Duna/General Lander, is this overkill?

[TomDRV]

I've designed this as a 'general' lander. It has the delta V and chutes to land on even Laythe.

I'm intending to take it as my lander/ascent vehicle for my first Duna mission. Thoughts?

It has payload capacity for a utility bay (shown) or a rover/anything you can fit under. The docking port at the very bottom is for attaching a 10m heat shield module, which is then ditched before touch-down. The docking port means you can take multiple with you on missions for multiple landings.

 

thanks,

 

Edited July 25, 2016 by TomDRV

[Stargate525]

If it can land on Laythe, it's way overkill for Duna.

[moogoob]

Heat shields are optional at best on Duna. Remember too that Duna has a third Kerbin's gravity. Landing doesn't use much fuel at all, even if you don't use chutes.

Also - that thing's a beast! Remember that you're gonna have to get it out there in the first place - lighter is better in that situation. Here's the biggest Duna lander I've ever made for comparison:

It had delta-v to land and take off again, plus a third of a tank left for odds, ends, rendezvouses and mistakes.

[septemberWaves]

Honestly I like the big lander from the original post. It looks pretty good, and a lot of excess delta-v is often good to have on landers in case of a) bad piloting or b) biome hopping. The one thing I would question about it is why the capsule can be decoupled. The lander is clearly designed for reusability, so why use it as a return vehicle at all when you can instead transport the big lander to its destination once, and have future missions bring only the crew and replacement fuel instead of another new lander?

[Rune]

Tips to shrink that big boy to half or more of its current size:

-TWR. You have a thrust to weight ratio of five. That's about five times more than you need! At the very least four, so you can ditch three vectors and save a whooping 12mT in dry weight. Just that should increase your dV over 4km/s.

-As @eloquentJane says, that decoupler is wasted weight if you can reuse it... or land it whole. Remember the whole thing about this being a lander?

-And chutes. You have a boopload of chutes in there. You also have powerful engines! Unless you need to be able to land with empty tanks, just a touch of engine power can land with many, many less chutes. A couple should do, to make your rockets face the right way and stabilize you, which is all they should do if you want a lean and mean ship.

With all those weight reduction measures, you should arrive at something about the same size as my Heinlein, perhaps a bit bigger with the bay and such. And then you don't need to build a launcher, you can make it launch itself. Because if you certify a rocket for kerbin SSTO operations (3.5~4km/s and 1.5~1.2 TWR), it can land anywhere, and take off again form most places. Or you could not make it SSTO, just almost-SSTO, and stick a small booster underneath to relax the mass fraction requirements. The <2 km/s of taking off from Duna means that it could even land 100% propulsively, and take off again without refueling. Pic for reference of the kind of vehicle I'm talking about (and that you can take a look at in KerbalX):

 

Rune. You cold actually just refuel in LKO and LDO with depots, and do the whole mission in a single stage vehicle.

Edited July 26, 2016 by Rune

[michal.don]

I like to keep my designs simple and on the small side. This is my current Duna lander that serves as a taxi between my Duna base and an orbital outpost placed at 60 kilometre altitude (the lander is the thing on the right).

With a crew capacity of four, surface TWR of cca 5,0, and several hundreds of Delta-V margin, it weighs under 20 tonnes and consists of only 30 parts. I refuel it on the surface, but if you have an orbital refueling station, it's going to work as well. I like the looks of your lander, but getting the beast of it to Duna would be quite expensive (which I guess is not a concern if you are not playing carreer mode).

Michal.don

[Foxster]

Though that's certainly a whopper of a lander, you are much better designing something for each body. What is good for Duna is certainly not so good for Eve without some massive over-enginerring.

You are going to struggle to get that behemoth to your destination and you might end up assembling a huge wobbly thing in LKO. 

Remember that each small increase to the payload leads to a much larger increase in fuel and engines to get it somewhere. So think very, very carefully about what you are aiming to achieve and KISS! Say it is a manned science return mission to Duna. All you want is one Kerbal in a tiny capsule and the set of science instruments that can be ditched before return. Be wary of mission creep where you think you might like to drag along a couple of extra crew, a mining rig, a cargo bay, a rover, some extra solar panels, moar fuel, some extra chutes, RCS, docking stuff, huge landing legs...

[NSEP]

It kind of reminds me of my Vertical SSTO i made awhile back

its has 4,7Km of delta-v. That is alot of Delta-V and pretty overkill for a Duna lander. Bit it is not a Duna lander. And if you want to get Kerbals to Duna, i recommend doing it Apollo style, with the seperate lander and return vehicle.

[TomDRV]

On 7/26/2016 at 2:50 PM, Rune said:

Tips to shrink that big boy to half or more of its current size:

-TWR. You have a thrust to weight ratio of five. That's about five times more than you need! At the very least four, so you can ditch three vectors and save a whooping 12mT in dry weight. Just that should increase your dV over 4km/s.

-As @eloquentJane says, that decoupler is wasted weight if you can reuse it... or land it whole. Remember the whole thing about this being a lander?

