Origami used to design ultra-compact solar arrays

BYU engineers have teamed up with a world-renowned origami expert to solve one of space exploration’s greatest (and most ironic) problems: lack of space.

Working with NASA’s Jet Propulsion Laboratory, a team of mechanical engineering students and faculty have designed a solar array that can be tightly compacted for launch and then deployed in space to generate power for space stations or satellites.

Applying origami principles on rigid silicon solar panels – a material considerably thicker than the paper used for the traditional Japanese art – the BYU-conceived solar array would unfold to nearly 10 times its stored size.

“It’s expensive and difficult to get things into space; you’re very constrained in space,” said BYU professor and research team leader Larry Howell. “With origami you can make it compact for launch and then as you get into space it can deploy and be large.”

The current project, detailed in the November issue of the Journal of Mechanical Design, is propelled by collaboration between BYU, NASA and origami expert Robert Lang. Howell reached out to Lang as part of landing a $2 million National Science Foundation grant in 2012 to explore the combination of origami and compliant mechanisms. (Joint-less, elastic structures that use flexibility to create movement.)

The particular solar array developed by the group can be folded tightly down to a diameter of 2.7 meters and unfolded to its full size of 25 meters across. The goal is to create an array that can produce 250 kilowatts of power. Currently, the International Space Station has eight solar arrays that generate 84 kilowatts of energy.

Howell said origami through compliant mechanisms is a perfect fit for space exploration: It is low cost and the materials can handle harsh solar environments.

“Space is a great place for a solar panel because you don’t have to worry about nighttime and there are no clouds and no weather,” he said. “Origami could also be used for antennas, solar sails and even expandable nets used to catch asteroids.”

Building a Lunar Base with 3D Printing

31 January 2013. Copyright European Space Agency (ESA). Reproduced with permission.

Lunar base made with 3D printing
Lunar base made with 3D printing

Setting up a lunar base could be made much simpler by using a 3D printer to build it from local materials. Industrial partners including renowned architects Foster + Partners have joined with ESA to test the feasibility of 3D printing using lunar soil.

“Terrestrial 3D printing technology has produced entire structures,” said Laurent Pambaguian, heading the project for ESA.

“Our industrial team investigated if it could similarly be employed to build a lunar habitat.”

Foster + Partners devised a weight-bearing ‘catenary’ dome design with a cellular structured wall to shield against micrometeoroids and space radiation, incorporating a pressurised inflatable to shelter astronauts.

A hollow closed-cell structure – reminiscent of bird bones – provides a good combination of strength and weight.

The base’s design was guided in turn by the properties of 3D-printed lunar soil, with a 1.5 tonne building block produced as a demonstration.

1.5 tonne building block
1.5 tonne building block

“3D printing offers a potential means of facilitating lunar settlement with reduced logistics from Earth,” added Scott Hovland of ESA’s human spaceflight team.

“The new possibilities this work opens up can then be considered by international space agencies as part of the current development of a common exploration strategy.”

“As a practice, we are used to designing for extreme climates on Earth and exploiting the environmental benefits of using local, sustainable materials,” remarked Xavier De Kestelier of Foster + Partners Specialist Modelling Group. “Our lunar habitation follows a similar logic.”

Multi-dome base being constructed
Multi-dome base being constructed

The UK’s Monolite supplied the D-Shape printer, with a mobile printing array of nozzles on a 6 m frame to spray a binding solution onto a sand-like building material.

D-Shape printer
D-Shape printer

3D ‘printouts’ are built up layer by layer – the company more typically uses its printer to create sculptures and is working on artificial coral reefs to help preserve beaches from energetic sea waves.

“First, we needed to mix the simulated lunar material with magnesium oxide. This turns it into ‘paper’ we can print with,” explained Monolite founder Enrico Dini.

“Then for our structural ‘ink’ we apply a binding salt which converts material to a stone-like solid.

“Our current printer builds at a rate of around 2 m per hour, while our next-generation design should attain 3.5 m per hour, completing an entire building in a week.”

