Nerf the LV-N

[Wanderfound]

No, I don't mean to reduce its thrust or ISP. Nuke rockets are very efficient, and that's how it should be.

But there are two problems:

1) They're so much more efficient for interplanetary transfers that using anything else on anything except a lightweight probe is an exercise in masochism.

2) Using the LV-N is also an exercise in masochism. The burns are painfully slow, and the engine is so heavy and bulky that you're often obliged to design the craft around the LV-Ns limitations.

These facts may be relatively realistic, but they aren't fun to play.

I can easily build a small LV-N powered spaceplane that can cruise direct from KSC to Laythe. But I'd much rather be flying on RAPIERs and Aerospikes. It's just more fun. And while I'm happy enough to limit myself to no LV-N's, I also like sharing my craft with others. The non-nuke stuff just can't compete in the long-range spaceplane market.

So, how to bring back some reason to use the other high efficiency vacuum engines (KR-2L, LV-909, Poodle, Aerospike) without making the LV-N unrealistically inefficient?

Cost. Make the LV-Ns extremely expensive. Possibly move them back in the tech tree as well. Inventing a nuke rocket is not that technologically advanced, but inventing a nuke rocket that the general public is willing to let you launch is.

We don't use nuclear rockets in the real world today, and much of the reason for that is more political/environmental than technical, but that doesn't mean that those reasons aren't a real factor. So, make the cost of the LV-N reflect the expense of the PR, insurance and safety measures that would be required in order to fly one today.

The LV-N's would still be there for those that want them, but there would now be some reason apart from self-imposed handicapping to use some of the higher TWR options as well.

Edited November 27, 2014 by Wanderfound

[Bill Phil]

Or, better yet:

Lower the default Kerbin science modifier.

There's just too much in the Kerbin-Mun-Minmus system, that there's no reason to even go to other planets except money, and there's plenty of test contracts and science from x-place or planting flags on x-body to keep you afloat.

This has really been bothering me for a while... And I'm sure it's more than just me being bothered.

They should be expensive, though. Nuclear reactors are by no means cheap.

And add a very scientifically expensive pre-requisite node for nuclear reactors and nuclear fuel storage. That way it makes sense.

[Wanderfound]

Or, better yet:

Lower the default Kerbin science modifier.

There's just too much in the Kerbin-Mun-Minmus system, that there's no reason to even go to other planets except money, and there's plenty of test contracts and science from x-place or planting flags on x-body to keep you afloat.

This has really been bothering me for a while... And I'm sure it's more than just me being bothered.

They should be expensive, though. Nuclear reactors are by no means cheap.

And add a very scientifically expensive pre-requisite node for nuclear reactors and nuclear fuel storage. That way it makes sense.

That'd work for me as well, if done successfully.

Hopefully the Kerbin science nerf is coming with the added biomes of .90, but the integration of Fine Print is going to reverse that somewhat by making science available for satellite launches and aerial surveys. I don't mind people getting good tech while just futzing around in LKO; it's what I do myself these days, as the lack of interplanetary biomes makes planet-hopping primarily a sightseeing exercise (and I've already seen 'em).

I just want for there to be some reason for the existence of non-nuke vacuum rockets.

[Bill Phil]

Yeah, making nukes insanely expensive would limit their use.

But if it's too expensive, then no one would use them.

Although, reusable space tugs would counter-act that...

As they say:

"Once it's in space, it's in space."

[Rakaydos]

A high price makes uselss.

Except if you leave it in orbit as a transfer stage, or refuel it as a reusable single stage lander, or recover it for 100% of the price by landing on the runway or launchpad.

Yep. Totally useless for everything a NERVA should be used for.

If this happens, it shold be spelled out in the item description- Very expensive, good space engine. Get your money's worth out of it.

[Bill Phil]

A high price makes uselss.

Except if you leave it in orbit as a transfer stage, or refuel it as a reusable single stage lander, or recover it for 100% of the price by landing on the runway or launchpad.

Yep. Totally useless for everything a NERVA should be used for.

If this happens, it shold be spelled out in the item description- Very expensive, good space engine. Get your money's worth out of it.

