Launch of Artemis ll

 

 

Trans Lunar Injection Successful!  

 

Links and References

Space Launch System 

 

Where the SLS Comes From

 

Links and References

Space Launch System

NASA Space Launch System Infographics

SLS Derived Artificial Gravity Habitats for Orbital Havens and Interplanetary Space Travel

Notional spinning artificial gravity producing AGH 1500 orbiting 600 km above the Earth's surface. Rectractable solar arrays and radiators produce power and regulate temperatures for the twin habitats.    

by Marcel F. Williams

Microgravity environments are inherently deleterious to human health in space. 

Weight loss, the clumping of perspiration and tears, facial and speech distortions, a degraded sense of  taste and smell,  and even an increased frequency of  flatulence are minor problems associated with short term exposure to a microgravity environment. 

 

But months or years under microgravity conditions can cause much more serious problems for  human health in space. Without regular exercise, 20% of muscle mass can be lost in just 12 days. 1.5% of bone mass is lost in a single month. And this bone demineralization can increase the calcium concentration in the blood stream, increasing the risk of developing kidney stones.  Significant reductions in cardiovascular fitness can also result from long periods of microgravity conditions. Vision problems of varying degrees of severity can occur in men in their 40s or older.  And the use of medicine can be hampered due to the changes in blood flow redistribution under microgravity conditions. 

 

After  a few months aboard the ISS, the blood pressure of some astronauts drops to abnormally low levels when they move from a lying position to a sitting or standing position. Some astronauts even have problems standing up, walking, and turning and stabilizing their gaze.

 

 The deployment of small habitats that are capable of spinning to produce artificial gravity could alleviate the health problems associated with a microgravity environment. Artificial gravity habitats could allow humans to:

1. Remain in orbit perpetually without the need to return to the Earth’s surface reducing the number of launches necessary to maintain a human presence in space 

2.  Remain physically healthy during long interplanetary journeys 

3. Receive quality medical care while in orbit including major surgical procedures. 

4. Have a  permanent human presence in orbit practically anywhere in the solar system 

5. Test  variable levels of gravity on the health of humans and other animal species

Notional 10 meter in diameter AGH 1500 in launch configuration on top of the SLS compared an SLS vehicle with an EUS and 10 meter in diameter payload faring.

 

An SLS Block I configuration would easily be capable of deploying a 60 tonne artificial gravity habitat to LEO. Reusable EUS derived ROTV 100 orbital transfer vehicles cold to deploy the habitat to the appropriate orbit where thrusters could rotate the structure, expanding its  twin counter balancing pressurized habitats at the ends of a 224 meter in diameter  boom. 

 

Directly derived from the SLS oxygen tank architecture, each habitat would be 8.4 meters wide and 16.8 meters tall. This would allow at least five 8.4 meter in diameter habitat levels that are  at least 2.5 meters high, ten human habitat levels in total for the habitat.    This should be enough room to easily accommodate 12 to 32  astronauts and their guest within the twin counter balancing pressurized modules. Because the combined pressurized  area of the twin habitat modules exceeds 1500 cubic meters in volume, the notional artificial gravity habitat is here referred to   as the: AGH 1500 (Artificial Gravity Habitat 1500).

 

AGH 1500 both contracted for trajectory burns and expanded to rotate producing 0.5g of simulated gravity

 

In order to mitigate the physiological effects of Coriolis, the habitat would be approximately 224 meters in diameter, rotating at approximately 2rpm (two rotations per minute) to produce 0.5g of simulated gravity (higher than the gravity on the Moon and Mars).  Slower rotations could be used to simulate the gravity on the Moon, Mars, Mercury, and Callisto, low gravity worlds that could potentially be colonized by humans someday. 

 

 

X-Ray of AGH 1500 showing floors levels on one of the counter balancing pressurized habitat modules

X-Ray of the top or bottom of the microgravity habitat area of the AGH 1500

 

Housed within a ten meter external cylinder would create a 80 centimeter gap between the pressurized habitat. Less than 20 centimeters of water within an external  polyethylene bag or pipes  could provide astronauts on interplanetary journeys with protection against the heavy nuclei component of cosmic radiation and from major solar storm events while also reducing cosmic radiation exposure in general during multi-month interplanetary journeys. 

