Why Can't I Get This Into Space?

[TheHockeyPlayer]

Okay, someone please take a look at this and tell me what you think of it:

http://cloud-2.steampowered.com/ugc/902129094390777386/B79263005A11D0F99478807B061DB6D36DBA59BC/

I'm completely blown away that I cannot get this hunk of junk into space, mostly because I'm using asparagus staging which is not working whatsoever. In 0.20 I could get an entire space station into orbit with this staging design, but now I can hardly get past a 20km sub-orbit! When I was launching the vehicle, I noticed that fuel was consumed at double the rate. Could this be a bug? Is it possible to get around it? If so, how?

[Mr Shifty]

Your stage 1 decouplers need to be moved down to stage 2.

[Dkmdlb]

And move the center mainsail engine from stage 4 to 7. That will improve your TWR and efficiency. Make sure your asparagus staging is feeding fuel to your center tank.

[Mr Shifty]

And move the center mainsail engine from stage 4 to 7. That will improve your TWR and efficiency. Make sure your asparagus staging is feeding fuel to your center tank.

I thought about this, but 1.8 is actually about the ideal TWR for a first stage; I'd move it to stage 5 or 6 for better efficiency. You want your stage TWR to average out at around 2 for the most efficient atmospheric flight, which, since TWR goes up as you burn fuel, means you have to either have a starting TWR of 1.7-1.8 or you throttle down during the stage.

[capi3101]

...odd that there's no delta-V indicated for Stage 5. Which set of engines is throttled up at that point?

[Tex_NL]

I haven't studied your ship all that much or read the suggestion thus far. I assume they are all pretty good and accurate but none have mentioned one issue you most DEFINITELY WILL encounter once you get your staging correct. The moment you stage to your 4 nuclear engines the shrouds will be ejected. In your current layout you'll will rip at least two or more engines clean off. Guaranteed!

[Mr Shifty]

...odd that there's no delta-V indicated for Stage 5. Which set of engines is throttled up at that point?

I'm guessing it has to do with how KER calculates delta-V. I'm assuming it only does delta-V calcs for stages that end with a decoupling, so it treats stage 4 and 5 as a combined stage for delta-V purposes, with 3 engines.

[troyn123]

When you fire up the stage with the nuclear rockets, does it blow up? I've had problems with the 2 panels that house the enclosed LVN crashing into the other rockets whenever I try to do more than 2x side by side...

[espm400]

I would still consider moving the centre engine from stage 4-7 and just using the throttle to manipulate your TWR.

Also, it's been a while since I've made asparagus staged rockets (I think they're ugly as sin), but with the fuel lines attached as they are (from top tank to top tank), doesn't that mean that the fuel will only transfer from the top tank to the next stage? I don't know if the fuel tree is still as it was when I built them, but I would replace the bottom two X200-32 tanks with one Jumbo 64 and re-route my fuel lines from the Jumbo 64 to the X200-32 on the following stage. That way the fuel is flowing from the bottom tank on one stage to the top tank on the next.

EDIT: Also, I just noticed while looking at your ship again, the way you've got those quad-couplers set up (quad-coupler>LV-N>decoupler>quad-coupler), with the way the part tree works you actually don't have any connection between the the decouplers and the lower quad-coupler. This can lead to some major inherent structural problems. You really should take a look at this video to see what I'm talking about. I know you're using decouplers and the video has docking ports, but it's the only way to do it with the way that Unity handles the part tree.

Edited July 26, 2013 by espm400

[lammatt]

stage 3 onward... too low twr

and stage 4 gets u 4km/s only..

it takes ~4.6km/s to reach spacee

[krenshala]

EDIT: Also, I just noticed while looking at your ship again, the way you've got those quad-couplers set up (quad-coupler>LV-N>decoupler>quad-coupler), with the way the part tree works you actually don't have any connection between the the decouplers and the lower quad-coupler. This can lead to some major inherent structural problems. You really should take a look at this video to see what I'm talking about. I know you're using decouplers and the video has docking ports, but it's the only way to do it with the way that Unity handles the part tree.

Would this same thing be why my three stage rocket isn't getting fuel to the engine? For my initial stage I've got (from the bottom up) a Mainsail connected to a TVR-200L bi-coupler, and a couple of FL-T800s that are supposed to be feeding the main engine to get the thing off the ground and (mostly) to orbit. When i try to launch it says the engine claims it is fuel starved and fails to ignite. If I throw an X200-8 tank between the bi-coupler and the engine it actually lights up, but I'm not sure if it is actually getting full fuel flow or not (only tried one launch and reverted that).

[espm400]

Okay, Opera's starting to piss me off. For the record this is the third time I've written this post (Opera crashed once, and went back a page another time).

Anyways, to put it simply, the TVR-200L only transfers fuel in one direction (if it didn't, your rocket would fire, but only draw from one tank. We'll get to that in a moment).

