Payload Concept Proposal. Galileo s Explorers of the Abyss The fotia of Auahituroas, the pagos of Europa, Dawn of life.

Transcription

1 Payload Concept Proposal Galileo s Explorers of the Abyss The fotia of Auahituroas, the pagos of Europa, Dawn of life. Da Vinci Team 2

2 1.0 Introduction Europa is Jupiter s sixth closest moon as well as the sixth-largest moon in the Solar System. Europa was discovered by Galileo Galilei in 1610 and is made mostly of ice and what is theorized to be water under the surface. Team Galileo s Explorers of the Abyss, or Team GEA, will create a payload design that will voyage to Europa to complete a scientific mission. The team s main goal for the mission is to learn as much as possible during the time spent in Europa, centering its attention on the comet that crashed on Europa. The payloads, which will travel to Europa with the UAH orbiter and lander, will investigate the Pwyll crater and the surrounding brown substances. In addition this, the team will also explore the seismic conditions of the planet in order to learn more about the thickness of the ice. There will be two payloads to achieve these goals: an orbiter, known as Komitis; and small landers, known as the Mini Yetis. Komitis will focus on gathering information about Pwyll s composition and the Mini Yetis will focus on learning about the seismic activity on Europa. 2.0 Science Objective and Instrumentation Team GEA s Science Objective is to learn more about the comet that crashed on Europa and gain knowledge of the possibility of life in Europa. Specifically, the team will be gathering information about the composition and temperature of the crater known as Pwyll. The team has decided on this objective because the information gathered by the payloads may provide further support for panspermia: the theory that life is spread through the universe by comets and meteors. If this theory is proved, it may offer more clues about how life began on Earth. Although there are several methods for determining composition, the team has decided to use a hyperspectral imaging camera because of its versatility and ability to gather information from a distance. To gather information about temperature, the team will use thermocouples. As a science enhancement, the team will also take seismic measurements in order to possibly determine the thickness of the ice. Instead of using seismographs, which are large and heavy, the team will use inertial measurement units in their place. Science Objective Learn about Pwyll Learn about Pwyll Learn about the thickness of the ice (Science Enhancement) Table 1. Science Traceability Matrix Measurement Measurement Objective Requirement Find the composition Take images from the of Pwyll orbiter Find the temperature Landers successfully of various areas arrive in Pwyll within Pwyll Use seismic data to learn more about how thick the ice really is Landers successfully arrive in Pwyll, Landers survive for long enough to take measurements Instrument Selected Hyperspectral Imaging Camera Thermocouple Inertial Measurement Unit (IMU) Page - 1

3 Instrument Pika XC - Highperformance Hyperspectral Imaging Camera Omega CO1-T Thermocouple VN-100 SMD Inertial Measurement Unit Mass (kg) Table 2. Instrument Requirements Power Data Lifetime Frequency Duration (W) Rate (Mbps) Self Powered 30 days (720 hr) 1 image 1 hr hr Continuous Continuous hr Continuous Continuous Table 3. Support Equipment Table Component Mass (kg) Power (W) Other Technical Specifications On Board Processor x 94 x 12.4mm Batteries N/A Provides power for Mini Yetis, not required on Komitis Highly Integrated S-Band Transmitter for Pico and Nano Satellite Deployable Antenna System for CubeSats x 46 x 15mm, only on the Mini Yetis, not required on Komitis 98 x 98 x 7mm, only on the Mini Yetis, not required on Komitis 3.0 Payload Design Requirements There are many conditions that team GEA s payload design must survive in order to successfully conduct the mission. First, it must successfully deploy from the UAH spacecraft. It must then be able to autonomously collect data, transmit data, power itself, and protect itself from the environment. If part of the payload does not deploy, it must still be able to gather data independently. Europa s environment is extremely harsh. Temperatures around Pwyll are approximately -160 C with 540 Rem of radiation per day. The atmosphere is exceedingly thin, with only 0.1 µpa of pressure. To create the payload, the team must make sure it can withstand the cold temperature for enough time to receive information and study the comet s impact site. The orbiter section should be able to survive its journey in space. The lander sections must be able to survive the cold weather and impact from landing. The requirements that were given by InSPIRESS are also vital to being able to properly create a payload design. In addition to the aforementioned requirements, the payload must be less than or equal to 44x24x28 cm and 10 kg and part of the payload must deploy, but it mustn't harm the UAH spacecraft. Page - 2

