Tuesday, March 4, 2014

Cosmic Radiation and the New Frontier

Mars and its inner moon, Phobos
by Marcel F. Williams

The average woman on Earth is born with an approximately 38% chance of developing cancer sometime in her lifetime. And the average man  is born on our planet with about a  44% chance of developing cancer sometime in his lifetime.

Oxidative stress from the production of oxygen free radicals created during the metabolism of  proteins, carbohydrates, and fats (food) appears to be the primary cause of cancer and aging amongst humans and other animals on Earth. But ionizing radiation from space and from  the natural geology of the  Earth and in the food we eat and the water we drink can also  contribute to cancer and aging.

Ionizing radiation interacts with the tissue of humans and other animals by stripping away electrons from molecules, leaving behind  chemically active radicals that can be harmful to the cells of the human body.  As our civilization begins to expand off the Earth in the 21st century, the human species will encounter substantially higher levels of ionizing radiation from the cosmos.   Enhanced exposure to Galactic Cosmic Rays (GCR)  could significantly increase the rate of cancer and aging  and even brain damage amongst explorers and settlers in the New Frontier-- unless appropriate  means are  utilized to mitigate the potentially  deleterious effects  of cosmic radiation and major solar events.

Humanity and all other creatures on Earth live under a sea of air whose mass substantially reduces our exposure to cosmic radiation and the ionizing  effects of solar storms. The average amount of cosmic radiation exposures experienced on the surface of the Earth is approximately 0.039 Rem. Within inhabited US territorial areas, annual cosmic radiation exposure may be as high as 0.13 Rem (Wyoming)  or as low as 0.03 Rem (Puerto Rico).

The Earth's crust is also naturally radioactive thanks to uranium and thorium and a radioactive component of potassium (potassium-40) that is naturally found in our soil. Terrestrial soil contains about 6 parts per million  of thorium on average and 0.7 to 11 parts per million of uranium.  The Earth's oceans contain more than 4 billion tonnes of uranium 238 which has a radioactive half-life  of 4.47 billion years. The world's rivers dump about 32,000 tonnes of uranium annually into the world's oceans.

The human body, of course, is naturally radioactive thanks mostly to the naturally radioactive potassium in our bodies. Human body mass typically contains about 40 grams of potassium of which 1/1000 of this element is radioactive potassium-40. Humans also ingest food and water that is naturally radioactive thanks to the natural potassium, uranium and thorium contained in these foods. So internal radiation in the human body contributes about 0.04 Rem of annual radiation exposure.

However, the inhalation of  radon  222 and 220 is the predominant contributor of ionizing radiation in humans on Earth.  Radon gas is a radioactive by product from the decay of uranium or thorium and has a half-life of approximately 3.8 days. Radon exposes humans and other animals to approximately 0.23 Rem annually.

Smoking, however, can add even more radiation exposure to the human lungs than radon. The inhalation of tobacco contains  radionuclides  polonium 210 and lead 210. While a typical non-smoking American is exposed to about 0.36 Rem of radiation annually on Earth, a smoker can add an additional 0.28 Rem of radiation exposure to the human lungs.

Typical medical diagnostic procedures that use nuclear material can add 0.06 Rem of annual radiation exposure.

Ionizing Radiation on Earth

 0.039 Rem - Average annual amount of natural radiation in the human body
 0.2 Rem -  Average annual  internal radiation exposure due to the inhalation of  radon
 0.28 Rem - Annual radiation exposure for individuals who smoke cigarettes

 0.029 Rem - Average annual  exposure to terrestrial radioactive decay
 0.026 Rem - Average annual exposure to cosmic radiation in the US

0.36 Rem - Total average amount of natural and man-made ionizing radiation exposure for a person living in America


Boeing 747 (Credit: Boeing)

 The US legal limit for radiation exposure for workers is 5 Rem per year. Personal working at a nuclear facility are normally exposed to  0.115 Rems annually. However, personal aboard an airliner are typically exposed to 0.22 Rem per year.


Ionizing Radiation Exposure Limits on Earth

5 Rem - annual maximum radiation exposure allowed for radiation workers in the US

0.22 Rem - The average annual cosmic radiation dose experienced by flight personnel

0.12 Rem - Annual radiation exposure experienced by workers at a nuclear power plant

0.007 Rem - Annual radiation exposure while living in a stone, brick, or concrete building

0.003 Rem - Annual radiation exposure while living near the gate of a nuclear power plant

People who live near the gate of a nuclear power facility are normally exposed to about 0.003 Rem annually.  Living in a brick, stone, or concrete building would expose you to 0.007 Rem of annual radiation exposure. And each individual living inside of your home with you adds another 0.04 Rem of annual exposure. 

It should be noted, however, that there are places on Earth where people are exposed to substantially higher levels of ionizing radiation. A community of over 2000 people exist in Iran, that is naturally exposed to 1 to 25 Rem of radiation annually-- with no signs of any deleterious physical or reproductive effects on that population.

 In space, however,  exposure to ionizing radiation would be substantially above that typically experienced on Earth.

International Space Station (Credit: NASA)
On our planet of evolutionary origin, humans a typically exposed to 0.36 Rem annually. The annual exposure to cosmic radiation aboard the ISS (International Space Station) space station, however,  can range from 20 to 40 Rem depending on whether our solar system is experiencing solar maximum or solar minimum conditions. This is one of the reasons why astronauts typically remain aboard the ISS for only a few months. The solar maximum is a period when the sun has the most sunspot activity and the solar minimum is a period when the sun has the least sunspot activity. Solar maximum conditions can help to mitigate  the rain  of galactic cosmic radiation (GCR) within the Solar System. However, large solar flares often occur during solar maximum conditions.

Cosmic radiation levels become even worse as we leave the protective proximity of the Earth's massive globe and its surrounding magnetosphere. A space habitat located near the Moon at EML4 (Earth-Moon Lagrange point Four) for instance would be exposed to as much as 73 Rem annually  during the solar minimum. Being beyond the Earth's magnetosphere  also exposes astronauts to the heavy nuclei components of cosmic radiation.

