LV-N what's it good for

[AbacusWizard]

6 hours ago, rkman said:

It doesn't help much with going to the Mun because you don't need much fuel anyway to go there, so the high mass of the engine offsets what you save on fuel.

 

For a single there-and-back-again trip, sure, but I do find atomic engines very useful for reusable ships (passenger transport, cargo freighters, etc.) that are going to be going to Mun (or Minmus) and back many times.

[Guest]

I've never really bothered using LV-Ns. Their efficiency is remarkable, yes, but it comes at the cost of really heavy weight and low thrust.

I don't know, but I think that the fuel I save by using nuclear engines is gained back because of the engine's weight, and all that's left is lower thrust and really expensive costs. Only disadvantages, it seems.

I can easily circumvent that by using the Skipper (best engine IMO) and more fuel. Cheaper and safer.

[WillThe84th]

They're very good for large interplanetary ships. I usually use them when I have more than one destination. (Unless I'm just flying by, in that case I use gravity assists and small engines)

They only consume liquid fuel, so you either need to use jet fuel tanks or drain all the oxidizer out of the conventional tanks, which can make your ships pretty big.

[max_creative]

I use them on my cruisers because they have a good mix of efficiency and thrust. Ions are waaaaaaaay to slow, and chemical engines would run out of fuel and cause big problems. It's never good when the ship carrying your Dres base accidentally runs out of fuel, fails the gravity asset, and crashes into the mun. Because the ships are pretty big, I use big radiators because if I don't they tend to overheat from long burns. 8 LV-N's on a Watney doesn't over heat, but 8 on a joyride mk1 does. I do test fires before sending them somewhere to check heat management.

Also, used with Thuds it makes a good way to land. I learned this from @ShadowZone's Ozymandias VIII, where he used the LV-N's to slow down, then landed horizontally with the thuds. It also makes the already nice looking 2.5 to mk3 adapters even more practical on cruisers because they have oxidizer which is used for vernors and radial engines. Space only ones can get away with SAS alone, while ones intended to land need to maneuver quickly and have vernors. 

I use them so much that even craft with a means of propulsion in orbit has at least one LV-N. 

They also make good improvised nuclear bombs.

[Terwin]

Even with their lower thrust, I suspect ion engines would get a lot more popular if you could produce their fuel with ISRU.

I use LV-N's because they are the most efficient engine that I can refuel, as such it can get me to the most places for a given fuel:payload ratio.

[Mjarf]

I ran into that exact same argument last night. Wanted to use Ion engines for my hoverbike design for my Mun base. My Mun base can't produce xenon gas, so I went with RCS thrusters instead, as it can produce monopropellant.

[AbacusWizard]

If ISRU could produce xenon gas and engines could run during timewarp, I would be using ion engines for EVERYTHING.

[Archgeek]

On 5/31/2016 at 4:43 PM, ZooNamedGames said:

Is it bad that whenever I read this thread title to myself I sing "LV-N... what it good for- HUH" like that one song that goes "War... what's it good for". XD  .

"LV-N, HUH!  What is it good for?  Interplanetary transfers, y'all!"

sayit again, now.

[ZooNamedGames]

4 minutes ago, Archgeek said:

"LV-N, HUH!  What is it good for?  Interplanetary transfers, y'all!"

sayit again, now.

LV-N, HUH! What's it good for? INTERPLANETARY TRANSFERS ya'll.

Was that what you were after  ?

[Archgeek]

1 minute ago, ZooNamedGames said:

LV-N, HUH! What's it good for? INTERPLANETARY TRANSFERS ya'll.

Was that what you were after  ?

HEH, yes, 'forgot that part was shouted.  Probably because I tend to hyper-exagerate and extend the "HUH!" bit.

[ZooNamedGames]

5 minutes ago, Archgeek said:

HEH, yes, 'forgot that part was shouted.  Probably because I tend to hyper-exagerate and extend the "HUH!" bit.

You shout all of it- that's how it's best  

[rkman]

On 7-6-2016 at 9:11 PM, Aperture Science said:

I don't know, but I think that the fuel I save by using nuclear engines is gained back because of the engine's weight, and all that's left is lower thrust and really expensive costs. Only disadvantages, it seems.