4 4.0 Alternative Concepts Team GEA has a total of five concepts: two orbiter concepts and three lander concepts. The orbiter s mission would be to take hyperspectral images of Pwyll and the lander s mission would be to take seismic and thermal measurements on Pwyll. Both orbiter concepts are similar in that their only scientific instrument is the hyperspectral imaging camera. They would be using this to take images of Pwyll in order to determine the composition of the ice in the crater, including the mysterious brown substance. For the first orbiter concept, the orbiter would achieve its own individual orbit around Pwyll. Once the UAH orbiter is at the same altitude as Pwyll, the orbiter would deploy and achieve an equatorial orbit, unlike the UAH orbiter which has a polar orbit. The second orbiter concept is a simpler version. Instead of achieving its own orbit, it would remain with the UAH orbiter for the entirety of the mission. Once the UAH orbiter passes over Pwyll the payload will take images and conclude its mission. The orbiter payload will be referred to as Komitis. Figure 1. Orbiter Concept Team GEA created three different concepts for the lander payload, known as the Mini Yeti payload. These concepts are known as the Crash Lander, the Air Bag lander, and the Air Canister lander. Each concept will not be alone, but will rather be a fleet of landers to increase odds of success. For the Crash Lander concept, the fleet will be deployed from the UAH lander during the orbit null phase and will freely drop into Pwyll. Each lander will be made with several coats of carbon fiber to withstand the force of impact. Upon deployment they will begin to take thermal and IMU measurements and will continue for the time it takes to land on Europa and for a Europan day cycle. Once that time ends, the battery will run out and the mission will conclude. Figure 2. Crash Lander Concept The Air Bag s mission will begin in a manner similar to the Crash Lander. The fleet will deploy from the UAH lander during the orbit null phase and will fall into Pwyll. All instruments will be activated at this time. Before impact, they will deploy air bags to cushion their impact. After they land, the air bags will detach and they will continue the mission for a Europan day cycle. Figure 3. Air Bag Lander Concept The third design is the Air Canister concept. They will deploy from the UAH lander, as all the rest, and would fall to Pwyll during the orbit null phase. Once they approach Pwyll, an air Page - 3

5 canister located on the bottom of the payload will release air to slow down the payload s descent. The fleet will take measurements for a Europan day cycle. Figure 4. Air Canister Lander Concept 5.0 Decision Analysis In order to pick the two best designs, the team created two independent decision matrices; one for the Mini Yetis and one for Komitis. The matrices have the same Figures of Merit, but the scores are judged differently for the orbiter concepts than for the lander concepts. Designs were carefully considered and scored based off possible scenarios, especially worse case scenarios. Table 4. Orbiter Payload Decision Analysis FOMs Weight Orbiter (Its own Orbit) Orbiter (With UAH) 1, 3, or 9 Raw Score Weighted Score Raw Score Weighted Score Science Objective Likelihood Project Requirement Science Mass Ratio Design Complexity ConOps Complexity Likelihood Mission Success Manufacturability Power Consumed Data Rate/Transmission Data Collected TOTAL The decision analysis for the orbiter payload was created with each score, comparing both concepts. Major concerns for the independent orbiter were extra weight for support equipment and transmission of data, as the hyperspectral imaging camera has a large data rate. In the end, the analysis revealed the orbiter payload that remains with the UAH orbiter to be the most effective concept. Page - 4

6 Table 5. Lander Payload Decision Analysis Weight Crash Lander Air Bag Lander Air Canister FOMs Raw Weighted Raw Weighted Raw Weighted 1, 3, or 9 Score Score Score Score Score Score Science Objective Likelihood Project Requirement Science Mass Ratio Design Complexity ConOps Complexity Likelihood Mission Success Manufacturability Power Consumed Data Rate/Transmission Data Collected TOTAL This decision analysis was scored based on comparisons with the other payload lander concepts. Due to concerns about feasibility for the concept, the Air Canister concept scored the lowest. Although the Air Bag lander had a high score, the team considered that more complex designs are more likely to have complications throughout the mission. The analysis revealed the Crash Lander payload to be the most effective for its mission. 6.0 Engineering Analysis In order to calculate the final weight, amount of power required, and mission time, a certain order of calculations was followed. The calculations were the time over Pwyll, the weight of Komitis, Mini Yeti lifetime, Mini Yeti weight, and g-load upon impact. To find how much time the orbiter would spend over Pwyll, the team began with the speed of Europa s rotation. This was found by dividing the circumference of Europa (9806 km) over the time it takes Europa to rotate (85.22 hr). Europa was determined to rotate at a speed of km/hr. Next, the time to pass Pwyll over the X axis (due to Europa s orbit) was calculated by dividing the diameter of Pwyll (26 km) over the previously calculated speed of Europa s rotation (115.1 km/hr). This time was found to be 0.23 hr, or 13.8 minutes. The next step was to find the orbital velocity, which was found by multiplying the universal gravitational constant (6.67x10-11 ) by the mass of Europa (4.7998x10 22 ), dividing it from the orbiter s distance from Europa s center ( m) and then finding the square root of the result. The orbital velocity of the UAH orbiter was found to be m/s. This led to finding how long it would take for the UAH orbiter to orbit Europa. This was found by dividing the orbital velocity (1.388 km/s) by the circumference of Europa (9806 km) and was found to be seconds or 1.96 hr. With the time required to orbit found, the team calculated how many times they would pass over Pwyll throughout the course of the mission. The mission lasts 30 Earth days, or 8.45 Europa days. By diving the window of opportunity for passing Pwyll over the X axis (0.23 hr) over the time it Page - 5

7 takes to orbit Europa (1.96 hr) per day, the result, 0.117, is the average amount of passes per Europan day. When multiplied by the 8.45 day mission, the team found a total of 1 pass over Pwyll throughout the course of the mission. Because the orbiter is moving at a speed of km/s, it would take s to pass over Pwyll (which has a circumference of 26 km.) In short, Team GEA s orbiter would pass over Pwyll once for seconds over the course of the mission. With the time over Pwyll calculated, the team could then find the total weight and power required for Komitis mission. Because the payload would only pass Pwyll once, it would only be able to take one hyperspectral image of Pwyll. In order to ensure the best results, Komitis will be powered on for an hour as it approaches, is over, and passes Pwyll. The only two electronic instruments onboard are the hyperspectral imaging camera and processor, which take up 2.5 W and 0.4 W of power, respectively. The team multiplied these numbers by 1 for the hour Komitis would be active and then added them for a total of 2.9 W. As Komitis would stay with the UAH orbiter and would receive power from the spacecraft, it would not need its own batteries. Next, the team found the surface area of Komitis. The dimensions of Komitis are 24 x 12 x 8 cm, so it has a surface area of 0.12 m^2. The carbon fiber has a weight 0.3 kg per meter square, so the team multiplied it by the surface area of 0.12 to find a total of kg of carbon fiber. The combined weight of the hyperspectral camera and processor is kg, giving Komitis a total weight of 2.03 kg when the carbon fiber is added. With Komitis weight found, the team then found the Mini Yetis lifetime. First the team found the final velocity upon impact with Europa. The final velocity was found with the equation V f 2 = V i 2 + 2aD. The initial velocity was 0, the rate of acceleration was on Europa, and the distance was 100,000. After solving for the final velocity, the team found a total of m/s. With the final velocity Team GEA could then find how long it would take each Mini Yeti to fall to Europa. This was found by solving for t in the equation V f = V i + at. The team found a total time of s, or 0.11 hr. When added to a day cycle on Europa (85.22 hr), the team determined the Mini Yetis to be active for hr. Once the Mini Yetis lifetime was calculated, the team moved on to find their total weight. In order to find the weight of the batteries on board, the power requirements for all of the instruments on board was found (total of W), multiplied by the total lifetime (85.33 hr) and divided by 400. The batteries were found to weigh kg. For the actual instruments themselves, Team GEA added up their weights ( kg) and multiplied them by two for thermal protection to survive the harsh conditions of Europa for a total of kg. Next, the team found the weight of the carbon fiber coating. Each Mini Yeti is a 6 cm cube with a surface area of m^2. Using the same 0.3 kg weight from Komitis, a layer of carbon fiber was found to weigh kg. In order to ensure the survival of the Mini Yetis, GEA decided to use five layers of carbon fiber for a total of kg. With all of these weights combined, each Mini Yeti was found to weigh a total of kg. Finally, the team found how many Mini Yetis would fit into the payload in terms of weight. Because the weight limit is 10 kg and Komitis weighs 2.03 kg, there was a total of 7.97 kg available for the Mini Yetis. The team divided the weight of each Mini Yeti ( kg) by the 7.97 kg for a total of Team GEA concluded that there would be enough weight for a total of 9 Mini Yetis. The box that contains all of the Mini Yetis prior to deployment will be 28 x 18 x 18 cm large and has a total surface area of 0.26 m^2 and uses a total of kg of carbon fiber, giving all 9 Mini Yetis plus their containing box a weight of kg. This leaves a total of kg leftover. Page - 6