Yeah. A deep space reusable tug. That's literally the most effective way to use it already. And it was a concept for NERVA.

[Wanderfound]

So: how expensive is "very expensive"?

I'm thinking of at least a x10 cost multiplier, probably more.

[Overfloater]

Maybe the LV N could have a high failure rate (explode?) if malfunctions are implemented, or a chance for crew members to die of radiation?

Because right now there's absolutely no reason for me not to use it ;D

I was a bit surprised at 1st, when i realized there's no risk involved in using LV-Ns!

Edited November 27, 2014 by Overfloater

[RainDreamer]

How about keeping it at the same price, but introduce a new fuel (nuclear engine running on LFO?) that is much more expensive? NearFuture mod gives us liquid hydrogen, for example. The fuel would make people have to think real carefully about how much they want to burn their money away. New storage tank for that special fuel will also force design change. It would be difficult to build and fly a craft efficiently with nuclear engine, but it would be more rewarding, as it should be.

[Bill Phil]

Hmm,

Let's see.

LV-N

Current Cost: 8700 Funds

I would limit my use if it were 87000.

[prophet_01]

No malfunctions please. Higher price is something that I've been thinking about as well. It seems reasonable to me. IRL Nervas were never actually used in active service, so it's not clear how pricey that would have been. I don't know how dangerous a launch failure right on the pad would be and how much safety precautions would be needed. But I doubt that hazard due to radiation can be ruled out entirely.

Potentially dangerous materials always increase the costs. I would imagine that nervas would be like that. An example for a comparable case might be hydrazin. It's an efficient fuel but, not used in many rockets today because it's srsly toxic and difficult to work with. Although that can be dealt with, it's not cost efficient with all the extra effort to avoid harm to the people involved.

[Rakaydos]

"Ok, it's a bit expensive but there's no better engine in space. Werner says it's good for a thousand years, or until you crash. No refunds."

[Laie]

So, how to bring back some reason to use the other high efficiency vacuum engines (KR-2L, LV-909, Poodle, Aerospike) without making the LV-N unrealistically inefficient?

As long as you don't touch the ISP, it will eventually be the best engine. The other parameters only change the point of entry. Making it more costly means that you need to run it for longer until you reach the point of breakeven. Make it bigger (more thrust, more weight) and it only becomes feasible if the payload is heavy enough.

But frankly, I question your choice of using an SSTO to Laythe as a benchmark. If that's no long-range, I don't know what is. An SSTO also carries a lot of dead weight through space. Long range, high payload fraction -- and you wonder why conventional engines can't compete?

Potentially dangerous materials always increase the costs.

A failed launch would have been disastrous even without nukes. Security and safety precautions were already cranked to the max -- I don't think they could have played it any more safe than they already did, even with nuclear cargo. The engine itself would probably have been quite a bit more expensive than a conventional counterpart, but compared to the total launch cost, that may still have been not all that much.

You may want to have a look at von Braun's Mars Project and some other drafts from the era to give you an idea when and where nukes would have been considered the best engines for a purpose. However, reusability played a big role in their calculations -- I have no idea if nukes would still feature so prominently if there was no reason or opportunity to reuse them.

Edited November 27, 2014 by Laie

[Wanderfound]

As long as you don't touch the ISP, it will eventually be the best engine. The other parameters only change the point of entry. Making it more costly means that you need to run it for longer until you reach the point of breakeven. Make it bigger (more thrust, more weight) and it only becomes feasible if the payload is heavy enough.

But frankly, I question your choice of using an SSTO to Laythe as a benchmark. If that's no long-range, I don't know what is. An SSTO also carries a lot of dead weight through space. Long range, high payload fraction -- and you wonder why conventional engines can't compete? IRL, Nukes would have been the obvious best choice even for going to Mars.

Even if you take out the interplanetary factor: I can fly a spaceplane KSC-Mun-KSC without refuelling, if I design it as a dedicated long-range design with big tanks and minimal engines. Stick an LV-N on and I can do it in something the size of a fighter.

In LKO the LV-Ns aren't necessary, but they're still better. A medium size (i.e. two jets, one nuke) nuke spaceplane will hit LKO with over 6,000m/s of ÃŽâ€V in the tanks.

I'm fine with LV-Ns being better at their specialist role. I just don't want the conventional rocket options to be so bad in comparison that they're useless.

[CaptRobau]

A nuclear thermal rocket is also a nuclear reactor and those are probably not cheap, so it's probably warranted to make the LV-N more expensive without having to resort to insurance reasons, etc. Something along the lines of the 3.75m engines is probably fair. And I have no problem with switching the last two engine/fuel tech nodes, so that 3.75m engines come before the LV-n, which will then be the last engine in the top tech tree branch.

[Laie]

Even if you take out the interplanetary factor: I can fly a spaceplane KSC-Mun-KSC without refuelling, if I design it as a dedicated long-range design with big tanks and minimal engines. Stick an LV-N on and I can do it in something the size of a fighter.

Key phrase is "dedicated long-range design". That is just what nukes are meant for.

I'm fine with LV-Ns being better at their specialist role. I just don't want the conventional rocket options to be so bad in comparison that they're useless.

But chemicals just can't hold the water to nukes!

I refer you to my first paragraph, that you quoted as well: without touching ISP, you can only change the point when a nuke first becomes superior. Tweaking these knobs might well mean that SSTO-to-Laythe is only possible if the SSTO is big enough to carry a nuke.

I like the "no refunds" idea. That would mean that nukes are supposed to go into space and stay there, using them on an SSTO would be kinda pointless. Rep+ to Rakaydos.

[Kegereneku]

Just a note about Isp, Thrust, and nuclear spaceplane :

As we know there's a special relation between atmospheric pressure and Isp / Thrust.

However the equation used right now by KSP isn't a very correct simplification of it.

In short : fuel consumption in varying with altitude in lieu of thrust.

This mean that engine like the LV-N should have nearly no thrust at all in any atmosphere.

Similarly all engines' thrust should vary with atmospheric pressure, including the various kind of jet-engine (theirs would also vary with speed).

With the exception of the Aerospike that should have the same thrust at all altitude (as it is the selling point of its design)

This, would be the key at balancing the LV-N as a rare space-only engine. (alternatively they could also introduce heat radiator for him in particular)

I do not know if SQUAD plan to change this, but they might if they rework the aerodynamic model.

[Frozen_Heart]

I think that they should have a higher price and be at the end of the tech tree.

LV-Ns are not a disposable engine. If a ship has them on then you should reuse that ship as much as possible!

[prophet_01]

@ kegereneku: the LVN we have now is already severely nerfed. A real nerva does not have any problems in atmosphere. The performance of it is superior to chemical engines under almost any conditions. The low atmospheric isp in ksp already is a tweak to balance the gameplay

I don't think that "no refunds" is the right approach here. The reason to not use a nuclear ssto is related to safety. I don't think there are any issues with reusabiloty, unless you have to replace the nuclear materials or parts inside the closed cycle. This is not likely to be required for many years of service time. "No refunds" would only solve one half of the issue in a good way. I don't think that LVN's should be basically banned from the SPH. Since the game handles ssto's via the refund mechanic (which is a decent aproximation) I wouldn't be ok with that step

[Wanderfound]

Key phrase is "dedicated long-range design". That is just what nukes are meant for.

But chemicals just can't hold the water to nukes!

In terms of ISP, yeah; nukes stomp all over chemical rockets. But ISP is not the only constraint on spacecraft design.

I refer you to my first paragraph, that you quoted as well: without touching ISP, you can only change the point when a nuke first becomes superior. Tweaking these knobs might well mean that SSTO-to-Laythe is only possible if the SSTO is big enough to carry a nuke.

"Big enough to carry a nuke" is not very big at all:

(ditch the VTOL and you can make that substantially smaller, too)

You don't need big even if you're going to Laythe:

And you can still do long-haul spaceplanes without nukes if you're creative with drop tanks:

Takes a bit of prep, though; that one is designed to lift its own drop tanks into orbit, but for a serious long haul flight you'd need to lift half a dozen tanks before heading off.