Permanent artificial gravity habitats located beyond the magnetosphere within cis-lunar space and in orbit around other planets, moons, and asteroids will have to be provided with much more shielding to protect against excessive radiation exposure and potential micrometeorite damage. About 2 meters of lunar regolith would be required to shield the the pressurized habitat. But less than 80 centimeters of space would be available. However, lunar regolith is rich in much denser iron particles   that could be mined and deployed for external shielding.  So only 40 centimeters of lunar iron could be used to permanently shield artificial gravity habitats. Thorium is an even denser lunar material could also be utilized since there appears to be substantial thorium deposits in certain regions on the Moon. 

 

SLS EUS (Exploration Upper Stage) next to a notional EUS derived ROTV 100 (Reusable Orbital Transfer Vehicle +100 tonnes of propellant)

The telescopic boom cylinders are approximately 5 millimeters thick (much thicker that the fuselage for an airplane).  Five cylindrical booms would be  housed within the ten meter in diameter cylinder that accommodates radiation and micrometeorites shielding before the booms are expanded. One centimeter would be added to the top of each cylinder in order for each segment of the boom to securely attach to each other. So 1.5 centimeters would be required for each cylinder. Plus you have to add a centimeter for the boom cable that allows the boom to expand and contract. So ten centimeters would have to be utilized for the telescopic boom. That would allow nearly 70 meters to be used for radiation and micrometeorite shielding. But, as previously stated, only 40 meters or less would be required to permanently shield the twin habitat modules. 

 

AGH 1500 being deployed to a low Earth orbit 600 km above the Earth's surface by an EUS derivied reusable ROTV-100

Reusable EUS derived ROTV 100 vehicles could deploy the AGH 1500 600 kilometers to mitigate frictional drag from the Earth's atmosphere. After refueling at LOX/LH2 propellant depots, two ROTV 100 orbital transfer vehicles could deploy the AGH 1500 to various locations within cis-lunar space: NRHO, DRO, L3, L4, and L5. And twin ROTV orbital transfer vehicles could also deploy the AGH 1500 from cis-lunar space to the orbits of Mars and Venus-- allowing a permanent human presence in orbit above the surface of Mars and the clouds of Venus.

Twin ROTV 100 orbital transfer vehicles deploy an AGH 1500 from lunar orbit to a high Mars orbit beyond the orbit of the martian moon, Deimos

Links and References 

SLS Derived Artificial Gravity Habitats for Space Stations and Interplanetary Vehicles

SLS Fuel Tank Derived Artificial Gravity Habitats, Interplanetary Vehicles, & Fuel Depots

Cosmic Radiation and the New Frontier

Protecting Spacefarers from Heavy Nuclei

The Logistical Viability of an SLS EUS Derived Reusable Lunar Crew Lander

 

Commercial Utilization of Spent EUS Upper Stages after SLS-C Launches

Latest configuration of EUS for the Space Launch System (Credit: NASA, Boeing)

by Marcel  F. Williams

Boeing's development of the EUS (Exploration Upper Stage) for the Space Launch Systems super heavy lift configuration (Core stage/2 SRBs, EUS) should also enable the SLS to be deployed as a simpler two stage rocket. 

SLS Block I and Block IB (Credit: NASA)

 

The SLS core stage plus and EUS upper stage should be   capable of deploying more than 30 tonnes of payload to low Earth orbit. In this article, I refer to this SLS variant as the SLS-C.

Notional SLS-C (SLS core stage plus EUS upper stage) capable of deploying a CST-100 crew module plus nearly 17 tonnes of payload or more than 30 tonnes of payload to LEO (After NASA/Boeing).

Utilizing the SLS-C as a much more frequently launched crew launch vehicle could significantly reduce the cost of its super heavy lift variant. The SLS-C would also be more environmentally friendly since it won't produce the CO2 and the black carbon (soot)  created by hydrocarbon fueled rockets (methane and RP-1).  Black carbon is also deleterious to the Earth's ozone layer. 

Deploying Boeing's crewed CST-100 Starliner would allow the SLS-C to deploy the 13 tonne spacecraft with nearly 17 tonnes of additional payload to LEO.  So an   SLS-C should be capable of deploying a crew plus satellites to LEO. And since orbiting propellant producing water depots are now being developed by Blue Origin, a crew plus nearly 17 tonnes of water could also be deployed to LEO. The SLS-C could also be routinely used to deploy 30 tonnes of water to orbiting space stations or propellant manufacturing water depots at LEO.

