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.


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.

The Garden on The International Space Station

The latest crop harvested from the Garden on the International Space Station is Mizuna lettuce. The lettuce was returned to Earth for scientific research, aboard the Discovery shuttle in April 2010.

The greenhouse, first sent up in 2002, has been used for 20 plant growth experiments so far. Now, a second unit has been added, and the lettuce crop was the first experiment to test different conditions side by side.

For many years, the experiments have sought to confirm Earth side results which show that minimizing water usage and salt accumulation would lead to healthier crops. During this experiment, two different root growth mediums were used. One was the traditional root pack used on all the previous tests. The second was the new and improved root pack, with slow release fertilizer. The hypothesis was that the slow release would help reduce salt intake.

Science is sometimes best when things go wrong.

Mizuna Lettuce
Mizuna Lettuce On ISS
Image Credit: NASA

For some reason, the sensor controlling the watering in the first (traditional) module failed. This resulted in “over-watering” the plants. The results were surprising, but microgravity has held many surprises for scientists. First, the seeds that got “too much” water sprouted quicker and developed leaves twice as fast as the second (improved) module. The second surprise was that the plants grown in the slow release fertilizer in the second module had more salt accumulation than the plants in the first module.

The results suggest that plants in space need a larger volume of water and a faster rate of fertilizer than they do under normal gravity. Shane Topham, an engineer with Space Dynamics Laboratory at Utah State University in Logan, said that “the conservative water level we have been using for all our previous experiments may be below optimal for plant growth in microgravity”.

Overall, the garden experiments have four objectives:

  • Can the crops grown in space be consumed safely
  • What microorganisms grow on the plants, and how do you prevent or minimize microorganisms in the modules prior to launch
  • How do you clean and sanitize the crops after they are harvested
  • What conditions optimize the production of crops in microgravity

One additional objective of the experiments is to measure the non-nutritional benefits (stress relief, etc.) that crew members experience working with plants in space. Growing and tending to the crops provides comfort and relaxation to the crew. On a long voyage, this activity may contribute to the success of the mission.

Lada Module
A view of the Russian BIO-5 Rasteniya-2/Lada-2 (Plants-2)
plant growth experiment located in the Zvezda Service Module
on the International Space Station (ISS).
Image Credit: NASA

A close up view of sprouts on the Russian Lada-2 experiment.
Image Credit: NASA

A view of peas growing in the Russian Lada-2 plant growth experiment.
Image Credit: NASA

A close up view of a bloom on the Russian Lada-2 plant growth experiment.
Image Credit: NASA

NSS Competitions for 2010 -2011


For all of you space enthusiasts out there, listen to this podcast by National Space Society member Lynne Zielinski as she discusses contests for students. Lynne teaches at Glenbrook North High School in Northbrook Illinois, and the podcast provides details on competitions sponsored by the National Space Society.

1. NASA/NSS Space Settlement Student Design Contest (for grades 6-12)

NASA Ames Research Center in conjunction with the National Space Society sponsors an annual space settlement design contest for 6-12th grade students. Each spring students send their designs for homes in space for judging by NASA engineers and scientists. The contest has inspired thousands of students and helped hundreds of teachers bring the excitement of space settlement to the youth of America and the world.

2. International Space Settlement Design Competition (for high school)

This contest puts high school students in the shoes of aerospace industry engineers designing a city in space that will be a home for over 10,000 people. Student engineers demonstrate creativity, technical competence, management skills, space environment knowledge, teamwork, and presentation techniques to conquer the problems inherent in siting and designing a Space Settlement (aka Space Colony).

3. Pete Conrad Spirit of Innovation Awards (for high school)

The Spirit of Innovation Awards program challenges teams of high school students to create innovative products using science, technology, and entrepreneurship to solve 21st century, real-world problems. Eligible students may compete on teams in any of three Challenge Categories.

