Nerf the LV-N

[Laie]

The entire premise that the LV-N is currently working on is fundamentally flawed,

Stuff goes in, hot stuff comes out. Quickly. Looks about right to me.

Real-life (ahem) NTRs would use hydrogen only, for it's low molecular mass and higher exhaust speed. That's quite a difference, but not fundamental.

It may also be a bit more difficult to shut down a real NTR. There's probably considerable decay heat for a while. But if we go into that direction, we also have to wonder how our chemical rockets can be restarted unlimited times.

[Red Iron Crown]

Another way to make the LV-N less of a wonder engine would be to introduce engines somewhere in the Isp gap between it and the chemicals. Something with 600s of vacuum Isp and twice the TWR of an LV-N would be pretty compelling in some scenarios. Such things can be done with heterogenous clustering now, but that's a bit cumbersome and not really useful for smaller craft.

For realism, such engines would likely have to be nuclear as well, but there's no reason we couldn't have a few variants at different points along the TWR/Isp curve.

[Darnok]

Guys changing ISP, thrust or price of LV-N won't work, but if engine would generate radiation that would cause negative effects on Kerbals and "life-support" or structure of command pods we would have this problem solved. For me LV-Ns are ok as long as they are far away from command pods, so no more tiny spaceplanes or other crafts with clipped in LV-N

[Rusty6899]

The cost needs to be severely increased. At the moment it is by far the most economical craft for almost any purpose. It may be heavy and expensive, but it will give you a much lower mass/delta v solution for a stage than any other engine in almost all circumstances, meaning that the savings on the lifter stage(s) (where the real cost comes in) are going to more than make up for the cost of the nuke. I reckon it should cost at least somewhere between 50-100k. I'm sure it would still prove economical in certain situations.

[John FX]

Hmm,

Let's see.

LV-N

Current Cost: 8700 Funds

I would limit my use if it were 87000.

When I first read the OP I thought "Oh, so about 50K then?"

Make it the price of a smaller whole launch and I`d think twice about using one but it would not stop me.

EDIT :

Another way to make the LV-N less of a wonder engine would be to introduce engines somewhere in the Isp gap between it and the chemicals. Something with 600s of vacuum Isp and twice the TWR of an LV-N would be pretty compelling in some scenarios. Such things can be done with heterogenous clustering now, but that's a bit cumbersome and not really useful for smaller craft.

For realism, such engines would likely have to be nuclear as well, but there's no reason we couldn't have a few variants at different points along the TWR/Isp curve.

I`d support this also.

As long as we get a low profile engine with 100kn as well for landers!

[Laie]

The main problem is that NTRs really are that good.

Wikipedia goes through the example of a Saturn upper stage:

chem    nuke
  13.4t    17.3t   empty weight
 120t      39t     fueled weight
 1000kN   333kN	   thrust
6700m/s   8900m/s  delta-v

The lower delta-v is because this scenarios assumes a drop-in replacement, where the dimensions remain the same -- leaving the oxidiezer at home and only carrying hydrogen saved 2/3rds of total mass, but also means that there's only comparatively little reaction mass to be expelled.

I'm aware that this is a game, so the nukes don't have to be as obviously superior as they are in real life. But it always pains me if realism is sacrified. IMO, if nukes are so overpowered that it makes bad gameplay, I'd rather have them removed entirely than dumbed down.

That said, I think a 10t engine of 250kN would be nice -- and not suitable for small craft.

[Kegereneku]

I hadn't say it earlier, but myself I don't have problem with the LV-N being the engine of choice for interplanetary travel.

If you look at the "Mars Design Reference Architecture 5.0

http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf

Nuclear Thermal Rocket is used on every transfer vehicles.

But I understand it should just not be "efficient" or worth using on a probes, as well as for Spaceplane.

opinion time, I wouldn't be against it requiring heat radiator you cannot fold for reentry/aerobreaking.

[Francois424]

In agreement with Red Iron Crown about Something with 600s of vacuum Isp and twice the TWR of an LV-N .

I would most likely only use that one, unless I was really squeezed for ISP by cutthroat fuel requirements. In my modded install, I always use the 280 thrust Nuke engine of Nucleonic's mod simply because it has more thrust and makes burns manageable without going afk (like ions).

I'd rather have them removed entirely than dumbed down.

Ouch. Imagine the additional number of parts one would have to strap to a large mission to Jool... then Imagine a mission to Keptune (future, really far planet of KSP). Would make Ion be on top of the food chain again, but man those hour-long burns.

As long as we get a low profile engine with 100kn as well for landers!

I see what you did there...

And I agree, a mostly-flat bottom engine stronger than the existing one would be nice.

Edited November 28, 2014 by Francois424

[Wanderfound]

I see what you did there...

And I agree, a mostly-flat bottom engine stronger than the existing one would be nice.

Already there; Aerospike landers.

[Red Iron Crown]

Already there; Aerospike landers.

