Is the LV-N broken?

[MalfunctionM1Ke]

What I imagine when I read the Topic

Edited April 30, 2015 by MalfunctionM1Ke

[Hodo]

^I did look, and the other thread contained no poll.

Broken poll is a broken poll and that is a broken poll.

I can say that if you are using LV-Ns to get to orbit you are using them wrong. But if you are having heating issues with them in space then they are to far from a good cooling part. I have tried the wing parts as radiators and that works pretty well, but does add a lot of extra parts. Another thing I did was move them away from another heat producing part. You ideally want them connected to a part with a VERY high heat tolerance.

I may experiment with attaching the LV-N to a heat shield..... hmmmm....

[Argon]

^The nuke has already been significantly nerfed by the new tech tree as well as the liquid fuel only update, and if squad wanted to make it a big ship only part they could make it a 2.5m part, with significantly higher mass and thrust. All this new overheat mechanic has done is suppress creativity and induce lag.

-Argon

[Screeno]

Works fine for me... I notice it makes my ssto hot but, other than that... Seems the same execpt the fuel change.

[Hodo]

^The nuke has already been significantly nerfed by the new tech tree as well as the liquid fuel only update, and if squad wanted to make it a big ship only part they could make it a 2.5m part, with significantly higher mass and thrust. All this new overheat mechanic has done is suppress creativity and induce lag.

-Argon

It is not a big ship part, it is a part that just requires a bit more care to use, no more UBER single stage to anywhere LV-N craft that are smaller than a four door sedan. Now you just have to think a bit bigger and differently. Use that massive untapped potential between your ears and figure something out. Regex has given you one quick fix.

[Champ]

^The nuke has already been significantly nerfed by the new tech tree as well as the liquid fuel only update, and if squad wanted to make it a big ship only part they could make it a 2.5m part, with significantly higher mass and thrust. All this new overheat mechanic has done is suppress creativity and induce lag.

-Argon

It makes you HAVE TO imagine new ways to solve new problems. How can it suppress creativity ? I think it gives more reward to creativity, therefor it enhances creativity, not suppress it.

What you call "creativity" is "apply the same old recipe that always work, whatever the ship, whatever the purpose, whatever the destination" ? This is not creativity !

[Renegrade]

I see alot of complaining about small craft blowing up with nuclear engines, and then in the same sentance the words "unrealistic".....

...which is quite funny as there's never actually BEEN a nuclear engine in space, EVER. Some very early designs (significantly worse than the LV-N) were tested on the ground, and none since. Plus the actual usage in KSP is highly unrealistic in that NTRs generally suck if they aren't using hydrogen as a propellant, and you pretty much can't do long term storage of hydrogen that doesn't involve stupendously heavy ultra-high-pressure tanks with very, very tiny capacities.

The Apollo system and Space Shuttle system both incorporate hydrogen stages with conventional chem-burning engines (J-2 and SSME repectively), but they use low pressure tanks that just bleed off any hydrogen that evaporates, and rely on the fact that they don't have to hold the hydrogen for very long before it's consumed. Once the CSM/LM or Orbiter is in space, it's running off of a hydrazine-variant/nitrogen tetroxide system, as the fuel can't be allowed to evaporate over the upwards of 15 days of mission time, so cryo fuels are impractical.

Now compare that to a KSP mission where they're taking an NTR with hydrogen-level Isp to Eeloo for a nice five year journey..

Hmmm, do we agree that the old aerodynamic drag model was fundamentally flawed due to being based on mass? OK, so the heat model is fundamentally flawed because it doesn't take actual radiant heat into account at all and goes overboard on conduction. Convection, meh, that only happens in atmospheres and ships spend most of their time in vacuum, so it isn't that big a deal.

Maybe I take this a bit personally because I'm a firefighter so my life revolves around the mechanics of heat transfer. But in real life, radiation is by far the most important way heat moves from 1 thing to another. It's how we cook our meals, it's why fires keep us warm, and it's the driving factor in burning down houses. Radiant heat is where most of the energy goes and it moves line-of-sight at the speed of light. Conduction, OTOH, is a comparatively slow, weak process that depends on the thermal conductivity of the material the heat is trying to move through. So having parts explode from conducted heat while ignoring the effects of radiant heat is just blatantly wrong.

Buh? Radiation? That accounts for almost no heat transfer at all unless you're using a microwave (maybe a language problem here though?).

Radiation -> carried through electromagnetic radiation (heavily dominated by black body radiation which is mostly in the visible/infrared ranges - 0.3 to 1.5 micrometer wavelength). Except in the unique case of the microwave, this does almost nothing. It's the warmth you feel when sitting near a fireplace. It becomes dominant in space as the other types don't work. It does tend to happen all over the place though as it usually radiates isotropically.

