Art style: Please avoid neon lights. Please improve metallic hydrogen engine star-like exhaust.

[GoldForest]

7 minutes ago, regex said:

<sigh>

I have a real fear they're probably going to use isp values way beyond what is projected, and that cesium doping thing is basically only them talking about it. At least, I can't find anything other than the KSP devs referencing it. And that engine art is kind of a nightmare. Welp.

Well, this is just last known information. They could have changed it entirely. We'll just have to wait and see.

[Xelo]

7 hours ago, regex said:

<sigh>

I have a real fear they're probably going to use isp values way beyond what is projected, and that cesium doping thing is basically only them talking about it. At least, I can't find anything other than the KSP devs referencing it. And that engine art is kind of a nightmare. Welp.

https://patents.google.com/patent/WO2013070292A2/en
This patent mentions a nuclear rocket engine with hydrogen fuel 'seeded' with cesium (or some other alkali) to make 'the (hydrogen) gas electrically conductive as it flows though an MHD generator-accelerator'
So its possible this was the basis of that engine.

 

Quote

"A third advantage is to utilize the gas-cooled nuclear reactor to heat to 3000°K either hydrogen only, or to heat liquid oxygen and hydrogen followed by reaction of the oxygen with beryllium to heat the hydrogen to 6000°K, or much preferably to use water with non-equilibrium dissociation by LeChatelier's principle to yield oxygen for metal combustion while the hydrogen is heated to high temperature to be followed by seeding the ¾ with cesium and expanding the gas through a subsonic MHD generator that drives a co-axial supersonic MHD accelerator in an interplanetary rocket."

Edited October 28, 2022 by Xelo

[Bej Kerman]

6 hours ago, regex said:

<sigh>

I have a real fear they're probably going to use isp values way beyond what is projected, and that cesium doping thing is basically only them talking about it. At least, I can't find anything other than the KSP devs referencing it. And that engine art is kind of a nightmare. Welp.

I'd say an actual professional in the field is more trustworthy than a website developed by someone who admits it's just something they do in their freetime that may contain mistakes. There's nothing to worry about.

[Guest]

28 minutes ago, Bej Kerman said:

I'd say an actual professional in the field is more trustworthy than a website developed by someone who admits it's just something they do in their freetime that may contain mistakes. There's nothing to worry about.

That website has a ton of interviews with actual professionals and physicists, and they link their sources which more often than not are actual scientific papers so I'm pretty happy trusting it.

If you're not, that's fine, but quite frankly at this point I have zero use for your opinion on the matter.

35 minutes ago, Xelo said:

https://patents.google.com/patent/WO2013070292A2/en

This is fantastic stuff, thanks for finding it! I have my doubts about whether that is using the cesium to help direct the hydrogen out the back end, seems more like a heavy element to increase thrust from a conventional nuclear rocket engine rather than a metallic hydrogen engine. Still, very cool.

[Strawberry]

The use of cesium would decrease thrust and isp (even if by a little bit as I doubt youll need to dope the fuel with much cesium to get it easy to move), as heavier propellant is way less good as a working fluid. If you look into metallic tripropellants, you'll see that while the metal oxygen reaction is far more energetic, without that lightweight hydrogen present to be a working fluid, the isp is far lower then a triprop setup. This would be a reverse situation to where you're adding propellant that serves as a worse working fluid, thus reducing isp (but again likely only by a little bit as you probably dont need to add much cesium)

[Guest]

7 minutes ago, Strawberry said:

The use of cesium would decrease thrust and isp (even if by a little bit as I doubt youll need to dope the fuel with much cesium to get it easy to move), as heavier propellant is way less good as a working fluid. If you look into metallic tripropellants, you'll see that while the metal oxygen reaction is far more energetic, without that lightweight hydrogen present to be a working fluid, the isp is far lower then a triprop setup. This would be a reverse situation to where you're adding propellant that serves as a worse working fluid, thus reducing isp (but again likely only by a little bit as you probably dont need to add much cesium)

The paper that Xelo links also seems to be in reference to magnetohydrodynamic power generation in a conventional nuclear rocket engine (like NERVA). The cesium appears to be intended for that purpose and the fact that it is blown out the back is simply a side effect.

But I also thought that heavier atoms will produce more thrust and less isp? That's one of the appeals of hydrogen, you can get it going out the back very fast compared to other fuels. If you muddy the hydrogen you lose isp but gain thrust, that would likely be why you'd combine metallic hydrogen with water in atmosphere, it helps you get off the ground.

