[Space] Steampunk Firefly Idea
 

OK, so this idea is biting me again. The setting in a nut shell is K2 star with a gas giant at 0.62 AU with 3 habitable moons, all three moons will be about half the diameter of Earth, so quite small.

TL is 6 for the most part but with TL7 spaceflight allowing humanity to colonize the other two moons. Most notable that most places reserve the use of petroleum for use in space flight, good for preserving that Steampunk feel.

For Great Powers I'm thinking of stand-ins for the British Empire, France (Republic?) and Germany along with near great powers of USA, Spain and maybe Portugal representing Western, would there be others but? I'm thinking Japan is possible, but any suggestions?

Most actual conflict at this point is fighting over colonies, so limited to relatively small infantry based affairs with light vehicles and limited air ability, there are no space based weapons.

Other then a map and a plot is there anything a setting like this needs?

There's also another habitable planet at 0.39 AU and 3 other stars if I need to expand things.

Re: [Space]Steampunk Firefly Idea
 

Where does the Firefly aspect come into play?

Re: [Space]Steampunk Firefly Idea
 

China for the East. China has always pretty much dominated the Far East, long before Japan became a power. WWII was the height of Japan's domination, and even then they only barely managed to hold China's northern holdings. TL6 was the Boxer Rebellion, with grass-roots rebellion against Western imperialism and Christian missionaries, and who can forget the mythical "my Shaolin Kung Fu training will protect me from bullets!" train of thought that popped up in popular culture.

Re: [Space]Steampunk Firefly Idea
 

More importantly, if we're doing some variation on Firefly here, Chinese stuff is everywhere in the series (except the ethnicities of the main cast), while Japanese stuff is nowhere to be seen.

If this is supposed to be steampunkish, I'd personally dispense with TL7 trappings entirely, use some kind of TL 6+2 handwavium to achieve escape velocity, and then just use steam-based propulsion for maneuvering in vacuum. Whichever PC is the "Big Guy" can have the official job title of Coal Shoveler on a spaceship.

Re: [Space]Steampunk Firefly Idea
 

Agree. GURPS Steampunk also mentions space travel in the form of ether/reactionless drives.

Re: [Space]Steampunk Firefly Idea
 

Don't forget Russia! Armored Bears!

Re: [Space]Steampunk Firefly Idea
 

The comparison to Firefly is more to do with the nature of the 'Verse then anything. As for China, they weren't a Great Power

Re: [Space]Steampunk Firefly Idea
 

Also, the apes of TL7 space travel is the Saturn 5 rocket. That's just 3 men and a minimal amount of supplies. hardly colonization stuff.

Lower gravity on the world launching the thing will only go so far. That probably has less effect on the Delta-V required than you might hope for.

One the other end, a breathable atmosphere and higher than lunar gravity does seriously mess with the design of what you're replacing the Lunar module with.

I'd say almost be definition technology that enabled colonization in this scenario would have to be TL9 if there's no superscience involved.

So you want superscience. The Skylark of Space is probably the most accessible source of in-period technobabble but there were other stories of Emergent Superscience from the TL6. Verne might just miss the right dates but H.G. Wells is in the first third of it. Edgar Rice Burroughs was just a little later.

Re: [Space]Steampunk Firefly Idea
 

I've built surface to orbit spaceplane, 23.2 tons cargo, 64.5 tons Hydrogran-Oxygen fuel, $51,600 to refuel, interface rates of $2,224.137931 per ton, or under $1.20 per pound, or $2.40 after putting in a generous allowance for other costs, very cheap. Trans-Lunar shipping costs are probably about the same, so a shipper being charged $5 per pound and charging $10 per pound is probably the prices for moving goods

Re: [Space]Steampunk Firefly Idea
 

Really? I'm surprised at this. It's been my impression that if, e.g., Earth's gravity had been just 5% lower, getting up into orbit would have been much easier. Still requiring a 3-stage rocket, probably, but much cheaper, and with much less of having to stretch TL7 engineering to its absolute limits.

Re: [Space]Steampunk Firefly Idea
 

Following the formula, escape velocity goes with the square root of the gravity "g", so halving the gravity would give 0.7 of the escape velocity. Note though that distance from the centre of mass "r" is also a factor, so a smaller moon would have a lower escape velocity than just the difference in gravity would indicate.

Re: [Space]Steampunk Firefly Idea
 

How do the astronauts get _back_ from the new moon they visit?. There is very unlikely to be a long, smooth runway for any spaceplane you brought up in pieces and attached to a trans-lunar tug.

So no safe landing an no take-off afterwards.

Re: [Space]Steampunk Firefly Idea
 

Swap out one of the cargo holds for a soft landing system? But the point I'm aiming for will probably be 50 years AFTER the establishment of the first trans-lunar colony, making it a moot issue for the most part

Re: [Space]Steampunk Firefly Idea
 

But that can be quite a significant drop in difficulty, because delta-V goes as the log of the mass ratio. For example if the gravity of the Earth were 0.9 g, the mass ratio for a near ideal kerosene burning rocket falls from 12.2 to 9.5, you maybe *could* cut a stage. If it were 0.7 g, it falls to 5.8 and single stage to orbit starts to look plausible.

