Ice Refuelling

[whulorigan]

But the thing I'm still not getting is this; if the compounds in question are operating under PV=nRT conditions, only in a different realm of energy, then why would an astronomer call the solid crystal forms "ices"? Is it a matter of convenience?

Yes, exactly. It is a piece of "in-house" jargon among planetary astronomers. A shorthand term to describe a class of chemical substances.

 

[whulorigan]

GM: "You land, only a word of warning. There are ice shards out there moving at 600mph, and crashing against your hull. If you try to breath outside you'll both dry clean and flash freeze your lungs...although technically it is nitrogen-oxygen. Did I mention it's well below zero out there? Like, really below zero?"

The scenario would work fine on a world perhaps somewhat similar to Titan, where there is a thick N₂ atmosphere (about 1.5 atm) and the temperature is near the triple-point of CH₄ (meaning you can have solid, liquid, and gaseous methane, and perhaps methane/ethane lakes & seas, and hydrocarbon "rain/snow-storms").

If your atmosphere has free O₂, you will have to account for why that is, since O₂ is highly reactive chemically and will not last long (on astronomical time-scales) without some process producing/replenishing it. On Earth, that process is photosynthesis. (It could always be a legacy of ancient planetary "re-engineering/planetforming", of course).

In general though, I would avoid trying to have any type of "landing" on the "surface" of a Jovian or Neptunian world, since the conditions there are almost invariably (under current astrogeological theory) hyper-pressure and torrid temperature. There might be a liquid or solid "surface", but you wouldn't want to attempt a landing there. In fact, a larger Jovian world might very likely have a deep "global ocean" of liquid metallic H₂ when its atmosphere gets sufficiently compressed beyond a certain critical depth.

 

[whulorigan]

T4 M-Drives (Revisited)

BTW, I was puttering around on the T4 CD-ROM, and found these expanded descriptions of how the various M-Drive work according to the T4 Ruleset:

T4-SSDS Rules (Revised) p.7-13:

ContraGravity (tech level9+)
ContraGravity drives are not real maneuver drives, and aren’t useful outside of a gravity well. Their primary use is gravity vehicles. They are included here so that ships below tech level 11 (thruster plates) can hover and maneuver in an atmosphere. By 10 diameters out from a planet, the ContraGravity drive is virtually worthless, only producing 1% of the thrust it would on the surface. Note that the accelerations . . . can only be achieved in a 1G gravity well. Ships that use ContraGravity still need another form of maneuver drive to get out to jump distance. Normally, only enough CG is installed to counter the mass of the ship (use 10x displacement tons as a rule of thumb).

Fusion Drive (Tech Level 9)
A fusion rocket is not much more than a fusion reactor with a steady stream of hydrogen going in one end and a hole in the other. Super-heated hydrogen plasma expelled at tremendous velocities forms the reaction mass. Because of the nature of the drive, the exhaust is extremely dangerous. It cannot be used within planetary atmospheres, and ships which intend to land must have some form of auxiliary drive, such as ContraGravity. Other ships passing through the hydrogen wake will generally do so quickly enough that they won’t suffer any ill effects, unless extremely close (~200km, referee’s discretion). In that case, each crewperson must make a Difficult roll versus Constitution to avoid incapacitation by radiation (Average if wearing radiation-protective clothing), and each system on the ship suffers a minor damage result. All crew will require blood and bone-marrow therapy over the next several months to avoid long-term health problems. If the ship has sufficient sickbay space, this can be done on board. Otherwise, it must be done at a local hospital. Because of this effect, many systems have restrictions on the use of fusion drive within the local traffic area (10 planetary diameters). Restrictions range from strict control as to when and where the drive may be aimed for course changes, to requiring the drive to be “run rich,” increasing the fuel flow tenfold to dilute the effects somewhat. This also reduces the drive’s thrust. Note that the fusion drive does not require power, it generates excess power for use by other ship’s systems.

High Efficiency Plasma Recombustion (HEPlaR) Drive (Tech Level 10)
HEPlaR consists of a heat exchanger and recombustion chamber added to any power plant. Hydrogen is injected into the recombustion chamber, and the power generated by the power plant heats the hydrogen to a plasma state, causing a small fraction of the hydrogen to undergo damper-mediated fusion. The plasma is then released as a high velocity stream of reaction mass, providing thrust. Note the power required . . . and make sure it’s included in your power requirements when you select a power
plant. The prices and volumes . . . may seem like a bargain compared to the other drives, but remember: you still need a power plant!

Thruster Plates (Tech Level 11+)
Another effect of the tech level 11 mastery of gravitics (the science of gravity) is the invention of thruster plates. Earlier contra-grav technology only negates the effects of a gravitational field: thruster plates actually use the field itself for propulsion, by ‘grabbing on’ to the curvature of space and running along it much like an ant on the slope of a sugar-bowl. Rather than wasting valuable mass by hurling it out the rear of the ship, as lower-tech rockets do, gravity drives use the stellar system itself as their reaction mass (much as a train pushes against its track, and the planet below, rather than by expelling exhaust). A small change in a star’s momentum translates to a huge velocity change for the much smaller spacecraft. Unlike the ant of the earlier example, however, the slope of the “bowl” has a different effect on gravitic-drive ships. They depend on the slope for propulsion. Beyond a certain point, quantum-gravitic effects drastically reduce the efficiency of a gravitic-drive ship, by a factor of a hundred or more, and thus they cannot maneuver effectively in deep-space (empty) stellar hexes on the star map unless they have an auxiliary drive, though they can remain there while, for example, computing jump parameters. The cutoff parameter turns out to be around 2,000 solar radii. Beyond this point, thruster plates are virtually worthless for anything beyond stationkeeping, and some alternate form of propulsion is needed. Thus, the Drenid Deep Space Research Facility in Silea system is still resupplied using an automated freighter driven by a fusion rocket. Another disadvantage of thruster plates is their gravitic and visual signature: gravity-wave sensors can easily detect the peculiar emissions characteristic of the system. Normal telescopic sensors are approximately as useful: the ‘thruster plates’ themselves give off exotic particles, which very quickly decay as they leave the thruster field. The bright blue glow emanating from the rear of many new Imperial vessel is, perhaps, more distinctive than the subtle space-warp.

 

[HG_B]

BTW, I was puttering around on the T4 CD-ROM, and found these expanded descriptions of how the various M-Drive work according to the T4 Ruleset:

T4-SSDS Rules (Revised) p.7-13:

Yes. T4 had different "Thrust Plates" than in MT. MT's weren't Grav drives. MGT's Grav Drives don't experience performance degradation when away from a gravity well. 3 different drives. 3 different rule sets.

 

[whulorigan]

Yes. T4 had different "Thrust Plates" than in MT. MT's weren't Grav drives. MGT's Grav Drives don't experience performance degradation when away from a gravity well. 3 different drives. 3 different rule sets.

And T5's Drives seem to be direct descendants of the T4 drives described above.

 

[HG_B]

And T5's Drives seem to be direct descendants of the T4 drives described above.

That's what I predicted before T5 came out.

 

[esampson]

Yes. T4 had different "Thrust Plates" than in MT. MT's weren't Grav drives. MGT's Grav Drives don't experience performance degradation when away from a gravity well. 3 different drives. 3 different rule sets.

But what can be noted is that the maneuver drives in T4 do appear to produce some form of exotic particle exhaust that you would want to direct away from the ship, so there could definitely be seen to be a need for large 'nozzles' out of the back.

In all fairness to your point of view those nozzles should be shaped more like giant exhaust pipes rather than nozzles since they are producing exhaust and not thrust, but that might be handled through some more minor handwaving aspects (perhaps the inner diameter is constant but the mechanism to help direct the particles away from the ship needs larger coils closer to the ship or something).

That would seem to indicate the need for 'exhaustozzles' (a mechanism that might be a nozzle or an exhaust port) on the back of ships in 2 of the 5 versions of Traveller, unneeded in 1 of the 5, and undecided in 2 of the 5 (though if T5 engines are merely new versions of T4 that would move them from undecided to necessary in 3 out of 5. However that requires making a not completely supported assumption).

 

[HG_B]

so there could definitely be seen to be a need for large 'nozzles' out of the back.

Nozzles THAT large? Only if one had ZERO idea of proportion. They would be SUB atomic particles.. o:

 

[Vladika]

But what can be noted is that the maneuver drives in T4 do appear to produce some form of exotic particle exhaust that you would want to direct away from the ship, so there could definitely be seen to be a need for large 'nozzles' out of the back.

In all fairness to your point of view those nozzles should be shaped more like giant exhaust pipes rather than nozzles since they are producing exhaust and not thrust, but that might be handled through some more minor handwaving aspects (perhaps the inner diameter is constant but the mechanism to help direct the particles away from the ship needs larger coils closer to the ship or something).

That would seem to indicate the need for 'exhaustozzles' (a mechanism that might be a nozzle or an exhaust port) on the back of ships in 2 of the 5 versions of Traveller, unneeded in 1 of the 5, and undecided in 2 of the 5 (though if T5 engines are merely new versions of T4 that would move them from undecided to necessary in 3 out of 5. However that requires making a not completely supported assumption).

Expanding nozzles make sense from an engineering point of view as gasses will tend to expand rapidly, especially in a vacuum. There is pressure in a "pipe" and the quicker the gas is released the better.

BTW if there is any mass propelled away from the ship there will be thrust to overcome, albeit a small amount.

 

[esampson]

Nozzles THAT large? Only if one had ZERO idea of proportion. They would be SUB atomic particles.. o:

It's not the size of the particles that is important but the total volume. After all, the molecules of gas leaving a Saturn V rocket engine aren't large at all compared to the diameter of its nozzle.

Also, the description said that the engines emitted 'exotic particles which quickly decay'. Exotic particles are not required by definition to be subatomic. They are merely particles with extremely unusual properties. Tachyons would be a form of non-subatomic exotic particle as would exotic matter with a negative mass (the type that is proposed for use in holding open the throat of a wormhole or maintaining an Alcubierre drive).

 

[esampson]

Expanding nozzles make sense from an engineering point of view as gasses will tend to expand rapidly, especially in a vacuum. There is pressure in a "pipe" and the quicker the gas is released the better.

BTW if there is any mass propelled away from the ship there will be thrust to overcome, albeit a small amount.

Yes, however the exhaustozzles drawn on the back of most ships appear to contract rather than expand, which is why I said they don't really appear correct as simple exhaust tubes. That could be dealt with through some minor applications of phlebotinum to the exhaustozzles such as I was suggesting.

As for the tiny amounts of thrust produced, yes, that is absolutely true, so it would make sense to apply that exhaust so that those tiny amounts add to everything else. No sense in letting it go to waste (and besides, projecting the particles in the same direction as your 'thrust' means you get away from them faster).

 

[Blue Ghost]

The scenario would work fine on a world perhaps somewhat similar to Titan, where there is a thick N₂ atmosphere (about 1.5 atm) and the temperature is near the triple-point of CH₄ (meaning you can have solid, liquid, and gaseous methane, and perhaps methane/ethane lakes & seas, and hydrocarbon "rain/snow-storms").

If your atmosphere has free O₂, you will have to account for why that is, since O₂ is highly reactive chemically and will not last long (on astronomical time-scales) without some process producing/replenishing it. On Earth, that process is photosynthesis. (It could always be a legacy of ancient planetary "re-engineering/planetforming", of course).

In general though, I would avoid trying to have any type of "landing" on the "surface" of a Jovian or Neptunian world, since the conditions there are almost invariably (under current astrogeological theory) hyper-pressure and torrid temperature. There might be a liquid or solid "surface", but you wouldn't want to attempt a landing there. In fact, a larger Jovian world might very likely have a deep "global ocean" of liquid metallic H₂ when its atmosphere gets sufficiently compressed beyond a certain critical depth.

I was under the impression that both Neptune and Uranus actually had surfaces, unlike Saturn or Jupiter.

 

[Blue Ghost]

On thrusters; I saw a blurb on an old technology the other night. The kind of thing that could have revolutionized aviation, but was moderately ahead of its time.

I think I understand a little better both Marc Miller and Keith Brothers vision of maneuvre drive, what it was, how it worked, and how it might have been fuelled, and why the rules are written the way they are. Maneuver drive, as originally intended was not a chemical "rocket" technology, but a high energy thrust.

Later iterations in newer rules took that original concept, and threw in a lot of hand waves. Marc Miller's conception is based on real technology and science. Newer "thrust" drives are assuming breakthroughs in physics that, even for Traveller, are a little high concept. YMMV and YTUMV, and everything else that goes with house rules and various interpretations, but Traveller's "desire" to lean towards real science, I think is somewhat undercut by the thrust plate theory/advancement.

I mean, manuvre drive takes up space in engineering for a reason.

 

[whulorigan]

I was under the impression that both Neptune and Uranus actually had surfaces, unlike Saturn or Jupiter.

Well, to be perfectly frank, we can't be entirely sure, since we have never sent a probe that far down (that would be able to survive). According to most planetary formation models (and some data received from the probes we have sent to those planets), all 4 of our gas/ice giants theoretically have some rocky core under hyper-pressure if you get down far enough. Even Jupiter may have some type of roughly earth-sized rocky core under thousands of miles of liquid metallic H₂. It is just that with Uranus and Neptune, they are under less pressure than Jupiter or Saturn (but still extreme - at the point where the "gaseous" H₂atmosphere comes in contact with the superheated amonia/water volatile ocean, the atmospheric pressure is about 100,000 atm, and the ocean itslef is about 3000⁰K. Eventually, under several 1000 miles of ocean (which is underneath all of that atmosphere), you will reach a rocky center.

But I wouldn't want to try and fly a ship there.

 

[Blue Ghost]

Every book I've read or doc I've seen says that both have pretty icy surfaces, but that Neptune is volatile with surface winds that approach mach 1. Last I heard Neptune had a solid surface of sorts, but the geography was a mystery because of all of the high velocity blue gasses covering the place.

On Oxygen; I think you mean free flowing O that been broken off from other elements. We could suppose that the atmosphere is actually NO2 Any crew landing there might get frozen and suffocate, but at least they'll have a smile on their face.

 

[whulorigan]

Every book I've read or doc I've seen says that both have pretty icy surfaces, but that Neptune is volatile with surface winds that approach mach 1.

If you mean "ices" by the astronomer's definition I have given above (i.e. an "ice" = "volatile substance"), then yes. And ammonia and water are "ices" or "volatiles" by that definition. But they are superheated to a few thousand degrees under several thousand miles of crushing H₂ atmospheric pressure.

What books have you been reading on the subject, and how long ago were they published?

Last I heard Neptune had a solid surface of sorts,

That would be the rocky core under hyper-pressure that I mentioned above.

but the geography was a mystery because of all of the high velocity blue gasses covering the place.

The bluish color of the ice-giants is due to the presence of methane. The methane in the upper atmosphere absorbs red wavelengths, leaving the light reflected by the topmost layers of the atmosphere a bluish color.

 

[Blue Ghost]

To be honest it's been years, so my data is dated, but I'll go get up to date on the latest, and then see how it gybes with our discussion.

 

[Shonner]

What do you do, how do you do it, and all that other stuff

I see cool role-play situations where vibrating ice cutters/chompers cause an avalanche on top of the parked ship. Or a star is rising and causing the ice to crack and spray jets from the cracks. The weight of the ship, and the increasing slope of the ice drift your on, is not helping things.

 

[Jame]

I see cool role-play situations where vibrating ice cutters/chompers cause an avalanche on top of the parked ship. Or a star is rising and causing the ice to crack and spray jets from the cracks. The weight of the ship, and the increasing slope of the ice drift your on, is not helping things.

That is pretty cool, though I myself see it on a non-Jovian, terrestrial world.

 

[Blue Ghost]

Hmm, according to the last astronomy book I bought (back in 1991 or 1992), both Uranus and Neptune were speculated to have an "ocean mantle"; i.e. a rocky core surrounded by water that is many many miles deep. The upshot is that both worlds are less dense than the Earth, and the gravity is something a Traveller ship with greater than 1g accel could easily escape.

At the top of the clouds (ionosphere?) the temperature for both worlds is around 58 to 57 K. That's cold! Which leads one to speculate about the "biosphere"; i.e. the surface of the ocean; is there a hard frozen surface that is constantly cooled, or is there a tumultuous massive ocean there that is constantly whipped into a frenzy by mach 1 winds?

Wow.

Don't land there. Go for that ice moon. Set up shop, grab your ice, stay nice and warm in your ship, then jump back to civilization when you can.

Here're some pics I found

Loose tangent; the rules as to how much pressure a starship can take would seem to allow a type S 100 ton scout to land on a Neptune or Venus, though it would be a very rough ride once you were down.

Loose tangent 2; per my previous reference to Venus to clarify astronomical jargon, here's a cleanup processed picture from the Soviet Mariner probe;