Space Exploration Technologies Corp. Chief Executive Elon Musk called out rival United Launch Alliance for its $1 billion in annual U.S. Air Force support funding, while ULA Chief Executive Michael Gass questioned SpaceX’s ability to launch the full slate of government missions at its advertised prices in a written exchange recently submitted to the U.S. Senate.

The two companies are locked in a heated battle not only for the U.S. government’s launch business but also for the hearts and minds of U.S. lawmakers, many of whom have complained about the current high cost of launching national security missions. As prime contractor on the Air Force’s Evolved Expendable Launch Vehicle program, ULA currently has a virtual monopoly on that business, but SpaceX is gearing up to give the incumbent a run for its money.

Musk and Gass appeared March 5 before the Senate Appropriations defense subcommittee to answer lawmakers’ questions and, in an unusual twist, were given the opportunity to submit written questions to one another and provide answers back to the panel. Neither side landed a knockout blow, but the exchange was illuminating nonetheless.

Musk zeroed in on the roughly $1 billion ULA receives annually in so-called EELV Launch Capability funding, challenging Gass to fold those costs into the price of individual missions. Gass got Musk to acknowledge that SpaceX currently is capable of handling only 60 percent of the Defense Department’s payloads and that government requirements tend to drive SpaceX prices higher than the company’s advertised rates. Each had questions about the reliability of the other’s rockets, even as both claimed a 100 percent launch success rate.

Both sets of questions and answers were made available to SpaceNews. To view the full exchange, please click on the links below: