Gas Giant Skimming

[Timerover51]

I have been looking at distances in our Solar System between planets, and got to thinking about the economics of gas giant skimming. The idea is to get free fuel, so that you do not have to buy it at your destination.

However, if your destination planet is on the other side of the star from the gas giant you just skimmed, your destination might be several hundred millions of kilometers away. You are not going to cover that in Jump Space, so you use your maneuver drive and boost to it. That could take anywhere from 3 days to close to a week, depending on your drive. That is time when your ship is not earning anything, but your passengers and crew are still eating and breathing, using up life support stores, and you ship is more exposed to possible dangers. Then, when you reach the planet, you still need to find more cargo and passengers, but instead of two jump that months, you are making only one. That is going to make it a lot harder to make your ship and crew payments for that month.

My question is then, does it really make sense to spend the time trying to save some money skimming a gas giant, when it costs you the revenue from an additional jump?

 

[AnotherDilbert]

No, of course not. You skim from the local planet, or buy fuel.

Remote gas giant skimming is for ships in a hurry that don't want to visit the local main world.

 

[whartung]

The problem with Gas Giants is that they move. They're even a lousy destination if you have a busy outer system filled with belters and whatnot.

They are, however, handy for mid-multi-jump refueling if you don't want to bother hitting up the local refined sources. If you have a Jump 4 route with a J2 drive, target the gas giant in the Jump 2 system, instead of the home port.

One advantage of gas giants is that there's no waiting for a fuel nozzle.

It's also likely to be less heavily defended if you're trying to bounce a raider fleet in to the gooey center of a sub sector.

 

[McPerth]

I have been looking at distances in our Solar System between planets, and got to thinking about the economics of gas giant skimming. The idea is to get free fuel, so that you do not have to buy it at your destination.

However, if your destination planet is on the other side of the star from the gas giant you just skimmed, your destination might be several hundred millions of kilometers away. You are not going to cover that in Jump Space, so you use your maneuver drive and boost to it. That could take anywhere from 3 days to close to a week, depending on your drive. That is time when your ship is not earning anything, but your passengers and crew are still eating and breathing, using up life support stores, and you ship is more exposed to possible dangers. Then, when you reach the planet, you still need to find more cargo and passengers, but instead of two jump that months, you are making only one. That is going to make it a lot harder to make your ship and crew payments for that month.

My question is then, does it really make sense to spend the time trying to save some money skimming a gas giant, when it costs you the revenue from an additional jump?

This depends. Most ship's numbers are thought on 1 jump every 2 weeks. If you spend 1 jump in travel, an day skimming and 3 more to the main planet, you're still in schedule for you jump every 2 weeks, more so if you can contact a local brocker while skimming or moving to sell your cargo and find another, as well as passengers (post your next destination in the worlds' ciber board).

If the trip takes more than 4 days, things begin to get thight...

Not to say when the planet is a gas giant satellite...

The problem with Gas Giants is that they move. They're even a lousy destination if you have a busy outer system filled with belters and whatnot.

Sure, they move, but their movement is predictable well ahead....

It's also likely to be less heavily defended if you're trying to bounce a raider fleet in to the gooey center of a sub sector.

According the usual SDB deployment as told in several canon sources, they use to be the most defended parts of a system, aside from the main planet...

 

[Magnus von Thornwood]

Ooooo.

I had never considered this but good question.

I sorta figured that for the most part only Navies and Scouts hit up the GG, or as noted a ship with no in-system stops. For Merchants I always figured that Fuel costs were just part of the budget under "Expenses" and you gassed up at the Port.

 

[Enoki]

Actually, gas giants are a bad deal to refuel from in most cases. The most obvious reason to want to use one is that you really don't want anybody to know you're in-system and refueling.

First, the 100D distance from a gas giant when you jump in puts you-- usually-- a couple of days from the planet. Even if it's just say 23 hours at 1G to get into orbit, that's a big chunk of time wasted. Then you have the gravity well to consider getting back out of the gas giant to the 100 D jump horizon. That eats lots of time too.

In an expanded system generation, usually you can find water or hydrogen on an asteroid, planetoid, rocky planet, or elsewhere in the outer system. Even the outer satellites of a gas giant are a better choice than the gas giant itself.

