Interview with Sebastian Von Hoerner on 20 August 1979
Description
Creator
Rights
Type
Interviewer
Interviewee
Location
Original Format of Digital Item
Duration
Interview Topics
Start Date
Notes
The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.
Series
Unit
Transcription
Sullivan
Ok, this is talking with Sebastian von Hoerner at Montreal IAU [International Astronomical Union meeting] on 20 August 1979. Well, can you first tell me what your educational background was and I know you worked on many things before you came into contact with radio astronomy, can you just briefly describe those?
Von Hoerner
Yes, I hopped around in my working fields a few times and what I originally studied was theoretical physics and I somehow worked into hydrodynamics and met [C. F.] von Weizsäcker and worked with him in cosmic hydrodynamics, if you like, and we did a lot of work on turbulence and shock fronts at this time. And later on, I went to stellar dynamics and started these n-body calculations just on a computer, without any theoretical assumptions, just see what happens.
Sullivan
Which institute is this now?
Von Hoerner
The n-body problem was done in [Astronomische Institut in ]Heidelberg. Originally, I was at [the Max Planck Institute in] Göttingen and then this was at Heidelberg and there we had, what you would now call, a very slow computer and I could only work over whole weekends and in the course of several months got it done.
Sullivan
Somehow we had more time in those days too, I think, to do those sorts of things. How was it that you came into contact with radio astronomy then?
Von Hoerner
This came by surprise. I got a letter from Otto Struve who was very [?] and he invited me to come for a year as a visitor. And I was a little amazed and wrote back to him that I thanked him very much and I considered it an honor and a pleasure but I should be honest and tell him that I hadn’t the slightest idea about this field. And he wrote back that he was aware of that, he knows my papers, and he invited me and I could do whatever I like. And I wrote back, "Ok, sir, I’ve warned you and now I accept." And so I came and I must say I fell in love with the place on first sight. It was love on first sight when I saw Green Bank, met the people there, saw the spirit of the place, felt it, and this was a little different. At this time Green Bank was still in its very beginning.
Sullivan
What year now did you come?
Von Hoerner
’60.
Sullivan
1960.
Von Hoerner
And the only telescope which was there was an 85 foot, 25 meter telescope, 85-1, that it is now called. At this time, it was the only one. And there were plans for bigger telescopes but nothing was there. And so there was a lot of pioneering spirit of building things up and nothing worked. Well, it was just a very good atmosphere.
Sullivan
And do you attribute this to Struve’s leadership or was it the nature of the people on the staff or what exactly?
Von Hoerner
Well, it was everything together. It was a new field, radio astronomy was, and it was a completely new place. Green Bank just had been selected and started two before I came, and Struve was a wonderful man. For this task, he was a little too old because too many things went wrong and it needed a younger man with more physical power like [David S.] Heeschen later on.
Sullivan
Heeschen started in ’62, I believe, something like that.
Von Hoerner
But Struve, I liked him very much and most, I mean, all of us liked him and he mostly was very well balanced. He was old school and a gentleman and very seldom have I seen him lose him temper. One occasion was a very funny reason. Someone from the business administration had just painted the Grote Reber telescope, which is our exhibition piece, had painted it in blue and red and shiny colors without having asked Struve and the next staff meeting Struve got so furious about it. It was ridiculous and he said, "I want this observatory to become famous by the brilliant papers you write, not by the brilliant colors you use on the telescope."
Sullivan
Those colors had always struck me as being sort of nice.
Von Hoerner
Oh, they are very nice, sure.
Sullivan
But it’s also of course very interesting to have the old, traditional optical astronomer leading all these young radio astronomers. What was the reasoning behind...?
Von Hoerner
Well, Struve was just a well known person...
Sullivan
Was it to give creditability to Green Bank?
Von Hoerner
Yes, you need influence at higher levels and as happened so on. And so you wanted someone who is known and also from whom you know that he can be a good leader. And if everything had gone ok, he would have been a very good leader. The trouble was that we had a big problem with the 140 foot. I don’t know whether you know about it.
Sullivan
I know many details but you tell me about things that you were involved in.
Von Hoerner
Well, the problem was that the thing was designed by one man and improved by another man. Finally, some firm agreed to build it and when they were in the middle of building it, they discovered, in their opinion, something was wrong with the design and there was already the concrete building and pedestal finished. And there were some thousand tons- not hundreds, thousand ton of steel lying around and getting rusty and the firm refused on continue. And now, what do you do in this case- you build a committee to investigate. Well, they investigated for years and nothing happened. And at this time, some people in the higher levels saw that it might be a good idea to just call it a failure, close the whole place down, and forgot about it.