Re: [Space]Steampunk Firefly Idea
 

<shrug> Okay, we won't look at the rocket engineer behind the curtain. I just wanted to point out that you didn't really have viable colonization ability at a hard science TL7.

Re: [Space]Steampunk Firefly Idea
 

I don't know how far you've progressed with history or anything, but this is what I might do with the idea.

I'd have conjunctions, perhaps with the help of an uninhabitable intermediary moon, that make transfer between the inhabited moon and one of the other moons easier, but only occurring every few decades. This allows for the occasional wave of lower tech colonisation events to have happened in the past, by the setting's mad scientists, religious cults, or now-defunct superpowers (think of Portugal today).

The setting's modern tech allows freer transport between the worlds and so they are just coming to grips with the secret settlements and power bases that were established decades or even centuries ago.

Re: [Space]Steampunk Firefly Idea
 

So what we need is an enormous cheese-slicer to slim down Mother Earth.

Re: [Space]Steampunk Firefly Idea
 

What exactly is the problem as you see it then?

Re: [Space]Steampunk Firefly Idea
 

Somehow the phrase "hard science TL7" got into a thread titled "Steampunk Firefly".

Re: [Space]Steampunk Firefly Idea
 

Both Steampunk and Firefly are pretty hard sci-fi

Re: [Space]Steampunk Firefly Idea
 

Compared to Star Wars and Star Trek, maybe.

Re: [Space]Steampunk Firefly Idea
 

Apart from sentient machines I don't think Steampunk ever goes beyond what probable

Re: [Space]Steampunk Firefly Idea
 

Steampunk covers a lot of ground from fully realistic alternate history to the more fantastical and everything in between. Cyberpunk, for example, was never realistic.

I tend to think of slightly soft-ish Steampunk as the Murdoch Mysteries aka The Artful Detective show from Canada. Most of the anachronistic tech is at least technically possible.

Re: [Space]Steampunk Firefly Idea
 

TL7 space flight technology culminates in the Saturn 5. The Shuttle was designed at TL7 but didn't fly until tL8 and was continually modified at TL8. Neither of them (or anything real at TL7) would allow you to colonize even out Moon (and even if it had a breathable atmosphere).

Also for your early missions you need a VTOL launch and land that can alnd with a full fuel load or somehow make its' own fuel with a Spaceships Refinery module. That's not tL7 (or even 8) either.

This was why I recommended superscience. Steampunk tends to be full of the stuff starting with the power plant of captain Nemo's Nautilus.

Re: [Space]Steampunk Firefly Idea
 

I tend to think of Steampunk, in this context, to mean internal feel rather than truly Victorian level technology and culture.

Though even TL 7 is quite more advanced than the Victorian age. So why not go back a bit to TL 5/6 and add a hint of superscience?

Re: [Space]Steampunk Firefly Idea
 

Would a more conventional but reusable lift vehicle suit you better? (There's some interesting overlap between the complexities that requires and Steampunk) And I figure that the first wave of colonists would be dropped off in 30 Ton Drop Cans, not reusable spacecraft, they'd have the equipment to build a small spaceport for later use but.

Re: [Space]Steampunk Firefly Idea
 

Well, you only need 1 man and 1 woman to start a colony. Apollo sent 24 people to lunar orbit in a span of 4 years, for exploration and political gain, so this setting could maybe up that by an order of magnitude for colonisation purposes, multiplied by the number of countries involved in the space race.

And there's no reason a return flight has to be necessary, which makes it easier than Apollo was. Furthermore, as the moons have atmospheres, landing is just a matter of deploying parachutes, which saves on the delta-V needed. If refuelling is necessary, using local fuel sources might be sufficient depending on the tech. I'm guessing these habitable moons may have trees, crops, coal and oil available.

Another thing to consider is 3 moons around a gas giant is a different set of orbital mechanics than Earth-Moon. First is escaping your moon's gravity, but that puts you in the gas giant's orbit at a certain orbital speed. Transferring to the orbit of another moon is then a matter of gaining or losing orbital velocity, as well as transferring to its orbital plane. I tried to look at moving from Io to Europa as a comparison, but the outer moon has a slower orbital speed so I'm not sure what that means. The difference is about 3 km/s though, compared to Apollo's delta-V budget of 16 km/s, so my feeling is that it's easier in this setting to get around than looking at what the Saturn V could do. Transfers might also be assisted with slingshots from intermediate moons, making interlunar travel even more efficient. A concerted colonisation drive might also set up a low-orbit slingshot tether launcher, similar to what Stephenson describes in Seveneves.

So, I don't see big problems with colonisation in this setting at TL 7 or so, especially with a few dabs of steampunk superscience.

Re: [Space]Steampunk Firefly Idea
 

Multiple moons offer the possibility of using very low energy transfer orbits to get around -- on the order of hundreds of meters per second delta-V, rather than multiple kilometers per second. See, e.g., Ross and Scheeres 2007.

Re: [Space]Steampunk Firefly Idea
 

Indeed, and I'm sure most NASA probe missions are done on a fairly low delta-V budget.