4. Jim Baen Memorial Writing Contest (any age)

Since its early days, science fiction has played a unique role in human civilization. It removes the limits of what “is” and shows us a boundless vista of what “might be.” Its fearless heroes, spectacular technologies and wondrous futures have inspired many people to make science, technology and space flight a real part of their lives and in doing so, have often transformed these fictions into reality. The National Space Society and Baen Books applaud the role that science fiction plays in advancing real science and have teamed up to sponsor this short fiction contest in memory of Jim Baen.

Spaceport America Runway Dedication

White Knight Two flyover of Spaceport America Terminal carrying SpaceShipTwo
Image Credit: Barbara David

The two mile runway at Spaceport America in New Mexico was dedicated Friday, 22 October 2010. One of the highlights of the celebration was the flyover and landing of Virgin Galactic‘s White Knight Two carrying the rocket plane Space Ship Two, named Enterprise by Virgin Galactic.

Governor Bill Richardson of New Mexico, for whom the runway (spaceway) was officially named during the ceremony, commented that:

“We are celebrating the world’s first spaceway at the world’s first purpose-built, commercial spaceport. New Mexico is not only helping to launch the commercial spaceflight industry, but we are launching new jobs and opportunities for the people of southern New Mexico. Today marks a significant milestone on our historic and exciting journey.”

Sir Richard Branson and approximately 30 of more than 380 Virgin Galactic future astronauts attended the event. Two of the future passengers in attendance were Sonja Rohde from Germany and Perveen Crawford of Hong Kong. Both have already paid the full $200,000 price for their flight into space. “It’s like Christmas, you want to go, you can’t wait. It was always a childhood dream to go to space,” Rohde said. Crawford noted that “It’s a bargain compared to the Russians,” referring to the roughly $35 million past space tourists have paid to ride aboard the Soyuz to the International Space Station.

Approach to Spaceport America
White Knight Two carrying Space Ship Two on Approach to Spaceport America
Image Credit: Virgin Galactic

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

The Wilkinson Microwave Anisotropy Probe

Completed Microwave Map of the Universe
Image Credit: NASA

Scientists announced this week that the mission of the Wilkinson Microwave Anisotropy Probe (WMAP) has been completed. The last set of observations were downloaded on 20 August 2010, and researchers are compiling the final results. The satellite was placed in a permanent parking orbit around the sun on 8 September 2010.

WMAP was launched on 30 June 2001 and placed into an orbit around SEL-2, the second Sun-Earth Lagrange point. SEL-2 lies 1,500,000 kilometers beyond the Earth on a line from the Sun to the Earth. WMAP was the first spacecraft to occupy this location. SEL-2 is extremely cold, shaded from the Sun’s activity by the Earth’s shadow and ideal as an astronomical location in space. In 2009, the Herschel Space Observatory and Planck space observatory took up residence at SEL-2. They will be joined in 2014 or 2015 by the James Webb Space Telescope.

First detected in 1964, the cosmic microwave background (CMB) radiation (television “snow” – before cable), is the remnants of the extremely hot radiation from the big-bang, now cooled to almost absolute zero after 13.73 billions years of the expansion of the universe. It is a pattern frozen in place when the cosmos was only 380,000 years old.

WMAP COBE was the successor to NASA’s Cosmic Background Explorer (COBE), which was launched on 18 November 1989 and produced the first map of the microwave radiation. Note the great increase in resolution between the COBE map at the right, and the WMAP result above.

The Planck observatory is currently making high resolution measurements of both the total intensity and polarization of the primordial CMB anisotropies that were first observed by COBE and WMAP.

