- The Empire Club of Canada Addresses (Toronto, Canada), 10 Apr 1958, p. 287-299
- Heard, John Frederick, Speaker
- Media Type
- Item Type
- A brief history and review of the Sputnik satellites, and the American satellites. Orbits of these satellites. The lack of danger to earth from the satellites falling. The ways in which satellites are scientific experiments. Some preliminary results from the study of the orbits of these satellites. Observation of the satellite as a heavenly body. Satellites offering almost unlimited opportunities to study the earth's atmosphere, the earth itself, and the radiations and particles coming from the sun and stars which are screened from the earth's surface by the rather dense atmosphere in which we live. More ambitious space experiments ahead. The issue of manned space flights. Flight to the moon. The cost of interplanetary voyages. Information yet to come to scientists as a result of satellite experiments.
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- 10 Apr 1958
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- Full Text
An Address by
JOHN FREDERICK HEARD, M.A., Ph.D., Head of the Department of Astronomy and Director of the Dunlap Observatory--University of Toronto
Thursday, April 10th, 1958
CHAIRMAN: The President, Lt.-Col. W. H. Montague.
LT.-COL. MONTAGUE: Although Canada is not currently in the race to produce rockets and to successfully launch them into orbit in outer space, the fact is inescapable that the implications of the success achieved in this field by Russia and the United States have made such rockets our business.
When we read on the front pages of our newspapers that Russia proposes an agreement to prohibit the use of outer space for military purposes and an undertaking to launch rockets into outer space only in accordance with an agreed international program, provided that the United States will liquidate all foreign bases on territories of other countries, viz., in Europe, Middle East and North Africa, then it is surely time for Canadians to take notice and find out something about this very important subject.
To this end, we invited no less an authority than the eminent John Frederick Heard, M.A., Ph.D., Professor of Astronomy, Head of the Department of Astronomy and Director of the David Dunlap Observatory of the University of Toronto, to address us today on the general subject of "Sputniks". We are grateful that he has honoured us by accepting and we extend a most cordial welcome to him.
Dr. Heard was born in St. Thomas, Ontario. He graduated from the University of Western Ontario in 1929 with a B.A. degree. He advanced to his M.A. in 1930 at McGill University and continued there until 1932 when he achieved his first Ph.D. in Physics. He then went to London, England, as an 1851 Exhibition Scholar and after two years, in 1934, he secured a second Ph.D. in Physics.
1935 found him an instructor at the University of Toronto. Then he was promoted to Assistant Professor, to Associate Professor and, in 1952, to Professor of Astronomy, Head of the Department of Astronomy and Director of the Dunlap Observatory his present very important post.
When Canada was at war, Professor Heard laid aside his gown and went into uniform with the R.C.A.F. from 1940 to 1945. He served as a navigation specialist and staff officer and was demobilized as a Squadron Leader.
Dr. Heard's work in Astronomy is mainly in the field of stellar spectra with particular emphasis on the motions of the stars. From 1953 to 1954 he was President of the Royal Astronomical Society of Canada. He is a member of the American Astronomical Society and of the International Astronomical Union.
As I said earlier, he will address us on the subject, "Sputniks".
Gentlemen: Dr. John F. Heard, M.A., Ph.D., of the University of Toronto.
DR. HEARD: I hope I will not be offending you if I assume that you are at this time a little confused by the international assortment of hardware and live stock which has been flitting this way and that way around the globe during the past six months. So, perhaps, I may take a few moments to catalogue the satellites to date before we discuss the nature of the satellites, their usefulness and to what further developments, in my opinion, they may be leading.
Let us think back. Sputnik I, the first satellite, launched October 4th, last year, by Soviet scientists, circled the earth essentially from pole to pole. This was a characteristic of the Russian satellites. They went nearly from pole to pole, so they could be seen over wide areas on the earth, circling in a period of about 96 minutes, at an average height of about 360 miles in the beginning. There were three distinct parts to this satellite that were in orbit. There was the satellite itself, which was a 23-inch sphere, weighing, according to figures given out by the Russians, 184 pounds. Then there was the rocket carrier which had launched this into its final orbit, and which must necessarily, therefore, be in orbit itself--a much larger object, presumably rocket-shaped. It has been established there was a protecting nose-cone which originally protected the satellite before it was separated from the rocket carrier.