Another option if the gas giant has a significant magnetic field is electromagnetic tether propulsion or magnetic sails. These things sound high tech to us, but in this setting, whose science grew up in this environment, they would be a plausible advanced tech path. It could even be more steampunk, with spacecraft running Edison-style electric generators powering massive steel web magsails, navigated by captains who have gained an instinctive feel for the magnetic field patterns around the primary and its moons. These magships may not even be able to land, requiring shuttles, launch catapults and skyhooks to handle the surface-orbit stage.

ETA: I was just reading about the Io Plasma Torus. Could something like this be used like trade winds, giving a free velocity boost to magsail ships?

Re: [Space] Steampunk Firefly Idea
 

Ooh, that's a nifty idea. The combination of magsails and low-impulse trajectories gives a great feel.

If the moons are habitable, they probably require fairly significant magnetic fields of their own to shield from particles streaming off the gas giant. A sufficiently strong magnetic field and correspondingly excellent magsails would allow launch from the moons' surfaces, although only at their magnetic poles -- which also receive the concentrated particle flux, making them quite unhealthy. Magnetic shuttles, run by convicts and highly-paid short term volunteers?

Re: [Space] Steampunk Firefly Idea
 

The Mag Sail thing is interesting, maybe not for surface to orbit work, but for getting around once your in orbit, very nice. What I'll probably do for travel time is 1d-3, if the number is negative wait that number of weeks for magnetic null zone to clear, if 0 re-roll

Re: [Space] Steampunk Firefly Idea
 

I was Googling around for some more info on magsailing around inside Jupiter's magnetosphere, and there's suprisingly little out there. Atomic Rockets talks about magsails, but they're mainly focused on boring interstellar trips.

There was this one website however...
http://www.sjgames.com/gurps/Rolepla.../MagSails.html

Re: [Space] Steampunk Firefly Idea
 

Didn't know that was openly available -- excellent. Note that the magsails in GURPS Spaceships are at the 50 tons/ton of thrust level. If the magnetic liftoff stunt interests, you might want to use a superscience version capable of 0.01G per system (5 tons/ton of thrust).

Re: [Space] Steampunk Firefly Idea
 

Ganymede does, though it doesn't appear to be that strong.

Note that the magnetic poles can be at fairly low latitudes, so they could be in relatively temperate areas. Is it possible that they could stay fixed relative to the primary it's orbiting, while the moon's surface rotates under them? This would mean that there could be a band of launch sites on the surface in different countries- although I might be overestimating the thrust available from a magsail here.

Another possibility, going the superscience steampunk route, is that launch bases are built with massive powerful electromagnetic field generators, allowing magsail ships to be launched from the surface. Bases might have to be located near mountaintops and would look like heavy industrial sites. There might even be environmental fears that too many of these magnetic launch sites may disrupt the moon's natural magnetic field.

To be honest, this is probably the simplest solution. I don't know about a "null zone" though- maybe disruption from solar storms, the nearby passage of Io with its associated ion and plasma emissions, or magnetic storms from the gas giant instead.

I was thinking though about looking at a typical magsail journey. Once out of the moon's orbit, on a trip from one moon to another further out (like Europa to Ganymede), the ship first deploys sail to drag against the gas giant's magnetic field to start a Hohman transfer. This moves the ship from a higher circular orbit to a lower one, by passing through an elliptical arc with its periapsis on the lower orbit. The initial target orbit is in Io's high energy plasma torus, where the magsail can quickly pick up velocity on each pass to raise its apoapsis to the orbit of the higher destination moon. Once the right apoapsis is achieved, further acceleration impulses would be needed at the higher orbit to bring the craft into a circular orbit, or if the correction synchronisation is chosen the craft could slip directly into orbit around the destination moon. It seems that Europa at least also has a plasma torus, so this would also help with gaining orbital velocity. (All according to my imperfect understanding- corrections welcome.)

I'd imagine a magsail pilot sitting at controls with a number of compass globes showing the direction of magnetic field lines from sensors around the periphery of the ship, with one hand on the voltage control for the magsail and another on its tilt mechanism. He'd have charts and almanacs for the day's orbits and conjunctions of the major moons, and a telescope trained on the magsail at the end of its mile-long tether.

Action would be concentrated in short bursts at various periapsis and apoapsis passes, followed by long periods of waiting through the remainder of the orbits. Each orbit may take hours or days (comparable to the orbital periods of the moons?) so indeed passing from one moon to another could take a number of days.

Yep, you could play all that out, but it's probably better to simply roll dice for how long the journey takes.

Re: [Space] Steampunk Firefly Idea
 

The magnetic force lines of gas giant's are frequently described as tangled, the idea here was because of that they planet they where leaving from wasn't currently on a line of force, or if it was it wasn't useful

Very interesting and very steampunk, but I wonder is it's practical. At the very least these things are probably use some sort of vacuum-tube based electronics because of EM interferrance

Re: [Space] Steampunk Firefly Idea
 

For steampunk, I'd go with a mechanical analog computer, like the ones used for fire control on WW2 battleships (and retained on the Iowa class when the US Navy brought those back during the 80s). The spaceship is always going to need its flight computer, so lack of programmability isn't a problem.

Re: [Space] Steampunk Firefly Idea
 

So much to respond to and typing on my phone, so I'll just do a couple of highlights.

