Chemical thermal propulsion

A further special area of propulsion systems is Chemical Thermal Propulsion (CTP). CTP is defined in contrast to STP (solar thermal propulsion) and NTP (nuclear thermal propulsion). In CTP, in a very exothermic chemical reaction in a closed system, heat but no pressure is generated since the products of the reaction are solid or liquid. The heat energy is then transferred to a liquid medium (the propellant) using a heat exchanger, which is responsible for the propulsion of for example, the torpedo. Suitable propellants are e.g. water (the torpedo can suck it in directly from its surroundsings) or H2 or He, due to their very low molecular or atomic masses. The basic principles of CTP can also be used in special heat generators. A good example for a chemical reaction which is suitable for CTP is the reaction of (non-toxic) SF6 (sulfur hexafluoride) with easily liquified lithium (m.p. 180 °C) ... 

For which type of rocket/missile propulsion could chemical thermal propulsion (CTP) be very valuable ... 

Since 1950, plastics have been development for uses in very high temperature environments. By 1954, it was demonstrated that plastic materials were suitable for thermally protecting structures during intense propulsion heating. This discovery, at that time, became one of the greatest achievements of modern times, because it essentially initially eliminated the thermal barrier to hypersonic atmospheric flight as well as many of the internal heating problems associated with chemical propulsion systems. 

Ochoa, F., Eastwood, C., Ronney, P. D., and Dunn, B., (2003) Thermal Transpiration Based Microscale Propulsion and Power Generation Devices, 7th International Workshop on Microgravity Combustion and Chemically Reacting Systems, NASA/CP-2003-21376, 2003. 

In all jet propulsion engines, just as for all propulsion of thermal origin, the source of available energy is an exothermic chemical transformation of solids, liquids, or gases, carried on board and called propellants. For... 

The requirements for selecting a fuel and oxidizer as a liquid bipropellant system are usually a compromise between the demands of the vehicle system, the propulsion system, and the propellants themselves. The vehicle and propulsion system will determine performance levels, physical property requirements, thermal requirements, auxiliary combustion requirements, degree of storability and package-ability, hypergolicity, etc. The final propellant selection must not only satisfy such requirements but is also dictated by thermochemical demands which the fuel and oxidizer make on each other. Frequently, specifically required properties are achieved through the use of chemical additives and/or propellant blending. 

An explosion occurs when a large amount of energy is suddenly released. This energy may come from an over-pressurized steam boiler, or from the products of a chemical reaction involving explosive materials, or from a nuclear reaction which is uncontrolled. In order for an explosion to occur there must be a local accumulation of energy at the site of the explosion which is suddenly released. This release of energy can be dissipated as blast waves, propulsion of debris, or by the emission of thermal and ionizing radiation. 

It can be seen from a review of the synthetic chemistry associated with binder research that significant scientific contributions came from this work. Most of the advanced systems developed, however, have found very limited application in solid propulsion owing to such factors as thermal and shock sensitivity, lower energy than originally calculated, high cost and lack of availability of chemicals, and deficiencies in the physical properties of the polymers prepared. 

Although one might imagine that at USC Simha s interests were focused solely on solution viscosity and statistical thermodynamics, he found time to be involved in such diverse topics as computation of DNA sequences (with Jovan Moacanin from the Jet Propulsion Laboratory), in glass transition phenomena and thermal expansion of polymers (with Moacanin and Ray Boyer of the Dow Chemical Co.), observation of multiple subglass transitions in polymers (with a research associate, Robert Haldon), and thermal degradation (another collaboration with Leo Wall from NBS). 

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