Cosmic rays are mostly of galactic origin, resulting from super nova explosions. Approximately 85% of cosmic radiation particles are composed of hydrogen derived protons;  13%  are derived from helium atoms.   Heavy nuclei are accelerated particles  whose nuclei are derived from atoms heavier than hydrogen and helium. While heavy nuclei comprise only about 2% of cosmic radiation particles, they can do substantially more damage to biological tissue.

Astronauts in low Earth orbit, are only infrequently exposed to heavy nuclei bombardment thanks to the Earth's protective magnetosphere. Beyond the Earth's magnetosphere, however, astronauts frequently experience ' retinal flashes'. These visual flashes appear to be the result of heavy nuclei impacts upon the visual cortex of the human brain. Most cosmic ray ions pass harmlessly though the vacuous space between the atoms of the human body. But the relentless rain of cosmic radiation inevitably results in impacts upon our corporeal components. Heavy nuclei, especially the heaviest ions, can be particularly damaging to human tissue and especially to the human brain. Additionally, the particle  impacts of cosmic radiation impacts can produce significant amounts of secondary particles such as neutrons that can enhance the deleterious effects of cosmic radiation on biological tissue. 
 
Twenty seven Apollo astronauts returned to Earth after nearly two weeks beyond the Earth's magnetosphere with no significant deleterious effects to their body as the result of exposure to cosmic rays and its heavy nuclei component.  So a few days or weeks of cosmic ray exposure beyond the magnetosphere appears to have no significant impact on human health.

However, it is estimated that during a future 6 month journey to Mars, the nucleus of  one out of every three  cells in the human body would receive at least one hit from a cell damaging heavy ion. While most human tissue has the ability to repair itself, this is mostly not true for the neurons of the human central nervous system. So during a  mere six months of relentless cosmic ray exposure, heavy nuclei could potentially destroy a third of the neurons in the human brain-- without any repair or replacement. And rodents exposed to significant amounts of heavy nuclei bombardment have displayed some mental impairment.  So protecting the human brain from significant heavy nuclei exposure during multi-month or multi-year space missions should, obviously, be a priority.

Fortunately, astronauts traveling or living beyond the Earth's magnetosphere for months or for years could easily be protected from the dangers of heavy nuclei with only about 10 centimeters of lunar regolith, or an equal mass of less than 20 centimeters of water or ice.

But cosmic rays would not be the only danger astronauts could experience from ionizing radiation. A major solar storm could expose an unprotected crew to up to 1000 Rem over a short time period. Just 600 Rem of acute radiation exposure can cause radiation poisoning and even death. But 20 centimeters of water or ice would appear to be enough to reduce radiation exposure during a major solar event to well below NASA's 25 Rem per month radiation exposure limit.


Apollo 16 astronaut on the lunar surface (Credit: NASA)





Ionizing Radiation in Space

Interplanetary Space:

73 Rem - annual amount of cosmic radiation in interplanetary space during the solar minimum 

28 Rem -annual amount of cosmic radiation in interplanetary space during the solar maximum 


Surface of the Moon:

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

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

Surface of Mars:

33 Rem - annual rate of cosmic radiation on the surface of Mars beneath 16 gm/cm3 of Martian atmosphere during the solar minimum

8 Rem - annual rate of cosmic radiation on the surface of Mars beneath 16 gm/cm3 of Martian atmosphere during the solar maximum

Martian Surface (Credit: NASA)


Ionizing Radiation Exposure Limits for NASA Astronauts for a maximum 3% lifetime excess risk of cancer mortality

25 Rem - maximum 30 day exposure limit to ionizing radiation

50 Rem - maximum annual exposure limit to ionizing radiation 

100 Rem - maximum career exposure limit to ionizing radiation for  a 25 year old woman

150 Rem - maximum career exposure limit to ionizing radiation for  a 25 year old man

175 Rem - maximum career exposure limit to ionizing radiation for  a 35 year old woman

250 Rem -maximum career exposure limit to ionizing radiation for  a 35 year old man

250 Rem -maximum career exposure limit to ionizing radiation for  a 45 year old woman

325 Rem -maximum career exposure limit to ionizing radiation for  a 45 year old man

300 Rem -maximum career exposure limit to ionizing radiation for  a 55 year old woman

400 Rem -maximum career exposure limit to ionizing radiation for  a 55 year old man

NASA's annual limit for radiation exposure is 50 Rem. But the lifetime exposure limit for a 25 year old woman is only 100 Rem. Philosophically, I don't believe  that  a single space mission should ever end the extraterrestrial  career of a young individual. So the radiation shielding levels proposed here are designed to limit total cosmic ray exposure during an entire mission to less than 50 Rem.  A rotating interplanetary habitat module exposing astronauts to less than 25 Rem per year during an interplanetary journey would require nearly 50 centimeters of water to protect against cosmic radiation and major solar events. The internal shielding requirement for the inhabited areas for two rotating SLS fuel tank derived habitat modules would require nearly 240 tonnes of water shielding. This water shielding could be provided from lunar water resources shuttled to an interplanetary space craft located at one of the Earth-Moon Lagrange points.

ETLV derived Reusable Water Tanker Lunar Shuttle
Shielding astronauts below the 5 Rem per year requirement for terrestrial radiation workers in the US would require approximately 50 centimeters of iron shielding  or at least 4.5 meters of water. A rotating space station with two SLS hydrogen fuel tank derived habitat modules would require nearly 1900 tonnes of internal iron shielding. Fortunately, there's no shortage of iron ore in the lunar regolith. So exporting regolith bags heavily enriched with iron to shield rotating space stations located at EML4 or EML5 shouldn't be too difficult-- especially with reusable transport vehicles with replaceable CECE engines.

