Power Systems
Cubesats can be powered by solar energy [1], [2]. According to the equations for Radiation pressure, the amount of Solar radiation received is inversely proportional to the distance from the source [3].
Since Jupiter is approximately 5.2 times further away from the Sun than Earth is, Jupiter receives approximately 3.698% of the total power. To help compensate for the lack of power, the internal essential hardware, that a 1U or 10cm x 10cm x 10cm cubesat has, should be encased in a bigger case with more Solar surface area and enough room for other power sources [4]-[7]. The size of the cubesat case will be determined by two factors:
The power source for the Mother Ship would be the same as the one used in the Juno mission, because the Juno mission would have the most advanced solar panels available and design work would be minimized by using a previous designs as a template. The cubesats will also use the same type of solar panels. The Juno spacecraft has three solar arrays [9], [10]. Two arrays have dimensions of 2.9 meters wide and 8.9 meters long [9]. The third array has dimensions 2.091 meters wide and 8.9 meters long [9]. The total solar panel area is calculated to be 70.22 meters squared. The Juno solar array is expected to generate at least 420 watts [9]. The calculated efficiency of the solar panels is approximately 5.980 Watts/meters squared.
By using the exact same designs, the Mother Ship can use that 420 watts for heating, computing, and communications [9]. Since there would be no measurement instruments on the Mother Ship, not all power would be used once all the cubesats are dispensed. So unlike the Juno mission, the Mother Ship would not need the most solar energy efficient space path [10]. In addition, since the Mother Ship would not have all the instruments the Juno mission has [9] and replaces it with cubesats, a dispenser system and other necessary new components, the amount of power required will be heavier at the beginning of the Jupiter Orbit, and less after dispensing. This works well since the solar panels would deteriorate in quality over time [10].
The 12U cubesats will have a maximum surface area of 0.366m x 0.226m, which equals approximately 0.0827 meters squared [5]. The maximum expected power generated is 0.494 Watts. However, by adapting information from Arnold [1] who uses Schaffner’s [6] data, the 1U cubesat, needs at least 377 mW at all times. NASA [11] stated that the Jupiter magnetic fields are similar to Earth magnetic fields. Then three (7cm length x 0.9 cm diameter) 200mW magnetorquer will be used to maintain the altitude in the x, y, and z axi [12]. Since the magnetic field of Jupiter is approximately 20 times of that of Earth's magnetic field [13], the magnetorquer will have more force to maintain the altitude. In the current situation, the communicating with the Mother Ship takes 2W, increasing the power budget to requiring 2820 mW. Solar energy is not enough.
Cubesats can be powered by solar energy [1], [2]. According to the equations for Radiation pressure, the amount of Solar radiation received is inversely proportional to the distance from the source [3].
Since Jupiter is approximately 5.2 times further away from the Sun than Earth is, Jupiter receives approximately 3.698% of the total power. To help compensate for the lack of power, the internal essential hardware, that a 1U or 10cm x 10cm x 10cm cubesat has, should be encased in a bigger case with more Solar surface area and enough room for other power sources [4]-[7]. The size of the cubesat case will be determined by two factors:
- The carrying capacity of the Mother Ship, a larger Satellite that is based on the Juno spacecraft.
- The size of the alternative power sources.
The power source for the Mother Ship would be the same as the one used in the Juno mission, because the Juno mission would have the most advanced solar panels available and design work would be minimized by using a previous designs as a template. The cubesats will also use the same type of solar panels. The Juno spacecraft has three solar arrays [9], [10]. Two arrays have dimensions of 2.9 meters wide and 8.9 meters long [9]. The third array has dimensions 2.091 meters wide and 8.9 meters long [9]. The total solar panel area is calculated to be 70.22 meters squared. The Juno solar array is expected to generate at least 420 watts [9]. The calculated efficiency of the solar panels is approximately 5.980 Watts/meters squared.
By using the exact same designs, the Mother Ship can use that 420 watts for heating, computing, and communications [9]. Since there would be no measurement instruments on the Mother Ship, not all power would be used once all the cubesats are dispensed. So unlike the Juno mission, the Mother Ship would not need the most solar energy efficient space path [10]. In addition, since the Mother Ship would not have all the instruments the Juno mission has [9] and replaces it with cubesats, a dispenser system and other necessary new components, the amount of power required will be heavier at the beginning of the Jupiter Orbit, and less after dispensing. This works well since the solar panels would deteriorate in quality over time [10].
The 12U cubesats will have a maximum surface area of 0.366m x 0.226m, which equals approximately 0.0827 meters squared [5]. The maximum expected power generated is 0.494 Watts. However, by adapting information from Arnold [1] who uses Schaffner’s [6] data, the 1U cubesat, needs at least 377 mW at all times. NASA [11] stated that the Jupiter magnetic fields are similar to Earth magnetic fields. Then three (7cm length x 0.9 cm diameter) 200mW magnetorquer will be used to maintain the altitude in the x, y, and z axi [12]. Since the magnetic field of Jupiter is approximately 20 times of that of Earth's magnetic field [13], the magnetorquer will have more force to maintain the altitude. In the current situation, the communicating with the Mother Ship takes 2W, increasing the power budget to requiring 2820 mW. Solar energy is not enough.
