Even when it’s expected, the passing of a friend, colleague, mentor is never easy. When it’s your father, all the less so. But the kind words you have all shared here have been tremendous comfort to me and my family. They have helped us appreciate what we already knew – our father and grandfather was a very special person. It’s nearly impossible to reflect on a lifetime of memories in a short space. I beg your indulgence with a long piece.

For an average kid growing up in suburban LA, we had far from an average life. Back then, it was hard to get here from India, England, China, South Africa, Germany, Japan, and Ireland. The visitors that graced our house from these and more places granted me a small degree of childhood prestige with my friends. Mom and Dad’s affection for his colleagues and students gave us great exposure to the broader world. Many of them, like Uncle Rolf (Sabersky), are no longer with us and like Dad live on in our hearts.

You enriched our lives from my earliest recollections. Good meals, wine and heated discussions were a staple in our home.  Dad adored spicy condiments which always graced our table, frequently gifts from colleagues. He had a near-competitive addiction to hot chilis of all kinds. Once, a Korean chef once refused to prepare his order, fearing Dad couldn’t handle it. The milder dish he was served was the hottest he ever ate.  

As in some of your stories, Dad encouraged me, scolded me (usually with due cause), always pushed me, and never held me back. Except once when I was about 10 he refused to let me ride the motorcycle one student had driven to the house.  (Dating was an entirely different matter.)

Before the sailboats we camped and hiked. Dad shared his love of walking with me.  Vigorously. No dilly dallying – walks are serious business and pity the person who couldn’t keep up with those long legs. With Dad’s coaching, I could name most native California tree species along with many flowers.

He was demanding.  But this stern man was also forgiving – after a terrible performance at a violin competition he gave me the perfect fatherly encouragement, and after several attempts at picking a career path he provided wise and loving counsel despite his personal vexation at my circuitous college career.

He was a loving grandfather to my 3 kids, giving them all special, cherished memories. He was a great story teller, they refused to go to sleep without one when we stayed with them. Years earlier, he composed a serial tale of Esmerelda, a princess who lived in the Icy Mountains, that entertained us as young kids during the long drives that summer we camped through Europe. Later that year when he read us The Hobbit, I couldn’t believe the remarkable resemblance many of the characters had.

Dad also passed along his love of music, he had an amazing collection of recordings and loved playing his flute. He enjoyed the challenge of playing with many of you, and just a few years ago Dad, his brother Ed, Ed’s wife, and I gathered in Seal Beach to play quartets.

Then there were the sailboats. What halcyon days! The first was a Cal-20 named Release after the USS Release. Although Mom eschewed Dad’s competitive racing bug, they both loved cruising. The 20 foot boat quickly became too small and was replaced by the Santana 27.

Like most dads he taught me to ride a bike and drive a car. But he also taught me how to row a dingy, hoist a jib, reef a main, chart a course, sail through squalls, and swim through kelp without getting tangled up.

Dad and I hiked all over Catalina. Before the Nature Conservancy took over, buffalo roamed the entire island. Once we came face to face with a massive bull, but Dad calmly had us quietly back up before beating a hasty retreat. I rowed the dingy while he dove for abalone and sea urchins. Once, perhaps stoking my rebellious streak, he put his out of season abalone catch in a gunny sack and told me to throw it overboard if Fish and Game approached.

But I never imagined Dulcibella. Building her was in many ways one of Dad’s biggest projects. 4 years of his and Mom’s hard work just to launch, were followed by nearly 40 more years of pleasure which included living aboard, cruising, and just sitting at the dock.

Reflecting on Dad’s career and accomplishments I find I didn’t ask enough probing questions. To me he was Dad, the one who gave me a passion for hard work, loyalty, dedication, music, and the outdoors. I never did understand the joy in his eyes when he told me calculus would unlock the mysteries of the world. But in adulthood I found the gift of appreciation of the significance of his work and his worldview of science. A few years ago my husband asked Dad what the biggest scientific breakthrough of his lifetime was. Without any hesitation he answered the transistor – because it made everything possible.

For me, your stories combine fond memories with details of his contributions to engineering. They confirm a life well-lived.  He is now in peace, but he did not go gentle into that good night – his ideas and spirit live on. Of all his interests and passions, one of his greatest joys was the deep and enduring friendships with his students and colleagues.

Sail on Dad.

