Squeezing the grapevine, looks like there’s an issue with the Russian-supplied RD-180 engine used in the Atlas V booster.

Talk is that there’s a “flight constraint” that’s cropped up with the Russian-developed powerhouse. The issue is being wrestled with by engineers to clear the problem. Meanwhile, what impact this condition will have on the Atlas launch manifest for the rest of the year remains unknown.

What is known is that a look downrange on the calendar shows the Atlas V is manifested to power several spacecraft into orbit, such as the Air Force’s nifty X-37B military space plane. That mission is slated for December, a flight that pushed the NASA Lunar Reconnaissance Orbiter — also to ride an Atlas 5 — into 2009.

Other spacecraft missions on the Atlas V launch books for the remaining months of this year: A Defense Meteorological Satellites Program (DMSP) satellite; a Wideband Global SATCOM spacecraft, formerly known as the Wideband Gapfiller Satellite; as well as a couple of National Reconnaissance Office (NRO) spacecraft launches.

How all this shakes out in lofting these satellites this year is definitely indefinite, at least for now.