Table 1. CP1 power budget adapted for current project with redundancy [1],[6],[14].
NASA has used Radioisotope Thermoelectric Generators to power previous missions like the Galileo mission [15]. Adding in a Radioisotope Thermoelectric Generators (RTG), will help with the power supply [15], [16]. Since there is no previous NASA based cubesat that used a RTG, it is necessary to create a new power source for this mission [15]. By using Thermocouples and a heat source, electric power can be generated [15]. Due to the size limitations of a 12U cubesat, using a 4”x4”x2” or (10.16cm x 10.16cm x 5.08cm) General Purpose Heat Source module, or GPHS would allow the cubesat to run, even without solar energy, [5], [16]. The Galileo mission also used General Purpose Heat Source (GPHS) modules, but as heat sources not as power source [15]. The NASA webpage states that the GPHS begins with 250 Watts [16], by using a 6% efficient thermocouple, the peak power is 15 Watts [15]. In order to account for the inevitable power loss, the power budget will assume 200 Watts of power instead. By engineering together a 6% efficient thermocouple, a 200 Watt GPHS, and protective casing, a 12 Watt Nuclear power supply is created [15]. The radioisotope generators are known for lasting for years and even decades, and almost never fail [16]. 12 Watts is so big that solar power and ion batteries are not necessary [1]. In order to release excess power to not damage the rest of the cubesat, an adaptable power dissipator circuitry will be made to absorb extra energy and convert it to heat [1]. The excess energy is not detrimental to the system because some heat is necessary to maintain the electronics [17].
Table 2. Power Safety System on the Cubesat [1],[6]
Table 3. Power Budget for the Mother Ship [1],[6],[9]
Power usage for the Mother Ship is set up so that approximately for every 4 seconds in the Sun, 1 second of battery power is stored. There will be more batteries than the Juno mission because many power consuming electronics will be removed, and replace with enough batteries that will allow the orbit to not use solar power for 60 minutes [9].
Inside the Cubesat
The cubesat will have 12 boxes of space: 6 boxes per layer on 2 layers [5]. Figure 1 shows the components of the cubesat in a 3x2 frame. Figure 2 shows the components of the remaining half of the cubesat.
Inside the Cubesat
The cubesat will have 12 boxes of space: 6 boxes per layer on 2 layers [5]. Figure 1 shows the components of the cubesat in a 3x2 frame. Figure 2 shows the components of the remaining half of the cubesat.
References:
[1] Arnold, S.S. et al. "Energy budgeting for CubeSats with an integrated FPGA," Aerospace Conference, 2012 IEEE , vol., no., pp.1,14, 3-10 March 2012 doi: 10.1109/AERO.2012.6187240
[2] J. Lee et al. "Design and Management of Satellite Power Systems," Real-Time Systems Symposium (RTSS), 2013 IEEE 34th , vol., no., pp.97,106, 3-6 Dec. 2013 doi: 10.1109/RTSS.2013.18
[3] Wikipedia. (2014, Mar. 12). Radiation pressure [Online]. Available: http://en.wikipedia.org/wiki/Radiation_pressure
[4] Clyde Space. (2014). Some useful information about CubeSats [Online]. Available: http://www.clyde-space.com/cubesat/som_useful_info_about_cubesats
[5] Spaceflight Inc. (2014). Pricing [Online]. Available: http://spaceflightservices.com/pricing-plans/
[6] J. Schaffner, “The Electronic System Design, Analysis, Integration, and Construction of the Cal Poly State University CP1 CubeSat” in 16th AIAA/USU on Small Satellites Conference, Logan, UT, October 2002, pp. 1-2
[7] V. Kane. (2013, Oct. 24). The Potential of CubeSats. [Online]. Available: http://www.planetary.org/blogs/guest-blogs/van-kane/20131023-the-potential-of-cubesats.html
[8] Clyde Space. (2014). 6U CubeSat SIDE Solar Panel w/MTQ [Online]. Available: http://www.clyde-space.com/cubesat_shop/solar_panels/12u_solar_panels
[9] P. Blau. (2014). Juno Spacecraft Information [Online]. Available: http://www.spaceflight101.com/juno-spacecraft-information.html
[10] N. T. Redd. (2011, Aug. 4). NASA's Juno Mission to Jupiter to Be Farthest Solar-Powered Trip [Online]. Available: http://www.space.com/12541-juno-jupiter-mission-solar-panels-power.html
[11] NASA. (2011, Aug. 1). Juno to Show Jupiter's Magnetic Field in High-Def [Online Video]. Available: http://www.nasa.gov/mission_pages/juno/news/juno20110801.html#.U89CmruoIjg
[12] Innovative Solutions In Space. (2014). CubeSat Magnetorquer Rod [Online]. Available: http://www.cubesatshop.com/index.php?page=shop.product_details&product_id=75&flypage=flypage.tpl&pop=0&option=com_virtuemart&Itemid=65&vmcchk=1&Itemid=65
[13] H. R. Smith/NASA Educational Technology Services. (2011, Aug. 10). What Is Jupiter? [Online]. Available: http://www.nasa.gov/audience/forstudents/5-8/features/what-is-jupiter-58.html#.U89BULuoIjg
[14] T. Pratt et al., “Satellites,” in Satellite Communication, 2nd ed. Danvers, MA: John Wiley & Sons, Inc., 2003, ch.3, sec. 7, pp.87-89.