There were three distinct objects. All three parts have now fallen to the earth. They presumably were destroyed by the entry into the fairly dense part of the atmosphere at a height of about ninety miles, where the meteors and the meteorites encounter enough atmosphere to make them glow and partly, if not altogether vapourize. The destruction of the rocket carrier was first and took place early in December. The fall of the satellite took place early in January and the nose-cone--no one knows when, but it is certainly down now. So Sputnik I has passed into history.
Sputnik II, also Russian, a one-piece affair, is rocket shaped. This was the one that carried the dog, Laika for biological experiments. This was a very heavy affair, weighing about 3.5 tons, probably 50 feet long, 7 feet in diameter--an enormous object. This is still in orbit. It went into a slightly higher orbit than the first sputnik. It has lasted somewhat longer. It is still in orbit. Launched in November, it is due down within the next few days.
Now, by a curious coincidence which I assure you neither your President or I had any foreknowledge of, this satellite in its dying stages is about to pass over Toronto or very nearly over Toronto, about the time I finish speaking--about 1.40. Now, I can't think of anything much more dramatic, so I will ask one of your guests, perhaps, to keep a lookout out the window because it is going to come from the southwest and pass toward the northeast.
Of course, I am joking. The chances of this coming down today are very small. The chances of it meeting the earth are very small. Actually, if anyone is concerned, and a few people have been concerned as to whether the satellite might conceivably do any damage, I would ask you to keep in mind, that every day about six meteorites, weighing perhaps a hundred pounds or more apiece, fall to the earth's surface, and there has only been one recorded instance of a person being hit by a meteorite. So I don't think we have to worry too much about these few satellites coming down.
Now, those are the Russian satellites. The American satellite, Explorer I, the United States Army one-piece rocket-shaped affair, about seven feet long, weighing about 31 pounds, was launched January 31st, at still greater height, an average height of 900 miles above the surface of the earth, a still longer circuiting period than being followed by radio signals and our own observations at the Observatory lead us to think that it will stay up for several years.
The orbits of this and other American satellites are more equatorial than polar, which means that they go around the earth more nearly in equatorial regions than over the poles. Consequently, they are, I won't say of less interest, but less likely to be observed by us here in Canada.
The second American satellite which is still in orbit is the Vanguard, which is United States Navy, two pieces this time. The satellite itself is the size of a grapefruit. The final launching rocket is about four feet long. It was launched on March 17th, a still higher altitude, an average height of about 1400 miles, a larger circuiting period and it is expected to stay in orbit for perhaps ten or twenty years, and its solar-charged batteries may last almost indefinitely and keep this satellite transmitting messages to the earth. We are also receiving the messages from this satellite. By messages I merely mean the sound of the transmitter.
The final one of the five is Explorer III. It is called the third because Explorer 11 misfired. It went to a sufficient height, apparently, but did not get in orbit, but it is reckoned apparently as Explorer II.
Explorer III is similar to Explorer I, on a lower orbit, average height of about 950 miles, and is expected to last only a few months.
Now such a recital as that may have raised some questions in your minds. One question is frequently asked: What keeps satellites on their repeated circuits? The answer is that no power is needed any more than a power is needed by the moon in its orbiting around the earth, or the earth, to keep it orbiting around the sun. The satellite was given an initial velocity at a sufficient height, nearly parallel to the earth's surface, so that a centrifugal force was developed which just balanced gravity. So we have now in these satellites going around the earth an exact balance between the natural centrifugal force tending to throw away from the earth, and the drag of the earth's motion which tends to keep them down. Such is the result of the balance of the satellite's motion. If this satellite is definitely out of the drag of the earth's motion there is no reason why it should not orbit indefinitely.
The second question is: Why have I talked about the average height of these satellites? The answer in general is that a satellite is on an eccentric orbit. That is to say it dips low on one side and rises high on the other side above the earth.
I have listed on the card behind me the maximum and minimum heights of the satellites, as they were at launching, and it is worth looking at for a moment.
