Abusing an AHL

[Hemdian]

Here's a question that came up in game: can an Azhanti High Lightning class cruiser refuel from a world ocean directly (without using its fuel shuttles)?

On the one hand the image of 60K dtons of ship hovering in the air (over an ocean) in exactly the same way that bricks don't seems wrong. On the other hand the stresses (atmospheric and gravetic) of a gas giant skimming must surely be greater.

Thoughts?

Regards PLST

 

[Andrew Boulton]

Supp5 says no. GG refuelling is possible, but very dangerous.

 

[DaveShayne]

Originally posted by Hemdian:
Here's a question that came up in game: can an Azhanti High Lightning class cruiser refuel from a world ocean directly (without using its fuel shuttles)?

On the one hand the image of 60K dtons of ship hovering in the air (over an ocean) in exactly the same way that bricks don't seems wrong. On the other hand the stresses (atmospheric and gravetic) of a gas giant skimming must surely be greater.

Thoughts?

Regards PLST

Do you want the reality answer or the game rule answer?

For reality I'd say gas giant refueling is probably impossible and all of those pesky bits of flavor text are misinformed. For the game rules the AHL is listed as "Partially Streamlined" and capable of GG skimming but not landing on a planet.

 

[mike wightman]

The mission described in the MT folio adventure Arrival Vengeance relies on gas giant refueling by an AHL at times.
Surface refueling from an ocean is right out of the question though.

A TNE variant may be able to do it if fitted with a big enough contragrav lifter

 

[Tobias]

Originally posted by DaveShayne:
For reality I'd say gas giant refueling is probably impossible

Why? It's not like the ship must descend deeply into the Gas Giant. The upper layers of the "atmosphere" are probably quite enough. Although some flavor text does indeed imply that ships do indeed enter the lower GG atmosphere.

Regards,

Tobias

 

[RainOfSteel]

What happened to CT Supp 9: p.31: "Integral fuel scoops and on-board fuel purification plant. Design concepts make the ship depend on fuel shuttles rather than skim directly."

 

[DaveShayne]

Originally posted by Tobias:
</font><blockquote>quote:</font><hr />Originally posted by DaveShayne:
For reality I'd say gas giant refueling is probably impossible

Why? It's not like the ship must descend deeply into the Gas Giant. The upper layers of the "atmosphere" are probably quite enough. Although some flavor text does indeed imply that ships do indeed enter the lower GG atmosphere.

Regards,

Tobias </font>[/QUOTE]My first gut reaction is that if the exceedingly strong magnetic field doesn't get you the heat from the friction of the atmosphere or the 1000 kph huricanes will.

 

[mike wightman]

Originally posted by RainOfSteel:
What happened to CT Supp 9: p.31: "Integral fuel scoops and on-board fuel purification plant. Design concepts make the ship depend on fuel shuttles rather than skim directly."

Other rules happened.
The AHL is configuration 4, which gives it partial streamilining, which allows fuel skimming from gas giants.

The flavour text in S9 is derived from Supplement 5, which was originally a High Guard 1 design and thus unstreamlined. In S5 on page 43 it says that an AHL will fuel skim, but only as a last resort.

The Arrival Vengeance was specially modified to make fuel skimming a safer, more routine, operation.

 

[Tobias]

Originally posted by DaveShayne:
My first gut reaction is that if the exceedingly strong magnetic field doesn't get you the heat from the friction of the atmosphere or the 1000 kph huricanes will.

See, this is exactly what I mean. You don't need to dive so deeply that weather is a major problem. FWIW, even a small ESA exploration drone made quite a deep descent (pressure of 24 bar) before being destroyed. I think Traveller starships should be capable of this and more.

Regards,

Tobias

 

[DaveShayne]

Originally posted by Tobias:
I think Traveller starships should be capable of this and more.

Streamlined and partially streamlined ones are.

But we are talking about real world capabilities here. Traveller starships are capable of a lot of things that seem to be impossible in reality which is why I gave a seperate answer going by the rules.

Ask a physicist about waste heat radiation if you want to really ruin your fun.

 

[Tobias]

Originally posted by DaveShayne:
But we are talking about real world capabilities here. Traveller starships are capable of a lot of things that seem to be impossible in reality which is why I gave a seperate answer going by the rules.

However, surviving in the upper layers of a Gas Giant's atmosphere is evidently not impossible in reality.

Ask a physicist about waste heat radiation if you want to really ruin your fun.

I am aware of this problem, but I do not think it is relevant to the matter at hand.

Regards,

Tobias

 

[DaveShayne]

Originally posted by Tobias:
However, surviving in the upper layers of a Gas Giant's atmosphere is evidently not impossible in reality.

Considering your only example of survival is a small probe that didn't actually survive I think you are overstating your case somewhat. Give me one example of a craft getting into the atmo and back out with 40 to 50 percent of it's volume filled with liquid hydrogen (I'll settle for 10%) and then you can talk reality.

I am aware of this problem, but I do not think it is relevant to the matter at hand.

Friction (inevitable if you are deep enough into the atmosphere that it's dense enough to get usefull amounts of hydrogen) causes heat - heat has to be radiated. It's directly related to the discusion.

 

[Hemdian]

Sticking to the reality of Traveller (heat dissipation is not a problem, radiation shielding is not a problem, magnetic fields are not a problem, etc) ... the question is: isn't ocean refuelling going to be easier than gas giant skimming?

