Explosive or blast-wave accelerators are a member of the class of chemical catapult (artillery gun type) launch systems. In explosive accelerators, a projectile is accelerated either by a high explosive or by hydrogen gas that is compressed by an explosive (Wenzel and Gehring, 1965; Wenzel, 1987). Explosives such as Composition B, Octol, RDX, HMX9404, LX-10 and PBX 9010 are used for their high detonation velocities of 7 – 9 km/s. Examples of this concept include the air cavity launcher, the shaped-charge detonation launcher, the Voitenko implosion gun, and the blast-wave accelerator. The air cavity launcher uses a high explosive to accelerate a small projectile to 5.5 km/s (Clark et al., 1960; Kineke, 1960). The shaped-charge detonation launcher uses a high explosive to implode a conical metal liner, whereby the implosion fuses the liner into a thin liquid jet that accelerates a projectile to 16.5 km/s (Wenzel and Gehring, 1965). And the Voitenko implosion gun uses a high explosive to accelerate hydrogen gas, which in turn accelerates a thin disk to 40 km/s (Voitenko, 1964; Sawle, 1969).
The blast-wave accelerator is chosen as a recommended advanced propulsion concept because of its simplicity and very low system cost. Projectiles are accelerated by a series of hollow explosive rings that are detonated in rapid sequence causing a near-constant pressure to form at the base of the projectile, thereby generating a near-constant and large acceleration (Moore et al., 1965; Rodenberger, 1969; Rodenberger et al., 1970; Bakirov and Mitrofanov, 1976; Voitenko, 1990; Tarzhanov, 1991; Kryukov, 1995; Carrier et al., 1995; Tan et al., 1996; Takayama and Sasoh, 1998; Wilson and Tan, 2001). The gun can have a barrel (launch tube) or explosive rings that are supported by a top beam via inertial confinement (see Figures 4 and 5). The gun’s structure is simple since the principal change required to reload the gun is the replacement of the explosive rings and rudimentary structure. Plastic foam is used in steel launch tube designs to protect the tube from the explosion, and hydrogen gas flows near the tube axis. There are disposable designs that forgo the plastic foam in order to achieve higher hydrogen gas pressure. The projectile accelerations produced by a blast-wave accelerator are moderate compared to the other explosive accelerators. Payloads can have an apogee kick motor attached to circularize their trajectory and enter orbit. The overall system has nominal-to-low cost operation.
The salient features of the blast-wave accelerator (Bekey, 2003):
• This system is a one-stage gun launcher, which can directly place payloads into orbit
• This is a lower-cost launch system that can orbit small dense payloads or multiple modules designed to be assembled in orbit
• This system can launch commodities and small spacecraft with electronics
• This system can ballistically deliver a warhead (oriented projectiles or explosives, undersea homing torpedoes, etc.) or payload anywhere on the globe:
* it can be used as a precision strike weapon with global reach
* it can achieve strike precision at near-orbital speed
* it has artillery-like operations, complexity and cost
* it can be based anywhere
* it possesses excellent stealth (i.e., it has no exhaust plume)
* it has affordability, ferocity, and quick reaction time
• The Blast-Wave Accelerator:
* is of Russian origin
* is a concept that has been verified by NASA studies
* is state-of-the-art technology
• Estimated launch cost: $200 – 2,000/kg of payload, depending on construction and refurbishment options
• 15 m barrel generates 300,000 g acceleration
• 40 m barrel generates 100,000 g acceleration
• Longer barrel generates lower launch acceleration
• Russian experiments indicate that Mach 27 projectile/payload velocity is achievable
• Payload mass fraction is 70 – 95%
It should be noted that experiments have demonstrated that electronic circuits and components (including vacuum tube electronics) can withstand accelerations up to and above 100,000 g and continue to function.
This is an overlooked, promising near-term concept. It does not require the development of new technology or technology risk reduction. This concept has not been in development for reasons involving politics, agenda, legacy, or simple resistance to different ways of doing things. This concept possesses substantial unrealized benefits and it can be implemented right now to meet most unmanned mission requirements.
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