The U.S. Senate is debating the 2017 National Defense Authorization Act this week with the goal of passing the bill by the end of the week. One of the key provisions in the current draft of the bill is to limit the Department of Defense to purchasing only 9 more Russian RD-180 rocket engines. Those engines power the first stage of the Atlas V, the workhorse rocket used to launch critical national security satellites.

Sens. Cory Gardner and Bill Nelson have proposed an amendment that would provide relief from this restriction, recognizing that the current draft legislation would significantly harm the national security space program. The Senate Appropriations Committee appears to favor a similar loosening of the arbitrary Armed Services Committee restriction.

There is no question that long-term dependence on Russian engines is no longer acceptable. Current provocations, as well as recent aggressive behavior toward its neighbors, necessitate a review of all U.S. government relationships with Russian businesses. Memories are short in some circles, however, on how we got to this point in our space launch history.

After the fall of the Soviet Union in the late-1980s, the United States was concerned that talented rocket scientists in the former Soviet Union might be hired by potential adversaries. To preclude that possibility, the decision was taken to keep those engineers and scientists employed by using the RD-180 engine on the Atlas V rocket, and to eventually coproduce that engine in the U.S. As Russia proved to be a reliable supplier, and the much higher costs of co-production became clear, the Department of Defense elected to rely instead on direct procurement from Russia.

Another landmark decision by the U.S. government was to encourage the formation of United Launch Alliance, a joint venture of Lockheed Martin and Boeing. Expected commercial satellite launch contracts did not materialize in the 1990s, and there was insufficient launch demand to keep two independent companies in business. The Nation still required dependable and assured access to space as a crucial component of our national security, so ULA was created. Over 100 consecutive successful launches later, the wisdom of the ULA decision has been validated.

Over the past few years, however, several new companies have entered the space launch business. Most notable to date has been SpaceX, which was certified by the U.S. Air Force in May, 2015 to compete for national security space launch contracts. In fact, SpaceX was recently awarded a contract for such a launch in the future. Other companies likely will be certified in the coming years.

And the Air Force is actively pursuing a new rocket engine to replace the RD-180, but that new engine and the rocket matched to it will not be available for several years. Current Defense estimates are that 18 RD-180 engines will be needed to bridge the gap until new engines and new rockets are available. The restrictions in the current draft of the Senate authorization bill would result in the Department of Defense prematurely running out of engines for the Atlas V.

Clearly, this is a complex period of transition in the national security space launch business that requires judicious planning and decision-making. Due to the criticality of our satellites, long-standing National Space Policy has required two means of access to space, thereby ensuring space launch capability even in the event of a catastrophic failure of one rocket type. The Atlas V and the Delta IV have satisfied that requirement for many years. But if an arbitrary limit of 9 more RD-180 engines becomes law, once those 9 are expended, for the next several years only the SpaceX Falcon and the ULA Delta IV could compete for launch contracts.

The Delta IV is more expensive than the Atlas V, and the Falcon is cheaper than both. But SpaceX has yet to launch any national security satellites, and like all new launch vehicles in history, development problems have caused failures. A single failure of a national security launch would result in the loss of a satellite costing hundreds of millions of dollars, not to mention the loss of critical operational capability. Ensuring a solid transition that provides safe, reliable access to space should be the goal.

Over the last two years, the Senate Armed Services Committee's desire to punish Russia for its bad behavior has overcome consideration of the predictable and inevitable consequences to our own national security launch capability. An inconsistency that bears mentioning is the United States continuing to accept Russia as the sole means of access to the International Space Station until a new commercial crew program matures. The national security space launch program should have a similar pragmatic and rational approach rather than arbitrary restrictions based in anger.

Sens. Gardner and Nelson, as well as Sens. Shelby and Durbin, are courageously leading an effort to ensure the U.S. can continue to launch national security satellites with very high confidence as the launch industry transitions to a new era. The House version of the authorization act allows 18 more engines, so it appears only one congressional committee is out of step. Here's hoping a majority of our senators see the wisdom in turning the Armed Services Committee's proposal into a more constructive approach.

General (retired) William L. Shelton is the former commander of Air Force Space Command. Thinking of submitting an op-ed to the Washington Examiner? Be sure to read our guidelines on submissions.