Utilizing Lunar Water Resources for Human Voyages to Mars

At EML4, an OTV-400 interplanetary booster  undocks with a fuel depot (WPD-OTV-400) before proceeding to dock with the  Odyssey interplanetary spacecraft. 

by Marcel F. Williams

Long interplanetary journeys to  Mars, or to the orbit of Venus, or even to some of  the NEO asteroids could take several months or even years before their human occupants finally return to the relative safety of the Earth's surface. Such interplanetary voyages will require a substantial tonnage of water  for drinking, washing, the preparation of food,  the manufacturing of oxygen for air,  the production of  liquid oxygen and hydrogen for propellant, and for appropriately shielding humans inside of  habitat modules from the dangers of cosmic radiation and major solar events.

NASA delta-v estimates for  achieving Mars Transfer Orbits from LEO during the 2030s range above 3.8 km/s to just below 5 km/s-- just to reach the vicinity of Mars. Additionally,  a LEO departure for Mars would require launching the huge amounts of water and propellant for the voyage out of the Earth's enormous gravity well. This would require a delta-v ranging from 9.3 to 10 km/s.

However, if  crewed interplanetary vehicles are launched from an Earth-Moon Lagrange point, the delta-v requirements to achieve a Mars Transfer Orbit would be substantially lower. The delta-v requirements for departing cis-lunar space from one of the Earth-Moon Lagrange points could be less than 2 km/s-- especially if an Earth flyby or an Earth and Moon flyby (even better) are taken advantage of during the initial trajectory burns.

Providing water and propellant for  crewed interplanetary mission from the lunar surface to an Earth-Moon Lagrange point would also have a substantially lower delta-v requirement.  A  delta-v of less than  2.6 km/s would only be required to supply water and propellant to an interplanetary gateway at an  Earth-Moon Lagrange point. Contrast that with the  enormous  9.3  to 10 km/s delta-v that is need to  supply propellant and water to an interplanetary vehicle located at LEO.  The lunar supply of water and propellant to an interplanetary spacecraft at an  Earth-Moon Lagrange point would also have the additional economic advantage of being able to use single stage reusable vehicles. 

Earth-Moon Lagrange Points, the optimal gateways to interplanetary space within cis-lunar space.

So  launching  crewed interplanetary space craft to Mars from one of the Earth-Moon Lagrange points (L1, L2, L4, or L5) has a substantial delta-v advantage over launching crewed interplanetary spacecraft from LEO--  if such spacecraft are supplied with fuel and water from the surface of the Moon. 

During the 2030s, entering High Mars Orbit during a Conjunction Class Mission (330 to 560 day stays) would require an additional delta-v of 0.9 to 1.9 km/s, while entering High Mars Orbit during  Opposition Class Missions (60 day stay)  would require an additional delta-v trajectory burn ranging from  0.9 to 3.8 km/s. The additional delta-v requirements for reaching High Mars Orbit adds further support for minimizing the initial delta-v requirements when departing from cis-lunar space. So, again, supply fuel and water from the Moon from an Earth-Moon Lagrange point gateway would appear to be the optimal way to begin crewed interplanetary journeys. 

But how much water is there on the lunar surface? And how technologically difficult would it be  to extract large quantities of water from the lunar regolith?

A spectral analysis of the ejecta plume from the impact of  a Centaur upper stage  into the  Cabeus crater at the lunar south pole was conducted in 2009.  The analysis indicated that the lunar regolith in the shadowed crater contained water ice with concentrations ranging from 2.7% to 8.5% by mass. This suggest that  in some of the permanently shadowed craters at the southern pole, the lunar regolith there may contain as much as  27 to 85 kilograms of ice per tonne. 

The dark purple and blue areas represent neutron emissions from the Moon's polar regions that indicate  hydrogen-rich regions on the lunar surface covered by desiccated regolith (Credit: NASA) .  

