[1.12.x] Kerbal Atomics: fancy nuclear engines! (January 22, 2022)

[intelliCom]

On 5/4/2021 at 1:28 AM, lemon cup said:

These nuclear engines very much dabble in how real NTRs operate (as you can see in the posts above). Their main source of cooling is actually the cryogenic liquid hydrogen flowing over the reactor vanes! Mode of operation seems funky at first but makes sense if you think about it. Here is a quick rundown:

1. Deploy radiators. Make sure they are powered and cooling.
2. Right click engine and manually set Reactor Throttle to roughly 10%.. Any higher and the reactor will rapidly try to melt.
3. Activate Reactor. Notice heat values will steadily start to climb, your radiators are providing a modest heat sink for now but before long they will be saturated.
4. Set your main engine throttle to 100% . Right click the engine, Activate Engine (or activate via staging). Now you can see your reactor starts to quickly cool down thanks to the superchilled propellant coursing through it.
5. Isp and thrust are currently crummy, because the reactor is throttled way down and not generating much heat. Slowly throttle the reactor up to 100%. 
6. You are now NTR-ing.

To safely shutdown, deactivate the reactor before you cut engine throttle. This will automatically shut down your engine and therefore stop propellant flow. This is where your radiators come back in - they will gradually whick away the remaining heat in the reactor core. Coast to destination.

OH, also make sure you are in space during all this, NTRs don't do much in the atmosphere.

Just an update on my experience with NTRs: I've managed to use your process to operate a "Liberator" rocket motor.

Firstly, The ISP and thrust are apparently always going to be crummy for a short time after the engine's activation, so some Delta-V ends up being wasted. Is this avoidable in some way?

Secondly, on cooling down the engine after shut-down, the radiators do successfully whick away some of the heat, but there's still some heat left over that manages to wear away at the reactor core. I am currently using 12 XR-500 radiators (Total heat rejection of about 6000 kW when reactor is in use.) Do I just need more radiators, or should it perhaps be best to slowly throttle down the engine to give the radiators more leeway to get rid of the heat?

Edited May 15, 2021 by intelliCom

[lemon cup]

32 minutes ago, intelliCom said:

Just an update on my experience with NTRs: I've managed to use your process to operate a "Liberator" rocket motor.

Firstly, The ISP and thrust are apparently always going to be crummy for a short time after the engine's activation, so some Delta-V ends up being wasted. Is this avoidable in some way?

Secondly, on cooling down the engine after shut-down, the radiators do successfully whick away some of the heat, but there's still some heat left over that manages to wear away at the reactor core. I am currently using 12 XR-500 radiators (Total heat rejection of about 6000 kW when reactor is in use.) Do I just need more radiators, or should it perhaps be best to slowly throttle down the engine to give the radiators more leeway to get rid of the heat?

Great, glad I could help 

On the topic of reactor shutdown,  I have not been using KA engines recently and noted their behavior, so I would have to do some testing just like you, and see what occurs. On the previous page you can see some other users discussing the matter; in a nut shell - real-world NTRs would also need a spool-down cooling cycle. So it could honestly be a feature of these KA engines that you should leave your engine running, throttle the reactor back down, and let the cryo propellant do most of the reactor cooling, before finally cutting both the reactor and engine throttle to 0...

Though it could also be that the engines are not functioning as desired. I can not speak for Nertea and his current design goals regarding KA and System Heat - I know all of his mods want to strike a good balance of realism and accessibility. Best you can do is  follow through with some more testing and post the results here so he can revisit and provide more clarification, if needed.

[KSPrynk]

4 hours ago, lemon cup said:

On the topic of reactor shutdown,  I have not been using KA engines recently and noted their behavior, so I would have to do some testing just like you, and see what occurs. On the previous page you can see some other users discussing the matter; in a nut shell - real-world NTRs would also need a spool-down cooling cycle. So it could honestly be a feature of these KA engines that you should leave your engine running, throttle the reactor back down, and let the cryo propellant do most of the reactor cooling, before finally cutting both the reactor and engine throttle to 0...

I think you're spot on; it's probably intentional, to be realistic.  In theory, true bi-modal NTRs should have enough radiator capacity to handle a reactor in steady-state electricity generation power levels, and minimize (or perhaps eliminate) the need for propellant quenching.  But I've read docs suggesting bi-modals make some engineering compromises for power generation that can limit max isp.  Plus they're more complex, hence many NASA Mars mission designs stick with plain NTRs for thrust and solar panels for power.

@intelliCom, the trick with radiators is to find the balance between cooling and wasting propellant for quench cooling.  You don't want to go too crazy on radiators, because that then becomes more mass eating into your total dv budget.

