the Air Force and NASA should pursue joint development programs with interagency cooperation and commercial partnerships, particularly for liquid rocket engines, noting that neither agency can afford standalone programs.
Greg Rudderman (Air Force Research Laboratory; AFRL) presented charts generated by Richard Cohn (AFRL) who was not able to attend the workshop. This presentation started with a review of relevant research, past and present, by AFRL, including the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) program. IHPRPT is a joint DOD-NASA-industry program to develop technologies that will lead to more capable rockets. Military applications of interest include tactical missiles, strategic missiles, and spacecraft. The IHPRPT goals are similar in nature to many of the goals laid out in NASA’s draft roadmap for TA01. Propulsion Directorate is interested and actively working on both solid and liquid motor technologies as well as improved modeling while other parts of AFRL pursue air-breathing engine concepts. In reviewing the draft TA01 roadmap Cohn noted that it includes some technologies that have been shown in the past to lack promise and agreed that greater focus on a smaller number of promising technologies would be beneficial.
Randy Kendall (The Aerospace Corporation) said that modern launch options have plenty of performance and reliability, but are very expensive. He also stated that increased flight rates were key to reducing launch costs. He described current Air Force plans to build a reusable booster system and said that a combustion engine suitable for a reusable hydrocarbon stage would be the most promising NASA technology to support a reusable booster system. Over the mid- to long-term, he said that the highest priorities should be air-breathing propulsion technologies (RBCC and TBCC), pulse detonation engines, and an air collection and enrichment system.
Tim Lawrence (Air Force Institute of Technology) included comments on in-space propulsion and more advanced concepts. He suggested that nuclear-based propulsion technologies are good options for solving NASA’s transportation needs, but there are several challenges to be overcome before they can be implemented. He strongly encouraged development in the field of green propulsion technologies (that do not include hazardous materials) because they are compatible with small scale and student-run spacecraft. In addition, revolutionary advances in propulsion technology would enable missions that are currently inconceivable.
In the discussion period many speakers discussed how the U.S. Air Force and NASA should cooperate. It was noted that, although the two agencies are trying to cooperate, it is difficult to execute joint programs because of the potential for redirection by either participant. It was also mentioned that the nation may have too many underused test facilities because of overlap between the Air Force and NASA. One speaker said the Air Force launch rates would probably remain unchanged unless a revolutionary system is developed that leads to higher launch rates.
Session 3: Propulsion System Manufacturers
Stan Graves (ATK) started the session with propulsion system manufacturers by noting that current launch systems all use a combination of liquid and solid propulsion systems. He expects that trend to continue due to the physics, economics, and programmatics of the launch vehicle industry. Having reviewed the draft NASA roadmaps for TA01, he observed that many of the technologies would benefit both commercial and NASA heavy lift launch systems and both liquid and solid propulsion systems. He also suggested that two technologies, electrical-hydrostatic and electrical-mechanical thrust vector control, should be high priorities. Graves also asserted that investments should be made in developing a low-cost, safe, and green system.
Jeff Greason (XCOR) stated improving rocket performance is not likely to be a cost effective approach for NASA to improve the economics, reliability, and safety of access to space. Instead, he advocated increasing flight rates and reducing production costs. He declared that one of the best approaches for increasing flight rate is for commonality in performance requirements established by launch customers, and NASA could contribute to this approach by investing in technologies that allow large exploration missions to be broken into smaller pieces for launch. With a higher flight rate, reusable launch systems become more advantageous, especially if maximum payload mass per launch is contained. He identified two other high priorities: thermal protection systems for reusable launch vehicles and low-cost engines with adequate performance.
Russ Joyner (Pratt Whitney Rocketdyne) said that the current roadmaps are too broad and should be focused, but not before NASA establishes mission priorities. In the meantime, he urged NASA to invest in crosscutting technologies, such as manufacturing. He also called for technology investments to focus on reducing cost rather