In the Moon's northern polar region, the Mini-RF on board the Chandrayaan-1 orbiting probe strongly suggest that 40  craters in the northern polar region my contain as much as 600 million tonnes of water-ice. So there is clearly no shortage of  water resources on the lunar surface.

In order to provide enough water for human activities at a lunar outpost, a cis-lunar transportation system, and to supply propellant and mass shielding for five Conjunction or Opposition Class missions to Mars during the 2030s: 2030, 2033, 2035, 2037, and 2039, at least 500 to 1000 tonnes of water is going to have to be annually manufactured on the lunar surface.

A lunar water and fuel manufacturing depot along side of mobile LOX and LH2 storage tanks and a mobile microwave water extraction robot (Water Bug).

NASA researchers have demonstrated that a simple one kilowatt microwave oven could extract as much as a tonne of water from the regolith at the lunar poles over a one year period. A single mobile robot with a 100 kw powered microwave oven, therefore, should be  able to annually extract 100 tonnes of water from the regolith from the shadowed areas at the lunar poles. Ten such mobile microwave units might be able to extract 1000 tonnes of water per year from lunar polar regolith resources.

Solar extraction of water from lunar regolith brought from permanently shaded lunar craters at the lunar poles. Transparent domes allows sunlight to heat a layer of lunar regolith from the top while solar heated metal tubes below filled with methanol heat the regolith from below. Water vapor is deposited within regolith insulated cold trap canisters.

However, a simpler method may only require sunlight to passively extract water from the lunar regolith. If one tone of regolith from the shadowed areas of the  lunar poles is composed of  approximately 5% water ice then mobile lunar excavators capable of digging up and depositing at least one tonne of regolith into a solar heater could produce at least 50 kg of water per day (18 tonnes of water per year). Just a few electric powered or fuel cell powered excavation robots on the lunar surface could, in theory,  deposit at least one ton of icy regolith to a solar heater per hour (more than 400 tonnes of water per year).

A reusable water tanker shuttle on a microwave sintered launch pad after being loaded with lunar water and lunar fuel for its flight to a water and propellant depot at one of the Earth-Moon Lagrange points.

The Odyssey interplanetary vehicles would be crewed spacecraft capable of transporting 12 astronauts to High Mars Orbit and back to cis-lunar space using solar photovoltaic powered propellant producing water depots supplied with water from the lunar surface. The Orbital Transfer Vehicle (OTV-400) and the IAGH (Interplanetary Artificial Gravity Habitats) would both be derived from the SLS fuel tank technology.

 The OTV-400 would use  a common bulk-head LOX/LH2 fuel tank derived from the SLS fuel tank technology. An IVL(Integrated Vehicle Fluids) type of technology would be used to utilize ullage gases for attitude control. Space Works has proposed a similar type of OTV using IVL technology that would store more than 450 tonnes of LOX/LH2 fuel. However, the OTV-400 would also use photovoltaic powered cryocoolers to  virtually eliminate any hydrogen and oxygen boil-off.
 
The twin habitat modules of the IAGH would rotate to produce a 0.5g simulated gravity for the six humans inside each module. The IAGH would also  be  appropriately water shielded to protect  its most radiation vulnerable occupants (25 year old female astronauts) from excessive exposure to  cosmic radiation and its  heavy nuclei component in a addition to major solar events-- for up to four years-- during solar minimum conditions. 50 cm of water shielding would be required to appropriately shield the light weight twin SLS fuel tank derived living areas: 118 tonnes of water shielding for each habitat module, 236 tonnes of shielding in total. 

A reusable Orbital Transfer Vehicle (OTV-400) for transporting crewed artificial gravity habitats to the orbits of Mars, Venus, or to the NEO asteroids. While some of the ullage gases are utilized for attitude control, most of the ullage gases are reliquified by photovoltaic powered cryocoolers to prevent fuel loss, a technology already developed by NASA.

