Discussion of metallic hydrogen propulsion split from another thread.

[Guest]

Metallic hydrogen again... this is how scientific misconceptions are born. No, it doesn't work as a propellant, we already know that. 

[Incarnation of Chaos]

4 hours ago, Dragon01 said:

Metallic hydrogen again... this is how scientific misconceptions are born. No, it doesn't work as a propellant, we already know that. 

Technically even if it isn't metastable it could be used as a propellent; it's just at that point the equipment to keep it under such monumental pressures and the materials to withstand the forces involved are well beyond our current technology and likely would be far heavier than whatever thrust the material would be producing.

[Guest]

Well, then it's just a particularly fancy cold gas thruster taken to the extreme. Also, seeing as releasing any hydrogen from containment would lower the pressure, resulting in rapid decomposition of the rest, the best you could do with such a setup is a BLEVE (only with a solid instead of liquid). The metastable hydrogen concept hinges on the fact that it wouldn't turn into gas spontaneously, but rather in a controlled fashion. Even if you could hold that kind of pressure, all you could make with it is a bomb, unless you also had a way to keep the tank constantly pressurized to the absurd pressure you need to maintain the hydrogen as a metal. In short, it doesn't work. Not now, not in the future, not ever. No amount of wishful thinking, or research funding for that matter, would change that, because we already know that it won't work.

[Incarnation of Chaos]

3 hours ago, Dragon01 said:

Well, then it's just a particularly fancy cold gas thruster taken to the extreme. Also, seeing as releasing any hydrogen from containment would lower the pressure, resulting in rapid decomposition of the rest, the best you could do with such a setup is a BLEVE (only with a solid instead of liquid). The metastable hydrogen concept hinges on the fact that it wouldn't turn into gas spontaneously, but rather in a controlled fashion. Even if you could hold that kind of pressure, all you could make with it is a bomb, unless you also had a way to keep the tank constantly pressurized to the absurd pressure you need to maintain the hydrogen as a metal. In short, it doesn't work. Not now, not in the future, not ever. No amount of wishful thinking, or research funding for that matter, would change that, because we already know that it won't work.

That's what i was envisioning tbh, perhaps having a system where you push chunks of the material out of a one-way valve to spontenously decompose so the tank never sees any meaningful changes in pressure.

But yeah metastable metallic Hydrogen is dead, and that means the entire idea of propelling a ship with it is dead with it. 

[GoldForest]

1 minute ago, Incarnation of Chaos said:

That's what i was envisioning tbh, perhaps having a system where you push chunks of the material out of a one-way valve to spontenously decompose so the tank never sees any meaningful changes in pressure.

But yeah metastable metallic Hydrogen is dead, and that means the entire idea of propelling a ship with it is dead with it. 

Or a multi-tank design. Possibly 3. One to hold the Metallic Hydrogen, one tank to drain the main tank and send it into a third tank, then the third tank sends the hydrogen directly into the combustion chamber, that way the main tank keeps its pressure. The second tank serves as a transfer node between first and third tank so the first one doesn't lose pressure. 

[Incarnation of Chaos]

2 minutes ago, GoldForest said:

Or a multi-tank design. Possibly 3. One to hold the Metallic Hydrogen, one tank to drain the main tank and send it into a third tank, then the third tank sends the hydrogen directly into the combustion chamber, that way the main tank keeps its pressure. The second tank serves as a transfer node between first and third tank so the first one doesn't lose pressure. 

Perhaps, all this adds weight though. And that's on top of our impossible pressurization system we're assuming we have and runs off of literal pixie dust because we're unable to currently approach these pressures except on microscopic interfaces between diamond anvil cells. 

Edited October 3, 2019 by Incarnation of Chaos

[GoldForest]

Just now, Incarnation of Chaos said:

Perhaps, all this adds weight though. And that's on top of our impossible pressurization system we're assuming we have and runs off of literal pixie dust because we're unable to currently approach these pressures except on microscopic interfaces in diamond anvil cells. 

Hmmmm, you're right. You would need a super dense gas to keep the pressure on the hydrogen, on top of a tank that can withstand such forces. A tank that strong would have to be probably at least 1 foot of titanium reinforced with steel braces probably. Titanium is light, but it adds up. 

Sulfur Hexafluoride and Perfluorobutane are pretty heavy gases, but Idk how they reacts to hydrogen. That's another concern, a gas that's dense enough to keep pressure on Hydrogen, but safe enough that it won't react with it. 

