The Fastest, Safest, and Most Economically Sustainable Way to Return to the Lunar Surface

by Marcel F. Williams

 “I’m taking nothing off the table, and we’re not compromising safety. Anything we don’t need to do we can delay. There’s future launches, there’s future things we can test, but right now, how do we get boots on the moon in 2024?”  (NASA Administrator Jim Bridenstine)

It is now a directive of the Executive Branch of the United States for American astronauts to return to the surface of the Moon by 2024. But the type of transportation infrastructure developed for a US return to the lunar surface could largely determine whether, or not,  America will strategically and economically dominate the Moon, cis-lunar space, and the rest of the solar system.

It is estimated that between 100 million to one billion metric tons (tonnes) of water ice may exist at the Moon's north and south poles. Exploiting polar ice deposits on the lunar surface for the production of rocket fuel is one of the principal arguments for returning to the Moon. Lunar hydrogen and oxygen propellant would make it much easier to send humans to Mars. And lunar propellant and propellant dept technology  could also give astronauts easy access to the surfaces of Mercury and Jupiter's Galilean moon, Callisto, two additional worlds that could be potentially colonized by humans someday. 

Liquid oxygen comprises nearly 86% of the mass of LOX/LH2 propellant and nearly 89% of the mass of water. So even if there were no ice deposits on the Moon, the extraction of oxygen directly from the lunar regolith would provide humans with an almost endless supply of oxygen for utilization as propellant.

So any reusable spacecraft developed to return humans to the surface of  the Moon should also be inherently designed  to utilize potential lunar propellant resources-- once such lunar resources become available. But until lunar ice and regolith resources can be exploited hydrogen and oxygen, or water,  will have to be launched into cis-lunar space from the Earth's surface.

The primary purpose for a Lunar Gateway at NRHO (Near Rectilinear Halo Orbit) is to make it simple and easy to routinely visit the lunar surface from that delta-v bridging location. Yet NASA is currently advocating  a highly complex and inherently more dangerous transportation infrastructure to operate out of the NRHO Gateway. NASA's current gateway transportation architecture requires two or three different spacecraft in order to transport astronauts on a simple round trip between NRHO and the lunar surface. And the elements are not even completely reusable.

Notional  Lockheed Martin reusable lunar landing spacecraft on the lunar surface (Credit: Lockheed Martin)

Lockheed Martin, on the other hand, has proposed a simple--  single stage-- spacecraft that can operate out of NRHO. And its completely reusable. The Lockheed Martin's reusable spacecraft concept is derived from the ULA's future Centaur V and ACES rocket technologies. These cryogenic oxygen and hydrogen fueled upper stages will be used in the ULA' new Vulcan rocket system-- which is supposed to go into operation in 2021.


Lockheed Martin's Notional  Reusable Crewed  Lunar Landing Vehicle

Propellant: 40 tonnes of LOX/LH2

Inert Weight: 22 tonnes

Engines: Four RL-10 derived engines

Maximum delta-v capability: 5.0 km/s

Maximum number of crew: Four


Two of the 22 tonne Lockheed Martin lunar landing vehicles, which I will refer to as the R-LL (Reusable Lunar Lander), could easily be deployed to LEO by a single Block I SLS launch within the 8.4 meter (7.5 meter internal) payload fairing equipped with an extra barrel section.  The notional lunar spacecraft, however, would have to be fueled by propellant depots. But propellant depots would be essential if NASA is really serious about exploiting lunar resources to produce hydrogen and oxygen. So there's no logical reason not to develop cryogenic depots now!

The optimal propellant depot design would be a-- water depot-- that simply uses solar electricity to convert liquid water into hydrogen and oxygen though electrolysis and then into liquid hydrogen and oxygen through cryo-refrigeration. However, much simpler depots could be directly derived from the propellant tanks of  existing  upper stages and could utilize NASA's new helium or nitrogen cryorefrigeration technology.

Propellant could be easily transferred to a spacecraft by docking the spacecraft to the propellant depot, automatically connecting the spacecraft fuel hoses, and then firing thrusters to create simulated gravity through acceleration. Useful acceleration for propellant transfer  can be as little as 0.00004 g.