Notional Mega orbital habitat deployed to LEO with-- a single-- SLS super heavy lift launch. The EUS hydrogen tank derived space habitats are attached to a spent SLS core stage retrofitted by robots or astronauts with airlocks. Combined with the spent core stage, the Mega habitat provides more than 4000 cubic meters of volume; more than four times the total volume of the ISS.  Solar panels and radiators are viewed laterally. One CST-100 Starliner his attached to an airlock while the other has detached before heading back to the Earth's surface.    

But if commercial space stations are deployed to LEO then the EUS upper stages could be retrofitted for other commercial purposes. This could be done by astronauts or  by robots teleoperated from the Earth's surface or by astronauts and robots working together in space.

Flexcraft could be crewed or teleoperated from Earth to retrofit spent SLS core stages or spent EUS upper stages for a variety of commercial uses (Credit NASA).

 

The EUS hydrogen tank in particular will be 8.4 meters in diameter and 7.5 meters tall. And such a substantially spacious  tank could be used for a large variety of commercial purposes that could allow-- each spent EUS-- to generate hundreds of millions of dollars in savings annually.

X-ray of the EUS showing the large 8.4 meter in diameter hydrogen tank and the small oxygen tank (Credit NASA/Boeing).

 

 An EUS retrofitted near a commercial space station with airlocks, pump connectors, or solar powered cryocoolers could be used for:

Water storage: Both the spent hydrogen and oxygen tanks of the EUS could be modified to store nearly 300 tonnes of water. Water can be used by commercial space stations for drinking, food processing, the the production of air, and to enhance radiation shielding. Propellant depots can convert water into hydrogen and oxygen propellant for spacecraft destined for beyond LEO cis-lunar and interplanetary missions. 

Large habitat module: Retrofitted with an airlock, the empty hydrogen tank could be pressurized and  attached to a small or large habitat, adding a huge amount of additional habitat area:  7.5 meters high and 8.4 meters in diameter.  Such a substantial increase in space could be used for  microgravity recreation  or used to add three or four 2.5 meter high habitat levels.

Sewage storage: Waste water from commercial space stations can be stored and later reprocessed into potable water.

LOX storage: During the production of LOX/LH2 propellant  through electrolysis at an orbiting depot, 25% of the oxygen is wasted. Retrofitted with a pump connectors and cryocooler, the spent EUS hydrogen tank could be used to store more than 200 tonnes of excess oxygen saving more than a billion dollars in additional launch cost from Earth. 

Micogravity lettuce farm: a large variety of edible lettuce can be grown under microgravity conditions. A spent EUS would allow substantially more area for growing food.

Microgravity Mushroom farms: mushrooms can be grown in microgravity and when exposed to UV light than can be enriched with vitamin D.  Growing mushrooms within spacious EUS hydrogen tank could help to reduce the cost of shipping food from the Earth's surface.

Artificial gravity aquaculture: attached to two thruster modules, the EUS hydrogen tank could be filled with water or seawater and used to raise brine shrimp, fish, or oysters. 

Micrometeorite and radiation shielding: A spent US transferred to the lunar gateway or other cis-lunar Lagrange point areas for utilization could still have value after its no longer used for habitats, water, sewage, or oxygen storage. If the EUS is simply crushed and grounded up into fragments by solar powered machines in orbit, the high density fragments could be used to enhance the  radiation shielding for  habitats beyond the Earth's magnetosphere while also enhancing micrometeorite protection. 