The observations made by WMAP are the most accurate to date and have allowed scientists to rule out several “inflation” models about what happened in the first trillionths of a second during the birth of the cosmos, while supplying support for several other models:

  • The age of the universe is 13.73 billion years old to within 1% (0.12 billion years)
  • Ordinary matter (atoms) makes up only 4.6% of the universe (to within 0.1%)
  • Dark matter (not made up of atoms) makes up 23.3% (to within 1.3%)
  • Dark energy makes up 72.1% of the universe (to within 1.5%)

Dark energy is the force driving the galaxies in the universe apart at an ever increasing rate. At some point in the future, inhabitants of the Milky Way will not be able to see any other objects in the sky. These entities will conclude that they are at the center of the universe, and will have no information about the big bang and the creation of the cosmos as we know it today.

The Astronomy and Astrophysics Decadal Survey – 2012 to 2021

by Dave Fischer

The National Research Council has released Its sixth decadal survey of astronomy and astrophysics. The plan focuses on three science objectives:

  • The exploration of the origins of the universe
  • The search for habitable planets outside our solar system
  • The use of astronomical observations to investigate fundamental physics.

The report addresses large, medium, and small activities in these fields. It surveys the existing facilities and the new facilities that would be needed, both ground based and space based. It looks at the known science objectives and where new discoveries might be made. And it looks at the promise of the proposals and the risks associated with each.

The large scale space-based projects are:

  • 1. Wide Field InfraRed Survey Telescope (WFIRST)
  • 2. Explorer Program Augmentation
  • 3. Laser Interferometer Space Antenna (LISA)
  • 4. International X-ray Observatory (IXO)

WFIRST, the near infrared wide-field telescope, is intended to explore Dark Energy and Exoplanet statistics as well as support guest survey investigations.

The Explorer Program is ongoing and funds rapid, targeted projects that deliver a high science return. Past projects include WMAP, Swift, GALEX and WISE.

LISA will exploit the new field of astronomy using long wavelength gravitational radiation measured by three spacecraft 5 million kilometers apart.

IXO is a large area, high spectral resolution x-ray observatory to explore hottest regions in the universe, including clusters of galaxies, the intergalactic medium, and black hole accretion disks.

The medium scale space-based projects are:

  • 1. New Worlds Technology Development Program
  • 2. Inflation Technology Development Program

The New Worlds technology development program is a research program to obtain preliminary observations in order to study nearby habitable planets. Included is technology development in order to make an informed decision in the second half of this decade on a flagship mission.

The Inflation Technology development program will use ground based microwave background telescopes to examine “B-mode polarization.” This is a sensitive signature of processes thought to have occurred during the earliest moments of the universe. If a signal is seen, then a space-based mission with at least ten times greater sensitivity is warranted and associated technology development would be needed.

There are four large scale ground-based projects recommended, and prioritized as follows:

  • 1. Large Synoptic Survey Telescope (LSST)
  • 2. Mid-Scale Innovations Program
  • 3. Giant Segmented Mirror Telescope (GSMT)
  • 4. Atmospheric Cerenkov Telescope Array (ACTA)

The LSST project would address research such as dark energy using gravitational lensing, dark matter, Near-Earth Kuiper-belt objects, the Solar neighborhood, and transient phenomena such as gamma-ray bursts, variable stars, and supernova.

The mid-scale program would fund annual proposals to compete for funding, of which around 7 proposals would be chosen during the decade.

The Giant Segmented Mirror Telescope project suggests that NSF chose one of the two current 30 meter telescope projects (The Giant Magellan Telescope in Chile or the Thirty Meter Telescope in Hawaii) and invest in a quarter share in order to provide access for the entire US community.

The report proposes that the team responsible for the proposed US Advanced Gamma-ray Imaging System (AGIS) collaborate as a minor partner with the European Cherenkov Telescope Array (CTA).

There is one medium scale ground-based program that was recommended by the NRC Decadal Survey:

  • 1. Cerro Chajnantor Atacama Telescope (CCAT)

This 25 meter wide-field sub-millimeter telescope would work in conjunction with the Atacama Large Millimeter Array (ALMA) in Chile.

