Simple Space Station - Need Help

[Wulfonce]

I'm trying to build a simple space station to start researching the Mun. I want it to consist of:

in this order...

-Forward mounted "pulling" engines mounted onto fuel tanks

-Mobile processing lab

-Solar array/communications

-Mun lander docking port

My plan is to launch these sections in 4 pieces and assemble them in Kerbin orbit, before moving the whole thing toward the Mun under it's own power.

So far I've built the engine section. This should be the heaviest piece of the station. I've had several unsuccessful attempts to get this section into kerbal orbit without burning around 80% of the fuel I intend to take with me to the Mun. I need this fuel for the lander. The obvious answer to this problem is to launch a few fuel transfer rockets, but I fear that might eat into my budget to much. I have a budget of 300k to make this happen, and I've already spent around 100k of that setting up a satellite network.

I'm under the impression that my station is designed horribly wrong. I've done this once before and I don't recall it being this much of a challenge. Maybe I'm taking to much fuel? Maybe the stations engines are overkill? maybe I have to much Mono Propellant? Hell I don't know. I'm kind of a noob at this game.

The station really only needs to be a working processing lab with fuel storage. Perhaps the Solar array section wouldn't even be necessary? I could probably just slap a bunch of panels to the outside of the lab?

Bottom line is, this station will likely be abandoned after the fact, so I really don't want to throw a lot of money at it. However, if it's built to some kind of standard, I could use to to eventually explore Minmus as well.

Here is the engine section.

It consists of:

-Liquid Fuel 360x4 tanks = 1440 (burning off about 80% of this before orbit)

-Mono Propellant 100x3 = 300

-engines 2x200 thrust = 400 (overkill?)

The bottom of the cross shape is a docking port that the processing lab will later attach to. The main engines are directally below the wide fuel tanks. Everything below the engines will be scrapped during the flight. Oh now that I think of it. Can you even transfer fuel through that scaffolding stuff? If I had a lander attached behind the processing lab, could I transfer fuel from the 2 main tanks at the front of the station, all the way to the back and into the lander?

Any advice to make this work? "When in doubt, add more boosters" doesn't seem to apply here. I'm thinking it may just be a crappy design.

and my satellite network, ready to go.

[tomf]

I am assuming you are using stock aerodynamics.

My first thoughts looking at the screenshots of your booster are that it could be made much more efficient. Just looking at the TWRs launching with 3 is pretty excessive. You should either reduce the number of SRBs firing or throttle them lower. After teh first stage it then drops to low at 1.2 and 1.1. You want to keep it at around 2 for the first 2500m/s or so of delta v.

Unless you have them for aestheitic reasons you could use the nosecones to reduce weight, they dont serve any purpose. Also do you really need all of that RCS fuel? with some practice at docking you might be able to reduce that considerably.

[WuphonsReach]

In general, stations and orbital parts should have minimal thrusters. For station parts of <= 20t, I use two or four LV-1R towards the bottom and shoot for a TWR of about 0.1-0.2 at most and maybe 500 m/s of DV. Which is just enough to make minor adjustments to the orbit.

At the bottom of your station part, you should have a docking port. Use that to dock a "tug" with larger engines and fuel tanks to move station parts from orbit to orbit (or to another orbital body). That dockable tug vessel should be used for any case where you need to do anything more then a 50-100 m/s maneuver.

[Starhawk]

Are you sure you need to launch four separate pieces?

My (painfully acquired) experience in KSP has led me to a couple of engineering principles I try to always keep in mind:

1. Less is more. (Except for struts. )

2. Keep it simple.

I find that if I try to start with the smallest, lightest, simplest thing I can think of that will do the job, I have more success. Less mass, the lightest engines I can get away with, and the fewest parts seems to work best for me. It's also cheaper.

Big things built with multiple docking ports are very flexible and hard to steer.

Until the new aerodynamics in the next update, nosecones and fairings actually hurt your performance in the stock game because they add mass and drag. Also, they cost kurrency.

I may be wrong, but it seems to me you could launch a single craft which could satisfy your mission requirements.

Hope this helps. Good luck!

[EDIT]: Yes, you can transfer fuel through the 'scaffolding stuff'. Any parts without fuel crossfeed are marked with those words in orange in their tab in the VAB. You can manually transfer fuel between any tanks that are attached to the same vessel as far as I know.

Edited January 15, 2015 by Starhawk

[Kerba Fett]

Is there a particular reason why you want the engines to pull the craft? If not, here's a ship I've used to harvest science from Minmus and the Mun for the last few career restarts. I've done minor variations, but stuck with the same basic design since it works pretty well.

The 3 man capsule give you enough crew to man the lab module and still keep someone in the capsule. (required to run the lab) This version has 4 docking ports on the fuel tank and 1 shielded port on the nose. Fuel is the same capacity as the big orange tank and the engine is a poodle for decent fuel economy.

When fully fueled in kerbins orbit it's got about 4000 dV and you will have to refuel it in LKO. A full orange tank is too heavy for a poodle to lift. If it you tweak it to half full in the VAB it's easy enough to get into orbit. I use 4 of the radial mount monopropellant tanks. It's enough to keep the lander topped up for enough dockings to harvest every biome of the Mun or Minmus.

I normally send the lander on it's own booster and transfer stage to Minmus or the Mun. I've usually got a bit of fuel left in the transfer stage so I'll dock with the mothership and transfer out any remaining fuel in the transfer stage and jettison it.

The lander design is also something I've stuck with through a few career restarts. I used a 2.5m main fuel tank to keep the COM low, still carry a decent amount of fuel and provide a nice wide landing gear base. It uses the LV909 for fuel economy and has 2 science jr and 2 goo canisters. 2 of the small radial mount monopropellant tanks are mounted on the bottom next to the engine. This lets you use lots for docking and landing assist and keeps the COM low. (important on the mun where flat spots are rare)

By the time I've harvested all the science and am ready to move on, I've usually set up a kethane mining base on the surface that I use to refuel the mothership. Stock players could send a tanker from kerbin. When you're ready to move on you just dock the lander to the nose of the ship to be in line with the COT and deactivate the lander engine.

The small ship docked is a data courier. After a number of landings and storing the data in the pod of the mothership, a small courier ship comes from kerbin to pick up the data and take it home. This way the mothership never has to go back to kerbin unless you replace it with a better one.

While this version uses 4 radial docking ports, I found 2 plus the one in the nose was enough in later versions. Still gives you room to dock habitat modules for crew comfort or refueling tankers.

It's been a while since I haven't launched one in .90 yet, but if memory serves the booster was a mainsail with 3 orange tanks and 8 basic jet engines radial mounted. Gives you a starting point to work from.

I found this setup to work quite well through a few career restarts so hopefully there are some ideas here you can use.

[KSK]

Just a quick comment. If you're comfortable getting to Minmus, I highly recommend starting there instead, since you'll need far less fuel for your lander to get down to the surface and back up to your lab. Plus you'll get more science points from exploring Minmus.

Design-wise, I don't have much to add to the rest of this thread. The one time I did this, my space station consisted of a mobile lab with a docking port on one end, a Hitchhiker module (because role-playing), and a fuel tank + engine to get the whole thing out to Minmus. A fairly simple in-line design that sits nicely on top of a booster. These days you might need to include a probe core, or somewhere to put a pilot, to give you SAS control.

I sent the space station up on one launcher, got it to Minmus and then sent the lander over separately. I didn't bother retrieving the lab at the end.