Liquid Hydrogen Detonation/Handling

[kilemall]

Let's say you take a hit from ye olde beam laser into an L-Hyd fuel tank- just how explosive should that be in a RL chemical/physics sense, given that most of the time it won't be mixing with oxygen for it's true explosive potential?

Also, should a fuel hit be far more catastrophic in planetary atmo with oxygen then in space?

I am suspecting our default fuel is at once safer then many would like to assume, and more dangerous under some circumstances then the rules tend to generate.

While looking into all this, ran across this gem of an article, by THE NASA L-Hyd handling expert.

https://www.nasa.gov/pdf/513855main_ASK_41s_explosive.pdf

Finally, I am assuming the 1% leakage issue is largely solved by TL8-9, combo of material science and perhaps gravitic microrepulsion built into the tanks. Do you have a solution for hydrogen leakage IYTU?

 

[WistfulD]

We don't have a mechanism, we just don't cover the leakage (so the superscience effects of ignorium).

As to the fuel tank hit-- the laser will energize the hydrogen to a phase change, just as it did the slagged hole in the hull. This will cause expansion as liquid turns to gass, and could cause a pressure explosion. This, however, is just the same for liquid H2 as it is for water, except that water has a specific heat of 4.187 kJ/kgK and a latent heat of vaporization of 2,270 kJ/kg, while H2 is 9.78 kJ/kgK and 445.6 kJ/kg, respectively. So no big explosion, but maybe a small pressure explosion. Mostly a hole in the hull leaking precious fuel.

If that happens in an O2 atmosphere, it probably would ignite, but likely as the hydrogen leaves the ship, so no further damage. The fire wouldn't enter the tank (and potentially cause an internal explosion) until the pressure inside the tank was less than that outside the tank. At that point, most of the gasified H2 would have already been expelled, and the fire would find itself with liquid (i.e. cool) H2 and very little internal oxygen, and thus probably wouldn't ignite the rest of the tank.

Whether you can get the tank resealed before the rest of your hydrogen boils off, on the other hand...

 

[Spartan159]

Just as self sealing tanks were developed for internal combustion engine fighter planes, I could see self sealing hydrogen tanks being developed after a few space combat instances or even just for micrometeorites. Or handwavium /shrug

 

[kilemall]

We don't have a mechanism, we just don't cover the leakage (so the superscience effects of ignorium).

As to the fuel tank hit-- the laser will energize the hydrogen to a phase change, just as it did the slagged hole in the hull. This will cause expansion as liquid turns to gass, and could cause a pressure explosion. This, however, is just the same for liquid H2 as it is for water, except that water has a specific heat of 4.187 kJ/kgK and a latent heat of vaporization of 2,270 kJ/kg, while H2 is 9.78 kJ/kgK and 445.6 kJ/kg, respectively. So no big explosion, but maybe a small pressure explosion. Mostly a hole in the hull leaking precious fuel.

If that happens in an O2 atmosphere, it probably would ignite, but likely as the hydrogen leaves the ship, so no further damage. The fire wouldn't enter the tank (and potentially cause an internal explosion) until the pressure inside the tank was less than that outside the tank. At that point, most of the gasified H2 would have already been expelled, and the fire would find itself with liquid (i.e. cool) H2 and very little internal oxygen, and thus probably wouldn't ignite the rest of the tank.

Whether you can get the tank resealed before the rest of your hydrogen boils off, on the other hand...

That's my read of the stuff in space. Assuming we are chilling it to cryogenic levels routinely, unless we foolishly keep our oxygen atmo up in the ship it will explode very locally and in limited fashion.

I would expect vents and ultimately blow out panels on the tank and hull to prevent pressure from doing damage laterally or to the interior.

Don't know about self-sealing tanks, difference between bullet holes and big chunks torn out, especially with bay weapon/spinal strikes.

Assuming self-sealing is not practical (and I'm thinking you'll lose the cryogenic level of temp in any case), the stuff will just boil off anyway, which is a preferred state to hanging around the ship in a gaseous "please leak oxygen so it can become a fuel air explosive-like detonation" situation.

Nice thing about these fuel tanks is they can be a second-rate armor, AND thanks to their cryogenic state act as a shield to internal IR generation.

Has starship layout implications, perhaps you relocate the power plant and bridge/computer to the spine of the craft even if unarmored? Course the reverse may be true in the advent of the meson gun era.

Perhaps another potential military use is to cool off those hot lasers, PAs and railguns to increase ROF?

I'm thinking conversely every captain sweats the atmo portion of takeoff and landing, having a magazine explosion strapped to the belly of their ship. Maybe standard civilized starport A/Bs require empty fuel tanks coming and going, and topping off/selling back once in orbit as a safety measure?

 

[kilemall]

Oh, and the NASP was intended to cool off by running liquid hydrogen along the hull then recapturing it for extra thrust.

https://fas.org/irp/mystery/nasp.htm

I don't know about the scramjet aspect given that most of our ships won't takeoff fast enough to make it worthwhile, but could explain another use for our fuel and relatively mundane business of reentry.