Both water and propellant could be easily deployed to LEO and NRHO by commercial launch vehicles. The Falcon Heavy should be able to deploy more than 15 tonnes of propellant to NRHO and the future Vulcan Heavy rocket systems should be capable of routinely deploying more than six tonnes of propellant to NRHO per launch.  Monthly propellant launches by each system could deploy enough liquid hydrogen and oxygen to NRHO for at least six R-LL round trips to the lunar surface  per year. NASA only sent astronauts to the moon six times from  1969 to 1972 during the entire Apollo program. 

Lightweight, disposable, propellant tank derived from Centaur 3 LOX tank capable of storing 26 tonnes of liquid oxygen (Credit: ULA)

If the R-LL uses ULA's future IVF technology, then only hydrogen and oxygen would have to be transported to NRHO. However, if the R-LL uses existing Centaur rocket technology then gaseous helium will also have to be deployed to NRHO. While the helium itself would represent less than 2% of the total propellant mass, the tanks needed to deliver the helium to NRHO would be heavy and would require the helium to be  launched to NRHO by a  Falcon Heavy or Vulcan Heavy rocket. But using IVF technology would, obviously, make the R-LL simpler to fuel.

Much larger depots, directly  derived from the ULA's Centaur V or ACES upper stage rockets, could be deployed to LEO with the ability to self deploy themselves to NRHO. Such vehicles could store up to 68 tonnes of LOX/LH2 propellant.  So Falcon Heavy and Vulcan Heavy launches to NRHO could transfer their propellant directly to the large depots for long term storage. Reusable ACES tankers could also transport propellant originally deposited by commercial launchers to LEO to NRHO. This could allow technology such as Boeing's Phantom Express to continuously deploy propellant to LEO that could later be exported to NRHO.

Total mass of a water or propellant  that can be deployed to LEO via daily launch of a single Phantom Express space plane:

Daily - 1.36  to 2.27 tonnes

Monthly - 40.8  to 68.1 tonnes

Yearly - 496.4  to 828.6 tonnes 

Yearly amount of water or propellant that could then be transported by reusable ACES spacecraft to NRHO by a single Phantom Express space plane:  200 to 330 tonnes     

Once lunar water and propellant are being manufactured on the lunar surface then the R-LL could also be used as a reusable lunar tanker. Simply replacing the crew transport module with a water tank,  a single R-LL tanker could transport more than 40 tonnes of water to NRHO from the lunar surface. And after 12 round trips, a single  R-LL tanker could deploy more than 480 tonnes of water to NRHO before its RL-10 derived engines would have to be replaced.

Of course, propellant depots deployed to both LEO and NRHO would also make it easy for reusable spacecraft to travel between LEO and NRHO. So an Orion/ACES spacecraft could eliminate the need of using a super heavy lift vehicle to transport astronauts to NRHO.

Under NASA's current scenario, billions of dollars would be spent developing three lunar elements with one or two of the expensive elements having-- no long term future-- as far as the pioneering of the Moon and the rest of the solar system is concerned. The complexity of a three stage vehicle also enhances the risk to astronauts. And it delays the-- inevitable development-- of propellant depots, a technology that is essential for the exploitation of lunar propellant resources.    

So, under the scenario presented here, the propellant depot and reusable spacecraft architecture designed to return astronauts to the Moon would give NASA and America's launch companies almost complete strategic and economic dominance over cis-lunar space by 2025. And NASA could have astronauts on the surface of the Moon at the south lunar pole before then end of 2024.



SLS and Commercial Launch Scenario for Returning Astronauts to the Lunar Surface by 2024

2020 

SLS Block I:   Uncrewed test launch of Orion/SM/ICPS to DRO (Distant Retrograde Orbit)


2021

SLS Block I:   Crewed launch of Orion/SM/ICPS on a trans lunar injection lunar flyby.