1. You might want to look at an article called Halfway to Anywhere from Pyramid #3/79 - Space Atlas. That will give you everything you need to sort out delta-V requirements for moving between worlds. Remember that your primary is the gas giant, and all masses and distances are in relation to Earth (because of the precidents set by Space). The raw formulae are also presented if you prefer SI units.

2. Jupiter's magnetosphere so thoroughly irradiates the gallilean moons, minus Callisto, that people will suffer acute radiation syndrome and die in days if not hours.

3. The further an orbit is from the primary, the lower the orbital energy, ergo the lower the orbital speed (an object's mass is independant of its location).

4. No form of lightsail or magsail provides anywhere neeeear enough acceleration to attempt a Hohhman transfer. Those will require a slow spiraling brachistochrone transfer (for more jnfo, please see Halfway to Anywhere).

5. Damned cool idea in general. Personally, I'd drop all TL7 stuff and look up the scientific assumptions of the Victorian period and treat them ALL as true. Base your spaceships on that. Make it "hard scifi" to what was known and you will better achieve the feel than trying to assume modern physics and chemistry - neither is very forgiving, especially when your only power sources are pressurized steam and gunpowder.

Re: [Space] Steampunk Firefly Idea
 

Remember, we're not talking about the Jovian system per se, except by analogy:
Humabout is correct about Hohmann orbits, but in a complex dynamical system (such as a gas giant with multiple moons) there are more efficient options than simple constant-thrust orbits. The math is difficult, however, and depends on the specifics of the system. It might be worthwhile to calculate the brachistichrone orbit as Humabout suggests, then reduce the time on a successful Navigation(Space) roll -- say, 10% per point of success, up to maybe 50%.

Re: [Space] Steampunk Firefly Idea
 

By definition, a brachistochrone transfer is the fastest transfer orbit possible. Rather, you should use it as a cap on how fast you can possibly reach a destination for any given acceleration. It would be reasonable, however, to increase travel time by any amount so long as it never exceeds a Hohhman transfer (the slowest transfer orbit). For low thrust transfers, I'd probably eyeball a minimum transfer duration at halfway between a brachistochrone and a Hohhman, just as a ballpark without any math behind it.

It's also worth mentioning that while Ganymede - and to a lesser extent, Europa - have magnetic moments, it's currently believed to be a result of a liquid ocean of saltwater moving beneath the frozen surface and is truly minuscule. IIRC, Europa's manages to shift the field lines of Jupiter's magnetosphere by all of 0.4% of a degree - which is how it was inferred.

Re: [Space] Steampunk Firefly Idea
 

... in a two-body system, which this is not.

Still not talking about the Jovian system per se. The OP specified moons of a gas giant in the habitable zone. These are highly unlikely to be icy bodies, since they would have a distressing tendency to melt. Differentiated rocky bodies, with an iron core, could certainly sustain a higher magnetic field. Moreover, to be habitable as specified they would have to be protected from radiation; therefore, they have significant magnetic fields.

A more interesting point is radiation protection for ships in transit and stations (either fixed or free-flying) beyond the protection of the habitable moons' magnetic fields. It's relatively easy to give the ships magnetic radiation shields as a collateral drive benefit. For stations, either allow limited "force fields" just for radiation shielding, or equip them with undersized drives just for the shielding benefit. Either way, their orbits would deviate slightly from pure gravitational -- but there's something majestic about visiting a station that sails, however slowly. A station-based drive field might also be configured to facilitate close-in maneuvering, providing a buffer for arrival and a push-off for departure.

Mini-magnetospheric plasma propulsion (M2P2) might be a better option than the superconductor loops in the Pyramid article, on the strength that they (a) don't require miles-wide physical structures and (b) they provide the radiation shielding automatically, as long as they are in use.

Re: [Space] Steampunk Firefly Idea
 

Yep, that makes sense. Except I'm still having trouble reconciling that with how speeding up takes you to a higher orbit, as in a Hohmann transfer which involves applying positive thrust to achieve a higher orbital energy. Wikipedia describes it this way-
(Simplistic highlighting mine.)
So looking at the delta-V would mean looking at how much velocity you add here, but when you look at the orbital speeds of moons in the lower and higher orbit, the higher orbit is slower, as you say, which means you have to subtract velocity. Now that could mean that a rocket in a circular orbit can be moving faster than a moon in the same orbit, and it has to slow down to match it in that orbit, but for a circular orbit radius and velocity are proportional, so being in a particular orbit implies a specific velocity. Obviously I'm missing something, not sure what it is- I'm guessing it's about angular velocity versus tangential speed or something.

I was basing that on this bit of text-
So, not talking about a 2 burn Hohmann transfer, but a low thrust orbital transfer. If technically a Hohmann is only a 2 impulse manoeuvre, then apologies. I was using it to mean matching an elliptical orbit's periapsis and apoapsis between circular orbits, regardless of how many impulses are used.

A brachistochrone transfer would require a constant thrust, which might be possible in a Jovian-style magnetosphere. I was imagining that tapping a high energy plasma torus in a lower orbit for a "perigee kick" might be more desirable, but proving this true would need a lot of computation. You'd also need to know the field strength of the magnetosphere along your orbit, the energy in the plasma torus, and how well your magsail can capture those and translate them to the desired kinetic energies.