 

[GypsyComet]

While the situation has actually come up in a game I was in, the fairly small body of published Traveller-derived fiction has only used the volatile nature of hydrogen fuel once that I recall. One of Jeff Swycaffer's books mentions a port fuel disaster that leveled the terminal and startown and killed thousands. The disaster had since become a handy sinkhole for false identities, since having a false family die in that disaster meant no one could easily expose your forgery.

 

[WistfulD]

Perhaps another potential military use is to cool off those hot lasers, PAs and railguns to increase ROF?

Well, that large tank full of liq. H2 is a decent heat sink that you have to have handy and already have to maintain at that temperature, but you really have to maintain it at that temperature. Hydrogen's critical temperature as 33 K; critical pressure, 13.3 atmospheres; and boiling point, 23 K. That's not a lot of degrees you can heat it up before it gasifies, and what are you going to do with it then? Okay, half the time a ship is going around with parts of its fuel tankerage empty, but turning liquid to gas means your volume needs increase dramatically. The best solution is water, with it's ridiculous specific heat and 100 degrees of liquid phase to work with, a whole lot of rock (asteroid embedded weapon), or radiators aimed away from your enemy's sensors.

I'm thinking conversely every captain sweats the atmo portion of takeoff and landing, having a magazine explosion strapped to the belly of their ship. Maybe standard civilized starport A/Bs require empty fuel tanks coming and going, and topping off/selling back once in orbit as a safety measure?

It really depends on how you think of ships in your game universe (something Traveller has been relatively inconsistent about). In reality, damage such that there might be a fuel explosion is probably fatal on re-entry regardless of the fuel explosion (ex. space shuttle Columbia didn't need an explosion, the hole by itself was fatal). If, on the other hand, big lumbering ships with Star Wars like hulls, combined with contragravity (and the precident that combat-damaged ships can attempt reentry at all) suggest that maybe Traveller ships are sturdy enough that they could survive a holed hull, such that a fuel explosion could make the difference between survival and not.

 

[kilemall]

Re IMTU, I don't have antigrav ships, except special ones that expend space and money to do so. Most 'economy' ships don't.

On the other hand I am postulating a deflector system that is mostly about space hazards but partially an EW system and partially a variable virtual aeroform creating lift for takeoff and landing.

A hole in the hull might be able to be glossed over/protected from the full impact by the deflectors, but if it's a big enough hole it will have blown away the protecting deflectors and therefore the protection is not there. Best aeroskip back up to above atmo if possible for a patch and a docking at the station.

 

[kilemall]

Got to thinking about another aspect, the unrefined fuel part.

Classic Traveller says the Type S can use unrefined fuel. Well, that's going to either be water, methane, ammonia, or 'dirty' liquid hydrogen mixed with whatever helium or whatnot.

So presumably our fuel purifiers are cracking out the oxygen/carbon/nitrogen or impurities to give us the clean L-Hyd, but there is no room for the purifier on a Type S.

Does that mean there is some cracker built into the standard scout engineering, or that the plant and drives burns the hydrogen directly and expels the 'extra' elements?

Does that universal hydrogen use translate into some other loss of capability, perhaps for instance Type S takes longer to load the jump drive with L-Hyd because it's cracking it along the way?

Or Type S is lighter built overall then most ships so the fuel can be heavier but on a conventional ship the heavier fuel would be a drag on G ratings?

 

[epicenter00]

I think L-Hyd detonation really depends on how "period" your Traveller is.

There's no reason why hydrogen tanks wouldn't be mounted in the hull in such a way that the loss of containment would be safely vented. A possible design for such a kind of "double-hull" design where the tank is in a vaccum with a blow-out panel towards space so if the tank fails and the safely hull is filled with hydrogen, it's vented to space; even a weak self-sealing system on the double-hull would encourage the venting gasses to go into space in the case of overpenetration.

Similarly, sense says that large areas of a ship would be deliberately depressurized before combat and everyone would be in spacesuit; not because of the risk of some "explosive depressurization", but because it'd massively reduce the fire danger. This is not an IMTU thing - it's touched upon in the Hard Times supplement that some ships do that during that time (though I think in there the reason mentioned is because atmosphere is hard to replace or something).

A more loony idea might be that hydrogen tanks might be towed behind a starship like the lifeboats in a 1800s warship going into combat; everyone knows its dangerous so they might just tow the tanks of hydrogen behind them; while an enemy might snipe at your hydrogen tanks, it's still safer than keeping it on-board.

However, if you're playing "period" Traveller based on more 1960s sci-fi, engineering spaces and so on might have atmosphere in it during combat (because various components might have issues with vaccum since you can fabricate repair parts using a machine shop with lathes and so on - as mentioned in T4), which would provide for plenty of oxygen to detonations, fires, and other fun stuff.

Does that mean there is some cracker built into the standard scout engineering, or that the plant and drives burns the hydrogen directly and expels the 'extra' elements?

In my experience, GDW is pretty infamous for playing fast and loose with their own design sequences. I've always figured that the Scouts have a "special" reactor-drive array with a purifier built in. Why this special engineering hasn't been extended to other ships remains a mystery.