Min. Ht. Max. Ht. Sputnik I 145 miles 575 3 months Sputnik II 140 miles 1020 5.5 months Explorer I 219 miles 1587 years Vanguard 400 miles 2400 decades Explorer III 110 miles 1735 months
You see that the Sputniks, the two Russian satellites, have had minimum heights of around 140 miles and then have risen to heights of 575 and 1020 miles at their greatest height.
Explorer I went higher, both as regards the minimum height of 219 miles, and the maximum of 1587 miles. But Vanguard is the outstanding satellite to date in this respect. It went higher than any of the others. It never dips below 400 miles from the earth's surface and it rises about 2400 miles at the greatest height. Explorer III is a sort of throw-back to a lower satellite --110 miles minimum height, and 1735 maximum height. Now, on the card which is directly behind me, to give the idea of proportions there are the earth and the orbits of the Vanguard satellites drawn to scale. You see it dips fairly close to the earth at the closest approach, but it is getting to be a far distance at the greatest distance from the earth.
Now, another question: What brings satellites down at all? The answer is, these artificial satellites are not entirely outside the earth's atmosphere. The atmosphere falls off very rapidly, it is true, but there is still enough at a few hundred miles height to exert a drag which has the effect of causing the satellite gradually to lose height and to spiral towards the earth. The rate of fall is governed by both the average height and the minimum height, and so it is interesting to see what the calculations have been as to the lifetime of these satellites. They will last until the orbit has shrunk to a height of about ninety miles above the surface of the earth. Then they encounter atmosphere of such density that the acceleration downward is quite rapid and they can last only a few more days. The higher they start the less atmosphere they are encountering and the longer they will last before that shrinking takes place.
We see that Sputnik I lasted about three months. Sputnik II apparently is going to last about five and half months, because it is due down within the next few days.
Explorer I, according to our own observations would seem to have an expectant lifetime of some years, and the Vanguard satellite, a very small one, may be there for decades.
Rather an interesting idea, isn't it, to think if we can wait perhaps twenty years we may see a very small item in the newspaper that the Vanguard satellite is believed to have fallen to earth. We may talk about it to our grandchildren.
The nature of this downward spiralling is to cause the orbit to become first nearly circular. Then when it has become nearly circular the satellite spirals in fairly rapidly until it encounters this region of the atmosphere where the heat engendered will be sufficient to disintegrate it.
We have had one experience of that happening, namely, with Sputnik I. Dr. John Kraus of Ohio State University believes he detected and followed the break-up of Sputnik I by receiving the echoes of WWV radio time signals reflected from an ionized atmosphere trail which accompanied the disintegrating metal.
On the other hand, there were no absolutely certain observations of any visual meteors which resulted from the break-up of this first satellite. You may be sure, during the next few days intensive attempts are being made to observe, if possible, the break-up of the second Russian satellite. This is not just an academic point. This 'is of very practical importance because it is important for many reasons to know what happens to a satellite when it re-enters the atmosphere.
Now, I want to emphasize this, that the satellites are not merely scientific toys or demonstrations of prowess on the part of rocket experts. They are important scientific experiments. In fact, we can think of each satellite as comprising two classes of experiment. The first class of experiment involves the satellite as an experimental heavenly body, subject to the usual laws of motion of 'heavenly bodies, differing only from the natural bodies in that it is so close to the earth. To take one example, we have seen how orbit changes of satellites take place by virtue of the satellite being not entirely outside the vestiges of the atmosphere of the earth.
The rate at which these orbit changes take place, the shrinking of the orbit, is dependent on the amount of atmosphere up at those heights of one, two, three hundred miles. It is also dependent upon the mass of the satellite, the weight of it, the dimensions of it. So now if careful observations are made of this rate of shrinking of the orbit of the satellite, if we have the correct information about the size and the weight of that satellite, then it should be possible to investigate the density of the atmosphere at the various layers above the surface of the earth. This is something that is not very accurately known at the present time.
There are a number of agencies, both in the United States, Russia, and also in the United Kingdom, which are working very hard, continuously, on this problem of determining the changes in the orbit of these satellites as they come down to earth with just that in view. This is an attempt to investigate the upper atmosphere of the earth as to density.