If you use the maneuver system in LBB 3 (? I think I've got the right one without looking that up) from classic Traveller, you can see that maneuvering into and away from a gas giant is a big time waster.

 

[aramis]

According the usual SDB deployment as told in several canon sources, they use to be the most defended parts of a system, aside from the main planet...

GG's need to be defended for out-system travel only; most are going to be past Jupiter orbit (roughly orbit 6) - and orbits 7+ are longer to fly in-system than to jump. You aim for the outer GG's to bypass the mainworld.

This means the Navy needs to maintain a lot of SDB tonnage to defend the major worlds from deep attacks...

see, while you can detect ships at your roughly 8 AU of your mainworld, in about and hour, you can't get there in under a week by any means. So, if you detect incoming, you notify EVERY system within courier range; only the SDBs are going to be able to deny the GG, and by the time you know if the SDB's have worked, it's too late to even advise them.

 

[Silverhawk]

I have been looking at distances in our Solar System between planets, and got to thinking about the economics of gas giant skimming. The idea is to get free fuel, so that you do not have to buy it at your destination.

However, if your destination planet is on the other side of the star from the gas giant you just skimmed, your destination might be several hundred millions of kilometers away. You are not going to cover that in Jump Space, so you use your maneuver drive and boost to it. That could take anywhere from 3 days to close to a week, depending on your drive. That is time when your ship is not earning anything, but your passengers and crew are still eating and breathing, using up life support stores, and you ship is more exposed to possible dangers. Then, when you reach the planet, you still need to find more cargo and passengers, but instead of two jump that months, you are making only one. That is going to make it a lot harder to make your ship and crew payments for that month.

My question is then, does it really make sense to spend the time trying to save some money skimming a gas giant, when it costs you the revenue from an additional jump?

If the concern is about the delay for passengers and cargo, why go to refuel first? Unless you need it because there won't be fuel for the Powerplant, head for the mainworld take care of business. Skim on the outbound leg since, as Enoki pointed out you will have flight time to clear the GG's 100 diameter limit. Use that time to process the fuel.
Just an alternative thought.

 

[Carlobrand]

I would characterize gas giant refueling by a merchant as a desperation maneuver: you just don't have the cash to fill the tank, and for one reason or another the closer free fuel sources (water) are not available (the local government will shoot you down).

You can get unrefined fuel for Cr100 per dTon at the starport, but it's almost a 6-day flight for the typical 1G merchant to get to the closest gas giant by canon, and it's likely to be worse if the DM is one of those realism types who tries to figure out if the two worlds are close or far apart at this time of year. The merchant's basically turned a 2-week flight into a 3-week flight. For the Book-2 free trader grossing at best Cr324,000 per month, they've just saved Cr2500 but lost almost a week of potential income out of their year, or worse if they do it regularly. Even if they aren't turning a profit, fuel costs are only about 2 or 3 percent of their expenses if they're buying unrefined fuel at the port; they're better off paying the price and getting to the next potential source of profit as quickly as possible.

Numbers are different for different ships, of course, but it really doesn't get better.

 

[Enoki]

I see gas giant skimming, and using the outer worlds, particularly if sparsely populated, as the province of criminals and those on the edge of society.
You are smuggling "stuff."
You have a known, arranged contact in this system.
They have a ship waiting to transfer the "stuff" to in orbit of the gas giant hiding in its magnetic field, or even inside the atmosphere.
You arrive and transfer the goods getting paid. You refuel off the gas giant and then sneak back out of the system.
The whole time, you keep most or all of your active sensors turned off, and try to make yourself as invisible as possible.

It doesn't matter if it takes an extra week now. You're smuggling goods that have a very high value and that's just part of the cost of doing business.

 

[whartung]

GG's need to be defended for out-system travel only; most are going to be past Jupiter orbit (roughly orbit 6) - and orbits 7+ are longer to fly in-system than to jump. You aim for the outer GG's to bypass the mainworld.

This means the Navy needs to maintain a lot of SDB tonnage to defend the major worlds from deep attacks...

I find it difficult to imagine an SDB flotilla having any real affect against a determined raiding fleet with real tonnage.

Then you have to consider a system like ours: 4 Gas Giants. Each one needs to have a force capable of deterring an attacker. Plus the forces at the home world(s).

