On fuel, skimming GGs, and 1G drives...

[Foxroe]

I was perusing this thread today (and what a great thread BTW)…

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=11071&page=1

…and I had a couple of ideas:

Skimming GG’s

I always interpreted the 8-hour operation to mean that the ship settled into the lowest possible orbit around the GG, where there existed a very small concentration of hydrogen gas. The ship spends 8 hours in this relatively safe orbit sucking up the raw fuel it needs, then accelerates out of orbit once the tanks are full. This seems much more tame than the suggested repetitive “dive-bombing” of the upper atmosphere.

1G Maneuver Drives on Size 9+ Worlds

The whole vector math thing makes sense to me, and there is certainly no denying that the CT rules explicitly state that a low-G ship cannot take-off from a high-G world. However, the use of lift in atmosphere to offset the gravity vector enough to allow a slow departure would definitely work. The issue is getting the initial velocity necessary to generate that lift. MT talks about built-in overdrive to satisfy this, CT does not. Why not take the middle ground? The CT ruling is that it can’t happen, but that doesn’t mean that the pilot can’t attempt it! While the drives aren’t designed for it, they might be able to be goaded into achieving orbit, so make it a skill task to “overdrive” them:

“To overdrive the ship’s under-rated maneuvering drive in an attempt to achieve escape velocity from a high-G world, throw 13+ on 2D. DM’s are Pilot skill level or Engineering skill level (whichever is higher), -1 if Atmosphere 3 or less,-1 if using unrefined fuel (couldn’t resist putting that one in there), and -1 per missing required engineer. Failure indicates that the maneuvering drive has malfunctioned, and the ship crash-lands. Roll 1D hits on the Starship Hit Location table.”… or something like that.

LBB2/TTB fuel purification

While it doesn’t explicitly state this that I’m aware of, I always assumed that the standard designs presented in Book 2 were built without the ability to refine fuel. However, there should be nothing stopping the GM/Players from designing a different vessel than those presented that could use unrefined fuel at no penalty. That being said, I would rule that the option couldn’t be retrofitted to an existing ship. As far as why these designs have no purification ability, I would guess that Supp4 touched on it at the end of the thread: “Big Fuel” megacorporations have managed to force the issue (or at least that’s the popular conspiracy theory)… or perhaps it is just a TL issue. While it is certainly possible that fuel can be refined at lower tech levels, maybe it isn’t practical (cost/size-wise) for LBB2-sized ships until a higher TL (Note: don’t have HG handy to see the worst case TL/mass for a plant right now… so this suggestion may be lame).

-Fox

 

[Foxroe]

All right, so I read the section in TTB about skimming, and it does mention "diving deep into the atmosphere" after achieving orbit, but that still strikes me as suicidal. I certainly can't speak for systems outside our own, but I'm thinking that the atmosphere around Jupiter/Saturn would tear anything to shreds. And from what I've read, astronomers believe that the gas giants thus far detected around other stars are even worse. It always bugged me that a standard system defense boat tactic is lying in wait within a gas giant's clouds, ready to pounce on refueling enemy forces... they'd be tribble-chum!

-Fox

 

[Renaissance Man]

I'd expect that dive bombing into a GG atmosphere would be a one-way trip for most small craft and ships with smaller M-drives. Especially at earlier TL's we just could not expect ships to be dropping into the atmosphere and out again - they wouldn't have the juice.

I like the idea of using momentum and a specific approach vector to skim the upper edges of the atmosphere and break away (as per the gravitational "slingshot" technique,) circle around and do it again. I could see that as an 8-hour operation, and relatively safe.

Of course, the hull would get extremely hot. Some artful use of a ship's M-drive or contragrav could shunt particles away from leading edges of the hull and toward the fuel scoops to minimize heat-stress. Maybe this, in combination with a some kind of hull magnetization is able to manage high-velocity atmospheric particles.

I've always thought that management of hot reentry would have been a top priority for any spacefaring culture since it is the single most wear-inducing function of a ship besides combat. Especially if your ship is expected to dive into GG atmosphere's regularly.

 

[Foxroe]

I've always thought that management of hot reentry would have been a top priority for any spacefaring culture since it is the single most wear-inducing function of a ship besides combat. Especially if your ship is expected to dive into GG atmosphere's regularly.

Good point. But would the forces involved with diving into a GG's atmosphere be comparable to those during re-entry into an Earth-like atmosphere?

-Fox

 

[Renaissance Man]

Good point. But would the forces involved with diving into a GG's atmosphere be comparable to those during re-entry into an Earth-like atmosphere?

I should think so. I'm no physicist, but I figure the higher mass of GGs means the atmosphere is denser. And a bigger size means a bigger radius from the centre of rotation and therefore a greater speed of rotation. Add to that the violent wind speeds and you have more particle collisions at higher speeds. Mass of the particles will be less (hydrogen and helium vs. nitrogen and oxygen), but I expect these factors will at the least even out, if not make GG forces worse.

