Why liquid hydrogen?

[Enoki]

I would think that by about TL 11 - 12 liquid hydrogen would have become something of a fuel of the past and replaced by either / or metallic hydrogen or monoatomic hydrogen. Both of these forms of hydrogen pack about 11 to 15 times more energy per unit volume than liquid hydrogen does. That would mean a massive reduction in tank size to fuel a ship leaving more room for other 'stuff' (a highly technical term there).

Metastable helium--assuming you can find the helium--would double what those forms of hydrogen could produce in energy. Maybe that happens at TL 13 or higher...?

Of course, all of these would require the appropriate machinery to manufacture and would only be "refined" fuels, but given their far higher energy densities it would likely be worth doing. Let's say the equipment to make these takes up 3 to 5 times the volume refining equipment currently does in the rules. That would still leave you with a net 2 to 3 times less fuel tank volume for a given ship requirement. That's huge in terms of advantage. More cargo and passenger space, more armament or whatever, but it is a net advantage to go to these instead of sticking to liquid hydrogen.

 

[Condottiere]

My theory is that when refined it becomes deuterium.

 

[mike wightman]

The jury is still out as to if metallic hydrogen is stable - you can always handwave it ny havving extremely strong artificial gravity mimicking the conditions at Jupiter's core.

Atomic hydrogen combines to form hydrogen molecules, you would have to put considerable energy in to stop this.

You can always carry hydrogen in a metallic lattice or as a hydrogen compound, water methane and ammonia all have more hydrogen per displacement ton than liquid hydrogen.

Fusing protons to form helium is not as easy as Traveller would have you believe.

 

[TamsinP]

And water has the advantage that it isn't cryogenic and any leak isn't going to result in suffocation of the crew due to a drop in the partial pressure of oxygen. Add to that the fact that (some of the) oxygen released from "cracking" water to get hydrogen for the reactor can be used to top up the life support system.

 

[spank]

You can always carry hydrogen in a metallic lattice or as a hydrogen compound, water methane and ammonia all have more hydrogen per displacement ton than liquid hydrogen.

I've always wanted to work up some rules for ISRU from methane, you could use iceball planets and comets as refueling points.

My personal thoughts are that hydrogen, via skimming, is probably the most readily available source, so that's the default. Liquid Hydrogen would be the most easily produced form, and should be locally available from TL 5 or so. Yes you probably could carry Hydrogen in other forms, but there'd have to be infrastructure to manufacture and handle it. And there'd have to be a way, on the ship, to turn it from whatever form it's stored in to something that can be used by the ship. Even in the case of Metallic Hydrogen, you'd have to have a feed system. Again liquid hydrogen wins the ease of use contest.

 

[spank]

And water has the advantage that it isn't cryogenic and any leak isn't going to result in suffocation of the crew due to a drop in the partial pressure of oxygen. Add to that the fact that (some of the) oxygen released from "cracking" water to get hydrogen for the reactor can be used to top up the life support system.

Yes, but.....
You'd have to be able to crack it at an extremely fast rate to keep up with the voracious appetite of a Jump drive.
IIRC jump uses 80% of the fuel in the initial impulse to get into Jump Space. So a J-1 Free trader would need 59,000 gallons of liquid hydrogen ready to go.

 

[Grav_Moped]

A few of us went over parts of this in the "Come Visit Rangent..." play-by-post thread, in discussing fuel refining processes and rates.

That discussion starts HERE.

 

[kilemall]

The jury is still out as to if metallic hydrogen is stable - you can always handwave it ny havving extremely strong artificial gravity mimicking the conditions at Jupiter's core.

Atomic hydrogen combines to form hydrogen molecules, you would have to put considerable energy in to stop this.

You can always carry hydrogen in a metallic lattice or as a hydrogen compound, water methane and ammonia all have more hydrogen per displacement ton than liquid hydrogen.

Fusing protons to form helium is not as easy as Traveller would have you believe.

Metallic hydrogen could also prove to be explosive. I have it as the core material in starship capacitors.

 

[Spinward Flow]

I have it as the core material in starship capacitors.

That's a very interesting notion!

 

[Enoki]

My theory is that when refined it becomes deuterium.

Makes no difference to use in a fusion reactor.

 

[Enoki]

I've always wanted to work up some rules for ISRU from methane, you could use iceball planets and comets as refueling points.

