Travel within the Jovian System

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EtherExsurgent EtherExsurgent's picture
Travel within the Jovian System
My players are based out of Locus and have stayed in the Jovian Trojans for the most part, but at the end of our game session last Thursday they have decided to take a ship from the Trojans to the Greeks. My question is how long does it take to travel between L4 and L5 and is the Jovian Republic going to charge them a toll for crossing Jupiter? Also would the Jovians expect a flight plan before hand? Apologize if this is covered somewhere but I couldn't find it. As always any help is appreciated.
ORCACommander ORCACommander's picture
I think the real question is
I think the real question is how close do they come to any jovian habs and the probability of stumbling across a patrol.for the habs probly best to file a flight plan and well ya better for the latter. i would think the jovians would be more keen on interdicting jupitar space rather than charging tolls but just remember space is VAST and Light takes a long time to get anywhere. so you have to figure out how good the junta's passive sensors are and for active systems what kind of range can be expected. I recommend reading some honor harrington for good concrete examples on passive and active detections systems in space over light minutes
EtherExsurgent EtherExsurgent's picture
The books made it seem like a
The books made it seem like a lot of the income for the Jovians comes from the slingshot tolls so figured they must have tracking posts and some of their military ship scattered around the system for enforcement. I did find the travel times between the Jovian L4 and L5 points. Its 59 days, which may be longer than my group wants to take to get there. It's easy to forget just how large the whole Jovian system actually is.
Rallan Rallan's picture
They'll definitely demand a
They'll definitely demand a toll (I can't imagine getting from the Trojans to the Greeks without using Jupiter for a gravity assist), and they'll definitely demand a flight plan. They're tired of freeloaders and blockade runners trying to dodge the toll and they're paranoid about saboteurs/smugglers/whatever trying to infiltrate their colonies, so they'll probably want a flight plan for their approval before you get anywhere near them, and they'll have all sorts of dire warnings about why you shouldn't deviate from that plan.
Jaberwo Jaberwo's picture
I am not sure if you need to
I am not sure if you need to cross the Jovian system at all. My astrodynamics is from Kerbal Space Program, but if you are on the same orbit as your target, but separated by some path lenght on this orbit you lower or raise your orbit (depending on whether you need to go forward or backward) and leave the original orbit. Therefore you would not meet Jupiter, as it is still on the original orbit. Even if you go full throttle accelerating the whole time as some ships (even normal ones possbibly) can do, you would draw a straight line between two distant points on a circle not crossing the circle anywhere else. There might be techniques that save fuel by a slingshot maneuvre, but I don't know about that.
Undocking Undocking's picture
There are three ways of
There are three ways of reaching the Greeks from the Trojians. 1) the Trojans are the leading Lagraigan Point (60º ahead of Jupiter), so technically, they can accellerate along Jupiters orbit all the way around into the Greeks. This would take a long time, as you are covering 240º of the Orbit. 2) Use Jupiter as a slingshot. The quickest and most fuel efficient. 3) Accelerate towards the Greeks but diverge from the Laplace Plane, enough not to be effected by Jupiter's well enough to be qualified as a slingshot. This would require some sort of acute angle and would be less fuel efficient than the second option, but quicker than the first.
EtherExsurgent EtherExsurgent's picture
Thanks for the information.
Thanks for the information. Sent text to my players and they are trying to decide on there course of action. Story wise I think just having to deal with the Jovian military even a little will make things more interesting. I'm imagining all the Jovian personal operating the toll system are just assholes and love being able to make harass the smaller ships moving in system.
Aldrich Aldrich's picture
Orbital Mechanics
Undocking wrote:
There are three ways of reaching the Greeks from the Trojians. 1) the Trojans are the leading Lagraigan Point (60º ahead of Jupiter), so technically, they can accellerate along Jupiters orbit all the way around into the Greeks. This would take a long time, as you are covering 240º of the Orbit. 2) Use Jupiter as a slingshot. The quickest and most fuel efficient. 3) Accelerate towards the Greeks but diverge from the Laplace Plane, enough not to be effected by Jupiter's well enough to be qualified as a slingshot. This would require some sort of acute angle and would be less fuel efficient than the second option, but quicker than the first.
