Survey Contract Landing Target Keeps Moving

[qoonpooka]

:mad:

Here is the orbit I'm on, with the last target for a temperature survey contract showing. This is a Munar orbit:

I'm not getting messages, so I figure I need to burn my angle of inclination down to it. So I set up a maneuver node like so:

I burn that correction, note the dotted line DIRECTLY UNDER THE TARGET.

Except that, when I get there, the damned thing is the same distance away.

Mun is tidal locked, yeah? So it shouldn't be rotating away from me... I'm gonna run out of delta-v if I keep missing like this...

While I'm on the subject: Anyone got any good links to how to do a precision landing on a target like that, that /isn't/ mechjeb-assist or burn-to-zero right above it? The former because, if I wanted cheat codes I'd be playing a different game () and the latter because I've only got 1.6km/sec dV left, and I worry I won't be able to get home with those shenanigans - plus I have more flyover scanning to do, if I can afford it.

EDIT: Tidally locked doesn't mean it doesn't rotate out from under you... #TIL.

Edited January 14, 2015 by qoonpooka

[Alshain]

Tidally locked doesn't mean it doesn't rotate. It means it rotates a full rotation at the same speed that it takes to travel the distance around Kerbin. Earth's moon does this, that is why no matter when or where you are on the planet, you will always see the same side of the moon from Earth. It's rotating out from underneath you.

You might find it easier to land near by and then take off in the direction to close the distance on a suborbital hop.

Edited January 14, 2015 by Alshain

[wibou]

I add the same reaction at first... "Hey that damn target is moving!".

Then I realized... the moon is rotating so a stable orbit does not keep passing over the same point on the ground. As the moon rotate, the target rotate with it, but your orbit keep passing over the same point.

So this mean:

1- You need to adjust your trajectory as late as possible or to compensate for the rotation

2- You can just hit time-warp and wait, you WILL more or lss line up eventually (unless your are perpendicular), although it can take quite a long time.

[LethalDose]

Mun is tidal locked, yeah? So it shouldn't be rotating away from me... I'm gonna run out of delta-v if I keep missing like this...

"Tidally locked" doesn't mean "0 rotational speed"

Burn another correction so you're twice as far ahead of the marker as you did last time. OR wait until the moon makes another rotation.

As for precision landing, it's practice. Get a trajectory that will land past your target (even accounting for rotation), and then bend your trajectory (burn retrograde and a liiiiiitle bit radial) to land at your target.

[Slam_Jones]

Spent 10 minutes trying to figure out how to explain without pics.

Got ninja'd.

10/10 would post again

[LethalDose]

you WILL more or lss line up eventually (unless your are perpendicular), although it can take quite a long time.

Just a note: The only time you won't fly over a location is if your orbital inclination is less than the targets latitude or your orbital period is in some harmonic with the bodies rotational period (ratio of two small integers), but, as you pointed out it may take awhile.

Edited January 14, 2015 by LethalDose

[Yemo]

Intall the trajectory mod, which calculates rotation and atmospheric drag to provide you with an X.

[qoonpooka]

Awesome, thanks for the tip! Landed too far west, trying to walk my way there, but the delta-V budget is getting /tight/. Changing to Answered.

[Torquemadus]

To land at or overfly a specific target on the Mun, I go into polar orbit first. From polar orbit, I will gradually overfly every point on the Mun's surface as the Mun gradually turns underneath me.

Survey contracts that don't require a landing can be spammed from polar orbit.

[qoonpooka]

To land at or overfly a specific target on the Mun, I go into polar orbit first. From polar orbit, I will gradually overfly every point on the Mun's surface as the Mun gradually turns underneath me.

Survey contracts that don't require a landing can be spammed from polar orbit.

This was a manned mission, so I try to keep those durations plausible, and it included a plant-flag objective.

But yeah, I'm gonna park a satelite in a polar orbit for this reason.

[Kerba Fett]

If you've got to land on that point why do you care if your orbit goes over it?

Just use a maneuver node to set up your de-orbit burn and use both retrograde and anti-normal to put your predicted impact on your target.

You can land a long ways off your orbital path like that.