Notional RLV-4 Cargo vehicle in a distant Near Rectilinear Halo Orbit awaiting depot refueling before transporting a multilevel Lunar Regolith Habitat to an outpost at one of the lunar poles.

by Marcel F. Williams

Privately financing the development of a reusable SLS deployed lunar landing vehicle should be a priority for the major Space Launch System partners: Boeing, Lockheed Martin, Aerojet Rocketdyne, and Northrup Grumman. A reusable single stage LOX/LH2 fueled vehicle (RLV-4 Crew) could be commercially successful as a crew lander by simply adding a-- pressurized habitat module-- already being developed by Lockheed Martin for the Blue Origin National Team.

Notional RLV-4 Crew vehicle with Lockheed Martin derived habitat module with crew deployment davit system.

By financing a single stage vehicle rather than a two stage vehicle, development cost could be substantially reduced by simply developing one vehicle instead of two. Further cost reductions could result from using engines and propellant tank technology that already exist. So a notional RLV-4 could use RL-10 derived CECE engines already developed by SLS partner Aerojet Rocketdyne and super lightweight composite propellant tanks already developed by Boeing.

I envision the RLV-4 Crew and RLV-4 Cargo vehicles going into operation by the year 2026. If we assume a development cost of $6 billion for the RLV-4 over the course of six years, then each SLS partner would be required to supply at least $250 million a year of funding for the development of the reusable RLV-4.

Notional RLV-4 Cargo vehicle capable of being filled with up to 56 tonnes of LOX/LH2 propellant.

Similar to the RLV-4 Crew vehicle, I envision the RLV-4 Cargo as being launched-- in pairs-- within the 9.1 meter in diameter dynamic envelope of a 10 meter in diameter SLS payload fairing. At its corners, the maximum diameter of the RLV-4 octagon would be 8.44 meters with a distance between each opposite 3.23 meter side of the octagon being approximately 7.8 meters. With the legs folded during launch, the RLV-4 could easily fit within the internal 9.1 meter in diameter dynamic envelope of the 10 meter in diameter SLS payload fairing.

Each RLV-4 Cargo vehicle would weigh approximately 8 tonnes. The 10 meter in diameter payload fairing would add an additional 10 tonnes in weight headed for orbit. Since an SLS Block I would be capable of deploying up to 70 tonnes to LEO, up to 44 tonnes of propellant could be added to one of the vehicles in preparation for a mission.

Alternatively, one RLV-4 Crew vehicle could be launched with one RLV- 4 Cargo vehicle. Before launch, the crew vehicle would be filled with enough propellant to transport a crew to NRHO. The cargo vehicle would simply remain in orbit at LEO until its ready to dock with a payload and be fueled for a mission.

The reusable RLV-4 Cargo vehicle would be able to dock securely with large payloads (up to 10 meters in diameter) subsequently deployed to LEO by the SLS. Payloads deployed to orbit by the SLS would be equipped with flat standardized docking bases configured to securely join with the octagonal payload floor of the RLV-4. Propellant depots deployed to LEO, NRHO (Near Rectilinear Halo Orbit) and eventually on the lunar surface would be used to fuel and refuel the RLV-4 Cargo vehicles.

Octagon shaped payload floor of notional RLV-4 Cargo vehicle.

Fueled at LEO with up to 56 tonnes of propellant, the RLV-4 could deploy up to 10 tonnes of cargo to the lunar surface. Alternatively, the RLV-4 could transport up to 30 tonnes of cargo to NRHO where it could then be refueled to transport its 30 tonne payload to the lunar surface.

If the SLS deployed payload has an upper attachment area that could allow an additional RLV-4 to dock then two RLV-4 Cargo vehicles could be utilized for a single cargo mission. This could allow up to 60 tonnes of payload to be transported to NRHO. A single fully fueled RLV-4 Cargo vehicle could deploy up to 50 tonnes of payload to the lunar surface. But two vehicles would be required to deliver a 60 tonne payload to the surface. One vehicle would only travel to lunar orbit and then back to NRHO while the second vehicle would travel to the lunar surface with its 60 tonnes of payload.

So the reusable RLV-4 cargo system would be capable of delivering 10 tonnes to 60 tonnes of payload from the lunar surface from LEO. And that means the SLS could deploy up to 60 tonnes of payload to the lunar surface with a single launch if it used a reusable RLV-4 Cargo transport system.

Notional RLV-4 Cargo deployed lunar crane for unloading large cargo and for lunar regolith deposition.

