In order to reach some sort of accommodation, a group pulled from NASA, Air Force, ARPA, ABMA, and the Office of the Department of Defense Research and Engineering formed under the Silverstein Committee in December. von Braun was skeptical of liquid hydrogen as an upper stage fuel, but the Committee convinced him that it was the way to go on future upper stage development. Once these changes had been made, NASA's booster project was now entirely free of any dependence on military developments. At that point any sort of upper stage was fair game, and "If these propellants are to be accepted for the difficult top-stage applications", the committee concluded, "there seem to be no valid engineering reasons for not accepting the use of high-energy propellants for the less difficult application to intermediate stages".