Based on your description, I can assume this is a reasonable facimile of your lower stage:

In the original draft I had a paragraph here explaining why I'm an idiot, but I'll spare you that. Basic point: if you didn't know the TVR-200 and the TVR-200L don't line up with each other.

Moving on. All you have to do is setup some docking ports as per the video in my previous post. That will get you a proper structural connection. Then simply add some fuel lines.

Hope this helps.

[birrhan]

Make sure fuel lines flow from the bottom of the source stack to the top of the target stack; KER doesn't account for fuel kinetics. I'll wager you're tracking fuel by right clicking on the target tank, and it's not filling once the 1st source tank (of the three in each stack) empties. And (of course) make sure they flow the correct direction.

[TheHockeyPlayer]

Thanks for your help, everyone. I decided to just scrap the design and start over.

[The Destroyer]

KER works for 0.21?

[krenshala]

Okay, Opera's starting to piss me off. For the record this is the third time I've written this post (Opera crashed once, and went back a page another time).

For me, I posted this, had to wait for moderation (first post from me ) then just a few minutes later the site went down for maintenance and this is the first time I've had a chance to check for replies since (darn day job). Took me a bit to find it again due to forum redecorating until I remembered to look in my profile.

Anyways, to put it simply, the TVR-200L only transfers fuel in one direction (if it didn't, your rocket would fire, but only draw from one tank. We'll get to that in a moment).

Based on your description, I can assume this is a reasonable facimile of your lower stage:

Except for whats above the decoupler, yes, that is exactly what I built and attempted to fly.

In the original draft I had a paragraph here explaining why I'm an idiot, but I'll spare you that. Basic point: if you didn't know the TVR-200 and the TVR-200L don't line up with each other.

Yup, the 200L is for 2.5m parts, as I discovered the hard way during construction.

Moving on. All you have to do is setup some docking ports as per the video in my previous post. That will get you a proper structural connection. Then simply add some fuel lines.

Hope this helps.

With the fuel lines, are the docking ports needed to ensure the bi-coupler thinks it can also pass fuel "upward" toward the engine (from its point of view)? Are all the multi-couplers designed to only pass fuel (or the connection) "downward" like the TVR-200L is?

I'm assuming your method of ensuring the docking ports are properly coupled is still required when using this setup.

In the end I switched from the FL-T800s to some X200-8s (same mass and fuel capacity) and that allowed me to drop both bi-couplers and launch. So, now I have one probe in a 52 day solar orbit after a 20Km Mun encounter (ran out of fuel half way through the burn to make orbit), and a second that I goofed on staging and am attempting to get to the Mun anyway (its in a Kerbin orbit that reaches about 150Km further than the Mun's orbit, but is about 75 degrees behind the Mun at its current position).

[espm400]

~snip~

With the fuel lines, are the docking ports needed to ensure the bi-coupler thinks it can also pass fuel "upward" toward the engine (from its point of view)? Are all the multi-couplers designed to only pass fuel (or the connection) "downward" like the TVR-200L is?

I'm assuming your method of ensuring the docking ports are properly coupled is still required when using this setup.

In the end I switched from the FL-T800s to some X200-8s (same mass and fuel capacity) and that allowed me to drop both bi-couplers and launch. So, now I have one probe in a 52 day solar orbit after a 20Km Mun encounter (ran out of fuel half way through the burn to make orbit), and a second that I goofed on staging and am attempting to get to the Mun anyway (its in a Kerbin orbit that reaches about 150Km further than the Mun's orbit, but is about 75 degrees behind the Mun at its current position).

The docking ports aren't required for the fuel, the fuel lines do that just fine on their own, the docking ports just make the structural connection from the fuel tank to the bi-coupler. If you take a look at this

I know, as I said the TVR-200 and 200L don't line up, but it serves to illustrate my point fairly well. Just imagine that docking ports aren't there, notice how the part tree only connects to one of the fuel tanks? It wouldn't matter if it was two TVR-200s that lined up perfectly, the bi-coupler would only connect to one of parts, leaving the other flapping in the breeze. Sure you could strut the thing, and it would probably stay in place, but it's good to know the proper way to assemble multi-port designs like this as when you start building bigger and more advanced ships, that lack of a connection can cause some serious problems and serious frustration (Side note: This is a few months back, but it took me three launches to figure out why the quad coupler with docking ports in the middle of my ship (the top was a space station module and the bottom was a tug) was loosing three of the four docking ports every time I decoupled them. Turns out, although there was a connection between all eight docking ports, the quad-coupler could only connect to one of them, leaving the other three drifting in space and my ship unable to dock. On top of that, it took a good few hours of searching to find that video with the solution).

Anyways, I'm glad you figured out a work-around and got to space today. If you need any more assistance with KSP feel free to PM me and I'll help you if I can. Just keep in mind, math is not my strong suit (I'm not bad at it, I just don't like doing it in my spare time), so don't expect me to rattle off dV numbers and the like...

Edited July 27, 2013 by espm400