Re: Allan Acosta

Hello everyone:

Like all of you, I was saddened to learn of Allan’s death.  He taught me a great deal, probably much more than he realized, about research, fluid mechanics, writing, and thinking, all of it informally.  He was also kind, for he let me explore a topic neither of us knew anything about, namely, non-Newtonian fluid mechanics.  All of his guidance came to the fore when I wrote a manuscript based on my PhD research.  It was a good paper, as it turned out, and he helped with the writing, but he thought that his name did not belong on the manuscript, saying that the work was all mine. I explained how much I had learned from him, as indicated above, and how much he had contributed to the paper in that way.  Happily, his name is there.  

It was part of the academic culture in those days — the sixties —  that I had to persuade my adviser to be a co-author. 

David James

Re: Allan Acosta

It was a shock to hear of the passing of Allan; my friend, teacher and collaborator. While he had been ailing recently his passing leaves a deep sadness and it signifies the end of a very special era in my life. I met Allan on campus in 1960 when I arrived at Caltech as a foreign graduate student. He became my doctorate supervisor that year and that began a lifetime of camaraderie and friendship. Allan was unique in that he was able to slip transparently between being a teacher, a mentor and a friend thereby bridging the full spectrum of a close and enduring relationship. So many memories come to mind of this whether it was taking his classes, working with him in the lab, discussing some technical problem, critiquing my doctoral thesis, sailing or spending time with our families at his home in Altadena. He was always there to provide guidance, support and genuine personal interest. With great fondness, he always reminded me that I was his first doctoral student. I spent a couple of years after graduating as a Research Fellow working with him on several Navy and NASA contracts working in the Hydrodynamics laboratory in Guggenheim. We would spend many hours together on these programs but always go sailing on Wednesday afternoons in the “Wet Wednesday” racing series or race in some other regatta. Anchoring off Catalina on weekends to go scuba diving or fishing for abalone was another of his favorite past-times. 

Such life time recollections can never be replaced and will always be with me as i think of Allen. He changed my life and many others. To all his former students and colleagues and especially to his children Alison and Joey, who spent so much time with our family, and to Annette, our sincere condolences. We all will miss him!

Richard Wade

Re: Allan Acosta

Dear all,

I would like to join you mourning for Allan’s death. To me the new is inspiring deep sadness but also a feeling of serenity, as his has been a life of great accomplishments and recognitions by those who most closely knew him. Meeting Allan at Caltech 40 years ago when he became my supervisor was a very fortunate step in my life, since I ended up working with both a great teacher and a master of life. He has been a very special person to me for his enthusiasm and imagination and for his ability to motivate and direct a group that led research in his field worldwide for more than a generation. Allan always exercised the necessary leadership with wisdom, generosity, consideration and respect for the his younger collaborators. I owe him the “can do” attitude and the notion that “If everything seemed under control, you are just not going fast enough”, which hopefully inspired my later academic career. He once said that his objective in life was “trying to make things better”, the distinctive feature of a true gentleman. He fully succeeded. In retrospective, I was very happy and honored to realize that, while working with him, we had become friends, a friend I will never forget.


Luca d’Agostino

Re: Allan Acosta

Dear everybody

I am deeply sorry to hear Professor Allan Acosta’s passing away.  May he rest in peace.

I started the research of rocket pumps according to Allan Acosta’s proposal at Caltech in 1975.

I had gracefully appreciated his heartily appropriate advice and guidance in both USA and Japan.

He has been also my great senior and mentor for these 50 years.

Please convey my sincere condolences to his family.

Kenjiro Kamijo

Re: Allan Acosta

Hi All:

I concur with everything everyone has said about Al.  He was a great educator, mentor, friend and gentleman.  I had the pleasure and honor not only to have studied under him but worked closely along side him for more than a decade when he was consulting with the company where I was employed. He definitely had a positive influence on me and the other engineers who had the privilege of interfacing with him.  My wife and I have many fond  memories of having Pat and Al over to our home for social functions.  He will be sadly missed but not forgotten.

All the best,

Khoon Ooi

Kean Khoon Ooi

To Allan my mentor and friend

I joined Caltech in 1986. Having just landed from a flight from France, I recall the unsettling feeling of finding my marks in a place and city I had never been to. Just a day after I arrived Allan called me into his office, introducing himself with a warm smile and such a laid back open attitude that I instantly knew this was a man I could count on whenever I needed help. My PhD journey at Caltech would be ok… little did I know that Allan’s watchful presence would extend much beyond my PhD.

As a good mentor Allan knew when pushing for excellence was needed. During my first year of discovering the good side of Californian life I vividly recall being called to his office one day to be told “I did not bring you all the way from France for you to get a B in that electronics class”, and a small voice in my head telling me “I did not move all the way from France to be reprimanded by that professor”. My respect for Allan and the fatherly authority which emanated from him was enough to ensure that this single short burst of reprimand was the only recalibration that was ever needed towards the successful completion of my studies.

