Wondering How to perfect my Ship.

[LadyAthena]

So for starters, this is my ship: http://i43.tinypic.com/2jcg55e.jpg

With it I was able to achieve at least a VERY close pass of every planet in the solar system. However, never having enough fuel to actually make a proper landing. (those 1-2 minute burns are killer).

I decided I should probably make a refueling station in orbit around kerbin, this may help with my fuel supply and allow me to make those landings, and get home to boot. Problem is...

http://i42.tinypic.com/2nsmkc1.jpg

I refitted it with station parts. I already have the main "CnC" in space, which my refitted rocket did perfect at the job. But suddenly when I slap on a large fuel tank it can't make it? O.o;; If it does make it, I make such an absurd orbit due to it being so unstable for no real reason I can't make contact with the beginning of my station I put into space...

What am I doing wrong?

Edit: I am doing the campaign, so I don't have all parts unlocked.

Edited October 24, 2013 by LadyAthena

[toomuchbrew]

I think you are just over thinking this. I think the other problem might be your center over mass so far ahead of you thrust when you go even slightly off vertical, the rocket being top heavy wants to reaim at the ground. Remember, it's much better to do things simply. It also helps in trouble shooting.

[Johnno]

I replicated your launcher best I could and threw on an orange tank to simulate your payload (without those SRBs). I only barely got it to orbit and it was quite apparent that the issue is low thrust to weight ratio which decreases with each pair of asparagus boosters being dropped.

If you want to keep that exact launcher and just tweak it, here's what I'd suggest;

1. Swap out LV-T45 engines for LV-T30 (except for the three in the middle, those should be enough for steering).

2. Remove the SRBs from the payload.

3. Decrease the amount of RCS tanks to save mass.

Either way any launcher has limitations, yours seems to be able to get around 40 tons to orbit, but only barely. You likely had quite a lot less mass on your earlier launches, which is why it was easier. The more payload mass you have the more fuel you have to spend to get it into orbit. Also higher payload mass gives you lower thrust to weight ratio so you spend longer in the atmosphere and you have to be more careful with your gravity turn.

[Ariadne]

If you don't have enough fuel, make your ship more massive. More engines for escaping from the atmosphere, more efficient engines for saving fuels.

I use (Rockomax Jumbo-64 + Rockomax "Skipper")*24 for the beginning flight, (FL-T800*2 + atomic engine)*9 for interplanetary maneuvers and something for landing. This configuration allow me take kerbals on any planet. There is problem with returning, but the design isn't perfect yet.

[nadreck]

Here is my current "science lander" and "flying gas station" the later gets into low Kerban orbit with about 200L of Oxidizer left in the bottom centre stage, while the lander made orbit with about half it's upper stage fuel left. Have been sending the upper stage of the "flying gas station" to Munar orbit to dock with the lander between landings and refill it.

[LadyAthena]

I replicated your launcher best I could and threw on an orange tank to simulate your payload (without those SRBs). I only barely got it to orbit and it was quite apparent that the issue is low thrust to weight ratio which decreases with each pair of asparagus boosters being dropped.

If you want to keep that exact launcher and just tweak it, here's what I'd suggest;

1. Swap out LV-T45 engines for LV-T30 (except for the three in the middle, those should be enough for steering).

2. Remove the SRBs from the payload.

3. Decrease the amount of RCS tanks to save mass.

Either way any launcher has limitations, yours seems to be able to get around 40 tons to orbit, but only barely. You likely had quite a lot less mass on your earlier launches, which is why it was easier. The more payload mass you have the more fuel you have to spend to get it into orbit. Also higher payload mass gives you lower thrust to weight ratio so you spend longer in the atmosphere and you have to be more careful with your gravity turn.

If I don't have the SRB's, it won't even get into space, again, due to the fact that as you mentioned, it'll have to little thrust at the end.

What I do is after I drop 4-6 Engines, I turn on the SRB's. This allows it to get into space. But it handles so insanely, I can't get it lined up properly in orbit to meet up with my other piece.

[FlamedSteak]

Like others have mentioned, by the time you get to the latter stages the centre of gravity is all the way up front and the centre of thrust is all the way at the back. The result is massive instability, and probably a TWR that is far too low.

Getting big loads into space is better done with a flatter structure, that way your thrust and weight distribution stays even. That may change when aero resistance gets modeled, but at the moment it's the best way to do it.

[FoxKit]

You're getting diminishing returns from your overly large launch stage. Adding more rockets and more fuel after a certain point winds up giving you less delta-v, partly because you reach terminal velocity in low atmosphere and waste the rest of that thrust, and partly because the fuel (which scales linearly) is becoming heavier than your thrust (which scales on a curve). You should try to cut it down to 7 or less liquid fuel rockets and some solid boosters.

[SRV Ron]

The ship looks way to complex and inefficient. If it is slow to get to speed the first 10,000 meters, it is under powered. If it is glowing at 15,000, you are way overpowered. Either way is highly inefficient for placing a 40 ton payload in orbit.

An efficient design should have boosters that can lift a good percentage more then their own weight. I believe ideally, you can get close to 20% of the launch weight into a 100K orbit.

This design I was playing with to place a 40 ton fuel can in orbit. While using Novapunch mods and asparagus staging, it has sufficient efficiency and stability to do the job.

