Don't have the Nerv?

[Cpt Kerbalkrunch]

Hello to all.

Been playing this game for awhile now, and I feel like I've gotten pretty good at it. Wish I would've found this forum a year ago, though. Would've saved me a lot of frustration. But I learned a lot through trial and error, so maybe it's a good thing.

Beyond the obvious, I've learned the most important things in the game are proper launches and good orbital maneuvers. I finally feel like I've gotten them down pretty well. However, through an embarrassing amount of hours (about 1,600 thus far) I've found the Nerv useful exactly once. I had a contract to deliver a class E asteroid to Bop. Using the asteroid's own fuel to get me there seemed the obvious answer. The problem was, with Mammoths to catch and pull the rock, I was using up all its ore before I reached Bop. I redesigned the ship with 16 Nervs instead. Obviously, the ore went a lot further just converting to lf instead of lf/o. For that particular mission, it worked really well (I still cheated, though: threw on some Vectors for power: those 30 minute burns are brutal).

Beyond that, I haven't used them at all. Every screenshot and video I see shows that pretty much everyone else is using them for interplanetary burns. I'm not sure what I'm missing. A Nerv seems to me to be a rocket with the same power as a Terrier. Sure it has 2 1/2 times the fuel efficiency, but 6 times the mass at 25 times the price.

I prefer large ships with multiple crew members and single launches, so I use Terriers for the return stage, but not often for the transfer because of their power shortage. I know the Nerv's mass is offset by dropping the oxidizer, but I still don't see the trade-off.

So, what am I missing? Do you leave the transfer stage in orbit and refuel it? Seems like it would add even more time than the burns do. Plus, I think it would present problems with time-stamping (I always play career) if you re-docked new ships to it. Staging them seems like a waste of money. Terriers are cheap. I just dump 'em, and who cares?

Wow. Just saw how long this post is. Apologies. If you guys could tell me what you're doing (and how much better it is), I'd appreciate it. If everybody's doing it, their has to be a good reason.

Thanks.

[klesh]

There will be some math players that will post later with numbers that should make sense.  Essentially, use Poodles if your ship is under a certain weight, and Nerv's if it is over a certain weight.  Also, there is a point to which adding more Nervs isn't going to help.  Again, the math players should be able to better explain, but your example of 16 Nervs definitely crossed the boundary where it becomes less efficient to use them.  If I am using multiple Nervs on a big ship, I generally limit them to 4.   I throw caution to the wind, it looks like you're interested more in the numbers, so I'll let the smarties post about that.

 

[Razorforce7]

Quote

I know the Nerv's mass is offset by dropping the oxidizer, but I still don't see the trade-off.

You shouldn't use LF/O tanks (Liquid Fuel + Oxidizer) at all when using LV/N's. You have dedicated Mk1, Mk2 and Mk3 liquid fuel only tanks as you can see here
A interplanetary ship with Nervas should only have liquid fuel tanks without any oxidizer. Unless you need it to land with a secondary rocket engine at any of your destinations ofcourse.
If you carry oxidizer tanks then I'm not surprised your mising the greater benefit.
Just watch some youtube videos. I'm sure you'll see that most of the people have mostly/only liquid fuel tanks on that stage.

How you build your vessels is also a decision of your gameplay style. A terrier can get everything to any place just like the LV/N does.
It's just that with a terrier as interplanetary powerplant you'll need to scale up your rocket considerably to get the same mass to the same place.
Because of the Delta V benefit your far more likely to be able to haul your LV/N back to Kerbin where it can be recovered. In which case LV/N's are costless.

 

[Cpt Kerbalkrunch]

15 minutes ago, klesh said:

it looks like you're interested more in the numbers, so I'll let the smarties post about that.

 

Not really. Looking for any answers at all. I actually fly by feel and experience. I think the really brainy guys would laugh at the way I play. I never know my TWR or my delta-v. I just build each stage and ask myself "will this work?". Now that I've gotten better, the answer is "yes" most of the time, but I still need the occasional rescue mission.

I like to play it by ear because of the element of adventure. Flying off to Eeloo without being 100% sure you'll get back is kind of exciting. And the crazy things I've had to do to get home have really taught me how to fly. I'm not dumb enough to ignore hard numbers, though. If something is better than it's better, and I'll find a way to use it.

To your point, I really do love the Poodle. I've been trying to incorporate it more often. And 16 Nervs was nuts, right? It was a huge shipped dubbed the Atari 2600. Cuz it was going to get an asteroid and... yeah, you get it.

[Spricigo]

Nerv will give a huge amount of deltaV if you can endure the low TWR (and consequent long burn time) 

It's a tradeoff,  you can't have one without another.

 

[Cpt Kerbalkrunch]

40 minutes ago, Razorforce7 said:

You shouldn't use LF/O tanks (Liquid Fuel + Oxidizer) at all when using LV/N's. You have dedicated Mk1, Mk2 and Mk3 liquid fuel only tanks

 

Yeah, I meant the oxidizer and the dry mass they take up. Perhaps because of the weight of the Nervs it doesn't seem like much of a savings. I hadn't thought to recover them on Kerbin, though. Been awhile since I brought anything but Kerbals and science home with me. That would definitely offset the cost, so it's worth a look.