Allan of course had a passion for sea and sailing that pushed him to commute day after day 50 miles each way at very odd hours through the hellish LA traffic. It did take a few years for him to assess that I was far enough on my way to success, to finally ask me to go sailing with him to Catalina together with my girlfriend (now my wife Anh). I recall the first time I stepped on his boat asking basic questions about rigging and sensing the pride he had in explaining the some of the intricate details of the workmanship and construction process which took him many years to complete. What a fantastic demonstration of following through one’s dream! While mooring in Catalina Island’s Emerald bay sharing and tasting whiskeys, Allan related the story of what led him to build this boat and his long life dream to sail it around the world. Flashing a book with worn out pages one sees on manuscripts read and re-read hundreds of times, he narrated the story of this young man from Britany, France who had preceded him in the sixties: building that exact model boat while living in a camper car, and then setting off to worldwide adventures making friends and discovering different cultures. This book guided him, and is a great reflection of his never-ending eagerness to make meaningful friendships everywhere he went (even if his sailboat hardly ever sailed beyond Catalina). I thereafter sometimes wondered if my own Britany origins and love for sea played a part in my being selected to study at Caltech! For sure him bringing me to California had a defining impact on my life… I owe him, and Chris Brennen big time.

Through the years following my PhD there were several opportunities for us to catch up again, witnessing him being honored on multiple occasions, the pain of losing Pat, the joy of finding Annette, and whenever practical squeezing in a sailing trip to Catalina… Every time I travel through or set foot in LA I am instantly reminded of the nearby presence of my Californian father. Allan has taught me how to balance friendship and work, to follow one’s dreams with the hard realities of responsibilities that comes with being a family man. He was curious about everything, down to microdetailed technical understanding. Every time I would update him about a facet of my job he would never be contempt with the superficial and stubbornly drilled deeper until he would either run out of questions but mainly run me out of answers.

This morning, as I stand dumbfounded about the news of his passing away, I cannot help but to be profoundly sad… and happy knowing we will one day meet again and set off sailing amongst the breezy white clouds of eternity.

Yan Kuhn de Chizelle – May 2020

Re: Allan Acosta

Hi everyone,  I was informed by Annette that Allan was not doing well a week ago but it is a great shock to hear that he passed away yesterday.   Professor Allan Acosta educated, advised and supported me since I came to Caltech in 1968.  Without this I could never survive here, and I can’t find any other words now than to say I thank you,  rest in peace, Professor Allan Acosta.   


Okitsugu Furuya

A Tribute to Allan Acosta: My Advisor, Mentor, and Friend!

How many people can say they’ve known someone for over half a century? That’s how long I’ve known Allan—and what fond memories I have!

I came to Caltech in 1967 and chose Allan as my advisor, for which I feel extremely fortunate and forever grateful.  I vividly remember my first “encounter” with him, which formed my lasting impression about him: a tall lanky fellow with a handsome tanned look who was very kind to the fledgling intellectual toddler that I was.  I was minimally prepared academically – a confused twenty-something lad from Korea, which at the time was better known as a poverty-stricken third world country still reeling and barely recovering from the total destruction of the war.  I needed to assimilate to an entirely new world. I had a lot to catch up with the Caltech way of learning – like drinking from the fire hose, figuratively speaking. Allan was generous enough to take me under his wing.  He was patient and understanding while I wrestled to adjust to the new academic environment. 

I quickly discovered one of Allan’s great talents – he seemed to know how to get to the heart of complicated matters without beating the bushes.  I once tried to write a FORTRAN program to solve a problem on a mainframe computer and discussed it with him.  He did not seem amused at my approach although he did not disapprove it.  A couple of days later, he showed me how he did it on a pocket calculator (the pocket calculator had just come out in the mid-1960s) using an iteration.  I was duly impressed by his simple way. Allan was often able to simplify seeming complexities to a manageable level.  I eventually settled down working on my thesis, which was about the unsteady cavity in internal flows.  It was an analytical study of a two-dimensional supercavitating flow past a flat plate at a small angle of attack with heaving and pitching motion of small amplitudes in a choked tunnel and another study on a finite cavity flow over a wedge in the middle of a tunnel with a mass oscillation.  After graduation, Allan introduced me to cavitation problems in turbomachinery.  He explained how the positive feedback of an unsteady cavity flow into the inducer pump of a liquid propellant rocket engine could lead to a thrust oscillation resulting in the so-called POGO instability.  He also explained how a fluctuating cavity flow could cause a surge in a closed hydraulic loop.  What little knowledge I learned in BC (before Caltech) was mostly through classroom lectures based on standard textbooks, so all these things were a fascinating revelation to me.  Allan guided me to extend my earlier studies to this new problem, first to a tunnel flow and then to cavitating turbopumps.

