the basins and canyons, there air is just pretty darn thin. 

[Mikki]

 Edit: Stock fairing can handle this. As mentioned above, go full valley and pray not to ripp off significant parts.

Edited March 7, 2018 by Mikki