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Jakub Glazik
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1. Am I right I cannot aerobrake with ship having only ion engines? There is no hourglass icon on these maneuvers, so my guess is no, but this is a little nonsense. Why ion engine spacecraft could not do it?

2. When I survey Jovian moon location with Galileo probe and reveal "Survey with Galileo probe" scoring card can I take it immediately?
 
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Will H.
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1. That is correct. The Ion Thruster does not generate enough velocity to rapidly change the angle of the spacecraft to aerobrake.

I am editing a solo playthrough video, and I unfortunately learn this after planning a multi-year mission to Jupiter!

2. That is also correct.
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Jakub Glazik
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Thanks for answer.

1. It's true what you have written that ion engines does not have enough TWR to suddendly change the direction. The problem is that does not explain anything at all. AFAIK aerobraking is planned much, much earlier than in the orbit or while flyby, course corrections are made in moments where any thrust is sufficient to change path (often in Lagrange points).
 
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Joe Fatula
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Aerobraking does not forbid ion thrusters; aerobraking is unrelated to ion thrusters in any way.

If a maneuver takes a year or more, you can use ion thrusters. If it's an immediate maneuver, you can't.

It happens to be that some maneuvers with the aerobraking hazard take time and some don't.
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David desJardins
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buffalohat wrote:
If a maneuver takes a year or more, you can use ion thrusters. If it's an immediate maneuver, you can't.


I think the question is why you need any thrusters at all for aerobraking.
 
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Larry L
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Presumably to get going in the right direction?
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Jordan Booth
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This game abstracts out RCS thrusters to make gameplay more streamlined. You may consider all spacecraft with and without any type of rocket and/or ion thrusters to have the necessary RCS thrusters (and accompanying fuel) to thematically perform whatever maneuver is allowed by the gameplay mechanisms.
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Jakub Glazik
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Thanks for contributing, Joe! And others too. Of course you all are right.

The thing is I have been missing there are aerobrake maneuvers with hour glass. I was looking/thinking only about Jovian and Saturnian systems where ion engines indeed cannot brake with atmo.

Sorry, but now I'm even more confused. Why is that? If aerobraking is harder in these gas giants why to allow "normal" spaceships to do this? Calculating aerobraking trajectory is exactly the same any ship, corrections could be made in deep space, when (almost) any thruster can make it with a little thrust.

Secondly, why ion engines can set aerobrake trajectory on Earth and Mars but not on Jupiter?

I'm not specialist, maybe I am missing something there?...
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Pawel Garycki
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Aerobraking with ions is possible on the route Outer Planets Transfer -> Earth Orbit. This could be used as a return route from outer planets and as a means to test aerobraking with ions only (less costly provided aerobraking succeeds when compared to Mars or Venus tesst). Just take ion thruster and two mass of anything, make it through diff. 6 to Outer planets, go to the earth orbit via aerobraking and divide the ship to three before actual aerobraking so that each component is tested separately.
 
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Will H.
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It's funny, because I was SO CLOSE to winning a very hard solitaire version of the game tonight.

I was bringing quite a complex spacecraft to Jupiter Orbit. First, both my astronauts died due to radiation (which could have been prevented with i) better rolls, or ii) bringing an Aldrin capsule and additional medics).

When my spacecraft arrived at Jupiter Fly-By and I looked at Aerobraking, I was pouring over the rule book looking for something that said I could not use my 6 Ion Thrusters for the difficulty 3 maneuver. I couldn't find anything, but the idea that I could not use them was stuck in my head for some reason.

The reason is because the maneuver does not list any time tokens, so they cannot be used for the maneuver. As Joe mentioned above, the actual aerobraking has nothing to do w/ Ion Thrusters (although it might indirectly based on how the maneuvers are abstracted onto the location cards).

I JUST put my game away, or I could look at the other locations and see if there are any with the aerobraking hazard and 1 or more time tokens. In that case, Ion Thrusters may work...
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Jakub Glazik
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gar0u wrote:
As Joe mentioned above, the actual aerobraking has nothing to do w/ Ion Thrusters
The thing is in this situation it does have.

I still don't get it but I have accepted it as is.
 
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Josh Zscheile
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I think I realize what your problem is. You do not understand why you can on most occasions only use aerobraking in untimed maneuvers, mostly from fly-bys to orbits around the same body.

