coming back to KSP after a year off... How do I launch this stupid thing

[Elfmaze]

Hey guys,  I had quite a while back when an update crashed all my mods and I didn't feel like getting it all working again... Unfortunately I have forgotten some basics. 

 

I know there are different aero models now.  But i can't get a fairing on this thing, its silly wide.   I've tried flipping the payload and it works a bit better but wide up front.  Any suggestions on how to get it into orbit?   Mech jeb friendly.    A new station core for my old career mode  

 

 

[Rocket In My Pocket]

Personally? I'd go for way more drag at the rear. Ie. fins. Reaction wheels wouldn't hurt either.

If you can't get a fairing around it you are just going to have to fight it the whole way up.

Can't help you as far as MechJeb, never touched the stuff. I will however, give you your first (of many I hope) "like!"

[Elfmaze]

OK I may have had a partial success... STRAIGHT UP,  to around 100K then turn and burn... hopefully it has enough thrust to circularize.  but at least I got it through the atmosphere!  I put like 15 active fins on it    

[Geonovast]

You could probably get a fairing around most of it.  Just put the fairing base at the top flipped upside down.

Personally, with stuff like this, I would use Konstruction! and weld it together in orbit.

[Elfmaze]

four hours later, SUCCESS!  stable 100k orbit! Now I just need to put a few more details on the station and get it to work as a orbital hotel for my tourist kerbals as they are waiting for different shuttles!   Thanks Guys!  I'll check out that Konstruction mod... I love building stations and apparently they have gotten much harder to launch.

[Geonovast]

Also hit up Dock Rotate here.  Very new, but awesome, mod that KSP has needed for a long time.  It will help you line up stuff more precisely than the built in Konstruction! rotation before you weld.

 

[Elfmaze]

"Final" version is parked at 100K  I might send a booster to take it to 130k,  Figure i probably need to get it there before adding modules.  But for some reason I can't relight the booster on there right now... And current booster only has enough fuel to de-orbit it self anyway.  I would say thats a wrap for the night! 

Edited March 11, 2018 by Elfmaze

[Gargamel]

Another option is to lose those docking arms for your first launch, then send them up in pairs on a "space tug" and dock them to the main structure that way.  It would greatly reduce the width of the initial payload and make it far easier to launch. 

[Spricigo]

heavy stuff in the front, drag stuff in the back.

Next time you have a payload like this consider to build the launch vehicle around it instead of bellow.

 

[Elfmaze]

I tried a Goddard rocket...  That didnt go well

I think launching the four arms on a single payload and assembling in space is the best option

[Geonovast]

32 minutes ago, Elfmaze said:

I tried a Goddard rocket...  That didnt go well

I think launching the four arms on a single payload and assembling in space is the best option

I'm pretty sure this is what @Spricigo was getting at.

 

I think I replicated your payload accurately.  I stuck a probe core, battery, reaction wheel, and panels on with a decoupler just to maintain the thing until more is attached.

It did a fairly good gravity turn.  You can see the circularization burn was just shy of 600 m/s.  Not perfect, but way better than straight up.

 

I build ships this way all the time.  Pretty much all of my heavy launchers are configured like this.  Much more stable than trying to toss a semi-wet noodle through the atmosphere. 

If you want to see some overly complicated examples, click the Dres Awareness badge in my sig.

Edited March 11, 2018 by Geonovast

[Spricigo]

yep, something like that.

 

Looking your results I'd try a asparagus setup with:

central skipper+rockomax X200-16

2x(mainsail+2xrockomax jumbo-64)

2x(twinboar+rockomax jumbo 64)

 

[Elfmaze]

3 hours ago, Geonovast said:

I think I replicated your payload accurately.  I stuck a probe core, battery, reaction wheel, and panels on with a decoupler just to maintain the thing until more is attached.

It did a fairly good gravity turn.  You can see the circularization burn was just shy of 600 m/s.  Not perfect, but way better than straight up.