 

[Icosahedron]

AIUI, most of the hull heating during reentry is due to frictional deceleration from orbital speed. The gravity at Jupiter's cloud tops is about 2.5 G, so a 3G ship could just sit n dip without too much worry. Probably only need 2G on a SGG.
Wouldn't help a 1G ship much, though.

 

[jfetters]

Maybe we can settle some of this from the info from Adventure 12:

Since a key moment of the adventure takes place literally within the gas giant itself, there are some comments within:

Most ships refuelling from a gas giant rarely venture below the level of 0.5 atmospheres ... In order for a ship to enter the atmosphere, stop, hover, and otherwise maneuver, it must have at least 3G maneuver drive.

So that infers that 0.5 atmospheres is the max that most ships will go that do not have a 3G M-drive or greater. But what is the outermost level?

 

[Hal]

A while back I took the time to create create a "fictional company" for use in my own Campaign set in the Lunion Subsector. The company was called "The Ianic Refueling Corporation" whose purpose was to shave off the week required for ships to refuel at the only gas giant in the star system. The ship designes included:

145-ton Fuel Skimmer. Class: Plecostomus (robotic)
400-ton Oiler. Class: Jovian Diver
350-ton Refinery Station. Class: The Station

I had also spent the time detailing the costs for underground storage tanks, pumps, along with fuel trucks to service the starships at the starport. I calculated various things such as how much time was needed for down time for boats that could not jump between systems, but could have their annual maintenance done on the planetary surface. Five ships were needed to service the demand as well as handle the needs for individual maintenance. In addition, I took the time to consider what the other costs were and then calculated the return on investment based on the expected sales versus the expected costs.

What I found to be interesting is that, for Ianic Refueling Corporation, they could not maintain a profit if they sold unrefined fuel, but had to sell refined fuel to make their profit at all, let alone stay solvent. In addition - for those who wonder...

The ruleset I was using specified that on worlds with a Hydrographic value of 4 or less, wilderness refueling was outlawed. Ianic is a desert world, and as such, had in fact, outlawed wilderness refueling, and water was not permitted to be used for fuel by law.

In any event, unless the world has sufficient resources on world for providing raw unrefined fuel cheaply, the only way any planetary company can exist while selling fuel is to sel refined fuel - the costs of transporting unrefined fuel is just too high.

 

[atpollard]

What I found to be interesting is that, for Ianic Refueling Corporation, they could not maintain a profit if they sold unrefined fuel, but had to sell refined fuel to make their profit at all, let alone stay solvent. In addition - for those who wonder...

I would be interested in seeing your numbers. My old 'quick and dirty' calculations showed it to be VERY profitable.

 

[Qstor2]

This is a good article on Gas Giants and skimming from freelancetraveller (dot) com

http://www.freelancetraveller.com/features/science/gasgiants.html

Mike

 

[Foxroe]

This is a good article on Gas Giants and skimming from freelancetraveller (dot) com

http://www.freelancetraveller.com/features/science/gasgiants.html

Mike

Awesome article! Full of great stuff; I especially like the descriptions from a skimming ship's POV. :devil:

So when interpreting the LBB3 results for a GG, I would say that it doesn't necessarily mean that these are the only systems with GG's, but that these are the only systems with usable GG's (i.e. calm/low-contamination).

Thanks Mike!

-Fox

 

[Hal]

I would be interested in seeing your numbers. My old 'quick and dirty' calculations showed it to be VERY profitable.

What I would have to do is try and find out where the old TML archives are being kept, because I thought I had posted it to the TML and now can't find it. I still have the figures I used from GURPS FAR TRADER in estimating traffic patterns of commerce between Ianic and other worlds (this before the author suggested changing a value of the equation but not making it an official errata). If you're interested in the numbers I used for the traffic patterns, feel free to email me and I'll try and rework the figures. Note that I was using GURPS TRAVELLER prices and rules in the calculations. What might be "interesting" is to use JUST the GURPS traffic values that I used, and then working with only CT hull costs etc.

Books I used for the construction of the Ianic Refueling corporation:

GURPS TRAVELLER
GURPS STARSHIPS
GURPS STARPORTS
GURPS FAR TRADER

All of those books combined detailed costs for underground fuel depots, fuel pumper/tanker vehicles (ie grav tankers), ship costs, maintenance rules, etc. If I can't find the archives from the TML, then perhaps I can rebuild it. I still have the ship designs to work off of, so it shouldn't be THAT hard to redo - just time consuming Again, email me if you want to pursue this further. My email addy is available from CT-Starshps mailing list if you don't have it here...

Hal

 

[Renaissance Man]

AIUI, most of the hull heating during reentry is due to frictional deceleration from orbital speed. The gravity at Jupiter's cloud tops is about 2.5 G, so a 3G ship could just sit n dip without too much worry. Probably only need 2G on a SGG.
Wouldn't help a 1G ship much, though.

So that basically means that the minimum M-drive of any interstellar vessel, particularly in the early years of space exploration (when fuel is difficult to find) has got to be 2 or ever 3gs. That's some mighty large HePlaR drives. Either that or they have to hope that there's a GG that has 100 T masses or less.