If you look at a game like FFW, there shouldn't be a stack of counters in each hex, but there should be one for each defensible point. (i.e. gas giants). You may well have to choose whether to let a penetration raid through or sacrifice defenses on the real infrastructure within the system. Of course I appreciate the simplicity of the FFW system, but I think it shadows the real problems faced by planners.

Simply, I think that the border areas are much more porous than one might think. To where all you can do is see an enemy fleet jump in, count the bright dots on the screen, and then jump out, fueled and ready to go before you can get a reaction force there in to confront them.

 

[Enoki]

I find it difficult to imagine an SDB flotilla having any real affect against a determined raiding fleet with real tonnage.

Then you have to consider a system like ours: 4 Gas Giants. Each one needs to have a force capable of deterring an attacker. Plus the forces at the home world(s).

If you look at a game like FFW, there shouldn't be a stack of counters in each hex, but there should be one for each defensible point. (i.e. gas giants). You may well have to choose whether to let a penetration raid through or sacrifice defenses on the real infrastructure within the system. Of course I appreciate the simplicity of the FFW system, but I think it shadows the real problems faced by planners.

Simply, I think that the border areas are much more porous than one might think. To where all you can do is see an enemy fleet jump in, count the bright dots on the screen, and then jump out, fueled and ready to go before you can get a reaction force there in to confront them.

The SBD's would be best used within the actual gas giants where they engage in hit and run attacks against enemy ships in the atmosphere rather than in space. The objective would be to disrupt fueling and cause some degree of damage to the ships engaged in it.
An SBD set up to do that versus a ship designed primarily for space combat would put the SBD at an advantage over the starship. The SBD might have aerodynamic surfaces to increase maneuverability in an atmosphere, be equipped with weapons optimized for use in an atmosphere, and be better armored to allow going deeper into the gas giant to evade retaliation.

If the SBD's stayed in the atmosphere or only ventured out into space near the gas giant, they'd have the advantage of cover. Beam and energy weapons would be at a severe disadvantage against them. All they have to do is delay or disrupt the enemy, not destroy them.

This could seriously disrupt a fleet's refueling process.

 

[whartung]

All they have to do is delay or disrupt the enemy, not destroy them.

Since wilderness refueling behind enemy lines is mission requirement, you'd like to think that the fleet is prepared to deal with the specifics of beating of SDBs occluded in the atmosphere.

The attacking fleet is not going to "delay". You have to appreciate that they're not going to wait. There's nothing to wait for. The longer they stay, the more dangerous it becomes. No help is coming, and I doubt the SDB crews are going to get bored. The attackers really have nowhere to go, and are backed in to a corner the moment they arrive. They're dead already, and motivated to fight it out.

So, they will start refueling and destroy anything that gets in their way. If they take damage, then, hey, C'est la guerre. They knew this going in to it. No doubt the planners took it in to consideration when they planned the raid.

The only surprise is if the SDB forces awaiting the fleet are notably larger than whatever intelligence was reporting to be expected.

Even with any potential advantage of being in the atmosphere, I do not believe that SDBs can dramatically outfight their weight beyond the advantage of extra tonnage in lieu of a jump drive (assuming they are, indeed, just space ships vs star ships). The atmosphere works both ways, and will disadvantage both parties (though it may affect the attacker more than the SDB). The worst case is SDB blindly salvoing missiles out of the atmosphere to autonomously seek orbital targets once clear of the interference. You also have the case that when the refueling ship may simply bury itself in the atmosphere while refueling, offering it the same defensive advantages the SDB have. They simply have to survive the interface portions going in and going out.

And it does not discount the spreading of forces necessary to cover the different gas giants for systems with more than one. Theses defenses are very expensive. It can easily be decided that they are not worth defending, vs investing the defense on actual targets and infrastructure.

 

[aramis]

I find it difficult to imagine an SDB flotilla having any real affect against a determined raiding fleet with real tonnage.

Then you have to consider a system like ours: 4 Gas Giants. Each one needs to have a force capable of deterring an attacker. Plus the forces at the home world(s).

If you look at a game like FFW, there shouldn't be a stack of counters in each hex, but there should be one for each defensible point. (i.e. gas giants). You may well have to choose whether to let a penetration raid through or sacrifice defenses on the real infrastructure within the system. Of course I appreciate the simplicity of the FFW system, but I think it shadows the real problems faced by planners.