My personal thoughts are that hydrogen, via skimming, is probably the most readily available source, so that's the default. Liquid Hydrogen would be the most easily produced form, and should be locally available from TL 5 or so. Yes you probably could carry Hydrogen in other forms, but there'd have to be infrastructure to manufacture and handle it. And there'd have to be a way, on the ship, to turn it from whatever form it's stored in to something that can be used by the ship. Even in the case of Metallic Hydrogen, you'd have to have a feed system. Again liquid hydrogen wins the ease of use contest.

Only with current technology. We don't fully know what technology will become available in the future, but it is very likely that if metallic or monoatomic hydrogen are winners they will end up becoming 'the thing' in use.

 

[spank]

That assumes every port of call will have "future" technology. Alot of the ship in Traveller seem to be set up for more "frontier" or "backwater" conditions. With liquid hydrogen you can get it just about everywhere, and it's relatively easy to handle.

 

[Enoki]

That assumes every port of call will have "future" technology. Alot of the ship in Traveller seem to be set up for more "frontier" or "backwater" conditions. With liquid hydrogen you can get it just about everywhere, and it's relatively easy to handle.

I see this as just adding a new layer of options into the game. If you have a ship set up to use monoatomic or metallic hydrogen, it gives you an advantage. The disadvantage would be fewer places--say only TL 12 + worlds--have it available on a regular basis. While this would be disadvantageous to ships that go to backwaters and low-tech systems, it would be a huge advantage to larger freighters, liners, and megacorps that run their ships on a set route knowing the fuel would be available.

You might also have that special tank to handle these when you can get them to extend your own operating time or provide say, a second jump without refueling. That could be very handy for someone doing something like smuggling or the like. If you have run and jump ASAP, having that spare, if more expensive, fuel aboard could save you from 20 years in a labor camp...

 

[kilemall]

That's a very interesting notion!

Since they are available at TL9, means they are attainable with grav tech that can squeeze them into stability and are a key part of jump tech.

Also explains the explodey past capacity part. In my damage/scuttle rules, 3 tons of exploding capacitors roughly equals one nuke.

It is speculated that metallic hydrogen may have superconducting and superfluid properties. I’m just nudging it into the explodey battery role.

Metallic hydrogen - Wikipedia

en.m.wikipedia.org

 

[Condottiere]

Ours is expensive and expansive, so rather would take my chances with water.

 

[spank]

Ours is expensive and expansive, so rather would take my chances with water.

Recently there was a thread about the trans-rift route, and that got thinking about the best way to ship hydrogen for refueling stations. I wondered about sending methane, or metallic hydrogen. Which could be refined onsite to liquid hydrogen.

 

[Condottiere]

Since I don't know the specifics, all I can say is either find in range oasis systems, and/or start hunting for the (nearby) great dirty space snowballs.

 

[Spinward Flow]

I would think that by about TL 11 - 12 liquid hydrogen would have become something of a fuel of the past and replaced by either / or metallic hydrogen or monoatomic hydrogen.

The basic advantage of L-H₂ is that it is both backward compatible with the stone early fusion era technologies and also something of a "reliable common denominator" in foundational fuel technology systems. As soon as you start thinking in terms of In Situ Resource Utilization (ISRU) in a wilderness refueling capacity, L-H₂ starts becoming THE LOWEST COMMON DENOMINATOR of chemistry that can be obtained from an incredibly wide variety of feedstocks and locations.

Additionally, although metallic hydrogen may be denser in terms of energy per unit volume, that also means that metallic hydrogen is more energetic when disrupted into failure modes ... such as when damaged during battle. Fuel hits that vent 1% of my fuel tanks (or 10 tons minimum) is a much better outcome in damage control terms than fuel hits that ... ... destroy the craft.

Note that the same can be said of anti-matter fuels, which will be even more energetic when disrupted into failure modes than metallic hydrogen would be.



If all you're thinking about is PURE energy density, without concern or regard for cost, safety, availability or (passive) damage control procedures in the event of an emergency (I would classify battle damage as such an emergency) ... then sure, load up your craft with the highest density, most energetic fuel sources you can!

What could possibly go wrong?



Oh ...
Um ...

 

[whulorigan]

Perhaps this is an opportunity to re-examine the entire presupposition behind "refined" versus "unrefined" fuel.

