The History of the Gold Cup Boats -- Part III
My Next Record Attempt:
Will Jet Propulsion Make Possible a New Speed Record? --Sir Malcolm Campbell
As all the world of sport knows now, I intend shortly to make an attempt to better the world's water speed record of 141.7 mph, which already stands to my credit. A great many persons have asked me why I am going to essay to beat my own figures. Surely, they say, it would be enough to rest content until somebody else comes along to challenge the existing record and then go out to beat the new figures. Assuming, of course, that there were new figures to beat.
Well, it goes rather deeper than the mere desire to set up a new record. Standing by themselves, these speed records may mean much or little, as the case may be. Of course, there is a great sense of personal satisifaction in setting a figure which challenges the opposition but, if that were all, I should without much hesitation say that the effort was scarcely worth the time, trouble and expense involving in building a world-beating car or boat or aeroplane. It certainly would not be worth while if the achievement did not constitute a landmark on the road of progress. Every time we set up a new record of speed, either on land or water or in the air, we have learned something which can be applied to development and have travelled another distance towards that relative perfection of the machine which is the goal of human endeavor.
If I am fortunate enough to attain to new water-speed figures -- as I believe I shall, for reasons I will give a little later -- some valuable lessons will have been learned as to the practicability of propulsion by jet engines. So far, we know little or nothing about the possibilities. I think we can take it as certain that the jet principle can be best adapted to those purposes. It has certain characteristics and limitations which have to be studied and the problems arising must be solved before we can even visualize the liner propelled by jet engines.
Although we know so little about the subject, I am very firmly convinced that we stand at the threshold of a new era in power propulsion. I believe the possibilities of the jet are infinite and I look forward to the day when engines of the reciprocating type will be as extinct as the dodo. Of course, it may be that even the jet engine and its development may be put out of business by the application of atomic energy to most forms of power generation. But against that I would point out that we actually have the jet as a practical proposition, whereas atomic energy still remains in the stage of scientific possibility only. Obviously, there is only the one course to pursue and that is to study from all angles the actualy proposition we have in being, leaving the other to be brought, if possible, within the realm of practicability by the scientific enquirer. It would be the height of foolishness to neglect the concrete for the merely hypothetical. These, briefly, are the chief reasons why I have decided to attempt the use of a jet engine as a means of achieving a new world's record.
To reinforce this line of reasoning, let me hark back to my original water-speed records. I made my first attempt in 1937, and achieved a speed of about 129 mph. The main conviction resulting from this was that much higher speeds could be attained in the future. I had used a single Rolls-Royce motor, developing something in the region of 2,000 hp. To attain a still higher speed, the question arose as to whether or not to use two similar engines. One the fact of it, it would seem obvious that here was the solution of greater speed. But there were two factors which had to be taken into consideration. There was, first of all, the one of increased weight, which would have meant that a larger hull would have to be designed and built, and it was by no means certain that even then the desired result would be attained without prolonged and expensive tests. The second factor which had to be reckoned with was an even more serious one, that of propeller slip. We found that as much as 20 per cent of the engine power developed was lost through inefficiency of the propeller. So it seemed that the best line to be explored in the search for more speed lay in the direction of improving propeller design. So we concentrated on that and, after considerable research and many exacting tests, we were able to improve the design so far that in 1939 I was able, with a new hull and the same engine, to increase the figure from 129 mph to 141.7 mph.
Now, a new prime mover has arrived in the form of the jet engine. How is it to be applied and adapted to the propulsion of water-borne craft? In its present application to the aeroplane, the most usual form is where the jet exercises its thrust direct on the atmosphere. As we know, aircraft thus propelled have travelled at speeds well over 600 mph and there is every certainty that before long it will be possible to travel faster than the speed of sound. Indeed, it is scarcely too much to say that the future possibilities of speed in the air appear to have no practical defined limit when using the Stratosphere. And this, it must be borne in mind, has been brought into our line of vision solely through the invention and development of the jet engine. And the jet is only in its infancy as yet. Who can tell what the possibilities of the future may be? That future lies in the hands of those who are pioneering another new venture in the progress of human travel.
Will the jet revolutionize sea travel as it has already done in the case of travel by air? Who knows? But my main reason for my forthcoming attempt on the record is to assist, so far as in me lies, in finding out just what are the possibilities.
I have already referred to the enormous loss of propeller efficiency at high speeds. Now, we know from experience in the air that the jet engine can be used in conjunction with the conventional air screw. But if we use the combination for marine purposes we come up against the same problem of slip. So, to use a propeller for the record attempt would just tell us little more than we know now. So we have ruled that out.