Above a certain amount of fuel (depending on several factors) you save so much fuel by using the LV-N that in the end the vessel has a lower mass.

It has been discussed and analyzed in-depth:

On 30-9-2013 at 9:07 PM, Meithan said:

Wow. Great stuff!

It seems that above 10 tons payload and 2000 m/s delta-v, the LV-N is the king pretty consistently if the required minimum TWR doesn't exceed 0.7 (Kerbin-relative), which is plenty for an interplanetary stage.

 

 

 

 

[Terwin]

Looks like anything using the large ISRU(4.25 tons + at least 1 drill for 0.75 tons) is better off with LV-N engines.

That matches pretty well with what I generally do.

[Archgeek]

1 hour ago, rkman said:

Above a certain amount of fuel (depending on several factors) you save so much fuel by using the LV-N that in the end the vessel has a lower mass.

It has been discussed and analyzed in-depth:

HEH, thank you for dredging those up.  I was waiting for those to appear and put any nascent arguments to bed.

[Guest]

1 hour ago, rkman said:

snippity snip

Can't say I was expecting that. Well played, sir, well played.

 

[Tw1]

On 09/06/2016 at 3:25 AM, ZooNamedGames said:

LV-N, HUH! What's it good for? INTERPLANETARY TRANSFERS ya'll.

Was that what you were after  ?

Literally every time I've seen this thread title this song gets in my head. 

[kBob]

4 hours ago, Tw1 said:

Literally every time I've seen this thread title this song gets in my head. 

I assure you it was quite unintentional and if you can't get the song out of your head now, I'm not to blame :).

[kBob]

Ok, I have an Eeloo window so for fun I thought let's send a probe with science (jr, goo etc.) so I make one up in two stages the first stage is some lfo tanks the probe core and science the second stage is mainsail, fuel and a few srbs.  So I'm at lko of about 100km.  I set up a node for an Eeloo Ap and see it says 5 minute burn.  Fine but I still have the mainsail attached with a very small amount of propellant left so I just dump it, run the throttle to full and back and look at my estimated burn time: 5 days (yes days not hours--that's still a day and half of human time).  Hmmm I know it was suggested here that it wasn't a great engine for probes but wow 5 days vs 5 minutes.  Ok Poodle time, or maybe skipper.  Now if I could time warp during burns it might be a different story.  Obviously I need to study some more on the trade off between efficiency and practicality.

[Terwin]

15 hours ago, kBob said:

Ok, I have an Eeloo window so for fun I thought let's send a probe with science (jr, goo etc.) so I make one up in two stages the first stage is some lfo tanks the probe core and science the second stage is mainsail, fuel and a few srbs.  So I'm at lko of about 100km.  I set up a node for an Eeloo Ap and see it says 5 minute burn.  Fine but I still have the mainsail attached with a very small amount of propellant left so I just dump it, run the throttle to full and back and look at my estimated burn time: 5 days (yes days not hours--that's still a day and half of human time).  Hmmm I know it was suggested here that it wasn't a great engine for probes but wow 5 days vs 5 minutes.  Ok Poodle time, or maybe skipper.  Now if I could time warp during burns it might be a different story.  Obviously I need to study some more on the trade off between efficiency and practicality.

Physical time-warp can cut that by a factor of 4(5 kerbin days-> 30 hours -> 7.5 hours at x4 time-warp), which sounds like an 'over night' burn with KAC set to pause a few minutes before the burn is due to finish.  Start the burn, set the alarm, go to bed and find your burn almost complete when you wake up.

[kBob]

6 hours ago, Terwin said:

Physical time-warp can cut that by a factor of 4(5 kerbin days-> 30 hours -> 7.5 hours at x4 time-warp)...

It's a nice idea but:

I gave up on my Eeloo probe it was just too expensive as this point (I'll try again later, meanwhile I've got some other windows coming up soon), also I have other things going that can't be left alone (yes KAC could and would stop them but that would defeat the purpose), really a burn that long isn't practical unless you are only doing one thing at a time; for example my science labs would be filled up and years wasted and my Duna probe would be as far out as my Eeloo probe or worse (if I turned off KAC).  I really wish warp could go faster when burning it would help a lot.

