| 摘要 |
<p>A projectile traversing the lower atmosphere at hypersonic speed suffers high aerodynamic drag. This may be reduced by preheating the air ahead of it to create a 'plasma tunnel', within which the temperature is raised to several times the ambient with a corresponding reduction in density, reducing the drag force. Typically, overall drag may be reduced by a factor of 10-100 in this way. The heating may be accomplished in several ways. For example the projectile may be equipped with a prove attached to the nose through which liquid is sprayed. The liquid is brought to rest by the surrounding air, converting its kinetic energy to heat. A particular application is to electromagnetic space launch systems. A projectile accelerated to orbital or escape velocity at ground level by linear accelerator can traverse the atmosphere with acceptable speed loss.</p> |
