Help me get my Rockomax base off the ground

[Somtaaw]

Been poking around, lurking the forums for the past 2 weeks after picking up KSP. Learning, watching youtube videos and reading the tutorials. Been playing through career from day one, for the added "fun" of learning while doing. My logic was by learning to do it with small modules, I'd have the basis for larger... boy was I ever wrong!

When it comes to particularly small packages, I have no issues lofting. Small landers, command capsules w/ a full science suite, small- & mid-sized probes also with full suites. But when I start trying to loft anything larger, or something designed to go outside Kerbin's SOI; I start having immense problems with handling my TWR, or even just having enough fuel after hitting orbit to do anything meaningful.

This is a sample of my general rocket-ships. The design changes very little if I'm using non-Rockomax components. In this particular image, I'm running:

Sputnik probe core + Communotron 88-88

2x Z-1k batteries

PPD-12 Station Cupola

4x Gigantor XL solar arrays

FL-R1 RCS Fuel tank + 4 RCS thrusters arrayed symmetrical

2x X200-32 Fuel tanks, with 4 Docking Ports arrayed around

FL-R1 RCS Fuel tank + 4 RCS thrusters arrayed symmetrical

That's the core of a space station I'm planning to build. I'm doing career, so I don't have access to some of the parts I'd like to install, so this is merely a temporary station, serving as a HKO refuelling station. Planning to put this sucker up at 200-250km range. Total mass of this preliminary station is just south of 50t, and I plan on all future components to weigh in at approximately the same weight. Now for the loft package, which is where I particularly need the help.

Decoupler (Temporary station, and I dont have the Rockomax docking port yet, to start a modular, upgradable station at this time)

Skipper Engine

Decoupler

X200-32 Fuel Tanks

Skipper Engine

Radially mounted around the X200-32 are four (4) Rockomax X200-16's, also mounting Skipper's. Radially mounted around each X200-16, is 3 BACC SRBs. All radially mounted detachables are mounted on Hydraulic detachment manifolds. The TT-70 mounts everything too far out, and I actually never did unlock the TT-38 (and I ran out of easily obtained research). Total mass of just the lofting platform is just about bang on 175t. My RCS build aid claims that I'm pushing about 1.73 TWR with the SRBs, and 2.63 TWR after I drop the SRB's. But the ship just falls to loft higher than ~15-20km.

Now one thing that may be hurting me, I don't light my liquid fuelled engines until after I disconnect the SRB's, mostly in an effort to try and be fuel economic. The SRB's usually have no issues lofting my platforms to 10-15km range, where I detach, light my liquid fuelled engine and burn to orbit.

Edited April 23, 2014 by Somtaaw
advice obtained

[Vanamonde]

SRBs give you a quick punch up to high speed, and then quit long before you're anywhere. They're not meant to be used as a whole stage, and while it can be done, they're not good at it. Replace most of those with liquid fuel engines which don't push as hard, but push much longer, and your ship will go much farther.

That's just one suggestion off the top of my head. How about stripping off everything but the payload you want to deliver and post a pic of that? Some players might even build a launcher for it and send you the craft file.

[luizopiloto]

put some S.A.S modules on it... use mainsail instead of skyppers... start all engines at launch... also you can use some aspargus stages...

[Ambisinister]

Here's an easy suggestion: Stick on 2 layers of 6 -32 tanks with skippers with radial decouplers. Run fuel lines from the outer tanks to the inside tanks, then from the inside tanks to the centre engine. Do normal staging. Later on in the game SRBs become rather useless, unfortunately.

Also, the highest skipper engine has no fuel running to it! Remember, fuel cannot pass through decouplers.

If the above doesn't work, try emtying the fuel tanks in the station, put it up into orbit, transfer remaining fuel from booster stage into the tanks and send up a refueling craft.

Edited April 21, 2014 by Ambisinister

[Jouni]

If you want to lift 50 tonnes to orbit, the launch mass of the rocket is likely going to be at least 350 tonnes. Probably more, if the target orbit is 200-250 km instead of around 100 km.

The SRBs in KSP can't really be used in the same role as in real rockets. They are very small and burn out quickly, so heavy lifting must be done with liquid fuel engines. SRBs are somewhat useful for giving an initial boost to the rocket, allowing you to use more fuel with the main engines. This is especially important with the Skipper engines, as they are quite weak for their size.

This example rocket can almost do what you want:

It can lift the payload to a low orbit, but it runs out of fuel before reaching a 200 km orbit. Using 7 lower stage modules instead of 5 modules would probably get the job done.

The basic module of the rocket consists of two X200-32 fuel tanks and a Skipper engine. One of them is used as an upper stage. The lower stage has five such modules in a row, and each module also has two SRBs attached to it. All 15 lower stage engines are ignited at launch.

A couple of random notes: The Skipper engine between the decouplers in your rocket doesn't do anything, as it doesn't have fuel tanks attached to it. You may want to place the docking ports further away from the solar panels, to avoid breaking the panels accidentally.

[Sirrobert]

What you want is asperagus staging. That'll allow you to get much more deltaV out of the same rocket.

This should explain the concept: http://wiki.kerbalspaceprogram.com/wiki/Asparagus_staging

If you don't have fuel lines yet, remember that you can right click the top tank and empty it. That'll save alot of weight. Once it's in orbit, you can send up other rockets to refuel it

[Somtaaw]

Thanks for all the tips. I didn't even know I could send up empty, or partly empty fuel tanks to begin with. That'll save a lot of immediate weight

I've always been building vaguely similar to American Shuttle launch, liquid engine base, SRB's radial mounted. It served me well launching over my career, until I started trying to launch with Rockomax components, without having access to mainsails. Might start a whole new career just to take what I've learned and not be at year 4, and only having visited Mun, Minmus, and eve.

Danke,

[Sirrobert]

Thanks for all the tips. I didn't even know I could send up empty, or partly empty fuel tanks to begin with. That'll save a lot of immediate weight

I've always been building vaguely similar to American Shuttle launch, liquid engine base, SRB's radial mounted. It served me well launching over my career, until I started trying to launch with Rockomax components, without having access to mainsails. Might start a whole new career just to take what I've learned and not be at year 4, and only having visited Mun, Minmus, and eve.

Danke,

The time is relative

I'd suggest keeping the science you already have, no need to grind through it again.

About the tweaking (that's the draining tanks). Since .23 you can tweak alot of things. For example landing legs can be set to deployed or not deployed in the VAB, instead of just the default not deployed.

Very usefull if you want to see how far the legs will reach down, so you don't have to test that on the launchpad.

You can also tweak the max thrust engines will give (in percentage of the total max thrust). Not very usefull if you're just starting, but if you check the TWR (thrust/weight ratio) with Mechjeb, you can use that option to make sure that the TWR is the same between staging (to high and your rocket will be less efficient).

But that's advanced rocket building, not important until you want to optimize your rockets. Something to do after you mastered building regular rockets

[vetrox]

I just slapped a lifter together to try and help. I dont know how far in the career you are but you will need mainsails for this and you will need to asparagus stage it (see kerbal x)

Although A design error left the final payload with no fuel to go anywhere ( i was trying to copy your design) I didnt bother with SRB's like Jouni and has 7 parts to its lower stage (6 outer, 1 inner)

I

A couple of random notes: The Skipper engine between the decouplers in your rocket doesn't do anything, as it doesn't have fuel tanks attached to it.

Boy did i find that out the hard way. But according to KER, were the skipper on the final payload fueld. It would have 3148m/s left (minus 35 to finish my 80km circling maneuverr )

Javascript is disabled. View full album

Edited April 21, 2014 by vetrox

[cantab]

The two major problems I see with your original design:

Your second stage engines (the five Skippers at the bottom, first staging being your SRBs) are way underfuelled, as is partly evidenced by the 2.6 TWR you mentioned having after dropping the SRBs.

