Space
Challenges for electronic circuits in space applications
Chris Leonard, Analog Devices, Inc. Talks about the challenging requirements for components in space applications
T
o set the stage for this discussion let me propose this scenario: imagine yourself as an astronaut sitting in the
crew module of the NASA Orion spacecraft. You are stepping through your final equipment checklist for a voyage to Mars while sitting on top of a rocket, anticipating the final countdown to ignition of the largest rocket ever designed—the NASA Space Launch System. You are sitting 384 feet in the air on a massive 130 metric ton configuration, the most capable and powerful launch vehicle in history. When you hear those famous words “gentlemen, we have ignition”, you will have 9.2 million pounds of thrust propelling you into outer space. The Orion spacecraft is being designed to take humans to Mars and into deep space where the temperature can approach over 2000°C, the radiation is deadly, and you will be travelling at speeds up to 20,000 mph. High reliability and devices with space heritage are key factors in the selection of components for space level applications. NASA generally specifies Level 1, qualified manufacturer list Class V (QMLV) devices, and they will always ask if there is a higher quality level available. Knowing the extensive selection process NASA uses for identifying electronic components for
space flight applications, one should be confident sitting on top of that rocket.
The harsh environmental conditions of a spacecraft and the hazards posed to the electronics The first hurdle for space electronics to overcome is the extreme noise and vibration imposed by the launch vehicle. The demands placed on a rocket and its payload during launch are severe. When a satellite separates from the rocket in space, large shocks occur in the satellite’s body structure. Pyroshock is the response of the structure to high frequency, high magnitude stress waves that propagate throughout the structure as a result of an explosive charge, like the ones used in a satellite ejection or the separation of two stages of a multistage rocket. Pyroshock exposure can damage circuit boards, short electrical components, or cause all sorts of other issues.
Outgassing is another major concern. Plastics, glues, and adhesives can and do outgas. Vapour coming off of plastic devices can deposit material on optical devices, thereby degrading their performance. Using ceramic rather than plastic components eliminates this problem in electronics. Outgassing of volatile silicones in low Earth orbit (LEO) causes a
cloud of contaminants around the spacecraft. Contamination from outgassing, venting, leaks, and thruster firing can degrade and modify the external surfaces of the spacecraft.
So how do you dissipate the heat generated by the electronics? The accuracy and life expectancy of electronic devices can be degraded by sustained high temperatures. There are three ways of transferring heat: convective, diffusive, and radiative. In the vacuum of space there is no thermal convection or conduction taking place. Radiative heat transfer is the primary method of transferring heat in a vacuum, so satellites are cooled by radiating heat out into space. Finally, the space radiation environment can have damaging effects on spacecraft electronics. There are large variations in the levels of and types of radiation a spacecraft may encounter. Each space programme has to be evaluated in terms of reliability, radiation tolerance, environmental stresses, the launch date, and the expected life cycle of the mission.
Sources of ionising radiation in interplanetary space (Image: NASA) 40 October 2018 Components in Electronics
The basic elements of a spacecraft are divided into two sections: the platform or bus and the payload. The platform consists of the five basic subsystems that support the payload: the structural subsystem, the telemetry subsystem, tracking and command subsystems, the electric power and distribution subsystem, the thermal control subsystem, and the attitude and velocity control subsystem. The structural subsystem is the mechanical structure and provides stiffness to withstand stress and vibration. It also provides shielding from radiation for the electronic devices. The telemetry, tracking, and command subsystems include receivers, transmitters, antennas, sensors for temperature, current, voltage, and tank pressure. It also provides the status of various spacecraft subsystems. The electric power and distribution subsystems convert solar into electrical power and charge the spacecraft batteries. The thermal control subsystem helps to protect electronic equipment from extreme temperatures. And finally, the attitude and velocity control subsystem is the orbit control system that consists of sensors to measure vehicle orientation and actuators (reaction wheels, thrusters), and to apply the torques and forces needed to orient the vehicle in the correct orbital position. Typical components of the attitude and control system include sun and Earth sensors, star sensors, momentum wheels,
inertial measurement units (IMUs), and the electronics required to process the signals and control the satellites position.
Analog Devices’ efforts in support of space level applications Analog Devices has been supporting the aerospace and defence markets for over 40 years with high reliability devices. Today’s focus is on the space market. The integration of Analog Devices and Hittite Microwave a few years ago now allows us to cover the DC to 110 GHz spectrum. ADI solutions range from navigation, radar, communication systems below 6 GHz, satellite communications, electronic warfare, radar systems in the microwave spectrum, radar systems, and satellite imaging in the millimetre wave spectrum. The space products group leverages Analog Devices’ portfolio of devices in the support of the space industry. We have proprietary silicon on insulator (SOI) processes that provide radiation tolerance for space level applications. In some cases we modify core silicon to enhance the radiation tolerance of devices. We also have the ability to port designs over to radiation hardened SOI processes. We integrate the die into hermetic, ceramic packages and characterise the device over the extended military temperature range. We target the development and release of fully qualified, Class S QMLV products using the defence logistics agency (DLA) MIL-PRF 38535 system for monolithic devices, and MIL-PRF 38534 for Class K hybrid and multichip modules. For radiation inspection we currently offer high dose rate (HDR) and low dose rate (LDR) tested models and for new product releases we offer single event effects test data. We offer enhanced products (EPs), plastic encapsulated devices designed to meet mission critical requirements, and high reliability application requirements. With customer input, we are initiating a new device product category for space applications that we have defined as enhanced products plus (EP+) devices. Our customers are requiring improvements in size, weight, power, higher performance, wider bandwidths, increased operational frequencies, payload flexibility, and optimised reliability. Spacecraft designers are being pressed to use commercial devices in order to meet high levels of performance in increasingly smaller, lower power, and lower cost spacecraft.
www.analog.com
www.cieonline.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
