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interplanetary travel without phasing angle?


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I'm sure someone can give a more precise answer but the short of it is you either fast forward to the next window or use extra ÃŽâ€V. Depending on how far out of the ideal launch window, it can require significantly more fuel to get there.

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Well, that rather depends on a number of factors. You might still be able to make some adjustments to get a Duna encounter, but it might end up taking a good bit of fuel. If you're already grazing or intersecting Duna's orbit, you could try to timewarp until you get a fairly close encounter you could adjust for.

Alternately, pull a "Luna 1" and tell everyone that you just launched your first solar investigation probe :wink:

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You don't really have to wait for the planets to align. Just escape Kerban SOI and plot a maneuver node in the right place and go to Duna. Treat it like a regular intercept the way you would if you were docking ships in orbit around Kerban. When you escape the Kerban SOI, it helps if you're going prograde in relation to the planet Kerban's orbit around the sun. Think of Kerban as a periapsis.

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You don't really have to wait for the planets to align. Just escape Kerban SOI and plot a maneuver node in the right place and go to Duna. Treat it like a regular intercept the way you would if you were docking ships in orbit around Kerban. When you escape the Kerban SOI, it helps if you're going prograde in relation to the planet Kerban's orbit around the sun. Think of Kerban as a periapsis.

Actually, this is *not* the way to go. It would mean speeding up to the speed Duna has, which means you have to spend *quite* a bit of fuel. The best thing to do is fiddling around with maneuver nodes a bit and try to find the cheapest encounter.

Also.... I don't know how you would orbit the sun clockwise? Could you give me an example of how to achieve such an orbit? I can only think of building a big-ass rocket with nervas to cancel out all orbital velocity, but this would take a rocket with some 15000m/s delta v. Which is a lot.

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Also.... I don't know how you would orbit the sun clockwise? Could you give me an example of how to achieve such an orbit? I can only think of building a big-ass rocket with nervas to cancel out all orbital velocity, but this would take a rocket with some 15000m/s delta v. Which is a lot.

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He meant leaving Kerbin SoI retrograde, you will still orbit Kerbol prograde but at a reduced velocity (kerbin orbital velocity - your escape velocity, give or take).

I also feel you are better tweaking your trajectory to try and get yourself an encounter. If you've set duna as target then you should see the 'closest approach' and 'target postition at closest approach' markers, play with a node and see which way they slide, try and bring em together. If the markers are more or less opposite each other then you are really out of phase, your best bet for encounter then (barring a bunch of time-warp orbits) is probably a burn at your solar apoapsis and try for an encounter with duna on the opposite side of the system. This will be reeeaaallly expensive in fuel, hope you have a NERVA if this is the case.

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hello, i was trying to send a duna probe but i forgot to wait till kerbin and duna align. what should i do now?

That depends on what you did.

If you just exited Kerbin SOI and are on orbit around Sun very close to Kerbin orbit, select Duna as target, place a maneuver on your orbit and try to get an encounter like if you were doing Mun encounter from Kerbin orbit.

If you executed the whole burn and your trajectory touches Duna trajectory but does not meet Duna there, then match inclinations if you didn't do that already and put a maneuver at the point where the two orbits touch. Now try to "inflate" your orbit a bit and check if you can get an encounter without exceeding Duna orbit. If you can't, the easiest thing to do is wait one orbit and try again. There are smarter things to do but I don't want to go to details now.

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hello, i was trying to send a duna probe but i forgot to wait till kerbin and duna align. what should i do now?

Depends - where is the probe, can you fly it back home and refuel? :D

More seriously:

If you cannot get a reasonable encounter (with the fuel you have) with Duna, set a node and see if you can get an encounter with another planet to salvage the mission. Then go back and launch a new one at the proper time.

Mod suggestions:

Protractor (to get all angles and timings)

Kerbal Alarm Clock (to do something more useful in the meantime without forgetting about the probe)

Kerbal Engineer or VOID (for orbital information of active craft, like inclination and current ejection angle)

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Actually, this is *not* the way to go. It would mean speeding up to the speed Duna has, which means you have to spend *quite* a bit of fuel.

Actually, that's not quite the problem. The problem is that once you are in solar orbit your burn to get the Duna intercept will no longer gain the efficiency boost of the Oberth effect. The difference is very significant in this case. But if you have the fuel to spare then sure, you can just wait in solar orbit for an appropriate phase angle and then burn for Duna. It will certainly get you there.

Another option is to change your orbit very very slightly and then wait a long long, LONG time for another Kerbin encounter, then use Kerbin to slingshot you up to Duna (with a burn at periapsis).