Your third stage engine is nonfunctional because the decoupler blocks fuel flow.

The upshot of both is that you don't have anywhere near the punch to reach orbit.

If you're OK with using some of the fuel in the station for the ascent, then you can do this quite simply. Put a Skipper right on the bottom of your station with a decoupler below. That will be your second stage. Below that put a Rockomax 16 tank, Rockomax 32 tank, and Skipper, then radially attach four more like that. You don't need decouplers for that radial attachment since all five engines are going to burn together. Job done. Add boosters if you like, or use 6-fold rather than 4-fold symmetry for the first stage, you won't need them but they'll let you keep a bit more fuel in your station once it's up there. If you have trouble placing the parts just try a few times, it can be a little finicky, or use the 70 decouplers to get some spacing.

Design by cantab314, on Flickr

In orbit and still plenty of fuel on board by cantab314, on Flickr

(I suggest adding some reaction wheels or fins, the control on this was a little iffy.)

If you want to get the station up there with its own tanks full, you've got a much tougher task considering you haven't unlocked the LFB and Mainsail. A first stage of lots of boosters, a second stage similar to the first stage of the above but maybe with 7 stacks, and a third stage of a single Skipper and a Rockomax 32 might do it.

A few other minor points. A cupola up top can make the rocket unstable on ascent, though if you want it on your station there's not much you can do. You have a lot of monopropellant (RCS fuel); unless you plan on refueling RCS-intensive ships or making big orbital changes for the station on the RCS I'd at least take off one of the big tanks. And the hydraulic detachment manifolds are heavy, try and avoid using them unless you need their extra force.

[Random Tank]

The new SRB's that were brought in via the ARM patch are quite good; nice amount of thrust (650kN) and a positively lovely ~63 second burn time! Try using some of them!

[FREEFALL1984]

Have you unlocked the ARM engines yet? for someone like me who plays on a pretty terrible craptop. The Arm engines and fuel tanks are a godsend, where I would normally require a half dozen orange tanks and a whole bunch of mainsails, along with the additional tanks to stop them overheating and a heap of struts to stitch the whole thing together, Now I can lift the same payload with just a very basic 2 stage rocket made from perhaps 20 parts and still have half my second stage fuel to spare, in fact since the ARM parts came along I've ALWAYS had about a half a giant 3.75m tank left over regardless of the payload. But if you haven't yet unlocked those parts, then consider using jet engines attached to radial small tanks and decouplers with radial intakes on the outside of the main stage, make sure you have enough jet engines to get a T/w of about 1.1 or more since when you're not moving on the pad you're engine output is lower. and once you hit about 12km then ignite the main engines and jettison the jet engines, basically for the addition of a few extra parts you've just raised your launchpad up to 12km. obviously 50 tonnes +lifter will come to about 350 tonnes + the jet engines themselves so you'll likely need about 25 jet engine modules to lift this thing and since each one comprises of 4 parts (tank, engine, intake and decoupler) you're basically adding 200 parts to the original design. But using that method i have made orbit with an 80 ton rocket, 22 tons of which was payload. and ending up with a full FL-t400 spare, and a 1:4 payload to lifter ratio is pretty good.

[Somtaaw]

Lots of advice rolling in, appreciate it. I went and "rerolled" my career, and with lessons learned on the first one, including pre-built rocket packs, the fine mechanics of orbiting, and running multiple ships on a trip instead of being a 3 year old space program without Mainsails, I now have a 20 day old with mainsails and station capability. And starting to prepare for my station again (this time with the ability to actually lift it)

Went poking around at other people's stations, and instead of cluttering up forums with another "hey how does my X look" I'll just drop them in here since it's still related to my OP (I'm just not lifting that station hub anymore). Using this guy's station concept, I took it and ran with the idea.