Simply, I think that the border areas are much more porous than one might think. To where all you can do is see an enemy fleet jump in, count the bright dots on the screen, and then jump out, fueled and ready to go before you can get a reaction force there in to confront them.

Refuelling craft are undergoing some of the peak incident stress of their operational life (Sup 5 notes this); a nuclear missile barrage in atmosphere is much more damaging than in vacuum.

Any engine hit is likely to result in a terminal event for the ship on the pass-through; you won't have the thrust needed to exit. Welcome to crush depth.

Crack the hull? anywhere from a minor issue to a catastrophic failure, depending upon exactly where. Anywhere on the front while inbound or in the deep third and it should result in catastrophic failure of the hull.

Unfortunately, these are issues outside the scope of the combat systems presented in the game.

On the other hand, the crew damage isn't outside the scope. And nukes are a way to do a lot of crew damage.

No fuel? No jump. Using Jump Shuttles? You likely won't have the defenses on the shuttles to fend off a 1000 Td hulled Missile-bay SDB loaded with Nukes.

The SDB itself will be max armor, Nuke dampers, and a 100 Td missile bay, and max G's for TL. Lots of Ammo, too. Most will be bigger than 1000 Td, so as to mount additional weapons - defense lasers. A 2000 Td hull has a large laser array for defensive fire, and a 100 Td nuclear missile bay..

 

[Enoki]

Aside from that... If you have to plan for and defend against SBD's then you are dumping cubic credits into doing that at the expense of building more space warfare ships, or making your space warfare ships less capable.

Any polity, nation, planetary government, has a limited budget. They simply cannot build endless ships and crew them. So, having to deal with SBD's as an expected part of gas giant refueling in a hostile system adds another layer of difficulty to the process.

 

[whartung]

Refuelling craft are undergoing some of the peak incident stress of their operational life (Sup 5 notes this); a nuclear missile barrage in atmosphere is much more damaging than in vacuum.

But all of this applies to the SDBs as well unless they're flying in blind out of the Sun, if not moreso since they're even deeper in the atmosphere.

As bad as lasers might be in the atmosphere, they're still efficacious at the throat cutting ranges of interface combat. They're still faster than anything else. You have sensors and systems designed to do deep space combat with ranges in the 100,000kms, waging battle in hundreds of km, far outside the effective range of a nuclear blast, well inside the "if we can see it, we can kill it" accuracy of a laser defense battery. none of this "multiple laser pulses over thousands of kilometers hoping for a hit", we're talking millisecond travel times.

As a corollary, with the efficacy of nuclear weapons in atmosphere, the basic "cheap" nature of nuclear missiles, and the even more "close only counts for horseshoes, hang grenades, and atom bombs", the attacking fleet will probably nuke any suspicious sensor ghost crawling under the clouds.

If the skimming ship were attacked blind from above, yea, I get it. (And thus the whole "high guard" concept.)

But I think the submerged ships are in even worse shape, deeper in the gravity well, easy enough to spot, and cheap enough to irradiate Just In Case.

 

[Enoki]

I'd say the reverse is true. The ship deeper in the planet will be masked by atmosphere. If there are strong magnetic fields, electrical storms, and particulates in the atmosphere (eg., the gas giant is like Jupiter) it's going to make finding anything deep in the atmosphere difficult.
Then you throw in violent winds, temperature gradients, atmospheric stratification, and you have all the makings for finding anything deep in the planet's atmosphere difficult to do.

Stuff out in space would be simple to detect by comparison. There's nowhere to hide.

For example, this stuff isn't in the rules, but would be entirely possible:

The SDB has a "towed array" of sensors that floats up higher in the atmosphere to find targets without revealing its own position. It's towed because by linking the ship and array using a cable, the interference of the gas giant's atmosphere, magnetosphere, etc., doesn't effect it.

It uses longer ranged, atmospherically flight capable "cruise" missiles that can be launched from hundreds or even thousands of kilometers against the target. These are programmed to "pop up" out of the deeper atmosphere at relatively short range and using nuclear warheads would attack the refueling ship.

Another nastiness would be for the defenders to have put a few massive meson spinal mounts on satellites around the gas giant and do everything to camouflage these to be as undetectable as possible until they open up. Deep in a satellite's core, these wait until the enemy ships start refueling then fire on them.


