Oscar III: Interplanetary Lander

[air805ronin]

I just started playing Tuesday and I figured since so many people share out designs and I'll share my favorite I've put together.

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This is the Oscar III and its entirely stock parts. I wanted to build something that would give me a lot of freedom to reach other Spheres of Influence. I saw that patch .17 was going to include other planets and I wanted something I think can give me the freedom to reach some of those (maybe without a return), but can be used for my fuel burning noob attempts at landing on the Mun and Minmus.

Stage 1: Large rockets and smaller rockets fire to push the heavy weight up all the way out of the atmosphere.

Stage 2: The large tank rockets should have about half a tank of fuel left, I use this to circularize my orbit between 100k and 140k. I guess it is a little wasteful.

Stage 3: You have 4 tanks and a much lighter weight that I planned for use to do the transfer to your target.

Stage 4: The lander stage. I haven't successfully landed it yet, but I'm 100% sure you can at least land on the Mun with half a tank left. I think the landing stage may need to be modified with extra tanks for a longer trip

Stock:

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With a Mechjeb autopilot, for those who like that kind of thing. I've used it once to examine how I'm messing up landings and it got me to the moon with a TON of fuel. This makes me think this design could be used for interplanetary travel, though likely one way.

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[Awaras]

How did you manage to connect the four large fuel stacks to the center stack with 2 radial decouplers each? I didn't think it was possible...

*edit* Never mind, I see now that the bottom set of decouplers isn't even connected.

Edited August 18, 2012 by Awaras

[air805ronin]

The second set aren't attached? I have a little trouble seeing sometimes when things are lined up, I guess I'll get better at that. I'll just take them off since they are likely useless weight.

Any advice? I was going to start attacking my designs with the mathematics in the How-To area to try to make them better.

If anyone uses this as a basis for something else, I'd love to see the designs.

[Awaras]

My first advice is to use struts instead of the lower set of decouplers.

Next, use fuel lines going from the outer stacks towards the inner ones - two fuel lines going to the bottom of every one of the four large stacks from the bottom of the smaller stacks connected to them, and then a single fuel line from the bottom of each of the four large stacks towards the bottom of the central stack.

You should find that you will get into orbit with more fuel than before.

Second, since the fuel lines will let you keep the center fuel stack full of fuel until the moment you decouple the four outer stacks, let the central liquid fuel engine engage from the beginning of the flight instead of staying off until the outer stacks run out of fuel.

Third, why did you place the SAS between the command capsule and the decoupler? once you decouple the rest of the rocket, the SAS is useless. For the same reason, you don't need 2 parachutes. One is enough.

[air805ronin]

I'll give those a try.

I put the SAS there simply because that's where I put it and I never knew it was useless till just now. It just never occurred to me. The two parachutes is to make up for the extra mass of the SAS. I found that if I had only 1 then sometimes the parachute would rip off.

I have just begun messing with fuel lines and hadn't test how they distributed fuel.

There is a lot of stuff you don't know when you first start out. I guess I'm fairly lucky I made it as far as I did!!

[Awaras]

The SAS is useful while your rocket is large - it improves the maneuverability of your rocket. But when all you have left is the command pod, the SAS is a dead weight. Just switch the SAS and the decoupler around so the decoupler is between the command pod and the SAS.

[air805ronin]

Thanks for the info! I really didn't get how the fuel lines distributed fuel so i will definitely give them a go on Oscar IV. Thanks for the advice. If I improve it a ton I'll do a repost of the improved craft.

[air805ronin]

It turns out that fuel lines are apparently directional. I put them on the wrong direction at first and my third stage wound up not having fuel. Whoops. I reversed them and now my third stage is completely topped off when separation happens.

Once I got that fixed I do indeed have much more fuel once I get to orbit. In fact I almost have an entire tank of the huge fuel tanks left to boost into an orbit, and maybe into a transfer. This extends the range of my craft immensely. My only problem now is to counteract a spin I'm getting until I hit my third stage. This implies, to me, that my fuel lines aren't symmetrical and are adding spin to my in atmosphere flight.

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[Moustachauve]

Did you try to add winglet? They help to control spin while in atmosphere

[air805ronin]

Did you try to add winglet? They help to control spin while in atmosphere

I tried them when I was having earlier problems. I will try them again, and other things, until I have this solid. Thanks!