And any ship that has M-drives smaller than that had better not bother to mount fuel scoops unless they're hell bent on wilderness refueling.

 

[atpollard]

So that basically means that the minimum M-drive of any interstellar vessel, particularly in the early years of space exploration (when fuel is difficult to find) has got to be 2 or ever 3gs. That's some mighty large HePlaR drives. Either that or they have to hope that there's a GG that has 100 T masses or less.

And any ship that has M-drives smaller than that had better not bother to mount fuel scoops unless they're hell bent on wilderness refueling.

Unless I am missing something, it should be possible to skim fuel with less than 1G aceleration. Build velocity, use an eccentric orbit and make repeated passes through the atmosphere -where the air drag will slow you down and fill your tanks. The thrust will determine how much drag you can offset, which will determine how deep you can go, which will determine how many passes are needed and long it will take to refuel. It might take longer than 8 hours, but it should be possible.

 

[jrmapes]

What I would have to do is try and find out where the old TML archives are being kept, because I thought I had posted it to the TML and now can't find it.

Do you recall about when (date) you posted it and by chance maybe a message title?

I have the archive on my hard drive and can search it.

You can also find archives here,

July 07 to Current - http://lists.travellercentral.com/pipermail/tml/

1987 to 2002 here - http://dbdev2.pharmacy.arizona.edu/archives/TML_Archives/


Jerry

 

[Hal]

Do you recall about when (date) you posted it and by chance maybe a message title?

I have the archive on my hard drive and can search it.

You can also find archives here,

July 07 to Current - http://lists.travellercentral.com/pipermail/tml/

1987 to 2002 here - http://dbdev2.pharmacy.arizona.edu/archives/TML_Archives/


Jerry

Hi Jerry,
Best as I can figure, 12/2003 or so - give a month or two either way.

Hal

 

[Renaissance Man]

The thrust will determine how much drag you can offset, which will determine how deep you can go, which will determine how many passes are needed and long it will take to refuel. It might take longer than 8 hours, but it should be possible.

I don't know man, from the article in Freelance Traveller, it sounds like you sort of have to dip in below the top layer of clouds in order to get to the "calm layer". Even when you're in the so-called "calm layer" you have to pick your point of entry carefully and hope that you don't hit a stormfront. That means that you'll have to get escape velocity in order to get back out.

 

[jrmapes]

Hi Jerry,
Best as I can figure, 12/2003 or so - give a month or two either way.

Hal

Crud. Unfortunately that range of time falls into the TML Black Hole.

The TML switched hosts a couple times in that period so those archives are spotty. I don't have copies of the archive or the digests from 2002 to 2006 - same with most of us that kept archives. I believe Listmom and maybe one other person has much of the 2003 to 2005 (some from 2006) archives in Unix mbox format but none of it is available to the community at this time.

There is a project going on to get all the archives in one spot and make it searchable - which will be nice when it gets finished. But until that time, from '03 to '06 will remain a black hole to anyone trying to find anything from the TML during that time.

Jerry

 

[atpollard]

I don't know man, from the article in Freelance Traveller, it sounds like you sort of have to dip in below the top layer of clouds in order to get to the "calm layer". Even when you're in the so-called "calm layer" you have to pick your point of entry carefully and hope that you don't hit a stormfront. That means that you'll have to get escape velocity in order to get back out.

There is a LOT of speculation about HOW to gather H2 in that article. If the assumptions are correct, then the conclusions are probably correct. On the other hand, if H2 can be skimmed from the thin atmosphere at the edge of space around the GG, then the winds and storms are irrelevant.

What I was looking at is that I can accelerate towards the GG in a 1 G ship for 8 hours at 5 meters per second (mps) [about half a G] and hit the atmosphere at 144,000 mps which is escape velocity for a world of about 14,000 Gees [assuming no math errors, but either way, you get the basic idea].

I do NOT recommend this tactic, I was simply pointing out that you can build velocity slowly to enter and leave an atmosphere even if the ship could not hover at local gravity.

 

[Hal]

Hi Guys,
Don't feel too bad if you can't find the posts from the TML, as it isn't all THAT important. I found one "post" I made to another forum that gives me most of what I need to recalculate things if neccessary. For now, it appears that apollard is about the only individual interested in what I did, so emailing him privately is sufficient for what he'd like

Part of me is tempted to start a new thread and detail my Ianic Refueling corporation here, and part of me thinks that the Ianic Refueling corporation is unique for my universe and unlikely to ever be needed or found useful by other GM's. To that extent, I'm hesitant to start a new thread. Rather than continue to hijack this thread (I apologize for that), I'm going to let this drop here with a thanks to anyone who would have or did try to dig up my old posts regarding the Ianica Refueling Corp from TML. Thanks Jerry! Thanks apollard!

For those who'd rather I did recreate the details on what went into the Ianic Refueling Corporation, and perhaps explore what the CT version of it might have looked like, feel free to start a thread along the lines of "Exploring Refueling corps in CT" or some such name

Hal