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[peskyninja]

the aerodynamic mod hugely increase difficulty, specially when combined with mechjeb

because in vanilla for now aerodynamic center can be put far back just by winglets, but with the ferram mod the other half of the rocket also have their aero pressure applied, so it is extremely easy to have an aerodynamically unstable rocket. (lift center above the gravity center)


it doesn't help that mechjeb makes its turn abruptly under the standard profile. this way you get a very high angle of attack suddenly and your rocket starts flipping.

try editing the ascent path, with a 100% curve, turn start at 1km and turn end at 60km

that works for me. also, you can start, turn early ay 70° inclination and asas all the way trough the atmosphere; less efficient but this way you keep the angle of attack alway small and will help in non getting your rocket flipping

I've found it incredibly easier to get rockets in orbit with the aerodynamic mod. I don't know if my series of failures is due to design errors or the mods but mechjeb surely haven't helped nothing by puting my rockets in a polar orbit wen I've clearly stated a "0" heading. Just made my power nodule rendevouz with my station, 15 meters  then I've realized that my RCS was no alligned properly. Pressing shift or ctrl to chenge heigth results in the whole ship rotating along the Z axis. I'll need to launch an improved version)

[forsaken1111]

the aerodynamic mod hugely increase difficulty, specially when combined with mechjeb

because in vanilla for now aerodynamic center can be put far back just by winglets, but with the ferram mod the other half of the rocket also have their aero pressure applied, so it is extremely easy to have an aerodynamically unstable rocket. (lift center above the gravity center)


it doesn't help that mechjeb makes its turn abruptly under the standard profile. this way you get a very high angle of attack suddenly and your rocket starts flipping.

try editing the ascent path, with a 100% curve, turn start at 1km and turn end at 60km

that works for me. also, you can start, turn early ay 70° inclination and asas all the way trough the atmosphere; less efficient but this way you keep the angle of attack alway small and will help in non getting your rocket flipping

I've found it incredibly easier to get rockets in orbit with the aerodynamic mod. I don't know if my series of failures is due to design errors or the mods but mechjeb surely haven't helped nothing by puting my rockets in a polar orbit wen I've clearly stated a "0" heading. Just made my power nodule rendevouz with my station, 15 meters  then I've realized that my RCS was no alligned properly. Pressing shift or ctrl to chenge heigth results in the whole ship rotating along the Z axis. I'll need to launch an improved version)

0 heading IS a polar orbit. You want a 0 inclination... You can click the button to switch between heading and inclination, but don't confuse the two.

[Starver]

The fuel line linking is critical.

Basically what it does is let you drop off dead weight as early as possible. Weight is drag and costs fuel, so you want to get rid of empty tanks and engines as soon as possible.

I sometimes have experimented with the outermost engine-bottomed stacks having further fuel-tanks (not in connected stacks, but in sliced 'rings') hanging off from radial decouplers and fuel-linked to to the ring above and the ring above (and the ring above...) and then into the outermost stack.  For an assembly that would not have been able to make the most of full-throttle anyway (for aforementioned air-resistance reasons) putting this additional weight on that slows it down is not a disadvantage if I can still full-throttle (or nearly so) the whole stack but be using the stack rings (from bottom to top) in turn, and keeping everything else topped up longer.

Drop the bottom-most ring when empty, the next bottom-most ring when that's empty, etc.  By then I've sometimes found myself in orbit[1] with almost all 'engine-bottomed tanks' still full, giving me a good burn off to whatever off-Kerbin trajectory I care to try.

As a (basic) segment-slice diagram, the following is the general plan...


        ,--centre
        |
        v

        A
  3=4=5=H=5=4=3
    4 5 H 5 4
  2=4 5 H 5 4=2
    4 5 H 5 4
  1=4-5-H-5-4=1
    ^ ^ ^ ^ ^

A          (capsule)
H <- Centre stack
^          (engine)

1, 2, 3, 4, 5 fuel tanks jetissoned off 1st..5th
= <- decoupler
- <- strut (for strength, these being radial ones but you also need ones that link circumeferencially)


Fuel-transfers (also the probably necessary SASes/etc) not shown, but are 1->2->3->4->5->H, with 4->5 and 5->H being from the bottom tank of the source to the top fuel-tank of the destination (not sure if necessary, but I've always done that, by habit).

