Problem with LVN's and Landing Struts

[Spaceweezle]

Hey, I just unlocked these cool engines which have just replaced 3 LV-909's, but now I have a problem both with the Couplers and a separate issue with placing some landing struts. Why do the engine couplers not cover all engines ? And how can I fix some L2 struts to this ? I wish these engines weren't so damn long.

I want the engines to maintain a central position as my final stage.

The undercarriage

[Traches]

What are you doing with it that requires 3 nukes? Engine clusters with stages below are difficult-- you can pull it off with docking ports and some finagling, but most of the time it's not worth the trouble.

[Spaceweezle]

What are you doing with it that requires 3 nukes? Engine clusters with stages below are difficult-- you can pull it off with docking ports and some finagling, but most of the time it's not worth the trouble.

Hey, I'm not sure what I'm doing with them, but I just wanted better efficiency out of my final stage. It seems I am pretty bad at making efficient burns, so I thought this will compensate nicely.

I just did a test launch and strangely one of the LVN's broke off when I de-coupled the final stage. It was actually the one with the coupler showing as attached. But wow, even two of these things are great in space, so efficient.

I'm still stuck with no landing gear as the L2's only reach half way down the engines.

[Weegee]

I would suggest mounting the LVN's radially. And for the size of payload you are moving, unless you are really impatient, 3 LVNs are not necessary. The more of them you have, you benefit less from their awesome efficiency, and only add TWR, making it move faster, which is only necessary on large ships.

To mount them radially, I would suggest using a cubic octagonal strut or a small hardpoint with a fuel tank on it, then attach the engine below it. Then run fuel lines into the radial tanks. The fuel tank is necessary, because LVNs can't be mounted radially on their own.

Also, are you landing on a planet from an atmosphere (besides the return to Kerbin)? If so, it's wise to use different engines, as LVNs have lower efficiency in atmosphere and the low thrust is bad for takeoff. And, if you're palnning to return to Kerbin, add a decoupler below the command pod, and potentially more parachutes so that there is less risk of a hard landing (especially if you are planning to land on planets with atmosphere before-hand).

Edited November 10, 2013 by Weegee

[Spaceweezle]

I would suggest mounting the LVN's radially. And for the size of payload you are moving, unless you are really impatient, 3 LVNs are not necessary. The more of them you have, you benefit less from their awesome efficiency, and only add TWR, making it move faster, which is only necessary on large ships.

To mount them radially, I would suggest using a cubic octagonal strut or a small hardpoint with a fuel tank on it, then attach the engine below it. Then run fuel lines into the radial tanks. The fuel tank is necessary, because LVNs can't be mounted radially on their own.

Also, are you landing on a planet from an atmosphere (besides the return to Kerbin)? If so, it's wise to use different engines, as LVNs have lower efficiency in atmosphere and the low thrust is bad for takeoff. And, if you're palnning to return to Kerbin, add a decoupler below the command pod, and potentially more parachutes so that there is less risk of a hard landing (especially if you are planning to land on planets with atmosphere before-hand).

Oh I see, thanks for that helpful information. There's a lot of still don't understand, so for me I rely purely on trial and error.

I'm not exactly sure which planets I will be landing on as yet, but I will probably benefit from landing struts. I think you're right about the LVN's though, maybe 3 is overkill after all. I will try as you said and maybe mount just 2 of them radially as some sort of auxiliary power. It also turns out that symmetry of engine placements has a big impact on stability. Running on the two remaining LVN's made things pretty wobbly.

[DMagic]

If you want to put landing struts just use I-beams, girders or truss segments to extend the landing legs below the engines.

As for the engine cowlings not covering some of the engines, that is because only one of them is actually connected to the decoupler below it. It's a limitation of tri-couplers and how crafts work. You can attach each decoupler directly to the engines to get around this, but you will still have a loose connection to the tri-coupler below it.