Conjunction Class Missions would only require one reusable OTV-400  storing close to 400 tonnes of LOX/LH2 propellant. The higher delta-v Opposition Class Missions will require two reusable OTV-400 boosters. Entering orbit around Mars and reentering cis-lunar space will also require the IAGH  to dump the water shielding from its habitat modules in order to substantially reduce the Odyssey's mass just before the final trajectory burns to enter Mars orbit or to enter cis-lunar space.

Coupled with a large water storage tank and a photovoltaic powered electrolysis plant  and cryocoolers, the OTV-400 would function as a water storage and hydrogen and oxygen producing propeelant depot (WPD-OTV-400). Still equipped with its own rocket engines, it could self deploy itself practically anywhere within the inner part of the solar system  while still being able to manufacture LOX and LH2 anywhere where there is a source of water.

The WPD-OTV-400 water and propellant depot would have the ability to transport itself to Mars orbit from the Earth-Moon Lagrange points after producing enough fuel for its on flight and filling up with enough stored water originating from the Moon. However,  once water is being manufactured on Deimos and Phobos, using the same technologies employed on the lunar surface, propellant from the lunar surface will no longer be required to replenish water and propellant supplies in orbit around Mars. 

Reusable Odyssey I interplanetary space craft with a crew of 12 at EML4 in a trajectory burn configuration for a Conjunction Class mission to High Mars Orbit  in the year 2033. 

After its initial trajectory burns on its way to Mars, the  OTV-400 boosters and the ETLV-2 vehicles (Extraterrestrial Landing Vehicles) would separate from the IAGH  and re-dock at its central axis.The Odyssey would, therefore, be reconfigured  to produce artificial gravity for its 12 person crew for their multi-month journey to Mars.   Liquid carbon dioxide rockets housed in each habitat module, would be used to rotate or to stop the rotation of the Odyssey. Cables will extend from the IAGH core more than 100 meters from the central axis of the vehicle. A series of light weight cylindrical metal or ceramic shells woulds also expand outwards creating rotational arms that would act as levers to increase, decrease, or stop the rotation of the Odyssey. 

Reusable Odyssey II interplanetary space craft with a crew of 12 at EML4 in a trajectory burn configuration for a 1000 day Opposition Class mission to High Mars Orbit (60 day stay) to explore the martian moons Deimos and Phobos while also deploying  satellite constellations at Sun-Mars L1 and Sun-Mars L2 to provide global communications for future human missions to the surface of Mars.

After several months of travel through interplanetary space,  the Odyssey would reconfigure itself again to prepare for an Orbital Insertion trajectory burn and the water shielding within IAGH modules would be dumped into space.  But after a day or two in Mars orbit, the Odyssey will once again reconfigure itself to produce artificial gravity for its crew. The  water shielding for the habitats could be fully  restored within a few hours or a few days from a pre-deployed  WPD-OTV-400 already in high Mars orbit. Returning to Earth will also require the Odyssey to be refueled by the orbiting water and propellant depot in Mars orbit.

Once in high Mars orbit, each fully fueled  crewed ETLV-2 vehicle would have enough fuel to travel to one of the Martian moons for a few days of exploration and sample retrieval  and back to the Odyssey. And if they wanted to travel to the martian moons a second time then they could refuel at the orbiting Mars depot (WPD-OTV-5).

A slowly rotating Odyssey II in an interplanetary configuration to provide a simulated gravity of  0.5 g  for six crew members in each of the  IAGH habitat modules. 

Since the Odyssey is intended for reuse (ten times with its RL-10 engines) for future interplanetary missions, a trajectory burn will be required to return to the Earth-Moon Lagrange points after the trajectory burn for Trans-Earth Injection from Mars orbit. Again, this will require the Odyssey to completely dump its water shielding before the burn. Once the crew is back within cis-lunar space, they will only be a few hours away from protective shelters on the lunar surface or just a few days away from the Earth's surface.

After the 12 person crew completes their 60 day mission in High Mars Orbit, the Odyssey II converts from it's artificial gravity configuration to a trajectory burn configuration for its Trans-Earth Injection burn to begin its journey back to cis-lunar space.