 

Links and References

NASA's Space Launch System Exploration Upper Stage completes critical design review

The Commercial Case for an SLS-B

Deploying a Ginormous SLS Derived Dry/Wet Workshop Habitat with a Single SLS Launch

The Logistical Viability of an SLS EUS Derived Reusable Lunar Crew Lander

Substantially Enhancing the Capability of the SLS Architecture by Utilizing EUS Derived Propellant Depots and Reusable Orbital Transfer Vehicles

 Flexcraft

NASA FlexCraft 2015 - Marshall Space Flight Center

How Fungi Can Support Life in Space

 

 

 

Launch of the Artemis 1

 

 

Links and References

Deriving Economically Sustainable Crew Launch Vehicles from the SLS

Boeing's New HLV Concept could be the DC-3 of Manned Rocket Boosters

The Functional and Economic Value of Repurposing Spent SLS Core Stages

Deploying a Ginormous SLS Derived Dry/Wet Workshop Habitat with a Single SLS Launch

The Logistical Viability of an SLS EUS Derived Reusable Lunar Crew Lander

ARTEMIS I

Media Briefing: Artemis I Launch Status (August 30, 2022)

The Functional and Economic Value of Repurposing Spent SLS Core Stages

Notional SLS derived Dry/Wet orbital habitat at LEO with more than 4000 cubic meters of pressurized volume. A notional  crewed reusable REUS-LV approaches the habitat after a voyage from a similar habitat at NRHO.

by Marcel F. Williams

 

Deploying large habitats, depots, and reusable interplanetary vehicles to LEO is probably the most logistical and economically efficient way to utilize the new Space Launch System (SLS). But the basic SLS Block I configuration capable of deploying up to 70 tonnes to LEO also comes with an added benefit. The spent core stage of the  SLS  could also arrive and remain in low Earth orbit fully intact. 

With a pressurized volume exceeding 916 cubic meters, $165 billion (in current dollars) the International Space Station is considered to be the most expensive structure ever built by humanity. But the pressurized volume of a spent  SLS core stage would exceed 3000 cubic meters (more than three times the pressurized volume of the ISS). 

If SLS core stages were allowed to remain in orbit, it could be retrofitted by astronauts from a nearby space station or space vehicle to accommodate enormous amounts of water, or cryogenic propellants, or the pressurized atmospheres of habitats. This, of course, would add significantly more economic value to each SLS launch.   

X-Ray of the SLS core stage hydrogen and oxygen tank (Credit NASA)

 

Microgravity Habitats

Polls suggest that 42% of Americans would like to travel into space. But  there are only about 52,000 people, worldwide, who could actually afford the $25 to $50 million cost of space travel. Still that suggest that perhaps 22,000 people who would like to travel into space-- actually have the funds to to do so. Annually, if just 10% of that group paid to visit an orbiting space hotel it would  require more than 400  commercial launches every year. This, of course, doesn't include the number of unmanned launches needed to provide such orbital facilities with the food and water and other supplies.  But even if a mere 1% of the super wealthy who desired to travel into space purchased rides to a space habitat every year,  that would require 44 to 55 private commercial launches annually.

Of course, additional revenues could be accrued by providing accommodations for astronauts from NASA, the Department of Defense and astronauts from foreign space agencies.  

Cramped conditions inside the interior of an ISS crew module (Credit NASA)

Relatively spacious interior of  6.6 meter in diameter Skylab space station (Credit NASA)

Two workers inside the empty interior of an  8.4 meter in diameter  SLS liquid hydrogen propellant tank (Credit: Boeing Aerospace.)

If the owner of a space hotel charged  $500,000 a day for each day their facility accommodated a  visiting astronauts or space tourist resided in their facility (including arrival and departure days) then they would make $5 million for a ten day stay. For a six member flight crew that would be $30 million dollars in revenue in just ten days.  If such a facility was continuously occupied by six individuals on average then  the orbiting hotel would make $1.095 billion (nearly $1.1 billion a year).

An SLS core stage retrofitted with docking adapters and airlocks could be latter attached to habitat modules deployed by the SLS or other launch vehicles. This could allow pressurized habitats deployed by private companies or national space agencies to attach their modules to a purchased retrofitted SLS spent core stage, guaranteeing them and additional 3000 cubic meters of pressurized space-- no matter how large of small their habitat modules are.

A  spent SLS core stage retrofitted with docking airlocks sold for $5 billion could be paid off in less than five years if the facility was continuously occupied by at least 6 astronauts or tourist. A 20 to 30 year lifetime might produce $21 to $32 billion of revenue for the SLS core stage enhanced habitat.

 

Notional SLS derived Dry/Wet orbital habitat at NRHO with more than 4000 cubic meters of pressurized volume. A notional crewed reusable REUS-LV is docked at the habitat before transferring a six person crew to the surface of the Moon.