Commercial Launch:  Propulsion and Power Bus deployed to LEO for self deployment to NRHO


2022

Commercial Launch: Remaining Gateway elements deployed and assembled LEO

Commercial Launch: Commercial Crew launch to inspect the Gateway before it is deployed to NRHO later in the year


SLS Block I + ICPS upper stage: Two fully fueled ICPS or Centaur V upper stages, or a combination of both  are deployed to LEO for a docking rendezvous with the Gateway at LEO. The two boosters transport the Gateway to NRHO (More Gateway component mass can be transported to NRHO if water for  radiation shielding is transported to the Gateway later by commercial launchers)

Commercial Launch: Two FlexCraft vehicles launched to NRHO Gateway

Commercial Launch: Beginning of commercial launches of water and other supplies to NRHO Gateway 



2023

(Last use of RS-25 engines from the Space Shuttle legacy) 

SLS Block I: Crewed launch of Orion/SM/ICPS or Orion/SM/Centaur V to NRHO Gateway

Commercial Launch: Vulcan/Centaur launch of ACES propellant depot to LEO

Commercial Launch: First commercial launches of  liquid oxygen tankers to LEO

Commercial Launch: First commercial launches of liquid hydrogen tankers to LEO


2024

(New RS-25 engines now being produced and utilized)

SLS Block I: Two R-LL reusable spacecraft launched to LEO utilizing commercial propellant depots at LEO to redeploy to NRHO. Both vehicles are initially used to deploy robotic vehicles to the lunar surface for sample returns. One R-LL goes to the north lunar pole. The second R-LL goes to the south lunar pole.

SLS Block I: Crewed launch of Orion/SM/ICPS or Orion/SM/Centaur V or Orion/SM/EUS to NRHO Gateway

Three members of the Orion crew boards one of the R-LL spacecraft for the first human mission to the south lunar pole. Three other crew members remain at the NRHO Gateway to serve as an emergency rescue team in case the first vehicle experiences a serious malfunction while on the lunar surface.

Commercial Launch: Vulcan/Centaur Launch of ACES depot to LEO to self deploy to NRHO

Commercial Launch: Beginning of commercial deployment of liquid oxygen tankers to NRHO

Commercial Launch: Beginning of commercial deployment of liquid hydrogen tankers  to NRHO

Commercial Launch: Vulcan/Centaur launch of reusable Orion/ACES to LEO  for crew transport between LEO and NRHO using propellant depots



Launch Vehicles that could be used to help return humans to the surface of the Moon

SLS Block IB: 110 tonnes to LEO (operational 2024)
 
SLS Block I + ICPS upper stage: 95 tonnes to LEO (operational in 2020)

SLS Block I : 70 tonnes to LEO  (operational in 2020)

Falcon Heavy: 63.8 tonnes to LEO (currently operational)

Vulcan Centaur Heavy: 34.9 tonnes to LEO (operational 2023)

Delta IV Heavy: 28.4 tonnes to LEO (currently operational) 

Vulcan Centaur: 27.5 tonnes to LEO (operational 2021)


Upper Stages that could be deployed to LEO by an SLS Block I Launch

ICPS: Total mass: 30.7 tonnes; empty mass: 3.49; propellant mass: 27.2 tonnes (currently operational)

Centaur V: Total mass: ~ 46 tonnes; empty mass: ~5 tonnes; propellant mass: 41 tonnes (operational 2021)

ACES:  Total mass: ~ 73.5 tonnes; empty mass: ~ 5.5 tonnes; propellant mass: 68 tonnes (operational 2023)

EUS: Total mass: 140 tonnes; empty mass: 15 tonnes;  propellant mass: 125 tonnes (operational 2024)


With NASA's new super heavy lift capability, America will be able to deploy large and heavy structures (up to 110 tonnes in mass) to LEO with a single launch.  This should enable NASA and private space companies to deploy huge reusable spacecraft with crewed interplanetary capability to LEO.  Single launches of the  SLS will also be able to deploy enormous microgravity and artificial gravity space habitats to LEO with pressurized volumes greatly exceeding that of the International Space Station.