 Because the major Odyssey components are reusable, the recurring cost for the interplanetary vehicle should be substantially lower that other interplanetary vehicle concepts that utilized expendable interplanetary boosters. The Odyssey's RL-10 or RL-10-like rocket engines could also be periodically replaced after perhaps ten round trips between cis-lunar space and Mars orbit which could further reduce their recurring cost.

The human safety advantages of using  lunar water resources for an SLS derived reusable artificial gravity producing  interplanetary spacecraft   deployed at one of the Earth-Moon Lagrange points should also be substantial:


1. The significantly reduced delta-v requirements at an Earth-Moon Lagrange point for fueling and mass shielding a crewed interplanetary vehicle should alleviate any pressure to significantly reduce the appropriate mass shielding of habitat modules against the dangers of cosmic radiation and major solar events. 50 cm of water shielding should also eliminate the possibility of space career ending radiation exposure during a single interplanetary mission for the most vulnerable occupants to radiation.

2. The rotating interplanetary artificial gravity habitats (IAGH) could significantly or totally eliminate long periods of exposure to the  deleterious physical effects of a microgravity environment

3. Having twin AGH habitats allows astronauts the enhanced safety of being able to seek refuge in the opposite habitat in case there is a serious life safety malfunction at the other habitat.

4. The more comfortable accommodations of the spacious SLS derived artificial gravity habitats could significantly reduce the psychological stress experienced by the drew  during several months or years of interplanetary travel.

5. The dangers and the complexity of direct, high-energy aerobraking into the atmospheres of Mars or during a return to directly to Earth would be avoided by limiting the Odyssey's flight path to travel only between the Earth-Moon Lagrange points and High Mars Orbit.

6. With at least one partially fueled  ETLV-2 (Extraterrestrial Landing Vehicle) connected to the Odyssey, any major malfunction of the OTV-400 during an orbital capture trajectory could allow astronauts to safely enter Mars orbit or cis-lunar space via the ETLV-2 vehicle or vehicles.  Even though this would mean the loss of the Odyssey spacecraft, the crew could still safely enter Mars orbit or cis-lunar space via the ETLV-2. However, Entering Mars orbit aboard an ETLV-2, without the Odyssey IAGH would require that an appropriately mass shielded space station already be pre-deployed in Mars orbit.



References and Links


Considerations for Designing a Human Mission to the Martian Moons (NASA)

A Study of CPS Stages for Missions beyond LEO (Space Works)

Mission and Implementation of an Affordable Lunar Return (Spudis & Lavoie) 

 Using the resources of the Moon to create a permanent, cislunar space faring system (Spudis & Lavoie)

Evolving to a Depot-Based Space Transportation Architecture (ULA)

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

 Utilizing the SLS to Build a Cis-Lunar Highway

Cosmic Radiation and the New Frontier

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

In 2031, a reusable OTV-400  places a boom contracted artificial gravity habitat (AGH) and two Extraterrestrial Landing Vehicles (ETLV-2) into high Martian orbit  for a  60 day mission of human exploration of the two Martian moons, Deimos and Phobos, before refueling at a pre-deployed orbiting  fuel depot for the return trip to cis-lunar space.

The relatively weightless conditions of orbital and interplanetary space are inherently deleterious to human health. Humans and other terrestrial animals have evolved their physical and physiological attributes under our planet's heavy gravitational environment.

On the surface of the  Earth, the human heart has to counter the downward pull of gravity  in order to pump adequate amounts of blood to the head and torso when people are standing erect, while blood flowing to the lower limbs is aided by the pull of gravity. But under the microgravity conditions of space,  human blood disproportionately flows to the head and torso while blood flow to the lower limbs is reduced. This makes the human face look puffy while their legs become thinner.

