Discussion of metallic hydrogen propulsion split from another thread.

[KerikBalm]

1 hour ago, Incarnation of Chaos said:

Unless it got blown off, think the cores remaining from hot jupiters or super-earths around red dwarfs that couldn't generate enough of a magnetic field to hang on to it during their flaring. 

Then such an environment would be very high radiation, and using Lantr, pebble bed ntr, nuclear lightbulbs, other closed  cycle fission drive would work at least as well.

Its just not needed, and the magnetic confinement vacuum drive is particularly egregious (just dilute with liquid h2, and have a high isp drive that works in an atmosphere too, but with less twr than the water diluted version)

[Incarnation of Chaos]

54 minutes ago, KerikBalm said:

Then such an environment would be very high radiation, and using Lantr, pebble bed ntr, nuclear lightbulbs, other closed  cycle fission drive would work at least as well.

Its just not needed, and the magnetic confinement vacuum drive is particularly egregious (just dilute with liquid h2, and have a high isp drive that works in an atmosphere too, but with less twr than the water diluted version)

Oh I'm not arguing that a fictional fuel is needed, just saying that a high-g vacuum environment isn't impossible. Heck; due to Kepler only being able to reliably detect transits that lie on our inclination and the lack of survey atmospheric tools (Or rather limited scope of the ones we have available) i'd say there's a lot more room to speculate about how common certain combinations of planetary environments are than metastable metallic hydrogen. We used to think earth-like planets (Mass wise, not anything else) in the habitable zones were extremely rare, and even with the limited dataset from Kepler we managed to completely overturn that within a few years.

Personally as i mentioned before; I'll be using either brute-force clustering or remote Orion to overcome these in any potential KSP2 play sessions i have instead of Metastable Metallic Hydrogen. It's about as real as infinite fuel, so I'll consider it a cheat for my own sake.

[SOXBLOX]

8 hours ago, KerikBalm said:

Dissappointing that you continue not to address the science behind mmH and admit that you made factually incorrect statements.

Wow. And nothing says he has to "admit" anything to us.

[snip]

Edited November 1, 2020 by Vanamonde

[OHara]

1 hour ago, Incarnation of Chaos said:

Personally as I mentioned before; I'll be using either brute-force clustering or remote Orion to overcome these in any potential KSP2 play sessions i have instead

That could be fun.
I avoid KSP1's reaction-control-wheels in favor of fins and reaction thrusters -- and I highly recommend trying that because  it is fun.
Clearly the unrealistic RCS wheels help a lot in making KSP1 accessible.  After a while I embraced their over-powered-ness and now use them in space.

The supposed metallic hydrogen, though, probably has much higher energy density than any other chemical fuel, so any substitute clusters of chemical engines might have unwieldy tanks to the point of being un-fun.  We'll have to see.

It seems clear that the design of KSP2 wants to fill a niche between existing chemical fuels and nuclear propulsion, and that the material filling that niche is metatastable enough to move around.   So we might say that, in the Kerbal universe, that idea about metallic hydrogen arranging into a very stable hexagonal lattice of filaments is actually true!  To be fair, this imagined Kerbal universe goes well beyond what the Brovman 1972 paper speculates, but somebody from Harvard Univ. speculated that far beyond the science, and now the speculation has a life of its own.

On 10/25/2020 at 6:58 PM, Chilkoot said:

here's a layman-level summary (YouTube)

The same YouTuber has a followup (Why Metallic Hydrogen is so important! [2020])  that goes into the speculative applications including rockets.
YouTube comments kindly pointed out the error in figuring delta-V.  Another YouTube comment pointed to a 2017 paper (link) that seems to take metastability seriously, so I read it.  That 2017 paper does the analogue of figuring how hot you can superheat water above boiling in a clean cup (which I did this morning with violent results when I put in the coffee). That paper is something of a time-capsule, using only results from before 1982, plus what seems to be an assumption that the metal has to first dissociate into single H atoms before forming H₂, and working out the pressure where bubbles of H₂ in the metal would expand.    Living in a universe where those assumptions are true sounds like fun --- lucky Kerbals.

[Vanamonde]

Some comments have been removed. Do not make the discussion personal, please. Talk about the subject rather than tell other people what you believe their motives are. 

[KerikBalm]

4 hours ago, SOXBLOX said:

nothing says he has to "admit" anything to us.

I never said he had to, I am just saying that I am dissapointed that he didn't. He is on the record saying that he is willing to have a conversation about mmH, and he has made objectively false statements about mmH.

For my part, I would be reassured if he just came out and admitted that he said something wrong, and that he's just keeping it in for gameplay.