The small scale investment recommendations are:

  • Target work-force development (TSIP, Sub-orbital, AAG, ATP)
  • Address changing role of computation and theory (TCN)
  • Support current/upcoming facilities (Gemini, Lab Astro, TCN)
  • Develop technology for the future (NSF ATI, NASA Tech. Dev.)

Other documentation:

NASA press release

Preliminary Report

NRC committee reports.

Town Hall Slides (pdf).

JWST – The James Webb Space Telescope

by Dave Fischer

James Webb Space Telescope
James Webb Space Telescope – Deployed
Credit: NASA Video

The James Webb Space Telescope (JWST) is an infrared observatory, and a partial successor to the Hubble Space Telescope. JWST does not view visible light because light from the earliest universe has shifted toward the infrared (red shift).

Infrared sensitivity is required in order to see further back in time toward the beginning of the universe than either Hubble or ground based observatories.The James Webb Space Telescope is a joint venture between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA). In all, fifteen countries are making contributions to JWST.

The are four main components to the scientific mission:

  • Search for the first stars and galaxies that formed after the Big Bang
  • Study galaxies and their formation and evolution
  • Understand the formation of stars and planetary systems
  • Study the origins of life on planetary systems

JWST is scheduled for launch in 2014 aboard an Ariane 5 rocket. It will take up residence at the Sun-Earth Lagrange point 2 (SEL-2). SEL-2 is 1,500,000 km beyond the Earth from the Sun (the Earth-Moon L2 is only 61,500 km beyond the Moon). The location was chosen in order to be able to shield the telescope from the infrared radiation of the Sun and the Earth.

Currently, SEL-2 is occupied by the Wilkinson Microwave Anisotropy Probe (WMAP), which was launched 30 June 2001, and the Herschel and Planck observatories, which were launched together on an Ariane 5 on 14 May 2009.

The image at left is a cutaway diagram the the Ariane 5 rocket, illustrating how the JWST will fold up inside the payload fairing. With the large screen behind it, the JWST will be about 21 m in width. It will stand about three stories high. The main telescope mirror, which measures 6.5 m in diameter, is too large to launch in one piece. Instead, it consists of 17 individual mirror segments mounted on a frame which will be folded inside the fairing of the Ariane 5 at launch.

Once it arrives at SEL-2, it will unfold, as this animation shows.

There are four instruments in the Integrated Science Instrument Module designed to conduct the investigations on board the James Webb Space Telescope:

Cutaway: JWST inside Ariane 5
Image Credit: European Space Agency

Four Instruments
Image Credit: NASA

  • Mid-Infrared Instrument, or MIRI – provided by the European Consortium with the European Space Agency (ESA), and by the NASA Jet Propulsion Laboratory (JPL)
  • Near-Infrared Camera, or NIRCam – provided by the University of Arizona
  • Near-Infrared Spectrograph, or NIRSpec – provided by ESA, with components provided by NASA/GSFC.
  • Fine Guidance Sensor, or FGS – provided by the Canadian Space Agency. The FGS contains a dedicated Guider and a Tunable Filter Camera.

The image below shows the locations of the four instruments in the Integrated Science Instrument Module (ISIM). Below, the image shows the location of the instrument package within the JWST.

Image Credit: NASA

The Mid-Infrared Instrument (MIRI) is an imager/spectrograph that covers the wavelength range of 5 to 27 micrometers. The camera provides wide-field broadband imagery, and the spectrograph module provides medium-resolution spectroscopy over a smaller field of view compared to the imager. The nominal operating temperature for the MIRI is 7K. Additional information can be found at the MIRI website, Space Telescope Science Institute.

The Near Infrared Camera (NIRCam) is an imager with a large field of view and high angular resolution. The NIRCam covers a wavelength range of 0.6 to 5 micrometers. More on NIRCam.