[Draalo]

You know that you can activate physical timewarp while accellerating with ALT-"," + ALT-"."?

With 4x physics warp burns last only a quarter of time.

 

NERVs are a good choice for big Motherships like:

MK3 Cockpit

MK3 Crewcabin (=20 Crew total)

MK3 Cargobay, Sciencelab etc.

MK3 Lf Tank (maybe the long one)

radial attached 2x3 NERV engines (or 4x2, depending on mass)

Attach a lander to a dockingport, throw 2 ComSat in the cargobay. Mass of the Vessel ~ 40to. - 80to.

Easy to grind Duna & Ike /w landings and safely return all crew and science back to Kerbin. For reentry you need another vessel - but: The mothership can be refueled/restocked with a new Lander/Sats and used for another trip. If you reuse the NERFs, initial costs doesnt matter.

 

Add many spare dockingports of various sizes - when you have the RTGs unlocked add a few to the mothership - ready to visit Jool and its moons then

 

(Add: NERFs doesnt have gimbal - add many reactionwheels)

Edited April 10, 2017 by Draalo

[Aegolius13]

As mentioned above, for nukes to make sense you have to be willing to put up with pretty low TWR.  I once tried an experiment to see how many nukes I'd need to match the TWR of a Rhino.  Turns out the answer was basically never.   Since they're so heavy,  adding more nukes gets into diminishing returns very quickly, while eating up the delta-v savings due to increased mass.  I try to keep the starting TWR of a nuke stage no higher than .5.

As far as cost,  the nukes themselves are not likely to save you money vs a Terrier or Poodle upper stage.  The savings,  though,  will come downstream on your rocket.   Properly deployed,  nukes will make the upper portions of your rocket significantly lighter for a given delta-v budget.  That should make it considerably cheaper to get into orbit. E.g, if you can use a Twin Boar instead of a Mammoth as a launch vehicle,  that pays for several nukes right there 

Another major advantage of nukes is reusability.  You can get pretty good results with heavily staged chemical rockets,  but only once.   The nuke's better ISP really shines on non- staged designs.  Reusing also helps defray the higher unit cost.   

Finally, they're nice on spaceplanes since you can do most (or sometimes all) of your mission on LF only. 

[klesh]

2 hours ago, Cpt Kerbalkrunch said:

Not really. Looking for any answers at all. I actually fly by feel and experience. I think the really brainy guys would laugh at the way I play. I never know my TWR or my delta-v. I just build each stage and ask myself "will this work?". Now that I've gotten better, the answer is "yes" most of the time, but I still need the occasional rescue mission.

I like to play it by ear because of the element of adventure. Flying off to Eeloo without being 100% sure you'll get back is kind of exciting. And the crazy things I've had to do to get home have really taught me how to fly. I'm not dumb enough to ignore hard numbers, though. If something is better than it's better, and I'll find a way to use it.

To your point, I really do love the Poodle. I've been trying to incorporate it more often. And 16 Nervs was nuts, right? It was a huge shipped dubbed the Atari 2600. Cuz it was going to get an asteroid and... yeah, you get it.

 

 

Try a quick and dirty recreation of your ship.  Cheat it right into Solar orbit and check out your burn times.  Try it with 16 Nervs, 8, then 4, but leave the fuel the same.  KER can spit out some numbers for you in the VAB that should be helpful as well, but seeing it in action is always good.    Now, reconstruct with a Poodle or two and see what the differences are.  You should be able to sort out where this magical point of diminishing returns with the Nervs is.   Poodle to Eloo?  Probably not unless its just a tiny probe up front.  Nervs to Duna?  Sure, if you've got some weighty behemoth.  Often times I'll use 1 Nerv with 1.25m tanks and a small little probe on top.  That can get ya almost anywhere.

 

[bewing]

3 hours ago, Cpt Kerbalkrunch said:

I prefer large ships with multiple crew members and single launches ...

... those 30 minute burns are brutal ...

It's kinda been said already regarding TWR, but these statements of yours basically rule you out as a customer for nukes.

Players who use nukes have all the time in the world to sit and watch a burn. They are also willing to design little tiny ships with 0 or 1 crew members, and lots of individual launches.

 

 

 

[Cpt Kerbalkrunch]

19 minutes ago, klesh said:

 

 

Try a quick and dirty recreation of your ship.  Cheat it right into Solar orbit and check out your burn times.  Try it with 16 Nervs, 8, then 4, but leave the fuel the same.

 

I don't use KER, but I like the idea of throwing different configurations into orbit to see what works best. Definitely fits my trial and error style.

[Cpt Kerbalkrunch]

28 minutes ago, bewing said:

It's kinda been said already regarding TWR, but these statements of yours basically rule you out as a customer for nukes.

Players who use nukes have all the time in the world to sit and watch a burn. They are also willing to design little tiny ships with 0 or 1 crew members, and lots of individual launches.