In the beginning Traveller simply specified that ships could skim gas giants for unrefined fuel, or pay for refined fuel at a Starport that provided refined fuel (or get a fuel purifier/refinery for onboard your ship after HG'79), both for the "Power-Plant" and Jump Drives. It was left largely unspecified as to what exactly that unrefined (vs. refined) fuel and Power Plant were (though most people had a pretty good idea). Later game material filled in the details. But even later (after Fusion Power was explicitly established) it was largely unspecified as to exactly what kind of Fusion reaction was occurring in that Power Plant (i.e. what isotopes were employed in the reaction). What exactly was being refined from the raw gas giant "gas".

So let's go back to basics and brainstorm without any prior preconceptions or presuppositions, other than that Fusion is occurring in the Power-Plant.

What specific isotopic fuel(s) are necessary for the Fusion reaction of the Power Plant Reactor and/or Jump Drive?

• Protium (Light Hydrogen) ? - Does it use straight Protium in a catalytic reaction (with other elements) or straight Proton-Proton?
• Deuterium ? - Can it produce its own Tritium in a deuterium-fired Fusion pre-burner?
• Light Helium w. Deuterium ?
• Is the reaction catalyzed by nuclear damper-mediation and/or Muonic (or other heavy-particle) interaction ?

What Unrefined Liquid/Gas might a ship be expected to be able to skim and store in its tanks in a Frontier-refueling situation?

• Does it store impure L-H2 or L-D2 ?
• Does it store impure liquid methane? Heavy Methane?
• Does it store impure liquid ammonia? Heavy Ammonia?
• Does it store impure liquid water? Heavy Water?
• Does it need a Helium reserve?

All of the above can be found in some small percentage in a gas giant atmosphere. Some can be found in lakes and ice moons.

What might make the whole "refined" vs. "unrefined fuel" a "thing" again in a Traveller setting that Starports might find it economical to provide "Refined Fuel" (or Unrefined Fuel) as a purchase option at a port setting?

 

[Enoki]

The basic advantage of L-H₂ is that it is both backward compatible with the stone early fusion era technologies and also something of a "reliable common denominator" in foundational fuel technology systems. As soon as you start thinking in terms of In Situ Resource Utilization (ISRU) in a wilderness refueling capacity, L-H₂ starts becoming THE LOWEST COMMON DENOMINATOR of chemistry that can be obtained from an incredibly wide variety of feedstocks and locations.

Additionally, although metallic hydrogen may be denser in terms of energy per unit volume, that also means that metallic hydrogen is more energetic when disrupted into failure modes ... such as when damaged during battle. Fuel hits that vent 1% of my fuel tanks (or 10 tons minimum) is a much better outcome in damage control terms than fuel hits that ... ... destroy the craft.

Note that the same can be said of anti-matter fuels, which will be even more energetic when disrupted into failure modes than metallic hydrogen would be.



If all you're thinking about is PURE energy density, without concern or regard for cost, safety, availability or (passive) damage control procedures in the event of an emergency (I would classify battle damage as such an emergency) ... then sure, load up your craft with the highest density, most energetic fuel sources you can!

What could possibly go wrong?



Oh ...
Um ...

I'm also looking at the volume it occupies. Since this would be on the order of say 10% of what liquid hydrogen takes up, protecting the storage tank(s) would be greatly simplified. It could be compared to storage of say avgas to jet fuel on an aircraft carrier. The former requires special precautions and care in handling to prevent fires while the later is safe to store in simple tanks as it is hard to ignite.

For merchant shipping the reduction in volume means more room on the same tonnage for cargo and passengers raising profitability. Such ships would not be designed with combat in mind, just safety in everyday operations. For ships that need to do multiple jumps without refueling, being able to store say 5 jumps worth of fuel in the same volume using metallic hydrogen would be a huge bonus.

Or, even storing a relatively small amount of metallic hydrogen would allow a ship to run its systems for months off it before refueling even when using L-hyd for jumps. Again, a big advantage over constant refueling.

How dangerous it would be is a matter of how stable it is rather than how much explosive force is involved. If it were relatively stable and required considerable effort to detonate it--think TNT compared to nitroglycerine--it could well be worth the risks involved in storing and using it. At this point, we really don't know what that property of metallic hydrogen is.

Within the game, we have grav technology, materials that are harder than diamond, and other advanced materials, so it is entirely likely that both metallic and monoatomic hydrogen exist in usable quantities by cost effective production means. Even if these were limited to say TL 12+ and only available at class A and B starports (aka refined fuel), they could be seen as the 'hi octane' alternative to L-hyd.

I'm not suggesting one replaces the other but that technology allows the use of all three as the situation and economics permits.