Spurring Economic Growth and Competitiveness Through NASA Derived Technologies

(Washington, DC) — On July 12 the House Committee on Science, Space, and Technology’s Subcommittee on Space and Aeronautics held a hearing entitled, “Spurring Economic Growth and Competitiveness through NASA Derived Technologies.” The purpose of the hearing was to highlight the direct economic and societal benefits that investment in NASA has generated and to examine how best to ensure that continued investments will maintain a pipeline for future economic growth. Testifying before the Subcommittee were Dr. Mason Peck, Chief Technologist at the National Aeronautics and Space Administration (NASA); Mr. George Beck, Chief Clinical and Technology Officer at Impact Instrumentation, Inc.; Mr. Brian Russell, Chief Executive Officer of Zephyr Technology; Mr. John Vilja, Vice President for Strategy, Innovation and Growth at Pratt & Whitney Rocketdyne; and Dr. Richard Aubrecht, Vice President at Moog Inc.

The technical challenges of NASA’s space exploration, space science, and aeronautics missions have necessitated the development of unique skills and capabilities and required significant technological advances. These advances have contributed directly and indirectly to America’s economic strength, capacity for innovation, and global competitiveness by permeating our everyday lives in ways that are not readily apparent to all Americans.

“This hearing serves as an opportunity to remind the public on the connection between the federal government’s investments in space and the benefits to society,” said Ranking Member Jerry F. Costello (D-IL) in his prepared statement. “These contributions developed important products, such as satellite radio, medical diagnostics and aeronautical advances that have improved the safety, and fuel-efficiency performance of both commercial and military aircraft. In carrying out its missions and developing these technologies, NASA also has inspired young people to enter educational and career paths in science, technology, engineering and mathematics.”

In addition, NASA investments have helped fuel the innovation economy by expanding the knowledge base of scientists and engineers who are building the technologies of the future. “Knowledge provided by weather and navigational spacecraft, efficiency improvements in both ground and air transportation, super computers, solar- and wind-generated energy, the cameras found in many of today’s cell phones, improved biomedical applications including advanced medical imaging and even more nutritious infant formula, as well as the protective gear that keeps our military, firefighters and police safe, have all benefitted from our nation’s investments in aerospace technology,” stated Dr. Peck.

Industry also benefits from continued investments in NASA, applying the knowledge used to create new technologies and the derivative technologies themselves to create new commercial opportunities. “NASA has played a very significant role in the development of leading edge technologies,” said Dr. Aubrecht. “These core technologies and knowledge have enabled much economic growth in the USA, not only in aerospace industries but in many other sectors of the economy who benefit from the new technologies. The model of NASA investing in really hard problems and challenging American companies has enabled the development of many core, pre-competitive technologies. This model is an example of where a Federal investment in technology development has an enormous impact on the overall economy.”

Focusing on how NASA could expand partnerships, such as that between the agency and General Motors, which resulted in such innovative technologies as the robotic glove, Rep. Clarke (D-MI) urged NASA to seek opportunities to partner with small businesses, academic institutions, and economic development organizations. Congressman Clarke also questioned witnesses on how start-up companies might engage with NASA. “There are many start-up companies in Detroit, Michigan that are eager to partner with NASA to create jobs,” stated Congressman Clarke. “I look forward to working with NASA to facilitate that collaboration and spur economic growth in metro Detroit.”

NASA's "Ride the Light" Program

NASA has selected two game-changing space technology projects for development. The larger of the two awards has gone to NASA’s “Ride the Light” concept which seeks to provide external power on demand for aerospace vehicles and other applications. The concept uses beamed power and propulsion produced by commercially available power sources such as lasers and microwave energy. The project will attempt to develop a low-cost, modular power beaming capability and explore multiple technologies to function as receiving elements of the beamed power.

This combination of technologies could be applied to space propulsion, performance and endurance of unpiloted aerial vehicles or ground-to-ground power beaming applications. Development of such capabilities fulfills NASA’s strategic goal of developing high payoff technology and enabling missions otherwise unachievable with today’s technology.

NASA has awarded approximately $3 million for concept studies to multiple companies during this first phase of the Ride the Light project. Systems engineering and analysis during this first phase of the Ride the Light project will be done by Teledyne Brown Engineering in Huntsville, Ala.; Aerojet in Redmond, Wash.; ATK in Ronkonkoma, N.Y.; Carnegie Mellon University in Pittsburgh; NASA’s Jet Propulsion Laboratory in Pasadena, Calif.; and Teledyne Scientific, Boeing, and the Aerospace Corp., all located in Los Angeles. Following these studies, NASA expects to make an implementation decision in 2013.

The funding comes from NASA’s Game Changing Technology Division, which focuses on maturing advanced space technologies that may lead to entirely new approaches for the Agency’s future space missions and solutions to significant national needs.