Yep, I was just giving it as an example of moons having magnetospheres not being unreasonable.

Re: [Space] Steampunk Firefly Idea
 

Okay, I've actually skim-read that paper now. To try to summarise, there are points in a 3-body system, such as Jupiter-moon-rocket, where the rocket can apply small impulses to be captured by the moon, or to escape the moon's gravity and go back into orbit around the primary. Essentially, it means setting the periapsis to land in the moon's L2 Lagrange point.
Indeed the math is difficult. For example, the paper you quoted simplifies a 67 body problem with individual orbital inclinations to a 3 body problem in a circular plane. It would be useful for mission control, provided with exact orbital parameters for all bodies in the system and the ability to precisely calculate trajectories and impulse patterns, to carefully plan out a computerised low energy transfer mission months ahead.

For this low-tech setting though, there'd need to be some more empirical knowledge- pilots have mapped a number of transfer points where they can cross into a moon's orbit, for example. If they're Lagrange points, they could set up flashing buoys there which shouldn't move out of position.

Re: [Space] Steampunk Firefly Idea
 

If you are referring to coasting, that maneuver can be used to pick up speed regardless of transfer orbit if you hit the right launch window (which don't work with any wonderful frequency, and that will mess with regular resupply missions needed for colonization). If not, you're limited to brachistochrone transfers. For more information or to calculate these things based on information available from the system generation rules in Space or to generate figures usable with Spaceships, please refer to Halfway to Anywhere. If you want to generate full porkchop plots and sort out your transfers from there, here's a thread with lots of good info and a calculator. If you don't want to fuss with numbers, make ships move at the speed of plot - a speed that is always worth considering!

Very good! I was expanding on to previous comments regarding the Jovian system. Even if you would rather speak of other gas giants of which we have measurements, Saturn has a sizable magnetosphere, also. And it's expected that Uranus and Neptune will follow suit with proportional magnetospheres, too; although, theirs may be significantly weaker depending on how much metallic hydrogen is present in the planets.

Again, I was speaking about existing bodies orbiting an existing gas giant. Not fictitious moons five times the size of Mars. Such moons would likely have iron cores, and if those cores contain a molten component, they will have a measurable magnetosphere - after all, all of Mercury, Venus, and Mars have dead cores. Of these, Venus seems to show some degree of a magnetosphere induced by the interaction of the solar wind and the ionosphere, but this is extremely weak and does virtually nothing to protect the planet from cosmic radiation.

I again refer to existing gas giants as a point of reference. The magnetosphere of Jupiter is incredibly strong (10 times the strength of Earth's and 18,000 times the moment). To really put it in perspective, Jupiter's field strength is about 428,000 times the strength of the Sun's at Earth's orbit. This leads me to suspect that even a moon with an iron core won't have a field strength that can protect against the gas giant's planetary radiation belts.

For comparison, if Earth generated the same field that Jupiter does, the Van Allen Belt would extend more than three times the distance from the Earth to the Moon. A body half the size of Earth would have an even

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Since this conversation is derailing the thread, I'm only going to further respond to comments related to the OP's post.
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Energy shields kind of edges away from the steampunk aesthetic pretty fast, though. I'm not against sailing space stations, though. I'd just say the ether is real and they sail using that. Check out Spaceships 7 for a lot of awesome ideas for that sort of thing.

An interesting thought, but to get the kind of thrust you'd need, you still need a massive electromagnetic field that would lethal to human life. Although going with my suggestion to use science as it was understood in the Victoria Era, that could be ignored...but then again, so could planetary radiation belts. And really, you could fly through space on ether sails, too. Honestly, this is the sort of thing I'd pursue to get that steampunk feel. Also, FYI, superconductor loops are from Spaceships, p. 25.

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In conclusion, all of these references are to give perspective on the realistic depiction of such a system as modern science explains it today, regardless of how the OP chooses to portray it. Personally, I think this detracts from the steampunk vibe and would look up the Victorian understanding of such things (remember Mars had water and Venus was a jungle planet back then, too). I would personally pick and choose carefully to craft the vibe you want and go from there. It was a time of rapid scientific advancement, and you could decide any number of competing theories are correct, as it suits your story.

Re: [Space] Steampunk Firefly Idea
 

"Halfway to Anywhere" is an introduction to two-body orbital motion. The OP's setting, however, is a multi-body system, with many opportunities for clever tricks and shortcuts. For just one example, the orbital periods of the various habitable moons about the gas giant are likely on the order of days, not months or years. Some of them will be in resonant orbits, with periods that are simple multiples of one another. In this situation, launch windows to take advantage of gravity assists should occur nearly every day -- a very important fact for interlunar commerce.

The real-world gas giant moons are all thought to be heated by tidal forces, which would also apply to fictitious rocky moons. Being larger than Mars or Mercury would also argue for better internal heating from radioisotopic decay. The situation doesn't have to be probable, just plausible.

Yet, as you point out, the other gas giants have significantly smaller magnetic fields. A smaller or slower-rotating gas giant primary might still have a useful magnetic field but not so powerful that it renders its large, rocky moons uninhabitable. Again, plausible not probable. But this is an insight that may help inform the OP's world building.