By saying nothing about it, then there are only 2 options: 1) he didn't know it was false and thus was misinformed and thus hasn't done proper research, or 2) he makes false statements, knowing that they are false.

Both are not good.

1) can be remedied, but with no sign its remedied, makes me worry what other misconceptions have made their way into KSP2.

2) .... well, there is a word for a person that does this, and it starts with L... Not good either.

So really the best outcome as I can see it is for him to show a sign that he is now properly informed, not doing (2), and just focusing on gameplay

[SOXBLOX]

2 hours ago, KerikBalm said:

...then there are only 2 options...

Actually, there are four. Your two, plus 3) he doesn't care whether some guy on the internet thinks the "misconception" needs to be remedied, admitted, or otherwise acknowledged, or 4) he cares more about having a playable game than having a perfectly scientifically accurate game, and included this because it was fairly plausible. (There are probably even more we both missed.)

3 is perfectly acceptable and well within human rights.

4 is a good sign that the devs are concerned with balance and engaging gameplay. (And it certainly isn't an excuse to include things like reactionless drives or technobabble garbage.)

If you don't want mmH in your game, you can certainly just not use it. (Like how I played a career save sans reaction wheels.) Or, use it, but call it a liquid-core nuclear engine or whatever. You can do whatever you like; that's the point of the game.

[KerikBalm]

9 hours ago, SOXBLOX said:

Actually, there are four. Your two, 

No, one of those 2 options must be true.

Any third option is as relevant as saying option 3: I have cookies with dinner tonight.... Totally irrelevant, and one of the two options is still true.

He made a factually incorrect statement, it is objectively wrong, with no legitimate debate otherwise.

Either he knew it was wrong, or he didn't.

Its basic logic: either A or not A.

Until he gives a sign that he knows his statement is wrong, the most generous conclusion is that the lead creative director for KSP2 doesn't know even the basics of what he is talking about - but this can be fixed with study.

The other option (this is not an accusation, just a statement of fact) is that he intentionally makes false statements - which IMO, creates problems that cannot be remedied.

So after making such a blatantly false statement, then saying that he is willing to have a conversation about it... the only thing that could restore my confidence in him is if he actually engages on the subject in a meaningful way, and shows that he is actually doing the research before throwing tech into KSP2... because so far he has given no sign that he has for mmH

[mcwaffles2003]

3 hours ago, KerikBalm said:

No, one of those 2 options must be true.

Any third option is as relevant as saying option 3: I have cookies with dinner tonight.... Totally irrelevant, and one of the two options is still true.

He made a factually incorrect statement, it is objectively wrong, with no legitimate debate otherwise.

Either he knew it was wrong, or he didn't.

Its basic logic: either A or not A.

Until he gives a sign that he knows his statement is wrong, the most generous conclusion is that the lead creative director for KSP2 doesn't know even the basics of what he is talking about - but this can be fixed with study.

The other option (this is not an accusation, just a statement of fact) is that he intentionally makes false statements - which IMO, creates problems that cannot be remedied.

So after making such a blatantly false statement, then saying that he is willing to have a conversation about it... the only thing that could restore my confidence in him is if he actually engages on the subject in a meaningful way, and shows that he is actually doing the research before throwing tech into KSP2... because so far he has given no sign that he has for mmH

You do realize that this is their game to make, right?

As much as we can deliberate and work to convince one another among this forum and pretend that we represent the whole community for which this game is intended, it isn't our decision to make. We haven't programmed squat for KSP 2, if mmH bugs you this bad then code it out, but isn't it a bit much to aggressively demand answers from the games creators as if they owe you a response for putting in the work for making the game?

Personally, if some random person came up to me demanding answers like this for artistic design choices I made in something I created I wouldn't pay any mind to them and brush them off as an angry person whom I just wouldn't like to engage in conversation with... Because why would I converse with someone who introduced themselves in an aggravated manner?

[KerikBalm]

22 minutes ago, mcwaffles2003 said:

You do realize that this is their game to make, right?

Yup, that's why I said: "I would have preferred if he said "yea, it seems like it can't really work... but if it could, it would be perfect for our vision of the gameplay, so we put it in anyway"

But as it is, his statement was objectively false."

22 minutes ago, mcwaffles2003 said:

Personally, if some random person came up to me demanding answers like this for artistic design choices I made in something I created I wouldn't pay any mind to them and brush them off as an angry person whom I just wouldn't like to engage in conversation with... Because why would I converse with someone who introduced themselves in an aggravated manner?

#1) I haven't demanded anything.

#2) I'm not angry or aggravated, but disappointed.