 

 

 

I kinda thought that was the case, but I'm glad to hear it from a staff member. I realize there's no "wrong" way to play the game, but I know I'm not playing the most efficient way. I purposefully play a very low-tech style without mods. I love the adventurous feel of it. I guess I'm always chasing the high of the early days when I never knew if anything was gonna work.

[Cunjo Carl]

No nuke? No worries!

As @Spricigo mentioned they've got the potential for some extremely high deltaV. This is especially the case when shedding drymass or beefing up the launcher isn't an option (SSTO, class E asteroid hauling, etc). In stock career there aren't too many situations that force you to play like that, so I've also only ever used them occasionally with a similar would-rather-not-estimate-it massive play time.

 In the end, using them winds up being a stylistic preference, and though we happen to be in the minority on this one, there's plenty of 'less optimum' solutions that wind up doing the job just as well in the same amount of play time. KSP is nicely balanced like that, which is a huge part of what makes it compelling for me. There's always 10 ways to solve a problem, and nukes happen to be a common catchall for bumping transfer deltaV. So does launching enormous asparagus monsters . Just sayin'.

Welcome to the forums, @Cpt Kerbalkrunch!

 

[Gargamel]

4 hours ago, bewing said:

I

Players who use nukes have all the time in the world to sit and watch a burn.

There is something to be said for the use of autopilots (like mechjeb) in these situations.   You plan your manuever manually, and then you let the AP fly it for you.  Especially when you have high part count ships, and that 15 minute burn in game is more like 45-60 IRL.   Then you can go eat dinner, or work or whatever during those burns, with the confidence that it will shut down when the burn is complete. 

[W. Kerman]

8 hours ago, Cpt Kerbalkrunch said:

Hello to all.

Been playing this game for awhile now, and I feel like I've gotten pretty good at it. Wish I would've found this forum a year ago, though. Would've saved me a lot of frustration. But I learned a lot through trial and error, so maybe it's a good thing.

Beyond the obvious, I've learned the most important things in the game are proper launches and good orbital maneuvers. I finally feel like I've gotten them down pretty well. However, through an embarrassing amount of hours (about 1,600 thus far) I've found the Nerv useful exactly once. I had a contract to deliver a class E asteroid to Bop. Using the asteroid's own fuel to get me there seemed the obvious answer. The problem was, with Mammoths to catch and pull the rock, I was using up all its ore before I reached Bop. I redesigned the ship with 16 Nervs instead. Obviously, the ore went a lot further just converting to lf instead of lf/o. For that particular mission, it worked really well (I still cheated, though: threw on some Vectors for power: those 30 minute burns are brutal).

Beyond that, I haven't used them at all. Every screenshot and video I see shows that pretty much everyone else is using them for interplanetary burns. I'm not sure what I'm missing. A Nerv seems to me to be a rocket with the same power as a Terrier. Sure it has 2 1/2 times the fuel efficiency, but 6 times the mass at 25 times the price.

I prefer large ships with multiple crew members and single launches, so I use Terriers for the return stage, but not often for the transfer because of their power shortage. I know the Nerv's mass is offset by dropping the oxidizer, but I still don't see the trade-off.

So, what am I missing? Do you leave the transfer stage in orbit and refuel it? Seems like it would add even more time than the burns do. Plus, I think it would present problems with time-stamping (I always play career) if you re-docked new ships to it. Staging them seems like a waste of money. Terriers are cheap. I just dump 'em, and who cares?

Wow. Just saw how long this post is. Apologies. If you guys could tell me what you're doing (and how much better it is), I'd appreciate it. If everybody's doing it, their has to be a good reason.

Thanks.

The Nerv is completely ugh if you hate long burn times. But for some missions it's indispensable, as it provides unmatched (Besides ion engines) Isp, and runs on jet fuel, which means you can ditch oxidizer all together on a plane craft.

[Zeiss Ikon]

For my own use, I like Poodles -- they're about as efficient as Terriers, but they have alternators (which is little help for long interplanetary flights, but useful if you're staying in Kerbin's SoI) and significantly more thrust.  The final stage of my Rockmaster Mod. 1 (see my post of April 9 in What Did You Do thread) uses multiple Poodles to get about 1 G with full tanks, and a good bit more when close to empty, but everything it does could be accomplished (much more slowly) with a single Poodle (and the mass savings for deleting six engines would give Even More Delta-V).  When pushing a thousand tonne asteroid, however, the extra thrust is very welcome...

[Cpt Kerbalkrunch]

2 hours ago, Zeiss Ikon said:

For my own use, I like Poodles -- they're about as efficient as Terriers, but they have alternators

I'm definitely starting to dig the Poodle again. I sort of forgot about them for awhile when I unlocked the bigger engines and I got into using Terriers radially around a central fuselage. I've started putting them on fuel shuttles for their efficiency. They can lug a ton of fuel around low g worlds like Minmus, Pol, and Bop. The alternator is a definite plus (which the Terrier lacks, as you mentioned). And compared to the Nerv, the Poodle gimbals (a huge advantage), is quite a bit lighter, has 4x the thrust, and is a whole lot cheaper. I definitely see the advantages the Nerv provides, but I think I'll continue to use it only when I really feel like I have to.