Ice Refuelling

[esampson]

. . .The Thrusters in MT, however, were described by DGP in SOM as being based on the "Strong Nuclear Force", not gravitics, and they "pushed against" their own Thruster-plates. . .

Huh. I missed that entirely. I thought that they pushed against their own thruster plates with a modified version of the grav drive. I didn't realize it was based on strong nuclear force.

Thanks.

 

[McPerth]

This doesn't mean that gravitic drives must behave this way. It is entirely possible to have one of the first two versions I outlined (reactionless and reaction) which would create an environment in which people could stand right next to a launching ship. All it means is that when you look at a version of Traveller (or any sci-fi for that matter) and all it says is 'gravitic drive' that doesn't mean it is reactionless and without exhaust.

In the CT adventure Exit Visa is told that the captain is afraid because the ship was involved in an accident where it took off with people near and at least one of them died. That could hint there's some kind of reaction, be it just exhaust or a gravity field that could crush people, but makes me clear people may not stand near a taking off ship.

It is the 3rd Law: For every action there is an equal and opposite reaction.

Rockets use this principle. "Grav drives" either "push" against an existing large mass. Like a planet. Or, in the case of deep space grav drives that don't have efficiency drop off, create their own grav field for the ship to "fall" into. The 2nd definition is NOT a reaction drive. The 1st type of Grav drive is not either but one can make torturous semantic attempts to make it so.

Then I understand a biplane propeller is also a reaction drive, according your deffinitions. Maybe just a language matter (as both in Spanish and Catalan when you talk about a reaction engine (motor a reacción in Spanish, motor a reacció in Catalan) or plane you're alking about a jet (so an engine that expells the reaction mass), as opposite to a propeller.

MT's Thrust Plates: "Upon reaching TL 11, breakthroughs in quantum physics leads to REACTIONLESS thruster plates. Faster and more efficient than grav propulsion systems" (they aren't Grav drives)...

But, IIRC, it also says that it was reached because of greater understanding of gravitics, so telling they are also gravitic drives, even though when you talk about gravitic drives you're usually refereing to the lower TL ones that are affected by gravitic fields...

 

[whulorigan]

In the CT adventure Exit Visa is told that the captain is afraid because the ship was involved in an accident where it took off with people near and at least one of them died. That could hint there's some kind of reaction, be it just exhaust or a gravity field that could crush people, but makes me clear people may not stand near a taking off ship.

If the gravitic drive is being imagined as a reaction drive that is "pushing off" of a mass, then anything between the drive and the mass being pushed against will feel the thrust of the drive as a crushing force. As the distance between the drive motor and the "planetary mass" increases, the "pushing force will be spread out over a larger area and so will drop off in intensity per unit area on the planetary surface. But being right behind it would be deadly.

In TNE: FF&S, this is described in the alternate technologies section as a "Gravitic Displacement" Drive. (Remember that in TNE, the standard gravitic lifter was "Contragravity", which merely nullified gravitational attraction - it did not produce any thrust).

 

[HG_B]

Then I understand a biplane propeller is also a reaction drive, according your deffinitions.

Yes. According to Newton they are.

But, IIRC, it also says that it was reached because of greater understanding of gravitics, so telling they are also gravitic drives, even though when you talk about gravitic drives you're usually refereing to the lower TL ones that are affected by gravitic fields...

No. They aren't grav drives. While learning about the nature of gravity they had breakthroughs in OTHER areas of physics. It is probably a language barrier you're running into.

 

[esampson]

In the CT adventure Exit Visa is told that the captain is afraid because the ship was involved in an accident where it took off with people near and at least one of them died. That could hint there's some kind of reaction, be it just exhaust or a gravity field that could crush people, but makes me clear people may not stand near a taking off ship.

Precisely. Even though the ship might be powered by a 'grav drive' doesn't mean it doesn't have some kind of exhaust. That is really my major point.

Then I understand a biplane propeller is also a reaction drive, according your deffinitions. Maybe just a language matter (as both in Spanish and Catalan when you talk about a reaction engine (motor a reacción in Spanish, motor a reacció in Catalan) or plane you're alking about a jet (so an engine that expells the reaction mass), as opposite to a propeller. . .

That is a little more of a matter of semantics, in all fairness. As a general rule you wouldn't refer to a propeller as a 'reaction drive'. You would refer to it as a 'propeller'. As a general rule when you are talking about a 'reaction drive' you are referring to a specific subset (rocket motors and jets). Sort of the same way that when a person refers to a 'calculator' they are referring to a pocket calculator and not a PC, abacus, or any one of a number of devices that might fit within the broader category of 'calculator'.

A gravitic drive, however, might fall into the category or 'reaction drive' similar to jets and rocket engines because it is possible that it provides thrust through the ejection of reaction mass. We can't say without more specific information about how the drive functions. However, as your earliest example points out it appears likely that there is some form of reaction mass that the drive ejects.

How is that possible since the ships don't carry reaction mass? The ships might take the reaction mass from the universe at large in some fashion (back to elementary particles and quantum perturbations). Maybe the ships actually do carry reaction mass, using small amounts of hydrogen fuel to provide the reaction mass. While we typically say that it is the power plant using it all and we don't track the precise amounts of thrust used to see how much fuel it uses up (with the exception of TNE) maybe that's just to prevent another book keeping headache.

All sorts of possibilities. All I'm really saying is that just because something is labelled 'gravitic drive' that doesn't mean there's no exhaust.

 

[HG_B]

That is a little more of a matter of semantics, in all fairness. As a general rule you wouldn't refer to a propeller as a 'reaction drive'.

Um, yes you would if you were talking about the principles behind its operation.

 

[esampson]

If the gravitic drive is being imagined as a reaction drive that is "pushing off" of a mass, then anything between the drive and the mass being pushed against will feel the thrust of the drive as a crushing force. . .

That's not a given. It is possible that the drive works through some form of more direct interaction with the gravitational force of the planet. Anything getting between the two might not be affected at all. Alternately the amount of energy it receives might be a factor of its own mass so as a result it is receiving orders of magnitude less force then that being exerted on the ship (as it has orders of magnitude of lower mass).

Of course it is also possible that the intervening object will get squashed flat as a pancake. I'm just saying that when you're dealing with the amount of hand waving already involved you can't really say that it would have to act this way or that.

 

[esampson]

Um, yes you would if you were talking about the principles behind its operation.

Correct. If you were talking about the principle behind the operation.

On the other hand you (probably) wouldn't describe a Cessna as a 'twin-react' to someone.

Semantics is probably the wrong word for me to have used in that instance. I suppose I should have said it was a matter of context.

 

[McPerth]

Um, yes you would if you were talking about the principles behind its operation.

If so, I guess even a train or a car caould be seen as reaction moved, and I guess not many people will call them as reaction moved vehicles...

 

[esampson]

If so, I guess even a train or a car caould be seen as reaction moved, and I guess not many people will call them as reaction moved vehicles...

I doubt people will call them 'reaction moved' because currently any form of drive is a reaction drive (in that sense of the word).

No one has currently found a way around action/reaction although the EmDrive would appear to do that if it functions as claimed. It should be noted that the creator of the EmDrive claims that it doesn't violate action/reaction, though I can't find anything where he explains how it doesn't, and that many other scientist argue that the EmDrive itself is a fraud.

 

[Jeff M. Hopper]

You know those thrust venturii at the backs of most starship designs? For gravitic drives I just say that they are heat exchanger vents where the superheated helium is exhausted from the fusion plant.

 

[HG_B]

You know those thrust venturii at the backs of most starship designs? For gravitic drives I just say that they are heat exchanger vents where the superheated helium is exhausted from the fusion plant.

I just call them for what they are. Artist drawings done by those who didn't/don't understand the game universe.

 

[esampson]

I just call them for what they are. Artist drawings done by those who didn't/don't understand the game universe.

No. Just one's who didn't/don't understand your view of the game universe.

How rude of them not to consult with you personally.

As I have pointed out, MT is the only version in which those nozzles are clearly wrong. In all other editions the need for them is at worst ambiguous.

 

[Carlobrand]

No. Just one's who didn't/don't understand your view of the game universe.

How rude of them not to consult with you personally.

As I have pointed out, MT is the only version in which those nozzles are clearly wrong. In all other editions the need for them is at worst ambiguous.

I mentioned this once (about got my head bit off, but I'm a stubborn cuss): you could use them in atmosphere as part of a system that drew in the local atmosphere and applied waste heat to it to get a bit more boost.

 

[Blue Ghost]

Also note: Though you would not want to attempt a landing on the "surface" of an Ice-Giant (Neptunian) world, such worlds are invariably orbited by small ice-moons, where the volatiles are ices in the forms we are more familiar with (cold/snowy/"icy", etc). A non-skimming refueling operation would likely be conducted there, rather than the Ice-Giant itself.

Hmm, I guess I'm still a babe in the woods on specific astronomy references and terminology. Having said that, having taken a couple of astronomy courses with calculus and engineering chemistry, I'm always under the impression that ice crystals referenced in programs for lay people, are in fact "ice" as you and I understand it in an everyday day sense; i.e. ammonia ice crystals in Jupiter or Saturn's atmosphere, again as I understood the term, referenced actual ice comprised of different elements to form an "ice" molecule in the form of a kind of sleet, hail or even snow. That's in reference to ice in jovian bodies.

As an extension of that framing, I was always under the impression that an ice is an ice is an ice, and that ice or snow on a Neptune or Uranus would be just that, albeit a deadly implement under the torrential winds on both worlds.

Now, to further muck things up, but perhaps to clarify as well, it's my understanding that Venus lower atmosphere, even though it is an atmosphere as you and I understand it, has the "thickeness" or "consistency" of water. The reason I bring this up, is because it sounds like when scientists refer to an ice, or an atmosphere, they're, as you state, referring to a layer of material under certain conditions.

Do I have that right?

 

[Blue Ghost]

Actually, I pretty much made up the specific example of the Denebians on the spot. I'm sure, however, that more than one sci-fi author has created fairly detailed creatures that come from a super-cold climate and probably with that same point of view.

I first realized the arbitrary nature of how we view things like that a few years ago when a new exoplanet was discovered and people were postulating that it was so hot that it would 'rain molten rock'. I read that and thought 'huh. And is that really so different from Earth where it occasionally rains molten ice?'.

There is actually a little blurb about a race of ice beings being carted through the streets of Capital looking with awe at the "hellish environment" in which the Imperium exists. It's somewhere, and I seem to recall it being in Mega-Traveller...unless I read your little thing somewhere years ago

 

[Blue Ghost]

Comment on drives; to me Traveller drives are cinematic combos of Star Wars, BSG, Space 1999, Buck Rogers, and bear little relation to contemporary rockets. I always imagined that the maneuvre drive was a powerplant engine that spun up energy and kicked it out the aft to get the ship to move; creating a cacophony of noise amidst a dull glow of blue or white.

The "reactionless" grav-derived drive is lost on me. No such creature, or rather it's the Mazda rotatory engine of starship drives; neat, kind of an impressive alternative, but not really more reliable nor efficient by any other conventional drive at the same tech level.

 

[whulorigan]

Hmm, I guess I'm still a babe in the woods on specific astronomy references and terminology.

Don't feel bad. Astronomers seem to love to use terminology in ways that defy common sense usage. They still call Blue Stars "early", and Red Stars "late" as a hold-over from 150 years ago when they thought stars radiated their energy due to gravitational contraction and cooling.

Having said that, having taken a couple of astronomy courses with calculus and engineering chemistry, I'm always under the impression that ice crystals referenced in programs for lay people, are in fact "ice" as you and I understand it in an everyday day sense; i.e. ammonia ice crystals in Jupiter or Saturn's atmosphere, again as I understood the term, referenced actual ice comprised of different elements to form an "ice" molecule in the form of a kind of sleet, hail or even snow. That's in reference to ice in jovian bodies.

As an extension of that framing, I was always under the impression that an ice is an ice is an ice, and that ice or snow on a Neptune or Uranus would be just that, albeit a deadly implement under the torrential winds on both worlds.

This is correct if you are in the upper atmosphere of one of the gas or ice giants, where the temperatures can easily be below -150⁰C or more, and the pressure is much less. There the ices behave much as you would normally think of ice (sleet/snow, etc). But the atmosphere there is still primarily H₂, and you are nowhere near the "surface". As you move downward, and the temperature and pressure increase, the "ices" start behaving in odd ways, turning to liquid or solid with odd properties due to the extreme conditions.

Now, to further muck things up, but perhaps to clarify as well, it's my understanding that Venus lower atmosphere, even though it is an atmosphere as you and I understand it, has the "thickeness" or "consistency" of water.

Venus' atmosphere is CO₂, but at the surface it has a pressure of 90 atm and is about 450⁰C, meaning that "wading" thru it would feel much like wading thru a dense liquid. I believe it is still technically a gas at this point, just under very high pressure (about the equivalent-pressure of a half-mile under Earth's Oceans - close to modern submarine-hull crush depth). Winds are only a few miles per hour, but considering the density, they would produce considerable force.

The reason I bring this up, is because it sounds like when scientists refer to an ice, or an atmosphere, they're, as you state, referring to a layer of material under certain conditions.

Do I have that right?

Specifically astronomers, not necessarily scientists in general.

An atmosphere basically means a gaseous envelope of any density. If the density and pressure cause the atmosphere (or another substance) to liquify, then that substance would generally be called a sea or ocean.

Concerning Ices (or more appropriately "Volatiles") - if you will permit another wikipedia synopsis:

http://en.wikipedia.org/wiki/Volatiles

In planetary science, volatiles are the group of chemical elements and chemical compounds with low boiling points that are associated with a planet's or moon's crust and/or atmosphere. Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide. In astrogeology, these compounds, in their solid state, often comprise large proportions of the crusts of moons and dwarf planets.

In contrast with volatiles, elements and compounds with high boiling points are known as refractory substances.

Planetary scientists often classifly volatiles with exceptionally low melting points, such as hydrogen and helium, as gases (as in gas giant), while those volatiles with melting points above about 100 K are referred to as ices. The terms "gas" and "ice" in this context can apply to compounds that may be solids, liquids or gases. Thus, Jupiter and Saturn are referred to as "gas giants", and Uranus and Neptune are referred to as "ice giants", even though the vast majority of the "gas" and "ice" in their interiors is a hot, highly dense fluid that gets denser as the center of the planet is approached.

 

[Blue Ghost]

Well, okay. I guess what I'm having a hard time is the physical concept of what an ice is on the surface of an "ice giant".

Caveat; when I started this thread I had more or less an Io or Europa kind of scenario; i.e. a relatively calm moon as you say, where there might be mountains of methane, ammonia, or just plain water snow, and a loner pilot/engineer with some navigational software for his 100 ton Type-S, lands and shovels what he needs into the fuel bins.

As an extension of that, and recalling the documentaries on the Voyagers and their fly byes of Jupiter and Saturn, and more "relatively" recently, Neptune and Uranus, cryovulcanism was mentioned; and the explanation was that the relative temperature and matter states found among our experiences with things like molten rock, liquid water and so forth, were "shifted" to a lower temperature realm where the same kinds of physical phenomena took place, but just with different substances that took the place of molten rock; i.e. you had liquid nitrogen or whatever spewing forth from a geyser because the pressure underneath the ice was warm enough for that volume of solution to punch through a weak point in the surface (which was described as ice) to create a "cryo volcano".

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?

Anyway, the lady astronomer who was explaining cryovulcanism, said with a smile how she imagined what it would be like to stand on the surface of one of the moons of Neptune or Uranus, where cryovulcanism was noted to take place, and feel the atmosphere on her skin and whipping through her hair. We all know she was talking poetically, but one wonders how cold it would be

 

[Blue Ghost]

A bit of a post script here; years ago I had a few adventure concepts that addressed extreme conditions on other worlds, where the adventurers had to venture forth. I had the equivalent of an astronomy minor in terms of education under my belt, but it was like all the cool themes of strange ancient aliens OTHER than the "Ancients" (Droyne) were verbotten at the time (or at least that was my impression). And so it was that I shelved some of those concepts. But, now that we're discussing what could be called extreme environments, I'm getting stirrings to write some of those concepts up again.

GM; "So, this old eccentric billionaire amateur researcher is willing to shell out a meg for each of you to take him to Tarsus, to look for some strange ancient lost city and artifact."

Players; "Cool, we're in. Tarsus? That's that forest world. Guns, ammo, some light armor...we're good."

GM; "And he has a flight profile already set up."

Players; "We're good. Let him play pilot for a while. As long as we get paid."

*Time and Play passes*

GM; "So you exit jump, but you're a little far from Tarsus. In fact, you're a couple of AUs out from Tarsus."

Players; "Wow, that's weird. Scan the area. Why are we so far out?"

GM; "And the flight profile is still operating. You're landing on Elias."

Players; "Elias? Huh? Wha--? Is that a moon or something?"

GM; "Eh, it's like an ice giant. Cold. Lots of ice."

Players; "Well, we got warm weather gear. We're good. But hack that computer anyway!"

*die rolls; fails*

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?"

Players; "That's b__l-sh_t!"

GM; "On the plus side your patron says the temple's only a day's walk away. Enjoy."



In all seriousness, players would know ahead of time, but seeing a group of players navigate that scenario would be most entertaining. A lot of Traveller sees to take place on Trek like "Class M" planets (a few exceptions), which is okay, but I think there's quite literally, whole worlds of adventure waiting to be explored.

Ah. Time to write some more