Allan was gentle and sensitive and showed personal interests in our conversations, technical or nontechnical, always giving his full attention to our talks.  Once I told him I was planning to visit Yosemite and his eyes lighted up. He suggested many things I could see and do there – I remember him describing the loveliness of the Tuolumne Meadow —   Another time, he said he knew too many things about airplanes that could go wrong so he would drink and quickly fall asleep whenever he flew!  He had commuted from Seal Beach to Pasadena until his retirement, and he said he would stay in a safe lane on the freeway and not change it unless absolutely necessary — a good safety lesson for me.

We once had an interesting discourse about my courses.  Allan suggested that I take an economics course, so I asked him in mild protest, “Why economics for an engineer?” He said, “Because you asked the question, that’s why!”  His response settled the issue, and I am so glad that I took his advice as it broadened my horizon, although it has not made me a billionaire (yet!).  I was also advised to take a full academic year of a graduate course in quantum mechanics in the Physics Department.  As an ME student taking a QM course, I struggled a bit but am proud that I added the two diametrically dissimilar disciplines to my repertoire, one known as dismal and the other abysmal.  The odd combination has occasionally given me an edge via an interesting perspective that my colleagues did not seem to fathom. 

After I left Caltech, I still maintained contact with Allan, albeit sparsely, as I transitioned from the cavitation area a few years afterward into nuclear energy.  I was aware of his activities in cavitation-induced turbo pump structural instabilities. When I organized the Korea-USA Fluids Engineering Seminar sponsored by the US NSF, I jumped at the opportunity to invite Allan to Korea. He presented a nice opening talk “Impeller-Induced Rotor-Dynamic Forces”, which he fondly called ABC paper (co-authored by Acosta, Brennen, Caughey). This appeared as the lead article in the proceedings.   We also met at a couple of ISROMAC conferences in Honolulu. In particular, he was honored to receive an ISROMAC Award at ISROMAC-4 conference in 1992.  He seemed happy and wistful to be back in Hawaii, which he had visited such a long time before in his Navy days. I remember him reminiscing about Waikiki, tall thin palm trees, and the historic Moana Hotel building still standing on the Waikiki Beach. My youngest daughter Janice accompanied my wife Jungsuh and me on a couple of these Hawaii trips, and although she was just a young teenager at the time, she remembers Allan to this day—his presence was large and his personality memorable to her.

Allan was a trailblazer. He used to say it was important to look for new areas and problems and, true to his form, he would open up new areas and move on.  As a young man who was intent on solving problems rather than finding new ones, I did not understand at that time his fixation on seeking new problems but later fully appreciated it, especially as a project manager at EPRI (Electric Power Research Institute in Palo Alto) and later as an academic person myself.

Jungsuh and I visited him many years after we left Caltech and finally enjoyed the privilege of seeing his famous boathouse.  He told us how he sailed in it to Baja, and I thought it must have been dangerous!  We were so pleased to see him again in the summer of 2018 but the boathouse was no longer.  He even put his old house up for sale, preparing to move to Encinitas.  He seemed reflective and pensive about leaving the place he had lived for nearly 50 years and having to clean up all the memorabilia. He was emotional about having to dispose all the research related materials including the dissertations of his former students and the publications he wrote with them that he had kept all those years.

There is a saying in Korea: “If strangers’ sleeves so much as touch each other, it makes a relationship.” My humble interpretation is that we are all interrelated and even such a chance encounter is a blessing although we may not realize it in the initial moment.  I have had so much more than merely touching Allan’s sleeves – I feel I am a most blessed man as I learned directly from him for over half a century and find myself still learning from him every day.

It has been said that one’s character, more than anything else, defines a person.  For all my admiration for Allan’s brilliance and numerous achievements, I personally value his character the most: his charm, kindness, sensibility, integrity, and love of wine!  Allan does not use big words nor does he have an oversize ego.  I never heard him boast or exaggerate – that is not his style.  Rather he has a keen sense and tender heart that eases and encourages those around him. This is the art of his fine character, and I am still trying to learn it.

Over half a century is a long time. I have accumulated my share of wonderful memories about Allan and wish to continue making more.  I owe him so much but don’t know how to repay all the care and kindness I received from him, so I will sum it up in these simple words: Allan, I wish you good health and many blessings.

