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原文年代久远，所述技巧仅供参考。

Introduction

A great deal of heat is, necessarily, generated by the combustion of propellant in a solid rocket motor. The hot combustion products are under high pressure and must be effectively and reliably contained by the motor casing to ensure the safe operation of the rocket motor. The casing behaves as a heat "sponge", continually absorbing heat, as essentially no heat is transferred from the casing outer surface to the surroundings (under flight conditions, however, some of the heat may be convected to the atmosphere) thereby continuously elevating the temperature of the casing walls over the operating duration of the motor. Fortunately, operating durations are usually quite short, as most structural materials suffer a significant reduction in strength at elevated temperature. Despite the short burn times, some form of thermal protection is usually required for the casing, as a result of the rapid transfer of heat that occurs in the "inferno" of high pressure turbulent flow conditions present in a rocket motor.

固体火箭发动机燃料燃烧过程中必然产生大量的热。高温高压的燃烧产物必须被有效且可靠的限制在发动机壳体内以保证发动机的安全工作。外壳此时如同一块吸热的“海绵”，持续地吸收热量，毕竟几乎没有热量能通过外壳表面传导出去（除了飞行过程中因气流经过产生的非常有限的散热效果），因而壳体温度会不断升高。幸运的是，工作时间通常都很短，毕竟大部分结构材料在高温下强度会显著降低。尽管如此，考虑到……壳体仍然需要某些形式的热防护。

Thermal protection is generally not necessary, however, if all the conditions below are satisfied:

如果以下条件都满足，则不需要做热防护：

1. The motor has a particularly short burn time (typically less than one second)

2. The propellant has a relatively low combustion temperature (e.g. KN based propellants)

3. The casing is fabricated from a material that will not weaken greatly at elevated temperature, and the casing wall is of sufficient thickness such that it is structurally capable of containing the chamber pressure at its reduced strength.

4. 工作时间很短（典型值：<1s

5. 燃料工作温度相对较低（如KN系

6. 外壳由强度不会因高温而过分降低的材料制成，且壳体足够厚，以至于在强度降低之后仍能耐受燃烧室压力

This is the approach that has been taken for my A-100, B-200 and C-400 motors. For all other scenarios, such as my new kAPPA rocket motor), thermal protection of the casing will be necessary. Practical thermal protection for amateur motors can take three forms:

我在我的A-100, B-200和C-400 发动机上都忽略了热防护。除此之外，比如我最新的kAPPA火箭发动机，外壳的热防护就是必须的了。

业余火箭发动机的热防护，有三种实用方案：

1. Layer of thermal insulating (low conductivity) material on casing inside walls

2. Heat sink, which may be as simple as using a thick walled casing of high conductivity material

3. Layer of ablative material which absorbs heat as it burns away (or casing is fabricated from an ablative structural material)

4. 外壳内壁贴隔热材料

5. 散热片。例如发动机壳体采用厚壁高导热材料

6. 烧蚀吸热材料

Item #1 is self-explanatory, which involves installing a heat-resistant liner against the casing inner walls. The low thermal conductivity of the insulator simply reduces the rate at which heat may be diffused into the casing walls. The challenge is to use a material that is sufficiently heat resistant such that it does not simply burn (or melt) away over the operating duration of the motor. Since most practical materials will in fact tend to burn away, it is necessary to size the thickness of the insulating layer such that enough remains to suit the task.

方案1 很简单啦，blahblah挑战在于找到一种材料，热阻足够高且不会在工作周期内烧蚀或者融化。考虑到大部分实用隔热材料都或多或少会被烧蚀，应调整隔热层的厚度以保证有足够余量撑完整个工作周期。

Item #2 is certainly the simplest approach. As will be shown later, materials with a high thermal conductivity (such as aluminum alloys) are capable of rapidly diffusing and "storing" any absorbed heat in such a manner that the overall temperature of the casing will remain reasonably low, as long as sufficient mass (i.e. thickness) is used.

方案2 是最简单的。足够厚的一圈铝合金可以快速吸热。

Item #3 is probably the best approach to thermal protection for motors with high operating (combustion) temperatures and /or long burn times. An ablative material is usually a thermoset plastic or rubber material which decomposes (rather than melts) as it burns away. The material undergoes an endothermic (heat absorbing) degradation shortly after motor start, as the poor conductivity causes the surface temperature to rise rapidly. Pyrolysis gases produced upon decomposition provide additional thermal protection by forming a protective boundary layer.

方案三则最适合那些工作温度高/ 工作时间长的发动机。烧蚀材料通常是热固性塑料或者橡胶材料，它们在烧蚀过程中会分解（而不是融化）。这些材料因为导热不良，表面温度会迅速升高，因而在发动机开始工作后不久就会进入受热分解过程。