Such blood flow redistribution can  sometimes cause nausea and headaches when astronauts first arrive in orbit but usually disappears after a few days in space. But other minor but annoying problems can be experienced under weightless conditions, including:

1.  Weight loss: the less strenuous conditions diminish appetite, resulting in weigh loss which could become excessive if astronauts don't exercise and eat regularly. 

2. A degraded sense of smell and taste: your favorite foods could taste a little different under microgravity

3. Clumping of tears and perspiration: there's no gravity to force trickles of water to run off the human body 

4. Facial and speech distortions: the face becomes  puffy and the voice tone and pitch becomes more nasal

5. Increased flatulence: since digestive gasses no longer rise towards the mouth, their is an increase in gas being expelled through the posterior orifice

The problems listed above could be viewed as only a minor inconvenience on short missions into space. But during long interplanetary journeys  lasting months or years, such problems could be annoying enough to enhance stress and increase tension aboard ship.

But there are other, more serious health problems that the human body may be subject to during months or years in a microgravity environment:

1. Astronauts can lose between 1 to 1.5% of their bone mass in a single month

2. Without regular exercise, astronauts can lose up to 20% of their muscle mass in just 5 to 11 days.

3. A microgravity environment can reduce  cardiovascular fitness

4. Vision problems of varying degrees of severity can occur especially in older men

5. Blood flow redistribution in a microgravity environment can effect medicines ingested or injected into the human body. 

6. Fluid loss and bone demineralization in a microgravity environment can increase the blood's calcium concentration, increasing the risk of an astronaut developing kidney stones.

7. The infected spray from the cough or the sneeze an ill person on board floats in the air instead of falling to the floor, enhancing the spread of infection aboard ship-- especially in a confined environment.

Returning to Earth after  a few months aboard the ISS, the blood pressure of some astronauts drops abnormally low 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. 

Since conjunction class missions to Mars may take more than seven months, there could be some question as to whether or not astronauts would  have the physical ability to perform a mission to the Martian surface.  Astronauts would have to endure weightless for several more months during their  return trip from Mars to Earth.

One possible solution to the deleterious effects of weightlessness would be temporary periods of high simulated gravity (hypergravity).   On Earth, sustained bed rest on a flat surface that is tilted  a few degrees backwards can simulate the deleterious effects of a microgravity environment, causing more blood to rush towards the head and less blood to flow into the hind limbs. But if such beds are attached to a short radius centrifuge, high levels of G forces can be experienced at the human foot level.

Short radius hypergravity centrifuge could help to mitigate the deleterious effects of a microgravity environment on the human body (Credit NASA).

Hypergravity studies have shown that protein synthesis in the leg muscles can be sustained if 2.5 G is experienced for just one hour a day at the foot level during a 21 day period. This suggest that daily exposure to a brief period of  hypergravity in space may be an effective counter measure, mitigating the loss of muscle mass in a microgravity environment. 

Production of the 8.4 meter section of the  SLS hydrogen fuel tank. Such components could be used for reusable common bulkhead interplanetary vehicles or for pressurized human space habitats (Credit Boeing Aerospace).

Short radius hypergravity centrifuges require a radius of more than 3 meters to accommodate the human body. So space habitats utilizing such  centrifuges would have to have unobstructed  internal diameters of more than six meters. Habitats derived from the SLS hydrogen fuel tanks could have an internal diameter as large as 8.4 meters. Even surrounded by 50 centimeters of water for radiation mass shielding would still give a habitat 7.4 meters in diameter of space to accommodate such machines. 

SLS  hydrogen fuel tank derived Skylab II concept (Credit Griffin).

So an SLS hydrogen fuel tank derived habitat such as the Skylab II concept could easily accommodate a short radius hypergravity centrifuge to keep astronauts and possibly even space tourist healthier while in orbit or on an interplanetary journy.

However, it has yet to be determined whether short centrifuge hypergravity machines can also alleviate some of the other serious physical and physiological problems associated with a weightless.  And temporary hypergravity would have no effect on the enhanced spread of infectious diseases and some of the minor but annoying problems associated with weightlessness.