Sullivan
That would have been the end of Green Bank or would it have been?
Von Hoerner
No, this would, I think, have been the end to Green Bank. I mean the whole thing would have been closed down and called a failure.
Sullivan
Just that telescope you mean?
Von Hoerner
No, the whole place, Green Bank. All of Green Bank, just forget about it. And what made the great difference was that the 300 foot was designed all in a hurry and the condition was to make it with money where we didn’t have to [apply for?], which we somehow could scratch together. So the engineer were told make it for $800,000 and not a single one more or it will not be built. So they made it for $800,000 and became a very good telescope. And from then on, interest in Green Bank awoke again and all of a sudden the commission was forgotten and there was money to redesign and rebuild the 140 foot and that was finished. And from then on Green Bank was a good place.
Sullivan
So the 300 foot saved the 140 foot?
Von Hoerner
Yes, yes, that’s right.
Sullivan
And who do you think should get the primary credit for the idea and the pushing of the 300 foot?
Von Hoerner
Well, I think you have to mention three names and I do not know in which order. I’d have to say [John W.] Findlay, [Hein] Hvatum, and Heeschen.
Sullivan
And what were their specific roles in the building of the 300 foot?
Von Hoerner
Well, just putting it ahead, finding an engineer who could design it, this was Ed Felton, and just speeding it up as much as they could, scratching the money together, and just getting it done, period.
Sullivan
Were there any unique aspects of the 300 foot design?
Von Hoerner
Yes, the lead aspect was that it was done all in a hurry. That it was, for it size, extremely cheap, and that it really did work.
Sullivan
Right, but what were the engineering aspects that made it to be so cheap for its size?
Von Hoerner
Well, now that was a severe limitation, that it was a transit telescope that you cannot move in azimuth but only in declination. These $800,000, for example, limited the height of the towers. Now when you are limited in the height of the towers, you are limited in the amount of tilt [???] so you couldn’t look far enough south. Now some ingenious fellow, I’ve forgotten who it was, later on discovered if you just dig a hole in the ground you can go further south and that’s what we did. And another thing was, which made it cheap that we took a few risk. At this time, there was no possibility to really exactly calculate the stiffness and stability of a complicated structure. You had to make approximations and because of that engineers always used to multiply by pi and if you do this on two levels, you have multiplied it by 10 already. And that is the way the 140 foot was designed, heavy overdesigned and on the 300 foot, we made approximations, gave a little safety factor, not pi, and just built it. And then we were very afraid it would break down on the first snow and we had an Air Force surplus jet engine and we melted the snow away by blowing hot air at it. And this took several years and fortunately the same year when the jet engine broke down beyond repair, this was the first year when computer people had designed massive methods and better computers so that a complicated structure could be investigated, so you could believe the results. And then we found we just have to stiffen up, I don’t know, 4 or 6 members and then the thing would be good. That’s what we did.
Sullivan
I see. So the jet engine was used for how long, four or five year, you say?
Von Hoerner
Well, I would say three years.
Sullivan
But the real reason for it was that you were worried about the whole damn thing falling down?
Von Hoerner
Yes, and I mean we have ice-rain once in awhile and it can get 4 inch thick, solid ice and it’s a heavy load. We even once over a coffee break, Findlay suggested, "Couldn’t we heat up the surface electrically and melt the stuff which comes down?" And I thought that was a good idea so I sat down and calculated it and I found we would need 7 megawatts and I thought I’d made a mistake and well meanwhile, Findlay had done the same and came up with 5 megawatts. So we gave up on that one.
Sullivan
The local power company wouldn’t like that.
Von Hoerner
No.
Sullivan
Now, let’s go back to the 140 foot. What were the fundamental design problems, I mean, from a technical point of view?
Von Hoerner
The real problem is that it was designed at a time where computers were already available by engineers who didn’t know it, didn’t really believe it, or didn’t want it. So it was designed the good, old fashioned way before the time of computers, polar mount, where you move the telescope only around one axis while an alt-azimuth has to move around two axes in a complicated way. But computers had been available at this time already.
Sullivan
Well, Parkes telescope, of course, is an example- that was an analog.
Von Hoerner
No, Parkes did the first analog. They also didn’t believe in computers and I don’t understand it because I was at the beginning of the computer field and so fascinated by it and that was in the early ‘50s, around 1950 began the computer time. And for me, I just can’t understand it, period. And now we have a very silly design which is a sail lying up in the air, catches whatever comes in terms of wind and snow and all and it’s very vulnerable to solar radiation and to temperature changes of all kinds, summer and winter also, and it could be much better [?] alt-azimuth is closer to the ground and much easier to handle.
