How to get this thing to duna without refueling

[TheThing345]

Yes, this is a base.

No, don't start, it is.

So, I try to get everything done in one go because refueling stations and stuff are too coimplicated and fiddly for me.

My basic duna design was:

Lander

Fuel tank + nuclear engine

Decoupler

4 Fuel tanks + Mainsail, 3 fuel tanks + mainsail on 2 sides. (with decoupler of course)

But since this bigger land- er.. BASE weighs around 60 tons, doing that and just attaching one fuel tank with a nuclear engine won't work, right?

So, what engines on what stage to use?

My initial plan was to create an orbit and land with the 3 engines attached to the bottom of this, but I dont think 3 poodles are going to be enough... or?

So please help me on the staging

Thanks in advance!

Edited May 29, 2013 by TheThing345

[Pugspaceprogram]

Skippers all the way!

Other than launch and transfer.

For launch use a mainsail and for transfer use nuclear engines.

[Ferigad]

Since you are landing on duna you can get some more breaking force by using parachutes in conjunction with the Lander. I always try to use a parachute system where a atmosphere exist. If you got enough parachutes it could work with nuclear engines in landing.

The lander(Base) will need struts too i think, for better connection of the side-pods. Always a question of how mutch fuel u use. And if you burn off your fuel at the landing with your lander, it will get leigther very quickly in the descend.

1 Nuclear engine can handle the job, but as more mass your ship has, the longer the acceleration process will take. If you get a good window, you can use the gravity of Duna to break you a bit down in a long travel trajectory. The shorter your traveltime, the higher will be the end speed at duna approach and you will need more fuel for a break manouver. You could also use the airbreak technic at duna, but i didnt use it myself. Dont wanna use it until real heatdamage is in. Atm it feels more like cheating for myself when i use that way to get my main-ship slower at the approach.

And because you dont wanna go back, you will actually only need the fuel of the nuclearstage for acceleration and deceleration. Hardest part will be breaking out of kerbal orbit, but it can be easy done when you use a support-rocket, like the leftovers from your launch-stage when you get into the orbit of kerbal.

So yes, 1 can work, but you will need some descent skills in planning your route to duna. So actually if you use parachutes as support for landing, you can even use some of the fuel from your lander for the final deceleration. You will deffinitly need more then 1 parachute, thats for sure with that mass. But if you can reduce your mass by use up mostly all of the lander fuel before the parachutes get active, it would be a quit easy landing with parachute support.

[Uberick]

That lander(photo), should have about 2600 dv as it sits. If you swap those poodles with nukes, you'll get more like 5500 dv. If you swap out the three poodles with one poodle, you'll get almost 3000 dv. In this case, you only want to bring engines that will make your thrust to weight ratio on Duna more than 1; which for this ship means bringing one poodle or about three nukes.

If you have a proper Duna window, I want to say that the transfer costs a little over 1000 dv. Aerobraking will make capture at Duna free, so all you really need out of this lander(base) is enough dv to do a transfer and landing. Even 2600 dv should do this just fine. You will arrive at duna with over 1000 dv to spend on your powered landing. If your bring enough chutes, you can reduce the requirements for a powered landing to just a short burst in the last 100 meters or so to drop your descent speed below 10m/s. Don't forget to include drogue chutes, since the atmosphere on Duna is thinner, parachutes work at about 1/5 effectiveness!

So, effectively, if you can get that lander in LKO, it should be able to take it from there.

[Jason Patterson]

I'm with Uberick. Getting to the surface of Duna is very easy, especially if you're good about making use of aerobraking. Even without parachutes you should be able to use that base to get from LKO to Duna's surface in one piece. The easiest landing site is one of the dark brown maria near the equator. They have a low altitude (and higher atmospheric pressure/drag as a result) and are flat.

I generally aerobrake twice, once just to get captured by the planet and then a second (and sometimes third) time to actually land. On Duna this is especially useful since the atmosphere is thin enough that it's easy to go far faster than terminal velocity for long distances. Two aerobrakes also allow you to adjust your inclination and more easily pick a landing site.

[EndlessWaves]

So, what engines on what stage to use?

My initial plan was to create an orbit and land with the 3 engines attached to the bottom of this, but I dont think 3 poodles are going to be enough... or?

Duna has a gravity of 2.94m/s². I'd consider around twice that a minimum for landing, you might be able to get away with a bit less on duna because of the atmosphere but let's call it twice.

Force = Mass x Acceleration. We have 60 mass, we want 6m/s² acceleration, therefore we need 360kN of thrust. Given that one poodle delivers 220kN, two will suffice and three is plenty.

[TheThing345]

In the end, 3 poodles with 3 nukes as a transfer stage below did it

Unfortunately I landed at a hill which makes navigating at that base pretty hard since the atmosphere is really thin there at 2.5km but that doesn't really matter as my kerbals will be staying in that base forever for... science!

Now I would change the prefix to answered if I knew how...

Edited May 29, 2013 by TheThing345

[Ferigad]

Congrats ^^ Next time you can just send a forward scout, little robotdrone or so, let it land and seek out the nicest spot. Or use some fancy mod to get the best surface to build a base

Try Edit your first post, and check in the edit if you can change topic name or if there is a advance option, there should be the dropdown menue für answer status.

[TheThing345]

Congrats ^^ Next time you can just send a forward scout, little robotdrone or so, let it land and seek out the nicest spot. Or use some fancy mod to get the best surface to build a base

Try Edit your first post, and check in the edit if you can change topic name or if there is a advance option, there should be the dropdown menue für answer status.

I actually sent a manned probe (capsule + chute) there for future personel AND surface finding. But my fuel was low and the orbit it sent me in let me land at the exact opposite side of the planet, so yeah. I aimed for somewhere very near the pole, for water and realism

Though that hill is actually a very small crater and I still have enough fuel to land at the bottom of that crater so everything is fine