To eliminate all of the problems associated with a microgravity environment during long periods of space travel, a continuous artificial gravity environment would be required.

In order to mitigate the physiological effects of Coriolis, a habitat capable of producing at least 0.5g of simulated gravity (higher than the gravity on the Moon and Mars) would require a rotation of  approximately 2rpm (rotations per minute) and a radius of at least 112 meters. That  would require a rotating habitat approximately  224 meters in diameter if twin counterbalancing pressurized habitats were utilized.

Artificial Gravity Habitat (AGH) located at EML4 or EML5 and radiation shielded with iron enriched lunar regolith to reduce annual radiation levels for inhabitants to below those allowed for radiation workers on Earth.

A rotating habitat derived from SLS hydrogen fuel tank technology under this scenario would  require two SLS launches to deploy and assemble the structure at one of the Earth-Moon Lagrange points. A core module would contain a pressurized docking section, solar panels,  plus extendable cables, boom, and twin  cable elevators on each side. Two external air locks derived from the SLS upper stage oxygen tank technology would also be deployed during this launch.

AGH core module featuring elevators and cable attachment rings for the habitat modules.

A second SLS launch to the Lagrange points would deploy two twin pressurized habitat modules that would connect to each side of the previously launched the core module. The total structural mass of the AGH (Artificial Gravity Habitat) is assumed to be less than 60 tonnes before the habitat modules are internally mass shielded by water for interplanetary journeys or with iron enriched regolith for permanent space stations.

Each AGH pressurized habitat module would provide shielded living area equivalent to a small two story homes, providing a spaciously comfortable environment for scientist and astronauts who may have to live in the confined simulated gravity habitats for several months or even a few years. 

AGH habitat module that can be internally shielded with 50 cm of water for interplanetary journeys or 50 cm of iron enriched regolith for permanent space stations.

A crewed or automated OTV-2 vehicle (derived from the ETLV-2) would be utilized to help assemble the AGH structure: docking the external airlocks to the sides of the core module and docking the habitat modules to both ends of the core module.

OTV-2 orbital transfer vehicle positioning the second habitat module to be docked with the core module of an Artificial Gravity Habitat (AGH) at EML4 or EML5.

The expandable boom would be rigid enough to allow thruster pods located at the ends of the habitat modules to increase or decrease its rate of the AGH rotation while the boom and internal cables are fully extended. Steel cables within the external boom would connect the AGH habitat modules to the core module. The cables would pull in the habitat modules before rocket burn maneuvers were conducted, expanding them again once the delta-v maneuvers are over. The hollow boom would also enhance the visibility of the AGH when crewed vehicles are approaching the central axis to dock.

For interplanetary journeys, the twin habitat modules would be shielded with water 50 cm thick. This would reduce astronaut's exposure to cosmic radiation to approximately 20 Rem per year during the solar minimum while also protecting astronauts from major solar events. Internally water shielding two levels of inhabited area within a pressurized habitat would add approximately 118 tonnes of weight to each habitat. Twin habitats, therefore, would add an additional 236 tonnes of mass to an interplanetary vehicle. So an AGH shielded for interplanetary travel would weigh nearly 300 tonnes, not including the additional mass for food, water, and air for the crew. Over the course of 1000 days, a crew of ten would add at least 50 tonnes of additional  mass to the vessel unless their was significant recycling of both air and water.

Reusable SLS hydrogen tank derived  OTV-400 utilizes a common bulkhead tank architecture for storing up to 400 tonnes of cryogenic fuel for interplanetary journeys. IVF technology would utilize ullage gases for tank pressurization and attitude control. Solar powered cryocoolers would eliminate fuel boil-off during long interplanetary journeys. 

At 5.2 km/s to 7 km/s, the delta-v requirements for transporting such a massive vehicle  from LEO to  Mars orbit could be prohibitive.  However, if the interplanetary vehicle was  fueled and  launched from the Earth-Moon Lagrange points to high Mars orbit, the delta-v requirements could be less than 2 km/s.

