Duna Lander DV Requirements

[Branjoman]

Hi, I'm trying to build a Lander that can land on Duna, take off again and rendezvous with the mother ship. How much Delta V should I pack on it to achieve this - any advice of building said lander is appreciated as well.

Edited February 22, 2015 by Branjoman

[Starhawk]

My handy delta-v map says you need about 1300 m/s to make low Duna orbit from the surface. You should need very little to land if you use parachutes.

I would probably shoot for about 1500-1800 depending on the safety margin you want. Orbital maneuvers for rendezvous usually don't need very much.

As far as advice goes -

Build your lander only as large as it needs to be for the purpose. Don't forget the chutes. You don't need a very big engine in Duna's low gravity.

Happy landings!

[pandaman]

Duna has an atmosphere so you can use parachutes to land, but you will need more of them than on Kerbin as its much thinner, so play safe and allow extra deltaV to slow you down for landing if you need to. If you estimate 1500 dV to get to orbit that will give you a bit of a margin, but allow more on top for the rendezvous. RCS will come in handy for the rendezvous too. Depending on what exactly you want to do I would suggest go for 2000 dV minimum as a starting point and, if you can, add more if practical.

Your rendezvous could eat up a lot if you're not careful with it so it may be worth giving the 'mother ship' extra fuel and RCS so that it can manouvre to save the lander needing to carry enough do it all.

Tip from experience - repack your chutes after landing, that way you can abort your take off and increase the chances saving the crew.

Hope this helps.

[Pecan]

Chapter 8, section 4 of the 'Exploring' tutorial in my signature has the Duna lander I recommend (link to PDF and ships downloads for the whole tutorial in that thread's OP).

[Taki117]

While you can use chutes for duna, don't rely on them. ( unless you have the realchute mod). I would pack at least 2km/s but that's mainly because I like to overkill everything. In all reality you shouldn't need much more than about 1.5-1.8km/s.

[panzer1b]

I would say 2K. Gives enough fuel to fix botched up ascents, or to rendezvous with something in a higher orbit. You can get away with 1500 (i think thats the bare minimum) with a perfect ascent, but i wouldnt go below 1600dV, unless you use MJ or something to guarantee a 100% perfect ascent. As for landing, you need maybee 10dV if you bring enough parachutes, or wings to fly in liek a plane (still takes alot of lift as duna = thin atmo).

As for RCS, i wouldnt bother with any more then the ship's crew pod has. Youd be surprised how much that 10 units or so of RCS fuel can do (especially with a light craft). I have a craft thats 20t approx, and ive managed to dock it 3 times before i ran out of RCS and had to play with the engine/luck. Ofc i always forget to give my capital ships RCS fuel (as they use vernors), and that always screws me over when trying to dock with a smaller craft, and then ofc having no rcs fuel for that craft.

[OhioBob]

I'm not adding much new here, but...

First, you need to budget some ÃŽâ€V for your deorbit burn, say 50 m/s.

As long as you're using plenty of parachutes and landing at a low elevation, you shouldn't need much ÃŽâ€V for landing. I generally budget about 50 m/s just in case I have to do a little breaking just before touchdown. If you plan to land at a high elevation, then you'll likely need more. How much more, however, I can't tell you because I don't have much experience with that.

I budget about 1350 m/s for launching into a low orbit of around 50 km. I haven't spent much effort trying to optimize my ascent. I've found the following works good enough: burn vertically until my velocity is 200 m/s, pitch over to 45^o and burn until my velocity is 400 m/s, pitch over horizontally and continue burning until my velocity is 800 m/s, cut the engine and coast up to apoapsis, and, at apoapsis, burn to circularize the orbit.

As others have said, if you must rendezvous and dock with another vehicle in orbit, you'll have to add ÃŽâ€V for that. I think 100 m/s + RCS should be enough in most cases (assuming you're good at rendezvous). Of course that assumes you're already in the correct plane. Chances are you're going to be somewhat out of plane and will have to make a correction. A budget of 100 m/s will allow a 6^o plane change (hopefully you're not off by more than that).

Adding another 100 m/s margin isn't a bad idea, which get's us up to a total of 1750 m/s for everything. Others have suggested as high as 2000 m/s. That number should be more than enough, but, for your first attempt, better to have too much margin than to come up short. You can always get more miserly with your ÃŽâ€V budget after you've gained some experience.

Edited February 22, 2015 by OhioBob

[Scarecrow88]

I have used the same lander I went to the Mun with to land on Duna. The only change I made was to add a couple of chutes. Maybe my Mun lander was over-engineered, but getting back to orbit from the surface of Duna isn't particularly difficult as you should have almost all of your fuel available for the ascent.