Water & Sewage Depots

Water, of course,  is an extremely valuable commodity in extraterrestrial environments. Water can be used to wash, to drink, and to prepare food for its human occupants. Electrolysis can be used to convert water into  oxygen to create breathable atmospheres.   And the oxygen and hydrogen produced through the electrolysis of water can also be liquefied and utilized for rocket propellant. 

Since a spent SLS core stage would have two empty tanks, one tank, in theory,  could be used to store enormous quantities of water. This water  could later be transported to nearby orbiting habitats or to propellant producing orbiting depots. 

Human occupied orbiting habitats will also produce substantial quantities of waste water in the form of sewage. So the second SLS core stage tank could be used to store this sewage-- almost indefinitely. Ultimately this sewage could be used as another source of water.  Methane could also be produced from the sewage to fuel liquid methane fueled interplanetary spacecraft. 

Nearly a tonne a day of waste water could be produced for six occupants aboard a space habitat saving more than 300 tonnes of water a year, avoiding perhaps $1.5 billion a year in cost if such water had to be brought from the surface of the Earth.  Assuming a 20 to 30 year lifetime for the depot, that could be $30 to $45 billion in water transport savings from Earth.                                                                                                                                                                                                                                                                                               

Liquid Oxygen and Liquid Methane Depots

Nine tonnes of water for a propellant producing depot would produce one tonne hydrogen propellant plus six tonnes of oxidizer-- leaving two tonnes of oxygen as a waste product. However, a spent SLS core stage could be used to store the excess oxygen.  The spent SLS core stage could be retrofitted with solar panels to keep the oxygen refrigerated. Interplanetary  vehicles launched from Earth could arrive in orbit with only fueled with hydrogen or methane, utilizing the excess oxygen stored by the SLS core stage for propellant oxidizer.

The second tank in the SLS spent cores stage could be used to store liquid methane produced from the sewage stored in water and sewage depots.

So every 90 tonnes of water sent into space for propellant production (~$450 million),  20 tonnes ($100 million) would be wasted-- if the excess oxygen produced through electrolysis  is not stored away to be later utilized. So 900 tonnes of water sent into orbit a year for propellant production could save $1 billion a year in propellant for extraterrestrial missions.

 Rotating Crop and Orchard Plantations 

With an interior diameter of approximately 8.4 meters, the two empty tanks of a spent SLS core stage tanks could accommodate two large areas for growing crops or trees. The cylinders would have interior surfaces of 285 meters squared for the empty oxygen tank and 886 meters squared for the empty hydrogen tank. The domed end caps could be used for vineyards (growing grapes). Even with soil (presumably originating from the lunar surface) a meter deep, the two tanks should be able to grow enough food to feed at least 12 people a year. 

Dwarfed trees between 2.5 to 3 meters tall could be used to grow apples, oranges, lemons, peaches, pears, plums, cherries, olives, etc. Banana plants could also be grown. 

Crops such as wheat, corn, rice, potatoes, yams, sugar beets,  tomatoes, lettuce, pineapples, etc. could also be grown.

The bio-waste from the agricultural foliage could also be of value. Pyrolyzed into syngas,  hydrogen or methane could be produced for rocket fuel and the waste CO could be converted into CO2 for growing trees and crops. 

A thruster module could be attached to the top of the spent core stage in order to make the structure spin along its axis, producing artificial gravity within the interior of the tanks. Remote controlled robots could be used to manage the orchards and crops. Humans in pressure suits could periodically visit the space farms under microgravity conditions to retrieve fruits and vegetables or to bring in more water and equipement by simply using the thrusters to hault the structure's rotation. Entry docking ports into the two tank areas could be retrofitted into each tank area the same way it would be done for the habitat core stages that were retrofitted to be habitats.   

Solar panels and cooling fins  could be attached to the thruster unit for providing thermal control and  electricity and interior lighting for a space farm.

If eight tonnes of food could were grown a year to feed up to 12 people, $40 million a year could be saved in food exports from Earth. This is perhaps $800 to $1.2 billion --in food import savings over the course of a lifetime for the spent SLS core stage tanks.

