Access the full text.
Sign up today, get DeepDyve free for 14 days.
Loading next page...
/lp/emerald-publishing/letters-to-the-editor-9ipHS6K3xI
References
References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.
- Publisher
- Emerald Publishing
- Copyright
- Copyright © Emerald Group Publishing Limited
- ISSN
- 0002-2667
- DOI
- 10.1108/eb032115
- Publisher site
- See Article on Publisher Site
Abstract
permissible. Some indeterminateness is bound to arise, however, when we try to place a physical interpretation on the condition M= l for non- isentropic flow. Wc feel that some confusion A Reply by the Author to Mr Cleaver of the British Interplanetary Society— might be dispelled if the matter is viewed in the following way. Further Correspondence on Flow through Convergent-Divergent Nozzles One-dimensional isentropic flow yields to simple mathematical treatment and provides still be very considerable. The problem is prim solutions which are undisputed. One-dimensional FUNDAMENTAL DYNAMICS OF arily one of deciding whether the means chosen non-isentropic flow is an impossibility, and its REACTION-POWERED SPACE are justified by the end in view. mathematical treatment using concepts such as However, although orbital techniques do not polytropic efficiency, though convenient from a VEHICLES greatly affect the basic problem, i.e. the economics practical point of view, is a makeshift adopted to aspect of space flight, there is little doubt that in overcome the difficulties of three-dimensional To the Editor, the ultimate development of interplanetary travel, treatment. Deductions drawn from such analyses DEAR SIR, these techniques will play an important role. Th e to give a physical interpretation of real flow must In a letter, which has jus t come to my notice, main virtue of sub-orbital techniques is that by always be unsatisfactory and inconclusive. published in your October 1951 issue, Mr A . V. splitting up a given space-flight into several In conclusion, we agree with Kestin and Cleaver advocates the use of sub-orbital refuelling stages, the need for individual vehicles of ex Owczarek5 that the concept of a friction force techniques as a means of rendering inter cessive weights is theoretically avoidable. As the applied to the boundary of the stream is the only planetary flight an economic proposition, and power dissipation problems associated with reasonable way t o allow for irreversibility in one- suggests that the importance of this factor was hypothetical large atomic rockets developing dimensional flow. It does not, of course, over underestimated in the above paper which was high thrusts at high jet velocities may be very come the particular difficulty we have been dis reprinted in your August issue. severe, it is therefore probable that some appli cussing. cation of orbital techniques will be necessary. It must be borne in mind that, in the paper in Yours faithfully, question, the feasibility or otherwise of space Space flights utilizing chemical propellents and G. F. C. ROGERS flight was decided on the basis of the economy sub-orbital techniques would be so expensive Y. R. MEYEROWITZ with which it could or could not be achieved. It that they would be of scientific interest only, and University Engineering Laboratories was not denied that step-by-step orbital tech of a 'once-only' nature. If there is to be much Unity Street niques offer possibilities of appreciably reducing point at all to space-flight, it must be rendered Bristol, 1 the physical magnitudes of the various individual capable of becoming reasonably commonplace in October 17, 1951 vehicles involved in a space flight undertaken by an economic fashion. Economy of the required these means, but it is by no means certain that order can only be achieved by some efficient REFERENCES TO LITERATURE the project is rendered more economical by the application of nuclear energy, as stated in the (1) Naylor, V. D . 'The Critical Flow of a Gas through a Con application of these techniques. Rather, it is vergent Nozzle.' AIRCRAFT ENGINEERING, June 1951, pp. 160-2. original paper. (2) Spalding, D. B. Correspondence. AIRCRAFT ENGINEERING, indeed probable that the overall cost would be Yours faithfully, August 1951, p. 238. increased considerably thereby, by virtue of the (3) Stephenson, J. M. Correspondence. AIRCRAFT ENGINELR- L. N . Thompson ING, August 1951, pp . 238 and 245. multiplicity of rocket vehicles (and hence pro 90 Lansdowne Road (4) Truesdell, C. 'On the Velocity of Sound in Fluids.' Reader^ pellent expenditure) and complexity of techniques Forum, Journal of the Aeronautical Sciences, July 1951, p . 