The Near Infrared Spectrograph (NIRSpec) measures the simultaneous spectra of more than 100 objects in a 9-square-arcminute field of view. This instrument provides medium-resolution spectroscopy over a wavelength range of 1 to 5 micrometers and lower-resolution spectroscopy from 0.6 to 5 micrometers. See the Space Telescope Science Institute information on NIRSpec.

The Fine Guidance Sensor (FGS) sensor is used for both “guide star” acquisition and fine pointing. See information from the Space Telescope Science Institute about NIRSpec.

See also:

The Wikipedia article on JWST.
NASA home page for JWST.
ESA home page for JWST.
CSA home page for JWST.
Make your own Paper Model of the JWST.
YouTube and JWST.

Let us know what you think. What do you want to know about? Post a comment.

Desert RATS

by Dave Fischer

If you want humanity to explore the Solar System, you have to test the systems you plan to use for moving around and living. And where is there a readily available harsh environment for such testing? Arizona. In the Summer it is hot and dry. In the Winter it is cold and dry (or wet, depending on the state of the Arctic storm systems).

Currently underway (31 August through 15 September) is the 13th iteration of the Desert RATS program. You can follow their exploits on the RATS’ Blog.

RATS site in Northern Arizona
Image Credit: NASA

NASA Athlete Vehicle
(All-Terrain Hex-Legged
Extra-Terrestrial Explorer)
Image Credit: NASA

Space Exploration Vehicle
Image Credit: NASA / Regan Geeseman

NASA’s Research and Technology Studies (RATS) program is designed to gather engineers, astronauts and scientists and test technology. This year, the major objectives include:

  • Space Exploration Vehicles (pdf) – a pair of rovers that astronauts will live in for 7 days at a time
  • Habitat Demonstration Unit (interactive pdf)/Pressurized Excursion Module – a simulated habitat where the rovers can dock to allow the crew room to perform experiments or deal with medical issues
  • Tri-ATHLETEs, or –Terrain Hex-Legged Extra-Terrestrial Explorer – two heavy-lift rover platforms that allow the habitat, or other large items, to go where the action is
  • Portable communications terminals
  • Centaur 2 – a possible four-wheeled transportation method for NASA Robonaut 2
  • Portable Utility Pallets, or PUPs for short – mobile charging stations for equipment
  • A suite of new geology sample collection tools, including a self-contained GeoLab glove box (pdf) for conducting in-field analysis of various collected rock samples.

During this mission, there will be four crew members living in the two rovers. Their traverse routes will include driving up and down steep slopes and over rough terrain at various speeds. The crew will also demonstrate docking and undocking with the PUPs and the habitat. Other objectives for the rovers include demonstrating the differences in productivity for crew members and their ground support that come with different communication methods, and evaluating different operational concepts for the trips the rovers make.

Let us know what you think. What do you want to know about? Post a comment.


by Dave Fischer

Commercial Reusable Suborbital Research Program

NASA has awarded $475,000 as part of its program to development recoverable launch vehicles to be used for small payloads going to “near-space,” the region of Earth’s atmosphere between 65,000 and 350,000 feet. The awards were made under the CRuSR program (Commercial Reusable Suborbital Research Program). NASA’s press release states:

The CRuSR program fosters the development of commercial reusable transportation to near space. The overall goal of the program is regular, frequent and predictable access to near-space at a reasonable cost with easy recovery of intact payloads.

The awards were made to Armadillo Aerospace, home to the Super-Mod vehicle, and Masten Space Systems, home to the Xaero vehicle.

Armadillo will fly three missions from Spaceport America in New Mexico. Two are schedule for an altitude of nine miles each, and the third is scheduled for 25 miles (132,000 feet – 40,200 meters).

Masten will fly four missions this winter from the Mojave Spaceport in California. Two of the flights are slated for three miles and two are slated for 18 miles (95,000 feet – 29,000 meters).

Image Credit: Armadillo Aerospace
Image Credit: Masten Space Systems

Let us know what you think. What do you want to know about? Post a comment.