[15] NASA. (2013, Sep. 4). Radioisotope Thermoelectric Generator (RTG) [Online]. Available: https://solarsystem.nasa.gov/rps/rtg.cfm
[16] NASA. (2014, Feb 4). RPS Technology [Online]. Available: https://solarsystem.nasa.gov/rps/types.cfm
[17] NASA. (2013, July 13). Radioisotope Heater Unit (RHU) [Online]. Available: https://solarsystem.nasa.gov/rps/rhu.cfm
[1] Arnold, S.S. et al. "Energy budgeting for CubeSats with an integrated FPGA," Aerospace Conference, 2012 IEEE , vol., no., pp.1,14, 3-10 March 2012 doi: 10.1109/AERO.2012.6187240
[2] J. Lee et al. "Design and Management of Satellite Power Systems," Real-Time Systems Symposium (RTSS), 2013 IEEE 34th , vol., no., pp.97,106, 3-6 Dec. 2013 doi: 10.1109/RTSS.2013.18
[3] Wikipedia. (2014, Mar. 12). Radiation pressure [Online]. Available: http://en.wikipedia.org/wiki/Radiation_pressure
[4] Clyde Space. (2014). Some useful information about CubeSats [Online]. Available: http://www.clyde-space.com/cubesat/som_useful_info_about_cubesats
[5] Spaceflight Inc. (2014). Pricing [Online]. Available: http://spaceflightservices.com/pricing-plans/
[6] J. Schaffner, “The Electronic System Design, Analysis, Integration, and Construction of the Cal Poly State University CP1 CubeSat” in 16th AIAA/USU on Small Satellites Conference, Logan, UT, October 2002, pp. 1-2
[7] V. Kane. (2013, Oct. 24). The Potential of CubeSats. [Online]. Available: http://www.planetary.org/blogs/guest-blogs/van-kane/20131023-the-potential-of-cubesats.html
[8] Clyde Space. (2014). 6U CubeSat SIDE Solar Panel w/MTQ [Online]. Available: http://www.clyde-space.com/cubesat_shop/solar_panels/12u_solar_panels
[9] P. Blau. (2014). Juno Spacecraft Information [Online]. Available: http://www.spaceflight101.com/juno-spacecraft-information.html
[10] N. T. Redd. (2011, Aug. 4). NASA's Juno Mission to Jupiter to Be Farthest Solar-Powered Trip [Online]. Available: http://www.space.com/12541-juno-jupiter-mission-solar-panels-power.html
[11] NASA. (2011, Aug. 1). Juno to Show Jupiter's Magnetic Field in High-Def [Online Video]. Available: http://www.nasa.gov/mission_pages/juno/news/juno20110801.html#.U89CmruoIjg
[12] Innovative Solutions In Space. (2014). CubeSat Magnetorquer Rod [Online]. Available: http://www.cubesatshop.com/index.php?page=shop.product_details&product_id=75&flypage=flypage.tpl&pop=0&option=com_virtuemart&Itemid=65&vmcchk=1&Itemid=65
[13] H. R. Smith/NASA Educational Technology Services. (2011, Aug. 10). What Is Jupiter? [Online]. Available: http://www.nasa.gov/audience/forstudents/5-8/features/what-is-jupiter-58.html#.U89BULuoIjg
[14] T. Pratt et al., “Satellites,” in Satellite Communication, 2nd ed. Danvers, MA: John Wiley & Sons, Inc., 2003, ch.3, sec. 7, pp.87-89.
[15] NASA. (2013, Sep. 4). Radioisotope Thermoelectric Generator (RTG) [Online]. Available: https://solarsystem.nasa.gov/rps/rtg.cfm
[16] NASA. (2014, Feb 4). RPS Technology [Online]. Available: https://solarsystem.nasa.gov/rps/types.cfm
[17] NASA. (2013, July 13). Radioisotope Heater Unit (RHU) [Online]. Available: https://solarsystem.nasa.gov/rps/rhu.cfm