With deep gratitude and best wishes, 

Jong H. Kim

Sent from Korea in October 2019

My Great Senior and Mentor for my Research Activities

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 [1]. 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 [2]. 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).

Professor Allan 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.

Kenjiro Kamijo
Prof. Emeritus Tohoku University

(1) Stripling, L. B.& Acosta, A. J., “Cavitation in Turbopumps,” Trans. ASME Journal of Fluid Engineering, Vol.84 (1962)
(2) Kamijo, K., “Hydraulic and Mechanical Performance of LE-7 Liquid Oxygen Pump Inducer,” AIAA Journal of Propulsions and Power, 9-6 (1993)

Visit to Sendai, Japan in 1986

I have received the itinerary and the official report of Allan’s visit to Japan in 1986, as well as many pictures, from Prof. Akira Shima of Tohoku University, Institute of High Speed Mechanics at that time and Institute of Fluid Science now, through Prof. Yuka Iga. The reports are available from:  [Itinerary] [Report]. Prof. Shima stayed with Allan long time before and arranged the visit. He is happy that he was appointed as a Fellow of ASME, recommended by Allan.

The documents remind me of the emergency phone call from Prof. Ohashi, on March 23, 1986. Allan’s flight JL61, scheduled to land at Narita, was diverted to Osaka because of heavy snow at Narita. All roads to Narita were closed. Prof. Ohashi was concerned that Allan could be kidnapped in the cabin till Narita is reopened and asked me to rescue him at Osaka. We were happy to welcome him as the first guest to our new apartment. He traveled to Tokyo by Shinkansen on the next day and could fit into the original schedule.   

Another memory is associated with his invited talk at the Cavitation Symposium. To show the cavity inception in the laminar separation bubble, he planned to use a high-speed film. However, the meeting site did not like him to use their movie projector:they were afraid of film jamming. Since the film was the key of his talk, we negotiated with the site saying that we will take all the responsibility in case of jamming, although we were not sure how we could. His talk was perfect: it proved that “take responsibility” is a key phrase in Japan.

The latter part of the report was written by Allan himself and I now learned from it that motivation and preparedness is very important for us engineers and researchers. He found that engineers in Japan are requested to be a specialist not only in a field but sometimes requested to lead a group in another quite different field. He argues that this might be very stressful not only for the engineers but also for their managements.  The flexibility he found might be a strong point of Japanese engineers and we might need to cultivate it also in the future.

Thank you Allan, for your careful observations and warm suggestions!!

Yoshi, based on material from Prof. Akira Shima, September, 2019

To 95 from 88

August, 2019

Dear Allan、

I had heard a lot about you from your former student, Dr. Oki Furuya, before I first met you in 1981. What a respect- and lovable educator you are! My admire to you was implanted prior to the visit by Oki, one of the undergraduate students whom I taught at Mechanical Engineering Department of the University of Tokyo around 1965.

You and I enjoyed sharing the same research interests in dynamic fluid forces on oscillating pump impellers in 1980s and early 90s. However, researches in CalTec and in UTokyo started quite independently; yours triggered by vibration trouble of turbopumps of Space Shuttle main engine, ours by that of high speed boiler feed pumps for supercritical thermal power plants. I was not aware of your research until Dr. T. Iino, Mechanical Engineering Research Laboratory of Hitachi, told me what he saw after he returned from NASA Workshop on Rotordynamic Instability Problems in High Performance Turbomachinery held at Texas A&M Uni. in 1980. Thanks to his introduction of our research at the workshop, we got invitation to submit a paper belatedly to the Conference Publication of the Workshop, NASA CP 2133.

We started theoretical and experimental study of lateral fluid forces on whirling centrifugal impellers around 1978 with close cooperation with Hitachi. Dr. H. Shoji of our group worked intensively on theory and completed his first contribution in 1979. We sent this paper to NASA and could join the Workshop on publication.

We completed our test rig for forced whirling motion in 1980 and continued experiments for 10 years with stepwise improvement of methods and devices. The first report on experiment was presented at ASME Winter Annual Meeting of 1981 at Washington, DC. On the way back home, I stopped over in Pasadena and met you at your office (photo below).

In 1990 we reformed the rig to forced precession motion, and continued experiment of force and moment on tilting impeller till my retirement in 1992. When I retired from UTokyo, I could not find successor of the research in my laboratory. Prof. Yoshi Tsujimoto of Osaka University, one of right-hand men supporting your research, appeared then as a Savior. He kindly offered to continue our research at his laboratory. The property registration of the whole test rig and accessories were officially transferred and moved to Osaka University. I am very glad and happy that Yoshi had produced a lot of contributions using the rig till his retirement in 2013. I hear also the test rig is still alive and active today under the new successor, Prof. K. Sugiyama.

 The test rig is now 40 years old. Its basic structure remains unchanged but measuring methods and devices have been continuously improved and renewed. The test rig is surely worth receiving Achievement Award for long years of service!

 Two researches at CalTec and UTokyo on fluid forces on oscillating impellers started independently, but got together finally by merge and acquisition by Yoshi. It is quite a happy end!

 Allan, I have many reasons to thank you. First of all, you raised many students from Japan to potential researchers and engineers, Oki is of course one of them. You were also a valuable mentor to numerous visitors from Japan, from academia as well as from industries, and gave them strong influences and incentives. Yoshi has been a good mediator to connect them to you. The conferment you received with the Order of the Rising Sun, Gold Rays with Neck Ribbon in 2012 was a big joy for all Acosta fans in Japan.

 You have been showing a beautiful example of sincere way of life as an educator, scientist and engineer, last but not least, as a human . We all Acosta fans are praying for your continuing wellbeing. Please show us good example of longevity for years to come!

With heartfelt regards,


Hideo Ohashi

Prof. Emeritus, University of Tokyo (88 years old)

Office looked like a showcase of impellers.

Held at Hyatt Regency Hotel, Shinjuku, Tokyo.

My Allan

Allan is my most influential mentor and set my research style after my stay with him in 1983(Oct)-1984(June), as a visiting associate. On the day of my arrival, he said that I might go to Santa Monica beach everyday if I wished, but if not I might work on a topic of rotordynamics. I knew that this interesting problem was studied also by Prof. Ohashi of University of Tokyo and, to tell the truth, I did not want to be his competitor. By comparing their treatments, I found that more fundamental approach was used at Caltech and I decided to extend it for realistic cases. After developing fundamental equations, I proposed Allan to carry out calculations after returning to Japan and spent the latter half of the stay studying cavitation under Allan’s guidance.

Although the results of calculation could simulate the experimental results qualitatively (convenient word!!), the magnitude was smaller than the experimental results. Instead of being disappointed, Allan kindly built and tested a 2D impeller which is assumed in the theoretical model and showed that the theory can simulate the magnitude as well!!  It was eventually found that the elementary flow fields developed for the rotordynamic problem could be conveniently used also for the analyses of rotating stalls in centrifugal impeller, vaned and vaneless diffusers.

Just after my return to Japan, Allan visited Japan to attend the first Cavitation Symposium at Sendai. Although I was not involved in cavitation at that time, he advised me to attend the symposium since I would be involved in the field. Before the Symposium he visited many universities and institutes and reported me about his impression. Perhaps on another visit to Japan, he was interested in visiting Matsue, on the other side of Hiroshima, which is not very familiar to foreign tourists. We drove there from Osaka and visited many marinas and small fishing villages as well. On the trip and other occasions with him, I learned from Allan about important attitudes for a researcher such as “make problems as simple as possible”, “nothing is more practical than a simple theory (said by someone else?)”, ”keep good balance between theory and experiment”. I tried to get closer to them throughout my life.

Allan developed a linear partial cavity model on a flat hydrofoil [1] and has shown that the cavity length is a function of a parameter (cavitation number)/(incidence angle). It was found that this parameter is important also for the occurrence of various types of cavitation instabilities. He also made the first detailed experimental study of cavitating inducer [2]. He reported about cavitation instabilities such as cavitation surge, alternate blade cavitation, and rotating cavitation. They are found also in modern turbopump inducers and extensive efforts are being made to avoid them.

Although my stay was only 10 months, he introduced me to many students who graduated before and after my stay, on my later visits. I feel very relaxed whenever I find Acosta family member in in various meetings all over the world. It is interesting that the stay with Allan gave me opportunities of getting familiar with Japanese important people, who are very busy and would have no time to talk with me in Japan. The first is Prof. Ohashi. He gave me his rotordanamic test facility on his retirement!! This is still working at Osaka University. The second is Dr. Kamijo, Dr. Yamada, and Dr. Shimura from National Space Laboratory, who introduced me to the interesting field of cavitation instabilities in turbopumps for rocket engines. In solving the problem, Allan’s theoretical and experimental works including those mentioned in the last section were very helpful. So, they invited Allan many times to obtain his suggestions. We collaborated with Dr. Furuya, a student of Allan, for the fundamental study of unsteady cavity response to disturbances.

Thus, I actually got deeply involved in cavitation as Allan predicted at the first Cavitation Symposium.