NASA also has selected Amprius Inc. of Menlo Park, Calif., to pursue development of a prototype battery that could be used for future agency missions. Amprius is teaming with JPL and NASA’s Glenn Research Center in Cleveland on the project, with an estimated value of $710,000 for one year of development.

The Amprius project will focus on the material optimization of silicon anodes and electrolyte formulation to meet the agency’s low-temperature energy requirements. Amprius developed a unique ultra-high capacity silicon anode for lithium ion batteries that will enable NASA to dramatically improve the specific energy of mission critical rechargeable batteries. NASA requirements are unique because of the extremely low temperatures encountered in space.

“NASA’s Game Changing Technology Development program uses a rolling selection process to mature new, potentially transformative technologies from low to moderate technology readiness levels — from the edge of reality to a test article ready for the rigors of the lab,” said Space Technology Director Michael Gazarik at NASA Headquarters in Washington. “These two new projects are just the beginning. Space Technology is making investments in critical technology areas that will enable NASA’s future missions, while benefiting the American aerospace community.”

Orbital Propellant Depots: Building the Interplanetary Highway

by John K. Strickland, Jr.

August 5, 2011, was a highly significant date in the history of the space program. On that date, NASA announced contracts awarded to four aerospace companies to define demonstration missions to test the capabilities of cryogenic propellant depots. The contracts effectively created a design competition which would lead to the selection of a company to build an actual prototype depot. Cryogenic propellant depots are a critical component of our entire future space exploration and development effort.

A cryogenic propellant depot can rightly be called “a gas station in space.” If there were no gas stations along the interstate, you could only go about 150-200 miles from home by car before you would have to return. Just as gas stations extend the range of your car, orbital propellant depots would extend the range of your rockets.

For rockets and space vehicles, propellants usually take up 2/3 or more of their total mass. If a rocket puts a payload into an orbit from where the payload is intended to go further, such as to the Moon, that payload has to contain another smaller rocket and a final payload. Once in orbit, the first rocket’s upper stage is usually “out of gas” and since there are no gas stations in orbit right now, it becomes very expensive, useless space junk. If the “final” payload is expected to land on the Moon or Mars, it again has to have its own landing rocket and an even smaller final payload. This can be referred to as the Russian Nested Doll (Matryoshka) style architecture, with smaller rockets inside (or on top) of larger rockets. (A Russian Doll is a metaphor for an object with one or a series of similar objects inside it.) This is just the way things have had to be done since the start of the space age, since we have never had propellant depots in space. If a stage could be re-fueled in orbit, it could then be reused more than once.

When payloads are launched with cryogenic propellants, the propellants have to be loaded at the last minute since they start boiling off right away. A propellant depot does several very important things:

  1. It allows propellant to be loaded via docking ports from tanker rockets or propellant delivery capsules.
  2. It keeps the propellant from boiling away using multiple methods.
  3. It allows the propellants to be off-loaded into empty space vehicles and rocket stages just before a mission starts, while in micro or “zero” gravity in orbit, using the same or similar docking ports.
  4. It protects the fuel store with micrometeorite and space debris bumpers and maintains orbital stability and attitude, especially by aiming the solar shield towards the sun, and reports its condition and fuel status to the ground.

The typical propellant depot would contain liquid hydrogen and liquid oxygen, which respectively are about 430 and 300 degrees below zero Fahrenheit. To keep the propellant cold so it does not boil away, a depot can use four methods:

  1. Multi-layered super-insulation around the tank to reduce heat conduction.
  2. Structural isolation of the tank (like a thermos bottle) to reduce points where heat can be conducted through the structure into the tank. The depot will already be in a vacuum which is “free insulation.”
  3. A multi-layered sun-shield to reduce radiated heat from the Sun and Earth.
  4. An active cryo-cooler powered by solar panels to keep the fuel cold or to re-condense it as fast as it boils off.
Cryogenic propellant depot with single sunshade. Image credit: United Launch Alliance, B. Kutter, 2008.
Cryogenic propellant depot with single sunshade. Image credit: United Launch Alliance, B. Kutter, 2008.

