The Air Force, recognizing the need to develop a follow-on to the Evolved Expendable Launch Vehicle rocket booster's upper-stage engine, is set to initiate a study on "cost effective, technically mature alternatives" to the EELV's engine within the next two months. The service informed Congress last summer that the EELV's upper-stage engine, known as the RL10, had reached its performance limit, and the service is now on the verge of launching a study to consider various alternatives to that motor...
