Discussion of metallic hydrogen propulsion split from another thread.

[Guest]

11 hours ago, kerbiloid said:

It does. Just remove the tank internal pressure and get propelled in the opposite direction.

Wrong. It doesn't propel you in the "opposite direction". It propels you in all directions at once. This isn't a propellant, it's a bomb. At most, you can try using it as a really crappy Orion. 

15 hours ago, wumpus said:

How do you prove that?  Was there just one (or a limited subsection) of possible states of metalic hydrogen that were potentially metastable and were recently shown to be not metastable?  Obviously the onus was to prove the feasibility of metalic hydrogen and that required assumptions that have been presumably been proven not true.

- I have a lousy background in chemistry
- I have been pushing our "science fiction" forum member to use this, with warnings that it would date any work and was likely to be seen as "no longer viable" at a moment's notice.  Presumably now is too late...

This and other posts by this guy, there's no need to duplicate what he did. All current evidence points to metallic hydrogen not being metastable. This is far beyond chemistry and into materials physics. I really don't think there's any chance of it turning out to be an useful material at this point.

[G'th]

12 minutes ago, Dragon01 said:

Wrong. It doesn't propel you in the "opposite direction". It propels you in all directions at once. This isn't a propellant, it's a bomb. At most, you can try using it as a really crappy Orion. 

Just spit-balling but without a nozzle a normal rocket is just a giant bomb as well. 

[Guest]

7 minutes ago, G'th said:

Just spit-balling but without a nozzle a normal rocket is just a giant bomb as well. 

No, it isn't. This is a common misconception, actually. Rockets do not ride a "barely contained explosion". An "explosion", of any kind, in this case, a detonation, would blow the engine apart, no matter what. In rocketry, this is called a hard start. During normal operation, a what happens in a rocket engine is called deflagration. The difference is, the combustion is supersonic in the former case, and subsonic in the latter. There's no shockwave in the latter case, which has important implications for structural integrity of the engine. The gas flow doesn't become supersonic until after it goes through the nozzle. A rocket engine without a nozzle is blowtorch, not a bomb.

What would a metallic hydrogen tank do? Neither. In metallic hydrogen's case, all energy would be spontaneously released the moment the pressure subsides below the point needed to keep it metallic. This is similar to a BLEVE, or a "boiling liquid expanding vapor explosion", which also doesn't typically involve combustion, just a hole punctured in a high-pressure tank where the liquid is kept in its state by pressure, not temperature. When this pressure is released, all of the tank's contents instantly turn into vapor, launching pressure through the roof and resulting in a very supersonic shockwave, which gives the acronym an alternate explanation of "blast leveling everything very efficiently". Lowering pressure on a bunch of metallic hydrogen is that, but several orders of magnitude worse.

[G'th]

13 minutes ago, Dragon01 said:

No, it isn't. This is a common misconception, actually. Rockets do not ride a "barely contained explosion". An "explosion", of any kind, in this case, a detonation, would blow the engine apart, no matter what. In rocketry, this is called a hard start. During normal operation, a what happens in a rocket engine is called deflagration. The difference is, the combustion is supersonic in the former case, and subsonic in the latter. There's no shockwave in the latter case, which has important implications for structural integrity of the engine. The gas flow doesn't become supersonic until after it goes through the nozzle. A rocket engine without a nozzle is blowtorch, not a bomb.

What would a metallic hydrogen tank do? Neither. In metallic hydrogen's case, all energy would be spontaneously released the moment the pressure subsides below the point needed to keep it metallic. This is similar to a BLEVE, or a "boiling liquid expanding vapor explosion", which also doesn't typically involve combustion, just a hole punctured in a high-pressure tank where the liquid is kept in its state by pressure, not temperature. When this pressure is released, all of the tank's contents instantly turn into vapor, launching pressure through the roof and resulting in a very supersonic shockwave, which gives the acronym an alternate explanation of "blast leveling everything very efficiently". Lowering pressure on a bunch of metallic hydrogen is that, but several orders of magnitude worse.