Edited October 28, 2022 by regex

[Strawberry]

12 minutes ago, regex said:

The paper that Xelo links also seems to be in reference to magnetohydrodynamic power generation in a conventional nuclear rocket engine (like NERVA). The cesium appears to be intended for that purpose and the fact that it is blown out the back is simply a side effect.

But I also thought that heavier atoms will produce more thrust and less isp? That's one of the appeals of hydrogen, you can get it going out the back very fast compared to other fuels. If you muddy the hydrogen you lose isp but gain thrust, that would likely be why you'd combine metallic hydrogen with water in atmosphere, it helps you get off the ground.

It's definitely possible to just run that magnetohydrodynamic generator in reverse and instead use it to accelerate the propellant in specific ways, it's been a pretty well studied field for electric spacecraft propulsion. I think from an engineering perspective its a bit of newer ground, but honestly I dont mind that as it's pretty scientifically sound, personally Id like it if the parts in ksp2 just so happen to add something new to potential design, instead of solely using only what was directly thought for it as it just seems really cool and potentially really helpful.

Injecting more propellant will generally just lead to higher thrusts, as you have more working fluid to use, this is why turbine engines are so efficient, they can pull in huge amounts of working fluid from the air. The thing for rocket engines is you also now have to carry that working fluid, making that tradeoff generally less worth it as you will generally worsen your isp by doing so (notable exception is in the case of metal triprop engines as mentioned earlier). Heavier atoms are worse at this, but they will work for this, the main reason why you'd want to use heavier atoms is for chemical nuclear thermal hybrids, where you use oxygen as an afterburner for a hydrogen nuclear thermal rocket, as that chemical reaction produces additional thrust at the cost of isp. 

Edited October 28, 2022 by Strawberry

[LHACK4142]

I just saw this thread, and I could not agree more with the first statement. PLEASE none of the lamentably common, unoriginal, annoyingly crowd-pleasingly distracting bright colors and flashy animations that are everywhere!!

And I do think the metallic hydrogen star is kind of strange. Either of the explanations seems to have a contradiction; If it is scientifically accurate, why isn't it mentioned anywhere? And if it's not scientifically accurate, why didn't the scientist they were working with comment on it? I wouldn't worry about the general scientific accuracy of the game, though, given the map view we've seen in the most recent feature video.

[Xelo]

1 hour ago, regex said:

This is fantastic stuff, thanks for finding it! I have my doubts about whether that is using the cesium to help direct the hydrogen out the back end, seems more like a heavy element to increase thrust from a conventional nuclear rocket engine rather than a metallic hydrogen engine. Still, very cool.

:0! I thought it might be relevant, as I noticed the exhaust is hydrogen in the exact temperature (6000K) that Tom Vinita quotes in the Next gen tech video (plus the cesium doping). I think how the team develops these rockets is just by mashing various rocket ideas, and presenting them to an expert(s) to see if its at least viable / what could be changed. In the video Nate jokingly recalls an anecdote that he asked whether they just could simply just 'add moar radiators' to  make the engine not melt from its heat. They may have stumbled onto this exact paper and just replaced the bulky nuclear bit with metallic hydrogen fuel, and kept the part at the end that dopes cesium for the magnetically confined thruster, the expert may have noted such an engine design would cause a star shape at the base to appear (though maybe at not what size or brightness), perhaps due to some of the exhaust arcing back around with the field lines.... 
(I'm not an expert, this is just speculation, but the visuals shown do have particles going in reverse in a field-line kinda trajectory (circled in red))

Edited October 28, 2022 by Xelo

[Aliquido]

On 10/25/2022 at 8:51 AM, regex said:

I've been looking through Google for a good thirty minutes and I can't find any metallic hydrogen engine concept art where it's exhausting before the nozzle. In fact, most of the concept art looks more like the four surrounding engines. That central engine is something different IMO, but I can't really guess what. Maybe some sort of fusion engine?

Regardless, the exhaust near the base should be even more diffuse than that coming out the nozzle when thrusting in a vacuum, you'd be hard-pressed to get those tight streams (and if you're wasting power doing that why not direct it out the back where you can get more thrust?).

I found some concept art from nasa, here you go.