#3) I'm not questioning his artistic design choice. I'm questioning his objectively false statements contradicting facts.

#4) He is on record saying that he is willing to have the conversation about the science behind it, yet he hasn't engaged in any conversation about it (at least not in any public forum). 

Making a factually incorrect statement is not an "artistic choice". The point of view that I've expressed is that it would be fine if he said it was included for gameplay purposes, but not scientifically accurate. I'm not fine with him publicly making factually incorrect statements, with ample time to issue a correction, and refusing to do so while pretending to be open to discussion.

 

[Snark]

Hi folks,

Let's take it down a notch, please.

We appreciate that people feel passionately about this game, and that's great.  We also appreciate that opinions differ.

However, tempers appear to be flaring to the point that civil discussion is suffering, so please try to rein it in.  Of course everyone's entitled to their opinions, and of course we all know this and nobody here would assert something so silly as to claim that their opinion is the only valid one, right?

For any topic (this, or others):

• Some people care passionately about <thing>
• Other people may diametrically disagree, and be pasionate about that.
• Still others-- I'd hazard a guess, the large majority-- think it's no big deal and have other priorities.

All three groups are perfectly legitimate and "correct", because they're simply stating what they like and consider to be important.  Let's please try to keep sight of that, and not let it build to acrimony, shall we?

So, to be clear:

• You're entitled to your opinion.  Nobody else is in any position to tell you that your opinion is wrong.
• Other people are entitled to theirs.  You're not in a position to tell anyone else that their their opinion is wrong.
• Nobody is obliged to care about anyone else's particular opinion.  The fact that you're passionate about your opinion doesn't make it outweigh others'.

So, when discussing opinions, let's please try to stick to the form "I like/dislike <thing> because <reasons>", or "My view is different from yours because <my priorities>", and not go down the path of "Your viewpoint is wrong and doesn't matter because mine is the only valid one."

Please remember that what really matters is that we're all friends here and that our discussions stay civil-- because that's the only way we can really have discussions, which after all is what the forum is made of.

Leaving the thread locked for a little while to allow tempers to cool off.  Thank you for your understanding.

[EDIT] Okay, opening the thread back up.  Please play nice, folks, okay?  Thanks.

[Guest]

On 11/2/2020 at 7:38 AM, Snark said:

[EDIT] Okay, opening the thread back up.  Please play nice, folks, okay?  Thanks.

I would love to know where the information for doubts of stability are if someone wants to link them to me

[Entropian]

Circles, circles...  https://www.nature.com/articles/s41586-019-1927-3
https://arxiv.org/abs/1709.05300

[OHara]

4 hours ago, The Doodling Astronaut said:

I would love to know where the information for doubts of stability are if someone wants to link them to me

The simplest/reason for doubt is to compare with real single-component explosives (link)   On that list you can find nitroglycerin which is famously hard to handle, and at 30× higher energy density, metallic hydrogen.  Stable explosives have some difficult change in atomic arrangement, between the stored-energy configuration, and the exploded configuration, so that there is a difficult re-arrangement serving a barrier to keep it from exploding right away.   Hydrogen is so simple that it is hard to imagine such a barrier that would make it difficult for atoms to pair up.

So you would think that metallic hydrogen is the least likely candidate for a stable explosive, because it seems so easy for it to form H₂ molecules.

Nevertheless, if you google metallic hydrogen you quickly find Harvard University publishing in 'Science' magazine:  "Moreover, other predictions suggest solid metallic hydrogen (SMH) is metastable at room temperature when the pressure is released (Brovman, 1972). The combination of these expected properties makes SMH important for solving energy problems and can potentially revolutionize rocketry as a powerful propellant (Silvera, 'Conceptual launch vehicles...')."   One has to read carefully to notice the unjustified slide from "predictions suggest X" to "these expected properties " including X.

The "other predictions" is only one theoretical paper by Brovman and colleagues form 1972 that proposes a very strange structure for the metal, and describes it as metastable.  It is not clear to me what they mean by metastable.  The paper by Graham Ackland, that @Entropianlinked, suggests Brovman meant it would stay metal for some amount of time, and then Ackland computes the lifetime of the metal after releasing pressure to be <1 ps.  All theory, and no hint of what I would consider a stable explosive at ambient pressure.

The best experiment so far is in the Nature article from Loubeyre, linked by @Entropianabove, but you might rather look at the summary, which doesn't require a subscription.  The only mention regarding stability is "Moreover, they discovered that this transition is reversible." which in context means the reflectivity indicating they had a metal appeared as pressure went up and disappeared as it went down.  