There remain, then, the two alternatives of using the jet conventionally, so to say, by directing the thrust against the atmosphere, and by submerging the jet and utilizing the pressure generated against the more resistant medium of the water itself. So far as I am aware, no exhaustive experiments in this latter direction have so far been made. Of course, propulsion by a submerged water jet is comparatively well know though I do not think it has achieved any remarkable results. In any case, this method bears no resemblance at all to the problem which will have to be tackled as some time or other. I say advisedly that it will have to be tackled, because in the light of present knowledge it seems that the main line of research in connection with marine propulsion by jet must entail its underwater use. It is perfectly obvious that it is not a practical proposition to propel ships, or even small craft, by engines that expell enormous volumes of hot gases into the atmosphere. Either we must use the jet or gas turbine to drive propellers or in the alternative manner by exhausting the gases under water.
So far as concerns Bluebird, we are using a jet engine driving against the atmosphere. I am sorry that it is impossible for me to say at the moment anything about the technical details of the engine of its type and make.
At the present moment, we are carrying out experimental tests in the Admiralty tank at Haslar and in the wind tunnel. These tests are chiefly directed to finding the correct line of thrust, upon which much depends. One interesting thing we have discovered is that, while the tank tests were perfectly satisfactory, leading to the belief that we had found out all we wanted to know about the hull, when we came to the wind tunnel tests we found that everything was, literally, "all over the shop." So we have had to make several important modfications in the deck design to eliminate the trouble. I think we have found out some of the things we wanted to know but it is obvious that in adopting an entirely new method of propulsion -- and one so revolutionary -- there are still many things we have to take on trust.
We simply do not know how the boat is going to behave until we have an opportunity of actually trying her out under record-breaking conditions. While every possible test and trial is being made to ensure that things shall be right, we are faced with the fact that, while models tested in tank and wind tunnel may show perfect results, the unexpected may happen when we get down to the serious business of record breaking with the complete craft based on the results of these carefully carried out tests. However, all things lie in the lap of the gods and we can only hope for the best.
I intend to make the attempt over the same course I used when I made my existing record in 1939. One of the chief difficulties which has to be surmounted by the aspirant for water-speed honors in England is to find a suitable stretch of water. In my previous attempts I tried all sorts of waters, both here and in Italy and Switzerland, but was never able to find the ideal stretch which would give sufficient smooth water for accelerating to maximum speed, then the clear mile for the record, succeeded by length enough for pulling up and then the acceleration stretch for the return run. It should be remarked that, to constitute a world's record, a mean of the speed over out and home runs is taken as the ultimate figure. Finally, I discovered Lake Coniston which came nearest to the conditions I was seeking. It is by no means ideal but I found it the best available. I dare say I could have found something better in the U.S. or on the Continent except for one thing, the expense attendant on conveying boat and staff to the selected venue.
One important condition has to be observed if success is to be attained. That is, you must have dead smooth water for the attempt. You may have otherwise ideal conditions -- all the space you want, no obstructions and perfect visibility for timekeeping and the rest -- but you MUST have smooth water. I had investigated such waters as Loch Lomond, Lake Windermere, and several others in the Lake District of England, but there was always the trouble that either the lake was subject to the curious wind conditions so often found on landlocked waters, or the surface was disturbed by steam and motor craft to an extent that made it impossible to attempt really high speeds.
So I decided at last on Coniston, which fulfils most of the necessary conditions. You do from time to time get smooth water -- unless, of course, there is a gale blowing; in that case you just hang around until it subsides. There is no traffic on the lake -- at least, none to speak of -- so there is no interference as there is, for instance, on Windermere, where by the way, the late Sir Henry Segrave came to his unfortunate end.
So Coniston it is to be again. It has its drawbacks, chief of which is that it is in places only a half mile wide, which means that there is only some 44 yards on either side of the course. If all goes well, that does not matter, but it is certainly not too much if anything should happen to make Bluebird, traveling at full speed, take a sudden sheer. There are plenty of rocks at one end of the course, too, to make things more awkward! However!
When do I intend to make the attempt? As soon as possible. I had planned to make it about the middle of September but, as I have already explained, the results of some of our tests have made necessary considerable modifications in the hull design of Bluebird, which will, I am afraid, mean that she will not be ready until early in the following month. October is a bit late in the year for these attempts, but I am hoping to have the luck of the weather and to bring off the attempt before we have real autumn conditions to contend with.
What speed do I think I shall reach? I have no idea, except that it should be in excess of the existing figure of 141.7 mph. It certainly ought to be. Although, as I have already explained, I am precluded from saying anything about the engine I am going to use, I can say this: that the total power output, expressed in terms of thrust, will be a long way ahead of the power generated by the Rolls engine I used in setting up the present figures. I hope to be able, later on, to give the readers of Yachting not only all the essential details of engine and craft, but something about a new record and how it was achieved. But one never knows!
(ED. NOTE--Sir Malcolm Campbell first tested his jet-powered Bluebird on June 12-13, 1947, on Lake Coniston. The boat proved unstable at 150 miles an hour in straightaway speed, prompting Campbell to postpone further high speed trials. The engine was a de Havilland Goblin II jet unit as used in the Vampire interceptor aircraft. The horsepower rating was 6,250.)
(Reprinted from Yachting magazine, November 1946)