[Guest]

14 hours ago, Xelo said:

:0! I thought it might be relevant, as I noticed the exhaust is hydrogen in the exact temperature (6000K) that Tom Vinita quotes in the Next gen tech video (plus the cesium doping). I think how the team develops these rockets is just by mashing various rocket ideas, and presenting them to an expert(s) to see if its at least viable / what could be changed. In the video Nate jokingly recalls an anecdote that he asked whether they just could simply just 'add moar radiators' to  make the engine not melt from its heat. They may have stumbled onto this exact paper and just replaced the bulky nuclear bit with metallic hydrogen fuel, and kept the part at the end that dopes cesium for the magnetically confined thruster, the expert may have noted such an engine design would cause a star shape at the base to appear (though maybe at not what size or brightness), perhaps due to some of the exhaust arcing back around with the field lines.... 
(I'm not an expert, this is just speculation, but the visuals shown do have particles going in reverse in a field-line kinda trajectory (circled in red))

Also no expert but particles arcing back along very strong magnetic lines seems legit.

Looking at the engine without the SFX, it has a plate with vanes at the base to ... direct the exhaust plasma? There are large pipes behind that and then a few running up the sides. If fuel is injected in the sides instead of the rear of the nozzle that just seems like a complete waste. Not opposed to the design really, I guess, but those base streams will be far, far, far more diffuse than depicted unless you're using a magnetic field to direct it (and once again, at that point why aren't you spitting it out the back?)

Then there's this earlier image which seems to be a much more realistic option (less detailed though):

It's like the combustion products go directly into the magnetic nozzle and there's no "exhaust management system" at the back because why would you do that?

Seems like this engine was made to take advantage of "the rule of cool", which I gotta say, is failing pretty hard as shown at this time. It's making me scratch my head more than go "neat!"

28 minutes ago, Aliquido said:

I found some concept art from nasa, here you go.

One thing I immediately notice about this concept image is that all the exhaust products are going out the back of the engine.

[Xelo]

7 hours ago, regex said:

Looking at the engine without the SFX, it has a plate with vanes at the base to ... direct the exhaust plasma? There are large pipes behind that and then a few running up the sides. If fuel is injected in the sides instead of the rear of the nozzle that just seems like a complete waste. Not opposed to the design really, I guess, but those base streams will be far, far, far more diffuse than depicted unless you're using a magnetic field to direct it (and once again, at that point why aren't you spitting it out the back?)

Maybe the side pipes are for cooling the (superconducting?) magnet rings, I'd imagine itd still get pretty hot from the exhaust even its not touching it. :0 
I also see the rings having thinner pipes on them, which could be fed from the aforementioned side pipes.

Edited October 29, 2022 by Xelo

[Ember12]

18 hours ago, Xelo said:

Maybe the side pipes are for cooling the (superconducting?) magnet rings, I'd imagine itd still get pretty hot from the exhaust even its not touching it. :0 
I also see the rings having thinner pipes on them, which could be fed from the aforementioned side pipes.

That's possible, but I don't know where the heat would go, because I don't see any radiator fins or anything.  Maybe it would dump the heat into the fuel before it it lit (however it is lit), or maybe you need to attach your own radiators.

Edited October 29, 2022 by Ember12
Typo

[Wubslin]

Without even reading any comments in this thread, I think it's kind of dumb to be hating on the magnetic nozzle having crazy wicked plasma leaks. I don't know where I recently heard someone describe magnetic plasma confinement as "squeezing jello using rubber bands", but it's basically true whether the plasma is quasi-neutral or not.  Anywhere the confinement isn't perfectly even, some plasma's going to try and squeeze through the gaps. Even in inertial confinement fusion you get this problem. With pelletized ICF like the Daedalus drive (read: teeny tiny thermonuclear weapon secondaries) you get "Rayleigh Taylor instabilities" where your metal ablator gets turbulent and mixes into the fusion fuel. With electrostatic fusors, you'll bet the plasma in the center will capitalize on any minute change in voltage gradient to squirt out of the little cage. The same will apply for magnetic confinement just as it does for any other type. Dynamically confining plasma (or really any fluid) is inherently going to be a messy affair. Remember that it's Kerbals who are the ones engineering these drives. A little multi-thousand kelvin rocket exhaust shooting out the side of your nozzle never hurt anyone.

[Guest]

1 hour ago, Wubslin said:

Without even reading any comments in this thread, I think it's kind of dumb to be hating on the magnetic nozzle having crazy wicked plasma leaks.

I really have no problems with plasma leaks, what I have a problem with is just how coherent they are. If you can create coherent, defined streams out of your plasma leaks then you can spit those leaks out the back of the engine. If those exhaust leaks were diffuse I wouldn't be making a fuss.

