United States Patent US3114517A: Microwave Operated Space Vehicles (Raytheon / William C. Brown)

Patent Number: US3114517A Title: Microwave Operated Space Vehicles Inventor: William C. Brown, Western Division, Raytheon Company Assignee: Raytheon Co., Lexington, Massachusetts Filed: May 12, 1959; Granted December 17, 1963 Status: Expired - Lifetime Jurisdiction: United States (US) Source: Google Patents B64G1/409 (Unconventional spacecraft propulsion systems) Track Directory (Physics_Math): N/A — remote microwave power beaming architecture; decoupled energy source paradigm; candidate for a future energy/power delivery track

Image files:

• patents_intl/tweets/raw_download/1962913727885258862_1.jpg (Google Patents abstract page)
• patents_intl/tweets/raw_download/1962913727885258862_2.jpg (full patent text page 1)

Overview

This 1959 Raytheon patent is one of the most consequential entries in this archive. William C. Brown was Raytheon's chief engineer for microwave power transmission and the inventor of the rectenna (rectifying antenna) — the device that converts microwave energy directly to DC electricity with high efficiency. The patent, filed in 1959, applies Brown's microwave power transmission expertise to spacecraft propulsion: a ground or platform-based microwave transmitter beams high-density microwave power to a vehicle, which converts it onboard to electricity powering a propulsion system. The vehicle requires no onboard fuel beyond the conversion electronics.

The patent text reads in part: "This invention pertains generally to space vehicles and the like, and more particularly to a novel form of space vehicle and a system for maintaining such vehicle in flight or at a desired location in spaced-apart relationship with respect to a point on another planet or the like." The prior art section acknowledges earlier systems propelled by carrying their own fuel, and the document explicitly addresses the problem that on-board fuel limits flight duration, operational flexibility, and re-tasking capability.

Physics Mechanism: Decoupled Energy Source via Amplitron-Based Microwave Beaming

Brown's physical claim is that the Amplitron — a relativistic crossed-field microwave amplifier tube capable of high peak and average microwave power output — enables sufficiently intense and coherent microwave beams to power a remote vehicle from distances of kilometers to potentially much larger ranges. The Amplitron achieves this through an interaction between an electron beam and a slow-wave structure in a crossed DC electric and magnetic field: electrons lose kinetic energy to the wave, amplifying the microwave signal with efficiency reaching 85% for pulsed operation. Brown had demonstrated wireless microwave power transmission at practical efficiencies before the patent filing.

Architectural Principle: Decoupled Energy Source

The patent establishes a key architectural principle: decoupled energy source and vehicle. If the ground-based transmitter is nuclear- or grid-powered, the vehicle's operational endurance becomes effectively unlimited. The microwave beam maintains station-keeping against gravity, provides propulsive thrust, and can be steered by varying beam direction. The vehicle's size and mass are reduced dramatically compared to a self-fueled equivalent, because the propellant mass fraction — which in chemical rockets can exceed 90% of gross takeoff weight — is eliminated entirely.

Strategic Significance and International Patent Filing

The 1959 filing date places this concept concurrent with the early U.S. satellite programs and pre-dates the Apollo program by nearly a decade. The patent was licensed internationally: worldwide applications in 1959 (US), 1960 (GB, BE, JP) indicate Raytheon and potentially DoD were actively protecting this IP internationally at a time when the concept would have been directly applicable to classified surveillance vehicle programs. The GB and JP filings are particularly noteworthy, as they extended protection into allied nations' jurisdictions for what would later become a key component of remotely-powered UAV architecture.

The immediate engineering accomplishment of the patent: it describes not merely a concept but a concrete system architecture specifiable in terms of existing 1959 hardware — the Amplitron tube was commercially available, parabolic dish antennas were well-developed, and rectenna arrays were demonstrated by Brown in the late 1950s. Raytheon possessed all the component technologies in-house at the time of filing. The question of whether classified operational versions were built remains open; the patent's existence confirms the technical feasibility was established in 1959.

Sources

• US3114517A on Google Patents (search by patent number)
• Brown, W.C. — Raytheon microwave power transmission and rectenna development, late 1950s

This information was compiled from Break_thrus.mdx staging file.