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I have been to most worlds and moons in the game now and have never waited for an alignment. Wouldn't actually know what to look out for. I guess I just naturally over engineer things so I can launch, burn and then just play with the position and delta v of the maneuver node until I see an encounter pop up.

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If you're ship is in a Kerbin-like orbit, then it's just a matter of time, warp plot a lot of nodes until you get you're encounter.

If you started burning towards Duna and missed it, and now you have weird orbit... then, well, you can just wait, warp, and plot a lot of nodes :). But it's a pain in the ass and most of the time you're better off restarting the whole mission again.

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I have been to most worlds and moons in the game now and have never waited for an alignment. Wouldn't actually know what to look out for. I guess I just naturally over engineer things so I can launch, burn and then just play with the position and delta v of the maneuver node until I see an encounter pop up.

This works, but it usually costs more delta-V, getting progressively more as you get further out of phase from the ideal angle for a Hohmann transfer. This is even added to by the fact quite a few of our celestial bodies have no atmosphere, forcing you to cancel out more relative velocity.

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This works, but it usually costs more delta-V, getting progressively more as you get further out of phase from the ideal angle for a Hohmann transfer.

Not if you do it right. Especially if your destination has no atmosphere.

Hohman transfer (to higher orbit) means you first raise your apoapsis to the target orbit, then at apoapsis raise the periapsis. Once you raise the apoapsis to the target orbit, you get the closest approach markers in the map. Then you can phase raising your periapsis so you exactly intercept the target after the last raise. You use exactly the dv needed for Hohman transfer that way, not less not more.

Of course if the destination has atmosphere you lose some dv to get the intercept because otherwise you'd not need to raise the periapsis. But that's not about Hohman transfer anymore.

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Well yeah, I always try to keep the node as close to the periap as possible for that reason, but for the sake of a couple of hundred m/s on a craft with nine or ten thousand or more, it seems trivial.

I'm probably wrong.

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Not if you do it right. Especially if your destination has no atmosphere.

Hohman transfer (to higher orbit) means you first raise your apoapsis to the target orbit, then at apoapsis raise the periapsis. Once you raise the apoapsis to the target orbit, you get the closest approach markers in the map. Then you can phase raising your periapsis so you exactly intercept the target after the last raise. You use exactly the dv needed for Hohman transfer that way, not less not more.

Of course if the destination has atmosphere you lose some dv to get the intercept because otherwise you'd not need to raise the periapsis. But that's not about Hohman transfer anymore.

100% agree and this is why I don't usually wait for transfer windows. Anyway when chaining multiple gravity assists, waiting for a transfer window only helps with the first leg and for the second and subsequent ones you just have to take the planetary alignment as it comes.

Plus, if you're going to avoid spending fuel for the inclination change (for Eve, say) then you need to intercept at the AN/DN, which means if you're waiting for a transfer window you need a phase angle of Kerbin relative to Eve AND relative to the orbital node. You could be waiting a very long time. In this case, by ignoring planetary alignment you usually end up waiting less, and it costs only a tiny amount of additional fuel, by burning at the first pass of the node to adjust the orbital period such that you get an intercept after some number of orbits.

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im now in a mun g-assist escape trajectory, with roughly 1500 m/s dV left on stage (my third stage of the launcher is still there)

Actually, this is *not* the way to go. It would mean speeding up to the speed Duna has, which means you have to spend *quite* a bit of fuel. The best thing to do is fiddling around with maneuver nodes a bit and try to find the cheapest encounter.

Also.... I don't know how you would orbit the sun clockwise? Could you give me an example of how to achieve such an orbit? I can only think of building a big-ass rocket with nervas to cancel out all orbital velocity, but this would take a rocket with some 15000m/s delta v. Which is a lot.

im not doing a retrograde orbit.

He meant leaving Kerbin SoI retrograde, you will still orbit Kerbol prograde but at a reduced velocity (kerbin orbital velocity - your escape velocity, give or take).

I also feel you are better tweaking your trajectory to try and get yourself an encounter. If you've set duna as target then you should see the 'closest approach' and 'target postition at closest approach' markers, play with a node and see which way they slide, try and bring em together. If the markers are more or less opposite each other then you are really out of phase, your best bet for encounter then (barring a bunch of time-warp orbits) is probably a burn at your solar apoapsis and try for an encounter with duna on the opposite side of the system. This will be reeeaaallly expensive in fuel, hope you have a NERVA if this is the case.

im not doing retrograde orbit!!!!! i just didn't wait for the phasing angles

Edited by Specialist290
Merging sequential posts.
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Nothing stops you burning out until your orbits overlap, then sitting there waiting until there's a natural event in which the separation is quite minimal. Then make a node to fix it. I've done all my flights this way, it just involves less maths and confusion than waiting for phases.

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