[Wubslin]

2 hours ago, regex said:

I really have no problems with plasma leaks, what I have a problem with is just how coherent they are. If you can create coherent, defined streams out of your plasma leaks then you can spit those leaks out the back of the engine. If those exhaust leaks were diffuse I wouldn't be making a fuss.

That doesn't follow. "If you can lose millions of watts in coherent, defined plumes of water vapor out the top of your power plant's cooling towers then you can afford to be using that heat to turn more turbines!" Sounds to me like you're trying to pass off an artistic complaint as an engineering complaint. Since it's all fiction, the losses coming from that plasma will be as little or as much as you want it to. The devs are still going to punch in the same number for "WyvernEngine_isp_setequal" either way.  If you don't like how the exhaust looks, just say so. I've voiced as much on here about the bright green skybox nebula and no one's come calling the police on me for it. Personally, I like the look of the leaky exhaust. It yells "MAGNETS!" right into the player's face.

[Guest]

2 minutes ago, Wubslin said:

If you don't like how the exhaust looks, just say so.

I've been saying that the whole time, I don't like the way it looks. It's just that it doesn't look good to me because it doesn't make any sense scientifically (or at least, no one has shown me why it should make sense scientifically).

[Xelo]

10 hours ago, Ember12 said:

That's possible, but I don't know where the heat would go, because I don't see any radiator fins or anything.  Maybe it would dump the heat into the fuel before it it lit (however it is lit), or maybe you need to attach your own radiators.

Incredibly dumb idea but, considering that metallic hydrogen could potentially be super conductive, what if the fuel itself was used as the magnetic coils (and coolant) when it passes through the engine bell? 

[Vl3d]

8 hours ago, Wubslin said:

Personally, I like the look of the leaky exhaust. It yells "MAGNETS!" right into the player's face.

May I remind you it is touching other components? Besides the destructive heat problem, it reminds me of cheap flashy games which overuse sparkles and oversaturated neon colors. It doesn't look as good as everything else in the image.

 

[Bej Kerman]

2 minutes ago, Vl3d said:

Besides the destructive heat problem, it reminds me of cheap flashy games which overuse sparkles and oversaturated neon colors.

And? It's realistic, at least it will be if the devs have heat transfer detection implemented in those areas. Whether or not it's realistic is the department of those who have read stacks of books on similar topics to determine how such an engine would work I.E. those Intercept consulted while creating the engine.

[Wubslin]

1 hour ago, Vl3d said:

May I remind you it is touching other components? Besides the destructive heat problem, it reminds me of cheap flashy games which overuse sparkles and oversaturated neon colors. It doesn't look as good as everything else in the image.

 

May I remind you that this image also has five vacuum exhaust plumes, precisely zero of which are interacting with each other? They're all clipped into each other. Also, I guarantee that if you plow engine first through the atmosphere your rocket exhaust won't form a blunt stagnation layer where the upwards rushing air fights the downwards rushing exhaust. Do you think your radiators are going to suffer from reduced efficiency because of view factor obstruction if you start piling on more than two of them around your rocket? It's just a video game.

https://tvtropes.org/pmwiki/pmwiki.php/Main/MST3KMantra

 

[Guest]

1 hour ago, Wubslin said:

Do you think your radiators are going to suffer from reduced efficiency because of view factor obstruction if you start piling on more than two of them around your rocket?

I do hope that's the case, this is a video game about rocket science after all. It would also be neat of those dumb "plasma leaks" damaged the other engines.

[t_v]

Just now, regex said:

I do hope that's the case, this is a video game about rocket science after all. It would also be neat of those dumb "plasma leaks" damaged the other engines.

View factor obstruction would be really processing intensive to implement when every radiator needs to check the position of every other radiator to see what percentage of the radiation just goes to the other radiator, and although it would make sense after the first few times you notice your radiators aren't working, the hit to performance would be too much for it to be worth it.

[Wubslin]

1 minute ago, regex said:

I do hope that's the case, this is a video game about rocket science after all. It would also be neat of those dumb "plasma leaks" damaged the other engines.

Temper your expectations. The game isn't going to run a raytracing monte carlo simulation every time you place a radiator in the VAB. Engines are just gonna work, and 90% of the game will be patched conics.

[Guest]

6 minutes ago, Wubslin said:

pThe game isn't going to run a raytracing monte carlo simulation every time you place a radiator in the VAB.

The game also isn't going to model exhaust interactions between five engines, but the least it could do is have some visuals at the base of an engine that match what's coming out the back end.