[LeFudge]

I make the occasional LVN powered lander, this thing tows some extra fuel behind it allowing it to make the trip to Duna and back with no CSM/transfer vessel

[Spaceweezle]

If you want to put landing struts just use I-beams, girders or truss segments to extend the landing legs below the engines.

As for the engine cowlings not covering some of the engines, that is because only one of them is actually connected to the decoupler below it. It's a limitation of tri-couplers and how crafts work. You can attach each decoupler directly to the engines to get around this, but you will still have a loose connection to the tri-coupler below it.

Hey, Thanks for explaining that. I am almost certain that I did place the engines and decouplers manually. I had the same issue with the LV-909's but miraculously on the launch pad, the couplers displayed properly.

I don't have access to the Beams or Girders yet, but I have tried something similar to what Weegee said, this is the result so far:

Sadly the landing struts still won't protrude enough. I might try moving the tanks higher.

@Lefudge - Haha, that's cool man. I don't even know what half of that stuff is on your ship, but it looks capable.

Edited November 10, 2013 by Spaceweezle

[LeFudge]

Make sure you have fuel lines running out from the center tank to the ones above the nukes or they'll run out of juice. And that poodle's going to ruin your efficiency (isp only 390, plus you'll just be towing around 2.5tons of dead weight), might as well get rid of it :3

[Spaceweezle]

Make sure you have fuel lines running out from the center tank to the ones above the nukes or they'll run out of juice. And that poodle's going to ruin your efficiency (isp only 390, plus you'll just be towing around 2.5tons of dead weight), might as well get rid of it :3

Hey, I put the Poodle there for Atmospheric landings, since the LVN's suck at that. I figure this is a nice balance of ISP. Also I don't have a perpendicular decoupler, so the main purpose is to land with everything intact (experiments etc) and the Poodle should be good in this instance, or so my brain tells me.

[LeFudge]

Well if your science is all on/above your command pod you could just eject everything below and parachute to safety pretty well, I think. Even if you don't have the right size decoupler, I've found myself using the smaller one in a pinch.

Also just FYI the ISP on the LVNs only drops to about 500 on the surface of Duna so they're actually a pretty good lander engine for Duna I found.

[Weegee]

Hey, Thanks for explaining that. I am almost certain that I did place the engines and decouplers manually. I had the same issue with the LV-909's but miraculously on the launch pad, the couplers displayed properly.

I don't have access to the Beams or Girders yet, but I have tried something similar to what Weegee said, this is the result so far:

~Image~

Sadly the landing struts still won't protrude enough. I might try moving the tanks higher.

For lift-off on atmospheric planets, you'd be better off with an engine that has a higher ISP at sea level. The poodle is pretty bad at sea level, with an ISP of only 270. You might want to try using an aerospike, though I'm not sure if it'll have enough thrust. Another option for landing on an atmospheric planet would be to forget the LVNs on the lander and use different engines. Then you could launch the lander on top of a transfer stage with nuclear engines, then dock with the transfer stage when you're going to leave.

The latter suggestion is probably more viable, because then the lander only needs enough fuel to land and get into orbit, and you don't need to deal with the weight of the LVNs. Also, if you are planning on atmospheric planets, you'll want to do most of your landing with parachutes, so I'd suggest adding the radial ones. In any case, it's probably a better idea to have a separate lander for atmospheres, but you'll probably have to dock with a transfer stage that you leave in orbit.

Also, you might as well put a decoupler below the command pod, because you don't need to rest to land with you on Kerbin. (Plus it'd be a bit more realistic that way ) And don't forget fuel lines to the LVNs, transferring fuel mid-flight is difficult, trust me

And if you really wanna still go with the hybrid lander, set the LVNs and the landing engine to action groups so you don't have to dump the LVNs or deactivate them manually, It'll make life easier

[Spaceweezle]

Hey guys, thanks much for all that. It's going to take me a while to comprehend though, I don't even know what half of that stuff means.

I don't understand how to work the Action groups thing, at first glance it would appear that it doesn't do anything, but the ability to set engine priorities is exactly what I was looking for. Adding Fuel lines sounds like a good idea too.

