radiation effects and its shielding.pptx

Radiation and its shielding methods

1. RADIATION EFFECTS AND ITS SHIELDING Mr. J. Jensin Joshua M.E.,CEng , ( Ph.D ) Aeronautical Engineer

2. Topics Radiation Space Environment Shielding from Space Environment Inherent Space Shielding Charge Dissipation Coating

3. Radiation Radiation is a form of energy that is emitted in the form of rays, electromagnetic waves, and/or particles . In some cases, radiation can be seen (visible light) or felt (infrared radiation), while other forms—like x-rays and gamma rays—are not visible and can only be observed with special equipment . Space radiation is comprised of atoms in which electrons have been stripped away as the atom accelerated in interstellar space to speeds approaching the speed of light – eventually, only the nucleus of the atom remains. Space radiation is made up of three kinds of radiation: particles trapped in the Earth’s magnetic field; particles shot into space during solar flares (solar particle events ); galactic cosmic rays, which are high-energy protons and heavy ions from outside our solar system. All of these kinds of space radiation represent ionizing radiation.

4. SPACE ENVIRONMENT

5. Van A llen radiation belt

6. Radiation risk

7. Some Case studies related to radiation effects in Spacecraft Apollo 13: In 1970, the Apollo 13 mission suffered an explosion in one of its oxygen tanks , which caused the spacecraft to lose power and oxygen. The crew was exposed to higher levels of radiation than normal during their return trip to Earth due to the lack of protection from the damaged spacecraft. Mir space station: In 1997, the Russian Mir space station suffered a fire in one of its modules. As a result, the station's shielding was damaged, which increased the crew's exposure to radiation . Later in 1998, one of the station's modules was struck by a cargo ship, which caused a leak of toxic propellants and damaged the station's radiation shielding further. Fukushima satellite: In 2011, the Fukushima Daiichi nuclear disaster in Japan released large amounts of radioactive material into the atmosphere. A satellite that was passing over the area at the time was exposed to high levels of radiation, which caused it to malfunction and lose communication with ground control. Mars Exploration Rovers: The Mars Exploration Rovers, Spirit and Opportunity, were launched in 2003 and landed on Mars in 2004. Both rovers experienced higher than expected radiation exposure due to several solar events during their missions. Spirit's mission ended prematurely in 2010 due to a mechanical failure, while Opportunity's mission ended in 2019 due to a dust storm that covered its solar panels.

8. Shielding from Space Environment Both short- and long-term health risks from exposure to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) are potentially limiting factors in the human exploration of deep space. A significant portion of the risk is attributable to the presence of high-energy heavy ions in space, particles that do not exist on the surface of the Earth and which are known to cause biological damage disproportionate to the physical dose they impart. Large uncertainties remain in our knowledge of the biological effects of high-energy heavy ions, particularly at the low dose rates encountered in space . In conventional radiation protection, three principles apply: ( 1) minimize the duration of the exposure; ( 2) maximize the distance from the source ; ( 3) place shielding between personnel and the source whenever possible.

9. Design of Radiation Shield in Spacecraft Define Mission Requirements | Identify Radiation Sources | Select Shielding Materials | Calculate Shielding Thickness | Evaluate Structural Impact | Test and Validate Shielding Design | Implement Shielding Design

10. Shielding from Space Environment - Types Passive shielding: Passive shielding involves the use of materials that are capable of blocking or absorbing radiation , such as lead, tungsten, and polyethylene. These materials are often used in the walls and floors of the spacecraft to provide a natural barrier to radiation . Active shielding: Active shielding involves the use of magnetic or electric fields to deflect charged particles away from the spacecraft. This technique is still in the experimental stage and is not currently used in spacecraft design .

11. Water shielding: Water is a good radiation shield and can be used in spacecraft design to provide protection against radiation. For example, the walls of the ISS are lined with bags of water to provide additional protection for the crew. Biological shielding: Biological shielding involves the use of living cells or organisms to absorb or block radiation. For example, the walls of the Biosphere 2 project, which was designed to create a self-sustaining ecosystem, were made up of soil and plants that absorbed and blocked radiation. Active dosimetry : Active dosimetry involves the use of radiation sensors to monitor radiation levels in the spacecraft and provide real-time information to the crew. This helps to ensure that radiation levels are kept within safe limits.

12. Effects of Radiation Electronic systems: Radiation can damage or disrupt electronic systems in spacecraft, including communications, navigation, and scientific instruments. The high-energy particles in space can cause electrical glitches and can even flip bits in computer memory. Human health: Radiation exposure can also have significant health effects on the crew, including an increased risk of cancer, cataracts, and other radiation-related illnesses. The risk is particularly high for deep space missions, where the crew is exposed to higher levels of radiation from cosmic rays and solar flares. Material degradation: Radiation can also cause degradation of spacecraft materials, leading to reduced performance and reliability of critical systems. Solar panels: Radiation can cause damage to solar panels, which can result in reduced power generation capabilities for the spacecraft.

13. Inherent Space Shielding Inherent mass shielding is a technique used in spacecraft design to protect against the harmful effects of radiation. It involves incorporating materials into the structure of the spacecraft that provide a natural barrier to radiation, rather than relying on additional external shielding. Inherent mass shielding works by selecting materials that have high atomic numbers, which means they have a greater number of protons in their atomic nuclei. These materials, such as lead, tungsten, and tantalum, are more effective at stopping high-energy particles than lighter materials like aluminum and plastics. By incorporating these materials into the structure of the spacecraft, such as the walls and floors, the spacecraft itself can provide a certain level of protection against radiation without the need for additional, external shielding. This can save on weight and reduce the cost of the spacecraft. However, inherent mass shielding has its limitations. It may not provide adequate protection against particularly high-energy particles, such as those produced by solar flares. In these cases, additional external shielding may still be necessary.

