Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

# UNCLASSIFIED

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Projections and modelling claim a Mach 5 capability, to 100,000ft altitude. The laser provides thermal energy (collected from the beam) and used to produce air-breathing thrust. At altitude, conventional rocket fuels would be used to boost to escape velocity.

## MICROWAVE PROPULSION

28. Low frequency microwave beams are not suitable for on-board energy collection. The problems are those of diffraction, and the requirement for large antennas on board the vehicle. Also, the low breakdown threshold of the atmosphere limits the received power density. The selection of high frequencies is limited by the EM atmospheric windows (e.g. 34, 94, 140 or 220GHz). Atmospheric attenuation also increases with increased RFs. It is assessed $ ^{1} $ that a 15m diameter craft could logically use a 35GHz system with the high power rectifying antenna ('rectenna'), which is a solid state converter. Within the atmospheric propagation breakdown limits $ (4\mathrm{KW c m}^{-2}) $ this antenna could receive $ \sim 5. 6 \mathrm{G W}. $ At an RF of 200 GHz Benford and Myrabo $ ^{2} $ , suggest an array of focused 10KW gyrotrons could provide a launch station. With the overall power assessed at 30MW a huge 550m diameter array would be required to ensure adequate energy (10MW on a one meter diameter receive antenna), reaches the vehicle at the extremity of the atmosphere because of the extinction loss en-route (even using the 220GHz atmospheric 'window'). Conceptually, a space-based, (LEO) passive relay station could be used to pass the EM energy beamed from a terrestrial station onto the vehicle in space, where the energy would be converted this time for use in an ion thruster engine.

29. It is beyond the scope of this report to include fine details of the design of such a craft other than to list the key features which might have a bearing on the potential UAP

connections in answering the enigmatic question - "Can a craft capable of extra terrestrial travel with the reported characteristics be conceived within the limits of 'earthbound' capabilities"? The key features follow with UAP-related comments in square brackets

(a) Size The microwave craft proposed has a 15m diameter. [This falls within some reported UAP diameters].

(b) Mass A launch mass of 1400Kg is proposed (surface area loading $ 7. 9 \mathrm{K g}. \mathrm{m}^{2} $ ). This is an aerodynamic (e.g. wing) loading similar to that of ultralight aircraft. This leads to the conclusion that every conceivable means must be used to lighten the mass even to the point of carrying no propellant - hence the idea of using a microwave-induced 'air spike' and beamed energy sources. The point that immediately diminishes the UAP connection here is that energy conversion is used and atmospheric thrust is produced. Hence, there will always be, as far as can be deduced, some type of acoustic effect. [In other words an observer will hear very loud sounds, contrary to UAP reports] However, if it is possible to place all the electromagnetic air acceleration technology on the outside of the body this may not be the case.

(c) Materials Thin film materials with adequate tensile and compressive strength could, conceivably, be made. Silicon Carbide based materials (exotic fibres) have been suggested. The thin film materials might be microwave-reflective, acting simultaneously as the rectenna. Any collected spare power could be used, for example, to power the air-spike.

(d) Propulsion Several propulsion configurations have been proposed. The first is the pulsed detonation engine (PDE), or microwave-thermal