How to get to Duna and back without rendezvous

[Dr. Peaky]

I've been to Duna and landed colonies there, but I've never been able to land Kerbals on Duna and get them back again. How big would my stages and lander have to be in order to get to Duna and back? I'd prefer to not have to do any rendezvous or dockings as I'm not very good at that.

Edited January 14, 2015 by Dr. Peaky

[AlexinTokyo]

How long is a piece of string?

How big your lander would have to be will depend on what you plan to send with it. A minimal, 1-Kerbal lander for a direct return to Kerbin from Duna's surface could be quite small, but it would be much larger using a 3-Kerbal pod and carrying a bunch of science gear.

Looking at my favourite ÃŽâ€v map (here), the return journey would be as follows:

Launch to low-Duna orbit: 1300 m/s

Duna-Kerbin transfer: 610 m/s

Assuming that you aerobrake for Kerbin capture, deorbit, and landing.

So your first design goal is a lander that has (at a bare minimum with no safety margin whatsoever) 1,910 m/s of ÃŽâ€v on the surface of Duna.

A minimal design for this would be:

1 x Command Pod Mk1 (with MonoProp removed)

1 x Mk16 Parachute

2 x OX-4W 2x3 Photovoltaic Panels

3 x LT-1 Landing Struts

1 x FL-T200 Fuel Tank

1 x Rockomax 48-7S

This would give you a fueled mass of 2.31 t, a dry mass of 1.31 t, 1950 m/s ÃŽâ€v, and a Duna TWR of 4.6

Then you'd need to get that to Duna's surface:

Kerbin-Duna transfer: 1080 m/s

Duna insertion: 610 m/s *

Landing: 1300 m/s *

*You can save some (maybe all) of these by aerobraking at Duna.

And finally you'd need a lifter capable of putting all of that into LKO from KSC (about 4,500 m/s)

Again, all of these numbers are bare-minimum, no-margin, and assume optimal mission planning and piloting. In other words, use them with extreme care

[Dr. Peaky]

Thanks for the help, mate. Without this, I'd still probably trying to land a Saturn V sized lander on Duna.

[eddiew]

Bear in mind you can aerobrake all but the last hundred metres, and you don't technically need to orbit first. Speccing a Duna lander so that it parachutes around 3 m/s on Kerbin will give you a manageable 12-15 m/s on Duna's midlands, needing only a little tap of your engines just before landing

I've been running Kerbal Construction Time sims of a Duna lander which has 2500 delta-v at descent. The remnants of the transfer stage's fuel will push it into a ~5k periapsis, then detach, so the debris crashes hard while the lander floats down. If the planetary alignment was right for a cheap return, this would land using chutes and about 100dv, take off with about 1500, and have enough to come back home.

That said I use TAC life support, meaning I have to carry extra weight, and take a sub-optimal return window to get home before my kerbals starve, so I'm leaving a fuel and food cache in orbit, rather than having to carry it down to the surface and back. The cache carries a medium grey 2.5m tank's worth of fuel, and and gives the lander a healthy 2200 delta-v when reattached, even dragging all that heavy food and water around. Plenty for an early return - and of course the chutes get used again when landing back on Kerbin, because I'll have room for an engineer on board

[MacroNova]

I strongly recommend you work on your rendezvous and docking skills, as that will open up many new possibilities for you. Where are you having the most trouble?

[cantab]

If you want to calculate things, just check the delta-V map. And use the KER mod if you don't want to do manual calculations.

If you want to wing it, build a ship that has plenty of parachutes and can go from LKO to the Mun, land on the Mun, get into Munar orbit, and land on the Mun again. (Probably not all in one stage). That should run you your Duna mission.

[Skorpychan]

MechJeb is a godsend for rendezvous and docking if you're terrible at it.

[LethalDose]

I strongly recommend you work on your rendezvous and docking skills, as that will open up many new possibilities for you. Where are you having the most trouble?

That's probably the best advice you're gonna get.

Beyond that, doing it without a rendezvous is going to require effective rocket staging and efficient engines, same as any mission.

[Liowen]

If you are not opposed to using mods I would suggest using MechJeb to help learn how to do rendezvous and docking, however if you want to learn it without using mechjeb there is a way. Since you can already go to another planet you can, in theory, rendezvous on a large scale, and if you can do an asteroid mission you have done both in essence. The same principals apply to rendezvous and docking in a smaller orbits, it is just more frustrating since it there are greater chances of missing the target.

[Fearless Son]

I want to add something to what Liowen said: in both interplanetary transfer and orbital rendezvous, there is one concept that needs to be stressed and that is timing, timing, timing. In either case, you cannot just point in the general direction of your target, thrust on full, and hope for the best. You need to wait for your window of opportunity to come up before you start if you expect to make it with a minimum of fuel. Starting with bad timing will expend literally tons of fuel just trying to make the right corrections.

In the case rendezvous with an object in equatorial low-Kerbin orbit (which is probably where you will do most of your rendezvous and get the most practice at rendezvous in general) you want to wait to launch until the target is passing above the Kerbal Space Center. Likewise, make sure your gravity turn is in the direction the target is orbiting so that you do not end up orbiting the opposite direction (which is a huge pain to change once you are in it.) If you can start from an orbit and position close to the orbit and position of your target, rendezvous becomes much easier to manage.

The same goes for parking an interplanetary transition module around a target planet and recovering a lander. Be sure to leave the transition module in a good orbit (preferably equatorial) and put the lander down somewhere that the orbit passes approximately above it. Then wait for the right window to come along before blasting off the lander to return to the transition module.

Further, this practice will serve you well. Taking from my own experience, I have never been able to get to Duna in a way that leaves me enough fuel to get completely back to Kerbin. I always end up stuck in a high-Kerbin orbit. I do still recover the Duna craft, but I need to send a refueling drone out to rendezvous with the parked Duna craft to give it just enough juice to bring its orbit within Kerbin's atmosphere. If I could not do that rendezvous, I would have lost all Kerbals and plenty of valuable scientific data from that mission.