“A base on the Moon can … be used for constant monitoring of the Earth’s surface.” [TASS. 2007 Russian Academician - Boris Chertok Calls for Building Lunar Base. Russian News Agency (August); Burke, K. 2022 Chinese Military Thinking On Orbits Beyond GEO. China Aerospace Studies Institute (August)]

Lunar warfare is a potential exotic battlefield environment characterized by the absence of an atmosphere, and gravity of the Moon is one/sixth that of the Earth. There is potential for direct interaction between Lunar surface combat forces and satellites orbiting above the surface of the Moon, in a combat between opposing forces.

CISLUNAR AND LUNAR SURFACE EXOTIC BATTLEFIELD ENVIRONMENT

A 1965 United States Army Lunar surface weapons study identified it was feasible for an over the horizon attack to be made from the surface from some 320 miles: 514.9 kilometres away. The 1965 Study argued the, “approach … [to] … the problem of Space weaponry should recognize the differences in … [Lunar] … conditions” [United States Army. 1965 The Meanderings of a Weapon Oriented Mind When Applied in a Vacuum Such as on the Moon. Headquarters Weapons Command Rock Island, Illinois (June, 652156)]. The major tactics change posed by Lunar conditions, was the curvature of the Moon (its mean radius 1,080 miles: 1,737.1 kilometres), meaning a Human with an approximate height of six feet: 185 centimetres, was likely to have an unrestricted maximum line of sight some 8,448 feet: 2,574.9 meters away. It was further calculated that a Lunar surface personnel defence weapon, would have the capability to fire a projectile horizontally, reaching a maximum point of impact: impact point, some 8,190 feet: 2,500 meters away. It was concluded, as a result of the high visibility: “A complex set of sights does not therefore appear to be required.” [United States Army, 1965] However, it should be noted that Apollo Astronauts on the Lunar surface frequently reported – “that Sun is bright!”, and it has been concluded in later studies, that Lunar surface, “lighting will create glare and shadow that will overwhelm the ability of Astronauts’ vision to adapt [Cooter, M. 2023 The Visual Experience During EVA at the Lunar South Pole. NASA (July)].

The Lunar surface horizon in relation to the following: (A) maximum over the horizon range: 320 miles (514.9 kilometres); (B) In general terms, a Lunar Orbit is the region of space closest to the Moon, and the Low Lunar Orbits are at altitudes below 100 kilometres [Kurt W. Meyer, et al. 1994 Lifetimes of Lunar Satellite Orbits. NASA Technical Paper 3394, Langley Research Center]; and, the lowest possible orbit around the Moon is a highly elliptical orbit where the orbiting body just barely avoids grazing the surface at its lowest point; (C) maximum line of sight: 8,448 feet (2,574.9 meters); (D) maximum impact point of a horizontal fired projectile: 8,190 feet (2,500 meters); and, (E) maximum ordinate: the highest point of the trajectory, approximately 80 miles: 128.7 kilometres, above the surface; from (F) position of a Lunar surface combatant▼.

▲▲ Lunar orbital altitudes vary radically, due to its topography consisting of high mountains and depressions, and the Moon is the most gravitationally lumpy major body known in the Solar System. Lunar Mascons: mass concentrations, in the upper crust of the Moon alter the local gravity above and around them sufficiently that low and uncorrected Lunar orbits of satellites around the Moon are unstable on a timescale of months or years. Small perturbations in the orbits accumulate and eventually distort the orbit enough for a satellite to impact the surface.

TRANSLATING ORBITAL MANOEUVRE WARFARE CONCEPTS TO CISLUNAR SPACE

Cislunar Space is the region of Outer Space from the Earth out to and including the region around the Moon and its surface. In Orbital Manoeuvre Warfare terms, “spacecraft can operate in various trajectories in Cislunar Space including Lunar orbit, trans-lunar trajectories, and in families of orbits in the regions of Space around Earth-Moon Lagrange points.” [Berkowitz, M. Williams, C. 2023 Strategic Implications of China’s Cislunar Space Activities. National Security Space Association (21 August)] When looking at the potential to translate Orbital Manoeuvre Warfare concepts to Cislunar Space, commentaries have stated:

“China has demonstrated everything it would need to execute co-orbital counter-space operations across the entirety of Cislunar Space: navigation, command and control, Rendezvous and Proximity Operations, and docking in Lunar Orbit, complex navigation and manoeuvring between Cislunar and Solar regimes.” [Goswami, N. Bowen, B. Wilson, R.S. 2024 High Ground or High Fantasy: Defense Utility of Cislunar Space. Center For Space Policy and Strategy. Debate Series (May)]

Historically, the 1961 United States Airforce Lunex Launch Complex, in addition to a Lunar Base also envisaged: “military facilities may have been established … in orbit around the Moon.” [United States Airforce. 1961 Lunar Expedition Plan (Lunex). Headquarters Space Systems Division, Air Force Systems Command (May)] The notion of a Circumlunar Orbital Military Facility was also found in the 1959 United States Army Project Horizon Report, which had an Intermediate Orbiting Space Station [United States Army. 1959 Project Horizon Report: A U. S. Army Study for the Establishment of a Lunar Outpost. Volume I: Summary and Supporting Considerations (9 June)]. Used initially to establish a Lunar Base, it was to be used as a Space assembly point orbiting the Moon. From this, a Space Transport Vehicle was envisage being used to ferry payloads to the Lunar surface. The 1959 Army Report  proposal had a plan for 252 Soldiers in Earth Orbit by the end of 1967 [Borch, F.L. 2021 Soldiers on the Moon?!? The Army’s Strange but True Plan for a Lunar Outpost. The Army Historical Foundation]. It was planned that a detail – estimated to be some 42 Soldier-Astronauts would continue onto the Moon for their tours of duty. Some 26 Soldier-Astronauts would then return from the Moon (leaving the Task Force of up to 12 to do their tour at the Lunar Base). The stopping-off point would be the Intermediate Orbiting Space Station before returning home to Earth.

The United States Army planned for Soldier-Astronauts to do a tour of duty on the Moon not exceeding one year. In terms of force options, this arrangement appears to have created two reserve forces: (1) A large force: some 200 Soldier-Astronauts on the Earth Orbiting Space Station (some two-three days flight from the Moon); and, (2) a second force of 12 or more Soldier-Astronauts on the Intermediate Orbiting Space Station (awaiting their return-flight to Earth). This arrangement would have given three potential United States Army forces of Soldier-Astronauts, who could be directed towards Lunar military operations, if the situation there was to have escalated for any reason, such as fending-off an attack▼.

CISLUNAR SPACE PATROLLING (CISLUNAR SPACE SITUATIONAL AWARENESS/SPACE DOMAIN AWARENESS)

‘Cislunar Space Patrolling’ is a notional Space Situational Awareness/Space Domain Awareness technology concept for Cislunar Space, where a Moon orbiting satellite is used. A case for Cislunar Space Patrolling is based on the lack of reach of Earth-based Space Situational Awareness/Space Domain Awareness as its furthest reach is Geosynchronous Orbit. For instance, it is possible to place a satellite in retrograde orbit in Geosynchronous Orbit via the Moon [Goswami, 2024]. The orbital advantage is that within 12 hours, it can not only provide early debris warning but also inspect (or target) every other Geosynchronous Orbit satellite … [in a potential surprise move]” [Goswami, 2024]. A 2022 technology concept known as the Cislunar Highway Patrol System: CHPS, has been described as:

“a spacecraft conceived at the Air Force Research Laboratory Space Vehicles Directorate that is designed to improve the United States Space Force’s ability to detect track and identify artificial objects operating at Lunar distances and beyond, a range of 385,000 kilometres. Most Space Force sensors are designed to detect and track satellites that are in Geosynchronous orbit (~36,000 kilometres) distances or closer.” [Air Force Research Laboratory [The]. 2022 Space Domain Awareness Mission Beyond Geosynchronous Earth Orbit (GEO): Cislunar Highway Patrol System (CHPS). Fact Sheet]

▲ A potential model for Cislunar Space Patrolling with a Lunar Orbit Patrol Craft. This is a Cislunar Space Situational Awareness/Space Domain Awareness technology concept where a Moon orbiting satellite is used. A case for Cislunar Space Patrolling is based on the lack of reach of Earth-based Space Situational Awareness/Space Domain Awareness, which uses a combination of active radar and optical tracking. As its furthest reach is Geosynchronous Orbit, there is likely to be a requirement to have Cislunar Space Situational Awareness/Space Domain Awareness by placing a manoeuvring satellite in Lunar Orbit (rather than have this located on the Moon’s surface). The patrol satellite would require an additional motor and fuel (another replaceable craft mated with the satellite), in order to allow for multiple orbital adjustments. It has been suggested the patrol satellite could be placed in Geosynchronous Orbit via the Moon providing not only early debris warning, and inspection of other Geosynchronous Orbit satellites. Coming from the Moon direction this could provide orbital tactical surprise.

SPACE DOMAIN AWARENESS SATELLITE

In September 2023, the United States Space Force launched its Silentbarker - a Space Domain Awareness Satellite. The role of the satellite is to meet the Space Force’s, “insatiable need for awareness of activity in Space in order to identify and track potential adversaries through a proliferation of its own architectures on orbit.” [Everstine, B. 2024 U.S. Space Force Seeks More Sharing of Situational Awareness Data. Aviation Week (4 March)] A 2023 statement about Silentbarker’s role – which is also part of a space monitoring constellation that ‘watchdog’ in Geosynchronous Orbit:

“What Silentbarker is going to do is provide … indications and warnings so it can inform decisions about what we do or don’t need to do in terms of manoeuvre or awareness. So, it’s a great increase in our understanding of what we’ll be able to do and will greatly improve our ability to determine future courses of action” [Hitchens, T. 2023 Silentbarker ‘Watchdog’ to be ‘Exponential’ Leap in DoD Monitoring of Chinese, Russian Sats. Breaking Defense (31 August)].

Silentbarker join five other Geosynchronous Space Situational Awareness Program (GSSAP) satellites, “currently undertaking on-orbit inspections to augment U.S. Space Command’s ground-based radar and telescopes for monitoring the heavens.” [Hitchens, 2023] In terms of potential Orbital Manoeuvre Warfare concepts, it has been recently theorized an attack like blinding a Space Domain Awareness Satellite while executing another Co-Orbital Antisatellite Weapons attack would operate as a deception operation, that could greatly increase the opponent’s chance of a successful attack [Suss, J. 2024 Asymmetric Warfare in Space: Five Proposals from Chinese Strategic Thought. Æther: A Journal of Strategic Airpower & Spacepower. Volume 3. Number 1 (Spring)].