Notional EUS derived REUS-OTV with connecting ring for operations with a second REUS-OTV vehicle

 

Exploiting Residual Fuel

Several tonnes of propellant would be required to de-orbit the SLS core stage. But the residual fuel used to de-orbit the core stage sending it into the Earth's atmosphere could be extracted by orbiting propellant depots to be stored and saved to fuel vehicles destined for beyond LEO missions. This could amount to $5 million per tonne of fuel saved.

 

Beyond LEO Deployment 

While the SLS could deploy spent core stages to LEO, a notional REUS (Reusable Exploration Upper Stage) used in pairs could be used to redeploy the core stage practically anywhere within cis-lunar space (NRHO, DRO, L3, L4, and L5) and even into orbit around Mars and Venus.

Links and References

Deploying a Ginormous SLS Derived Dry/Wet Workshop Habitat with a Single SLS Launch

Space Launch System

Commercial Launch Demand to Private Microgravity Habitats at Low Earth Orbit

The Logistical Viability of an SLS EUS Derived Reusable Lunar Crew Lander

All about dwarf fruit trees

Cis-Lunar Gateways and the Advantages of Near Rectilinear Orbits

NASA Rolls Out Space Launch System

 

 

NASA Successfully Test SLS Core Stage

 

Links and References

Deploying a Ginormous SLS Derived Dry/Wet Workshop Habitat with a Single SLS Launch

SLS Derived Artificial Gravity Habitats for Space Stations and Interplanetary Vehicles

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

Pioneering and Commercial Advantages of Permanent Outpost on the Moon and Mars

 

SLS Program Manager Discusses Major Component Failure in Core Vehicle Engine

 

 

 

Green Run Update: Data and Inspections Indicate Core Stage in Good Condition

SLS Hot Fire Shutdown Due To Conservative Testing Parameters, Not Engine Malfunction

 

Commercial Advantages of a Large SLS Deployed Reusable Extraterrestrial Crew Landing Vehicle

Notional SLS deployed RLV-4 Crew lunar landing vehicle with a crew davit deployment system. 

by Marcel F. Williams

 

Before the end of the decade, the deployment of orbital propellant depots to LEO and NRHO (Near Rectilinear Halo Orbit) will probably make the SLS/Orion vehicle-- obsolete-- as part of an affordable and efficient crew transport  architecture to the lunar surface. So the-- crewed-- SLS/Orion configuration could be haulted just a few years after it started.  

 

However, the four major partners in SLS manufacturing and operations (Boeing, Northrup Grumman, Aerojet Rocketdyne, and Lockheed Martin) could take full economic advantage of the coming  propellant depot architecture by using the Space Launch System to deploy large-- reusable-- lunar landing vehicles into orbit to transport crews or heavy cargo to the lunar surface. 

 

I'll  call such a notional extraterrestrial landing vehicle, in this article, the RLV-4 (Reusable Landing Vehicle Four). And I seriously believe that if Boeing and their SLS partners finance and build a  RLV-4 type of vehicle for both crew and heavy cargo transport to the lunar surface, their partnership could easily end up economically dominating cis-lunar space and probably the rest of the solar system for the next 25 to 30 years-- with such a  simple single stage extraterrestrial vehicle and its inherently useful variants.

LOX/LH2 tank configuration in Boeing's Altair lunar lander concept (Credit: Boeing)

The notional  RLV-4 would be octagon shaped like Boeing's Altair lunar descent vehicle concept. But it will use a simplified propellant tank architecture requiring just two LH2 tanks and two LOX tanks, similar to Blue Origin's octagon shaped Blue Moon lunar lander which is basically a smaller-- simplified-- version of of the Altair lunar lander. 

Top view of LOX/LH2 tank configuration for Boeing's Altair lunar lander concept (Credit: Boeing)

 

The propellant tanks for the RLV-4 will be derived from Boeing's super light weight composite cryotank technology with the two large 3.8 meter in diameter hydrogen tanks and and the two smaller liquid oxygen tanks approximately 2.4 meters in diameter. Both cryotanks will stand nearly 6 meters high within the interior of the RLV-4 octagon. Gaseous compressed hydrogen will be used to pressurize the liquid hydrogen tanks and compressed gaseous oxygen for pressurizing the liquid oxygen tanks during liftoff and trajectory burns-- replacing gaseous helium. Gaseous hydrogen and oxygen will also be utilized for the vehicle attitude thrusters in this notional vehicle design. So hydrogen and oxygen will provide the propellant, attitude control, and tank pressurization for the RLV-4. 