 I guess the other option would be to calculate the amount of fuel it would use and then just hyper-edit the ship with the proper amount of fuel to the proper location, but I think for now I'll just wait until I have a new window, more funds, better tech and am in a position to send a crewed expedition.

Now here's a thought how about a mod that would "time warp" a single ship basically it would just remove the ship from the game until the "burn" was done and place the ship back in at the correct location and trajectory with the proper amount of propellant removed...kind of like using hyper-edit but done automatically and without the other temptations of having hyper-edit installed.

[Zamolxes77]

Well, most of the roles have been exemplified by above posters, I'll list mine.

1. Perfect for tugs. In early and mid gameplay, I quickly create a fueling depot in orbit, with a 4 LVN tug. Large interplanetary ships or stations launch empty, dock with the tug and a second launch brings up the fuel. Whatever it doesn't fit in the newly assembled ship in orbit goes into the fuel depot. Using this tactic, my launches stay relatively low count for parts, easy to maneuver and very, very efficient, not to mention CHEAP. Every single part is 100% recoverable, including the main stage of every launch. Also every launch brings up a new heat shield, and a set of parachutes, a "landing module" if you will. Heat shield gets mounted either on top or bottom of the tug, so it can aerobreak on its return trip and gets ditched into atmosphere once target orbit has been achieved, while the chute module gets mounted at the end of the mission, to retire the tug if better parts become available. First nuclear tug used regular docking ports, but once senior port becomes available, old TUG and space stations get retired, for 100% refund.

2. Interplanetary engines for SSTO. You cannot beat 800 isp. Coupled with that the simplified logistics, you use only one type of fuel for both ASL and VAC burns and is extremely hard to justify using some other engine in place of an LVN. Once Rapiers get unlocked, SSTO receives a small fuel+oxidizer tank, just enough to get the craft from atmospheric flight to desired APO, circularization burn is executed with the LVN's.

3. Landers and science hoppers. Once you get to the Mun and try to science mine it, it becomes very important to "loiter". Each cycle of break from orbit - land - take off - make orbit - circularize eats up some 1200 dV or more (on Mun). Using LVN's is a wonderful option, that will give your science hopper an immense dV reserve, you can "hop" from biome to biome, without the need of going back into orbit after each one and wait for next shipment of fuel from Kerbin. Once that shipment of fuel is needed, well you can use the nuclear TUG you parked in orbit and bring over a very large quantity of fuel, 12,000 dV worth. On top of it, you can add extra capsules on your lander, so experiments can be repeated as many times as the number of capsules available, each capsule can contain a full copy of experiments which eliminate the need for repeat visits of the same biome. It took me for example only 3 expeditions to completely mine all 15 biomes of the Mun and completing additional 4-5 contracts, mixed in with the "hopping for science".

[NeoMorph]

I used to use clusters of LV-N on my Kerbonite Moon to Orbit tanker. On airless moons they are great for shuttling the product up to the orbiting refinery.

[foamyesque]

I just can't stand the awful TWR. My interplanetary stages generally run on Poodles and Rhinos, or sometimes Mammoths.

[WuphonsReach]

Yeah, I'm still in the "it needs more TWR" camp with regards to the LV-N.  At least the MRS addon has a quad-version of the engine which gives you a 2.5m part with four of them strapped together (for reduced part count).

[purpleivan]

For making interplanetary burns then LV-N's make a lot of sense. After all, with the time involved in getting into the transfer window, the transfer itself, braking into an orbit and most likely adjusting your plane, then an extra few minutes to make the transfer burn is small change really.

In my current main game save I have a small fleet of little nuke tugs to do the interplanetary leg work to get a bunch of other vehicles into position for mining operations at Minmus and Ike.

 

Initial fuel section headed for Ike station

 

Mining base delivered to Ike orbit

 

Habitation and docking core of station headed for Minmus

 

I even used a couple of modified tugs to haul my Eve return vehicle the Eve Redux out there

 

Then act as a return vehicle to bring Maxisa back

 

I have much love for the nukes