The aerospike's short length makes it good for landers but its lack of a bottom attachment node can make axial mounting on a rocket a bit trickier than it need be, you basically need to mount the lander upside down.

[Wanderfound]

The aerospike's short length makes it good for landers but its lack of a bottom attachment node can make axial mounting on a rocket a bit trickier than it need be, you basically need to mount the lander upside down.

Or strut/girder around it.

[sdj64]

I think the main argument I would have for reducing the overpoweredness of LV-N on spaceplanes is to make it so that jets cannot get so close to orbit that the LV-N can finish the job. If you were limited to the speed of basic jets in stock KSP or playing on 6.4x or 10x scale RSS, you wouldn't be able to go with just jets and nuke, you would either have to use dual mode engines (rapiers) or carry chemical rockets as well.

Then, it would still be the engine of choice on interplanetary transfer stages (what it was designed for) and should perform better than chemical rockets for this purpose.

[Tangle]

I am fine with both the LV-Ns and jets. Also, there are mods for nerfing the jets.

However, the engine that REALLY needs nerfing is the krakendrive. It still works, right?

[beabop]

The main problem is that NTRs really are that good.

This.

We don't use nuclear thermal rockets because the public is terrified of a launch failure. We don't have nuclear-powered aircraft because the radiation would kill the crew, or the radiation shielding would make it too heavy to fly. So, maybe these two things are enough to balance nuclear rockets:

1. Crashing the LV-N on Kerbin ruins your Reputation.
   
2. Kerbaled craft need a radiation shield to use the LV-N. It's too heavy for spaceplanes. You also can't operate one near a kerbaled space station. Unless you want to kill your kerbals.
   

[Wanderfound]

This.

We don't use nuclear thermal rockets because the public is terrified of a launch failure. We don't have nuclear-powered aircraft because the radiation would kill the crew, or the radiation shielding would make it too heavy to fly. So, maybe these two things are enough to balance nuclear rockets:

1. Crashing the LV-N on Kerbin ruins your Reputation.
   
2. Kerbaled craft need a radiation shield to use the LV-N. It's too heavy for spaceplanes. You also can't operate one near a kerbaled space station. Unless you want to kill your kerbals.
   

Yup.

Yes, NTRs are very, very good (although probably not quite as good in practice as they are on paper). But we don't use them. Why not? Because (a) they're somewhat dangerous, and ( the not-entirely-accurate public perception of them is that they're very dangerous. Accurate or not, that perception is still a real limitation that should be accounted for.

At present, KSP LV-N's have the advantages of NTRs without the drawbacks. The already nerfed TWR is a partial compensation, but I don't think it's the best way to do it; all that achieves is to make them painfully slow to use. Give me a realistically high-thrust NTR, but make it expensive and don't let me casually fire it up on the KSC runway.

A triple-thrust LV-N that can't be lit within Kerbin atmosphere and can't be returned to Kerbin after reaching orbit could work.

[King Arthur]

You also can't operate one near a kerbaled space station. Unless you want to kill your kerbals.

Emphasis underline. With all due respect, I am adamantly against fear-mongering-driven perceptions along the lines of "RADIATION KILLS!!! NUKE VERY BAD!!!1!1!!1", they add no educational value and in fact encourages ignorance and lack of proper understanding of nuclear technology and its applications.

Radiation is bad, don't get me wrong, but radiation won't just kill you like a bullet out of the sky unless we're talking something severely excessive.

[Wanderfound]

Emphasis underline. With all due respect, I am adamantly against fear-mongering-driven perceptions along the lines of "RADIATION KILLS!!! NUKE VERY BAD!!!1!1!!1", they add no educational value and in fact encourages ignorance and lack of proper understanding of nuclear technology and its applications.

Radiation is bad, don't get me wrong, but radiation won't just kill you like a bullet out of the sky unless we're talking something severely excessive.

...such as loitering near the exhaust of an NTR.

Don't get me wrong; I'm about as far from anti-nuke as you can get. I used to work at a reactor, and I've published research papers using radiological techniques. My concern is primarily with keeping KSP fun, and I find the current implementation of NTRs un-fun to use.

[King Arthur]

To be clear, loitering near the exhaust of any rocket engine is going to be very bad for your health period.

Some form of radiation management should be implemented with reworking the LV-N, this is partially what I meant when I mentioned earlier in the thread that the entire premise that the LV-N is currently working on is fundamentally flawed. The LV-N as it currently is needs a far more thorough reworking for it to become a proper engine with a fun-but-still-agreeably-realistic purpose, instead of something lazy like "oh just reduce the ISP" or "oh just increase its cost".

Edited November 29, 2014 by King Arthur

[Bill Phil]

Radiation in space already isn't great for you*, so why not add more ( a tiny amount, too).

* the Apollo astronauts, despite flying through the Van Allen belts, lived fairly long lives. IE Neil Armstrong, 1930-2012.