Sullivan
Sure but given that once they had chosen the polar mount, where there other basic faults that could have been done a lot better?
Von Hoerner
Yes- well, yes and no. I mean at this time when the first telescopes were built, all of them, not the 140 foot, nobody had thought in terms of short wavelengths. So I mean, you know the story of Jodrell Bank which was designed for 40 cm wavelengths and right away 21 cm was discovered and they had a problem. Our receiver was designed for the 21 cm line and now it is working at a few centimeters. And so on and so on, and the 140 foot again was designed, I’ve forgotten for what, I guess for 6 cm or 10 and nobody knew at this time and we couldn’t land on the short wavelengths would became so important and now we are on our way to improve the 140 foot.
Sullivan
Even 20 years later, yes.
Von Hoerner
Yeah. For example, I have studied the pointing errors which were much too large and had localized where do they occur and for what reason and partly the solar radiation and partly summer and winter and by spraying foam on some few parts, we have improved the pointing error by a factor of 3, which is a really good factor.
Sullivan
Well, there is very little thermal insulation.
Von Hoerner
Thermal insulation. And we have put heating pads on the upper floor so that also the summer-winter difference has become less. And the next step we are doing now is this telescope is not a homologous design which means that it deforms heavily under gravity when you tilt it, and this is the present limit of its accuracy. It’s not the surface; it is the gravitational deformation. And my idea was first to study the deformation and in first order, it is astigmatic which is the simple type so you just make a Cassegrain, a secondary, a Cassegrain mirror and deform it in the same way and then you correct the deformation of the big one and we had made an experimental design and at very good resolution. On the water vapor line at 20° elevation, we have improved it by a factor of between 2 and 3. And that again is a good factor and that was an experimental design and the real one will be finished in half a year.
Sullivan
Let’s go back now to the early ‘60s, like you say in some sense, it’s a bit unfair to say that it should have been designed for shorter wavelengths, but in terms of at that time were there other design problems in the original design that were improved?
Von Hoerner
Well, it was just a very overdesigned, heavy thing. I mean something an engineer would have made where he isn’t really sure of what he should make so he makes everything twice or three times as thick and then it gets so heavy that you cannot roll it on bearings anymore. Then you need fluid bearing and so it was resting on an oil fill and all this makes it awkward and expensive. And so the whole thing when it was built it was $12 or $14 million- at this time, a lot of money.
Sullivan
So it was an overdesign, you are saying?
Von Hoerner
Oh, heavily. You see, the 300 foot was $800,000.
Sullivan
Now, that is an amazing contrast. Now, how did you get involved so much in antenna construction and theory?
Von Hoerner
This was in the beginning when I came to NRAO I got very interested in cosmology. It was something I had never touched before, found very exciting and wanted to do a little work in cosmology so I studied it. I found it is almost all theory; almost no observation. And after a little bit of study, I decided what we really need is not more theories; what we really need is better observations. And that then again would mean special telescopes or bigger telescopes and so I began by trying to design a special purpose telescope that was going far out into space but for a very limited region of sky only.
Sullivan
And the cheapest possible thing to do the job?
Von Hoerner
This was a reflecting cross, a very large cross reflection antenna. And it turned out that as a one purpose instrument it would have been too expensive so we gave up on that.
Sullivan
Now, the estimated cost in your publication was just shy of $1 million for the whole installation, $500,000 for the antenna itself.
Von Hoerner
And when the engineers went over it, it turned more out like $2 million and then we had the feeling that $2 million for a single purpose wasn’t justified.
Sullivan
Because it can only look at the 1° strip at the zenith apparently?
Von Hoerner
Yes, you’re right.
Sullivan
But this the first, of course, of many feasibility studies and so forth that you got into antenna design. So this is what got you fascinated in the whole idea, in the structures?
Von Hoerner
Yeah, that’s right. This was the first time, I, in my life, touched engineering problems and structural problems and I just got fascinated and they looked so nice.
Sullivan
Were you a part of the whole 140 foot analysis at that time?
Von Hoerner
No, not that. But we had then, under the leadership of Findlay, we had the LFST, the Largest Feasible Steerable Telescope. And we started out with designing all kinds of very different telescope designs, all completely steerable, and with 200 meter, 600 feet, diameter and found out that they all turned out very expensive. So the question was not the largest feasible steerable telescope but the largest fundable steerable telescope. And then we cut in down to 100 meter and worked out a real design in detail and went to NSF [the National Science Foundation] for the money.
Sullivan
What year now are you talking about?
Von Hoerner
This was a 300 foot or 100 meter design and I had this idea of homologous deformations meanwhile so this means let gravity work as it likes, but make it so that it deforms from one parabola to another parabola and that was the main idea.
