The United States needs to buy Russian-built RD-180 rocket engines to avoid a domestic monopoly and ensure two independent and certified launch vehicles provide access to space - at least for the time being.

"The failure of [SpaceX'] Falcon 9 version 1.1 rocket should give everyone pause about jettisoning a dependable arrangement vital to US security," General William Shelton said, referring to the Atlas V and Delta IV rockets, which boast a 100-percent success rate.

Cause still unknown after several thousand engineering-hours of review. Now parsing data with a hex editor to recover final milliseconds. — Elon Musk (@elonmusk) 29 июня 2015

Both launch vehicles are produced by a joint venture of Lockheed Martin and Boeing, known as the United Launch Alliance (ULA). Atlas V is powered by reliable and relatively cheap Russian-produced RD-180 engines. The expensive Delta IV does not use them but it will go out of production in a few years.

#DidYouKnow ULA's #AtlasV 551 can deliver the equivalent of 2 school buses to orbit! pic.twitter.com/RCfNSKNcR1 — ULA (@ulalaunch) 17 июня 2015

The US Air Force wants to lower launch costs, meaning more companies have to enter the bidding process for the national security launch contracts, the commander of Air Force Space Command from January 2011 to August 2014 said.

SpaceX has done just that with its Falcon Heavy rocket, which has never been launched let alone certified. Nevertheless, the company successfully convinced US lawmakers to prohibit the use of the Russian-made engines for heavy lift rockets after 2019.

By that time, as the rationale went, the US will have produced its own rocket engine. The ULA announced it would design a new rocket and new engine in the necessary timeframe but there are considerable concerns that a replacement will not be ready in time.

When the ULA runs out of RD-180 engines and the Delta IV is phased out, Falcon Heavy will be the only means of access to space available to the US.

"The long-standing national space policy to ensure two means of access to space for national security satellites will be ended," General William Shelton pointed out in an article published by the Wall Street Journal.

This scenario spells trouble for US national security which relies on two independent launch systems to access space.