ETLV derived Reusable Lunar Regolith Shuttle

50 centimeters of water shielding would probably make it prohibitive to launch manned interplanetary vehicles from LEO.  The delta-v requirement to travel from LEO to Mars capture orbit would be around 5.2 km/s. However, the cheapest fuel source for an interplanetary vehicle would be from the Moon's low gravity well rather than from the huge gravity well of the Earth. The delta-v to LEO from Earth is over 9.3 km/s while the delta-v from the Moon to one of the Earth-Moon Lagrange points is less than 2.6 km/s. So it would  be cheaper to fuel the interplanetary vehicle at one of the Earth-Moon Lagrange points rather than at LEO.   The delta-v budget for traveling from an Earth-Moon Lagrange point to Mars Capture Orbit would be less than 2 km/s vs the 5.2 km/s delta-v of launching an interplanetary vehicle from LEO to Mars Capture Orbit.
Lunar Regolith Habitat with automatically deployed regolith wall. A similar habitat could be used to protect astronauts from cosmic radiation on the surface of Mars.
On the surface of the Moon or Mars, humans would be exposed to only half the amount of cosmic radiation thanks to the natural mass shielding of being on a planetary surface.

Interior configuration of a Regolith Habitat for the Moon or Mars
Two meters of Lunar or Martian regolith would be enough to lower annual radiation exposure below 5 Rem. The metallic shells of the pressurized habitat and the outer regolith wall would add additional radiation protection.   However, two meters of iron enriched regolith shielding could reduce radiation exposure within the Lunar or Martian habitat to terrestrial levels, if desired.

Links and References

Lifetime Risk of Developing or Dying From Cancer

Oxidative stress

What is Oxidative Stress

Biological consequences of oxidative stress-induced DNA damage in Saccharomyces cerevisiae

Oxidative DNA damage: mechanisms, mutation, and disease

THE HIGH BACKGROUND RADIATION AREA IN RAMSAR IRAN

Natural Radiation

Fueling our Nuclear Future

Space Faring The Radiation Challenge


Cosmic Ray Interactions in Shielding Materials


Galactic Cosmic Radiation Leads to Cognitive Impairment and Increased Aβ Plaque Accumulation in a Mouse Model of Alzheimer’s Disease

Radiation Protection for Human Missions to the Moon and Mars


Radiation Hazards and the Colonization of Mars: Brain, Body, Pregnancy, In-Utero Development, Cardio, Cancer, Degeneration


Mission to Mars: Health Risk Mitigation

(Rich Williams: NASA Chief Health and Medical Officer)


Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars


Regolith Biological Shield for a Lunar Outpost from High Energy Solar Protons


Lunar Station Protection: Lunar Regolith Shielding


Radiation exposure in the moon environment


Utilizing the SLS to Build a Cis-Lunar Highway

Wednesday, February 5, 2014

Utilizing the SLS to Build a Cis-Lunar Highway

The Earth seen rising above the Lunar horizon aboard Apollo 17, the last human mission to the Moon (Credit: NASA)
by Marcel F. Williams

By 2017,  American astronauts should be back in space aboard American made and launched private commercial vehicles. 2017 will also be the year that NASA launches it first true heavy lift vehicle since the days of Apollo.

SLS crew & cargo  vehicles
Some perceive the SLS as the antithesis of Commercial Crew development. But others view the Space Launch System as complimentary to Commercial Crew development. While Commercial Crew vehicles will enable Americans to have access to orbit again, the SLS launched  MPCV (Multipurpose Crew Vehicle) will give NASA the ability to launch humans practically anywhere within cis-lunar space-- and safely back to Earth's surface.

But  the Space Launch System could also be utilized to do a lot more.  

The SLS could be used to deploy a reusable cis-lunar architecture that could give passengers aboard Commercial Crew vehicles easy access to the surface of the Moon and to other commercially viable regions within cis-lunar space.

Below is a possible scenario that could make this happen by using a standard reusable ETLV (Extraterrestrial Landing Vehicle) derived architecture, starting in the year 2021. 

Nomenclature: 

EML (Earth Moon Lagrangian point); 
LEO (Low Earth Orbit); 
SLS (Space Launch System); 
MPCV (Multipurpose Crew Vehicle); 
CM (Command Module)
ETLV-2 (crewed Extraterrestrial Land Vehicle; 
ETLV-2R (Unmanned Automated ETLV-2); 
C-ETLV-4 (cargo lunar lander); 
WFD-OTV-5 (Water- Fuel Depot Orbital Transfer Vehicle); 
WFD-LV-5 (Water- Fuel Depot Lunar Landing Vehicle); 
RWT-LV-5 (Reusable Water Tanker Lunar Landing Vehicle); 
LRH (Lunar Regolith Habitat); 
Water Bug (Robotic Microwave Water Extraction Vehicle);
ATHLETE (All-Terrain Hex-Legged Extra-Terrestrial Explorer) 

Earth-Moon Lagrangian Points (Credit: NASA)
Before manned beyond LEO cis-lunar missions can begin, a new satellite communications system must be deployed at two of the Earth-Moon Lagrange points. Under this scenario, in  2020, a Delta IV heavy or an Atlas 401 will launch two satellites to EML2 (Earth-Moon Lagrange point 2). A second launch of either or the two vehicles will deploy two more communications satellites at EML1 (Earth-Moon Lagrange point 1).  This will allow continuous communications coverage for nearly the entire lunar surface. However, there will be some brief periods at some small mid-latitude regions that will be unable to communicate with the deployed constellation of Lagrange point satellites. But the deployment of satellite pairs at EML1 and EML2 should mostly eliminate the need for Earth-based tracking.