NASA will probably select one of the four company designs to create a prototype depot. The designs will surely incorporate at least three of the four methods listed above. A prototype depot design may be based on an existing upper stage with its tanks. The initial prototype, which would cost between 200 and 300 million dollars, might not use the cryo-cooler part if it can demonstrate high efficiency with the static parts of its cooling system. Some companies have sophisticated and detailed designs which have existed for several years. One design might be able to keep boil-off losses to 1/10 of 1 percent a day or only 3 percent a month. It would probably hold at least 30 tons of propellants. Current cryo-coolers need to be scaled up from ones designed to keep space telescope instruments cold. For long duration propellant storage, a large cryo-cooler would definitely be needed, but it would not use a huge amount of power. The Spitzer space telescope maintained an insulated supply of liquid helium for its instruments without a cryo-cooler for 66 months.

A very significant result of having propellant depots in LEO is that it allows a spacecraft to be launched “dry” without fuel. This means that the total mass of the vehicle can be reduced by as much as 2/3 (the fuel), thus allowing a much larger spacecraft to be launched, or the same size spacecraft on a smaller rocket.

The same scenario can be used with depots placed at various destinations, such as geosynchronous orbit (GEO), L1, L2, or lunar or Mars orbit, where a depot would supply high performance cryogenic propellants to reach the Lunar or Martian surface. Depots can be sent to any destination orbit, since it is actually easier to keep the propellant cold away from the warm Earth’s infra-red radiation. The non-insulated or minimally insulated fuel tanks used by current spacecraft would lose all of their propellant during a trip to Mars, so only low performance (non-cryogenic) propellants have been used there to date. The depot can thus be considered as a component of a reusable in-space transport system that can do more than the sum of its parts.

Placing depots in remote destinations is the same as building gas stations in the mountains or the desert, far from the city. It allows you to conduct a full range of operations in the area of the depot with its secure propellant supply. If propellants can be created at the destinations from local materials, a local depot would provide a place to store them until they are needed. Since a depot can be a source of propulsion, energy, oxygen, and water, crew refuges may also be attached to remote depots as backup survival sites.

The cryogenic propellant depot is not only a critical part of the road beyond Low Earth Orbit (LEO), but would also be a boon for conducting routine operations in LEO. With the retirement of the Shuttle, the capacity to deliver large payloads to specific locations in LEO has been temporarily lost. Locations such as the space station or a propellant depot are usually thousands of miles from where a booster first enters orbit, and a booster, unlike the Shuttle, cannot move payloads around once in orbit.

Propellant depots offer an elegant solution to this problem because they could supply fuel to a reusable, insulated LEO space tug. The tug would remove the need for large payloads to carry their own propulsion systems to maneuver to locations such as the space station, the propellant depot, or other destinations. A space tug could also be used to rescue astronauts if they became stranded in an orbit away from the space station. A space tug was originally to be part of the space station program but was never funded. Such a space tug could be based on existing upper stages or upgrades of existing space station cargo delivery vehicles.

A re-usable LEO to GEO space tug can remove the need for the expendable upper stages currently needed to reach GEO. Such a tug would not be possible without an orbital propellant depot where it can refuel.

A low or Zero Boil-Off (ZBO) depot can be considered to be a propellant accumulator, since multiple small tanker vehicles can add propellant until the supply is sufficient for large missions. The value of a propellant accumulator can be illustrated by its potential use had it been included in the now-cancelled Constellation architecture. In that architecture, an Ares V would have been launched with a full lunar stack similar to that carried by a Saturn V, minus the crew capsule. NASA would have then had about two weeks to launch a crew to the orbiting lunar stack on an Ares I before enough of the hydrogen fuel boiled off to turn the multi-billion dollar stack into orbiting space junk and wasting the entire Ares V launch. Even a medium-sized cryo-cooler docked with the lunar stack in orbit would have been sufficient to keep the fuel cold. With a depot, a lunar stack could be launched dry (meaning a much lighter stack is needed, thus requiring a smaller booster, or alternatively a larger stack with the same size booster). The stack would rendezvous with the depot, load the dry stage that takes the stack to the Moon with propellant, and the stack would then leave Low Earth Orbit.

Using depots to re-fuel upper stages would mean that Heavy Lift Vehicles (HLVs) can be smaller than they would otherwise need to be. For example, a Falcon Heavy class HLV (50 metric tons) would be able to launch a dry payload equivalent to what an SLS class HLV (125 metric tons) would be able to launch wet, at a small fraction of the cost.