Large lunar cranes might be one of the most valuable initial payloads for the RLV-4 Cargo. Using a davit system, a pair of large cranes could be deployed to the lunar surface. Such electric or hybrid electric (pressurized hydrogen fuel cell/battery) vehicles could be used to unload large and heavy payloads from a large variety of lunar landing craft. If we assume that each lunar crane weighs at least 8 tonnes, lunar regolith could be used to provide an additional 24 tonnes of counter weight. So each lunar crane should be capable of offloading more than 30 tonnes of payload. However, if the iron and other metals that inherently exist within lunar regolith are magnetically extracted to increase the counterweight capabilities of lunar regolith then payloads weighing more than 60 tonnes could be unloaded. Lunar cranes could also be used to deposit regolith within the surrounding walls of large habitats and within the foundation floor for inflatable biospheres and surrounding bio-tori.

RLV-4 Cargo vehicle carrying twin lunar regolith cranes to be deployed to the lunar surface using davit system.

Pressurized 8.4 meter in diameter cylinders derived from SLS propellant tank technology could provide multilevel habitats for the lunar surface up to 20 meters tall if deployed within an SLS 10 meter in diameter payload fairing. With a self deploying regolith walls, lunar cranes could provide appropriate radiation shielding by simply dumping lunar regolith within the cavity of the surrounding wall.

Lunar regolith crane about to remove a Lunar Regolith Habitat from a RLV-4 Cargo vehicle.

But even longer 8.4 meter in diameter cylinders could be deployed to the lunar surface after being to deployed to LEO by the SLS. 40 meter habitats could be deployed to the lunar surface using the RLV-4 Cargo. Such habitats could be unloaded by large lunar cranes and deployed horizontally to the lunar surface and then covered with lunar regolith bags. The use of the larger horizontal habitats for agriculture could even allow for the growing of orchard trees for the production of apples, oranges, peaches, lemons, etc. The horizontal habitats could also be used for aquaculture, raising shrimp, crabs, fish, clams, etc.

X-Ray of an SLS propellant tank technology derived Lunar Regolith Habitat

If the RLV-4 Cargo is used to deploy inflatable Kevlar biosphere and bio-tori then substantially larger habitats could be deployed. 50 meter in diameter Kevlar biospheres that are pressurized with half the atmospheric pressure on Earth could easily be deployed to the lunar surface by an RLV-4 Cargo. An additional SLS launch would be required to launch the surrounding 25 meter wide bio-torus. And another SLS launch would be required to deploy the expandable connecting tunnel and regolith base for the biosphere and bio-torus on top.

A 15 meter high SLS deployed lunar regolith hab might provide five spacious 8.4 meter in diameter habitat floor levels (55 square meters per floor).

But the bottom half of a 50 meter in diameter biosphere could provide up to 9 habitat levels with each floor averaging about 25 meters in diameter (490 square meters per floor). That would be up to 16 times the floor area for just the bottom half of the biosphere. The upper half of the biosphere (the biodome) would provide the astronauts, military personal, and guest with spacious recreational area with a ceiling up to 25 meters high. Such an area could easily accommodate a large circular recreational swimming pool 30 meters in diameter. This might also be room enough to strap on a pair of wings and fly about within the 50 meter wide biodome. The surrounding bio-torus or tori could be used for agriculture and aquaculture and storage.

Notional lunar biosphere and bio-torus covered with regolith bags and connected to twin Lunar Regolith Habitats on the sintered surface of a lunar outpost area.

Once propellant is being produced on the lunar surface, extraterrestrial vehicles like the RLV-4 crew should make it substantially cheaper to travel to the lunar surface after departing the Earth's surface aboard a commercial crew vehicle. If a lunar habitat was deployed to the lunar surface and utilized as a hotel for astronauts, tourist, and military personal, the owners could reasonably charge its guest perhaps $10 million each for a 30 day stay. This, of course, doesn't include the cost of the round trip from Earth to the Moon. If we assumed that an individual habitat was continuously occupied by at least 4 to 8 personal (astronauts, military personal, tourist) then an individual habitat could make between $480 million to $960 million per year in revenue. With up to 16 times the floor area for the bottom half of a biosphere, a single biosphere/bio-tori complex could make more than $15 billion a year in revenue if it were continuously fully occupied with up to 128 people. Providing water, food, and air for the lunar guest would be insignificant if such resources are derived from ice and carbonaceous and nitrogenous resources in the lunar regolith at the poles or from similar resources deep within lava tubes. Assuming a minimum 20 year lifetime for such habitats, such SLS deployed facilities should be highly profitable.

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