8 Finally, the team calculated the G-load that the Mini Yetis would sustain upon impact with Europa. The first step was to find the penetration into the ground upon impact. This was found with D = SN ( m A ).7 (v 30.5), or D = (2)(.9) ( ).7 ( ) with all of the variables filled in. This yielded a total penetration of 2.37 m. Using this number for d in the equation V f 2 = V i 2 + 2ad, the team solved for a and found it to be m/s^2. GEA then divided this result by 9.81 to find a total G-load of upon impact with Europa, a number well within the limits of the protection provided by carbon fiber. 7.0 Final Design Team GEA s final designs were the version of Komitis that remains with the UAH lander for the entire course of its mission and the Crash Lander version of the Mini Yetis. These designs were chosen based off the results of the decision matrix and were tweaked slightly to be able to better complete the mission. Komitis, the orbiter payload, is 24 x 12 x 8 cm in size and would not deploy for the course of the mission. While inside the UAH orbiter, it would take a hyperspectral image of Pwyll. Since it would be attached to the UAH orbiter, Komitis would not require batteries, a transmitter, nor an antenna. The UAH orbiter will only pass over Pwyll once, and Komitis will use that opportunity to capture the image using the hyperspectral imaging camera. Komitis won t be subject to harsh conditions on Europa, so it will only be enclosed by one layer of carbon fiber. Figure 5. Komitis Final Design/ConOps The landers, called the Mini Yetis, are 6 cm large cubes. There will be 9 Mini Yetis due to weight constraints. They are shaped as cubes because there is no wind resistance on Europa, and there is therefore no need to create an aerodynamic design. They will remain aboard the UAH lander until deployment. There will be a total of nine Mini Yetis aboard the lander. When the UAH lander begins the gravity null phase and comes to a stop, the Mini Yetis will drop onto Europa using gravity to fall. The Mini Yetis not slow themselves in any way before landing. The team decided on this because the carbon fiber housing would be able to sustain the impact and therefore the Mini Yetis would not use up more weight for the additional support equipment. Upon deployment, all instruments will be activated and will begin taking measurements. They will land and remain in Pwyll for a Europan day, taking measurements with the IMU and thermocouple. Data from the IMU will be used as seismic measurements and will be used to possibly determine the thickness of Europa s ice. The Mini Yetis will be contained inside a carbon fiber box that is 28 x 18 x 18 cm large. Inside of this box, there will be small ramps that will direct three trios of Mini Yetis in different directions upon deployment. In order to deploy the Mini Yetis, the box s bottom section will open, and they will drop due to gravity. Page - 7

9 Figure 6. Mini Yeti Final Design/ConOps Table 6. Komitis (orbiter) Final Design Mass Table Function Mass (kg) Deploy N/A Measure 1.9 Collect Data Provide Power N/A (2.9 W) Send Data.036 House/Contain Payload 2.03 Table 7. Mini Yeti (lander) Final Design Mass Table Function Mass (kg) (only one overall) Deploy Measure Collect Data Provide Power Send Data House/Contain Payload (for all 9, individual) Table 8. Payload Design Compliance Requirement Payload Design No more than 10 kg of mass Komitis weighs 2.03 kg and the total Mini Yeti weight is kg, leaving kg left over. Fit within 44cm x 24 cm x 28 cm when Both payloads together would fit into the stowed required size when stowed Survive environment Komitis will safely remain inside the UAH orbiter, the Mini Yetis instruments have thermal protection and have 5 layers of carbon fiber to survive impact upon landing No harm to the spacecraft Komitis doesn t deploy, Mini Yetis deploy using gravity Page - 8