Unless I'm misunderstanding what you mean, I'm afraid none of these ways actually work - you can't "accelerate along Jupiter's orbit". Orbital velocity is fixed as a function of distance. So if you're parked at the Trojans, then in the Sun's reference frame you're orbiting at the exact same speed as Jupiter. If you want to get to the Greeks, you have two options: - switch to a (faster) orbit closer to the Sun, and then switch back to Jupiter's orbit as you approach the Greeks from "behind" - switch to a (slower) orbit further away from the Sun, and then switch back to Jupiter's orbit as the Greeks approach *you* from "behind" Either one would probably put you far enough away from Jupiter to not involve the government, but that's something that I would totally hand-wave in favor of narrative. If it helps your story to have Jovian customs agents demand that you heave-to and prepare to be boarded, then that's what happens. And you definitely wouldn't want to try to fly "over" or "under" Jupiter in the plane of the ecliptic, because that has *no* effect on your orbital velocity, it just changes your orbital inclination. Any energy spent going "up" or "down" doesn't get you closer to the Greeks and just has to be canceled out later.
Jaberwo Jaberwo's picture
That's what I was trying to
That's what I was trying to say, in this case you would of course want to switch to a slower orbit further away from the Sun, as your target is 120° of orbit behind you, but 240° in front of you. Paradoxically you have to burn in the oposite direction of where your target is, along your orbit. You could then circularize your orbit and wait for the target to catch up and decelerate so that you encounter it. Maybe you don't need to circularize and do the first burn in such a way that you coast outward some time and then come back at the right moment, but I am not sure if that gives you any advantage in speed or delta v. But what happens if you have lots of delta v? There are certainly very fast trajectories where you burn constantly, maybe a straight line like I mentioned before? I would not want to rule out a gravitiy assist either, but I have struggled to get an intuitive feel for them so far. As it seems to me it is complicated enough that you can get away with anything that fits your story. Nobody says the Jovians can't make an excursion and board you millions of miles away from their system as an exercise.
Undocking Undocking's picture
Aldrich wrote:
Aldrich wrote:
Unless I'm misunderstanding what you mean
In my attempt to make the concepts simple, I did reduce them too much. It was sloppy, and I'm glad you provided a better post.
Jaberwo Jaberwo's picture
While we're at it: Does
While we're at it: Does anyone have experience with a mission/orbit planner software and can recommend something? I recently downloaded GMAT but didn't have the time to try it out. Seems complicated though.
Aldrich Aldrich's picture
No worries!
Undocking wrote:
Aldrich wrote:
Unless I'm misunderstanding what you mean
In my attempt to make the concepts simple, I did reduce them too much. It was sloppy, and I'm glad you provided a better post.
No worries! I could tell you were trying to simplify, I just wasn't sure how much :)
Jaberwo wrote:
But what happens if you have lots of delta v? There are certainly very fast trajectories where you burn constantly, maybe a straight line like I mentioned before?
Yes, if you have unlimited reaction mass you can continuously accelerate towards where your target is going to be, flip around at the midway point, and decelerate the rest of the way. That's a very pulp scifi approach: Atomic Rockets has a good discussion of that type of ship ( http://www.projectrho.com/public_html/rocket/ ). However, EP is a hard scifi setting, so this simply wouldn't make financial sense. An antimatter rocket like the courier on page 347 of the core book might be able to do something similar, but those are extremely expensive ships and extremely expensive to fuel. Players probably aren't scooting about in one!
Jaberwo wrote:
While we're at it: Does anyone have experience with a mission/orbit planner software and can recommend something? I recently downloaded GMAT but didn't have the time to try it out. Seems complicated though.
I can't personally recommend any of these, but have you seen this list? http://space.stackexchange.com/questions/646/what-are-the-choices-today-... If you don't already have it, I *highly* recommend the game Kerbal Space Program. It has a super-active modding community, including a set of full conversion mods to the real solar system, realistic fuels and engines. That might suit your needs and is entertaining to boot!
Jaberwo wrote:
As it seems to me it is complicated enough that you can get away with anything that fits your story. Nobody says the Jovians can't make an excursion and board you millions of miles away from their system as an exercise.