The point being that uncontrolled a rocket is not effectively different from a bomb. If you ignited all the fuel at once it will explode. 

Assuming that we won't figure a way to control the reaction in a way conductive to propulsion is just pessimistic non-science when we haven't even gotten to a point where we can make the stuff. Until actually proven otherwise there is zero reason outside of pessimism to write off MH as a fuel. 

 

[Guest]

26 minutes ago, G'th said:

The point being that uncontrolled a rocket is not effectively different from a bomb. If you ignited all the fuel at once it will explode. 

Assuming that we won't figure a way to control the reaction in a way conductive to propulsion is just pessimistic non-science when we haven't even gotten to a point where we can make the stuff. Until actually proven otherwise there is zero reason outside of pessimism to write off MH as a fuel. 

No! You haven't gotten a single thing right here.

1. How would you ignite "all the fuel at once"? There is no such thing, except with monopropellants. In which case the propellant tank is a bomb, not the engine.
2. There's no such thing as an "uncontrolled rocket engine". The closest thing to it is properly called "an open fire". A turbopump might fail due to mechanical stress if it overspeeds, but that's it. An uncontrolled rocket is dangerous, because it's a giant, tumbling mass of highly flammable/oxidizing propellants and metal. Yes, it will explode if it hits the ground, but it will not ignite all at once. The propellants will get atomized, partially mixed, ignited by an external source and for most part, blown apart without igniting. After the N1 was done exploding, it was raining kerosene. Hypergolics are even better about it, they just start a fire (if that), albeit a really toxic fire. Most of the time, rockets explode because the RSO blows them up.
3. There is no "controlling" phase changes, except by the thing that causes them. Can you control how the ice will melt? Yes, you can control boiling and freezing of water, but water is weird like that. In most cases, once the conditions are right, the phase change happens. In particular, metallic hydrogen requires high pressure to exist, and once it is released, it stops being metallic. Simple as that. It's not a reaction. The very nature of this phenomenon is completely different from chemical reactions, fusion or fission.
4. We have gotten to the point we can make the stuff. It evaporated instantly once the pressure was released. It's not pessimism, it's science. It's you who are grasping at straws, attempting to see a "back door" into making a metallic hydrogen engine, when in fact there is none. It's been dubious from the start, and has now been disproven. 

Edited October 4, 2019 by Guest

[magnemoe]

41 minutes ago, Dragon01 said:

No, it isn't. This is a common misconception, actually. Rockets do not ride a "barely contained explosion". An "explosion", of any kind, in this case, a detonation, would blow the engine apart, no matter what. In rocketry, this is called a hard start. During normal operation, a what happens in a rocket engine is called deflagration. The difference is, the combustion is supersonic in the former case, and subsonic in the latter. There's no shockwave in the latter case, which has important implications for structural integrity of the engine. The gas flow doesn't become supersonic until after it goes through the nozzle. A rocket engine without a nozzle is blowtorch, not a bomb.

What would a metallic hydrogen tank do? Neither. In metallic hydrogen's case, all energy would be spontaneously released the moment the pressure subsides below the point needed to keep it metallic. This is similar to a BLEVE, or a "boiling liquid expanding vapor explosion", which also doesn't typically involve combustion, just a hole punctured in a high-pressure tank where the liquid is kept in its state by pressure, not temperature. When this pressure is released, all of the tank's contents instantly turn into vapor, launching pressure through the roof and resulting in a very supersonic shockwave, which gives the acronym an alternate explanation of "blast leveling everything very efficiently". Lowering pressure on a bunch of metallic hydrogen is that, but several orders of magnitude worse.

All modern explosives detonates. Its an few exceptions who uses slower explosions either to reduce shock and vibrations if you need to blast close to other stuff and legal issues like blasting kits using black powder who is  
Guns uses an explosion however. More so an pipe bomb and and solid fuel roket is only difference in its nozzle if lit by an burning fuse. 