[Incarnation of Chaos]

Just now, GoldForest said:

Hmmmm, you're right. You would need a super dense gas to keep the pressure on the hydrogen, on top of a tank that can withstand such forces. A tank that strong would have to be probably at least 1 foot of titanium reinforced with steel braces probably. Titanium is light, but it adds up. 

Sulfur Hexafluoride and Perfluorobutane are pretty heavy gases, but Idk how they reacts to hydrogen. That's another concern, a gas that's dense enough to keep pressure on Hydrogen, but safe enough that it won't react with it. 

Ummmmmm

No

We're talking CNT's or GTFO at these types of pressures and temps; also you could just use a membrane to contain your gases you're using to pressurize the system.

[GoldForest]

7 minutes ago, Incarnation of Chaos said:

Ummmmmm

No

We're talking CNT's or GTFO at these types of pressures and temps; also you could just use a membrane to contain your gases you're using to pressurize the system.

Really? Titanium isn't strong enough? The strongest metal... dang, Metallic Hydrogen is really that dang complex?

CNT? Hmmm. Would simple carbon carbon do? We can't make CNT's in mass, but we can make carbon carbon, which is the strongest substance minus CNTs, and we can easily make it. 

Edited October 3, 2019 by GoldForest

[Incarnation of Chaos]

9 minutes ago, GoldForest said:

Really? Titanium isn't strong enough? The strongest metal... damn, Metallic Hydrogen is really that dang complex?

CBT? Hmmm. Would simple carbon carbon do? We can't make CBT's in mass, but we can make carbon carbon, which is the strongest substance minus CBTs, and we can easily make it. 

Have you actually looked at HOW we've attempted to produce vanishingly small quanitites of metallic hydrogen on earth?

This isn't the best source but gives you an idea what we're looking at- https://physicsworld.com/a/the-quest-to-create-metallic-hydrogen/

"At low temperatures, enormous pressures – until recently, around 350 GPa – have been achieved in diamond anvil cells (DACs). In DACs, the hydrogen is in a hole or cavity in a metallic gasket that is pressed between two diamond anvils. We developed techniques to achieve even higher pressures – touching 500 GPa"

GPa=Gigapascals, um=Micrometers, DAC=Diamond Anvil Cell

"The main challenge is creating the enormous pressures that are required. In DACs, the highest pressures are achieved with a small culet. The culet is the flat-polished part on the tip of a brilliant-cut diamond. At the highest pressures, we use culet flats around 20–30 µm in diameter with a hydrogen sample size of about 10 µm in diameter and 1 µm thick. While the sample is in a cryostat, this requires careful study using microscopes that creates certain optical challenges. Furthermore, the hydrogen sample is between two diamond anvils, and to study the sample, radiation must pass through those diamonds. The diamonds have a region in the visible and infrared where they are transparent, but block out light in the ultra violet, which limits studying them in this region of the spectrum."

Edited October 3, 2019 by Incarnation of Chaos
Further clarifying terms

[GoldForest]

5 minutes ago, Incarnation of Chaos said:

Have you actually looked at HOW we've attempted to produce vanishingly small quanitites of metallic hydrogen on earth?

This isn't the best source but gives you an idea what we're looking at- https://physicsworld.com/a/the-quest-to-create-metallic-hydrogen/

"At low temperatures, enormous pressures – until recently, around 350 GPa – have been achieved in diamond anvil cells (DACs). In DACs, the hydrogen is in a hole or cavity in a metallic gasket that is pressed between two diamond anvils. We developed techniques to achieve even higher pressures – touching 500 GPa"

GPa=Gigapascals

"The main challenge is creating the enormous pressures that are required. In DACs, the highest pressures are achieved with a small culet. The culet is the flat-polished part on the tip of a brilliant-cut diamond. At the highest pressures, we use culet flats around 20–30 µm in diameter with a hydrogen sample size of about 10 µm in diameter and 1 µm thick. While the sample is in a cryostat, this requires careful study using microscopes that creates certain optical challenges. Furthermore, the hydrogen sample is between two diamond anvils, and to study the sample, radiation must pass through those diamonds. The diamonds have a region in the visible and infrared where they are transparent, but block out light in the ultra violet, which limits studying them in this region of the spectrum."

So we need super low temperatures and very high pressure? Well, the two conditions are almost impossible together since pressure creates heat. 

[Incarnation of Chaos]

Just now, GoldForest said:

So we need super low temperatures and very high pressure? Well, the two conditions are almost impossible together since pressure creates heat. 

Passively you would be correct, however with active heat transport it is very possible. You would need some form of refrigration at the bare minimum.

[GoldForest]

4 minutes ago, Incarnation of Chaos said:

Passively you would be correct, however with active heat transport it is very possible. You would need some form of refrigration at the bare minimum.