501, Forest Hall (5) Kestin and Owczarek. Correspondence. AIRCRAIT ENGIN involved. The energy required to accelerate a Newcastle-on- Tyne EERING, October 1951. pp. 306-7. satellite rocket from orbital to escape velocity is November 1, 1951 much less than that required to accelerate a DEAR SIR, rocket from rest to escape velocity, but in any My first letter on this subject (AIRCRAFT event energy has to be provided in the first ENGINEERING, August 1951) was written in the instance to bring the satellite rocket up into its hope that the disputed question of the velocity orbit and establish it therein. The achievement of CRITICAL FLOW at the throat might be settled once and for all. a form of space-flight by a combined use of I believe that this has now been done, not admit chemical propellents and sub-orbital techniques To the Editor, tedly by me, but by D r Kestin and Dr Owczarek would still remain very expensive. This latter DEAR SIR, in their admirable letter (AIRCRAFT ENGINEERING, statement has been fully agreed to (in the In the June issue of AIRCRAFT ENGINEERING1, October 1951). 1 agree that my four propositions l.Mech.E. discussion on the paper—see Pro Mr V. D. Naylor states that when the mass flow must be limited to the exit section of a convergent ceedings) by such authorities as Dr Eugen through a convergent nozzle is a maximum, the nozzle, and acknowledge the right of the author to Sanger, one of the world's greatest rocket engin velocity of the gas at the exit is equal to the sonic turn back on me the criticism which I made— eers and originator of the Sanger circum-globular velocity at the exit. He further states that when also with justice I think—of the original proof by supersonic rocket-bomber project and also First friction is present this velocity is V{u—\)CT, Villey. The point is indeed a most singular one. President of the International Astronautical which is smaller than the isentropic sonic velocity I do not withdraw my criticism of Mr Naylor's Federation, and Mr A. C. Clarke, Chairman of V(y— \)C„T. It is on this second point, with paper, however, and am glad to find myself on the BIS itself. which Mr Spalding's argument2 fails to deal, that the same side as Dr Kestin and Dr Owczarek in Mr Cleaver, in support of his proposals, refers we would like to comment. this matter. to a paper by Dr von Braun, but due to space Yours faithfully, Provided Mr Naylor's use of a polytropic effi limitations does not quote any actual numerical D. U. SPALDING ciency is accepted, it is true that the maximum values from this paper. An examination of the Engineering Laboratory discharge will occur when the throat velocity is particular values concerned will justify the state V{it — \)C T. That this is the maximum velocity Trumpington Street, Cambridge ment in the above paragraph. attainable at the throat , however, does not follow October 20, 1951 Dr von Braun's paper outlined a theoretical from the equations. Nor does it follow that the 70-man expedition to Mars, using chemical pro local sonic velocity at the throat is given by this pellents (hydrazine and nitric acid) throughout. expression. There is n o reason to suppose that the The project was t o commence with the assembly M.C.A. INFORMATION CIRCULARS relationship between P and p, which Mr Naylor in a terrestrial sub-orbit of ten 3,720-ton space assumes for the expanding gas stream, also holds The Ministry of Civil Aviation announce the issue ships, over a period of 8 months. To achieve for a superimposed pressure wave at the throat. of the following Information Circulars: this, approximately 1,000 flights by 3-step ground- Ideally, we are concerned with defining the No. 125/1951. U.K. National Airways System- to-orbit supply rockets would be necessary. The conditions under which any disturbance down Departure Delays take-off weight of each of these supply rockets No. 126/1951. U.K. National Airways System- stream will be unable to affect the flow upstream was to be 6,400 tons, and 46 of them were to be Flight Plan'Amendments of the throat. This is the case when the velocity used in relays (semi-expendable construction No. 127/1951. U.K. National Airways System- of the stream becomes equal to that of a pressure being proposed). Airways Clearances wave of whatever amplitude and frequency. Un At the Martian stage of the expedition, several No. 128/1951. Meteorological Specifications fortunately, as Mr Stephenson3 and Professor No. 129/1951. Aeronautical Charts of the main spaceships, and all of the small ferry Truesdell4 rightly state, the speed of propagation No. 130/1951. Ground Controlled Approach rockets carried with them, were to be abandoned. of such a wave can assume various values either (Tcls. 36/51) (G.C.A.) The expense alone, of such a project as the No. 131/1951. Production of Documents by Persons greater or smaller than V(y— 1)C„T; and there is above, would obviously be very great (as indeed Leaving the United Kingdom therefore no unique choking condition for the is admitted by D r von Braun himself), let alone No. 132/1951. The Effect of Frost, Ice and Snow on non-isentropic case. the difficulties of constructing 6,400-ton rockets. Aircraft Performance. Precautions When merely wishing to express stream veloci Even if the scale of the project was reduced by before Take-off ties in non-dimensional form, the consistent use one order of magnitude, i.e. if only one spaceship No. 133/1951. ICAO Radiotclephony Procedures. of any such ratio as vVyRT (Mach number) is carrying seven men was used, the expense would (Tels. 37/51) New Word-Spelling Alphabet 378 Aircraft Engineering
Journal
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Dec 1, 1951