With its propellant depot architecture, reusable ACES spacecraft working alone or in pairs could transport at least 40 to 80 tonnes of payload from LEO to practically anywhere within  cis-lunar space. An reusable EUS that could utilize propellant depots would have substantially more capability.

Cargo landing vehicles directly  derived from the notional R-LL vehicle should be able to land more than 40 tonnes of payload on the surface of the Moon.

Finally, by using commercial spacecraft to reach LEO,  a propellant depot architecture could  allow astronauts and tourist to easily travel between NRHO and LEO. This would make it unnecessary to launch astronauts to NRHO aboard a super heavy lift vehicle that is only infrequently used to launch passengers.  At the Gateway, single stage reusable vehicles could be used to travel between the lunar surface and NRHO.   And suddenly private commercial space tourism could expand beyond LEO-- all the way to the practically any place on the surface of the Moon.  And a new economic age of space travel will have begun!




Links and References

Bridenstine says “nothing off the table” as NASA develops new lunar plan 

How Much Water Is on the Moon?

Cis-Lunar Gateways and the Advantages of Near Rectilinear Orbits

Work begins on rocket engines for SLS flights a decade from now

Realistic Near-Term Propellant Depots: Implementation of aCritical Spacefaring Capability 

Status of Power and Propulsion Element (PPE) for Gateway

Utilizing the Centaur V and ACES 68 for Deep Space SLS Missions

ACES Stage Concept: Higher Performance, NewCapabilities, at a Lower Recurring Cost

ULA’s Vulcan Rocket To be Rolled out in Stages

ULA's Tory Bruno (Twitter)

A Commercially Based Lunar Architecture

Evolving to a Depot-Based Space Transportation Architecture

A Study of CPS Stages for Missions beyond LEO

LARGE SCALE CRYOGENIC STORAGEWITH ACTIVE REFRIGERATION

Transient Modeling of Large Scale Integrated Refrigerationand Storage Systems

NASA Adminstrator's Speech on Returning to the Moon at the Space Symposium

Inflatable Biospheres and Bio-Tori for Large Outpost and Colonies on the Lunar Surface

Notional regolith bag covered Kevlar biosphere and  bio-torus next to two solar powered cylindrical SLS propellant tank technology derived lunar regolith habitats on top of a microwave sintered lunar outpost floor.

by Marcel F. Williams 

NASA's Space Launch System (SLS) scheduled to go into operation by 2020 or 2021. But large cargo landing vehicles are going to be required  in order to utilize the SLS for the deployment of  lunar outposts habitats.  Large multilevel pressurized habitats derived from SLS propellant tank technology  could be deployed to the lunar surface on top of cargo landing vehicles designed to fit within a 10 meter in diameter SLS payload fairing. Such multilevel habitats for the lunar surface could be 8.4 meters in diameter, with two to four levels available for habitation. The average apartment in the US provides approximately 82 meters of floor area.  With each 8.4 meter in diameter level providing more than 55 square meters of floor area, a single multilevel SLS deployed lunar habitat could provide lunar astronauts with 105 to 210 square meters of habitation floor area. 

X-Ray of notional SLS propellant tank derived Lunar Regolith Habitat

However, substantially larger lunar habitats would require the deployment of inflatable structures.

Various  types of inflatable  habitats have been proposed by NASA personal since the dawn of the space agency. In the 1980's, M. Roberts of  NASA's Johnson Space Center,  proposed deploying inflatable   Kevlar biospheres to the lunar surface.  Since the lower hemisphere  of such biospheres would be underground, the radius of the inflated habitats would be limited by the depth of the regolith. Depending on the region on the lunar surface, lunar regolith can be as deep as eight meters or as shallow as two meters before encountering bedrock.  Such depth constraints on the lunar surface would limit the diameter of a biosphere to just  4 to 16 meters. A 16 meter biodome pressurized with an Earth-like  nitrogen and oxygen atmosphere of 14.7 psi (101.3 kPa) with a safety factor of four would weigh only 1.76 tonnes.