-And chutes. You have a boopload of chutes in there. You also have powerful engines! Unless you need to be able to land with empty tanks, just a touch of engine power can land with many, many less chutes. A couple should do, to make your rockets face the right way and stabilize you, which is all they should do if you want a lean and mean ship.

With all those weight reduction measures, you should arrive at something about the same size as my Heinlein, perhaps a bit bigger with the bay and such. And then you don't need to build a launcher, you can make it launch itself. Because if you certify a rocket for kerbin SSTO operations (3.5~4km/s and 1.5~1.2 TWR), it can land anywhere, and take off again form most places. Or you could not make it SSTO, just almost-SSTO, and stick a small booster underneath to relax the mass fraction requirements. The <2 km/s of taking off from Duna means that it could even land 100% propulsively, and take off again without refueling. Pic for reference of the kind of vehicle I'm talking about (and that you can take a look at in KerbalX):

 

Rune. You cold actually just refuel in LKO and LDO with depots, and do the whole mission in a single stage vehicle.

Maybe I'll try and shrink it to something more than size . . . 

[Scarecrow]

I use the same lander for Duna that I use on Mun, I just slap a couple of chutes on it.  The fact that you need to use very little fuel to actually land on Duna means that the vast majority of fuel that the lander is carrying is available for returning to orbit.

[septemberWaves]

This lander weighs nearly 120 tonnes. I've made Eve ascent vehicles with less than a third of that mass (though they weren't single stage). Something I've learned when building landers in this game is to be minimalistic. For a general-purpose three-kerbal lander using that command pod and all science equipment, I can usually extract about 4km/s out of a couple of the smallest Rockomax tanks and an aerospike. A little extra fuel and a second aerospike will usually make such a vehicle Tylo-compatible as well, and therefore also able in theory to act as an SSTO from Kerbin. And that ends up being between 15 and 20 tonnes usually. Your lander has a nice appearance and looks fairly realistic, but for KSP it's really quite overengineered.

[TomDRV]

On 26/07/2016 at 2:24 PM, eloquentJane said:

Honestly I like the big lander from the original post. It looks pretty good, and a lot of excess delta-v is often good to have on landers in case of a) bad piloting or b) biome hopping. The one thing I would question about it is why the capsule can be decoupled. The lander is clearly designed for reusability, so why use it as a return vehicle at all when you can instead transport the big lander to its destination once, and have future missions bring only the crew and replacement fuel instead of another new lander?

It's an escape system; the capsule can detach and abort independently.

Although, the fact the lander can have that type of escape system might be a hint it's too big. 

Taking heed of all these replies . . . I present DALV v2:

Using KW Rocketry, KAS & B9

This one comes with >4000L KAS/KIS inventory space plus cargo bay.

Edited September 11, 2016 by TomDRV

[septemberWaves]

Nice new lander. The only thing I wouldn't be so sure about is whether it can still ascend from Laythe, because if I remember correctly those engines aren't too good in an atmosphere. But for a Duna lander it looks pretty effective.

I am fairly sure that that engine is from Near Future Spacecraft by the way (unless KW has an almost identical one to the Near Future one), just in case you want to add that to the post where it details the mods.

[TwinKerbal]

The only thing I would recommend is lots of chutes. If you have enough, you can conserve dV, and then have a bit of extra fuel to dock (because if you are anything like me, docking is really hard to set up....).

[septemberWaves]

14 hours ago, TwinKerbal said:

The only thing I would recommend is lots of chutes. If you have enough, you can conserve dV, and then have a bit of extra fuel to dock (because if you are anything like me, docking is really hard to set up....).

Parachutes aren't really needed for a Duna lander if you have enough delta-v. It takes around 1600m/s to get into a low Duna orbit (give or take some depending on how well the gravity turn is executed) and a lander with twice that amount will usually have a reasonable margin for error if they use aerobraking and a fully powered landing.

[Ripper2900]

While chutes aren't needed for Duna, it saves a lot of landing dv. Just one or two chutes will slow you down, get the lander vertical and stop horizontal speed. Then you can use a small little burn just before crash-down to convert in to a gentle landing.

I use this approach on Kerbin and Laythe, haven't tested on duna yet with my ssto, but shouldn't be much different. The terminal velocity IS bigger on Duna... 

Landing by chutes alone, will be even cheaper dv-wise, but you'll need tons of chutes! 

[septemberWaves]

8 hours ago, Ripper2900 said:

Landing by chutes alone, will be even cheaper dv-wise, but you'll need tons of chutes! 

Cheaper on delta-v for the ascent vehicle perhaps, but consider the fact that you need to launch all of those chutes to Duna (obviously whilst they're attached to the ascent vehicle of course). And in any case, the atmosphere of Duna can rarely slow you down enough for a landing by parachute without an engine burn, unless you use an incredibly shallow aerobraking trajectory.

[Ripper2900]

4 hours ago, eloquentJane said:

Cheaper on delta-v for the ascent vehicle perhaps

Exactly, this is why I suggest to use just a single chute (or two for symmetry). 

Use that to stabilize, slow most of the airspeed, and kill the horizontal speed. 

Then you can land with just a short burn, having let the chute kill much of the required dv.

Don't plan on using the chute alone. That would usually require more chutes than is worth carrying.