Delta-V Budgets & Destination Travel Times
 
LEO to TLI - 3.2 km/s dv

LEO to LLO (~2 days) - 4.5 km/s dv

LEO to LLO (~4 days) - 3.97 km/s dv

LEO to EML1 (~2 days) - 4.41 km/s dv

LEO to EML1 (~4 days) - 3.77 km/s dv

EML1 to or from LLO (~2 days) - 0.75 km/s dv

EML1 to or from  LLO (~3 days) - 0.64 km/s dv

LLO to or from the Lunar surface - 1.87 to 2.1 km/s dv

LEO: Low Earth Orbit; TLI: Trans-Lunar Injection; LLO: Low Lunar Orbit; 

EML1: Earth Moon Lagrange Point 1
(Credit John Connolly: NASA-JSC - 2012)
 
2021

Unmanned ETLV-2R docked with the WFD-OTV-5 fuel depot at ELM1
Derived from the Extraterrestrial Landing Vehicle (ETLV), the WFD (Water Fuel Depot) OTV (Orbital Transfer Vehicle) will utilize the same  cryotanks used for the ETLV-2. But these will be five in number instead of two, fixed within a higher cruciform in order to enhance the depot's ability to store the maximum amount of cryofuel. The WFD-OTV-5 would be capable of storing nearly 70 tonnes of LOX/LH2 fuel in addition to more than 100 tonnes of water. However, when the WFD-OTV-5 fuel depot is initially deployed at EML1 by the SLS upper stage, it will contain only 20 tonnes of fuel and no water because the SLS upper stage will only be able to deliver a little more than  30 tonnes to the Lagrange point.

The first ETLV-2 mission to the lunar surface under this scenario will be an unmanned mission to the South Lunar Pole. But first the SLS will launch The ETLV-2R will be launched by the SLS to the fuel depot at  EML1. Although the ETLV-2R would be nearly fully fueled, some additional fuel would be required  in order  for the vehicle's return to the Lagrange point after landing on the lunar surface.

Once on  the lunar surface, a variety of small mobile robots will be deployed to explore the polar region, test water extraction technologies, and return a variety of samples from lunar regolith. After a few days, or a few weeks, the ETLV-2R will return to L1.

A similar mission will occur with the third launch of the SLS in 2021. But the unmanned destination will be the North Lunar Pole. Again, after  a few days, or a few weeks, the ETLV-2R will return to L1.

So the end of both unmanned missions to the lunar surface will not only retrieve lunar samples from the lunar poles but will twice demonstrate the ability of the ETLV-2 vehicle to travel to and from the lunar surface from L1 on a single fueling of it's twin tanks. These two demonstrations of the ETLV-2,  to and from the lunar surface, should enhance the safety of the first crewed mission of the ETLV-2 in 2022.

MPCV (Multipurpose Crew Vehicle) Credit: NASA
The fourth launch of the SLS that same year will be the first manned mission of the MPCV. Astronauts will be sent to EML1 to dock with both  ETLV-2 vehicles in order to retrieve the lunar material for return to Earth. The SLS upper stage will also carry nearly ten tonnes of water destined for the L1 fuel depot. The WFD-OTV-5 will convert this water into liquid hydrogen and oxygen, producing more than enough fuel to replace the extra fuel extracted by a single ETLV-2 on its way towards a round trip to the lunar surface.

Astronauts will return to Earth aboard the CM of the MPCV, demonstrating the vehicle's ability to travel within cis-lunar space while also bringing back precious regolith samples from the north and south lunar poles.


2022
C-ETLV-4 and the ETLV-2 cargo and crew lunar landing vehicles

The first SLS launch of 2022 will send the C-ETLV-4 lunar cargo vehicle directly to the lunar surface. An ATLETE robot will deploy two small mobile excavators, two mobile sintering robots, and a single back hoe for depositing regolith into the walled interior of human habitat structures.

ATLETE robot for offloading cargo from the C-ETLV-4 (Credit: NASA)

The ATLETE robot will be routinely relied upon to unload habitats and machines from future C-ETLV-4 missions to the lunar surface.  

Lunar excavation robots (Credit: Astrobotic Technology and Carnegie Mellon)

The mobile excavators will be used to remove rocks and level the surface area for eventual sintering. Mobile sintering machines will move over the paved area using microwaves to melt the lunar regolith, creating a hard sintered layer approximately 0.5 meters deep and a smooth  solid surface approximately 3 to 5 cm deep.  Two widely separated  areas will be prepared by the excavators and the sintering machines. One area will be for the deployment of the Lunar Regolith Habitats. The other area will be exclusively prepared for landings by the ETLV-2, C-ETLV-2, Reusable Water Tankers, and  lunar fuel depots. Both areas will be connected to each other by a paved and sintered road perhaps a kilometer or more long.
Lunar sintering robot (Credit: Credit: Larry Taylor)

The battery powered or fuel cell powered back hoe won't be utilized until the Lunar Regolith Habitats are deployed.
An electric powered (battery or fuel cell) back hoes would have to be deployed to the lunar surface in order to deposit lunar regolith inside of the regolith walls of a Lunar Regolith Habitat (LRH) (Credit: Volvo)
The second launch of the SLS in 2022 will deploy the Lunar Regolith Habitat. The ATLETE robot will remove the habitat from the top of the C-ETLV-4 and transport it to the sintered area previously prepared for human habitat occupation.
Lunar Regolith Habitat (LRH): Lunar regolith is deposited by the back hoe within the 2 meter cavity between the pressurized SLS hydrogen tank derived habitat area and the automatically deployed exterior wall.  This will  provide micrometeorite and thermal protection in addition to protection against major solar events and a reduction of cosmic radiation exposure to below maximum levels for radiation workers on Earth. Power for the habitat is provided by the solar panel on top. And radiators on top of the habitat help to regulate and dissipate excess heat. A mobile water tanker will periodically pump lunar water into the habitat for washing, cooking, drinking, growing food, and for the production of air.

Once it is in position, the LRH-1 will automatically expand its solar panel to recharge the habitat batteries. An SLS hydrogen tank derived pressurized habitat will automatically expand its wall panels to produce a rigid and continuous wall around the pressurized area, creating a 2 meter wide cavity between the wall and the pressurized habitat. The lunar back hoe will deposit lunar regolith inside of the cavity to the top of the regolith wall which will also extend approximately two meters above the top level of the pressurized habitat. This will provide astronauts, scientist, and other visitors to the habitat with thermal and micrometeorite protection while also protecting them from the radiation of major solar events and while also reducing their annual exposure to cosmic radiation to levels below that required for radiation workers on Earth. This will allow astronauts and scientist to continuously remain at such habitats for more than a decade without coming close to their lifetime NASA limits for radiation exposure.