To minimize radiator needs, it helps to minimize the number of NTRs to be cooled.  Real LH2 NTRs have relatively low thrust - not nearly as low as real ion engines - so if you have burn durations of a few minutes; a few seconds at mediocre isp shouldn't be a big deal.  I think some NTR mission profiles have had split-burn orbital pumping, which can be plotted with Maneuver Node Splitter.

Landing and taking off on a high-g planet may be problematic, but why are you spraying radioactive fuel rod spalling and neutrons all over my nice clean planet, while flying over my base?  I haven't tried out any of the LOx augmented NTRs, to see what impact Oxidizer has on the cooling profiles.

FYI, I also still haven't tried to see if there's any MJ-compatible automatic power control for use in pre-plotted manuever nodes....

[Spaceman.Spiff]

Perhaps as a reference for a later engine expansion/revamp:

Spoiler

http://www.astronautix.com/r/rd-0410.html

 

 

Edited June 3, 2021 by Spaceman.Spiff

[Starhelperdude]

2 minutes ago, Spaceman.Spiff said:

Perhaps as a reference for a later engine expansion/revamp:

  Hide contents

http://www.astronautix.com/r/rd-0410.html

 

 

isn't the restock+ cherenkov derived from it?

[Nertea]

Yes indeed it is. 

[konsti156]

something isn't right I think. When I use a nuclear engine like the "NV-100 Neptune" i got more thrust and ISP with LOx injection.

For example:

With LOx: 1,15 TWR   3157 m/s dV

Without:  0,77 TWR    1981 m/s dV

Should I not get more dV and less thrust without LOx injection?

[Doggydog]

2 hours ago, konsti156 said:

something isn't right I think. When I use a nuclear engine like the "NV-100 Neptune" i got more thrust and ISP with LOx injection.

For example:

With LOx: 1,15 TWR   3157 m/s dV

Without:  0,77 TWR    1981 m/s dV

Should I not get more dV and less thrust without LOx injection?

lox should give more TWR, as its both adding more mass to the exhaust, and reacting with the LH2 to produce more energy. The higher delta V is because in augmented mode you are using the whole tank as fuel, where as in pure nuclear mode you are only using the LH2. When you do switch the tanks to pure LH2, the mass is still lower than the Hydrolox tank, so you need to add more tanks to make up for it.

Edited June 23, 2021 by Doggydog

[jimmymcgoochie]

It depends on your fuel tank setup- using a tank of hydrogen and oxidiser will tend to favour the LOx-augmented mode because oxidiser is heavy but hydrogen is not; when burning the oxidiser it’s part of the fuel mass, so counts towards delta-V, but in hydrogen-only mode the oxidiser is part of the dry mass, so reduces delta-V because it’ll still be there once the hydrogen is used up.

The best tank setup for these engines is to use main tanks of just hydrogen, with a few small tanks of just oxidiser as needed and rigged to be dropped as soon as they’re empty to avoid dragging their empty weight around; baguette tanks on decouplers is a good option.

[konsti156]

14 hours ago, Doggydog said:

lox should give more TWR, as its both adding more mass to the exhaust, and reacting with the LH2 to produce more energy. The higher delta V is because in augmented mode you are using the whole tank as fuel, where as in pure nuclear mode you are only using the LH2. When you do switch the tanks to pure LH2, the mass is still lower than the Hydrolox tank, so you need to add more tanks to make up for it.

 

2 hours ago, jimmymcgoochie said:

It depends on your fuel tank setup- using a tank of hydrogen and oxidiser will tend to favour the LOx-augmented mode because oxidiser is heavy but hydrogen is not; when burning the oxidiser it’s part of the fuel mass, so counts towards delta-V, but in hydrogen-only mode the oxidiser is part of the dry mass, so reduces delta-V because it’ll still be there once the hydrogen is used up.

The best tank setup for these engines is to use main tanks of just hydrogen, with a few small tanks of just oxidiser as needed and rigged to be dropped as soon as they’re empty to avoid dragging their empty weight around; baguette tanks on decouplers is a good option.

Thank you guys. Now I get it.

The LH2 tank was much lighter with less fuel. Now it makes sense.

 

[Rakete]

Just a silly question: Is there some kind of wiki for this and the other NF-Mods, that describes how the newly invented mechanisms work and give a little starting help in How-to-do ?

[Rakete]

On 3/9/2021 at 9:19 PM, Nertea said:

Just a note - this mod needs an update to work with Waterfall 0.6.0. Will be coming in the next few days. 

Is that waterfall-compatibility upgraded version already available?

Bug Report (major):

Plumes of Oxidizer-boosted nuclear engines do not show up (only the inside of the nozzle turns purple).

Edited June 30, 2021 by Rakete

[Rakete]

Bug Report (minor):

Plume of emancipator at zero throttle still shows litte flickering in the middle of the nozzle.

Edited June 30, 2021 by Rakete

[Tomáš Brada]

On 6/29/2021 at 12:54 AM, Rakete said:

Is that waterfall-compatibility upgraded version already available?

