The most recent issue of Science News (18 December 2010) has the following notes from 17 December 1960:
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 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:
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.
* The Falcon 9 rocket performed nearly flawlessly. The roll attitude was solid through the entire flight. The first stage sep was without impingement.
* The Dragon capsule entered orbit 301×288 on a targeted 300km circular.
* The capsule thrusters were tested on maneuvers similar to what is required for ISS docking.
* 4 Cubesats were successfully released into orbit.
* After separation from Dragon, the Falcon 2nd stage was fired again and placed in an orbit with an 11,000km apogee.
* The capsule re-entry burns were spot on.
* All three parachutes deployed perfectly.
* The capsule came down so close to the recovery ship that they have a good photo of it under the parachutes.
* It was being recovered within 35 minutes of the opening of the drogue chute.
* The heat shield barely got warm. We have now been told that this craft has a heat shield that can handle a free return from the Luna or Mars, i.e. it can be used as an interplanetary vehicle.
* Plans are for the next generation to do powered landings on a helipad sized landing pad.
* The volume and capabilities of Dragon meet or exceed those of the not yet ready for test Orion capsule.
* Today’s mission was so stunningly successful that SpaceX wants to move directly to an ISS flight on the next test. NASA is thinking about it
Today, SpaceX became the first commercial company in history to re-enter a spacecraft from low-Earth orbit.
SpaceX launched its Dragon spacecraft into low-Earth orbit atop a Falcon 9 rocket at 10:43 AM EST from the Air Force Station at Cape Canaveral.
The Dragon spacecraft orbited the Earth at speeds greater than 17,000 miles per hour, reentered the Earth’s atmosphere, and landed in the Pacific Ocean shortly after 2:00 PM EST.
This marks the first time a commercial company has successfully recovered a spacecraft reentering from low-Earth orbit. It is a feat performed by only six nations or government agencies: the United States, Russia, China, Japan, India, and the European Space Agency.
It is also the first flight under NASA’s COTS program to develop commercial supply services to the International Space Station. After the Space Shuttle retires, SpaceX will fly at least 12 missions to carry cargo to and from the International Space Station as part of the Commercial Resupply Services contract for NASA. The Falcon 9 rocket and Dragon spacecraft were designed to one day carry astronauts; both the COTS and CRS missions will yield valuable flight experience toward this goal.
View the press kit: http://www.spacex.com/downloads/cots1-20101206.pdf
SunSat Design is an international competition intended to accelerate the design, manufacture, launch and operation of the next-generation satellites that will collect energy in space and deliver it to earth as electricity.
Registration Deadline: January 10, 1011
Design Submission Deadline: April 4, 2011
Winners will be announced at the National Space Society’s International Space Development Conference in Huntsville in May.
This Design Project will generate visualizations to aid in the design, manufacture, launch and operation of the new types of satellites that will collect sun’s rays in space and deliver them to earth as a clean and renewable source of energy. These visualizations will also inform the public debate about the way forward for development and implementation of universal access to space-based solar power.
Winning designs will be high-impact digital art, supported by credible science, engineering and business plans, that best promote media understanding and public acceptance of a path forward in using space satellites to deliver energy on-demand to any and all places on earth.
The SunSat Competition is an initiative of The Online Journal of Space Communication in partnership with The Society of Satellite Professionals International, the National Space Society, and the Ohio University GRID Lab.
For more information and registration, go to http://sunsat.gridlab.ohio.edu.
The Coalition for Space Exploration, of which the National Space Society is a member, has produced another in its series of short public service announcement videos intended to provide some answers to the question “Why spend money on space when we have so many problems here on Earth?”
The new video is called “Think Outside the Circle” and can be viewed on the NSS website by clicking on the image below.
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.
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:
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.