Within the 8.4 meter in diameter pressurized housing, there would be two levels each with approximately  55 square meters of area. So each habitat level would be about the size of a one bedroom apartment on Earth. In total, these two levels would have more floor area than the average family home in Great Britain.  Airlocks derived from the ETLV tanks would be located below the pressurized habitat area.

The last two SLS launches in 2022 will send the ETLV-2 and the MPCV to EML1. Again, the water will also be delivered to the fuel depot at L1 during the MPCV launch to EML1. After adding additional fuel, the ETLV-2 will deliver six astronauts, four Americans and two foreign guest  to the lunar surface. But they will only spend a few days or a few days on the lunar surface to inspect the lunar habitat and to collect more lunar samples.   The ETLV-2 will return the astronauts back to EML1 where it will dock with the MPCV for the crews return to Earth. The ETLV-2 will remain at L1 for future use once new fuel is being manufactured at L1 from lunar water resources. And it will be part of a fleet of three reusable vehicles starting in 2025.

2023

The solar powered WFD-LV-5 will be able to store Lunar water while also being able to  convert water into liquid hydrogen and oxygen for storage and distribution. Mobile cryotankers will extract cryofuels from the fuel depot for fueling space vehicles like the ETLV-2. Mobile water tankers supply the  fuel depot with Lunar water from the Water Bugs .

The first SLS launch of 2023  will send a solar powered water storage and cryofuel producing depot to the new lunar outpost. This will be followed just a few weeks later by the  C-ETLV-4 deployment of two mobile cryotankers derived from ETLV cryotank technology.  The mobile cryotankers will be used to extract cryofuels from the WFD-LV-5 lunar fuel depots in order to  refuel lunar landing vehicles. The mobile cryotankers will also be capable of scavenging residual fuel from the dormant C-ETLV-4 vehicles.

2023 will end with another pair of SLS launches for the ETLV-2 and MPCV  in order for another temporary human  visit to the lunar outpost . 

2024

Mobile water tanker next to a Water Bug robotic microwave water extraction vehicle. Water Bugs will recharge their batteries in the sunlight before venturing within shadowed craters for water mining. Mobile water tankers will extract the water from the Water Bugs for deposition at the fuel depot or in lunar water bags.
2024 will open with the SLS launch of a C-ETLV-4 to the lunar outpost. The ATHLETE robot will deploy two mobile water tankers plus a twin pair of Water Bug  microwave water extraction vehicles. Each Water Bugs should be able to extract as much as one to two tonnes of water from the lunar ice deposits per day. Excess water that can't be accommodated by the fuel depot, the mobile tankers, and the lunar habitats will be stored in water bags at the outpost.

A second SLS launch in 2024 will use the C-ETLV-4 to deploy a second habitat to the lunar outpost (LRH-2). The second habitat will double the area for human accommodations at the outpost. Each habitat will also serve as backup accommodations for the other in case there is a  serious malfunction at one of the habs.

Two SLS launches will end the year, bringing the first long term inhabitants to the lunar outpost. Some of these individuals will remain on the lunar surface for more than a year simply to determine if there are any deleterious physical or psychological effects for human individuals after living in a low gravity environment for more than a year. Before the first human attempts to venture to the orbit of Mars and to the Martian surface, some astronauts will have to eventually stay on the lunar surface as long as four years.  The results of these simple human test on the lunar surface could have enormous implications for humanity's future in the rest of the  solar system.

 2025

RWT-LV-5 water tanker next to the ETLV-2

A single SLS launch in 2025 will deploy two reusable lunar water tankers to the lunar outpost. Each vehicle will be capable of transporting more than 50 tonnes of lunar water to the EML1 fuel depots per flight while still being able to return to the lunar surface. With their CECE engines, each vehicle should be capable of at least ten round trips between ELM1 and the lunar surface before their engines or the entire vehicle is replaced.  


RWT-LV-5 transferring lunar water to the WFD-OTV-5 at ELM1
A single SLS launch will be used to deploy three partially fueled Orbital Transfer Vehicles (OTV-2) to LEO. Three expandable aerobrakes will accompany the three vehicles into orbit. Each OTV-2 will have enough fuel to reach the fuel depots at EML1. The OTV-2 is simply an ETLV-2 without the landing legs. So there will be minimal development cost for the vehicle. The aerobrake will be required in order to minimize fuel utilization upon returning from the Lagrange points to Earth orbit.
An OTV-2 preparing to dock with an Aerobrake Shield and another OTV-2 docked with an Aerobrake Shield

The deployment of the reusable OTV-2 vehicles will  mean that an SLS launch of the MPCV will no longer be necessary in order to transport astronauts to the Earth-Moon Lagrange points. However, NASA astronauts will still need to be able to get to LEO in order to access the OTV-2. But by 2025, NASA should have a wide variety of  Commercial Crew and foreign vehicles available to give NASA astronauts access to orbit.    

Russian Soyuz

Chinese Shenzhou

Dream Chaser (Credit: Sierra Nevada Co.)
Dragon (Credit: Space X)
CST-100 (Credit: Boeing)
SKYLON (Credit: REACTION ENGINES LTD)
 Commercial Companies could also have private commercial access to the lunar surface by simply purchasing an OTV-2 and an ETLV-2 from the American vendors that produce them. And this could allow private American companies them to provide access to the lunar surface to other nations and for wealthy space tourist and space lotto winners. So as early as 2026, reusable ETLV derived vehicles and fuel depots deployed by the SLS could allow private Commercial Crew companies to expand space tourism and other commercial enterprises all the way to the lunar surface.

OTV-2 docked with an ETLV-2 lunar landing vehicle at EML1
A single SLS launch will deploy two additional fuel depots (WFD-OTV-5) to LEO. One will use its own engines to reach EML1 while the other will remain at LEO to refuel the OTV-2 vehicles. Once a  LEO fuel depot begins to run low on fuel, it will transport itself to EML1 to be refueled with water from the lunar tankers in order to manufacture enough fuel for its redeployment back at LEO.