Conduction -> the direct transfer of heat via direct contact. The more heat conductive a material is, the better this occurs. It's also why metal feels hotter or colder than wood in a given situation: it has high thermal conductivity and can rapidly transfer that temperature difference to your skin.

Convection -> this is really just conduction happening via gas molecules. The heat conducts or radiates into a gas particle (molecule/atom/ion/whatever it happens to be), the particle moves about with the flow, and can conduct that heat into whatever it comes into contact with. Tends to be in an upwards direction.

As a fireman, you MUST understand it better than you described. As you approach an airtight(ish) door with a fire behind it, you feel the radiative heat coming off the door (wood) and doorknob (metal) - usually nothing. If it's not so airtight, the air might be warm - convection. You feel the door - the wood is cool-ish as it's only been recently exposed to the heat and is conducting slowly. You feel the knob - OW, it burns you - it's VERY hot as it's quickly conducting the heat. There's definitely a fire behind the door!

An even simpler test is this:

1. Put your hand next to someone else's hand, with a sheet of glass in between. The heat you feel (if any) is radiation.

2. Put your hand above the other's hand. You're feeling radiation+convection now. Little or nothing.

3. Do a handshake. This is conduction+radiation (and a tiny bit of convection, perhaps). Quite warm, eh?

Also if radiation heating (and thus cooling of course) was the most effective transfer, clothing would be ineffective. Also, car radiators wouldn't work as they're a convection/conduction system (despite the name).

Radiation transfer is very fast in terms of signal speed (c/index of refraction), but low in bandwidth (so to speak). It takes a long time to transfer a given number of joules of heat. Convection is kinda in the middle, good at neither (also depends on the gas situation). Conduction is pokey-slow, but has massive heat bandwidth even through insulators..but even more through metals.

KSP IS modelling radiative heating (you can see it in the debug info) - perhaps not enough, but it is (and heat buildup is a massive problem in real life spacecraft as radiative cooling is very inefficient/ineffective).

I might not remember much from school, but I do remember that much. Also I researched it for my own game sometime later too, so I guess I've had a refresher since then..

That being said, the values should probably be looked at closely to ensure they aren't too wacky (and radiators added). Also I'd personally like it if heat management could be an issue for other engines...and better ways of tracking heat management aside from debug info.

What I imagine when I read the Topic

http://i.imgur.com/FLOrHHg.gif

Lol.. Michael Bay parakeet film?

[Randazzo]

If you're finding the LV-N heat to be unmanageable in it's current state, follow the link in my signature.

Or just click here.

[Kanddak]

As much as I love to see heat management as an important element of spacecraft design, a nuclear-thermal rocket is basically the most ridiculous possible part to create a heat problem. The basic principle of its operation is that the propellant absorbs heat from the nuclear reactor and is then expelled from the spacecraft, carrying that heat with it. The whole thing is an open-cycle cooling system.

Save the difficult heat management for the ISRU equipment for now. Give us nuclear-electric VASIMR or MPD later and we can revisit this.

[panzer1b]

Aside from the obviously biased poll, i hate to say i actually like the new nukes, just sadly we dont quite have actual radiators to take advantage of for long burns. I really like the fact that the new heat both spreads between parts and takes much longer to dissipate (and longer to build).

That said, right now without a dedicated radiator its tough to make radiators without resorting to incredible amounts of wings, enough that it makes my capital ships with their 300+ parts look liek a joke. If every nuke needs a precooler+10 wings or so, its nto a very good looking nor low part count solution. So for now im stuck with limited burn times on nukes, i guess its the only way to balance those (previously) overpowered engines. Look at the bright side though, they are the ONLY engine that wasnt nerfed to oblivion by the ISP nerfs (well ions also didnt get nerfed if u stuck to space).

[Gaarst]

Buh? Radiation? That accounts for almost no heat transfer at all unless you're using a microwave (maybe a language problem here though?).

Radiation -> carried through electromagnetic radiation (heavily dominated by black body radiation which is mostly in the visible/infrared ranges - 0.3 to 1.5 micrometer wavelength). Except in the unique case of the microwave, this does almost nothing. It's the warmth you feel when sitting near a fireplace. It becomes dominant in space as the other types don't work. It does tend to happen all over the place though as it usually radiates isotropically.

Conduction -> the direct transfer of heat via direct contact. The more heat conductive a material is, the better this occurs. It's also why metal feels hotter or colder than wood in a given situation: it has high thermal conductivity and can rapidly transfer that temperature difference to your skin.

Convection -> this is really just conduction happening via gas molecules. The heat conducts or radiates into a gas particle (molecule/atom/ion/whatever it happens to be), the particle moves about with the flow, and can conduct that heat into whatever it comes into contact with. Tends to be in an upwards direction.