Bug Report (major):

Plumes of Oxidizer-boosted nuclear engines do not show up (only the inside of the nozzle turns purple).

Can confirm. The effect controller "throttle" is incorrectly bound to the LH2 engine module on both effects, thus both (LH2 & LH2Ox) effects show up in LH2 mode and none show up in augmented mode.

[Nertea]

I'm sure it'll be fixed sometime

[theJesuit]

@Nertea,

Following my post in the CyroEngines thread, was there a particular formula that was applied to the optional LF patch for the atmospheric curves in Kerbal Atomics?  Or are they all individually balanced?

Peace.

 

[Nertea]

No, barely thought about it. It's mostly to stop the complaining .

[Rakete]

On 6/30/2021 at 10:23 PM, Tomáš Brada said:

Can confirm. The effect controller "throttle" is incorrectly bound to the LH2 engine module on both effects, thus both (LH2 & LH2Ox) effects show up in LH2 mode and none show up in augmented mode.

You seem to know how to correct it in the configs? Which files have to be changed in what way? 

 

Second question: some engines are described as trimodal. But i only found a switch to toggle LH2 and LH2/O-Mode. Tri-modal implies a third mode... What did I overlook?

Edited July 2, 2021 by Rakete

[Spaceman.Spiff]

27 minutes ago, Rakete said:

third mode

power generation using the nuclear reactor. 

Edited July 2, 2021 by Spaceman.Spiff

[Rakete]

9 hours ago, Spaceman.Spiff said:

power generation using the nuclear reactor. 

Wasn't there. Maybe I had to install an extra patch... but as far as kerbal atomics go: I discarded it for now and wait with the re-install until the plumes are fixed or there is a descrption how to fix the configs.

Edited July 3, 2021 by Rakete

[coyotesfrontier]

I feel that the current exhaust cooling system is way too punishing, as setting the throttle to 0, turning off the reactor, and turning off the engine all result in a very quick meltdown unless you do it very carefully. While a system like this would fit in something like Kerbalism or RO, I feel like it's way too difficult compared to the balance of the rest of everything in stock and the PKMC suite.

I propose reducing the engine heat production to it's original values, and reducing the exhaust cooling percentage to half its current value. (for example, the LV-N's heat production would become 200kw from 2,000kw, and the exhaust cooling percentage would be reduced to 50%) This allows players to take 2 possible routes in building a ship: Either put enough radiators for the heat to be stable even when the engine isn't firing (for example, putting 200kw of radiators for a single LV-N), which is safer but less efficient, or put only enough radiators for the engine while it's firing (for example, putting 100kw of radiators for a single LV-N), which is difficult but more efficient.

[Nertea]

Your concerns have been noted. 

[Rakete]

6 hours ago, coyotesfrontier said:

I feel that the current exhaust cooling system is way too punishing, as setting the throttle to 0, turning off the reactor, and turning off the engine all result in a very quick meltdown unless you do it very carefully. While a system like this would fit in something like Kerbalism or RO, I feel like it's way too difficult compared to the balance of the rest of everything in stock and the PKMC suite.

I propose reducing the engine heat production to it's original values, and reducing the exhaust cooling percentage to half its current value. (for example, the LV-N's heat production would become 200kw from 2,000kw, and the exhaust cooling percentage would be reduced to 50%) This allows players to take 2 possible routes in building a ship: Either put enough radiators for the heat to be stable even when the engine isn't firing (for example, putting 200kw of radiators for a single LV-N), which is safer but less efficient, or put only enough radiators for the engine while it's firing (for example, putting 100kw of radiators for a single LV-N), which is difficult but more efficient.

Agreed. I support this opinion, as far as I tested out Kerbal atomics few days ago. In reality you would have a computer to controll precise burn durations in combination with a coordinated reactor shutdown at the end of the burn. But in KSP you can hardly reach both goals at once, if you don't do a overkill of cooling panels to keep the reactor in a not cooled by firing engine state cool. And if you have more than one nuclear engine you will either mess up the burn or mess up some of the reactors... (or have a ludacris amount of panels with you) :-) 

To my mind, a more player friendly rebalance would be a good idea. Playerfriendly is always a good choice.

(looking forward to come back to kerbal atomics when the plumes work again correctly.  no hurry, take your time  - thumps up for nertea's efforts. Greatest Modmaker for KSP ever.)

Edited July 3, 2021 by Rakete

[Nertea]

This is not the right thread to discuss System Heat. 

Let's just understand I am aware of the whole garbage nature of the system now and 'll figure it out eventually. 

[Rakete]

System Heat? It was about ideas to optimize the heat of Kerbal Atomics Parts and their mechanics. Just relax :-) Since your Mods act together in a wonderful way, there are topics on them, which lie exactly on the border of two mod threads. Sooo just relax :-) I really appriciate your work, which you put into these mods.