The engineers who proposed the M2P2 system for crewed spaceflight clearly don't agree.

Re: [Space] Steampunk Firefly Idea
 

One that covers coasting and calculating launch windows, actually... And again, if the OP wants to break out n-body solutions, I've already linked to one resource that can help him. Unfortunately, GURPS won't help him, as it's planetary design system doesn't provide the requisite information. Of course, it is an interesting modeling exercise.

If you're going for "whatever is plausible," just make stuff up. If you're looking for something likely, consider that the only rocky planet or dwarf planet known to have an active metallic core is Earth, and that includes both an extra-hot planet right next to the sun (it's getting heat in spades) and Venus, a near duplicate of Earth in size, but with approximately 20% more solar heating. But yes, if you search all of the roughly estimated 100 octilliion stars, such a system probably exists somewhere several times over.

I am ignoring smaller gas giants because they are far less likely to accumulate enough of an accretion disk to produce the size moons the OP is talking about, and to manage to capture three might-as-well-be-planets in stable orbits sounds suspiciously unlikely. Again given an estimated 100,000,000,000,000,000,000,000,000,000 stars in the universe, yeah, it's probably happened somewhere. He will probably need to rely on this justification to have the kind of solar system he's talking about anyway. So he is certainly justified in handwaving this however he likes. It's just more likely to be a Jovian-scale giant rather than a Neptunian one.

Those who propose concepts rarely naysay their ability to perform usefully. And if you'd like, I'll go pull responses from other engineers who think it's not worth even considering. This is common anytime new technology is proposed. Only building and testing one would truly settle the debate...or then again maybe not. So yeah, it may be a cool idea, but from a worldbuilding perspective, what I'd ask myself is, "Is this steampunk? Does it fit the setting? Does it suit my story's purposes?" If so, run with it and handwave any "realistic" nonsense that gets in the way. If not, ditch it even if it's perfectly reasonable (otherwise he'd be using Saturn Vs to launch his lunar expeditions).

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I'd be curious to know what the OP's thoughts are in general. It strikes me that he probably doesn't care what some engineers think or even what an n-body system implies. But if he does, I'll gladly hit up some sources and pull more detailed information with proper references to papers. Otherwise, I'd like some creative direction so I can better give my uninvited advise :)

Re: [Space] Steampunk Firefly Idea
 

So 25% probability, with sample size n = 4?

Mercury and Venus both have exceptionally low rotational rates, which suggests that their examples should be considered with some care. Rocky moons, tidally bound but in orbits on the order of days, are in a different environment. As you yourself pointed out, the icy moons of Jupiter have small but measurable magnetic fields presumably derived from salt water oceans below their surfaces maintained by tidal heating.

<shrug> It's been peer-reviewed, with new results published off and on for the last 15 years. I don't see any of the nay-sayers in the published literature.

You are referring to M2P2 and not the so-called EM drive, though, aren't you? All of your linked threads were about the latter, which is a very different animal.

Re: [Space] Steampunk Firefly Idea
 

The difference between maintaining a temperature above 273 K to a depth of 75ish miles (or somewhere in that order of magnitude) of 975 miles and maintaining a core temperature above 1,811 K are two different things. Where I'd expect to see some interesting tidal effects would be on moons orbiting the a gas giant orbiting in the habitable zone of a red dwarf. The proximity of the two bodies should produce much larger tidal forces on those moons than a situation like Europa around Jupiter. Still not sure it's enough, though.

Re: [Space] Steampunk Firefly Idea
 

From what I remember of the relevant Transhuman Space playtests (and a few other sources) the radiation of Jupiter's magnetosphere is much less of an issue than appears to be assumed here.

It's al mid to low energy charged particles and in terms of Gurps radiation rules it multiplies PF by 20. Any probable ship hull (and perhaps especially something steampunkish made of iron or steel) should be able to stop those particles.

Likewise any atmosphere reaching Earth-like levels of breathability will stop such particles as well. The surface of some of the real world Galileans is dangerous to humans in thin-skinned suits or vehicles is because there is no significant atmosphere.

Re: [Space] Steampunk Firefly Idea
 

That would create some horrific motion of the ocean, so to speak. Quakes on the order of bad disaster movies ala 2012.

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Oh, I said "interesting" for a reason. :p There would be all sorts tectonic activity, I'd think, too - volcanism, earthquakes, etc. I'm not sure it'd be truly uninhabitable, but it'd be difficult to colonize.

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To that, you could also add that humans evolved in a high radiation environment may have adapted a resistance to that radiation (see the theory of radiation hormesis).

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That would then suggest that leaving the radiation zone would cause large increases in disease and ill health not at all obvious to the punkers.

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I'm not sure what you mean.
1) Leaving their native radiation zone would expose them to higher levels of radiation that they would be unprepared for, as radiation sickness is outside their realm of experience?
- But I expect their innate Radiation Resistance advantage would still be of benefit.

2) Entering a zero radiation zone would be detrimental to their health?
- As the Wikipedia page says, this hasn't even been studied yet, so I'm not sure why there'd be "large increases in disease."

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I like the notion of the mag sails to move ships around the system. It's evokes an exoticism that loans itself well to a steampunk feel. The vessels really are "spaceships" and not" spacecraft," and nautical terminology could slop over nicely.

