General Question Sync orbit taking too long

[DanScall]

Wotcher,

OK, little odd one this I feel. I can Sync Orbit fine, but as I'm beginning to use more realistic craft such as the XR-5 I find it takes too long, the crew runs out of oxygen and everybody dies. Now, I think the problem is that when I first Align Planes and prepare to Sync, the required Dtmin change is retrograde, and will actually lower my PeA below the atmosphere, I therefore have to wait a very long time until the reguired Dtmin change is prograde. I think the problem could be that I am attempting to reach a retrograde station, is this correct?

 

[insanity]

Okay, create a point of intersection. All this means is find a place where your two orbital altitudes intercept with aligned planes. Sync MFD calls this Intersect 1 or something like that. Wait until you are almost there (watch the time until your craft reaches the intersect point on 0 orbits), then burn (prograde will do, unless you are close enough behind it that retrograde won't put you in the atmosphere and give you a reasonable intercept time). Keep burning until you have a reasonable transfer solution worked out.

 

[Shadow Addict]

Or you could just launch so the station is behind you instead of vice versa, then let it catch up to you. This requires a higher orbit than the station's so there's no way it'll intersect the atmosphere.

 

[Wolfer]

You can also create an intersection point, then wait. It might take a long time (a couple of days), but eventually, you'll have a reasonable DTmin.

 

[Urwumpe]

Retrograde station? Are you having 180° Rinc or do you mean you are above the space station in terms of semi-major axis?

 

[DanScall]

Cheers for the advice so far guys, creating an intersect point, as opposed to simply using the PeA as the intersect, didn't seem to help so I'm gonna try launching so that the station is behind me now.

Urwumpe, I mean the station is orbiting from right to left on the MapMFD, as opposed to the usual left to right of, for example, the ISS. I thought that was a "retrograde orbit"?

 

[Adelanthal]

DanScall, once you're in orbit, the direction of orbit doesn't matter except for how much dV you have left. Another option you might try is turning off Non-Spherical Gravity to get the basics and then, as you gain confidence, turn it back on. If the target is behind you, loft your orbit to 100-200 km above the target orbit. If the target is ahead of you, enter an orbit 100-200 km below the target, assuming that that orbit does not put you in the atmosphere. Wait until the last or second to last orbit before you overrun the target, align planes, and adjust your orbit to be roughly similar (>10-20 km difference in altitudes at maximum). Ensure that the majority of your orbit is on the proper side of the intersection (higher altitude if you're ahead of the target, lower otherwise). When you're within 5-10 km of the target, use final approach and docking procedures as normal. Hope this helps.

 

[Arrowstar]

I agree with the comment about using a higher apogee orbit and letting the station catch up. I routinely use this method with the XR-5 and it's never taken me more than 5-6 orbits to meet up with the station I'm after.

 

[Shadow Addict]

Yeah, I recall one of the early OFSS missions had the launch window set up to let the station catch up. It was just as easy as catching up to the station (though I do that normally).

 

[DanScall]

Thanks guys, I followed the "Raise your PeA" advice and RV'd perfectly in less that 8 orbits, cheers!

 

[Tommy]

If your mean (average) orbital altitude is lower than your target's, you will catch up to it. If your mean is above the target's, it will catch up with you.

Keep in mind that you can "catch up" faster if you leave both your Ap and Pe as low as possible - 200k works well. Then you can raise your Ap to meet your target when it's about 1/4 to 1/6 orbit ahead of you.