Delta- V Budget from Cis-Lunar Space to  Mars Orbit

EML1 or EML2 to Mars Capture Orbit -- 1.64 km/s

EML4 or EML5  to Mars Capture Orbit - 1.93 km/s

EML1 or EML2 to Low Mars Orbit ------ 3.04 km/s

EML4 or EML5 to Low  Mars Orbit ----- 3.33 km/s

LEO to Mars Capture Orbit ---------------- 5.2 km/s

LEO to Low Mars Orbit -------------------- 7 km/s

Liquid hydrogen and oxygen fueled cryogenic propulsion stages have been proposed by SpaceWorks with a fuel capacity of over 450 tonnes but with n inert weight of less than 30 tonnes. The ULA has proposed a cluster of six ACES boosters with a LOX/LH2 fuel capacity of approximately 700 tonnes.

Under this scenario, a common bulkhead LOX/LH2 fuel tank derived from the SLS hydrogen tank technology is utilized for a reusable interplanetary booster in order to minimize development cost. The OTV-400 would be capable of storing up to 400 tonnes of fuel for crewed interplanetary journeys to Mars, Venus, and the near Earth asteroids. The standard 400 tonne fuel tank is also utilized for large fuel depots under this scenario in order to minimize cost. Integrated Vehicle Fluid (IVF) technology would utilize ullage gases for tank pressurization and attitude control. Cryofuel boil-off would be eliminated during interplanetary journeys by using  solar powered cryocoolers.

A single SLS launch would be required to deploy the OTV-400 to LEO with enough fuel to travel to an Earth-Moon Lagrange point for refueling. Less than 350  tonnes of fuel would probably be required for a crewed interplanetary journey to high Mars orbit,  including two fully fueled Extraterrestrial Landing Vehicles.

Launching human interplanetary missions from the Earth-Moon Lagrange points to high Mars orbit rather than from LEO has several advantages.

1. To travel from an Earth-Moon Lagrange point to high Mars orbit requires less than 2 km/s of delta-v. But traveling from LEO to high Mars orbit would require more than 5 km/s of delta-v.

2. The delta-v requirement to transport water for shielding and fuel to an Earth-Moon Lagrange point is less than 2.6 km/s. The delta-v requirement to transport water to LEO is more than 9 km/s

3. The vehicles required to transport water to from the Moon to the Earth-Moon Lagrange points could be used for at least ten round trips before their CECE engines would have to be replaced or a new vehicle would be required. The vehicles required to transport water from Earth to LEO, however, would be expendable and could only be used once.

Reusable OTV-400 attached to a contracted AGH during propulsive delta-v maneuvers and a reusable  OTV-400 attached to an expanded rotating AGH after the completion of a propulsive delta-v maneuver.

The interplanetary vehicles return trip from Mars to cis-lunar space would require the OTV-400 to refuel at a previously deployed depot in high Mars orbit.  Fuel depots in orbit around Mars would initially use water exported from the lunar surface to manufacture fuel. But eventually, lunar derived water producing and exporting machines and vehicles would be placed on the surfaces of Deimos and Phobos for water production and export to the Mars orbiting fuel manufacturing depots. 

An OTV-400 derived fuel depot  (WFD-400) capable of producing cryogenic hydrogen and oxygen from stored water. The WFD-400 would be capable of transporting itself  anywhere within cis-lunar space or into orbit around Mars or Venus.

For permanent space stations at the Earth-Moon Lagrange points or in orbit around Mars, the twin habitat modules would require a radiation shield of  iron enriched regolith about 50 cm thick to reduce cosmic radiation exposure to less than 5 Rem annually (maximum allowed for radiation workers on Earth) during the solar minimum. That would require nearly 1865 tonnes of mass shielding (932 tonnes of iron enriched regolith for each habitat module). This would require one or two SLS launches of twin reusable regolith shuttles to the lunar surface-- depending on whether or not the CECE engines on the regolith shuttles are replaced after ten round trips.