See the book, The Wreck of the River of Stars for an example of how this might work. That's fairly hard science fiction, and even though Flynn isn't a great writer, it could be a useful resource for this sort of thing.

http://www.amazon.com/Wreck-River-St.../dp/0765334194

If we break down spaceship motion, it falls into four broad categories:
1. Launch from the surface of a planet, and/or break orbit.
2. Transfer from one orbit to another.
3. Maneuver to dock with space facilities.
4. Land on a planet.

Of the four, only the first needs a huge amount of energy expended, and it has to burn that energy in a short period of time.

Orbital transfers can take more time, and docking maneuvers had better go slowly or somebody's gonna get killed (or, at least, terribly upset). Neither requires a huge expenditure of energy all at once.

Landing is a unique situation, in that while it definitely qualifies as "energetic," any landing on a sizable planet with atmosphere means little of that energy actually needs to be in the spaceship. Atmosphere braking is pretty exciting, but it works really well and we have a lot of experience with it, by now.

Landing on massive planet with no atmosphere is a whole 'nother kettle of fish, and I'd think you'd just use specialized shuttle craft, for that, and all it a day.

So, to have a merchant vessel similar to the Firefly-class (and others seen during the program), you need a burst of energy to launch, the ability to transfer at will from one orbit to another, maneuver delicately and land without shaking things up, too much.

And all of that needs to take up no more than about a third of the total mass and volume of the spaceship.

We're definitely in hand-wavey territory, here. May as well go all in, and work to make it internally consistent, even if the underlying assumptions rank as Sheer Fantasy.

Given that this is Steampunk Firefly, I'd turn to Victorian science fiction for space travel ideas.

The number one most useful notion appears in First Men on the Moon by H.G. Wells.

In that book, Wells invents (whole-cloth) unobtanium known as cavorite, which has the incredibly useful ability to shield mass from the effects of gravity from a single direction. A spherical vessel of glass and steel, with "windows or blinds" made of cavorite, can be steered through interplanetary space.

I'd change that around, some, and harden it up a bit. I'd say cavorite blocks Higgs bosons from interacting with matter, but only if the cavorite has a powerful electrical charge. So, the way a space craft launches or breaks orbit is to suddenly discharge capacitors into the cavorite sheathing, which negates gravity's affect on the mass of the spaceship temporarily. This appears as a bright golden burst.

The cavorite need not cover the entire vessel, only the part that faces the planetary mass from which one needs to escape. So, a hemispherical section is enough, as long as the circumference of the hemisphere at the widest point is enough to block the rest of the vessel from the planetary mass.

A spacecraft either rests on legs or in a cradle with the cavorite boost section pointed at the planet. The legs get drawn in and the apertures covered by cavorite shutters so has to have an unbroken hemisphere. The capacitors discharge, the cavorite flashes bright gold, and ship zips away from the mass at the speed of the planetary rotation, at that point.

The burst only lasts long enough for the ship to reach geosynchronous orbit, at best (that's the regulatory standard, which old ships may not quite meet...) but that's all that's needed, anyway.

Once the ship reaches the stable orbit, the maneuvering pilot hands the helm to the sailing master, and he has the crew deploy the mag sail. (In small vessels, the pilot and the sailing master may be the same guy. In a really small vessel, the master and commander of the vessel may fill both roles, himself -- and he takes catnaps and drinks a lot of really strong tea or coffee, for the duration of the trip.)

Under the guidance of the sailing master, the ship breaks orbit and travels to the destination. Along the way, the steam turbine (fueled by powdered coal on older ships, kerosene on newer ships, and Nautilus-style radium engines for military vessels and those commanded by science-pirates) recharges the capacitors, and provides power to life support, the Babbage engine, and other vital systems. The smoke is vented out into space, of course, through telescoping smokestacks that extend out past the edge of the cavorite sheathing during interplanetary flight, so as to limit the buildup of soot on the hull. The vessel will also need sizable O2 tanks, just to keep the fuel burning (one reason the military vessels prefer radium engines, despite the hazards -- less mass for O2 means more for armor).

Once the ship gets close, the sailing master hands the helm back to the maneuver pilot, and he steers the ship to its final destination.

If the destination is a micro-gravity facility, the pilot just uses maneuvering thrusters. Compressed air is fine. If an atmospheric landing is necessary, he uses a combination of aerobraking and a burst of compressed steam to land the ship. Again, the cavorite shutters must be withdrawn from the nozzles of the steam thrusters.

Of course, a maneuvering pilot with "leaf-on-the-wind" levels of skill can play games with the cavorite burst, assuming the capacitors have a sufficient charge. While in orbit, he might be able to trigger a burst with only part of the sheathed section pointed at the mass, combined with the steam nozzles and the maneuvering thrusters, and produce tactically useful spins, gyrations and weird-ass deltas of all sorts.

All of these bits and parts mean a lot can go wrong on older ships. ("What was that?") But, hey. A hard-working crew needs something to spend their money on, right?

So, what do you think? Patently ridiculous, or silly fun?

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If we benefit/need a little more, and they benefit/need a lot more, why wouldn't a commensurate change in radiation have a commensurate change in disease?
Extremophiles don't just survive in extreme environements, they evolve to need them.

