WITH this article, the rocket propulsion industry and profession are invited to comment upon and to criticize the present informal (and therefore unofficial) publication of a proposed American Standard Letter Symbols for Rocket Propulsion. In responding to this invitation, it will be appreciated if all comments are addressed to J. P. Layton, Secretary, ASA Y10 Subcommittee 17, c/o The American Society of Mechanical Engineers, 29 W. 39th St., New York 18, N. Y., prior to December 15, 1955. Alternatively, for those who will be attending the 25th Anniversary Annual Meeting of the American Rocket Society in Chicago this month, a cordial invitation is extended to participate in the Forum on Letter Symbols for Rocket Propulsion at 4 p.m. on Tuesday, November 15, 1955. BACKGROUND. Preparation of the proposed standard has been the responsibility of Subcommittee No. 17 on Rocket Propulsion, one of seventeen subcommittees appointed by Sectional Committee ASA Y10 on Letter Symbols. The other subcommittees cover Mathematics, Hydraulics, Mechanics of Solid Bodies, Structural Analysis, Heat and Thermodynamics, Photometry, Electrical and Magnetic Quantities, Radio, Physics, Chemical Engineering, Acoustics, Meteorology, Feedback Control Systems, Abbreviations, and General Principles of Letter Symbol Standardization. Sectional Committee Y10 was organized under the procedure of the American Standards Association in January 1926 with the American Society of Civil Engineers, the American Institute of Electrical Engineers, the American Society for Engineering Education, The American Society of Mechanical Engineers, and the American Association for the Advancement of Science, as joint sponsors. The committee was reorganized in October 1935, and it now consists of representatives of 42 national societies and associations, under the reorganization of April 1951. The American Society of Mechanical Engineers has assumed the role of sole sponsor and maintains a Standards Department devoted to the editing and publishing of American Standards. Subcommittee No. 17 was established as a result of discussions arising during 1952 on the revision of American Standard, Letter Symbols for Aeronautical Sciences, ASA Z10.7—1950. During its discussions, Subcommittee No. 7 on Aeronautical Sciences found that a great many specialized terms in the field of rocket propulsion (particularly concerning internal aspects of rocket powerplants) were being proposed for inclusion in the revised Aeronautical Sciences Standard. C. W. Chillson, a member of Subcommittee No. 7, undertook the task of recommending which of these symbols should be included in the revised Aeronautical Sciences Standard. Subcommittee No. 7 adopted several of the proposed symbols and at the same time recommended to the ASA Sectional Committee on Letter Symbols the establishment of a new subcommittee to formulate an American Standard on Letter Symbols for Rocket Propulsion. Subcommittee No. 17 was originally constituted in 1952