Report from Goddard to Assistant Secretary Abbot
Goddard, R. H., Dr.
Department of Physics May 5, 1926
Dr. C. G. Abbot, Assistant Secretary
Dear Dr. Abbot:
This report is an outline of the progress on the rocket work that has been made to date. I am sending vouchers under separate cover.
Test of December 6, 1925
On December 6, 1925, a 12-lb. Rocket in its final form was tested in a frame which permitted an upward lift to the extent of one foot. This model included pumps, and operating and governing devices, as mentioned in the letter to the Institution of October 5, 1925; a double-acting engine, however, being used in place of two separate engine systems, which were tried because they involved less work of construction, but which were found next to impossible to operate together.
This model operated perfectly for 27 seconds, until the liquid propellant were used up, the chamber and nozzle being uniformly, and only moderately, heated, and the rocket being in as good condition after the run as before; the chamber and nozzle being, in fact, the same as used in a number of previous tests, with various governing devices. The lift was just enough to balance the rocket's own weight.
This test was an important one, in that it demonstrated that the problems of pumping, governing, and control of heating were solved, but it also showed that a rocket on as small a scale as this model would not lift itself sufficiently to give a flight, including, as it did, devices which would not be necessary in a larger rocket.
Test of March 16, 1926
Although the problem of satisfactory operation was solved, it was not possible to have a flight unless a larger model were made, or a different principle, permitting greater lightness, were employed. The construction of a larger model was not undertaken because of expense, and another plan of construction was used, which involved back pressure in the supply tanks, and eliminated the pumps, engines, and most of the moving parts, but did not permit such accurate control of the combustion, nor the use of the lightest form of supply tanks, as did the previous model. A test of January 20, in the testing frame above mentioned, indicated a pull throughout the test of more than 9 lbs., and a similar model, of as light construction as possible, was accordingly made. The lack of control of combustion manifested itself in the frequent burning out of the nozzles.
In a test made March 16, out of doors, with a model of this lighter type, weighing 5¾ lbs. empty and 10¼ lbs. loaded with liquids, the lower part of the nozzle burned through and dropped off, leaving, however, the upper part intact. After about 20 seconds, the rocket rose without perceptible jar, with no smoke and with no apparent increase in the rather small flame, increased rapidly in speed, and after describing a semicircle landed 184 feet from the starting point -- the curved path being due to the fact that the nozzle had burned through unevenly, and one side was longer then the other. The average speed, from the time of the flight measured by a stop watch, was 60 miles per hour. This test was very significant, as it was the first time that a rocket operated by liquid propellants traveled under its own power.
Several trials have since been made, using most of the original rocket, with less weight of propelling liquids and with other minor changes, but although it has left the frame and traveled as much as 50 feet away, the handicap of weight has left it in its frame for a half minute or more before lifting has begun.
To me, personally, these tests, taken together, prove conclusively the practicality of the liquid-propelled rocket, which means that the multiple charge idea, or the feeding into a combustion chamber of successive portions of propellant material from extremely light containers or tanks, is realizable.
In case the person or organization which is willing to finance the development of a high-altitude rocket for serious work is not satisfied with the flight of March 16, it will be necessary to make the rocket on a larger scale, in order to increase the lift in proportion to weight. I believe that such a larger model can be made for $500. Incidentally, however, some of the materials would require from three to five weeks for delivery.
On the other hand, I believe that to make this additional trial flight would be a waste of time and money, for several reasons. First, all the principles involved in the construction of a rocket to beat the altitude records have been worked out satisfactorily. Further, the latest model, although useful, no doubt, for some work, and representing the acme of simplicity, makes accurate control of combustion a difficult matter, and does not permit the use of extremely light fuel tanks, which do not have to withstand pressure. Hence I should not consider using the principle of the latest model in a rocket intended for reaching great heights, and I cannot predict beforehand just what can be accomplished by its use.
I should be glad to come to Washington, if you so desire, to make clear any matters connected with the work, and discuss plans for the development of a rocket to reach great altitudes. In the meantime, I would appreciate it if no public statement, such as recently suggested by Acting Secretary Wetmore of the Institution, were made before I had opportunity to supply such details as it may seem desirable to include. My reason is that this rocket work is being made almost a national issue in Germany, a novel having been written, playing upon race feeling, in which Germany is urged to support the development of a German liquid-propelled rocket, which, the readers are given to understand, is a German idea. Nearly every day, I am in receipt of requests from Germany for information and details.
Another point is that Science Service is very anxious to secure statements from a number of authorities regarding the importance of this rocket work in time for publication when any announcement is made by the Smithsonian Institution. I assume that the Institution would not be averse to notifying Mr. Watson Davis when to gather his material, inasmuch as the Institution is represented by you on the Board of Trustees of Science Service.
I am enclosing an enlargement made from a film taken at the time of the test of March 16, which I might entitle "The Empty Frame," inasmuch as I had been working to make a liquid-propelled rocket leave a frame since 1920.
Very truly yours,
[signed] R. H. Goddard