Notional Boeing 3.8 meter in diameter composite LH2 tank and 2.4 meter in diameter LOX tank.

The RLV-4 would be somewhat similar in height with Boeing's Altair concept. But it would be able to store more than twice as much propellant (56 tonnes) thanks to the substantially larger  cryotank diameter of the liquid hydrogen tank and the larger diameter and height of the liquid oxygen tanks relative to those conceived for the Altair. So the RLV-4 would be capable of accommodating up to 56 tonnes of propellant which would be more than enough fuel to land a 16 tonne crew vehicle from LEO to the surface of the Moon.

The restartable engines for the RLV-4 could be provided by SLS partner, Aerojet Rocketdyne, who is currently developing the expendable RS-25 engines for the  SLS core vehicle and the RL-10 engines for the upper stage vehicle. The RL-10 derived CECE engines would be capable of throttling between 104% down to just 5.9% and would be capable of at least 50 in space starts. So the CECE engines should be capable of performing at least 12 round trip missions between NRHO and the lunar surface before having to be replaced. Using them in pairs would give the RLV-4 engine-out capability, enhancing crew safety.

However, the RLV-4 propellant tanks should be capable of at least 50 refills (50 round trips if  missions between NRHO and the lunar surface are conducted on a single fueling of propellant). So if two more engines were added to the RLV-4, 24 round trips could be possible if only two engines were used during a journey-- while propellant flow was shut off to the other pair of engines. Replacing the engines after 24 round trips with four more CECE engines could maximize the RLV-4's reusability allowing the vehicle to conduct up to 48 round trips to the lunar surface before-- if it is refueled less than 50 times. 

Basic RLV-4 cargo lunar lander with solar panels on four sides of the octagon shaped vehicle and radiators on four sides of the vehicle

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 aboard an SLS vehicle within a 10 meter fairing, the RLV-4 could easily fit within the internal  9.1 meter dynamic envelope of the payload fairing. 

 

Notional RLV-4 LOX/LH2 cyotank configuration within the octagon shaped vehicle

While NASA currently envisions only an 8.4 meter fairing for it's use of  the SLS, it would be in the economic interest for the  SLS partnership to quickly develop its originally intended 10 meter fairing in order to have a clear competitive advantage over vehicles like the Space X's future Starship which will have a 9 meter payload bay with probably an 8.1 meter dynamic envelope. However, Blue Origin's 7 meter in diameter New Glenn launch vehicle could be competitive since it should  also be capable of accommodating payload fairings up to 10 meters in diameter. With an 8.4 meter diameter for the SLS core vehicle, the SLS should be capable of accommodating  payload fairing sizes up to 12 meters in diameter with internal dynamic envelopes up to 11.1 meters in diameter.

SLS partner, Lockheed Martin, could supply basically the same Orion derived crew habitat module for the RLV-4 as it will for the Artemis National Team (Blue Origin, Lockheed Martin, Northrup Grumman, Draper) that will deploy a lunar crew lander to the Moon for NASA-- but without the added complexity and the expense of the ascent propellant architecture. 

A tall 10 meter in diameter SLS fairing should  be able to easily deploy two RLV-4 crew vehicles and other variants into orbit per launch-- cutting  RLV-4 deployment cost in half per launch. And the SLS should be able to deploy each vehicle to orbit with enough propellant for each vehicle to self deploy practically anywhere within cis-lunar space.

Utilizing propellant depots deployed at LEO, the RLV-4 should be able to transport crews from LEO to NRHO with less than 24 tonnes of propellant. 

But round trips between NRHO and the lunar surface could require nearly 48 tonnes of LOX/LH2.

Supplying a propellant depot at LEO with enough propellant for a RLV-4 crew mission to NRHO would only require a single Vulcan-Centaur launch (Vulcan-Centaur 562). 

However, supplying water or propellant to depots located at NRHO for a single lunar mission would require eight Vulcan-Centaur launches for the round trip between NRHO and the lunar surface plus an additional  four Vulcan-Centaur launches to NRHO to fuel the return trip of the RLV-4 back to LEO from NRHO. 