I like the "no refunds" idea. That would mean that nukes are supposed to go into space and stay there, using them on an SSTO would be kinda pointless. Rep+ to Rakaydos.

That'd work for me, too, especially if combined with a chunky price increase; it might return some economic viability to traditional vertical rocket launches, as well. At the moment, spaceplanes are massively overpowered from an economic point of view.

Edited November 27, 2014 by Wanderfound

[Kegereneku]

I was wondering recently whether or not making a [suggestion] for making some engine much more refund friendly than other. because realistically some engine are way harder to maintain than other, if there were built to be maintained at all.

On the matter nuclear system are the worst to maintain regularly, so "no refund" to avoid nuclear spaceplane sound a good idea to me (I would even give a penalty if nuclear material ever landed back on Kerbin)

If didn't made that thread it was because :

- you can not yet recover rocket spent fuel the way we (plan to) do it in reality.

- to me the game is not fleshed out enough yet to really worry about balance.

A lot of other parts, building upgrade, kerbal training course, tech-tree rework will certainly be done in the future. So most change of price here could turn out being meaningless.

[Laie]

"Big enough to carry a nuke" is not very big at all:

I point out which knobs are available for tweaking, and to what effect. You reply with pictures of a craft using the engine as it currently is, which shows us what? That the current LV-N is the best choice even for very small craft? You're already said so in the OP, and I don't see anyone contradicting you. No need to insist on a point that has long been ceded.

[prophet_01]

The refund argument is similar to the whole discussion we had regarding reusable ssto's. The game does not let you reuse the parts without a whole refund/rebuild cycle. That's a gameplay decision that should not be labled as a an argument for realism.

I don't think that the use of jet engines at 1,5k m/s is any more realistic. I don't want to blame anyone or tell you how to play the game, but ruling out the rusability for LVN would do that to the people who prefer to do things that way. You are not going to get realism with that if you airhog instead :/ again I'm not blaiming anyone for playing the way he likes to play it

[Wanderfound]

I was wondering recently whether or not making a [suggestion] for making some engine much more refund friendly than other. because realistically some engine are way harder to maintain than other, if there were built to be maintained at all.

On the matter nuclear system are the worst to maintain regularly, so "no refund" to avoid nuclear spaceplane sound a good idea to me (I would even give a penalty if nuclear material ever landed back on Kerbin)

If didn't made that thread it was because :

- you can not yet recover rocket spent fuel the way we (plan to) do it in reality.

- to me the game is not fleshed out enough yet to really worry about balance.

A lot of other parts, building upgrade, kerbal training course, tech-tree rework will certainly be done in the future. So most change of price here could turn out being meaningless.

Yeah, I'm not launching a campaign or demanding any sort of immediate change; just noodling about what we might want to happen in future.

The thing that actually got me thinking about this was starting to play with Scansat; those multispectral scanners are pricey enough that you can't afford to casually toss them onto disposable probes all the time. Which got me thinking about ways of improving the game balance of components without altering their ISP and TWR characteristics.

It's fine for one rocket engine to be the clearly best choice for a particular purpose, but every part should have some use and a reason for being in the game. At the moment, that doesn't seem to be the case to me.

IMO, spaceplanes and nukes are both somewhat overpowered in economic terms. Unsurprisingly, they're also the two notable places where the game goes beyond current reality and edges into near-future SF. Although there are plenty of plans for both spaceplanes and nuke rockets, there aren't actually any flying around up there.

I don't think that the two points are unconnected; paper rockets always fly better than real ones.

[King Arthur]

Rather than debating whether or how to nerf the LV-N, perhaps it is much more prudent to discuss how the LV-N can be made more realistic while staying fun to play with.

I mean let's be real, it's understood that the LV-N is currently what it is to simplify the development process of the game, but real NTRs don't run on liquid fuel and oxidizer like conventional chemical rockets. The entire premise that the LV-N is currently working on is fundamentally flawed, and no amount of tweaking will be able to ultimately address the LV-N's downfalls without fundamentally reworking it.

Let's have a solid foundation before we decide what thickness of walls we want on the house, aye?