At the beginning of 1970s I started the research and development of rocket turbopumps. Around the same time I knew Prof. Acosta’s paper which showed how to calculate the geometry of blade surface cavitating inducers of rocket pumps . I eagerly hoped to meet him. Fortunately, I could stay his laboratory for one year from 1975 as Visiting Associate. I remembered that the unsteady characteristics of rocket pump inducers and the liquid oxygen pump of the SSME alternate turbopump were investigated cooperation with Dr. Chris Brennen, who was Research Associate. My research at Caltech started with Acosta’s proposal, “consider why the cavitating inducer makes fluid systems unsteady.” I began to investigate the unsteady flow of the inducer using the visualization in our laboratory, which was obtained by a high speed camera. I printed each frame on photographic papers in the darkroom of the mechanical engineering. These pictures were arranged and Fig. 1 was produced. This Fig. 1 is the very beginning of rotating cavitation which is completely different from rotating stall. The paper of the rotating cavitation was published on AIAA journal in 1993 . 17 years passed since I had made (Fig. 1). I introduced the summary of my research of rotating cavitation in the symposium of Cavitation and Gas Liquid Flow in Fluid Machinery and Device which was held to celebrate Prof. Acosta’s retirement from Caltech. He was interested in my lecture and wrote his signature on the cover of the proceedings.
I attended several AIAA conferences like AIAA/ASME/SAE/ASEE Joint Propulsion Conference after 1976. In June 1992, before I attended the Joint Propulsion Conference at Nashville with my family, Prof. Acosta had sent me an E-mail in which the researchers of NASA Marshall Space Flight Center eagerly wanted to talk about the shaft vibration of SSME alternate liquid oxygen turbopump. I promised them to discuss the problem at the Space Museum near the Marshall Space Flight Center, because my wife and son can enjoy the history of the space projects in USA for a while when I carried out the meeting. Two hour’s drive by a rental car took us to the museum. The cause of the trouble was easily found. It was rotating cavitation. Prof. Acosta was satisfied with the result very much and invited us to Athenaeum at Caltech. We enjoyed a fancy dinner there with Prof. Acosta and Prof. Brennen and spent the night at the biggest room of the guest house. I will never forget the memories through life.
In June 1996, I attended the Joint Propulsion Conference at Orlando, Florida. After the conference I visited Prof. Acosta’s house with my wife, Sachie. Prof. Acosta took us from Seal Beach to Long Beach by his sailing boat. He had prepared lunch and we enjoyed pretty good sandwiches on the boat (Fig. 2).
Prof. Acosta had visited Japan several times by invitation of some organizations such as universities and conferences. (These invitations were described in Prof. Acosta’s blog by Prof. Akira Shima, Prof. Hideo Ohashi, Prof. Yoshinobu Tsujimoto, Dr. Takashi Shimura) I invited him to Sendai and Tohoku district four times. When Prof. Acosta visited Japan to attend the first international symposium on cavitation held at Tohoku University in March 1986, I invited him to the Kakuda Research Center of National Aerospace Laboratory ( JAXA Kakuda Research Center now) at the beginning of march, 1986. I showed him the LE-7 liquid oxygen turbopump of H-2 rocket and the picture of its cross-section. He told me that the structure of this turbopump was very simple and that simple is best. I gained huge confidence in our design from his opinion. In my house, he enjoyed the dinner which was made by Sachie. (Fig. 3).
Graduate students of my class in Tokoku University could also have a nice chat with him in my house at the winter of 2000. (Fig. 4).
J. Acosta has been a great senior and mentor for these 50 years with my
research activities. I had gracefully appreciated his heartily appropriate
advice and guidance and hope Professor Allan Acosta filled with peace, good
health and happiness.