I am always asking myself how Allan would think, whenever I encounter new problems. I am now wearing the T-shirts and listening to the music both from Allan. So, Allan is always with me and I wish his quick recovery.


[1] A. J. Acosta, (1955) “A Note on Partial Cavitation of Flat Plate Hydrofoils”, California Institute of Technology Hydrodynamic Laboratory Report No. E-19.9.

[2] Acosta, A.J., (1958). An Experimental Study of Cavitating Inducers. Second Symposium on Naval Hydrodynamics, Hydrodynamoc Noise, Cavity Flow. August 25-29, Washington D.C., ACR-38, 533-557.

Tomoko, Annette, Allan, and Oki
July 17, 2016, at Oki’s home in Pasadena, on my last visit

Yoshi Tsujimoto, August, 2019

Long Time Friendship between Professor Acosta and JAXA Friends (A friend of Allan since 1983, Takashi Shimura)

Friendship between professor Acosta and friends of Japan Aerospace Exploration Agency (JAXA) started in 1970s. I would like to introduce our relationship a little bit. Professor Acosta accepted Dr. Kamijo of JAXA (later professor of Tohoku university) as a visiting scholar. It was the early stage of research and development of Japanese liquid rocket engine turbopumps. Research of rocket engine turbopumps has been carried out mainly at Kakuda Space Center of JAXA. The next visiting scholar was Dr. Yamada. The following picture was taken in 1982 at Caltech when I visited Caltech with my family during the stay of Dr. Yamada.

Professor Acosta kindly treated us lunch. As I took this picture, I was absent in the picture. My wife Makiko and my three years old son Munetaka joined with professor Acosta, professor Brennen and Dr. Yamada.

This picture was taken in the laboratory of professor Acosta. I was interested in the dynamic response of rocket engine turbomachinery.

After our visit to professor Acosta at Caltech, he visited Japan sometimes. When he visited Japan, professor Kamijo and I welcomed him playing the music instruments. Professor Acosta is a good player of the flute. The next picture was taken at the home of professor Kamijo.

Professor Acosta play the flute with the guitar of professor Kamijo and I. I think this picture shows Japanese spirit of entertainment, Omotenashi.

In 1986, a party to celebrate retirement of professor Murai from Tohoku university was held.

Professor Kamijo took this picture. Therefore, he is missing. Professor Acosta, professor Murai, professor Shima and his wife, Professor Kamijo and his wife, my wife and I joined together.

The next picture shows one scene of this party. Professor Kamijo and I played the guitar. I also played the bamboo flute.

In 1995, we have a chance to stay at a hotel in the Zao mountains, Zao Mets. The next picture shows the member gathered.

This picture was taken in front of the Zao Mets. Professor Acosta, professor Shima and his wife, professor Kamijo and his wife, my wife and I joined together.

I played the guitar with the flute of professor Acosta at the Zao Mets.

We had a concert at the lobby of the Zao Mets. Professor Acosta played the flute accompanied by my wife.

In 2011, AJK conference was held in Hamamatsu Japan. It was held soon after the gigantic earthquake attacked Tohoku district of Japan. Next picture was taken at a amall party during the conference joined by professor Acosta and JAXA people.

I was sitting to the right of professor Acosta. Professor Hirata and professor Uchiumi were sitting to the left of professor Acosta. I remember one thing. Professor Acosta was interested in the small ceramic ware which is used to rest chap sticks on. Therefore, I asked the shop manager if it is possible to buy the small ceramic ware for professor Acosta. Kindly, the shop manager presented it to him.

Just after the AJK conference in Hamamatsu, professor Acosta visited Tohoku district seriously damaged by the gigantic earthquake. He prayed to repose the souls of more than 18 thousand people died in the disaster. He is always anxious about us. The next picture was taken at that time in the area of Kakuda Space Center of JAXA.

Dr. Yamada showed professor Acosta around Kakuda Space Center. Professor Tsujimoto accompanied with them.

JAXA people are very grateful for the cooperation with professor Acosta. To express our gratitude, JAXA recommended professor Acosta as a candidate for the decoration of Japanese government. Dr. Yamada and I prepared for the application form of recommendation with the strong help of professor Tsujimoto. Fortunately, of course as a natural consequence, the application was accepted, and professor Acosta received the prestigious award at the Los Angeles Japanese Consulate in 2012. The next picture was taken at the ceremony held there.

The next picture shows the good luck flag we wrote to celebrate his achievement and to express our sincere gratitude.