X-Ray of notional regolith bag shielded biosphere on the lunar surface (Credit: NASA)

However, the constraints of regolith depth could be easily alleviated by inflating a biosphere-- on top of the lunar surface-- and surrounding it with an inflatable bio-torus. An inflated Kevlar torus would be an inherently self supporting structure. So regolith could be deposited within the cavity between the bio-torus and the biosphere, providing structural support for the inner biosphere. Since the surround bio-torus would require substantially more Kevlar material than the biosphere, reducing the diameter of the torus to approximately half that of the biosphere could substantially reduce the amount of mass needed to be deployed to the lunar surface.  A spacious cavity between the bottom of the biosphere and the surrounding bio-torus could accommodate  additional living space in the form a smaller bio-torus about one third the diameter of the external bio-torus.

Inflatable torus extraterrestrial habitat (Credit: NASA, 1961)

Lunar Statistics

Diameter relative to the Earth: 27.3%

Surface area relative to the Earth: 7.4% (Land area not covered by water only comprises ~ 29% of the Earth's surface)

Surface gravity: 0.17g

Regolith depth: 2 to 8 meters 

Annual amount  of cosmic radiation on the Lunar surface during the solar minimum - 38 Rem

Annual amount of cosmic radiation on the Lunar surface during the solar maximum - 11 Rem

(Maximum amount of  radiation allowed for radiation workers on Earth per year - 5 Rem)
(Maximum amount of radiation allowed for adult female during nine months of pregnancy -)

The biodome and the upper and outer exterior of the bio-torus could be covered with regolith bags that are either 2.5 meters or 5 meters in thick, depending on what level of radiation protection is desired for the habitat. At least, 10 centimeters of lunar regolith is required to protect humans from the cell killing heavy nuclei component of cosmic radiation. Thermal fluctuations of the lunar surface may also require as little as 10 centimeters of lunar regolith. Assuming an average regolith density of about 1.5 grams per cubic centimeter, at least 60 centimeters of lunar regolith would be required to protect the habitat from micrometeorites.

Its relatively easy to shield habitats and even humans in pressure suits  from the heavy ion component of cosmic radiation.  But most cosmic ray particles are composed of the smallest ionized atoms: protons (85%) and alpha particles (ionized helium atoms) which are much more difficult to shield against. Most protons and alpha particles streak harmlessly though the vacuous space between the atoms of the human body. But the relentless rain of these cosmic ray components  inevitably results in impacts upon our body tissues.

On average, humans receive about 620 mrem per year of radiation due to a combination of sources from both cosmic and terrestrial radiation sources. The maximum recommended radiation exposure for  a pregnant woman is 50 mrem per month which comes very close to the average radiation exposure that humans on Earth experience in a year.

The maximum level of radiation exposure for radiation workers on Earth is 5 Rem per year. And that would require approximately 2.5 meters of regolith shielding. But the maximum level of radiation exposure allowed for a woman during the term of her pregnancy is just 0.5 Rem. So lunar regolith shielding would probably have to be increased to  5 meters (the same level of radiation shielding provided for humans by the depth of the  Earth's atmosphere). Inflated with an Earth-like atmospheric pressure, biospheres and bio-tori could easily support the weight of 5 meters of regolith.

Of course, there would be no shortage of available regolith on the surface of the Moon.  Just one  hectare of regolith on the lunar surface could provide between  20,000 to 80,000 cubic  meters of shielding material (2 million to 8 million cubic meters per square kilometer) for  large pressurized habitats.  And the excavation and deposition of lunar regolith and even the production of regolith bags could be done by robots teleoperated by personal employed on the surface of the Earth. 

During solar minimum conditions, the maximum radiation exposure on the lunar surface can  exceed 3000 mrem per month. A hardened pressure suit designed to protect against the heavy nuclei component of cosmic radiation could  reduce general cosmic radiation exposure by two thirds. But even 1000 mrem (one Rem) per month would exceed annual radiation levels for radiation workers in less than six months. Pregnant lunar colonist would probably have to remain inside the protective confines of their habitat during nine months of pregnancy. But even if lunar colonist spent only 10% of their time  outside of  pressurized habitats (less than 2 Rem of annual exposure within radiation hardened pressure suits ), that would still avail them to more than 16 hours a week of EVA time on the lunar surface. But I seriously doubt if most lunar colonist will spend more than 5% of their time outside of the comfort of their lunar habits.