Exactly! :)
Eridan Eridan's picture
Don't forget Egocasting ;)
Don't forget Egocasting ;)
Host of The Tabletop Review Podcast www.TheTabletopReview.com
Jaberwo Jaberwo's picture
Aldrich wrote:Yes, if you
Aldrich wrote:
Yes, if you have unlimited reaction mass you can continuously accelerate towards where your target is going to be, flip around at the midway point, and decelerate the rest of the way. That's a very pulp scifi approach: Atomic Rockets has a good discussion of that type of ship ( http://www.projectrho.com/public_html/rocket/ ). However, EP is a hard scifi setting, so this simply wouldn't make financial sense. An antimatter rocket like the courier on page 347 of the core book might be able to do something similar, but those are extremely expensive ships and extremely expensive to fuel. Players probably aren't scooting about in one!
You are of course right, I was in the mindset of the military crew in one of my games, their vessel has 500 km/s and not enough acceleration to get rid of it before reaching its target a lot of the time. It's a different case for things like ion drives or other low thrust high specific impulse systems. I am trying to get a feel for those at the moment.
Aldrich wrote:
I can't personally recommend any of these, but have you seen this list? http://space.stackexchange.com/questions/646/what-are-the-choices-today-...
That's where google lead me as well :D
Aldrich wrote:
If you don't already have it, I *highly* recommend the game Kerbal Space Program. It has a super-active modding community, including a set of full conversion mods to the real solar system, realistic fuels and engines. That might suit your needs and is entertaining to boot!
Like I said, my knowledge is almost exclusively derived from that game, it's the best I've had in years. The planning unfortunately is difficult to do in advance and with precision. In addition, the aforementioned low thrust systems are a bit of a hassle. Also, building rockets is hard.
Chernoborg Chernoborg's picture
Ah, the wacky counter
Ah, the wacky counter-intuitive world of orbital mechanics. Apply thrust in the direction you want to go - move into a different orbit that takes you away from where you want to go! I wouldn't doubt that the Jovians have a couple clusters of customs frigates (corvettes? Dang! broke alliteration :P) at the Jupiter-Sol L1 and L2 points. These are useful for both policing the traffic between the Trojans and Greeks and having the high ground from which to launch customs interceptions. How far those points are from Jupiter I don't know as I've yet to find a Lagrange points calculator or distances chart ..that would answer SO many questions!
Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!
EtherExsurgent EtherExsurgent's picture
I actually went with the
I actually went with the Jovians having several customs ships and a couple of small asteroids set up to police the area. Smugglers and those avoiding the gravity well surcharge know where the asteroids generally are but the ships can be anywhere. Thanks for all the help and ideas with this.
Chase-san Chase-san's picture
Using standard orbital
Using standard orbital mechanics to get around the Jovian system would take a very long time. With low delta-v you could probably swing around the sun and make it back to the Greeks in a few years if you do it all correctly. (You could probably swing around another planet, such as mars sooner if things line up, aiming outward is ill advised.) Luckily, this is the future, and we have lots and lots of lovely delta-v. If you have lots of delta-v and a way to use it quickly, the fastest way would be to burn retrograde until you reverse your orbit and swing back towards Jupiter, then use a gravity assist to throw you out towards the Greeks. Then burn prograde to reverse your orbit again and slow down before you run into them. That will get you there in maybe a month or two. You always can burn towards them until you are half way there, and then burn backwards to slow down. With enough dV and thrust you could in theory get there faster (maybe a week or two at a not completely unfeasible dV+thrust), but that would take a lot of fuel and a very light ship.
Aldrich Aldrich's picture
Jupiter's L4 and L5 Points
Chernoborg wrote:
How far those points are from Jupiter I don't know as I've yet to find a Lagrange points calculator or distances chart ..that would answer SO many questions!
Jupiter's real world Lagrange points aren't points per se. They're spread out over a very large area. Here's an image of some of the asteroids that are caught in Jupiter's L4 and L5 points: This is the sort of thing I'd definitely abstract away from, unless you're into that sort of detail, of course :) I don't have a calculator offhand, but I remember a guy from JPL recommending one to me a while back. I'll see if I can find that email and link you to it...
ShadowDragon8685 ShadowDragon8685's picture
Hey, I just noticed - there's
Hey, I just noticed - there's a [b]single[/b] green one at the L3 point. I wonder what's out there in EP? Somebody had to build on it. That gif is extremely useful, though. It gives a tangible sort of look at just [i]how massive[/i] Jupiter is and what kind of effect it actually has on the solar system. I used to find myself at best bewildered, at worst skeptical of the idea that Jupiter alone could deflect incoming planet-killers. Now it's like... How could it [i]not?![/i] there'd be very few incoming vectors/velocities that would result in a hit on Earth, anything else would be deflected between Jupiter and the Sun and go off higgeldy-piggeldy. I wish there was a larger one to show the entire system.