It might be interesting to tell you a little of the preliminary results along these lines, because one of these agencies, the Smithsonian Physical Observatory, has already published very tentative results as a result of the fall of Sputnik I, the satellite proper. They have found, accepting the Russian data concerning the size and weight of that satellite, that they must attribute to the upper atmosphere a very much higher density than was previously thought to be the case. This is not terribly surprising, because previous knowledge of upper atmosphere of one hundred miles above the surface of the earth wasn't very accurate. However, they have established that it is several times denser than, say, the best guesses that have been made to date.
Now, here is an interesting point. If we take that information of the density of the atmosphere and apply it to the rocket carrier that accompanied the first satellite and to the rocket-shaped second Russian satellite, it is possible to make interesting computations concerning the weight of these rocket carriers. The Russians gave out their information on the size and shape of the spherical satellite proper, but they did not, for reasons which may have some military significance, give out the size or weight of the third stage of the rocket which carried the satellite up there and which was responsible for putting it in orbit and which itself must necessarily go into orbit. It isn't possible, however, to conceal the size of this rocket carrier, nor is it possible to conceal the size of the second Russian satellite, because we have observed these many times. Whenever they are in a twilight sky and pass near the Observatory the satellite can be observed and from the brightness one can make a pretty shrewd guess as to the size. It seems inescapable that the size of the first satellite rocket and of the second satellite itself was rather large, to put it mildly at least seven feet in diameter across, and about fifty feet long. This seems to be a conservative estimate. This is a big thing to have thrown up into orbit.
Now, if the scientists who are investigating the density of the earth's atmosphere have also determined the rate at which this fell, the only unknown quantity that remains in their equations is the weight of that rocket carrier. It seems that the weight of the first rocket carrier, the first satellite rocket carrier and of the second satellite itself was, to put it conservatively, three and a half tons. You remember that the Russians gave out a weight for the second satellite as 1150 pounds. It turned out later that this referred to the instrumented part of it and to the dog. It didn't refer to the rest of it. So apparently the Russians have been able to put into orbit all-up weights in the neighbourhood of three and a half tons.
Now, let us compare that with what the Americans have done to date. The all-up weight of their Explorer was about 31 pounds. In the Vanguard, the all-up weight of the two combined pieces was something over 50 pounds. So I think we must be impressed by the rather staggering ballistic effort that the Russians have demonstrated. This doesn't mean to say that American rocket experts have shown all they can do so far. This has been purely experimental. Nevertheless, based on demonstrations to date, I think we must say that the Russians have demonstrated a superiority, ballistically, over the American efforts of the factor of perhaps somewhere between ten and a hundred.
I have spoken of one part, one kind of an experiment, that falls into this class of observation of satellites from the ground. There are others and I think I will not detail them except to tell you that one kind of observation that can be made concerning just the way the satellite orbit behaves will give us information, it is hoped, about the shape of the earth. The orbit swivels around that way which is dependent upon the equatorial bulge. You recall we all learned in school that the earth wasn't a sphere. It flattens at the poles and bulges at the equator. The accuracy of the bulge is known by the geologists to within about a hundred yards. That seems accurate, but one Soviet geophysicist has estimated that with careful observation of satellite behaviour it may be possible to reduce this uncertainty to as little as five yards. It seems a remarkable thing that a little satellite, revolving around the earth, can eventually give us more information about the shape of the very earth we live on than we have been able to achieve in centuries of measurement right here on the surface.
One type of experiment is observation of the satellite as a heavenly body. The second class of experiment involves the use of satellites as instrument vehicles. We have all read that satellites are to a greater or less degree carrying instruments which measure such things as upper air temperature, cosmic ray intensity and the impact of micrometeorites. The results come in the form of coded variations of the radio signals sent out by the satellites.
As far as I know, the code can be interpreted only by the designers of the instruments, and it is rather hard to see how it could be otherwise at the present state of the experiment. There is every reason to believe both the American and the Russian scientists will publish their findings as they have agreed to do under the terms of the I.G.Y.