A slightly modified design placed the same full fuel can into Mun orbit. Some monoprop fuel was needed to circularize that orbit. Note, no fuel was used from that Rocomax orange tank.

[SRV Ron]

If I don't have the SRB's, it won't even get into space, again, due to the fact that as you mentioned, it'll have to little thrust at the end.

What I do is after I drop 4-6 Engines, I turn on the SRB's. This allows it to get into space. But it handles so insanely, I can't get it lined up properly in orbit to meet up with my other piece.

Replace the SRBs with the equivalent weight in liquid fuel tanks and engines. You will gain more delta V, probably enough that you could reduce the weight by using LV-909s which will place less demand on the launch vehicle. Add bracing to stabilize them to the core tank.

I'm assuming that you are using career Mode parts for this design where Rocomax parts would be more efficient with a simpler design .

[LadyAthena]

Replace the SRBs with the equivalent weight in liquid fuel tanks and engines. You will gain more delta V, probably enough that you could reduce the weight by using LV-909s which will place less demand on the launch vehicle. Add bracing to stabilize them to the core tank.

I'm assuming that you are using career Mode parts for this design where Rocomax parts would be more efficient with a simpler design .

I am doing the campaign. I probably should of mentioned that.

[capi3101]

Next question then: how far along are you on the Tech Tree?

Johnno's given you the best advice so far if you're playing stock.

[numerobis]

SRBs have high drag, so you want them on the bottom of your ship (if at all), otherwise you'll be unstable. They also have low Isp; you generally want SRBs to be on the launch stage, helping your T30s and T45s push up extra fuel.

[grim5000]

can you post what areas of teh tech tree you have unlocked? it will make it a lot easier for people to help you.

[LadyAthena]

Actually thanks to your guy's help and input, I did manage to re make a ship. Since I didn't have those extra large fuel tanks, I just used my trio design. http://i39.tinypic.com/qrda8g.jpg

it did make it into space to 100k km much quicker than my old one, and without troubles. The only issue I'm having now is controlling it in space. I do have thrusters on it, but it still is slow to manouver. However I think that has to do with 70% of me not knowing what I'm doing when it comes to docking. As I can't even remotely start to get close to my other station section...

And here is what I have on my Research tree so far. http://i40.tinypic.com/sqp9av.jpg

Any additional help would be appreciated! (Is there a way for me to even upload my ship so you guys can download it?)

[Taki117]

This post should be deleted (I don't know how to do it)

Edited October 25, 2013 by Taki117

[Taki117]

You have everything you need to build a decent heavy lifter. 8 of the grey tanks (X200-8) make up 1 large orange tank (And proportional from there) IF you add the Skipper engine to your center stage, and set up asparagus staging on your liquid boosters (Using clustered engines) then you should be able to get to orbit without much issue.

Edit: Try adding RCS thrusters to the top and bottom of every stage, as well as the Inline reaction wheels and ASAS modules. Also make sure your RCS thruster blocks are on the same plane (if the ones up to pare 90 degrees from the front the ones on the bottom should be the same) Also, make sure your RCS are set to 4x symmetry. You don't need that much RCS fuel for docking, loose the roudified tanks and add some struts for the other stack. (Yes, moar struts). I have also included my Minmus Explorer design that uses the heavy lift system I described. (It is NOT set up for asparagus staging, though it requires it)

https://drive.google.com/file/d/0BzOU_F85Qj0YZzlYNVFza01WbWc/edit?usp=sharing

Another Edit: There are multiple file upload sites, I use Google drive.

[LadyAthena]

You have everything you need to build a decent heavy lifter. 8 of the grey tanks (X200-8) make up 1 large orange tank (And proportional from there) IF you add the Skipper engine to your center stage, and set up asparagus staging on your liquid boosters (Using clustered engines) then you should be able to get to orbit without much issue.

Edit: Try adding RCS thrusters to the top and bottom of every stage, as well as the Inline reaction wheels and ASAS modules. Also make sure your RCS thruster blocks are on the same plane (if the ones up to pare 90 degrees from the front the ones on the bottom should be the same) Also, make sure your RCS are set to 4x symmetry. You don't need that much RCS fuel for docking, loose the roudified tanks and add some struts for the other stack. (Yes, moar struts). I have also included my Minmus Explorer design that uses the heavy lift system I described. (It is NOT set up for asparagus staging, though it requires it)

https://drive.google.com/file/d/0BzOU_F85Qj0YZzlYNVFza01WbWc/edit?usp=sharing

Another Edit: There are multiple file upload sites, I use Google drive.

Thanks I'll give that a try ^.^

[Taki117]

Be sure to set up aspagus staging first (It also might need some reinforcement in places) I use KSPX for some parts so I had to replace some of the KSPX parts with Stock ones for the same effect. That design is untested, but the original design I use with great reliability. All the bits and fuel lines are there for asparagus staging, just the stage order needs modified.

(For more on asparagus staging:

)

[700NitroXpress]

You can get rid of all of the complex launch stages and just go with a 2 stage design. 1st stage uses all jet engines to lift your craft to 20,000 meters, eject, then fire an orbital stage to get your craft into orbit. If you perfect this method you can get any sized payload into orbit without asparagus staging. I do an example here when I launch my refit engines into orbit to connect to my orbital base that I later set down on Duna.