X-Ray of Skylab II with its SLS derived pressurized habitat at ELM1 (Credit: Griffin)

The final SLS launch in 2025 will be to deploy an SLS hydrogen fuel tank derived habitat with an internal hypergravity centrifuge to EML1. Lunar water exported to L1 will provide enough radiation shielding for the Lagrange point habitat to protect astronauts from a major solar event. The deployment of the lunar water shielded Skylab II will be first test  of a potential interplanetary habitat for possible manned missions to the orbit of Mars.

 Marcel F. Williams
© 2014 MuOmega Enterprises


Monday, January 27, 2014

The Future of Ocean Nuclear Synfuel Production

Artist’s rendition of the Russian floating nuclear power plant “Akademik Lomonosov” (Credit: SevMashZevod)
by Marcel F. Williams

Land based commercial nuclear power  is the safest form of electricity production ever created. No one died as the result of radiation exposure at the Fukushima nuclear facilities in Japan-- despite three meltdowns-- thanks to the inherent safety of the containment structures. But even if you include the mortality rate of the Chernobyl nuclear accident which didn't have a containment structure, the mortality rate for commercial nuclear energy is 90 deaths per trillion kWhr compared to:

Wind, 150 deaths per trillion kWhr

 Rooftop solar,   440 deaths per trillion kWhr,

Hydroelectric, 1400 deaths per trillion kWhr

Natural gas,  4000 deaths per trillion kWhr

Coal, a whopping 170,000 deaths per trillion kWhr.

However, these statistical facts have not alleviated the unreasonable fear that many have of commercial nuclear energy-- nor people's paradoxical phobia of radiation in general. This seems ironic since Americans exist in a society where radioactive materials are commonly used in nearby facilities such as hospitals and clinics. Americans are also  frequently exposed to much higher levels of cosmic radiation when they're flying in the upper atmosphere on airliners. Astronauts endure levels of radiation while in orbit much higher than what would be allowed for nuclear workers on Earth on a daily basis.  Americans also don't seem to have any fear about joining the US Navy to serve on nuclear powered aircraft carriers and submarines. And families don't seem to have any fears about  greeting their sons and daughters and husbands and wives when they depart from nuclear vessels on their return to shore.  

Still, there are many who have an almost innate fear of commercial nuclear power. And this unreasonable fear by some American's could seriously imperil the environment and the  quality of life for future generations.

Humans are currently living within an atmosphere that is alien to our species and even to our 2.6 million year old genus, Homo. Our use of fossil fuels has now pumped so much carbon dioxide into the air  that CO2 now comprises more than  400 parts per million of our atmosphere. These are levels of CO2 that have not existed on the Earth since the Pliocene, a warm epoch that spanned 5.3 million years ago until 2.6 million years ago when sea levels may have been as much as 40 meters higher than they are today. And as the polar  ice caps continue to melt and sea levels continue to rise, there are no signs that our civilization is currently stopping the increase of  greenhouse gasses into our atmosphere through the burning of fossil fuels. 

Yet the United States and most other industrial countries could easily stop the increase in CO2 levels into the atmosphere within the next 20 to 30 years if we simply built a lot more nuclear power plants for both  electricity and synthetic fuel production. There's already enough room at the more than 60   nuclear sites in the US to increase nuclear generation at each site to at least 8 GWe. That would be more than enough electricity to replace the electricity from fossil fuels in the US.

But what about transportation fuels for automobiles, trucks, ships, plains, and heavy ground vehicles?

Fortunately, a new generation of small nuclear reactors is about to emerge in the United States and in  the rest of the world. These small nuclear reactors offer the promise of an even more enhanced level of commercial nuclear safety while also substantially lowering the cost of manufacturing and deploying nuclear power through centralized manufacturing,  mass production, and transport by barge or rail to a nuclear power facility.

The first of this new generation of small nuclear reactors is being deployed by the Russians-- not the United States. But its not a land based reactor. It is a floating nuclear reactor. And floating nuclear reactors could be the key towards finally galvanizing broad acceptance of nuclear energy for all. 

Russia  intends to  mass produce floating 70 MWe nuclear power plants at shipbuilding facilities. These will then be towed   to coastal waters near industrial centers, towns and cities for the production of electricity and desalinated water.

The US once had the intention of deploying an offshore nuclear power facility as a way to avoid the increasing difficulties of licensing land based reactors. Four larger reactors were to be deployed by Westinghouse just 16 kilometers north of Atlantic City at the mouth of Great Bay. But licensing these off-shore reactors proved to be just as publicly difficult as land based reactors. And the project was eventually canceled.

But what if we deployed some floating nuclear reactors far out to sea-- far away from the  coastal environments of any town or city and the licensing headaches associated with coastal deployment.  Instead, these Ocean Nuclear power plants would be deployed hundreds or even over a thousand kilometers away from continental coastlines for the production of carbon neutral synthetic fuels. These clean synthetic fuels could then be shipped to any fuel port in the world for the production of electricity or for utilization as transportation fuel for automobiles, trucks, plains, and ships.
The conversion of seawater into methanol through nuclear electricity

The US Navy has recently revealed that they have developed a technology that can produce carbon neutral synthetic fuels from seawater by simply using a carbon neutral source of electricity. This technology takes advantage of the fact that the concentration of bound and dissolved carbon dioxide in seawater is  approximately 140 times greater than in the atmosphere. At the same time, the hydrogen contained in the seawater could be extracted through electrolysis and synthesized with CO2 to manufacture a variety of hydrocarbon fuels.

While the US Navy is focusing its attention on using nuclear or renewable OTEC technologies for manufacturing jet fuel at sea, the Navy's new technology  could be easily utilized to manufacture other carbon neutral fuels such as methanol, dimethyl ether, diesel fuel, and even gasoline.

The production of methanol at sea could allow floating nuclear power plants to ship this carbon neutral fuel  to practically any coastal port on Earth-- for  electricity production and for ground transportation fuel. Methanol tankers already exist and  come in a wide variety of sizes for transporting large quantities of methanol.

Methanol is relatively non-corrosive fuel that  remains at a liquid state at room temperature and atmospheric pressure. Methanol requires no specialized containment and can be handled the same way as other oil based liquid fuels.  Since methanol is easily biodegradable  in marine waters, an accidental  tanker spill would be much less damaging to the marine environment and to coastal beaches  than an oil or gasoline spill. 