As for the cockpit decoupler, the only reason I am trying to avoid it is so I can lower my center of mass. Ultimately I wanted the landing stage to be as short as possible for the engine configuration I wish to use. I guess it might not make loads of difference, but since I don't really need it, I might as well leave it out (for now) anyways.

[DMagic]

Hey, Thanks for explaining that. I am almost certain that I did place the engines and decouplers manually. I had the same issue with the LV-909's but miraculously on the launch pad, the couplers displayed properly.

I don't have access to the Beams or Girders yet, but I have tried something similar to what Weegee said, this is the result so far:

Yeah, those multi-couplers are really tricky to use. You can search around the forums, there are a few guides about how to use them with engines and with docking ports, but there are some things they just don't work for.

I haven't played around with career mode much, but I think the medium size truss piece is available early on (the rectangular girder thing). It might be a bit ugly, but you can use a stack of those to extend the legs down below the engines.

[Weegee]

Action groups are fairly simple. First, click the action groups tab in the VAB. Then click on custom 1-10. These are represented as 1,2,3,4,5,6,7,8,9 and 0 on your keyboard. One you've selected which action group you want, just click on the part you want to set an action for (works with symmetry, so a group of engines will be set to the same action). For engines, since you'd want to be able to turn them off and back on again, select toggle engine. You can also use action groups to make deploying objects easier, such as solar panels, which it extremely helpful with stations.

Hope this helps.

[Spaceweezle]

Yeah, those multi-couplers are really tricky to use. You can search around the forums, there are a few guides about how to use them with engines and with docking ports, but there are some things they just don't work for.

I haven't played around with career mode much, but I think the medium size truss piece is available early on (the rectangular girder thing). It might be a bit ugly, but you can use a stack of those to extend the legs down below the engines.

Oh right, the Girder segment. I was thinking of using it, but I worried about having a bulk of mass around the lander and the extra drag from them. I know they don't weigh much but I think I would need at least two on each side meaning they would also obstruct some instruments, And as you said they are quite ugly lol.

@Weegee - Oh thanks buddy, that helps a lot! It's time to get technical hehe.

[SRV Ron]

The heavy nukes are only good for pushing large ships for interplanetary transfers. Stick with the much lighter LV-909 for landers. The elimination of 1.75 tons of dead mass per engine will more then offset the lower efficiently.

[sojourner]

The heavy nukes are only good for pushing large ships for interplanetary transfers. Stick with the much lighter LV-909 for landers. The elimination of 1.75 tons of dead mass per engine will more then offset the lower efficiently.

Not true. LV-N's are great for landing and take off on planets with low or no atmosphere. I have a tuna can lander with 2 LV-N's that can do a powered landing and take off from duna without refueling that masses less than 20 tons.

[700NitroXpress]

Move the tanks up and you could take out that poodle engine and instead use the smaller radially mounted engines.

[sibrit]

I've been able to get the couplers to cover 3 engines by switching to triple symmetry setting (X and Shift-X to cycle) when putting on the engines, and again for the separators, but when you add another inverted stack tri-coupler/tri-adapter it will only "connect" via one of the 3 connection points, which means you cannot do a physics warp or it'll send your ship into a spin (the 2 unconnected sides will "compress", putting the COM over to one side).

It's the only real gripe I have with the VAB.

[Spaceweezle]

Not true. LV-N's are great for landing and take off on planets with low or no atmosphere. I have a tuna can lander with 2 LV-N's that can do a powered landing and take off from duna without refueling that masses less than 20 tons.

Oh sweet! This makes me look like less of an idiot for wanting to try them.

@700NitoXpress - That's not a bad idea at all. Though the only ones I have are those tiny farty ones, hope that's enough.

@Sibrit - Oh man you certainly know your craft. That makes a lot of sense now. I must revisit the tripple-whammy configuration again and try out your method.

[700NitroXpress]

Yeah, you would need the 24-77's or the 48-7S

Otherwise, don't underestimate the power of the Mark 55 radial engines.