New Station base. 24 parts & 9t in total. Cupola, Science Lab, and the multi port docking clamps. 13 parts is the temporary power source and unmanned control capsule (to deorbit the temp power) http://i.imgur.com/JK4Zqej.png

Power Hub: 20 parts (+2 for the probe core+seperator to fly the rocket upto the station) 3 XL solar sails, 2 Z-4k batteries, and a few RCS to help give the station basic attitude adjustment.

http://i.imgur.com/qQDxTYQ.png

Fuel Hub: 34 parts (+2 for above) 2 X200-32's, with a whole lotta RCS bunkerage. 16 Junior docking ports to dock probes waiting on motherships, and my tugboat drop tanks (mentioned later)

http://i.imgur.com/c8iECUh.png

Docking Ring: 41 parts (+2). 1 Large docking ring, and 4 normal clamps. 4 Lights are aimed at each normal clamp, 1 from each cardinal point (top/bottom, left/right).

http://i.imgur.com/2kWpyb8.png

Tug - 34 parts, and only 32t. Definitely thinking I would like some advice here, I'm not a big fan of just going and taking someone else's work directly (just using their .craft file anyways), but if I can look at the image and build it myself, I'll use it because at least I understand the mechanics. 4 Nuke engines, and 4 small docking clamps for the drop tanks to increase fuel bunkerage. Also heavily loaded with RCS, since it's a tug.... it should be doing a lot of maneuvering, thus the station is well equipped to handle her fueling needs. http://i.imgur.com/jre4VIe.png

Drop Tank - 20 parts, boils down to being 2 FL-T200s, a medium rcs fuel tank (I did say my tug is planned to use lots of rcs), 8 rcs thrusters, and an RC-001S self-guidance (figured it was better to have each drop tank move from the fuel hub to each tug on its on, instead of trying to maneuver the tug to the tank) 4 OX-4L 1x6 solar panels and a Z-1k power these self-moving fuel tanks. Considering throwing a medium dock clamp behind the SGU so they can dock with small or medium clamps, but I'm still undecided at this time. http://imgur.com/oNPBmA3

[Claw]

Overall, I would say that looks like a pretty good plan. Go forth and prosper!

The tug looks okay.

- You might want to avoid angling the engines if you can unless you like it that way. You'll "waste" a bit of dV/thrust because of the angle, but if it doesn't bother you then don't worry.

- You may also want to consider adding another set of RCS thrusters to the top (for 2x the thrust power). Once your tug grabs onto something, the CoM is going to shift up quite a bit. If you don't have thrusters on the station sub-modules, then you might have a hard time getting translation without a lot of rotation. As long as your sub-modules have RCS thrusters (which it looks like most of them do), it shouldn't be a problem the way it is. I was surprised at how much just two XL Modular Girders and a few XL Solar panels (2.15 tons) wreaked havoc on my tug system. Although my tug for that station was a quite small.

[cantab]

Looks sensible enough. A few changes I'd make if it were me:

Put an antenna on the core, since that's where the science lab is. Just the low-gain one will do, I can add med- and high-gain on future modules.

Drop that funny double adapter from the power hub, it's a waste of two parts. (But then, my PC sucks so I really have to watch the part count to avoid the lag).

Not put that many docking ports on the fuel hub. Again, just part count.

Test my lighting on the docking ring on the ground. It's very easy to over-light things, which gives you a saturated view that you can't see the details in.

Put just two engines on the tug. That'll be enough for shifting stuff around in kerbin orbit, unless it's absolutely huge or you need to do something silly like completely reverse an orbit. It shouldn't need so many battries either. I'd also be concerned about the exhaust when pulling a cargo; the angled engines may be an effort to deal with that, but more reliable is to put the rear docking port much further behind the engines.

Put the second docking port on the drop tank, in case you want to refuel through it or double-stack them.

[Somtaaw]

Looks sensible enough. A few changes I'd make if it were me:

Put an antenna on the core, since that's where the science lab is. Just the low-gain one will do, I can add med- and high-gain on future modules.