Because of the 6-symmetry (or 8-symmetry, of traditional-thickness tanks immediately surrounding the larger sized central core), the 'stages' and fuel-links between (say) the 4-stage and the 5-stage would be via 4a, 4b, 4c... opposing pairs, to be disposed of in turn, as you might imagine, once those sectors of this current 'outer-layer' are a depleted force (this needs to be reflected in the "fuel only" rings, also, either in how you feed or how you jettison).  And if you suffer undue wobbles after a part-layer separation event (the circumference strutting between now absent outer sectors and the the (still) adjacent tanks in that 'ring' having gone), you may need to also add struts between the not-first-to-go segment stack and diagonally inwards to an inner-layer to add rigidity/non-elasticity to the structure.  (Sometimes I've managed to fit "miss one" links between non-adjacent segments either side of the segments that would be first to go, but it depends on how the rest of the structure aligns.  However, if it attaches the terminator to the next ring in, instead, then just repeat in the other direction and you get the diagonally inwards links as just described, for much the same effect.)

(Due to the sometimes highly-fragile nature of the ship, though, I tend to shut off engines, decouple then start the engines up again (powering out of the debris once I can see it's not likely to spin into an engine), for some non-atmospheric 'stagings'.)


I don't think it's as good a method as having all jettisonable fuel-stacks 'work for their supper' with their very own engines[2], arranged in layers so that you shuck off 'rings' of boosters[3] (or the simpler "asparagus" model just talked about, which sounds similar but I've not seen/tried during my rather lonesome endeavours), but if/when an economic model states that engines are at a premium while mere fuel tanks are much cheaper it could be a more cost-effective way to lift.



[1] With a judicious lateral component to the upward flight.  Although I've also experimented with "just go up!", right from my first experiments with KSP, with only solar orbits (and unclosed, solar-escape orbits) to aim for once I've gotten beyond the Mun.

[2] Also, I've had rather wide designs that sometimes do (but sometimes don't) clip the launch structure, creating imbalances either straight away or as soon as that sector of inner-rings runs out of fuel early..

[3] And, within that ring, symmetrically opposite pairs of boosters in turn, if I've edited the .craft file to get what was laid down as sixfold/eightfold symmetries to now behave as similarly aligned triplets/tetruplets of two-fold symmetric addons, for the fine control.

[peskyninja]

Spoiler (click to show/hide)

Look at that beauty! Hopefully that is the main body of the dimitri space station.

Spoiler: snip (click to show/hide)

the aerodynamic mod hugely increase difficulty, specially when combined with mechjeb

because in vanilla for now aerodynamic center can be put far back just by winglets, but with the ferram mod the other half of the rocket also have their aero pressure applied, so it is extremely easy to have an aerodynamically unstable rocket. (lift center above the gravity center)

it doesn't help that mechjeb makes its turn abruptly under the standard profile. this way you get a very high angle of attack suddenly and your rocket starts flipping.

try editing the ascent path, with a 100% curve, turn start at 1km and turn end at 60km

that works for me. also, you can start, turn early ay 70° inclination and asas all the way trough the atmosphere; less efficient but this way you keep the angle of attack alway small and will help in non getting your rocket flipping

I've found it incredibly easier to get rockets in orbit with the aerodynamic mod. I don't know if my series of failures is due to design errors or the mods but mechjeb surely haven't helped nothing by puting my rockets in a polar orbit wen I've clearly stated a "0" heading. Just made my power nodule rendevouz with my station, 15 meters  then I've realized that my RCS was no alligned properly. Pressing shift or ctrl to chenge heigth results in the whole ship rotating along the Z axis. I'll need to launch an improved version)

0 heading IS a polar orbit. You want a 0 inclination... You can click the button to switch between heading and inclination, but don't confuse the two.