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Nah, you "adapt" to high radiation by successfully reproducing yourself and possibly even dying of old age before the radiation kills you. this is why the Chernobyl exclusion zone is a fine habitat for small rodents.

Hormesis may stimulate some systems in the short run but radiation sickness and/or cancer will get anything with a lifespan like a human.

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It does seem like a good rule of thumb that radiation tolerance goes down as rate of aging goes down. Grasses are hardy, while trees die at the drop of a rad.
Then again, don't forget that even humans have quite interesting radiation healing abilities. Those with xeroderma pigmentosum lack much of this suffering burns from even tiny amounts of UV and usually get skin cancer by age 10.

Really creepy are those single celled critters that can reform functional cells out of pieces fragmented from radiation damage like a family of T 1000.

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So the ship's velocity is imparted by the moon's rotation at take-off? This means equatorial launch sites are favoured, and that aerodynamics would be important. Also, exact time of launch would be important, but you could disengage the cavorite and go into orbit until you're on the target vector. However, why don't they just use gravity to navigate to their destination? It would be more powerful than low thrust magsails. Perhaps the cavorite is extremely energy intensive and can only be used for short durations, but then what advantage does it have over rockets?

So similar to how lack of exposure to sunlight causes rickets, bowel cancer and Seasonal Affective Disorder? Possible, but I don't see GURPS paying much attention to those things. What kinds of disease would you envision? And as some people are suggesting these moons would be bathed in radiation, no-radiation zones would only be low likelihood hazards.
I presume we're talking about the home moon of this human race, which evolved here over millions of years and have now reached a TL for space travel. That's why I said "evolved", not "raised". The link with radiation hormesis is just to show that there are mechanisms for dealing with high radiation levels and possible precedents in human populations. And the Wikipedia link is indeed suggesting that at certain exposures of radiation there is lower than expected rates of radiation sickness and cancer, not just in the "short run".

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Oh, you could certainly just use the cavorite to do it that way, and Wells' book, that's what they did. If the cavorite sheathing goes on shutters or flaps the pilot can manipulate finely, and doesn't require any sort of extra energy to work, then the ship can careen around the solar system like a pin-ball.

Basically, it's a reactionless drive that requires no energy input, and that's about as hand-wavey as it gets.

I was just trying to evoke a certain feel by introducing and energy requirement in such a way as to limit cavorite's utility enough to make mag-sails an attractive option. Rule of Cool, and all. :)

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Would limiting its efficiency do the job? Perhaps a fraction of the gravity still gets through, so you still need something else to provide thrust. Or it generates a spherical field, so there's no directionality to the contragrav effect.

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If that moon has an Earth-like atmosphere that atmosphere will completely protect from the sort of radiation seen in a gas giant's magnetosphere. It will even protect substantially from cosmic rays which are far more penetrative than the low-to-mid energy charged particles in question.

So any radiation to be adapted to (even if that is possible) must be from some other source.

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An earth like planet/atmosphere in the radiation belt of a gas giant would need an insanely powerful magnetic field to avoid having its atmosphere stripped away in geological time frames.
"Mild" solar wind stripped Mars' atmosphere away most likely due to an insufficient mag field.

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The notion of a spherical effect is an even more elegant justification, actually. Once the cavorite is activated, the vessel only has the vector it had upon activation. Deltas for actual navigation require an actual power source, and mag-sails are a nice solution for a steampunk space setting. Very evocative.

Make the industrial process that results in cavorite dependent upon a rare mineral, and you've got motivation for imperial expansion, as well -- especially if it's a bit more abundant on, say, Venus (a lush jungle world rich with life -- and big toothy predators -- where the richest deposits lie deep in the valleys where the atmosphere is so dense it requires humans to wear reduction masks, and the toothy predators all have wings).

Mars, of course, would be the source of weird science found in the desiccated ruins of ancient Martian cities, haunted by feral creatures and surrounded by violent, degenerate barbarians who struggle to survive. Dubbed "Reivers" by the British explorers who found them (and who managed to get a message out before they were eaten), the clever barbarians have started to build their own space craft, modeled on the British scout vessel they captured.

Soon, the solar system will scream.

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Heat Rays pretty much enable Laser Rockets at whatever TL you get them, so if you get Heat Rays at TL (5+1)^ you also get Laser ROckets

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You've got the laser part but how's your pointing ability? You might manage the gyrostabilization part with enough gleaming brass but you'd need to adjust your focus and aim your beam with more speed and precision than a human operator can probably manage,

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TL(5+1) means you get computers, OK their more Babbage calculating machines, but still.

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This is rather advanced TL8. You'd need TL5+3 or at least TL 5+1^

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Um, what? TL(5+1) can have crime solving robots and we're already applying Superscience, why couldn't they keep a gun pointing at a rocket

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TL5+1^ can have crime solving robots. Without the ^ you're not indicating superscience.

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At least there's a reasonable justification for all three moons to be habitable and life-bearing if just one is- lithopanspermia. Basically, ejecta from meteor impacts allow biological material to be shared between planets or moons.

You could posit that volcanoes or even violent storms could achieve the same function, and I was thinking about some kind of organism that had adapted to spending a period in space travelling between the moons.