There is other information to be obtained on the study of satellites but these two classes are picked out to give you an idea of the versatility of the satellite experiments. Thinking of a satellite as a heavenly body that needn't have a radio at all, we can observe how it moves in the outer parts of the earth's atmosphere, how it is affected by the bulge of the earth, and the other part of the experiment involves using the satellite as a vehicle to carry instruments.
I think we can realize that the satellites offer almost unlimited opportunities to study the earth's atmosphere, the earth itself, and the radiations and particles coming from the sun and stars which are screened from the earth's surface by the rather dense atmosphere in which we live.
In order fully to exploit these possibilities I would think that many satellites will be launched on different orbits, orbits of different shape and size. Practice will make perfect the achievement of precisely the required orbits, and I doubt if very great accuracy has been achieved yet.
For astronomers there would be a considerable use for a permanent satellite of appreciable size placed in orbit at a height of several thousand miles so as to be essentially permanent. This would serve better than any natural heavenly body for testing any theories, including the theory of relativity.
To go a little further, in spite of all the opportunities provided by the present satellites, there is plenty to indicate that both American and Soviet scientists are impatient to get on with more ambitious space experiments. The experiment with the dog, Laika, was obviously directed toward manned satellite flight, but in this direction there are very difficult problems to solve--the problems of re-entry into the atmosphere without destroying the contents, and the problem of a soft landing on the surface of the earth. We can expect to see experiments along this line soon, I would expect.
Yet, to tell the truth, I find it a little difficult to understand what purpose would be served by a manned satellite flight. I suppose the critics of Columbus, the Wright Brothers, and Sir Edmund Hillary said the same sort of thing.
We also hear about flights to the moon unmanned and manned. Among the proposals that have been discussed is, first, placing a small object on the moon. This would call for rockets of somewhat greater thrust and a good deal more accuracy than has been demonstrated so far, and, yet I have no doubt that it will soon be accomplished. I don't know what scientific end would be achieved by this experiment.
Secondly, sending a satellite on an orbit which will circle the moon and return to the vicinity of the earth. This, according to careful computations made by Soviet scientists, is possible and feasible. Conceivably, this might bring us a television picture of the back of the moon, the side of the moon that no one has ever seen, because, you know the moon turns always the same face toward the earth
Now, I wonder what those cameras will see? Will they see the same kind of craters and mountains and lava beds which we see on our side? Well, maybe more, because there is one important difference between our side of the moon and the far side of the moon. Our side of the moon, for millions of years has been subject to rapid coolings and equally rapid reheating that occur during a total lunar eclipse, when the moon enters the earth's shadow. That doesn't affect the far side. Many selenographers believe this has been an appreciable factor in modifying the surface of the moon, our side of the surface of the moon--rapid heating and rapid cooling, the cracking and the chipping of the lunar rocks. If this is the case perhaps we could expect that the far side of the moon would be considerably more rugged than our side of the moon, so it is conceivable that a picture of the far side of the moon may give us some really good clues as to the moon's history and development.
On the other hand, maybe the first ones around there will just see a big sign, saying, "Yankee, go home". Man's flight to the moon with a landing on return to the earth is contemplated by some. Surely that is a long way off. The problems are of a completely different order of difficulty because this idea involves a payload to the moon which must include rockets to soften the landing on the moon, further rockets to take off from the moon, further rockets to soften the landing to the earth. The cost and the effort, I would think, of such a project would be prodigious and beyond present developments.
I think it would be foolish to prophesy that manned lunar voyages and even interplanetary voyages will not come about. The cost and the effort will certainly be fantastic and I believe it is proper at this time to ask, as some scientists are asking, if the results will repay the cost.
Even an astronomer--perhaps I should say especially an astronomer--should be sober enough to weigh the possible advantages of a brief landing on Mars against the dollar equivalent in research nearer home. I have heard many, astronomers particularly, express this view. However, perhaps we are going too far afield. I hope we will not lose sight of the hundreds of patient, skilful scientists who are now and who will be for years to come wresting some of the secrets of Nature from the vast accumulation of data from the present satellites, not to mention the man that we expect within the next year or so.
For the man on the street, satellites are, I am afraid, almost old stuff. For the scientists, the best part of the experiment is still to come--the result.
THANKS OF THE MEETING were expressed by Mr. Bruce Legge, Vice-President of the Club.