Get rid of the big engine on the bottom and instead mount 2 of the Mark 55 radials on the craft, you get a little more power and you'll have more clearance underneath the craft. Another suggestion, is that you could put larger fuel tanks on the LVN's and instead, flip them upside down. This way you'll have clearance and since you don't use them for landing, it would work. Even if you wanted to use them for landing, you could and then just flip the ship over and finish the landing with the radial engines.

Make sure your center of mass is low or in the middle of the ship otherwise it might flip over. You could always mount the Goo on the sides of the LVN engine's fuel tanks.

Edited November 11, 2013 by 700NitroXpress

[sojourner]

Oh sweet! This makes me look like less of an idiot for wanting to try them.

Hehe, here it is in a slightly older version of ksp. Should still work though since nothing has really changed in regards to the parts used.

http://s479.photobucket.com/user/seattle221/slideshow/Kerbal/nukelander

[Spaceweezle]

Yeah, you would need the 24-77's or the 48-7S

Otherwise, don't underestimate the power of the Mark 55 radial engines.

Get rid of the big engine on the bottom and instead mount 2 of the Mark 55 radials on the craft, you get a little more power and you'll have more clearance underneath the craft. Another suggestion, is that you could put larger fuel tanks on the LVN's and instead, flip them upside down. This way you'll have clearance and since you don't use them for landing, it would work. Even if you wanted to use them for landing, you could and then just flip the ship over and finish the landing with the radial engines.

Make sure your center of mass is low or in the middle of the ship otherwise it might flip over. You could always mount the Goo on the sides of the LVN engine's fuel tanks.

Upside down engines ? now that's some quantum stuff right there. The question is could I actually fly it ? ...

I put some 55 radials on just to get an idea of what the setup would be like, and boy are they ugly, they stick out like a sore thumb. I think it's because I'm using those steel tanks. But I'm now working on something purely diabolical hehe!

@Sojourner - That's really nice man. Though I don't recognize most of the parts you have used. I see all these parts but don't really know the applications for them just yet. I haven't given up on the LVN's, currently building a new hybrid with them, which only exceeds in falling over on the launch pad.

[capi3101]

OP: Looking at your original design, what you had going on there was a classic case of attempting to merge the stack after branching. That tends to lead to a wobbly ship (think insufficient strutting) and then if you're lucky enough to get it into orbit, something like this happens:

You can get around it by placing decouplers on the bottom of the engines, then docking ports (standard Clamp-O-Trons) below that, then a second set of docking ports below that. What happens then is that your ship will "dock" to the lower stage as soon as the physics engine releases it prior to launch. You wind up with a solid connection that way.

You've found a workaround though, so that's just something to file away for the future. You'll probably have to build the bottom part of your craft as a subassembly if you try the docking port trick (or at least the bottom part of the engine "

sandwich").

As others have suggested, you can use I-Beams to extend your lander legs to the point where they stick out below your engines. You wind up with something that looks kinda like this:

In this case I needed the extra clearance for a bottom-mounted docking port mounted on the bottom of a piece of structural fuselage. Its a design for Duna being tested on the Mün. Anyway, something like that would work with nukes. If you don't have I-beams, you can try the long girder segments that become available with Advanced MetalWorks on Tier 6 (300 pts) of the tech tree. You might also try just putting together normal girders end to end and see if that does anything for you (normal girders are, of course, Starting Tech).

One more technique for you to try in the future is this:

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Advantage here is that you wind up without those pesky LV-N shrouds. You probably don't have BZ-52s, but Tail Connectors (available with Aerodynamics on Tier 4) can do the same job if you flip them around so the flat end is facing downward (you'll have to strut the top bit), and even girders can do the job if you turn them flat against the side of the tank (girders allow fuel flow without adding fuel lines, incidentally). You might have to turn on parts clipping to get it to work (ALT-F12 to bring up the debug menu).

Anyway, there's some different techniques for you to try out. Good luck.