[FlamingCobra]

In general, the melting point of a metal increases with pressure, right?

[redsniper]

Uh... I think maybe slightly. It wouldn't be as dramatic as how boiling point changes with pressure though.

[FlamingCobra]

Does that mean that tantalum hafnium carbide could remain a solid in Earth's outer core?

[redsniper]

Idk, look up a phase diagram for that.

EDIT: Looks like those aren't readily available.

So, TaHfC has a theorized melting point of 4215 °C. Buuuut... "The temperature of the outer core ranges from 4400 °C in the outer regions to 6100 °C near the inner core." Cutting it really close there. Even if TaHfC could remain solid, it would be so close to it's melting point, and thus so soft, as to be kind of useless.

[Mars]

. . . 

Iron, which melts at comparatively cool 1538 degrees exists as the solid core of our planet. The immense pressure keeps it that way. Something with a melting point of 4000 would certainly be solid, but would be unlikely to remain at the core, as it is likely less dense than Iron/Nickle/Cobalt

(EDITED: Grammar derp)

[Mars]

Ima leave this here: Clausius–Clapeyron relation

[redsniper]

Hmmm, guess I derped there. Melting point probably doesn't change that much with pressure, but the pressure down there is just SO DAMN HIGH that stuff will stay solid at preposterous temperatures. I thought this thread was going to take the path of "well if this stuff can stay solid, let's build a probe/ship/vessel out of it and go down in the core," which I was kind of trying to preempt by saying the material would likely be significantly weakened by the heat. But yeah, if you could force a lump of this TaHfC down there, it would stay solid, sure.

[FlamingCobra]

Hmmm, guess I derped there. Melting point probably doesn't change that much with pressure, but the pressure down there is just SO DAMN HIGH that stuff will stay solid at preposterous temperatures. I thought this thread was going to take the path of "well if this stuff can stay solid, let's build a probe/ship/vessel out of it and go down in the core," which I was kind of trying to preempt by saying the material would likely be significantly weakened by the heat. But yeah, if you could force a lump of this TaHfC down there, it would stay solid, sure.

no. I was thinking we COULD do that but I wasn't suggesting it actually be done.


I was also wondering why the movie The Core had to create Unobtainium when TaHfC would work. Especially since TaHfC was discovered in...... what...... the 40s?




Besides, a far better application would be to send such a probe down to the core of Venus and see why the **** it doesn't have a dynamo.

But I am saving all things Venus for another topic.

[Mars]

No, it had to be made of unobtainium for far more reasons than that. The material would have to be hard enough at high enough temperatures to deal with getting dragged across millions of meters of stone at thousands of degrees. The drill would have to function through increasing temperatures (that would normally kill mechanics because of thermal expansion) without a head replacement, once again, for nearly six million meters of solid, ultra high density, scorchingly hot rock at incredible pressures, all while keeping a crew made of meat alive. The pressure would basically crush any man made structure ever like a bubble.

Pressure is the key here, not just the temperature. And hardness. And thermal expansion. And conductivity.

[FlamingCobra]

So no material known to man would work irl?

Not even TaHfC glazed with diamond?

Not even......... graphene?



Cuz........ I remember watching this show on discovery channel one time....... and they said it could be done irl with a ship made of diamond......

[Mars]

To my (highly limited) understanding no, but I could be wrong.

EDIT:

Carbon matrices can be really impressive I know. My guess is anything they could potentially come up with IRL would be some sort of composite made out of lots of different things. Also, Discovery says some weird things sometimes, especially late at night.

[FlamingCobra]

I know the aforementioned movie contained an almost uncountable number of scientific inaccuracies but I was trying to find a way around it.


Mostly because of the potential applications for Venus.


Now, I am rather uneducated on the subject, but wouldn't placing nukes in the core of Earth blow our planet apart rather than restart the core?



EDIT: Also, titanium isn't as great as it is made out to be. Tungsten, Depleted Uranium, Vanadium, and Zirconium on the other hand, are another matter entirely.

EDIT 2: Is graphene really a room-temperature superconductor?

[Mars]

Venus's surface, though inhospitable, is definitely not nearly as unconquerable as Earth's core. If we weren't limited by the expense of putting significant tonnage over there, and if we had nothing better to do, we could have people go down there for days at a time I'd bet. As it is though, its simply not practical to send heavily armored probes out there only to fizzle out after several minutes.

<EDIT>

Point being, I highly doubt that the best efforts of the world could actually get living humans down to the core.

[FlamingCobra]

Mars, I was thinking about terraforming Venus.

If we could find a way to start its core it would generate a magnetic field of its own. Having a dynamo in its core would also restart plate tectonics...... I think.


I believe it would be difficult to keep Mars terraformed because there would be no magnetic field to prevent its atmosphere from escaping.

EDIT: Maybe if we had a "grid" of satellites in orbit around Mars we could generate an artificial magnetic field but that would be rough.

[Mars]

I do believe Venus has a magnetic field, the thing that makes it uninhabitable is its atmosphere. Ima go check real quick

[FlamingCobra]

Venus has an induced magnetic field as a result of solar winds.

EDIT:
Also, venus' rotation is slow as FUUUUUUUUUUUUCCCCCCCCCKKKKKKKKKKKKK




also, venus got ****ed up the way it did because the carbon cycle stopped. the carbon cycle stopped because plate tectonics stopped. why plate tectonics stopped, i don't know.



but we gotta move this to another topic.

[Mars]

You're right.

[FlamingCobra]

yes. I have heavily studied venus on Wikipedia and various other sites.


Furthermore, isn't the tidal forces from the moon at least part of the reason that the earth's core is *still* spinning?


The reason I bring this up is because, to our knowledge, Venus never had a moon.

[redsniper]

The other thing is, any crew or instruments inside your 'ship' are going to fry. Even if you had some double-walled vessel like a thermos, with the inside suspended by magic and not touching the outer shell at all, enough heat would radiate in from the outer wall to burn it all to hell. Also yeah, pressure. My mind reels to think about how thick your walls would have to be to withstand the pressures you'd see down there.

[Mars]

Now, I am rather uneducated on the subject, but wouldn't placing nukes in the core of Earth blow our planet apart rather than restart the core?

Actually, unless it was a whole lot of nukes, I rather doubt you'd see much of anything happen. You have to figure your average hurricane unleashes many thousands of times the energy of a nuke. Nukes just put out a lot of energy that soft, fleshy things like us don't do well in.

EDIT: Also, titanium isn't as great as it is made out to be. Tungsten, Depleted Uranium, Vanadium, and Zirconium on the other hand, are another matter entirely.

That has everything to do with application. Titanium is light and strong. Tungsten and Depleted Uranium aren't nearly as strong per weight, but they're exceedingly dense, useful as kinetic penetrators or armor against penetrators / gamma rays. Vanadium and Zirconium are actually not all that impressive on their own, but are useful in niche applications and in steel.

No idea about graphene.