Sullivan
But what year now did you ask for the money from NSF?
Von Hoerner
I can’t tell. It was awhile ago.
Sullivan
Well, let’s say relative to the Bonn telescope was this several years before the Bonn telescope was built?
Von Hoerner
It could have been almost simultaneously.
Sullivan
So they had already adopted your idea for the homologous design?
Von Hoerner
The idea, yes, and we had a different method but the idea is this sort of homologous deformation. And I think I developed this idea around 1963 and worked it out in detail between ’64 and ‘5.
Sullivan
Now, you mentioned the size of 600 feet and, of course, my mind immediately rings a bell with Sugar Grove. Were you profiting from their experience in these designs?
Von Hoerner
No. I would say on the contrary because they gave up and this meant every big telescope was bad. So it hurt us.
Sullivan
So it hurt your chances for funding but in terms of design for telescope did you learn...?
Von Hoerner
We learned what we should not do. Make moveable panels.
Sullivan
That was the main trouble at Sugar Grove, you would say?
Von Hoerner
One of the main troubles.
Sullivan
What else? I’d be interested in your opinions.
Von Hoerner
They were also not sure about wind forces and other things and just again the awkward old way of if you are uncertain, you make it stiffer. And so after having finished the foundation, they wound up with something upstairs with something too heavy for what they had downstairs. And they made the mistake that they started to build the foundation before the telescope was finally designed.
Sullivan
Fundamental mistake to say the least.
Von Hoerner
Yeah.
Sullivan
Was the whole steering- now, of course, that was an alt-azimuth telescope so they didn’t make that mistake anyway.
Von Hoerner
No, no, not again.
Sullivan
But was the idea on the rails? I mean that would have worked out?
Von Hoerner
Yeah, we are still working with rails. We have now a 25 meter design and that again is moving on rails.
Sullivan
The millimeter telescope, you mean?
Von Hoerner
Yeah.
Sullivan
But now going back to the early ‘60s again, I know you that you had a very early interest in the whole extraterrestrial intelligence idea. How did you get interested in that?
Von Hoerner
I just can’t give you any date because even as a boy looking at the stars, I would wonder when I heard that stars are like our Sun and so on, well, would they have planets, would there be life. This is an old boyhood dream already.
Sullivan
Now were you at the famous conference at Green Bank?
Von Hoerner
No, unfortunately this was when I just had gone back to Heidelberg to think over whether I could come for good, and this time it was.
Sullivan
You went back to Heidelberg for a year or something then came back?
Von Hoerner
Yeah and then I found I just had to go back and somehow had to convince my family that it could be done.
Sullivan
But there must have been talk then around Green Bank about some of these questions?
Von Hoerner
Yes. Well, you see when I was there the first time, this was exactly the time when Frank Drake made his Project Ozma so I wasn’t involved in it but I looked over his shoulder everyday and we discussed in over coffee break and got excited about every little peak which turned up.
Sullivan
What was the attitude of other staff members towards Project Ozma? Can you remember?
Von Hoerner
They were very, very interested in it.v
Sullivan
There was no one that was was saying, "Oh, this is a waste of time?"
Von Hoerner
Well, someone might say so but, I mean, this you can say about any new project- that if it has no success it will be a waste of time.
Sullivan
But obviously this sort of thing is rather different than most other radio astronomy projects?
Von Hoerner
Yes. No I do not remember any, let’s say, fighting against him or making nasty remarks of that sort. Later on some people said he was going too much for publicity which I think that he should do and which is right because the public is interested. So I think there was nothing wrong.
Sullivan
But now you are getting into later years, in the late ‘60s you mean when you say later on or do you still mean...
Von Hoerner
Well, after this first Ozma trial when it was published.
Sullivan
Once the publicity began, I see.
Von Hoerner
It began right away. This is newspaper interviews and all the rest.
Sullivan
But now, I think your first paper was the one in Science, was it not?
Von Hoerner
Yeah, this was "Search for Signals" and I tried to make up my mind what could be done and what might it look like, and the next paper was about general limits of space travel. And at this time, I still had the idea or the prejudice that space travel must be finished within a man’s lifetime and only recently I’ve changed my mind completely. I mean, why shouldn’t it take generations if a whole colony goes and in a mobile home?
Sullivan
Or send robots or something like this?
Von Hoerner
No, a whole colony in a mobile home. I mean, a few thousand people in a big place and why shouldn’t they.
Sullivan
But in terms of your own thinking about this problem in those days, what kind of attitudes did you run into when you talked to other astronomers about these ideas?
