CAPITOL HILL: The war ground on today between San. John McCain, chairman of the Senate Armed Services Committee, and his colleague Sen. Richard Shelby on the Senate Appropriations defense subcommittee.

Shelby, knowing he had a policy friend in Air Force Secretary Deborah Lee James, asked her about the Russian-made RD-180 rocket engine essential to US satellite launches and “worried” that his colleagues might not completely understand the central Pentagon policy known as assured access to space.

James first sought to deflect the McCain onslaught she knew she would face: “I want to assure you we are moving as quickly as we can to eliminate the RD-180 engine.”

But James then went on to the meat of the Air Force position, which is that industry — however much we may not want to use Russian engines — just can’t build a complete launch system that comes anywhere matching the reliability of the United Launch Alliance’s RD-180-powered rockets by 2019, which is what Congress has said must happen.

“What’s critical is the total launch capability,” James told the Senate Appropriations defense subcommittee. “An engine is an important part, but we need a complete capability.”

James restated the position that the Air Force needs to use 18 RD-180 engines to ensure there is no “gap” between new systems being developed by ULA, SpaceX, Blue Origin and others. Elon Musk’s SpaceX has aggressively courted key lawmakers and the White House, arguing that his company should be given the chance to compete against ULA. Unfortunately, he hasn’t yet built and rigorously tested and successfully launched a rocket with enough power to lift the big satellites which ULA does such a reliable job of putting into orbit.

McCain reacted to Shelby and James’ comments this way on Twitter:

MYTH: #SECAF says Air Force needs continued access to #Russian rocket engines

Of course, Shelby and Sen. Richard Durbin inserted language into the December Omnibus Spending Bill giving the Air Force permission to use the RD-180s. McCain has cast all sorts of aspersions at the two for their action.

But there’s something of more lasting interest in the prepared statement James submitted to the SAC-D today.

For the first time in a generation, adversaries are boldly challenging Americas freedom of maneuver in contested regions and near our allies’ borders. The era in which the United States could project military power without challenge has ended.

In short, the technology and capability gaps between America and its adversaries are closing dangerously fast.