 

[mike wightman]

Got to thinking about another aspect, the unrefined fuel part.

Classic Traveller says the Type S can use unrefined fuel. Well, that's going to either be water, methane, ammonia, or 'dirty' liquid hydrogen mixed with whatever helium or whatnot.

So presumably our fuel purifiers are cracking out the oxygen/carbon/nitrogen or impurities to give us the clean L-Hyd, but there is no room for the purifier on a Type S.

Does that mean there is some cracker built into the standard scout engineering, or that the plant and drives burns the hydrogen directly and expels the 'extra' elements?

Does that universal hydrogen use translate into some other loss of capability, perhaps for instance Type S takes longer to load the jump drive with L-Hyd because it's cracking it along the way?

Or Type S is lighter built overall then most ships so the fuel can be heavier but on a conventional ship the heavier fuel would be a drag on G ratings?

This is a result of 'rules evolution'.

In LBB2 CT military/scout engines were allowed to use unrefined fuel at no penalty - there are no rules or costs associated with this, the referee just decides if a particular design has scout/military grade engines.

LBB5 1st edition tried to introduce rules for the military ships, so we got things like better weapons, armour, screens and at last the purification plant. These rules are not compatible with LBB2 unfortunately.

 

[Condottiere]

Or you have the majority of the fuel in drop tanks, that you eject just before battle, or in the case of blow out panels concept, armour being between the tanks and the ship, getting hit there wouldn't matter.

 

[nobby-w]

Let's say you take a hit from ye olde beam laser into an L-Hyd fuel tank- just how explosive should that be in a RL chemical/physics sense, given that most of the time it won't be mixing with oxygen for it's true explosive potential?

...

Pretty much a non-issue unless it's in the presence of an oxidiser. SOP for a warship is to evacuate the ship for combat to avoid exploisive decompression on a breach (pretty sure I read that somewhere in the Traveller rule books).

Ergo, if you're getting into a scrap you won't have an atmosphere in the ship so the explosive nature of the L-Hyd fuel isn't going to be a problem.

 

[Spartan159]

Pretty much a non-issue unless it's in the presence of an oxidiser. SOP for a warship is to evacuate the ship for combat to avoid exploisive decompression on a breach (pretty sure I read that somewhere in the Traveller rule books).

Ergo, if you're getting into a scrap you won't have an atmosphere in the ship so the explosive nature of the L-Hyd fuel isn't going to be a problem.

If the L-Hyd gets into the internal portions of a ship the cryogenic nature might be an issue?

 

[nobby-w]

If the L-Hyd gets into the internal portions of a ship the cryogenic nature might be an issue?

Probably not a big issue for three reasons:

1. In space you're going to be subjected to temperature extremes anyway, so the ship has to be capable of handling temperatures from cryogenic up to hundreds of degrees celsius.
   
2. The L-Hyd will evaporate pretty quickly, venting into space and probably blowing most of the liquid with it due to the vapour pressure, so it won't hang around for very long.
   
3. Leidenfrost effect - L-Hyd touching warmer parts of the ship will vapourise immediately forming an insulating layer of gas that slows down the heat transfer. The gas will also escape rapidly into the vacuum, pushing the L-Hyd further away from any surface capable of vapourising a layer.

 

[kilemall]

Pretty much a non-issue unless it's in the presence of an oxidiser. SOP for a warship is to evacuate the ship for combat to avoid exploisive decompression on a breach (pretty sure I read that somewhere in the Traveller rule books).

Ergo, if you're getting into a scrap you won't have an atmosphere in the ship so the explosive nature of the L-Hyd fuel isn't going to be a problem.

Same rule you cite mentions that sensitive cargo may require atmo, and then the rule goes into how atmosphere control is compartmented in the ship.

I could see some crazy VIP/noble type insisting they won't get in a vacc suit as 'fun times' for a passenger steward, with possible choices to keep atmo on, especially if the crazy person chartered the whole ship.

 

[nobby-w]

Same rule you cite mentions that sensitive cargo may require atmo, and then the rule goes into how atmosphere control is compartmented in the ship.

I could see some crazy VIP/noble type insisting they won't get in a vacc suit as 'fun times' for a passenger steward, with possible choices to keep atmo on, especially if the crazy person chartered the whole ship.

By definition, if something has made a hole in the pressurised compartments that's letting L-Hyd into them then the compartment is now vented into space anyway.

 

[kilemall]

By definition, if something has made a hole in the pressurised compartments that's letting L-Hyd into them then the compartment is now vented into space anyway.

Yes, but now they are mixing and likely sploding.

I'd like to quantify that.

 

[aramis]

Yes, but now they are mixing and likely sploding.

I'd like to quantify that.

No, not likely to explode. Hydrogen is one of the safest flammables around.

Note that the fireballs we see from NASA are flamefronts, not explosions.

Hydrogen only burns in a limited range of oxygen mixtures, and only detonates in a much much narrower range.

The flash freeze is the threat.

 

[Condottiere]

Yet, at forty five percent capacity by volume, one of the first images pictured one would have would be: