Ice Refuelling

[whulorigan]

T4 Drives

The thing is that a grav drive is not automatically reactionless. That is simply an assumption. In the other thread examples were given as to how a gravitic drive might not be reactionless.

True. To be clear, I am using the term "reactionless" in the sense that the drive in question does not require reaction mass to be thrown out the back of the ship. So a grav-based Thruster-Plate might not technically be "reactionless" if it is reacting against masses/grav-fields.

So unless they state in T4 that the grav drives were reactionless (or that the weren't) the best we have is 'vague' (because in all fairness while it is possible for a gravitic drive to not be reactionless it is just as possible for it to be).

From T4 Core Rules p. 92:

There are two types of maneuver drive: HEPlaR and Thrust.

HEPlaR Drive: At TL10, the standard maneuver drive is a variant of fusion rocket using High-Energy Plasma Recombination (HEPlaR). These drives require both electrical power and fuel for reaction mass.

To install a HEPlaR maneuver drive, cross-index the size of the hull with the maneuver Gs desired on the HEPlaR Drive Potential Table for the volume of the drive in displacement tons. To find the other characteristics of the drive, including the fuel required for 20 hours of operation, use the drive size on the Standard HEPlaR Drives table.

Thrust-Plate Drive: The thrust plate drive is developed at TL12, and is the standard spacecraft drive from that point onward. It uses gravitic principles, and requires only electrical power to operate.

To install a thrust plate drive, cross-index the maneuver Gs required with the size of the hull on the Thrust Plate Drive Potential Table to determine the drive’s volume (in displacement tons). Use the Standard Thrust Plate Drives Table for other characteristics of the drive.

 

[McPerth]

I was quite disappointed by T4 and never studied well its starship building system, but in pages 96-97 of the starship book they appear tables for the high efficiency countergrav drives (TL12) and for thuster drives (TL11). As said, I cannot tell you details on them, but I guess they are reactionless.

And in MgT, while the MDrives are not well described (at least in the books I have access to) they don't need reaction mass, and fuel is only required by the JD and PP, regardless of the MD you have.

 

[whulorigan]

I was quite disappointed by T4 and never studied well its starship building system, but in pages 96-97 of the starship book they appear tables for the high efficiency countergrav drives (TL12) and for thuster drives (TL11). As said, I cannot tell you details on them, but I guess they are reactionless.

The High-Efficiency Contragrav are for Grav Vehicles.

The Thruster Drives are for Spacecrraft M-Drives.

 

[esampson]

True. To be clear, I am using the term "reactionless" in the sense that the drive in question does not require reaction mass to be thrown out the back of the ship. So a grav-based Thruster-Plate might not technically be "reactionless" if it is reacting against masses/grav-fields.

From T4 Core Rules p. 92: []
Thrust-Plate Drive: The thrust plate drive is developed at TL12, and is the standard spacecraft drive from that point onward. It uses gravitic principles, and requires only electrical power to operate.

To install a thrust plate drive, cross-index the maneuver Gs required with the size of the hull on the Thrust Plate Drive Potential Table to determine the drive’s volume (in displacement tons). Use the Standard Thrust Plate Drives Table for other characteristics of the drive.

Precisely. Now, what if the mass that the drive reacts against isn't something that is carried? It could be interplanetary hydrogen projected at near relativistic speed (or just whatever the atmosphere happens to be made of when you are in an atmosphere). It could be elementary particles created from the interruption of quantum perturbation similar to how Hawking radiation is created. There's all sorts of possibilities. It could also be that the drive somehow interacts directly with the larger mass and uses it as the reaction mass, ships lifting off disturbing the planet's orbit ever so slightly in the same way that a large aircraft carrier sailing around ever so slightly alters the rotation rate of the Earth.

It's entirely possible that the grav drive is not reactionless and yet is still unsuited to melting ice. It is additionally possible that the drive is completely reactionless but still well suited to melting ice (do to the production of waste energy in the form of heat or other forms of energy that quickly convert to heat). That's why I said there were a lot of variables that have not been well defined in the Traveller canon.

 

[esampson]

. . .And in MgT, while the MDrives are not well described (at least in the books I have access to) they don't need reaction mass, and fuel is only required by the JD and PP, regardless of the MD you have.

Actually, I doubt they say that don't need reaction mass. What you are doing is interpreting the fact that the don't have to carry reaction mass as not needing it.

A Bussard ramjet doesn't carry reaction mass (or at least it isn't obligatory) but that doesn't mean it doesn't use it. Solar sails, likewise, carry no reaction mass but are not reactionless drives.

 

[whulorigan]

Precisely. Now, what if the mass that the drive reacts against isn't something that is carried? It could be interplanetary hydrogen projected at near relativistic speed (or just whatever the atmosphere happens to be made of when you are in an atmosphere). It could be elementary particles created from the interruption of quantum perturbation similar to how Hawking radiation is created. There's all sorts of possibilities. It could also be that the drive somehow interacts directly with the larger mass and uses it as the reaction mass, ships lifting off disturbing the planet's orbit ever so slightly in the same way that a large aircraft carrier sailing around ever so slightly alters the rotation rate of the Earth.

Yes that was the point of my quote upthread:

True. To be clear, I am using the term "reactionless" in the sense that the drive in question does not require reaction mass to be thrown out the back of the ship. So a grav-based Thruster-Plate might not technically be "reactionless" if it is reacting against masses/grav-fields.

The drive may react by directly "pushing-off" of a mass thru an as-yet not understood aspect of gravity, pushing the star/planet in an opposing direction ever so slightly.

 

[HG_B]

The thing is that a grav drive is not automatically reactionless.

For the intents & purposes of that definition as used in Traveller they are.

 

[HG_B]

And in MgT, while the MDrives are not well described (at least in the books I have access to) they don't need reaction mass, and fuel is only required by the JD and PP, regardless of the MD you have.

In MGT, Chem MD's require additional "fuel". Only the Grav reactionless drives can work with only a fusion PP.

 

[esampson]

For the intents & purposes of that definition as used in Traveller they are.

Perhaps as you use them. I've seen an awful lot of pictures of ships with what appear to be large exhaust nozzles and plenty of games in which the exhaust of the maneuvering drive is a concern.

I've also seen plenty of instances where the ships lift off smoothly, so I'm not saying that you can't interpret the drives as working that way. I'm simply saying that your position that they must work that way is no more supported than any other.

 

[HG_B]

Perhaps as you use them.

As used in the Trav universe. I just happen to use the same.

 

[Blue Ghost]

I posted some man-hour labor figures earlier on in the thread, if that helps anyone.

Thrusters, as I've always understood them, are not reactionless, otherwise they wouldn't work. They might have some reactionless qualities in terms of how they're fired up, but they do push your vessel. I'm assuming there's lots of heat and light being kicked out the nozzles, that would be more than enough to melt a good chunk of anykind of ice.

If you're on a world that's so cold that it has cryovulcanism (I was actually writing an adventure with that title two days ago), then you'd better be careful that the ice you're on top of (assuming you landed on an ice sheet) isn't housing an ocean of liquid methane, nitrogen or some other super cooled liquid. That could mean BIG trouble.

 

[HG_B]

Thrusters, as I've always understood them, are not reactionless, otherwise they wouldn't work. They might have some reactionless qualities in terms of how they're fired up, but they do push your vessel. I'm assuming there's lots of heat and light being kicked out the nozzles,

No. That wouldn't be enough to perceptibly move a Trav ship.

 

[esampson]

As used in the Trav universe. I just happen to use the same.

As has been shown, there are multiple examples in the Traveller universe that implicitly contradict you and few that expressly support you (and those few are countered by examples that expressly contradict you).

Now I am not saying that you must play that there is some sort of exhaust coming from the engine. There isn't any more support for that position than for yours. What I am saying is that your statements that this is how it works in Traveller are unsupported.

You want to say that it is how it works IYTU, knock yourself out. You want to say that it worked that way in MT. Absolutely. You want to claim that it has always been this way or even that it has been this way the majority of the time and I will point out that you are arguing from an unsupported position.

 

[esampson]

. . .
If you're on a world that's so cold that it has cryovulcanism (I was actually writing an adventure with that title two days ago), then you'd better be careful that the ice you're on top of (assuming you landed on an ice sheet) isn't housing an ocean of liquid methane, nitrogen or some other super cooled liquid. That could mean BIG trouble.

You actually probably wouldn't have to be much more careful than if you landed on a planet with 'traditional' volcanism (i.e. you would want to be sure that the ground you are on isn't housing an ocean of liguid magma).

There's probably a small amount of extra care due to the tensile strength of ice being lower but I would imagine not a whole lot. If the planet has cryovolcanos everywhere spewing forth ice and methane then yes, you would definitely be careful, much as if you were landing on a planet where conventional volcanos were spewing forth magma left and right.

If you were landing on a planet where there was much lower incidents of cryovolcanic activity I would imagine it would be much like landing on a planet that has much lower incidents of volcanic activity, such as Earth. You would be careful if you were landing near areas exhibiting active volcanos but otherwise, it's probably not a big deal.

Remember that to the cryocreatures of Deneb IV who evolved in an ocean of liquid methane Earth is a hellish planet with vast seas of molten ice that will evaporate and fall from the skies in a searing rain. In some ways it is all about perspective.

 

[Jeff M. Hopper]

So to get a little bitty into the nitty gritty of my questions....

OK, you have isolated the water ice and have melted it and are electrolysizing it into hydrogen and oxygen. Can you then recycle the oxygen with the methane to 'burn' it and provide heat plus more water to be eltrolysized? What about the ammonia and carbon dioxide, can similar helpful reactions be found for them?

You have a ship moving slowly relative to a dense comet tail or a ice ring system, you have your main cargo bay doors open, how much of a velocity difference do you want while letting the ice chunks collect in your cargo bay? I'm thinking enough so that is a fairly quick process, and enough so that when the chunks hit the interior bulkhead they shatter and partially melt from the impact, but not so great that you damage the interior or exterior of the ship.

 

[Vladika]

I'm thinking enough so that is a fairly quick process, and enough so that when the chunks hit the interior bulkhead they shatter and partially melt from the impact, but not so great that you damage the interior or exterior of the ship.

Try throwing a several hundred pound chunk of ice at your car and see what happens.

 

[esampson]

So to get a little bitty into the nitty gritty of my questions....

OK, you have isolated the water ice and have melted it and are electrolysizing it into hydrogen and oxygen. Can you then recycle the oxygen with the methane to 'burn' it and provide heat plus more water to be eltrolysized? What about the ammonia and carbon dioxide, can similar helpful reactions be found for them?

You have a ship moving slowly relative to a dense comet tail or a ice ring system, you have your main cargo bay doors open, how much of a velocity difference do you want while letting the ice chunks collect in your cargo bay? I'm thinking enough so that is a fairly quick process, and enough so that when the chunks hit the interior bulkhead they shatter and partially melt from the impact, but not so great that you damage the interior or exterior of the ship.

Methane is CH₄, so you would probably be better served breaking it down into hydrogen and carbon. The power plant of a starship runs off of hydrogen fusion (converting hydrogen atoms to helium). In 7 days that power plant will go through umpty-scrunch cubic meters of hydrogen, just in normal use. Unless it has some sort of mind-bogglingly high inefficiency you've got all the energy you need to melt ice and perform electrolysis on it. Burning the methane would be sort of like using a butane lighter on someone who is being blasted by a blow torch. Sure, it's more energy but such a tiny amount in relative terms that it would have negligible appreciable impact.

What do you do with that extra oxygen, carbon, and nitrogen? For the most part you probably just throw it away. Certainly you would first take the time to top off any storage supplies you might have (all three might have uses in life support; oxygen and nitrogen for the ships atmosphere, carbon as some sort of filtering agent) but because you will need tens of tons of hydrogen you will produce far, far more oxygen, nitrogen, and carbon then you should have any reasonable use for (even counting setting up a reasonable supply for emergencies).

As for the issue with the cometary tail/ice ring and what you do with the chunks, I would guess you probably don't really want to deal with chunks. You probably want to scoop up the massive amounts of tiny particles that won't impact your ship with any significant amount of force using the standard intake scoops. Not only are they less damaging but there's an awful lot more of them out there then the bigger chunks.

 

[aramis]

In CT 2nd, MT, MGT, GT, it was "reactionless". I believe TNE also. So, almost always it is so.

Not in TNE. TNE and T4 gravitics negate weight; weight is reduced by 98%. (Remember: weight part of is the effect of gravity upon a mass.) But they do not produce thrust.

T4 has optional gravitic thrust.

 

[HG_B]

Not in TNE.

Yes, this was corrected down thread already...

 

[Carlobrand]

...If the Traveller ships in your universe have any sort of high temperature exhaust then I'd probably use my engines to melt a big honking puddle. Gravity on Europa is a bit over .13 G's so I'll bet that with .1 G of thrust and my contragrav lifters I shouldn't have much problem (.1 G is actually a very large amount of acceleration. We're just not use to thinking of it as being very much when we play Traveller).
...

Triple point of water is 0.01 degrees C at about 0.006 atmospheres. Europa's atmospheric pressure is something like 10^-12 atmospheres. Heating the ice in those circumstances means it goes straight from ice to vapor.

So, heating it directly with engines or radiators isn't effective, not unless you've got some atmosphere around. You've got the problem of trying to suck up water vapor that's trying it's best to expand into the local near-vacuum atmosphere while you're doing it - most of the vapor's going to expand off into vacuum. You've got to find some way to enclose what you're heating so you can get the bulk of the vapor that results.

There might be some engineering solution; I'm not an engineer by any stretch of the imagination. However, I don't think the conventional "sucking it up in a tube" idea's going to work when you're mostly in vacuum to begin with and your target's turning straight to vapor, not unless you find some way to confine the vapor while it's being produced.