The new commitment of NASA money to propellant depot design lends more credibility to the concept. There are no fundamental barriers to building depots — it is an idea which has existed on paper for decades but for which no development money has been available. The longtime lack of funding acted to reduce the credibility of the idea despite its inherent value and technical feasibility. In addition, the business-as-usual focus on expendable launchers fostered a general lack of interest. Funding for depots was suggested by the second Augustine Commission in 2009 and is supported by Dr. Robert Braun, NASA Chief Technologist, as part of NASA’s advanced technologies initiative.

The four companies receiving the NASA contracts are Analytical Mechanics Associates Inc., Hampton, Va.; Ball Aerospace & Technologies, Boulder, Colo.; The Boeing Co., Huntington Beach, Calif.; and Lockheed Martin Space Systems Co., Littleton, Colo. Each contract is worth up to $600,000.

References/Links

This article as a permanent web page on the NSS website

Evolving to a Depot-Based Space Transportation Architecture (PDF paper 2010)

A Practical, Affordable Cryogenic Propellant Depot Based on ULA’s Flight Experience (PDF paper 2008)

Realistic Near-Term Propellant Depots: Implementation of a Critical Spacefaring Capability (PDF paper 2009)

LEO Propellant Depot: A Commercial Opportunity? (PDF slides 2007)

The Case for Orbital Propellant Depots (slides 2008)

Space Gas Station Would Blast Huge Payloads to the Moon (Popular Mechanics article 2009)

On-Orbit Propellant Resupply Options for Mars Exploration Architectures (PDF paper 2006)

NASA interest in an interplanetary highway supported by Propellant Depots (NASAspaceflight.com 2011)

Cryogenic Propellant Depots Design Concepts and Risk Reduction Activities (PDF slides 2011)

Beam it up, Scotty: 3D Printing may have space applications

Tools and mechanical parts might be “beamed” up to a space station or a lunar or Mars base using technology that has in recent years become a central process in design prototyping known as 3D printing or SLS (selective laser sintering). In this technology, an object is scanned and a powdery substance is converted via a heating process into a duplicate solid form. A striking demonstration of this technology can be seen in this 4-minute video clip from the National Geographic Channel.

A variation of the technology might also be used for lunar materials production by fabricating items from lunar regolith. Markus Kayser has demonstrated a prototype “Solar Sinter” device that uses the power of the sun to produce glass-like objects made from desert sand. You can view a 6-minute video demonstration of the device as tested in the Sahara Desert.

SpaceShip Two – First Feathered Flight

Feathered
SpaceShip Two “Feathered”
Image Credit: Clay Center Observatory

Om 4 May 2011, Virgin Galactic’s SpaceShip Two completed its third test flight in twelve days, and this one was special. For the first time, Virgin Galactic’s rocket plane deployed its twin tail sections in the position designed to allow it to softly return to the Earth’s atmosphere from the vacuum of space. Virgin Galactic noted:

After a 45 minute climb to the desired altitude of 51,500 feet, SS2 was released cleanly from VMS Eve and established a stable glide profile before deploying, for the first time, its re-entry or “feathered” configuration by rotating the tail section of the vehicle upwards to a 65 degree angle to the fuselage. It remained in this configuration with the vehicle’s body at a level pitch for approximately 1 minute and 15 seconds whilst descending, almost vertically, at around 15,500 feet per minute, slowed by the powerful shuttlecock-like drag created by the raised tail section. At around 33,500 feet the pilots reconfigured the spaceship to its normal glide mode and executed a smooth runway touch down, approximately 11 minutes and 5 seconds after its release from VMS Eve.

The feathered configuration is used during re-entry into the Earth’s atmosphere from the 100 km height obtained by the sub-orbital spaceship. The configuration is very stable during the free fall, which means the pilot has a hands-free re-entry. High drag combined with the light weight of the spacecraft means the skin temperature remains low.

ATV-2 Johannes Kepler


Keeping the International Space Station (ISS) supplied will become an increasing challenge with the retirement of the US Space Shuttle in 2011. This is the first in a series to look at how the ISS will be serviced for the next five or six years.

The Japanese were schedule to launch their second H-II Transfer Vehicle (HTV-2) resupply mission today, 20 January, but weather has caused the mission to be rescheduled for a possible launch on Saturday.

The Russians fly their Progress spacecraft on resupply missions, and the next one is scheduled for 28 January.


Johannes Kepler ATV-2
ATV-2 Johannes Kepler
Image Credit:
European Space Agency (ESA)

The European Space Agency (ESA) has flown their Automated Transfer Vehicle (ATV-1 or Jules Verne) to the ISS once before on 9 March 2008, and their next launch is coming up on 15 February 2011.

On the commercial side, Space X has successfully orbited their Dragon spacecraft and returned to Earth. Their next test flight is penciled in for July and the first resupply mission is penciled in for December.

And Orbital Sciences Corporation has their first cargo delivery test of its Cygnus spacecraft scheduled for December 2011.

That summarizes the partners working to support the International Space Station.

Here is a more detailed look at the European Space Agency’s ATV system.


The 20 ton Johannes Kepler ATV has a cargo capacity of up to 7 metric tons. The composition of this load can vary depending on the mission:

  • 1.5 to 5.5 metric tons of freight and supplies (food, research instruments, tools, etc.)
  • up to 840 kilograms of drinking water
  • up to 100 kilograms of gases (air, oxygen and nitrogen)
  • up to four metric tons of fuel for orbit correction and up to 860 kilograms of propellant to refuel the space station.

The spacecraft is compose of two main sections. The first is the ATV Service Module (below, left), which is not pressurized, includes propulsion systems, electrical power, computers, communications and most of the avionics. The ATV uses four main engines and 28 small thrusters to control the navigation of the spacecraft. Four solar panels are deployed after launch and supply 4800 Watts of power to the batteries and the electrical systems.

The second component is the Integrated Cargo Carrier (below, right). The large section in the front is pressurized and comprises about 90% of the cargo volume. It handles all the dry cargo, including the racks on each side. The inhabitants of the International Space Station access this area through the hatch in the Russian docking system.


Service Module
ATV Service Module & Four Main Engines
Image Credit: ESA

Service Module
Cutaway of ATV Cargo Carrier
Image Credit: ESA


The Equipped External Bay of the Integrated Cargo Carrier (ICC) holds 22 spherical tanks of different sizes and colors (below, left). These tanks are used to re-supply the Station with propellant for the International Space Station propulsion system, various gases (air, oxygen, and nitrogen) and water for the crew.

The contents of these tanks are delivered to the Station through dedicated connections, or through manually operated hoses.


Service Module
ATV Liquid Resupply Tanks
Image Credit: ESA

Docking Module
Russian Docking Module
Image Credit: ESA


The ATV uses the Russian-made docking equipment sensors to perform the approach and docking sequence (above, right). The procedure is the same as with the Soyuz manned capsules and the Progress resupply spacecraft.

The Russian docking system enables physical, electrical and propellant connections with the Station. Access to the ICC is through the Russian hatch.

Once the ATV is securely docked, the crew can enter the cargo section and remove the payload, which usually includes maintenance supplies, science hardware, parcels of fresh food, mail and family tapes or DVDs.

Galactic Cosmic Rays (GCR) – The 800 Pound Gorilla

The most recent issue of Science News (18 December 2010) has the following notes from 17 December 1960:

HEAVY SHIELD UNNECESSARY — Heavy shielding as protection for an astronaut against space radiations may not be necessary, at least for trips of less than 50 hours and at distances not greater than 618 miles from earth…. [B]iological specimens were encased in different types of metal to test their effectiveness as shielding materials. Some specimens were shielded only by the thin aluminum covering of the specimen capsule and the comparatively thin shell of the recovery capsule. Radiation dosimeters showed that aluminum provided better shielding properties than lead and that any heavy metal such as gold or lead becomes a hazard during a solar flare as high energy protons interact with these heavy metals to create damaging X-rays.

However, if you want to travel to the Moon or journey anywhere within the Solar System, Galactic Cosmic Radiation will require that the human crew is protected. Let’s take a look at the problem and the research required to test and implement solutions.

Synopsis

The GCR problem arises from interstellar atomic nuclei traveling near the speed of light striking the structure of a spacecraft. The resulting shower of secondary particles cause radiation damage. The Earth is protected by the Van Allen belts and a deep atmosphere. Brief journeys such as an Apollo mission does not expose the astronaut to dangerous dosages. However, astronauts on such a journey are at risk from Solar flares (Solar Particle Events – SPE). SPEs can be mitigated with layers of hydrogen rich materials such as polyethylene or water. GCRs, however, require spaceships on long journeys of more than 100 days, or habitats on the Lunar or Martian surface, to be surrounded by tens of meters of water for passive protection, or magnetic shields for active protection. Either solution is extremely heavy and makes space flight prohibitive in terms of propellant requirements.

The following sections discuss each aspect and provide references for further reading about the problem

The Source of GCR

Galactic Cosmic Rays come from outside our Solar System, but from within our galaxy, the Milky Way. They are comprised of atomic nuclei that have been stripped of their electrons. These nuclei can be any element. Common elements are carbon, oxygen, magnesium, silicon, and iron with similar abundances as the Solar System. Lithium, Berylium and Boron are overabundant relative to the Solar System ratios.

The Shielding Problem

Early on, it was suggested that cosmic rays could penetrate the Apollo spacecraft. From “Biomedical Results of Apollo” section IV, chapter 2, Apollo Light Flash Investigations we have the following account:

Crewmembers of the Apollo 11 mission were the first astronauts to describe an unusual visual phenomenon associated with space flight. During transearth coast, both the Commander and the Lunar Module Pilot reported seeing faint spots or flashes of light when the cabin was dark and they had become dark-adapted. It is believed that these light flashes result from high energy, heavy cosmic rays penetrating the Command Module structure and the crew members’ eyes. These particles are thought to be capable of producing, visual sensations through interaction with the retina, either by direct deposition of ionization energy in the retina or through creation of visible light via the Cerenkov effect.

When Galactic Cosmic Rays collide with another atom, such as those contained in the Aluminum, Stainless Steel or Titanium structures of a spacecraft, they can create a shower of secondary particles, These secondary particles cause radiation damage in living organisms (humans).

The problem is creating sufficiently powerful barriers to these extremely energetic nuclei.

Researching Solutions

  • Passive Shielding – At least for solar flares (SPE), some solutions are easier than the GCR problem.
  • Active Shielding
  • Fast Passage to avoid exposure (VASIMR propelled craft). A proposal for vapor core reactors integrated with VASIMR engines.
  • A proposal for studying radiation and other factors associated with long term human occupation of space.
  • NASA’s Space Radiation Program in association with the Brookhaven National Laboratories.
  • In 2008, the National Academies of Science published Managing Space Radiation Risk in the New Era of Space Exploration, which included chapter 6: Findings and Recommendations
  • From the Summary in Radiation Shielding Simulation For Interplanetary Manned Missions
      Inflatable Habitat + shielding

    • Hadronic interactions are significant, systematics is under control
    • The shielding capabilities of an inflatable habitat are comparable to a conventional rigid structure – Water / polyethylene are equivalent
    • Shielding thickness optimisation involves complex physics effects
    • An additional shielding layer, enclosing a special shelter zone, is effective against SPE
      Moon Habitat

    • Regolith shielding limits GCR and SPE exposure effectively
    • Its shielding capabilities against GCR can be better than conventional Al structures as in the ISS

See also the recent article in New Scientist about radiation hazards. A tip of the hat to ParabolicArc.

Virgin Galactic – First Free Flight

VSS Free Flight
Virgin Galactic’s SpaceShipTwo Enterprise during its first free flight
Image Credit: Virgin Galactic

Commercial spaceflight took another step forward this past Sunday, 10 October 2010.

Virgin Galactic’s SpaceShipTwo, named Enterprise, was dropped from its mother ship at 45,000 feet and successfully completed maneuvers and landing at the test facilities in the Mojave Desert. Enterprise is designed to carry two pilots and six passengers to an altitude of over 100 kilometers.

Sir Richard Branson, founder of Virgin Group, who was present during the first successful flight, commented that “This was one of the most exciting days in the whole history of Virgin.

The flight was designed to test the release mechanics from the mother ship and then verify the handling and stall characteristics as well as the lift to drag ratio. A complete set of landing maneuvers were executed at a high altitude, and the ship then made its final descent and landing.

Scaled Composites pilot, Pete Siebold, said “The VSS Enterprise was a real joy to fly, especially when one considers the fact that the vehicle has been designed not only to be a Mach 3.5 spaceship capable of going into space but also one of the worlds highest altitude gliders.”

Virgin Galactic will continue testing the new rocket ship during the coming year, and expects to fly its first commercial passengers within 18 months.

George Whitesides, former Executive Director of the National Space Society and current CEO of Virgin Galactic, was also present at the historic flight. Whitesides said, “To see the world’s first manned commercial spaceship landing on a runway is a sight I always dreamed I would behold. Now, our challenge going forward will be to complete our experimental program, obtain our FAA license and safely bring the system into service at Spaceport America, New Mexico.”


First Crewed Flight

First Crewed Flight of VSS Enterprise on 15 July 2010
Image Credit: Virgin Galactic