A super cold place with high pressure... hmmm, wonder if the ocean could help with that. A certain place that has been visited by only 3 men. 

[Incarnation of Chaos]

Just now, GoldForest said:

A super cold place with high pressure... hmmm, wonder if the ocean could help with that. A certain place that has been visited by only 3 men. 

At the deepest portions of the marianus trench it approaches 1,086 bars; this is around 0.1086 gigapascals. 

Water is good for heat transfer though, so if you're already fine dealing with insane pressures then go for it.

[Guest]

Is every thread going to turn into whining about metallic hydrogen? It's in, deal with it.

[GoldForest]

5 minutes ago, Brikoleur said:

Is every thread going to turn into whining about metallic hydrogen? It's in, deal with it.

I honestly don't care that it's in. More diverse engines is what I want and that's what they're giving. 

[Incarnation of Chaos]

7 minutes ago, Brikoleur said:

Is every thread going to turn into whining about metallic hydrogen? It's in, deal with it.

I mean we were having a fairly decent discussion about the practical application of a system using it; not sure how that's considered "Whining". 

[Guest]

3 hours ago, Incarnation of Chaos said:

I mean we were having a fairly decent discussion about the practical application of a system using it; not sure how that's considered "Whining". 

Ok, then make a "all the Metallic Hydrogen discussion here" thread and discuss the problem there, I opened this topic expecting a page of discussion about the details unveiled by the video and I found yet another discussion about metallic hydrogen, like in every other post in the whole KSP2 section. 

Edited October 3, 2019 by Guest

[GoldForest]

3 minutes ago, Master39 said:

GOLDFOREST opened this topic expecting a page of discussion about the details unveiled by the video

Fixed.

And technically we ARE talking about what's in the video. 

[Guest]

35 minutes ago, GoldForest said:

Fixed.

Lol, sorry I meant "clicked on this topic" not "opened it".

35 minutes ago, GoldForest said:

And technically we ARE talking about what's in the video.

Yes, but it's not the first time a topic turns into a metallic hydrogen discussion and in this instance above there's nothing new in the arguments.

Edited October 3, 2019 by Guest

[Vanamonde]

This extensive discussion of the feasibility of a propulsion method has been split off from a thread about KSP preview material. 

[DStaal]

If we're thinking about tankage, one thought would be to have basically a fractal series of tanks - Empty the small ones first, then flow from big to small as you empty enough that you can transfer the fuel to another set of fully-pressurized tanks.  Done right you should be able to minimize the amount of pressurization filler you need.  (And you may be able to recycle it as well.)

Also note in the 'it takes super high pressures to create and store' - what makes metallic hydrogen interesting is that it should theoretically be meta-stable, so you need super high pressures to *create* it, but maybe just reasonable pressures to *store* it.  (From what I understand, this is unsupported theory at this point - *if* the theory turns out true, then metallic hydrogen is useful as a rocket fuel.  If it isn't, then it's just not going to be worth the bother.)

[Guest]

1 hour ago, DStaal said:

Also note in the 'it takes super high pressures to create and store' - what makes metallic hydrogen interesting is that it should theoretically be meta-stable, so you need super high pressures to *create* it, but maybe just reasonable pressures to *store* it.  (From what I understand, this is unsupported theory at this point - *if* the theory turns out true, then metallic hydrogen is useful as a rocket fuel.  If it isn't, then it's just not going to be worth the bother.)

That theory was proven false. So yeah, not worth the bother. Also, "fractal tanks" don't work. You may use a piston to keep the pressure constant, though. Not that there's any point in this. Metallic hydrogen is not a viable propellant, and we've known this for a while now. 

BTW, Science subforum is a bad place for this. As noted above, metastable metallic hydrogen isn't science, it's pure fantasy. Any attempt to make non-metastable metallic hydrogen a propellant is grasping at straws. It doesn't work, period. 

Edited October 3, 2019 by Guest

[wumpus]

4 hours ago, Dragon01 said:

That theory was proven false. So yeah, not worth the bother. Also, "fractal tanks" don't work. You may use a piston to keep the pressure constant, though. Not that there's any point in this. Metallic hydrogen is not a viable propellant, and we've known this for a while now. 

BTW, Science subforum is a bad place for this. As noted above, metastable metallic hydrogen isn't science, it's pure fantasy. Any attempt to make non-metastable metallic hydrogen a propellant is grasping at straws. It doesn't work, period. 

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...

[kerbiloid]

On 10/2/2019 at 11:41 PM, Dragon01 said:

it doesn't work as a propellant, we already know that. 

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