Thank you very much again professor Acosta,

The former director of Kakuda Space Center

Takashi Shimura

For Allan James Acosta – A Heartfelt Tribute

I was incredibly fortunate to have enjoyed Allan Acosta as a teacher, a friend, and as a mentor.  When I was a young post-doc back in 1969, I was lucky enough to be assigned an office in the von Karman building next to an office occupied by Allan. From the start our interests and personalities drew us naturally together and so began 50 years of friendship and the most fruitful collaboration of my time.  I recognized early that Allan was a truly remarkable engineer, one of those rare individuals as talented in synthesizing machines and experiments as he was in analyzing phenomena.  I remember vividly the first time we flew back to Huntsville, Alabama in the 1970s to talk to NASA about a possible research program. The aura of von Braun and the Peenemunde kids still hung heavy around the Marshall Space Flight Center and the Redstone Arsenal and the huge test facilities gave the place a futuristic dimension. The Space Shuttle was then just a paper idea and the planned power density of the main engines were scary with all kinds of possible consequences.

That visit was the beginning of a long and very productive period in Allan’s career as well as my own – the beginning of a long sponsorship by NASA and a marvelous collaboration between Allan and I. Together we created a number of remarkable experimental facilities – facilities that in later years spawned copies in many institutions around the world – from Osaka, Japan, to Pisa, Italy, and many other places. But none that equaled the originality and productivity of  our “pump lab” in terms of the quality of data, new information and new concepts. That data and information are now used worldwide throughout the rocket and pump design industries.

Several generations of graduate students as well as numerous undergraduates contributed to and were witness to those events.  Allan was an inspirational teacher and along with all those students I learnt from him both the art and science of teaching. He made a fundamental contribution to whatever later success I enjoyed in the classroom. At the end of my teaching career, the students in my fluid mechanics class videotaped my lectures and, when I look at those tapes, I see Allan’s technique and even his gestures unwittingly reproduced.

But we also had great fun away from campus for we were both adventurers at heart. Allan taught me how to endure being hoisted to the top of a mast on a sailing boat in the middle of a gale and  how to disentangle the jib hoist prior to the start of a sailing race. How to swim/snorkle under the same boat to clean off the barnacles that allegedly were preventing us winning the race. How to dive down to the bottom of a kelp bed to pry abalone off the rocks with a tire iron and then to tenderize the meat with a piece of driftwood. And many more invaluable skills.

May the force be with you, my friend.

Christopher Earls Brennen, July 2019.

Ichiro Sugioka (Class of ’83)

Dear Professor Acosta,

Upon hearing that you are gravely ill, I find myself remembering fondly of the interactions that I had with you during my years at Caltech.  Beyond teaching us how to think and analyze fluid phenomena, I really appreciated learning that people in competitive professions can be friendly and supportive.  Those years led me to my lasting friendship with Tom Berto with whom I share many memories of your undergraduate courses.  You also direct me to attend MIT for graduate school, which in turn led me to my wife of 30 years.

Do you remember the time that Tom and I rode our bicycles down to Seal Beach from Pasadena and dropped in on you on your boat?  It was very nice of you to host us onboard for the visit.

In the last year or so, I have been fortunate to start enjoying retirement life.  It is with regret that I was too busy with work and life to visit you.  While I started my career helping Volvo produce aerodynamically efficient cars, I eventually shifted my focus to electrified drive train technologies.  Although I could not talk to you about it at the time, I like to think that you would approve the way I engineered to cool the lithium-ion battery modules in the 2003 EV that my team built at Volvo.

Thank you professor for preparing me for such a fulfilling life.

Yours truly,

Ichiro Sugioka

Class of 1983

From Tom Berto

Dear Doctor Acosta –

I apologize for taking so long to write.  A friend and I, on a recent Sierra backpacking trip, discussed our favorite and most significant college professors.  In my case, you are both of those. 

At Caltech, I had the unalloyed pleasure of learning fluid mechanics from you in my junior year, and heat transfer from you in my senior year.  Those two classes began what has become my lifelong love affair with mechanical engineering – and let into an ongoing career of 34 years.

I appreciate the wisdom and the inimitable, graceful style with which you taught those classes.  At times, I was transfixed, and at all times, I was learning.

Over the years I’ve been able to apply that experience in my career as a mechanical engineer.

You also provided direct and clear guidance to me at the end of my senior year, in regard to the choice between starting my professional career immediately, or continuing on in academia for a Master of Science degree.  As you put it: “You can work for the rest of your life.”   I remained a student for a while longer, attained my Master of Science in Mechanical Engineering at UC Berkeley, and never regretted any aspect of that experience for a moment.  I appreciated, then and now, your thoughts at that crucial time in my life.

I thank you, sir.   

Most sincerely, a devoted former student –