COLORADO SPRING: Message to Elon Musk of SpaceX: the head of Air Force Space Command is not really happy with you, and he personally supports development of a new rocket engine that would mean the United States did not have to depend on the Russians’ RD-180 rocket engine.

I asked Gen. Willie Shelton, who will retire August 15, at the National Space Symposium whether he was unhappy with SpaceX and the two lawsuits the company has filed. Shelton, a soft-spoken and very civil person, held himself back and said: “Generally, the person you are doing business with you don’t sue.” I followed up and asked how ticked off he was with Space X on scale of 1 to 10. He declined to answer. But he was clearly frustrated — at the least.

Shelton also reminded SpaceX that the Air Force is pouring $60 million and have put 100 people to work to see if they can certify Musk’s Falcon 9 rocket as safe and reliable enough to carry the “precious” and very expensive national security satellites into orbit.

Shelton, as did ULA’s Mike Gass yesterday, noted that the Russian government has not notified anyone in the US or in Russian industry that there is an embargo on sales. In classic Shelton style, he noted that there had been only “one Twitter from one official” from Russia about the supposed embargo. (We’ll send him a Tweet later today….) “I think it’s time to pause and just let things cool down,” the cool and collected general said.

“Russia is ready to continue deliveries of RD-180 engines to the US only under the guarantee that they won’t be used in the interests of the Pentagon,” Russia’s deputy prime minister Dmitry Rogozin said in a May 13 Tweet.

During the same press conference, Shelton told us that it is his “personal opinion” that the US should build a new rocket engine in part to bolster what he called a “withered” industrial base. Although the United Launch Alliance (ULA) has argued for years that they could co-produce the RD-180 engine, Shelton said that would cost about the same as developing a new engine. So how would Space Command pay for that new engine? Shelton made clear he can’t because his organization’s budget is already on the “ragged edge.” He said members of Congress had told him “not to worry” about finding money. They would take care of it.

All this centers, of course, on what is shaping up as one of the most exciting aerospace battles in years between the uber-corporate ULA, composed of both Lockheed Martin and Boeing, and feisty startup SpaceX, led by the loquacious Elon Musk.

SpaceX filed a protest against the EELV contract award — effectively against Space Command — in the Court of Federal Claims, one of three avenues for companies seeking redress through the filing of formal protests about contracts. Musk’s company also successfully sought an injunction to stop ULA from buying any more RD-180s and a U.S. Federal Claims Court judge issued a preliminary injunction against purchases of any more engines.