So it seems likely that Lunar colonist will spend at least 90 to 95% of their time on the Moon within the confines of pressurized  habitats. So living on the Moon will mostly be about living within the protective confines of pressurized habitats that are also designed to protect its inhabitants from the dangers of micrometeorites, extreme thermal fluctuations, and excessive radiation exposure.

So if future Lunarians are going to have to spend the overwhelming majority of their time-- indoors, such pressurized habitats should be as comfortably-- spacious-- as possible. Once large SLS propellant tank technology derived habitats are on the lunar surface, much larger (inflatable) habitats could be deployed by the SLS.

A single SLS Block I launch could deploy a 27.5 tonne biosphere, plus a 38 tonne external  bio-torus and a 2.5 tonne inner bio-torus to LEO. So a total mass of 68 tonnes would be deployed by the SLS to Low Earth Orbit. A pair of reusable ACES-68 orbital transfer vehicles could transport the payload to NRHO. Reusable lunar cargo vehicles could transport the biosphere and the bio-tori separately to the lunar surface.

X-Ray of 40 meter in diameter lunar biosphere surround by two bio-tori

A second SLS Block I launch could deploy five 3 meter in diameter and 3 meter high airlocks: one to be connected to the bottom of the biosphere and two each to be connected the bottoms of the two bio-tori on opposite sides. Six 3 meter in diameter expandable tunnels will also be deployed to linearly connect the airlocks to each other and to allow astronauts to enter and exit the base of the inflatable habitats. Six expandable regolith walls will be included to provide a firm regolith base for the biosphere and the bio-tori. Six 2.4 meter in diameter ECLSS modules will be included: two to be attached to the a biosphere airlock and individual modules to be attached to each of the bio-tori airlocks. Piping  will be provided to connect the ECLSS modules to external radiators. And wiring will be provided to connect the ECLSS to external solar, nuclear, and chemical power units.  Again, these payloads will initially be deployed to LEO before be transported to NRHO and then to the lunar surface by reusable LOX/LH2 vehicles.

 Once deployed to the lunar surface, the inflated Kevlar biosphere would be 40 meters in diameter. An 18 meter in diameter bio-torus would surround the biosphere. And an additional 6 meter in diameter bio-torus would be placed with the lower cavity between the biosphere and the external bio-torus.The pressurized biosphere and bio-tori would sit on top a regolith base. Airlocks beneath the biosphere and bio-torus would be connected to cylindrical metallic tunnels internally pressurized with cylindrical Kevlar bags would provide astronauts with easy access to the other sections of the habitat while also allowing them to exit the habitat or to connect to exterior habitats. 

The atmospheric pressure within the biosphere and within the bio-torus would be the same atmospheric pressure as on Earth. And this will allow people working in the bio-torus to move easily back and fourth between the bio-torus and the biosphere without the need of to deal with differences in pressure.

Notional biodome recreational floor area of a 40 meter in diameter bio-torus

With a floor area of 1257 square meters within a spacious biodome 20 meters high, the upper hemisphere of the 40 meter biosphere could be used for a variety of recreational purposes (tennis, volleyball, basketball, gymnastics, swimming, etc). The biodome could also provide astronauts with  a spacious area for relaxation if landscaped with grass and trees and other aesthetically pleasing foliage. 

The lower hemisphere would be composed of four expansive habitat floors, 2.4 to 3 meters high, providing apartments, laboratories, and gyms and more than 1200 square meters of habitable floor space.  The floors, rooms, and apartments will be composed of prefabricated sections manufactured on Earth and assembled within on the Moon within the pressurized biosphere. Ceiling, floor, and wall panels and beams and other structural components could be transported to the lunar surface by reusable and expendable  commercial lunar transports.  So the lower half of the biosphere should be able to provide at least four expansive levels for  habitation, with the lower hemisphere alone far exceeding that of the floor area for  SLS propellant tank derived habitat modules.

