The problem of air-breathing engines capable of flying at very high Mach numbers is described briefly. Possible performance of supersonic combustion ramjets is outlined briefly and the supersonic combustion process is described. Two mechanisms of combustion are outlined: one is supersonic combustion controlled by convection process, and the second is controlled by diffusion. The parameters related to the combustion process are discussed in detail. Data and analyses of reaction rates and mixing phenomena are represented; the flame mechanism is discussed, and experimental results are presented.

From some points of view this is a difficult time to be giving a general talk on supersonic civil transports. The pioneering period is over, and the really interesting lectures when bright new ideas and shapes were discussed have mostly all been given. The design of the Anglo-French “Concord” is now pretty well settled and a fair amount of information about it has been made public. The information which has not been made public is withheld for obvious reasons of commercial security, and I am therefore caught between not giving too much away on the present Concord and repeating a lot which has already been said.

There is not a great need for the further reductions in flight time that can be afforded by the SST over the near-sonic jets. Furthermore, the time gain by the SST will be counteracted by reduced in-flight comfort and, on the average, by an increasing difference in airport distance between supersonic and competing subsonic services. Nevertheless, most businessmen in a great hurry and some tourists are likely to prefer the SST on conveniently scheduled flights and at equal fares.

However, for utilisation reasons only some of the SST flights can be conveniently scheduled and the SST's will—for 15 specified reasons—be so grossly uneconomical in competition with subsonic aircraft that the condition of equal fares cannot be complied with without exceedingly high subsidies to be covered by the taxpayers in all SST-operating countries. The subsidies must continuously increase mainly because of

—improvements of competing subsonic aircraft in operating cost—and ability to use more centrally located airports and

—increasingly adverse sonic-boom reactions (as the operation grows and the SST's, as is normal, become heavier and create higher boom intensities) by people on the ground, including potential SST passengers.

As the SST enterprise will thus be an economic failure, most of the aspects that are claimed to be advantageous in the event of an SST success, in particular prestige and improved national economy, will instead turn into pronounced disadvantages: loss in prestige and an economical burden.

Over and above this, supersonic aviation will

—most likely be much less safe than subsonic aviation,

—possibly subject passenger and crew members or their off-spring to harmful effects of cosmic radiation,

—seriously counteract, probably make impossible, the urgently needed improvement of flight safety in aviation,

—hamper the brilliant prospects now in sight for making aviation a really cheap and convenient means of mass transportation, and

—retard the expansion of civil aviation.

People in general are prepared to put up with a certain amount of noise—in confined areas and mainly during the working hours of the weekdays—if it is an inevitable by-product of a necessary, an important, or a profitable activity. But supersonic aviation, which will cause serious noise disturbances day and night, 365 days of the year, in unprecedently vast areas, is neither necessary, nor very important, nor profitable. Thus, the introduction of supersonic flight would mean that hundreds of millions of people would not only be seriously disturbed by the sonic booms, often to an extent detrimental to health, but also have to pay out their own money to keep the noise-creating activity alive, and in addition, have to accept a much less safe and cheap civil aviation than would otherwise be possible to achieve.

Therefore, the consequences are such that, once the supersonic era has begun, the general public will always strenuously oppose it. There will be an unprecedented tension between aviation and the public. Intense efforts will certainly be made to switch back to all-subsonic aviation. The cost of such a reversion will be fantastic and rapidly grow the longer the supersonic era prevails.

Obviously, it lies in the best interest also of civil aviation to prevent introduction of supersonic flight in its presently suggested form.

During the past ten years the author has been collecting test data on the collapse of pressure loaded spherical shells in order to establish good design curves. The presence of initial imperforations causes wide variance in strength values from one investigator to another. An effort is undertaken to attempt to analyse all available data on some rational basis. Certain diagrams have been presented in the past.

The problem of combustion pressure oscillation in liquid-fuel rocket motor operation has long been the subject of theoretical and experimental investigations.

The low frequency (less than 200 cps) type of oscillation, known as “chugging”, has been thoroughly analysed and the problem solved (see Crocco, 5th Combustion Symposium, p. 164).

This Note is concerned with the more complex (and more destructive) high frequency oscillations, covering a range from about 1000 to 6000 cps. Such oscillations can resonate with the acoustical modes of the combustion chamber. Longitudinal, tangential and radial oscillating modes have been observed.