Also I am mistaken, so is mechjeb. I set it up for a 0 INCLINATION.

Spoiler: Before removing engines (click to show/hide)

Edit: The Kerellen station is 1/5 finished!

[andrea]

well, I just discovered an important thing.
if your rockets tend to leave behind debris, your station should be above debris ring.

can't target it anymore...

edit: also, I am surprised at how much debris comes withing 5 kilometers from my ship.

[peskyninja]

well, I just discovered an important thing.
if your rockets tend to leave behind debris, your station should be above debris ring.

can't target it anymore...

edit: also, I am surprised at how much debris comes withing 5 kilometers from my ship.

One of my old mapping sats just hit a 2 normal grey tank and 1 orange assembly thing. The poor bastard didn't make it.

[LoSboccacc]

Spoiler (click to show/hide)

why only three of the 7 unobstructed engine are firing?

[Sean Mirrsen]

Spoiler (click to show/hide)

why only three of the 7 unobstructed engine are firing?

Because they are seven Mainsail engines. That whole thing could be lifted up by two. He'd be wasting fuel of the upper stages to air resistance if he were using all engines at once.

[alway]

Spoiler (click to show/hide)

why only three of the 7 unobstructed engine are firing?

Because they are seven Mainsail engines. That whole thing could be lifted up by two. He'd be wasting fuel of the upper stages to air resistance if he were using all engines at once.

At that altitude, yes. However, the staging setup means he is doing that the whole way; wasting fuel to gravity.

[Starver]

I'd have gone for the aforementioned (Asparagus-thingummy) set-up and throttled down, in the lower altitudes at least, for a longer burn/more fuel left over

But I don't know what sort of comparative lift efficiency there would be between throttled-down mainsails (all of them, Asparagus-like) at whatever fuel-rate they would be working vs non-mainsails doing the same Asparagus thing at full(ish) throttle and whatever rate that is.


However, I've no idea what the ultimate aim of the station is, how far up (or how far away) it's going to be placed, etc.  There could be "reasons".


A now a quick question from me (not having had a chance to try it out yet)...  If a docking module has two docking ports, lining up with two docking ports on the thing-to-be-docked-with, will it attach at both points?  And, if so, will the 'magnetism' help adjust any minor misalignment (rotational and/or translational)?

[Graknorke]

Didn't we do a test earlier on and found that the concept of "wasting fuel to air resistance" wasn't actually a thing, and it was in fact best to gun it as fast as possible?

[10ebbor10]

I'm not sure, but I think the consensus was that as long as you stay below like 1500m/s (ground level), everything is fine.

[LoSboccacc]

I just asked why 

[Sean Mirrsen]

Spoiler (click to show/hide)

why only three of the 7 unobstructed engine are firing?

Because they are seven Mainsail engines. That whole thing could be lifted up by two. He'd be wasting fuel of the upper stages to air resistance if he were using all engines at once.

At that altitude, yes. However, the staging setup means he is doing that the whole way; wasting fuel to gravity.

There's a balance to strike there. He's using the thrust of three mainsail engines - easily enough to go at double the terminal velocity - for most of the way, as it seems to be, through the atmosphere. The last stage is three tanks and one more Mainsail, which, at the altitude and speed the previous setups will get you to, can pretty much carry you to GSO by themselves, if not Mun orbit. The NERVA and another full tank he's got for orbital maneuvers will get him anywhere.

Didn't we do a test earlier on and found that the concept of "wasting fuel to air resistance" wasn't actually a thing, and it was in fact best to gun it as fast as possible?

Take a Mainsail and a single standard 3m tank, under a Mk3 capsule. Max throttle up and see how far you go. (my experiment: 28Km) Then take the same setup and swap the mainsail for the closest thing mass and Isp-wise - six of the Mark55 surface-mounted engines - throttle up and see how far it goes. (my experiment - 58Km) See the difference.

[Techhead]

If he's only using the thrust of 3 mainsails at a time, he would get more delta-V if he converted three of those boosters into drop-tanks. Simply remove three engines and add three fuel-lines. That will shave 18 tons off of the Stage-1 weight.