Having issues with a 2m MUN rocket

[PhoenixCraftLTD]

I have been trying to develop the ROC, a Munar rocket with only the new 2m parts. I can make high orbit with a 5 booster first stage that drops 4x 2m boosters at the forth atmosphere mark, but that has no Munar injection stage. so i need to go up to 6x 2m boosters to add the extra transit stage, but i every time i add 6x 2m boosters all the braces snap off. I have tried adding more bracing but it keeps popping them. has any one made a good 2m lander with the mark3 capsule?

P.S. I do add in the 1m ASAS pod to the lander stage below the capsule decoupler.

[Pyre]

Without a picture or a .craft file, we can't help much, though I will suggest throttling back to keep acceleration under 4-5Gs.

[PhoenixCraftLTD]

Ok I got the ROC up and to MUN but i ran into some technical difficult with landing the barge of a ship.

[ATTACH=CONFIG]31854[/ATTACH]

I kept the thing at 12ish mps, but the lander legs snapped off. I'm going to try again at 6 msp, and change to my big langer.

[ATTACH=CONFIG]31853[/ATTACH]

Edited August 24, 2012 by PhoenixCraftLTD

[Secular_Response]

That is a huge amount of fuel on that lander. Try using half tanks instead. Try using a first stage with one stack of 3 fuel tanks with the largest motor, with three other stacks just like it mounted radially. Use fuel lines from the outer to the inner stack. Make the second stage just like the first, but with no radially mounted stacks, just the one with three tanks and an engine. Place the lander on top of that.

One method I've found to get the most bang for the strut is to cross them. Where they cross is the junction between two fuel tanks, so it resists the tendency for the stacks to come apart.

The arrow points to another feature, using structural pylons instead of decouplers. They work the same and it prevents the outer stacks from ripping off the engine and lower tanks of the middle stack when decoupled.

This rocket is what I'm talking about.

Edited August 26, 2012 by Secular_Response

[Werwolf]

That is a huge amount of fuel on that lander. Try using half tanks instead. Try using a first stage with one stack of 3 fuel tanks with the largest motor, with three other stacks just like it mounted radially. Use fuel lines from the outer to the inner stack. Make the second stage just like the first, but with no radially mounted stacks, just the one with three tanks and an engine. Place the lander on top of that.

One method I've found to get the most bang for the strut is to cross them. Where they cross is the junction between two fuel tanks, so it resists the tendency for the stacks to come apart.

The arrow points to another feature, using structural pylons instead of decouplers. They work the same and it prevents the outer stacks from ripping off the engine and lower tanks of the middle stack when decoupled.

This rocket is what I'm talking about.

You just gave me so many awesome ideas. Great post, +1

[Kosmo-not]

Here's my 3 kerbal Mun rocket. It has plenty of fuel for the job.

https://www.dropbox.com/s/3y72t371gja3k8s/4.craft

[Markus Reese]

Saw your comment about m/s. How did I miss that before?

I kept the thing at 12ish mps, but the lander legs snapped off. I'm going to try again at 6 msp, and change to my big langer.

Landing speed on a light rocket is <4m/s. For my large ones, I will feather the throttle and manual control it to less than 1m/s. That speed is probably your largest issue going right now.

[Nibb31]

You have to keep it simple and design your rocket top-down. Start with a lander capable of returning to Kerbin. A half-size 2m tank should be enough and keeps the lander light. However, you want to land with a nearly full tank, so the trick is to use the same booster stage for the Munar transfer, the orbit injection, the deorbit and most of the descent. A standard 2m tank is enough.

After that, all you need is a two stage booster to get the above into Kerbin orbit. This is my design for a simple Munar rocket:

The only trick is that the first stage outer boosters crossfeed the core stage, so that it takes off with 5 engines and when it jettisons those boosters it still has a full 2 tanks to finish the work. Other than that, it's a simple efficient design that can be even uprated to put a base on the Mun.

[Kosmo-not]

Nibb31, are you sure that rocket gets into orbit with 2 stages? By my calculations, it requires some of the 3rd stage to insert it into Kerbin orbit.

[Markus Reese]

The only trick is that the first stage outer boosters crossfeed the core stage, so that it takes off with 5 engines and when it jettisons those boosters it still has a full 2 tanks to finish the work. Other than that, it's a simple efficient design that can be even uprated to put a base on the Mun.

This is something I have started to make alot more use of. Jettisoned boosted fuel storage works excellent. Having outer tanks and engines that feed your core engine does wonders for most stages. Especially for landers like you said. A grouping of outer engines when landed then has the bonus of getting that initial liftoff push. On that topic, the smaller tank groupings and engines work really nice for that I find. My favorite lander atm for the large command module has a half 2m tank with the small 2m engine. Around it 4 of the 400u tanks with the small 1m engine and fuel tanks running to centre. It works very well for a 1m lander and ensures the full 2m tank.

[PhoenixCraftLTD]

That is a huge amount of fuel on that lander. Try using half tanks instead. Try using a first stage with one stack of 3 fuel tanks with the largest motor, with three other stacks just like it mounted radially. Use fuel lines from the outer to the inner stack. Make the second stage just like the first, but with no radially mounted stacks, just the one with three tanks and an engine. Place the lander on top of that.

One method I've found to get the most bang for the strut is to cross them. Where they cross is the junction between two fuel tanks, so it resists the tendency for the stacks to come apart.

The arrow points to another feature, using structural pylons instead of decouplers. They work the same and it prevents the outer stacks from ripping off the engine and lower tanks of the middle stack when decoupled.

This rocket is what I'm talking about.

Ok are you using a plugin to get such perfect symmetry on the struts? i try to get them close but mine are a little off.

[Nori]

You might be interested to know that the flat radial decoupler isn't worth using over the regular one unless you edit the config. The reason is that it weighs 16x more but is only marginally stronger. They really should change it to weigh less and be stronger, but I digress...

Edited August 29, 2012 by Nori

[Nibb31]

Nibb31, are you sure that rocket gets into orbit with 2 stages? By my calculations, it requires some of the 3rd stage to insert it into Kerbin orbit.

It only needs a tiny bit of the third stage for the final circularization, which conveniently jettisons the second stage into a reentry trajectory. I don't like leaving debris in orbit

That third stage has between 10 and 20% fuel left when I jettison it during the final descent, at around 200m above the Mun's surface.

Edited August 28, 2012 by Nibb31