 

I build ships this way all the time.  Pretty much all of my heavy launchers are configured like this.  Much more stable than trying to toss a semi-wet noodle through the atmosphere. 

If you want to see some overly complicated examples, click the Dres Awareness badge in my sig.

Wow!  incredible.   Looks like it still had plenty of delta V to send it anywhere in Kerbins SOI.   I'll have to give it a shot.   I don't know too much about reaction wheels yet.. But I think I only have a tiny one unlocked.  the big one is another two unlocks up.   I know I've had bad luck with RCS on stations before... super hard to get the CG right and they don't like to move right.   How many reaction wheels does something this size need to keep its orientation right for docking maneuvers ETC?   Looks like you just have the little one near the top docking port?

[Geonovast]

1 minute ago, Elfmaze said:

Wow!  incredible.   Looks like it still had plenty of delta V to send it anywhere in Kerbins SOI.   I'll have to give it a shot.   I don't know too much about reaction wheels yet.. But I think I only have a tiny one unlocked.  the big one is another two unlocks up.   I know I've had bad luck with RCS on stations before... super hard to get the CG right and they don't like to move right.   How many reaction wheels does something this size need to keep its orientation right for docking maneuvers ETC?   Looks like you just have the little one near the top docking port?

To clarify, this was done in Sandbox (So everything unlocked + no cost).  I almost exclusively play sandbox, but just wanted to give you an idea of how else you could do it.

The Reaction wheel was just there at the top for orientation after it's in orbit.  For stations, there's really no "minimum".  Even the smallest wheel will orient it... eventually.  You can always just stack them up too, if one isn't enough.

Usually a good idea to not put RCS on stations at all.  As you said, keeping the CoM in the right place is virtually impossible, and they just get all kinds of wobbly.  Just keep the RCS on whatever's docking with it, and shut it off as soon as you're docked.  Stations will literally shake themselves apart with RCS.

I'd be happy to float the craft file to you if you want to fire up a testing sandbox save.  I'm 99.9999% sure I used only stock parts.

[Gargamel]

10 hours ago, Geonovast said:

I'm pretty sure this is what @Spricigo was getting at

This is what makes this game great.

I would never consider this, I'm too stuck in the "It doesn't look real!" department.  I'd break the thing down, send it up in parts, and assemble it there.   But then again, I wouldn't be using trusses, each part would be a couple of hab modules, or science labs. 

Nice job with that build, not in my wheelhouse. 

 

[Elfmaze]

 

KSP you are a complex mistress....  Been working on my second module.  The solar generation and tug unit went up great. next component is my HAB unit.  Two hitchhikers and a Cupola.  I designed a similar expendable tourist ship previous to the station days that works beautifully.   But my three orange tank design just cant get that  CP much north of the CT.  Glitch,  or am I missing something?  I started with four kickbacks and escalated to the three orange... admittedly cost is getting out of control too.   Haven't tried the straddle method yet.  Hmm...   It really wants me to put two winglets on the nose cone(edit, that did bring the CP up but didn't help stability).

Edited March 12, 2018 by Elfmaze

[Harry Rhodan]

1 hour ago, Elfmaze said:

Glitch,  or am I missing something?

That blue ball does not indicate center of pressure, it indicates center of lift for wings and other dedicated lifting surfaces. It does not show body lift or drag, that's why it is mostly useless for rockets (and the rule for CoL slightly behind CoM wouldn't apply anyway because you don't rely on lift to keep the rocket in the air). The golden rule for aerodynamic stability of a rocket is to have more draggy stuff with more leverage below the center of mass than above.

[Elfmaze]

Any idea why orange tank rocket flips 1000ft up then?  

[Kryxal]

The initial fuel drain is likely from the top two outside tanks, or else from all outside tanks at the same time.  Reset fuel flow priority to have the bottom tank drain first, move the fuel duct to the top of the pair, and add some full-up delta wings to the very bottom.  You don't need the winglets for steering, you need them for drag if you go off-center, let the gimbals provide the steering.