Von Hoerner
Well, I, myself, was very fascinated and very positive and so, of course, I met people who didn’t share this attitude and were hesitant or a little opposed. But at this time, there was no mention of spending big money on it, so there was again no reason for heavy argument against it. It was just should I waste my time or not and if I’m willing to do, so ok with everybody else. And some astronomers would sit back and consider all this as nonsense but this was only, I would say, very few.
Sullivan
I think there are perhaps more today that say that. If you say a few then.
Von Hoerner
Well, yeah but the reason is not the project itself but the money to be spent on it. And everybody is afraid that it’s his money which is taken away.
Sullivan
I think there were a lot of people though that think that still, even if there was no money, that it is a waste of time.
Von Hoerner
Yeah, but that is a personal decision of those who do it. There is nothing wrong with that and the telescope time spent on it is very small.
Sullivan
Oh, that’s certainly true.
Von Hoerner
Up to now that we really haven’t done much. We have just started a few, almost a dozen, of very short trials on existing telescope with existing equipment so we haven’t spent any money.
Sullivan
Well, one final question is that you worked in Germany throughout the 1950s, not as a radio astronomer, but then you were involved with the Bonn telescope at least in a peripheral way.
Von Hoerner
Not in a direct way. I mean, I was in discussions with colleagues.
Sullivan
What I’m getting at is I’d be interested in your appraisal of radio astronomy in Germany vis-à-vis the U.S. in the late ‘50s and early ‘60s. There was this telescope at Stockert, which it seems to me did not really produce very much.
Von Hoerner
No, no, no. It didn’t do much.
Sullivan
What do you think are the basic reasons?
Von Hoerner
It’s hard to tell because at the same time there were telescopes in Holland, for example, of the same size and they did produce more. Now, they had the better electronics and maybe more astronomers got interested. I think I can’t give much comment since I wasn’t involved.
Sullivan
Well, I thought maybe you knew more about it since you were a German originally.
Von Hoerner
Yeah, but what I really envy- there is one point where I feel envy for my German colleagues and that is the way funding is done and was done also in the early projects. You see, the Efflesberg telescope and again the new 30 millimeter wave telescope...
Sullivan
Being built in Spain now.
Von Hoerner
Yeah, all this is done that you work out a feasibility study and a rough cost estimate and with this you go to your funding agency, like the NSF, and on that early stage, where you haven’t wasted much time on it, they tell you either forget about it, it’s not what we want or they tell you under the conditions that the final design meets what you say now, you will get the money. And then you go ahead and you put all your effort into it and you come up with something big. And if it is what you promised before then you have some money, go ahead and build it and there is nothing in the way anymore.
Sullivan
And what happens in the U.S.?
Von Hoerner
And here in the U.S. you first have to work out a final design. You cannot come with great ideas, with a feasibility study, [that’s not how it works?]. You have to work out a final design almost down to the nuts and bolts, and this takes years and years of hard engineering. Then you go to NSF. And I’m very opposed to this system that they never tell it no. They tell, "Oh sorry, not this year." And let me use a hard word, I think this is the way of cowards. They have not the guts to say no.
Sullivan
Bureaucratic approach.
Von Hoerner
Let’s us shove it off to the next year and to the next year and to the next year until you get tired and that’s not the way to do it. Those who give the money should have also the guts to say no if they don’t like it. And then they should say it on a very early state so you don’t waste your time and if you are told no at the beginning, that’s ok.
Sullivan
Then you can work on something else.
Von Hoerner
Yeah, you do something else.
Sullivan
Do you think this has hurt U.S. radio astronomy in particular?
Von Hoerner
Yeah, sure. We have, not only we, for example, the NEROC group. In the early days, there was the NEROC group from MIT and they wanted to build a big telescope in a dome and they had lots of engineers, good people, working on that project for years. And now meanwhile, it is clear that all that was wasted, talent and money wasted. And someone should have made the decision very early to tell them yes or no. And the same with us. You see, we had started out...
Sullivan
You are talking about the millimeter telescope?
Von Hoerner
Well, we went from 200 meter diameter down to 25 now. First from 200 to 100 meter then after we got several answers of this type, sorry not this year, we worked out a 65 meter telescope for 3 mm wavelength which I still think would have been a very good thing, again the answer was never a no. Then we said, "Ok, go do something smaller," so now we have made a 25 meter that is sitting there for 3 years. Nobody knows.
Sullivan
Good to 1 mm wavelength, I believe?
Von Hoerner
Yes and we hoped that we will get funded before the size converges to 0.
Sullivan
Ok. Well, thank you very much. That ends the interview with Sebastian von Hoerner on 20 August 1979.