Even adding more asteroid sized bodies into close orbits of the gas giant should be possible. Lots of rocks racing around it will complicate navigation and maneuver in and out of the gas giant. I doubt getting hit by 10,000 tons of rock at thousands of KM a minute would be good for any ship.

 

[aramis]

But all of this applies to the SDBs as well unless they're flying in blind out of the Sun, if not moreso since they're even deeper in the atmosphere.

SDB''s are purpose built and designed specifically for resisting the pressure.

A design intended primarily for damage resistance versus one for pressure resistance isn't going to be identical. SDB's are designed to withstand crush depths comparable to nuclear subs.

There should be a penalty for this pressure resistence. None has been provided.

Looking up the Ohio Class, ~500m depth, ~50 Bar, and ~38mm thick TL8 steel. Which, per Striker & MT is right at MT AV 14. (ship hulls are minimum AV 40). Which isn't even HG Rating 1 (= MTAV 40).

More modern designs have test depths ~600 m and similar thickness of better alloys. So, lets assume 50/14 3.5 Bar per AV. HG Ar at 7 is MT Av 57, +1 HG = +1 Striker/MT AV; SDB's should be TL and HG Armor 10+ ; they need gravitic thrust. Given that the thickness appears to be a log-scale straight-line (thus an exponential curve), and Striker/MT armor also is... this should work fine.

So a TL 12 HG vessel should have HG AV 12 (= MT AV 62)... for some 217 Bar tolerable... On Earth, that's some 2 km below wavetops. On Jupiter, I'm not certain, but the cloud tops are 1 Bar; 90 km down is 10 bar. Assuming 10 bar per 90 km continues... 90*217/10, we get more than 1900 km deep.

Assuming drone sensors and deep strike missile bays, the boats themselves may be and remain almost invisible, while peppering scooping vessels in the high cloud regions with nukes. With smart sensors, the nukes can even aim to go off just above, and force the course down...

 

[Carlobrand]

... with the efficacy of nuclear weapons in atmosphere, the basic "cheap" nature of nuclear missiles, and the even more "close only counts for horseshoes, hang grenades, and atom bombs", the attacking fleet will probably nuke any suspicious sensor ghost crawling under the clouds. ...

Pretty much, as laid out in the FFW box game. Attacking fleet rolls a D6, takes a negative DM equal to half the system's tech level, takes an additional -3 DM when the SDBs are hiding, and then consults a table. That's a rather unforgiving table. Most systems that do have SDBs only have a few and aren't particularly high tech, so SDBs in those systems get nuked pretty quick. You tend to want to send them out and hope they can do a bit of damage before they burn up.

There's no model for a High Guard style combat against SDBs hiding in a gas giant. SDBs per Secret of the Ancients can tolerate pressures up to 3000 atmospheres, between 4000 and 5000 kilometers below the top of the atmosphere and a few hundred kilometers below what other warships can handle. That could be deeper than missiles can manage: building a missile that can equalize pressure in all components with the external environment (to avoid being crushed) while going from zero to three thousand or so atmospheres propelling itself for much of the way through basically liquid hydrogen, at temperatures that would melt steel, for a couple thousand miles or so could be quite challenging. The warhead's a pit surrounded by an explosive charge; I don't know if you could design it and its electronics to handle that kind of environment. I think you're looking at deadfall ordnance you set off in the upper atmosphere, hoping the propagating shock wave is enough to kill them.

 

[Silverhawk]

Another nastiness would be for the defenders to have put a few massive meson spinal mounts on satellites around the gas giant and do everything to camouflage these to be as undetectable as possible until they open up. Deep in a satellite's core, these wait until the enemy ships start refueling then fire on them.


Even adding more asteroid sized bodies into close orbits of the gas giant should be possible. Lots of rocks racing around it will complicate navigation and maneuver in and out of the gas giant. I doubt getting hit by 10,000 tons of rock at thousands of KM a minute would be good for any ship.

For those systems that can't afford Meson weapons the option might be to add missile bays to those small rocks as well. Committed to a scoop run seems to me to reduce the options for evasive maneuvers. So if there are enough to overwhelm the defense there will be damage inflicted.