For that matter, when do you lose the center stack?  You could probably afford to reduce the power for this rocket some, depending...

[Elfmaze]

Ok,   I'm going with glitch.   I got the thing into orbit straight up and at 80,000km I dumped the side burners and fired the main and it started spinning even in vac,  not an aero thing.  

 

EDIT: GOT IT,   the cupola is mounted upside down,  all my controls were backwards!  needed to change the control point :facepalm:

Edited March 12, 2018 by Elfmaze

[Spricigo]

1 hour ago, Elfmaze said:

Any idea why orange tank rocket flips 1000ft up then?  

yes..because it have a lot of drag in front of CoM.

 

Drag is proportional to cross-sectional area. Try to visualize where the Center of Volume of your craft is, if that is above the CoM your craft is likely to be  prone to flip.

Now, KSP drag model really hates flat surfaces and sticky bits. So things like the exposed RCS thruster, the iluminators the abrupt transition from 2,5m to 1,25m (decoupler<->cupola) and open nodes bellow engines causes a disproportionally big amount of drag that may skew the Center of Pressure away from the CoV, but is a good approximation for many cases.

 

39 minutes ago, Elfmaze said:

Ok,   I'm going with glitch.   I got the thing into orbit straight up and at 80,000km I dumped the side burners and fired the main and it started spinning even in vac,  not an aero thing

By any chance you had any trim set? [MOD]+X removes trim if that is the case.

Another possibility is that you had some asymmetry shifting the CoM away from the centreline, so you had off-center  thurst.

[Spricigo]

14 hours ago, Gargamel said:

I would never consider this, I'm too stuck in the "It doesn't look real!" department. 

reality is overrated anyway

 

But worth mentioning that the idea is not as crazy as sticking a plane to a giant fuel tank and some busters and fire it to orbit. Just to mention one real spacecraft.

[Gargamel]

6 hours ago, Spricigo said:

reality is overrated anyway

 

But worth mentioning that the idea is not as crazy as sticking a plane to a giant fuel tank and some busters and fire it to orbit. Just to mention one real spacecraft.

Made a shuttle, like they said.

It'd be fun they said.

I don't even like spaceplanes now. 

 

[davidpsummers]

On 3/10/2018 at 5:52 PM, Elfmaze said:

Hey guys,  I had quite a while back when an update crashed all my mods and I didn't feel like getting it all working again... Unfortunately I have forgotten some basics. 

 

I know there are different aero models now.  But i can't get a fairing on this thing, its silly wide.   I've tried flipping the payload and it works a bit better but wide up front.  Any suggestions on how to get it into orbit?   Mech jeb friendly.    A new station core for my old career mode  

 

 

 

Looks like it can be separated at the docking ports into 2 parts?  I would launch those separately, always helps.

Then you will have less drag in the top.

Edited March 17, 2018 by davidpsummers

[Elfmaze]

yup,  I wanted it to be as modular and up-gradable as possible if the docking ports didn't work out for what ever reason.  But using the above straddle method it has been working great.  same way I got the return pods up to orbit.   

 

This morning I got my first "Space bus" up to the station,  will really help with the 23 kerbols that want to go see Minmus and the Mun!  I didn't have all the science tech onboard the shuttle yet,  so I guess a version 2.0 will need launched at some point,  But for now I just need to drag a 6 kerbol lander with the bus to each moon and get all these tourists done and off my station!   

 

TO DO list:  Science Lab Module,   Upgrade HAB Module(I only have 8 beds and 29 Kerbols onboard the station,  even rotating three shifts of sleeping thats leaving  five Kerbols sleeping on the floor  ) ,  Upgrade Fuel/tug Module,  build MUN/Minmus tourist lander for five bodies plus a pilot 

 

Going well so Far!