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Leaving Earth: Outer Planets» Forums » General

Subject: Jupiter maneuvers rss

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Joe Fatula
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In case anyone's interested, here are the main maneuvers for the Jupiter system (edited):

# = difficulty, {#} difficulty only available certain dates,
#yr = years, ?yr = optional years
hazard, (optional hazard)

Venus Fly-By
-> Jupiter Fly-By {1} 1yr solar jupiter

Jupiter Fly-By
-> Jupiter Orbit 3 jupiter aerobraking
-> Saturn Fly-By {0} jupiter 2yr solar
-> Outer Planets {4} 2yr solar
-> Lost ! jupiter
From Jupiter Fly-By you can survey any of the moons of Jupiter.

Jupiter Orbit
-> Jupiter Fly-By 10 jupiter ?yr
-> Ganymede Orbit 3 jupiter ?yr
-> Io 2 jupiter ?yr landing io
-> Europa 2 jupiter ?yr landing europa
-> Callisto 5 ?yr landing callisto
If you end the year in Jupiter Orbit, you face the Jupiter hazard.

Io
-> Jupiter Orbit 2 ?yr
If you end the year on Io, you face the Jupiter hazard.

Europa
-> Jupiter Orbit 2 ?yr
If you end the year on Europa, you face the Jupiter hazard.

Ganymede Orbit
-> Jupiter Orbit 3 ?yr
-> Ganymede 2 landing ganymede

Ganymede
-> Ganymede Orbit 2

Callisto
-> Jupiter Orbit 5 ?yr
-> Jupiter Fly-By 5 jupiter
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Will H.
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Cannot wait for this to come out!

Looking forward to more places to go.
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Larry L
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Difficulty 10. I wonder what that means for new rockets or thrusters.
 
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Darryl Roy
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Hi Joe, I just placed an order for the base game and I'm looking forward to the expansion.

I hope there will be some provision for not just gravity assisted slingshots to Saturn & the Outer Planets, but gravity assisted returns. It looks like you're treating the outer Galilean (Callisto) as an inner Galilean there. Is that a typo? The surface escape is not so different from Ganymede, and Callisto has something the more inner Galilean's lack: a potential highly ellipitical Jovian orbit.

ΔV for Io capture orbit (ie, orbiting Jupiter at Io's distance) to an Earth transfer Hohmann is 10.6 km/s. This is in addition to a ΔV of 2.5 km/s to escape Io. The comparable ΔVs for Europa are 9.2 and 2.0 km/s. Returning from Io's or Europa's surfaces is not going to happen without high-thrust nuclear designs, which may not be in the scope of your game.

However, the situation on Callisto (and perhaps Ganymede) is perhaps different. I just reread Zubrin's Entering Space, and here's the relevant passage:

Quote:
It will require a ΔV of about 2.4 km/s to take off from Callisto and reach a highly elliptical parking orbit about the moon. There you refuel, or transfer yourself and some propellant to a dedicated interplanetary spacecraft, and then execute a ΔV of 1.4 km/s to depart Callisto onto an elliptical orbit with its closest approach to Jupiter at 489,000 km from the planet's center. This orbit will have a period exactly half that of Callisto's, so after two of your orbits you will meet Callisto again (16.7 days later). Along the way, you make it your business to pass close by either Europa or Ganymede and use their gravity to distort your orbit a bit, so as to give you an increased encounter velocity when you return to Callisto. At that point you perform still another gravity assist to lower your closest approach to Jupiter to 78,540 km from the giant's center, which means you will pass above its surface at an altitude of 7,150 km. This will take you through the thick of Jupiter's radiation belts, and any crew or sensitive electronics aboard will have to be well shielded. Because you have dived so low, your velocity at minimum altitude will be an enormous 51.7 km/s (nearly 125,000 mph). Jupiter's escape velocity at that altitude is 16.8 km/s, so a little extra push of 1.1 km/s would allow you to depart into interplanetary space.

Departing Jupiter at high velocity using high-thrust rockets (km/s
Rocket ΔV Max velocity Departure velocity
1.1 56.8 0
1.5 57.2 6.8


Ie, from Calisto's orbit, you can make a not much greater than 2.5 km/s burn (s) to do a transfer orbit to anywhere in the solar system, including Earth.


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Joe Fatula
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darrylsroy wrote:
It looks like you're treating the outer Galilean (Callisto) as an inner Galilean there. Is that a typo?

Actually, the division in treatment here isn't between inner and outer moons, but between smaller and larger bodies. To avoid having far too many locations, small bodies in the game don't have a separate orbit card. Ceres, for example, has only a Ceres card, so the Δv of getting there is really the Δv of getting to orbit plus the Δv of landing.

A closer simulation than Leaving Earth would have separate locations for each moon's surface and orbit, as well as several different orbits around Jupiter.

darrylsroy wrote:
Ie, from Calisto's orbit, you can make a not much greater than 2.5 km/s burn (s) to do a transfer orbit to anywhere in the solar system, including Earth.

Now this is quite interesting. So far, I had only been looking at the Δv requirements of going from one moon to another, and of getting in and out of the Jupiter system directly. But this method, where you slingshot around Jupiter itself from Callisto, sounds very interesting. (From the description, I assume this is using the Oberth effect to make better use of propulsion at periapsis.)

In game terms, this would be a fairly cheap maneuver from Callisto to Jupiter Fly-By (or to the Outer Planets Transfer point) that causes you to face the Jupiter hazard (which is likely to be heavy radiation).
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