As an teen we tried to make an pipe bomb. Knowing this was very dangerous we knew about an remote field with two holes made for some drainage project. Perfect for our purpose. Put the bomb in one hole and we hide in the other. 
Well the bomb became an rocket because an too large fuse hole and the explosive was not energetic enough its jumped out of its hole and down into our  buzzing around. 
 

[G'th]

3 minutes ago, Dragon01 said:

No! You haven't gotten a single thing right here.

1. How would you ignite "all the fuel at once"? There is no such thing, except with monopropellants. In which case the propellant tank is a bomb, not the engine.
2. There's no such thing as an "uncontrolled rocket engine". The closest thing to it is properly called "an open fire". A turbopump might fail due to mechanical stress if it overspeeds, but that's it. An uncontrolled rocket is dangerous, because it's a giant, tumbling mass of highly flammable/oxidizing propellants and metal. Yes, it will explode if it hits the ground, but it will not ignite all at once. The propellants will get atomized, partially mixed, ignited by an external source and for most part, blown apart without igniting. After the N1 was done exploding, it was raining kerosene. Hypergolics are even better about it, they just start a fire (if that), albeit a really toxic fire. Most of the time, rockets explode because the RSO blows them up.
3. There is no "controlling" phase changes, except by the thing that causes them. Can you control how the ice will melt? Yes, you can control boiling and freezing of water, but water is weird like that. In most cases, once the conditions are right, the phase change happens. In particular, metallic hydrogen requires high pressure to exist, and once it is released, it stops being metallic. Simple as that. It's not a reaction. The very nature of this phenomenon is completely different from chemical reactions, fusion or fission.
4. We have gotten to the point we can make the stuff. It evaporated instantly once the pressure was released. It's not pessimism, it's science. It's you who are grasping at straws, attempting to see a "back door" into making a metallic hydrogen engine, when in fact there is none. It's been dubious from the start, and has now been disproven. 

1. ?? Have you not seen what happens when literally any given rocket explodes? 

2. I never said there was such a thing. Please feel free to quote me. I said an uncontrolled -rocket-. 

3. Except you don't know that. It isn't definitive whether or not MH is meta-stable or not. And if has been proven, then I recommend you cite the source. And lets not get tied up in semantics. You know what I'm referring to when I said reaction.

4. Cite it, for one, and for two, the only source I found on the matter was inconclusive on whether it or not it actually evaporated; it wasn't witnessed. https://www.sciencealert.com/the-world-s-only-metallic-hydrogen-sample-has-disappeared 

So no, nothing has been disproved at all. 

[wumpus]

1 hour ago, Dragon01 said:

No, it isn't. This is a common misconception, actually. Rockets do not ride a "barely contained explosion". An "explosion", of any kind, in this case, a detonation, would blow the engine apart, no matter what. In rocketry, this is called a hard start.

Except that in rocketry pretty much every crazy idea is pitched and plenty of those have been tried.  Including pulsed detonation rockets.  The Air Force even powered a Rutan Long-EZ via pulsed detonation in 2008 (presumably way less thrust than a rocket would want, otherwise the airframe couldn't handle the acceleration or drag).  I think the idea for rockets was that you get more momentum through detonation (energy more or less has to be a wash), so you get better Isp.  Also they were typically trying to use air-breathers, so anything that gives you enough thrust without carrying oxidizer is a win.  So I'm pretty sure there was plenty of research on doing just this (mostly before 2008 from memory), and it really didn't go anywhere.

And no matter how they do it, any pulse detonation engine will have a noise issue that can't be silenced.  Probably worse than supersonic propellers, and really useful for uncrewed flight (assuming TWR>>1).

[Guest]

20 minutes ago, magnemoe said:

All modern explosives detonates. Its an few exceptions who uses slower explosions either to reduce shock and vibrations if you need to blast close to other stuff and legal issues like blasting kits using black powder who is  
Guns uses an explosion however. More so an pipe bomb and and solid fuel roket is only difference in its nozzle if lit by an burning fuse. 