As a fireman, you MUST understand it better than you described. As you approach an airtight(ish) door with a fire behind it, you feel the radiative heat coming off the door (wood) and doorknob (metal) - usually nothing. If it's not so airtight, the air might be warm - convection. You feel the door - the wood is cool-ish as it's only been recently exposed to the heat and is conducting slowly. You feel the knob - OW, it burns you - it's VERY hot as it's quickly conducting the heat. There's definitely a fire behind the door!

An even simpler test is this:

1. Put your hand next to someone else's hand, with a sheet of glass in between. The heat you feel (if any) is radiation.

2. Put your hand above the other's hand. You're feeling radiation+convection now. Little or nothing.

3. Do a handshake. This is conduction+radiation (and a tiny bit of convection, perhaps). Quite warm, eh?

Also if radiation heating (and thus cooling of course) was the most effective transfer, clothing would be ineffective. Also, car radiators wouldn't work as they're a convection/conduction system (despite the name).

Radiation transfer is very fast in terms of signal speed (c/index of refraction), but low in bandwidth (so to speak). It takes a long time to transfer a given number of joules of heat. Convection is kinda in the middle, good at neither (also depends on the gas situation). Conduction is pokey-slow, but has massive heat bandwidth even through insulators..but even more through metals.

KSP IS modelling radiative heating (you can see it in the debug info) - perhaps not enough, but it is (and heat buildup is a massive problem in real life spacecraft as radiative cooling is very inefficient/ineffective).

About radiation: blackbody radiation depends a LOT on heat difference, actually, radiated energy is proportional to the temperature to the power 4 (3x hotter > 81x more radiation !)

In your example of the handshake, the temperature difference between the hand and the air is ~10°C. Just consider a lightbulb which is 3000K: the tungsten wire radiates towards the glass which is boiling hot very soon after turning on, and lightbulbs are filled with insulating gas to prevent as much as possible conduction/convection.

Also a wooden door has quite a poor emissivity compared to a metal part so radiates way less.

My point is that in space radiation IS the main source of heat transfer when you consider high temperature differences, eg: between a rocket engine burning over 2000K and space at only a few K. And that is only truer when your realise that in space both conduction and convection are impossible as they require a material middle to transfer.

Radiation from the Sun is what gives Mercury a heat gradient of ~600K: th Sun at 5800K 55 million km away heats a whole planet by 600K

But to come back to KSP, I find it ridiculous that an engine producing so much heat does not have an integrated, efficient heat dissipation system; or even a generic part that would serve to all engines.

Heat production is badly managed in KSP 1.0. That's it.

I think reentry heat is a good thing, adding to realism, but when a part such as the drill or converter cannot run longer than 10 secs on its own or even with several solar panels, I think something's broken.

[Hanuman]

^The nuke has already been significantly nerfed by the new tech tree as well as the liquid fuel only update, and if squad wanted to make it a big ship only part they could make it a 2.5m part, with significantly higher mass and thrust. All this new overheat mechanic has done is suppress creativity and induce lag.

-Argon

It's exactly this. All the people saying "you just aren't attaching to a big enough part for cooling" aren't getting it. They already made ion drives way more powerful for gameplay sake rather than simulation. This is the same deal. If you're required to only use this engine on large ships, then even that is already messed up, seeing as how they seem to put things in to INSPIRE creativity, not detract from it.

It's been said over and over again, being so late in the tech tree, low TWR, no integral radiator to the model, no generic other radiator parts, and a myriad of other reasons say this is broken. There is simply no particularly good reason for it to be like this.

[regex]

There is simply no particularly good reason for it to be like this.

Aside from someone simply missing it during the rebalance of parts for the new heating system. Again, it's quite likely that the values were simply reduced by a set amount; the LV-N has always been hot. The next update should hopefully address this.

[Frozen_Heart]

Managed a two and a half min burn with a TWR of 0.5. In the sunlight as well. Back half of the ship is glowing even when not on thermal view. The fuel tanks overheat before the engines though.

[SkyRender]

The LV-N would be fine if 1.) it was even remotely modeled after actual nuclear rocket motor proposed design (hint: they also planned to use the same cooling systems as more traditional rocket engines did), or 2.) there were actual heat radiator parts that actually had any sort of effect. Whatever the case, as it stands, the LV-N is currently the most nerfed of all the engines thanks to how the heating system currently works.

[Starwhip]

Everyone seems to be having problems which I am not. PC slowdowns, nukes overheating, SAS malfunctions. I wonder if it's somthing with my designs?

In any case, I had made a test SSTO with an LV-N as the secondary propulsion system, and it never overheated in the six or seven minutes that it was on at full blast during circularization.

If I discover this problem later on, all I can say is that it must be a design characteristic that one must fix and/or overcome.

[Sean Mirrsen]

I aim for an LV-N powered SSTO as a matter of principle, so that it uses oxidizer only on the way up. In space, and returning to the planet, it will use only LF.

