Every patent that touches a spacecraft carries a classification code, and for cosmonautics that code begins with B64G. The Cooperative Patent Classification (CPC) — the shared scheme jointly maintained by the U.S. Patent and Trademark Office and the European Patent Office — assigns B64G to the subclass it titles, verbatim, "Cosmonautics; vehicles or equipment therefor." When an examiner classifies a satellite-bus, launch-vehicle, docking-mechanism or space-suit invention, this is the bucket it lands in. For anyone trying to read the space industry's research footprint from the patent record, B64G is the front door: a single subclass query returns the spacecraft corpus that keyword searches scatter and miss.

The subclass is not a flat list. CPC organizes B64G into a small set of top-level main groups, each ending in /00, that partition the field by function. According to the published CPC scheme (version 2026.05), the groups are: B64G 1/00, "Cosmonautic vehicles"; B64G 3/00, "Observing or tracking cosmonautic vehicles"; B64G 4/00, "Tools specially adapted for use in space"; B64G 5/00, "Ground equipment for vehicles, e.g. starting towers, fuelling arrangements"; B64G 6/00, "Space suits"; B64G 7/00, "Simulating cosmonautic conditions, e.g. for conditioning crews"; and B64G 99/00, "Subject matter not provided for in other groups of this subclass." Each main group then branches into more specific dot-indented subgroups — B64G 1/40 and its children, for instance, gather propulsion and reaction systems for spacecraft.

"B64G — COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR. This subclass covers only vehicles able to leave the earth's atmosphere."— Cooperative Patent Classification, B64G scheme, USPTO CPC

That scope note matters more than it looks. By stating the subclass "covers only vehicles able to leave the earth's atmosphere," CPC draws a hard line between space and aeronautics. Aircraft, drones and atmospheric vehicles fall under sibling subclasses B64C (aeroplanes; helicopters), B64D (equipment for fitting in or to aircraft) and B64U (unmanned aerial vehicles). A reusable launch vehicle gets B64G when it is acting as a spacecraft; an air-breathing first stage may pull additional aeronautics codes. This is why a B64G search and a keyword search for "rocket" return different sets — the classification encodes a functional judgment the examiner made about what the invention actually is.

How the deeper groups work

The richest activity sits inside B64G 1/00. Its subgroups separate the spacecraft into its engineering systems: B64G 1/10 covers artificial satellites and systems of such satellites; B64G 1/22 covers vehicle parts or details; B64G 1/24 covers guiding or controlling apparatus; B64G 1/40 covers reaction and propulsion arrangements, with B64G 1/405 specifically tagging electric propulsion. A single granted patent commonly carries a dozen or more CPC codes at once — one primary classification plus a cascade of secondary codes describing each subsystem the claims and disclosure touch. That multiplicity is a feature for analysts: it lets a portfolio map distinguish a propulsion filing (B64G 1/40-series) from a thermal-control filing (B64G 1/50-series) from an attitude-control filing, even when both companies describe their work as simply "satellite technology."

Classification is also assigned, not chosen. The applicant does not select B64G; the patent office's classification staff and the examiner do, based on the disclosure. That makes CPC a relatively neutral lens on what an invention covers, independent of the marketing language in a press release. It also means classifications can shift as the scheme is revised — the bracketed dates in the scheme (for example, B64G 3/00 carries a [2024-01] revision marker) record when a group was introduced or amended, so a longitudinal filing-trend analysis has to account for codes that did not exist in earlier years.

Why B64G is the search anchor

For competitive-intelligence and whitespace work, B64G converts a vague question — "who is building spacecraft technology?" — into an answerable one. Pulling all grants and publications classified under a specific subgroup, faceted by assignee and year, surfaces filing velocity by company and by subsystem. A rising count in B64G 1/64 (apparatus for assembling or maintaining spacecraft in space, i.e. servicing and docking) reads as on-orbit-servicing investment; concentration in B64G 1/24 reads as guidance and control. Because the classification is consistent across the U.S. and Europe, the same query crosses jurisdictions. The crossover codes are equally informative: a constellation patent frequently pairs B64G with H04B7 (radio transmission to or from satellites) or H01Q (antennas), and a defense-adjacent spacecraft filing can pull G01S (radar, sonar, lidar) alongside B64G. The pairings themselves describe what the invention does at the system level.

A worked example shows the leverage. The Boeing all-electric propulsion grant U.S. 10,689,132 B2 carries B64G 1/405 among its codes — the subgroup for electric propulsion arrangements for spacecraft — sitting alongside B64G 1/242 (solar arrays as power source), B64G 1/26 (guiding or controlling apparatus by jet reaction) and B64G 1/40 (the parent propulsion group). Reading that code string tells an analyst, before opening the claims, that the document concerns an electrically propelled, solar-powered spacecraft with jet-reaction control. No keyword search reconstructs that subsystem-level picture reliably, because the same disclosure might never use the words "reaction control" in its abstract. The classification encodes the engineering taxonomy that the prose leaves implicit, which is exactly why a portfolio map built on CPC codes resolves a company's research into systems rather than buzzwords.

None of this tells you whether a patent is broad or narrow — that lives in the claims, not the classification. What B64G gives you is reliable recall: a way to gather the right set of documents before reading any of them. For a field where the same capability is described a dozen different ways in plain English, the classification is the common language the patent record actually speaks. Start a spacecraft patent search at the keyword and you will miss filings; start it at B64G and you have the population, ready to be narrowed by subgroup, assignee and date.