The surrounding 18 meter bio-torus would also consist of multiple levels that are composed of modular components. But, under this scenario, the   bio-torus would be divided into five levels. The top level would be used for orchards (apple, orange, lemon, cherry, and peach trees) and also for raising large fauna: pigs, miniature cows, sheep, and possibly even ostriches. The second level would be used for poultry. The third and fourth level would be used for growing fruits and vegetables: bananas, pineapples, watermelons, tomatoes, carrots, lettuce, potatoes, corn, wheat, sugar beets, etc. The bottom level of the bio-torus would be used for aquaculture: brine shrimp, fish, oysters, etc.

The inner 6 meter in diameter bio-torus would be largely used for storage and for emergency habitation in case something serious should occur inside of the biosphere.

The entire facility would be designed to comfortably accommodate between 50 to 100 individuals.

 Diameter and mass of Kevlar biospheres and bio-tori pressurized at 14.7 psi (101.3 kPa) with a safety factor of  four without regolith shielding and structural support

40 meter in diameter  biosphere: 27.5 tonnes
Surrounding 18 meter in diameter bio-torus: 38 tonnes
Surrounding 6 meter in diameter interior bio-torus: 2.5 tonnes

Mass of an M1-Abrams Tank - 62 tonnes

100 meters in diameter biosphere: - 430 tonnes
Surrounding 50 meter in diameter bio-torus: 759 tonnes
Surrounding 16 meter in diameter interior bio-torus: 44 tonnes  

Mass of a Boeing 747 - 440 tonnes

200 meters in diameter biosphere:  3438 tonnes
Surrounding 100 meter in diameter bio-torus: 6071 tonnes
Surrounding 32 meter in diameter interior bio-torus: 348 tonnes

 Mass of the Eiffel Tower - 7300 tonnes

300 meters in diameter biosphere:  11,600 tonnes
Surrounding 150 meter in diameter bio-torus: 20,512 tonnes
Surrounding 50 meter in diameter interior bio-torus: 1264 tonnes

Mass of an Ohio-Class atomic submarine - 16,764 tonnes


400 meter in diameter biosphere: 27, 500 tonnes
Surrounding 200 meter in diameter bio-torus: 48, 574 tonnes
Surrounding 60 meter in diameter interior bio-torus: 2478 tonnes

Mass of a cruise ship - 100,000 tonnes

1000 meters in diameter biosphere: 430,000 tonnes
Surrounding 500 meter in diameter bio-torus: 759, 000 tonnes
Surrounding 160 meter in diameter interior bio-torus: 44, 000 tonnes

 Mass of the Golden Gate Bridge - 804, 673  tonnes

Much larger inflatable facilities will probably require the Kevlar material to be exported from Earth in small sections to be woven together by machines deployed to the lunar surface. And, eventually,  Kevlar threads will be manufactured on the lunar surface from lunar materials mostly found at the lunar poles.

Biospheres that are 400 meters in diameter could be very attractive for human colonization of the Moon. The 200 meter high bio-domes of such facilities would be able to provide artificial lakes and lagoons at least 200 meters in diameter with surrounding sandy beaches where you could not only swim but also put on a pair of  wings and fly under the low lunar gravity.  The top half of the surrounding 200 meter in diameter bio-torus could also be used for housing familiar to that on Earth plus recreational parks and 100 meter lakes and lagoons. And with a 100 meter high rooftop, there should also be enough room in the bio-torus to strap on a pair of wings and fly at least 50 meters above the ground within the upper half of the bio-torus.



Links and References

Inflatable Biospheres for the New Frontier

Structural Design of a Lunar Habitat

Inflatable space habitat

Inflatable Habitation for the Lunar Base


Living and Reproducing on Low Gravity Worlds

Information for Radiation Workers

Doses in Our Daily Lives 

Ionizing Radiation

 GLOBAL LUNAR REGOLITH DEPTHS REVEALED


 ECLSS