So far I have a pretty good design, even if it's not particularly impressive.

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[adsii1970]

A poll is a good idea but your is heavily biased. Change the wording.

We need radiators to deal with heat.

I'm actually working on the model now. What I envision (and if it comes out like I want it to) is something that must be deployed and is the opposite of a solar panel - it actively attempts to steer itself away from sunlight! I have thought about requiring it to use mono-propellant as a refrigerant and a small electrical charge (for compressors and other related items) in order to function.

If someone wants to help with the scripting and animation, I would appreciate it...

[Sean Mirrsen]

I'm actually working on the model now. What I envision (and if it comes out like I want it to) is something that must be deployed and is the opposite of a solar panel - it actively attempts to steer itself away from sunlight! I have thought about requiring it to use mono-propellant as a refrigerant and a small electrical charge (for compressors and other related items) in order to function.

If someone wants to help with the scripting and animation, I would appreciate it...

You might not need to. Nertea, the creator of the Near Future Technologies pack (as well as Station Parts Expansion and the MkIV Spaceplane Set), has working radiators that behave exactly like that in his Near Future Electrical mod. He's in the process of updating the mod for 1.0. If you still want to go through with your own version, he'd probably be a good person to ask for advice on it.

[adsii1970]

You might not need to. Nertea, the creator of the Near Future Technologies pack (as well as Station Parts Expansion and the MkIV Spaceplane Set), has working radiators that behave exactly like that in his Near Future Electrical mod. He's in the process of updating the mod for 1.0. If you still want to go through with your own version, he'd probably be a good person to ask for advice on it.

Nope - I am ALL about not reinventing the wheel! Thanks for letting me know about the mod.

[Brotoro]

If you want the nukes (with the new tendency to overheat in space) to survive, you need to attach them to something that can draw off the heat from the nukes. This is going to limit how you can put a nuclear engine into your design, yes. So, you can:

a) Connect the nuke directly to a large tank, or

Connect the nuke to other structure that can draw off the heat

Then, especially if you want to make a loooong interplanetary burn, you need to make sure that the parts the nuke are connected to are not going to overheat before your long burn gets done. This can be done by:

a) Making sure the parts have enough thermal mass to absorb the heat generated during the burn.

This is why you must use a BIG tank. Also, keep in mind that as you use fuel the thermal mass of your tank will go down...so just because your nuke can run for 5 minutes when the tank is full, it will NOT be able to run that long when the tank is nearly empty. (So beware: test your design with the tanks nearly empty as well as full to be sure you can get home.) So you may end up having to bring along more fuel than you actually need for the mission just so the ship still has enough thermal mass to safely make your return burns. Yes, it's inefficient.

Also, if you have constructed a large ship in orbit, the heat is NOT going to transfer through the docking ports well (whereas it WOULD if you made the ship pre-docked in the VAB; this inconsistent behavior must be is a bug). So beware.

or, you can add enough parts to your ship that are able to radiate the heat away faster than the nukes create the heat.

This may require that you either spam lots of parts on as radiators, or it may require that you run the nukes at less than full throttle (making your looong interplanetary burns even longer). This is where proper radiator parts would be useful...but we don't have those in stock.

[Frozen_Heart]

whereas it WOULD if you made the ship pre-docked in the VAB

I've tested docking ports that are connected in the VAB. They insulate almost all the heat then as well.

[Bill Phil]

Actually, this pic shows how messed up the heat system is in KSP. That central tank being bathed in fire along both sides should be exploding instantly. Tractor/puller spaceships are totally unrealistic and should not work. That to me is a bigger problem than the LV-Ns overheating from use.

It doesn't explode instantly because it has decent thermal mass. As it should​ be, being a fuel tank with insulation. Not to mention only a little bit of the sides are getting heated. And it exploding is equally unrealistic. It would either melt or vaporize.

Tractors are very realistic and more efficient when it comes structural mass.

[Brotoro]

I've tested docking ports that are connected in the VAB. They insulate almost all the heat then as well.

Yes? OK...I was basing that warning upon tests posted by another poster (with pictures). I wonder what the difference was in his case?

- - - Updated - - -

...Tractors are very realistic and more efficient when it comes structural mass.

Tractors are mainly important in KSP because Squad hasn't given us a way to strut our stuff in orbit. If I could build rigid payloads, I'd be pushing more of them. If I have to move a noodle, I'm going to pull it.

[Bill Phil]

Tractors are mainly important in KSP because Squad hasn't given us a way to strut our stuff in orbit. If I could build rigid payloads, I'd be pushing more of them. If I have to move a noodle, I'm going to pull it.

Well... IRL struts have mass.

And a "noodle" ship could be more efficient than a rigid ship in instances where moving large payloads from one place to another is needed.