Skype and AIM names: Exactly the same as my forum name. [url=http://tinyurl.com/mfcapss]My EP Character Questionnaire[/url] [url=http://tinyurl.com/lbpsb93]Thread for my Questionnaire[/url] [url=http://tinyurl.com/obu5adp]The Five Orange Pips[/url]
Chernoborg Chernoborg's picture
Aldrich wrote:I don't have a
Aldrich wrote:
I don't have a calculator offhand, but I remember a guy from JPL recommending one to me a while back. I'll see if I can find that email and link you to it...
That would be great, thanks! Unless you're trying to get rid of me...yeah, that would do it for a while! :) Mostly I'm looking for L1 and L2 locations. Whenever something is said to be "in a geostationary orbit" to a moon it makes my eye twitch. So I figure those Lagrange points are what they're talking about, but then I want to know if it works relative to the rest of the system. It would be no good to move Phoebe to Saturn-Titan L1 only to have it crash into Rhea!
Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!
Rallan Rallan's picture
Oh and here's what those
Oh and here's what those brown bastards are doing. [img]http://upload.wikimedia.org/wikipedia/commons/7/7a/HildasOrbitWithLagran... As a bunch they look like they're doing some weird triangular craziness, but individually it's not all that fancy. Note how its orbital period is timed so a different one of the Lagrange Points is swinging on by every time it reaches aphelion.
ShadowDragon8685 ShadowDragon8685's picture
Rallan wrote:Oh and here's
Rallan wrote:
Oh and here's what those brown bastards are doing. [img]http://upload.wikimedia.org/wikipedia/commons/7/7a/HildasOrbitWithLagran... As a bunch they look like they're doing some weird triangular craziness, but individually it's not all that fancy. Note how its orbital period is timed so a different one of the Lagrange Points is swinging on by every time it reaches aphelion.
Maybe this is just my Kerbal showing, but if that were the case, wouldn't it be almost [i]trivially[/i] easy in Eclipse Phase to apply just a little bit of thrust when they're at their periapsis and push their AP up and [i]into[/i] the lagrange point? And then let the L-point's gravity give you a huge assist in bringing the periapsis into the same plane, thus leaving it in the L-point permanently?
Skype and AIM names: Exactly the same as my forum name. [url=http://tinyurl.com/mfcapss]My EP Character Questionnaire[/url] [url=http://tinyurl.com/lbpsb93]Thread for my Questionnaire[/url] [url=http://tinyurl.com/obu5adp]The Five Orange Pips[/url]
Rallan Rallan's picture
ShadowDragon8685 wrote:Rallan
ShadowDragon8685 wrote:
Rallan wrote:
Oh and here's what those brown bastards are doing. [img]http://upload.wikimedia.org/wikipedia/commons/7/7a/HildasOrbitWithLagran... As a bunch they look like they're doing some weird triangular craziness, but individually it's not all that fancy. Note how its orbital period is timed so a different one of the Lagrange Points is swinging on by every time it reaches aphelion.
Maybe this is just my Kerbal showing, but if that were the case, wouldn't it be almost [i]trivially[/i] easy in Eclipse Phase to apply just a little bit of thrust when they're at their periapsis and push their AP up and [i]into[/i] the lagrange point? And then let the L-point's gravity give you a huge assist in bringing the periapsis into the same plane, thus leaving it in the L-point permanently?
It's probably not a great idea to copy that orbit. It'l take you two thirds of a Jovian year to get from one Lagrange to the next.
EtherExsurgent EtherExsurgent's picture
The GIF is great, thanks for
The GIF is great, thanks for posting it. I showed one of my players, who was having trouble understanding what the Jovian system looked like, and as soon as he watched it he understood it so much better.
ORCACommander ORCACommander's picture
hehe that is not even the
hehe that is not even the complete Jovian System *loads up Universe Sandbox* Youtube: http://youtu.be/BfhTSoeRu20 ya i know the sun is not in this but i couldn't be arsed to properly add it in was originally going to make a light weight gif but the smallest i made was 83 megs :/
Chernoborg Chernoborg's picture
You own stock in the company
You own stock in the company that makes that, don't you?
Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!
ShadowDragon8685 ShadowDragon8685's picture
Rallan wrote:ShadowDragon8685
Rallan wrote:
ShadowDragon8685 wrote:
Rallan wrote:
Oh and here's what those brown bastards are doing. [img]http://upload.wikimedia.org/wikipedia/commons/7/7a/HildasOrbitWithLagran... As a bunch they look like they're doing some weird triangular craziness, but individually it's not all that fancy. Note how its orbital period is timed so a different one of the Lagrange Points is swinging on by every time it reaches aphelion.
Maybe this is just my Kerbal showing, but if that were the case, wouldn't it be almost [i]trivially[/i] easy in Eclipse Phase to apply just a little bit of thrust when they're at their periapsis and push their AP up and [i]into[/i] the lagrange point? And then let the L-point's gravity give you a huge assist in bringing the periapsis into the same plane, thus leaving it in the L-point permanently?
It's probably not a great idea to copy that orbit. It'l take you two thirds of a Jovian year to get from one Lagrange to the next.
I wasn't talking about using it for travel (unless you REALLY like taking things slow,) I was talking about boosting one of those belt objects migrating between the Lagrange points and putting them permanently in a Lagrangian orbit.
Skype and AIM names: Exactly the same as my forum name. [url=http://tinyurl.com/mfcapss]My EP Character Questionnaire[/url] [url=http://tinyurl.com/lbpsb93]Thread for my Questionnaire[/url] [url=http://tinyurl.com/obu5adp]The Five Orange Pips[/url]
ORCACommander ORCACommander's picture
Chernoborg wrote:You own
Chernoborg wrote:
You own stock in the company that makes that, don't you?
hehe nope if i did i would of monetized the video ;)
Aldrich Aldrich's picture
Chernoborg wrote:Aldrich
Chernoborg wrote:
Aldrich wrote:
I don't have a calculator offhand, but I remember a guy from JPL recommending one to me a while back. I'll see if I can find that email and link you to it...
That would be great, thanks! Unless you're trying to get rid of me...yeah, that would do it for a while! :)
Just popping back in to say that I hadn't forgot about this! I can't find the email I'm thinking of with a quick search, so I'll need to do some more intensive digging - but I can't right now because I'm in the last two weeks of the last quarter of my MS, so things are... busy.
ORCACommander wrote:
*loads up Universe Sandbox*
10$? I'm sold, that looks like a pretty sweet program!
Rallan Rallan's picture
ORCACommander wrote:hehe that
ORCACommander wrote:
hehe that is not even the complete Jovian System *loads up Universe Sandbox* Youtube: http://youtu.be/BfhTSoeRu20 ya i know the sun is not in this but i couldn't be arsed to properly add it in was originally going to make a light weight gif but the smallest i made was 83 megs :/
Isn't your video just of the stuff that's in orbit around Jupiter itself?
ORCACommander ORCACommander's picture
Yes it is. it is just the
Yes it is. it is just the default layout of the jupiter sim in the program. Yes i could add the sun but then i would have to adjust all the x,y,z coordinates of everything there, redefine jupiter with an orbital velocity. further if you wanted those lagrange asteroids simulated i would need estimated masses and coordinates for them and preferably velocities but i guess i could let the sim sort that one out there really my only true point is that the Jovian System is rather massive in cubic volume with lots of stationary orbits to hide things in
consumerdestroyer consumerdestroyer's picture
This thread is saving me a
This thread is saving me a lot of headache trying to plot out some things for my game!
Rallan Rallan's picture
ShadowDragon8685 wrote:
ShadowDragon8685 wrote:
I wasn't talking about using it for travel (unless you REALLY like taking things slow,) I was talking about boosting one of those belt objects migrating between the Lagrange points and putting them permanently in a Lagrangian orbit.
Ah, gotcha. Probably happens all the time as a lazy way of getting more raw materials. And I wouldn't be surprised if there's a fair number of stations scattered among the Hildas themselves. It's a pretty empty part of space even if it is the third busiest patch of asteroids in town (after the Main Belt and the Jovian Trojans), but you come within kissing distance of a Jovian Lagrange every eight years or so, and every 24 years your orbit lines up with Jupiter and you pass through the busiest space lane in the outer system. So it'd be ideal for Brinker settlements who still want reliable (if infrequent) trade with the rest of transhumanity.