Googling also quickly finds (at the US Office of Science and Technology) suggestions of using hydrogen metal to make light-weight cars, and much much more.  Exciting speculation with no evidence easily gets around the world --- and cited in what you would think to be authoritative sources --- before the boring reasons to curb our enthusiasm can catch up.   It is a common situation, so it is worth getting used to dealing with such situations, without getting upset.

Edited November 3, 2020 by OHara
repair link

[Vanamonde]

Some comments removed. Keep it on-topic, please. 

[KerikBalm]

11 hours ago, OHara said:

Nevertheless, if you google metallic hydrogen you quickly find Harvard University publishing in 'Science' magazine:  "Moreover, other predictions suggest solid metallic hydrogen (SMH) is metastable at room temperature when the pressure is released (Brovman, 1972). The combination of these expected properties makes SMH important for solving energy problems and can potentially revolutionize rocketry as a powerful propellant (Silvera, 'Conceptual launch vehicles...')."   One has to read carefully to notice the unjustified slide from "predictions suggest X" to "these expected properties " including X.

The "other predictions" is only one theoretical paper by Brovman and colleagues form 1972 that proposes a very strange structure for the metal, and describes it as metastable.  It is not clear to me what they mean by metastable.  The paper by Graham Ackland, that @Entropianlinked, suggests Brovman meant it would stay metal for some amount of time, and then Ackland computes the lifetime of the metal after releasing pressure to be <1 ps.  All theory, and no hint of what I would consider a stable explosive at ambient pressure.

To be clear. There has been only 1 paper suggesting metastability, and it wasn't really a prediction per se. 

http://www.jetp.ac.ru/cgi-bin/dn/e_034_06_1300.pdf

Quote

[...] it is not excluded in principle that there exists a metallic state of hydrogen at atmospheric pressure. It corresponds, however, to an energy lying much above the energy of the ground state of the molecular phase at P = 0 (and the densities of the two phases differ by almost one order of magnitude), and therefore the metallic phase will in this case naturally be metastable. An analysis of the actual realizability of such a metastable phase of hydrogen, which is actually of prime significance for all "terrestrial" applications, presupposes the solution of an entire series of interrelated problems.

1. Determination of the energy of the metallic state of hydrogen and the proof of the existence of a stationary point with respect to all the parameters characterizing the phase, and also the determination of the crystal structure corresponding to the lowest possible energy at P = 0.

2. Proof of the stability of such a phase. It should include a test for dynamic stability, and furthermore both in the long-wave limit and at excitations with arbitrary wavelength (reality of the phonon frequencies for the entire momentum space), and also a verification of the stability of the phase relative to thermal fluctuations.

3. Determination of a relation between the structure obtained at a pressure corresponding to the phase transition from the molecular to the metallic phase, and the structure of a metastable phase at atmospheric pressure (generally speaking the two structures need not necessarily coincide, and also an analysis of the processes occurring when the pressure is removed.

4. A determination of the lifetime of the metastable state (which should also include an analysis of the possible existence of a metastable phase at P < P* ).

The article then goes on to consider those problems, and in the conclusion:

Quote

In the Introduction we have formulated four problems, the solution of which would essentially answer the question of the feasibility and properties of a metastable metallic phase of hydrogen and the fundamental possibility of its production. The foregoing analysis solves the first two problems. Let us formulate first the results that will remain unchanged when the theory is subsequently quantitatively improved.

and:

Quote

As to the lifetime of the obtained state, which is metastable with respect to a transition to the molecular phase, this question, being purely kinetic and connected with nucleus-formation, remains open. It is interesting that, in principle, owing to quantum effects, this time is finite also at T = 0. Unfortunately, one cannot state that the lifetime will be sufficiently large, by virtue of the significant difference between the energies of the metastable phase and of molecular hydrogen at P = 0 and the small mass of the hydrogen ions.

Brovman 1972 never even really amounted to a prediction of substantial metastability. Brovman 1972 was speculation.

Subsequent theories (as linked by @Entropian , and myself multiple times earlier in this thread and others) show that speculation was unfounded, and predicted it to be "wildly unstable".

We now have 2 experiments that claimed to have made mH in a diamond vice, the latter being widely accepted, which showed no metastability. The first experiment, if it was successful, probably also showed no metastability judging by the sample loss.

@The Doodling Astronaut as you can see, we can more definitevly answer your question of "I would love to know where the information for doubts of stability are" than a question of "I would love to know where the information for doubts of magic pixe farts are". Magic pixe fart engines belong in the game more than mmH engines. We have no reason to think they exist, true, but there is no evidence against them. In the case of mmH, we have no reason to think it exists, and we do have evidence against it.