Japanese Methanol Tanker (Credit: SHIN KURUSHIMA DOCKYARD CO)

For electricity production, methanol can be easily used in  modified natural gas turbines. Tests have shown that,  compared to natural gas,  methanol produces a  higher electrical power output due to the higher mass flow, and significantly reduces NOx and while also producing  no SO2 emissions at all. The clean burning characteristic of methanol are also expected to reduce maintenance costs for a converted natural gas turbine. So using carbon neutral methanol for electric power production would not only reduce global warming but would also mean cleaner air in general. Methanol can be easily pumped via pipelines to modified turbine power plants located in inland regions for distribution to electric power  all over the mainland United States. Of course, on islands such as Hawaii, methanol could finally end the islands'  dependence on high priced oil for electricity.

Methanol can also be used in fuel cell power plants which an be used for back up electricity for buildings or for homes. And methanol fuel cells are currently used to power portable electronic devices.

Methanol electric power plant at Point Lisas, Trinidad (Credit: Mendenhall Technical Services)
Methanol can also be used to power seagoing vessels. And some ocean vessels have already been designed to use methanol in order to reduce pollution from vessels using diesel fuel.

Methanol can also be easily converted into dimethyl ether (DME) through dehydration over a catalyst.  Only moderate modifications are required to enable a diesel fuel engine to burn dimethyl ether. And dimethyl ether is a much cleaner fuel than  diesel fuel for trucks and other heavy ground vehicles.

The further dehydration of dimethyl ether can convert it into high octane gasoline. This carbon neutral gasoline can be either mixed with existing fossil fuel derived sources of gasoline or can be used to completely replace gasoline derived from fossil fuels.

Conversion of Methanol into Dimethyl Ether and Gasoline for ground transportation vehicles
So nuclear power plants floating far out to sea in the worlds oceans could potentially supply carbon neutral fuels for both electricity and transportation fuel for the entire planet. Such Ocean Nuclear  facilities could be easily designed to withstand the havoc of hurricanes, cyclones, and other tropical storms while also being inherently immune to earthquakes and tsunamis. But storm related production disruptions could easily be avoided by locating such facilities in regions where the frequency of tropical storm formation is very infrequent.

The colored areas  are regions where cyclones and hurricanes are most frequently created in the world's oceans (Credit: National Oceanic and Atmospheric Administration)
But Ocean Nuclear complexes could still be located at latitudes where winter snow could be avoided in order to attract more employees to work at the remote ocean facilities. Semi-permanently docked cruise ships could be purchased by a large Ocean  Nuplex to provide housing, recreation, restaurants, shopping malls, small hospitals and schools for its nuclear power plant and synfuel operators and engineers and their families.

Since small nuclear reactors will be designed to produce 300 MWe of electricity or less, that means that thousands of small nuclear reactors would have to be mass produced and deployed to sea in order to replace America's  transportation fuel needs alone. If nuclear manufactured methanol were also required to  replace all of America's  peak load electricity production  then several hundred more small reactors would also have to be manufactured. Of course, if the US wanted to export carbon neutral fuels to other countries then thousands more small nuclear power plants would have to be built and deployed to sea.

Centrally manufacturing dozens or even  hundreds of small nuclear reactors in the US every year would dramatically reduce the capital cost  nuclear reactors and, therefore, the cost of synthetic fuels being produce from these Ocean Nuclear facilities.  This would mean millions of high wage manufacturing jobs being created on the American continent for the production of floating nuclear power plants that most Americans would never see. Such nuclear ocean synfuel production facilities could be clustered in an area less than 100 square kilometers (a 10 kilometers by 10 kilometers) while producing 25 to 50 GWe of power for synfuel production.

Large remote Ocean Nuplexes  could also be used to produce jet fuel, and even ammonia for fertilizer (synthesis of atmospheric nitrogen combined with hydrogen extracted from seawater through electrolysis).

US Navy nuclear aircraft carriers could  stop by such Ocean Nuclear complexes to refuel their vessels with jet fuel and also for some R&R for the crew at one or more of the Nuplex cruise ships which could feature a large variety of entertainment and shops  which could add more revenue for the Ocean Nuclear Complex.

Security for Ocean Nuclear facilities could also be provided by the US Coast Guard, easily affordable by a large nuclear complex without any tax payer expense. They would also, of course, have their own security forces.   

There might also be logistical advantages for locating floating  uranium extraction platforms within a few dozen or a few hundred kilometers of an  Ocean Nuclear Complex. There's more than 4 billion tonnes of natural uranium in seawater, enough to power and fuel all of human civilization for over 3000 years. And if the spent fuel is eventually recycled in next generation breeder reactors then uranium could supply civilization with power for more than 300,000 years. However, since the  uranium content of the oceans will be resupplied with its current uranium content in less than 150,000 years, marine uranium could, in theory, supply human energy needs for as long as humans remain on Earth. Of course, this doesn't even include terrestrial thorium supplies and potential extraterrestrial uranium and thorium supplies within the solar system in the future.

Floating airports located perhaps 10 to 100  kilometers  away from an  Ocean Nuplex could take advantage of their proximity to synthetic jet fuel,  cheap electricity, and desalinated water supplies.  Underwater electric power cables that stretch more than 500  kilometers away from their power source are already in existence.

Floating space launch facilities in the future could also take advantage of Ocean Nuclear complexes located near the Earth's equatorial regions to take full delta-v advantage  of the Earth's rotation. Launch facilities located less than 80 kilometers away from an Ocean Nuplex could utilize the abundant hydrogen and oxygen produced at the floating nuclear facility-- for cryogenic rocket fuel

Ironically, Ocean Nuclear facilities might also attract new communities of people living on floating artificial islands. Such floating island communities might be located just 100 to 500 kilometers away from an Ocean Nuclear complex, taking advantage of the cheap nuclear electricity and high paying jobs-- along with the warm climate and spectacular ocean views! But even at just 100 kilometers away from the floating Nuplex, from the balcony of your floating home, you'd still be at least 70  kilometers away from from being able to see the nuclear power facility over the curve of the beautiful blue horizon!