So a single lunar mission would require at least 13 Vulcan-Centaur propellant launches costing more than a billion dollars in propellant cost alone for a single mission. But such cost  would still be competitive with architectures that require at least one SLS/Orion launch plus additional commercial launches for a lunar crew missions. 

However, propellant cost for the RLV-4 architecture would fall dramatically once hydrogen and oxygen were being produced on the lunar surface. And that would mean that only a single Vulcan-Centaur propellant launch to LEO would be required for a lunar mission. 

Propellant destined for depots located at NRHO could come from the lunar surface. And a RLV-4 tanker variant could supply nearly 50 tonnes of water or propellant to an NRHO depot per launch from the surface of the Moon, up to 1200 tonnes of water or propellant until its four engines would have to be replaced, and up to 2400 tonnes of water or propellant to NRHO before the entire vehicle would have to be replaced. So two RLV-4 tanker vehicles deployed-- by a single SLS launch-- might be able to deploy 2400 to 4800 tonnes of lunar propellant to NRHO.

Simple solar  powered RLV-4 variants could serve as orbital propellant depots at LEO and NRHO and on the lunar surface.  Each depot could store up to 56 tonnes of propellant plus up to 100 tonnes of water for possibly making propellant.  The appropriate solar arrays for lunar and orbital RLV-4 derived propellant depots could be developed by SLS partner Northrup Grumman which already specializes in developing and deploying extraterrestrial solar arrays. 

By sharing the cost for the development and deployment of the RLV-4, starting in 2021, Space Launch System partners: Boeing, Aerojet Rocketdyne, Lockheed Martin, and Northrup Grumman could have the RLV-4 lunar lander and its variants ready to be deployed within a 10 meter in diameter SLS payload fairing by the year 2027.

By 2030, future RLV-4 passengers (astronauts and tourist) would simply have to take a Vulcan-Centaur-Dream Chaser or another commercial crew configuration to a commercial orbital habitat at LEO-- such as a commercial SLS derived Dry/Wet Shop mega habitat.  At the orbiting habitat,  passengers would transfer to an RLV-4 that has already docked at the habitat and already refueled at a nearby RLV-4 derived propellant depot or another commercial depot. 

It would take the RLV-4 about four days to transport up to 8 people to another private microgravity  habitat located at NRHO which would serve as a gateway to the lunar surface. There, passengers would transfer to another RLV-4 vehicle that was fueled on the lunar surface at a lunar outpost with enough propellant to transport them to the surface of the Moon in just 12 hours time. Or the RLV-4 that they arrived in could be refueled to transport them to the lunar surface. 

The RLV-4 Crew vehicles located at NRHO  could also utilize the cheap lunar propellant exported to NRHO depots for bi-weekly crewed missions to other areas on the lunar surface-- lasting 6 days-- before returning the the NRHO Gateway.  But if two RLV-4 vehicles are available at an NRHO Gateway, then weekly missions practically anywhere on the lunar surface could be conducted by a group of astronauts on a weekly basis.

Once passengers have completed their stay on the lunar surface, lunar propellant could be used to transport them on a four day trip from the Moon all the way back to LEO where they could take a Dream Chaser back to Earth, landing at any accommodating airport or spaceport in America.  

But as advantageous the RLV-4 would be as a commercial extraterrestrial crew lander, it would be even more economically viable as a lunar cargo vehicle for transporting exceptionally large and heavy SLS LEO launched payloads to the lunar surface. The RLV-4 as a heavy cargo vehicle will be discussed in my next article on the Reusable Landing Vehicle IV. 
 
Links and References

 Lunar Lander Vehicle Design Overview

Concept for a Crewed Lunar Lander Operating from the Lunar Orbiting Platform-Gateway

System Architecture Design and Development for a Reusable Lunar Lander

Boeing's Composite Tank Could Greatly Improve Launch Vehicles

CECE: Expanding the Envelope of Deep Throttling Technology in Liquid Oxygen/Liquid Hydrogen Rocket Engines for NASA Exploration Missions

 Blue Origin's National Team Lunar Lander

Vulcan-Centaur

Deploying a Ginormous SLS Derived Dry/Wet Workshop Habitat with a Single SLS Launch

Delta V Calculator