As an teen we tried to make an pipe bomb. Knowing this was very dangerous we knew about an remote field with two holes made for some drainage project. Perfect for our purpose. Put the bomb in one hole and we hide in the other. 
Well the bomb became an rocket because an too large fuse hole and the explosive was not energetic enough its jumped out of its hole and down into our  buzzing around. 
 

Low explosives deflagrate. High explosives detonate. Both have uses. Guns, in particular, use low explosives. A detonation inside the barrel is lethal. Modern gun propellants are carefully formulated to have the desired burn rate. They burn, quickly, but not at a supersonic speed. The bullet may exit at a supersonic speed, but this is with relation to air, not to the propelling gas, in which the speed of sound is different. 

If your "explosive" burned, then you either had a bad explosive, or didn't initiate it right. C4 can deflagrate, a fact well known in the military, who use it as camp stove fuel. That something can detonate doesn't mean it will. 

13 minutes ago, G'th said:

3. Except you don't know that. It isn't definitive whether or not MH is meta-stable or not. And if has been proven, then I recommend you cite the source. And lets not get tied up in semantics. You know what I'm referring to when I said reaction.

4. Cite it, for one, and for two, the only source I found on the matter was inconclusive on whether it or not it actually evaporated; it wasn't witnessed. https://www.sciencealert.com/the-world-s-only-metallic-hydrogen-sample-has-disappeared 

Your source is a year old. Go and read the thread I linked to, it has sources aplenty, including more recent ones. I don't feel like finding the exact link now, but all you need to know is in there. 

13 minutes ago, G'th said:

1. ?? Have you not seen what happens when literally any given rocket explodes? 

Yes, the actual bomb attached to it blows, and then propellants mostly spray out as a mist, with some mixing and igniting, leading to a nice big fireball. High explosives don't usually produce much of a fireball, they're more of a flash and a puff of smoke (think WWII flak). It's deflagration that results in impressive balls of fire.

11 minutes ago, wumpus said:

Except that in rocketry pretty much every crazy idea is pitched and plenty of those have been tried.  Including pulsed detonation rockets.  The Air Force even powered a Rutan Long-EZ via pulsed detonation in 2008 (presumably way less thrust than a rocket would want, otherwise the airframe couldn't handle the acceleration or drag).  I think the idea for rockets was that you get more momentum through detonation (energy more or less has to be a wash), so you get better Isp.  Also they were typically trying to use air-breathers, so anything that gives you enough thrust without carrying oxidizer is a win.  So I'm pretty sure there was plenty of research on doing just this (mostly before 2008 from memory), and it really didn't go anywhere.

And no matter how they do it, any pulse detonation engine will have a noise issue that can't be silenced.  Probably worse than supersonic propellers, and really useful for uncrewed flight (assuming TWR>>1).

All PDEs I know of are airbreathers. This example is completely irrelevant, and isn't even rocketry. This is an odd evolution of the pulsejet which never seems to have gotten anywhere. The only way to use detonations in a rocket is a pusher plate. This was actually tested (as a precursor to Orion), but I don't think it's of much use.

Edited October 4, 2019 by Guest

[G'th]

You are not conductive to a good conversation guy. 

[Incarnation of Chaos]

On 10/3/2019 at 7:26 PM, wumpus said:

How do you prove that?  Was there just one (or a limited subsection) of possible states of metalic hydrogen that were potentially metastable and were recently shown to be not metastable?  Obviously the onus was to prove the feasibility of metalic hydrogen and that required assumptions that have been presumably been proven not true.

- I have a lousy background in chemistry
- I have been pushing our "science fiction" forum member to use this, with warnings that it would date any work and was likely to be seen as "no longer viable" at a moment's notice.  Presumably now is too late...

The study that found that metallic hydrogen could be metastable is from the 70s; well before current experiments. The experiments performed recently have had it dissipate whenever pressure is removed; this means that with our current knowledge that metallic hydrogen has not been proven to be metastable. This doesn't mean that it can't ever be metastable, but right now all evidence points to that being unlikely. Science deals with proof and evidence, so since it hasn't been shown to be metastable we cannot say that it is. This would also make any estimates of performance or projections of any traits highly dubious.

[kerbiloid]

Spoiler

If gawds wanted people to have the stable metallic hydrogen, why did they create other metals?

 

Edited October 6, 2019 by kerbiloid

[magnemoe]

On 10/4/2019 at 8:16 PM, Dragon01 said:

Low explosives deflagrate. High explosives detonate. Both have uses. Guns, in particular, use low explosives. A detonation inside the barrel is lethal. Modern gun propellants are carefully formulated to have the desired burn rate. They burn, quickly, but not at a supersonic speed. The bullet may exit at a supersonic speed, but this is with relation to air, not to the propelling gas, in which the speed of sound is different. 

If your "explosive" burned, then you either had a bad explosive, or didn't initiate it right. C4 can deflagrate, a fact well known in the military, who use it as camp stove fuel. That something can detonate doesn't mean it will. 

Your source is a year old. Go and read the thread I linked to, it has sources aplenty, including more recent ones. I don't feel like finding the exact link now, but all you need to know is in there. 

Yes, the actual bomb attached to it blows, and then propellants mostly spray out as a mist, with some mixing and igniting, leading to a nice big fireball. High explosives don't usually produce much of a fireball, they're more of a flash and a puff of smoke (think WWII flak). It's deflagration that results in impressive balls of fire.

All PDEs I know of are airbreathers. This example is completely irrelevant, and isn't even rocketry. This is an odd evolution of the pulsejet which never seems to have gotten anywhere. The only way to use detonations in a rocket is a pusher plate. This was actually tested (as a precursor to Orion), but I don't think it's of much use.

Yes was not clear enough that gunpowder deflagrate, not detonate. And yes its timed so an pistol has fast burning powder because the barrel is short. 
Cordite who is used in cannons burn mush slower than normal gunpowder as cannon barrels are long 

Pulse detonating jet engines is interesting because they offer better performance. Idea don't make so much sense for rockets however as their performance is already close to that is technically possible since you are mixing fuel and oxidizer much better an easier than in in an jet engine.  

[kerbiloid]

Why care about detonation-vs-deflagration when all you need is gas pressure.

https://www.dli.mn.gov/workers/boiler-engineer/poorly-built-air-tank-explodes

Happily, this wasn't metallic hydrogen.

[Guest]

Very disappointed by all the talk of metallic hydrogen. It doesn't work. It's done, busted, dead, nailed to the wall and buried six feet under. Please, just quietly ditch this and repurpose the assets, because that thing is an embarrassment. It's not "an unsolved engineering problem", it's bloody impossible. It's depressing to see them being so passionate about a debunked idea and so much science going into figuring out how something nonexistent would look. This will never be a thing in reality. Metallic hydrogen just isn't metastable.

Edited February 20, 2020 by Guest

[Dirkidirk]

6 minutes ago, Dragon01 said:

Very disappointed by all the talk of metallic hydrogen. It doesn't work. It's done, busted, dead, nailed to the wall and buried six feet under. Please, just quietly ditch this and repurpose the assets, because that thing is an embarrassment. It's not "an unsolved engineering problem", it's bloody impossible. It's depressing to see them being so passionate about a fairytale technology.

well there MiGhT bE sOmE wAy tO MAkE iT WoRK, posSiBly By kEEpINg tHe FuEl ComPreSSed dURINg FliGht.

Spoiler

I am also slightly disappointed

 

Edited February 20, 2020 by Dirkidirk

[XLjedi]

10 minutes ago, Dragon01 said:

Very disappointed by all the talk of metallic hydrogen. It doesn't work. It's done, busted, dead, nailed to the wall and buried six feet under. Please, just quietly ditch this and repurpose the assets, because that thing is an embarrassment. It's not "an unsolved engineering problem", it's bloody impossible. It's depressing to see them being so passionate about a fairytale technology.