Marcel F. Williams

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Tuesday, January 14, 2014

Utilizing Space Shuttle Main Engines (SSME) for Early SLS Cargo Launches and Commercial Crew Destinations

Some of the SSME (RS-25D) in storage at the Kennedy Space Center (Credit NASA).
by Marcel F. Williams

NASA's future Space Launch System (SLS) won't be fully operational until it can utilize the new expendable RS-25E engines which probably won't be ready until the year 2021. However, NASA has 16 Space Shuttle Main Engines (SSME: RS-25D), previously used by the Space Shuttle stored away for use by the SLS. Since the SLS will utilize four engines per flight, the SSME could launch up to four SLS missions before the arrival of the expendable RS-25E engines. But the safety of astronauts launched on the SLS may depend on utilizing these engines on unmanned test missions.
 
2014


Simulated Video of Delta IV Heavy Launch of the CM of the MPCV
In 2014, NASA will use the ULA's Delta-IV heavy to test launch the Command Module (CM) of the future Multipurpose Crew Vehicle (MPCV),  placing it in low Earth orbit for reentry back on Earth. The  Service Module (SM) of the MPCV, however, will still be under development by the European Space Agency and won't be available to launch with the CM until   2017

2017
MPCV (Credit: NASA)
SLS/MPCV (Credit: NASA)


The SLS heavy lift vehicle will make its maiden launch in 2017 along with the complete version of the MPCV . This unmanned flight could be as simple as sending the MPCV to TLI (TransLunar Injection) or on more complex journeys to the Earth-Moon Lagrange points or to some other points of interest within cis-lunar space. 

After 2017, NASA has no SLS missions scheduled until 2021 when the first crewed missions of the SLS/MPCV are scheduled to begin and the new RS-25E engines are scheduled to be utilized. It would also mean that astronauts would be launched on top of the SLS after just one unmanned test flight! But  NASA would still have 12 SSME that could be utilized for cargo missions before 2021 that could further insure the safety of the SLS for manned spaceflight.

 During the Apollo era, there were two unmanned test flights of the Saturn V heavy lift vehicle before NASA finally took a chance and launched three American  astronauts into orbit around the Moon in December of  1968. The first unmanned test flight of the Saturn V in November of 1967-- was a complete success. However, there were some  problems with the second and third stages of the Saturn V during  the second unmanned test  in April of 1968

Of course, serious problems with the Apollo Command Module occurred  during a launch rehearsal test on  January 27th, 1967 which cost the lives of three American astronauts:  Virgil I. "Gus" Grissom (a former Mercury astronaut),  Edward H. White (the first American to walk in space), and  Roger B. Chaffee-- an astronaut who never got a chance to fly into space.

So as far as safety is concerned, I believe it would be prudent for NASA to launch the SLS more than just one time-- unmanned-- before actually placing living human beings on top of the new heavy lift vehicle. 
But that doesn't mean that such early SLS flights can't also be put to good use. Below is a proposal for two additional SLS flights before the first manned flight of the SLS/MPCV in 2021:


2019
CST-100 Commercial Crew Vehicle docked with the Olympus BA-2100 space station (Credit: Boeing)
Interior of the Olympus BA-2100 space station (Credit Bigelow Aerospace)

I propose that in 2019,  NASA should launch the Bigelow Aerospace company's Olympus BA-2100 space station to LEO for-- private commercial utilization. While Bigelow Aerospace would pay for the development of the BA-2100, under this scenario,  NASA would pay for the launch of the habitat in exchange for up to 60 days of annual exclusive use of the facility-- with the exception of Bigelow Aerospace maintenance personal aboard the space station. 

This would give Bigelow Aerospace the advantage of having a huge space station in orbit for exclusive  fee based Commercial Crew and foreign spacecraft  visitations at least 10 months out of the year.   Bigelow could still pay  private launch companys to deploy its smaller microgravity facilities (BA-300) nearby. This would allow small specialized microgravity labs to function without human interference while the human engineers and scientist took shelter at the larger Olympus space station until the experiments are completed and the results can be retrieved from the smaller facilities. Human access to the Olympus space station will, of course, depend on the availability of operational Commercial Crew spacecraft which should be available to NASA well before 2019.

2020
Skylab 2 (Credit: Brand Griffin)
Hypergravity Centrifuge (Credit: NASA)
 I also propose that in 2020, an orbital habitat derived from the SLS hydrogen  fuel tank, similar to the Skylab 2 proposal,  also  be deployed by the SLS to  LEO. Such a habitat could be equipped with a six meter in diameter internal hyper gravity centrifuge-- easily accommodated within the 8.4 meter interior diameter of the space station. This will enable NASA to see if one to two hours of hypergravity per day  can  significantly mitigate some of the deleterious effects of microgravity on the human body. The new NASA space station will also be supplied with enough water shielding to protect astronauts from major solar events while also  reducing their long term exposure to cosmic radiation. Again, NASA will need to utilize Commercial Crew services in order to access the SLS deployed NASA space station at LEO. In the 2020's, a similar SLS derived habitat will be placed at one of the Earth-Moon Lagrange points and could someday be used to house astronauts on interplanetary journeys.

So before the Space Launch System is fully operational in the early 2020s, the old Space Shuttle Main Engines could allow the SLS to deploy two enormous space stations: one privately owned  and one owned by NASA. Both stations could serve as places of refuge if one of the stations had to be abandoned in an emergency. And they could both serve  as  way stations for future reusable Orbital Transfer Vehicles headed towards the Earth-Moon Lagrange points or to Lunar orbit. A new generation of space stations would allow NASA to finally move beyond the ISS while focusing its efforts and finances on beyond LEO missions to the Moon and beyond.

Adding two additional unmanned SLS launches should help to enhance the launch vehicles safety and reliability before manned missions begin in 2021.  And, under this scenario, four SSME would still be available in case the  RS-25E engines are still not ready for manned SLS missions by 2021. 

Marcel F. Williams

 
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