Delta-V requirements to transport water for fuel, air, drinking, and mass shielding to LEO or to the Earth-Moon Lagrange Points

Lunar surface to EML1 --------------------- 2.52 km/s

Lunar surface to EML2---------------------- 2.53 km/s

Lunar surface to EML4 or EML5 ---------- 2.58 km/s

Lunar surface to LEO (with aerobraking) - 2.74 km/s

Earth's surface to LEO ----------------------- 9.3 km/s

Earth's surface to EML2 -------------------  12.73 km/s

Earth's surface to EML1 -------------------  13.07 km/s

Earth's surface to EML4 or  EML5 -------  13.27 km/s

Reusable lunar tankers capable of delivering more than 50 tonnes of water or regolith to the Earth-Moon Lagrange points. Their CECE engines should be capable of at least ten round trips from the lunar surface to the Lagrange points before the engines, or the entire vehicle, needs to be replaced. So after ten round trips, each vehicle would be capable of delivering more than 500 tonnes of fuel or regoltih  to the Earth-Moon Lagrange points.

Transporting an iron enriched regolith shielded  space station to high Mars orbit  would obviously require a much larger vehicle than the OTV-400. A light sail with a surface area of at least 100 square kilometers should be able to transport a few thousand tonnes to Mars within a years time. But if light sail technology is still not available,  vehicles capable of transporting a few thousand tonnes to Mars orbit  could easily be assembled by clustering four or more OTV-400 tanks around a core tank. A cluster of five OTV-400 vehicles would create an OTV-2000 interplanetary booster. A cluster of seven OTV-400 boosters would create an OTV-2800 interplanetary booster. Large clustered LOX/LH2 fuel tanks have also been proposed by the ULA for their human interplanetary vehicle concepts.

 The fuel requirements for such large interplanetary vehicles under this scenario would require one or two SLS launches of reusable water shuttles to the lunar surface. The lunar tankers would then transport water manufactured on the Moon to  fuel manufacturing depots at L4 or L5. Again, such lunar tankers should be capable of at least ten round trips before their CECE engines would need to be replaced. 

OTV-2000 is comprised of a cluster of five OTV-400 boosters.

The  OTV-400 would give NASA and possibly private space companies the delta-v capability to conduct  human missions from the Earth-Moon Lagrange points to the orbits of Mars and Venus, and to the NEO asteroids, and to Sun-Earth L4 and L5 as long as fuel depots for the return trip to cis-lunar space  are pre-deployed at those destinations.

 OTV-2000 and OTV-2800 class of interplanetary boosters could  enable human journeys from the Earth-Moon Lagrange points to the asteroid belt to places like Ceres and Vesta, again with WFD-OTV- 2000 or 2800 fuel depots pre-deployed in orbit around such large asteroids.

 Marcel F. Williams
© 2013 Mu Omega Enterprises


Links and References

What if you were born in space

Weightlessness and Its Effect on Astronauts

Effect of spaceflight on the human body (Wikipedia)

Artificial gravity maintains skeletal muscle protein synthesis during 21 days of simulated microgravity

 NASA Gives Artificial Gravity a Spin

 Short Radius Centrifuge (SRC)

Skylab II

Artificial Gravity (Wikipedia)


Artificial Gravity Visualization, Empathy, and Design

Space Launch System's Liquid Hydrogen Tank Under Construction

Cosmic Radiation and the New Frontier

Utilizing the SLS to Build a Cis-Lunar Highway

An SLS Launched Cargo and Crew Lunar Transportation System Utilizing an ETLV Architecture


A Study of CPS Stages for Missions beyond LEO

A Study of Cryogenic Propulsive Stages for Human Exploration Beyond Low Earth Orbit

Evolving to a Depot-Based Space Transportation Architecture