Drop that funny double adapter from the power hub, it's a waste of two parts. (But then, my PC sucks so I really have to watch the part count to avoid the lag).

Not put that many docking ports on the fuel hub. Again, just part count.

Test my lighting on the docking ring on the ground. It's very easy to over-light things, which gives you a saturated view that you can't see the details in.

Put just two engines on the tug. That'll be enough for shifting stuff around in kerbin orbit, unless it's absolutely huge or you need to do something silly like completely reverse an orbit. It shouldn't need so many battries either. I'd also be concerned about the exhaust when pulling a cargo; the angled engines may be an effort to deal with that, but more reliable is to put the rear docking port much further behind the engines.

Put the second docking port on the drop tank, in case you want to refuel through it or double-stack them.

Thanks for the advice. I just directly copied as much of the linked space station as I could, so I'll drop the double adaptor. Thought it was funky, but figured better to do the direct clone, maybe there was a reason. Likewise I cloned as much of somebody's Spider-class tug (angled nukes, lander body, etc). I did test the docking ring lighting, thats when I upped it from 2 to 4 lights (didn't seem like it was enough, but maybe thats cause I was looking west towards KSC and seeing all of its lights and trying to equal it.

I figured the fuel hub docking rings (since they were tiny clamps) was ok. Most probes are pretty small, and it makes sense. Total docking capability is 2 large, 8 medium, and 16 tiny.

Could I ask what your tug looks like, image(s) by preference; if I like it I'll clone it via image replication, over the direct .craft file. I have the drop tanks self-pilotable, so if a tug needs fuels I'd swap them out. Later I'll go and design a fuel barge, which is just going to be a tug built purely around fuel transport. And I'm not sure I'd need to double stack my tug drop tanks, when I already have the space for upto 4. In any case, I'm going to switch this thread to answered, although we can continue discussions.

[Captain Sierra]

@Somtaaw,

My advice for the station is 86 about 8 of the tiny ports and slap on 4 regulars (I'd recommend doing this on the end farther from where it will attach to the station).

Some things you will learn in the future is that when docking 2.5m station parts together, it's almost universally better to use the 2.5m docking port. It's less wobbly and thus better for construction. Just be sure to include some standard docking ports places because those are what usually get put on your service craft.

Also, sometimes clustering small 1.25m engines is more powerful and efficient (not on your CPU! ) than 2.5m engines. 6 LV-T45 engines mounted as a cluster gives you 1200 thrust and vectoring. That makes a nice middle zone between a skipper and mainsail.

Regarding your tug, instead of angling the engines, you can create separation with the modular girder segment. Radially mount it then mount some fuel tanks to it. Attach engines and you're good. You also can probably get away with 2 nuclear engines since they are heavy and less engines will actually mean more dV (but you may have a bit less fuel after the rebuild so overall delta V will be slightly reduced). I would also tell you to not cover your capsule with docking ports. You'd be better off with a rockomax adapter there and a probe core if you really want the docking ports. Otherwise, you are blocking the hatch so kerbals cannot get in or out.

As you seem to have figured out, modular is key in KSP. Modular means expandability and versatility. Both of these mean you can modify and upgrade your station layout and modules rather than have to make a new station (or interplanetary ship when you get there). It fundamentally increases the lifespan of your infrastructure.

[Somtaaw]

@Sierra

Indeed, to me versatility is the new sexy. If what I'm designing can't fulfill at least two different (although possibly related roles), it's probably useless and I'll replace it as soon as I can design something better. My station will currently only expand in two directions, leaving the third free for free-flow, utility. When necessary I'll design a new multi-port connector unit, but I don't feel thats necessary at this time (perhaps if I get around to installing Kethane).

In your tug suggestions, could you perhaps show an image of what you mean? I'm actually sitting in the VAB right now, having already torn my tug apart to start its redesign