Cheer up; that's just the slower Cat 3 engine!   LOL

I'll swing by in my Cat 4 powered white death engine star destroyer and give you a tow to the next star system with my tractor beams.

Edited February 20, 2020 by XLjedi

[MechBFP]

Just now, Dragon01 said:

Very disappointed by all the talk of metallic hydrogen. It doesn't work. It's done, busted, dead, nailed to the wall and buried six feet under. Please, just quietly ditch this and repurpose the assets, because that thing is an embarrassment. It's not "an unsolved engineering problem", it's bloody impossible. It's depressing to see them being so passionate about a fairytale technology.

It’s a game, not an engineering simulator built for Elon Musk. 

It might indeed look like an impossible engineering problem, and in fact very well might be truly impossible, but you are simply dismissing things that may happen in the future of science that we can’t even comprehend. 
Never say never. 

[Guest]

3 minutes ago, MechBFP said:

It might indeed look like an impossible engineering problem, and in fact very well might be truly impossible, but you are simply dismissing things that may happen in the future of science that we can’t even comprehend. 
Never say never. 

It's not an engineering problem. The whole idea of using MetH2 propellant hinges on a property that it has been proven not to have. It's not the future of science. It's a plain contradiction with science we have right now. I am dismissing things that have been disproven. So yeah, it's a pretty good idea to say "never" here. Just like we're not going to have ships moving through space using aether propellers.

As for all those "it's a game" arguments, the video itself is the best refutation. Just look at how seriously these guys are taking it. They intend to showcase near-future technologies, to promote science and educate people. That's also what I want from KSP2. If doing something like that, it's paramount that they have their facts straight.

Edited February 20, 2020 by Guest

[MechBFP]

2 minutes ago, Dragon01 said:

It's not an engineering problem. The whole idea of using MetH2 propellant hinges on a property that it has been proven not to have

Do you have a source for that?

 

[Guest]

1 minute ago, MechBFP said:

Do you have a source for that?

https://arxiv.org/ftp/arxiv/papers/1906/1906.05634.pdf

Quote

Upon pressure release, the metallic state transforms back to the C2/c-24 phase with almost no hysteresis, hence suggesting that the metallization proceeds through a structural transformation within the molecular solid, presumably to the Cmca-12 structure.

Emphasis mine. This doesn't mean it won't have any interesting properties, but the days of MetH2 as a miracle rocket fuel are over.

[XLjedi]

@Dragon01  Ah...  but you have neglected the application of Kilgore Equations!

This is all very well rooted in actual science (fiction)

Citation:  https://en.wikipedia.org/wiki/Torchship

Kilgore Kerman...  our new father of interstellar space travel!

Edited February 20, 2020 by XLjedi

[Guest]

Just now, XLjedi said:

@Dragon01  Ah...  but you have neglected the application of Kilgore Equations!

This is all very well rooted in actual science (fiction)

Citation:  https://en.wikipedia.org/wiki/Torchship

Want a torchship?
http://www.projectrho.com/public_html/rocket/enginelist3.php#fszpinch

Take a look at these stats, this thing is a real-life Epstein drive. It also doesn't rely on esoteric material properties, and in fact the principle had been tested in a lab. 

[Guest]

9 minutes ago, Dragon01 said:

Emphasis mine. This doesn't mean it won't have any interesting properties, but the days of MetH2 as a miracle rocket fuel are over.

I'm not convinced that there's no possibility of finding a dopant that stabilises it.

[XLjedi]

1 minute ago, Dragon01 said:

Want a torchship?
http://www.projectrho.com/public_html/rocket/enginelist3.php#fszpinch

Take a look at these stats, this thing is a real-life Epstein drive. It also doesn't rely on esoteric material properties, and in fact the principle had been tested in a lab. 

Argh... thems a lot of text and numbers; and we are but simple pirates.

So how fast does it go?