Regards PLST

 

[Renard Ruche]

Hemdain:

I was chatting with Parmasson about some ship design questions the other day, and his ultimate response was:

'My take after several years of refereeing is that in your universe YOU ARE GOD! If you say that ship goes Jump 4 it goes Jump 4. If you want all hot dogs in your universe to be blue they are. If you want a 20% fudge factor you can take it.'


The rules are there to give you and the players guidelines. If you want the AHL to be able to perform ocean refuelling, then *bang* it's reality. My only advice is, make it pretty dangerous, last ditch type thing...you would only try it if there was no other option. And if the AHL has been through enough to loose it's fuel skimmer, I would assume it's going to be a pretty bumpy right, at the very least!

Of course, the scout version of the AHL may be better prepared for this eventuality.

 

[DaveShayne]

Originally posted by Hemdian:
Sticking to the reality of Traveller (heat dissipation is not a problem, radiation shielding is not a problem, magnetic fields are not a problem, etc) ... the question is: isn't ocean refuelling going to be easier than gas giant skimming?

Regards PLST

Almost certainly. The problem arises in that going by Traveller reality that AHL can't get down to the ocean to refuel. Does this make sense? I don't know but it is the way the rules are written.

 

[Tobias]

Originally posted by DaveShayne:
Considering your only example of survival is a small probe that didn't actually survive I think you are overstating your case somewhat.

Considering that it descended to depths where the pressure was 20+ times higher than on earth (so it was technically well below the "surface" of the planet), measured winds of 500+ kph and was subjected to quite high temperature, I don't think so.

Give me one example of a craft getting into the atmo and back out with 40 to 50 percent of it's volume filled with liquid hydrogen

Considering that no craft has ever attempted to collect hydrogen from a Gas Giant, that is an unreasonable approach. Give me one example of a manned starship experiencing any trouble in a Gas Giant's atmosphere.
But from a theoretical viewpoint: You can collect hydrogen basically everywhere in the universe. There are a few places where you can't, but the stratosphere of a planet which basically consists of hydrogen is one place where you definitely can.
I can only repeat myself: The ship would not need to dive into the Gas Giant itself. Staying in the upper layers of the atmosphere should yield a sufficient density of Hydrogen.

Friction (inevitable if you are deep enough into the atmosphere that it's dense enough to get usefull amounts of hydrogen) causes heat - heat has to be radiated.

Immersion in an atmosphere voids the basic problem at the heart of the radiator dilemma - the lack of conduction.

Regards,

Tobias

 

[DaveShayne]

Originally posted by Tobias:
</font><blockquote>quote:</font><hr />Originally posted by DaveShayne:
Considering your only example of survival is a small probe that didn't actually survive I think you are overstating your case somewhat.

Considering that it descended to depths where the pressure was 20+ times higher than on earth (so it was technically well below the "surface" of the planet), measured winds of 500+ kph and was subjected to quite high temperature, I don't think so.</font>[/QUOTE]And considering that it wasn't trying to suck hydrogen into it's frame through a gaping big hole and didn't try to get back out I do think so.

</font><blockquote>quote:</font><hr />Friction (inevitable if you are deep enough into the atmosphere that it's dense enough to get usefull amounts of hydrogen) causes heat - heat has to be radiated.

Immersion in an atmosphere voids the basic problem at the heart of the radiator dilemma - the lack of conduction.</font>[/QUOTE]But the convective ability of atmosphere probably won't help in this instance. The denser the gas is the greater the heat produced by the friction. Thinner densities mean less convection.

Anyway I stand by my gut feeling of probably not possible.

 

[Tobias]

Originally posted by DaveShayne:
And considering that it wasn't trying to suck hydrogen into it's frame through a gaping big hole and didn't try to get back out I do think so.

I do not think that fuel scoops are quite that primitive. That it didn't try to get back would be relevant only insofar as it received damage during the way down. The stated pressure was when its instruments stopped transmitting data. It is reasonable to assume that during a time when these delicate electronics were still operating, the probe was largely intact.

But the convective ability of atmosphere probably won't help in this instance. The denser the gas is the greater the heat produced by the friction. Thinner densities mean less convection.

That depends on velocity, environment temperature and other factors.
But for aircraft it works - in a different type of atmosphere, of course, but seeing as Gas Giant upper atmospheres are quite cold, it is logical to assume it could work here as well.

Anyway I stand by my gut feeling of probably not possible.

I prefer a more fact-oriented approach. I do not see any reason why a future spaceship with considerable armor, streamlining and structural strengthening should be unable to move through a low-density gas cloud collecting hydrogen when small, disposable drones have managed considerably greater feats.

Regards,

Tobias

 

[DaveShayne]

Originally posted by Tobias:
I prefer a more fact-oriented approach.

I'd like to see a more fact oriented aproach as well. I haven't seen any particularly relevent facts from you however and still think fuel skimming in a real world situation is unlikely because of the many practical dificulties involved.

Obviously YMV.

 

[Tobias]

I'd like to see a more fact oriented aproach as well. I haven't seen any particularly relevent facts from you however

You seemed to ignore the actual content of my posts, then. Let me sum it up in a nutshell:
- Gas Giant atmospheres are layered, just like any other atmosphere. In the outer atmosphere, there is low pressure, low friction, and still enough hydrogen to collect over time.
- Tiny, fragile drones of today can actually survive delving into the gas giant itself.
These are facts. Whether you come to the conclusion that supertech spaceships will be capable of skimming a Gas Giant's stratosphere, which poses only a miniscule fraction of the problems faced by the Galileo-launched probe, is up to you.

Regards,

Tobias