The United States militarys space program could see more than 30 missions delayed for an average of three and a half years each if Russia follows through with its threat to ban exports of the RD-180 rocket engines used for launching satellites, according to a Pentagon report obtained by SpaceNews. The Pentagon reportedly also found that, in a worst-case scenario, the delays may cost the US as much as $5 billion. The US needs to develop a domestic engineRussias Deputy Prime Minister said the ban would be going into place earlier this month, but SpaceNews reports that the government is yet to see signs that its been put in place. While that remains the case, the Pentagon suggests accelerating the pace at which RD-180s are purchased to increase the remaining US stock.