Mechanically, to make it happen that Ions could be used for aerobraking around most bodies you would for each maneuver to a fly-by location of a body with atmosphere have to add another maneuver to the orbit with the aerobraking hazard. That means there would be two additional maneuvers on IPT (for Mars and Venus), one on Earth Orbit (for Mars), two on OPT (for Saturn and Jupiter), one on Venus Fly-By (for Jupiter) and one on Mars Fly-By (for Jupiter as well), which is a lot of additional maneuvers making the game board even more crowded with lines of symbols.

I propose you just treat it as if it is not known how dense the atmosphere on other bodies is, hence you cannot from far away (at least a year travel time) know how your insertion burn has to happen so that you can use aerobraking to slow yourself down just enough to achieve orbit.
 
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Jakub Glazik
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No. The problem I have is not "why I cannot aerobrake everywhere" but specifically "why I can aerobrake on Jupiter with conventional thrusters and can't with ions".

So, your first reasoning - althought acceptable - looses sense, because that's not my point. (BTW: In fact would be great to use aerobraking on Mars like TGO after dropping Schiaparelli. )

There is something in your second argument, but I don't get it fully. If the jovian atmosphere is unknown, why let even conventional thruster spacechips to aerobrake? Where is their advantage? Because of their power they could more efficiently change trajectory even in the last moment? If yes - it's the same with ion thrusters, AFAIK such correct maneuvers don't need much delta-v.
 
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Josh Zscheile
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Hmm, so I don't know what the Jupiter Fly-By to Orbit looks like right now (don't have my game around, or I would be playing all day and not working ...or, you know, writing stuff on BGG...), but I think I remember either a hard, timed maneuver or an easier untimed aerobrake, right?

I know that realistically, changing your orbit does not take that much thrust to do (once you are in one), but my attempt to reason here (the one of unknown atmosphere density) says that you are essentially plunging into the atmosphere and then applying thrust to get the periapsis of your orbit to a point you want it in (because you did not know how much drag the atmosphere would apply on your space craft before experiencing it). That kind of quick maneuvering inside an atmosphere can hardly be done by slow Ion Thrusters.

But maybe I am just overthinking the whole matter and the answer is: because Joseph Fatula, God of this Solar system and all its brethren in parallel universes, deemed it so.
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Jakub Glazik
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Dagar wrote:
I think I remember either a hard, timed maneuver or an easier untimed aerobrake, right?
That's right. I also don't have the game before me at the moment, but AFAIR it's 10 vs 3 difficulty.

Dagar wrote:
you are essentially plunging into the atmosphere and then applying thrust to get the periapsis of your orbit to a point you want it in (because you did not know how much drag the atmosphere would apply on your space craft before experiencing it).
And that's not exactly right. You already are in periapsis (lowest point) and you want to get apoapsis (highest point) to desired point, or - in this case - to create apoapsis at all, to convert from fly-by trajectory to closed orbit. (I have mistakenly written that TGO did that, but in fact it burned it's engine to "built" orbit, and future orbit adjustment will be made by aerobraking.)

Dagar wrote:
That kind of quick maneuvering inside an atmosphere can hardly be done by slow Ion Thrusters.
Yes, that could be explanation. But it would be really, really stragne. Because my point is (AFAIK) making burns in the atmosphere (beside being dangerous) is pointless because aerobraking itself gives huge braking power, so this differentiation between conventional and ion thrusters makes no sense to me. Aerobraking procedure occurs when it is too late to make any corrections, all should be computed and prepared BEFORE entering atmosphere, while beeing in the space, and there is no need for huge amounts of delta-v for making correction maneuvers. Even ion engines could do it.

Dagar wrote:
But maybe I am just overthinking the whole matter and the answer is: because Joseph Fatula, God of this Solar system and all its brethren in parallel universes, deemed it so.
And I can fully accept such explanation in the game universe. It's just a game after all. I am just wondering.
 
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Josh Zscheile
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Yeah, I mixed up Peri- and Apoapsis, apparently. My point is, what if you plunge too deeply into the atmosphere (because you thought it was thinner), and you have to thrust prograde quickly to get out of it in order not to spiral down into Jupiter until you get squished? That's something Ions could not do for you. But you already know this, and I know this explanation is not perfect. Let's just leave it at that and enjoy the game (as much as we can without having it with us )
 
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