14. Space Shielding Examples The International Space Station (ISS) uses inherent mass shielding in its design. The walls of the ISS are made up of several layers of materials, including aluminum and Kevlar, to provide protection against radiation. The Mars Curiosity Rover also uses inherent mass shielding to protect its sensitive instruments and electronics from radiation. The rover is designed with a thick layer of aluminum shielding that is incorporated into the structure of the rover itself. The Hubble Space Telescope also utilizes inherent mass shielding in its design. The telescope is surrounded by a protective shield made up of several layers of materials, including aluminum and mylar . NASA's Orion spacecraft, which is designed for deep space exploration, incorporates inherent mass shielding into its design. The spacecraft's walls are made up of several layers of materials, including aluminum and a high-strength composite material, to provide protection against radiation

15.  Charge Dissipation Coatings  Many NASA spacecraft and satellites operate in radiation environments: geostationary and medium earth orbits, radiation belts in the outer planets, solar wind, and Lagrangian points near the sun . With highly charged particles that penetrate spacecraft, internal electrostatic discharge risks mission assurance. The Jovian environment has radiation levels 7 times greater that Earth's geostationary orbit, which is the NASA Europa Jupiter System Mission environment. In order to reduce the risk of internal electrostatic discharge on sensitive spacecraft electronic components, NASA seeks a conformal conductive coating that dissipates charge on the surface of electronic boards . It is highly desired for the coating to be applied to electronic boards using a standard industry method such as painting or other brush technique in a cleanroom environment.

16.  Charge Dissipation Coatings  (Contd..) The coating must dissipate charge, have low outgassing, and have low water absorption. The coating is highly desired to be optically clear for visual inspection of components. The coating is also highly preferred to be thermoplastic for removal if needed. The minimum maximum service temperature for the coating is 70 deg C. Charge dissipation testing can be done using electron gun, which can be screened using a scanning electron microscope (SEM). At the macroscopic level, the volume resistivity of the conductive coating must be in the range of 1 x 10 e8-e12 ohm cm. The paint or coating must be able to adhesively bond to conventional electronic epoxy and polyimide circuit boards without damaging metal circuits, resistors, capacitors, and semiconductor surfaces. Improved charge dissipation supports the mission assurance of NASA satellites and spacecraft that operate in charging environments.

17. Process Identify components for coating: Determine which components on the spacecraft need to be coated with a charge dissipation coating. These may include electronic components or other sensitive equipment that could be damaged by ESD. Prepare surface for coating: Clean the surface of the component thoroughly to remove any dirt, grease, or other contaminants that could interfere with the coating process. Apply the coating: Apply the charge dissipation coating to the surface of the component. This can be done using a variety of methods, including spray coating, brush coating, or dip coating. The coating is typically made from a conductive material such as carbon or metal particles mixed into a polymer matrix. Verify coating effectiveness: Test the coating to ensure that it is effective at dissipating electrical charges. This may involve measuring the surface resistivity or performing electrostatic discharge tests to simulate real-world conditions. Reapply coating as needed: Charge dissipation coatings can wear off over time or become damaged during handling or operation. It may be necessary to reapply the coating periodically to maintain its effectiveness.

18. Other Techniques to overcome radiation: Active Radiation Shielding: Active radiation shielding involves using a magnetic field generated by electromagnets to deflect charged particles away from the spacecraft. This method is effective against both high-energy cosmic rays and solar particles. Hydrogen Shielding: Hydrogen is an effective shield against radiation due to its high cross-section for interaction with charged particles. By surrounding the spacecraft with a layer of hydrogen, the radiation dose can be significantly reduced. This method is particularly effective against solar particles. Multi-Layer Shielding: Multi-layer shielding involves using several layers of different materials to provide protection against different types of radiation. For example, a spacecraft may have an outer layer of aluminum to protect against cosmic rays, followed by a layer of water to protect against solar particles. Self-Healing Materials: Self-healing materials can repair themselves when damaged by radiation. This is achieved by incorporating materials that can repair radiation-induced defects or using polymers that can re-form chemical bonds after exposure to radiation. Radiation-Hardened Electronics: Radiation-hardened electronics are designed to withstand the effects of radiation. This can be achieved through a variety of methods, including using radiation-resistant materials, shielding sensitive components, and using redundancy in electronic systems.

19. Some common Materials to overcome Radiation Aluminum: Aluminum is a lightweight and commonly used material in spacecraft construction. It is an effective shield against high-energy cosmic rays. Polyethylene: Polyethylene is a plastic material that has a high hydrogen content, which makes it an effective shield against low-energy protons and electrons. Water: Water is also an effective radiation shield due to its high hydrogen content. It is often used as a secondary shield after aluminum or polyethylene to provide additional protection against solar particle events. Lead: Lead is a dense material that is effective at blocking high-energy gamma rays and X-rays. However, it is not commonly used in spacecraft construction due to its weight. Beryllium: Beryllium is a lightweight metal that is effective at blocking X-rays and gamma rays. It is used in some spacecraft components, such as mirrors and X-ray telescopes. Boron: Boron is a material that is effective at absorbing thermal neutrons. It is commonly used in nuclear reactors and some spacecraft designs that use nuclear power sources. Carbon-based materials: Carbon-based materials, such as carbon fiber and graphite, are lightweight and have a high strength-to-weight ratio. They are often used in spacecraft construction and can also provide some radiation shielding.