L-MOSProposal
Mercury Lander Mission
Spring 2012
1.0Introduction
The InSPIRESS team gave Lee High School the challenge of designing a payload to fly to Mercury aboard the UAH designed spacecraft and conduct a scientific study. The team researched Mercury and spoke with a Jet Propulsion Laboratory Mercury specialist Noam Izenberg who suggested that Mercury surface has had little research done. The team researched Mercury and was intrigued by the fact that Mercury was so close to the sun they looked at influences from the sun as possible topics.
The team called itself the L-MOS for Lee Mission to Observe the Sun. The team consists of Project Manager, De’Sha Gragg; Chief Engineer, Chris Smith; and team members, Scott Pelzer, Roderick Cook, Kendrick Battle-Smith, Ivan Embden, Sierra Anderson, Derek Pickett, and Brian Simmons.
1.1Inspiration
The team divided into two parts with one part looking at research on Mercury’s surface and the other part looking at solar research. After weeks of research and investigation of the IKAROS solar sailing mission, the team thought that using the position close to the sun to act as an early warning detection system to study solar energy reaching Earth would be a valuable tool. The focus turned to study of solar sailing. The team consulted with Dr. Les Johnson and Roy Young from Marshall Space Flight Center solar sailing specialists, and Dr. Jonathan Certain and Allen Gary, solar physicists from Marshall Space Flight Center
1.2IKAROS
IKAROS is a solar sailing vessel launched in 2010 by the Japanese. It consisted of a large polyimide resin membrane that uses the pressure caused by light photons streaming from the sun to propel the vessel. The sail was 20 meters diagonal and is 0.0075 mm thick. It has thin film solar cells that are attached to the membrane to provide power and attitude control cells that lighten and darken to steer the sail. It also has scientific observation sensors.
2.0Science Objective and Instrumentation
The team’s science objective is: “Can they categorize the magnetic field and particles emitted by the sun to develop an earlier space weather warning system with the designed payload?” The instruments needed for the investigation are a magnetometer that will measure the magnetic field given off by the sun and a Faraday Cup.
2.1 Faraday Cup: The Faraday Cup will measure velocity, density, and temperature of the solar wind by determining the number of ions that will hit the cup. Ions will hit the cup and this clash will give off a small net charge which current will be read to determine the number of ions striking the cup.
2.2 The magnetometer: The magnetometer will measure the magnetic field of the Sun which tells us the flux. This measurement will aide in determining how the particles will travel to Earth and when and where they will reach.
2.3 Communications: The communications with the Earth will be accomplished with the High and Low gain k-band micro strip antenna array will be the instrument that will relay this message to earth. Its small mass, size, and power consumption makes it suitable for this payload.
Table 1. Science Traceability Matrix (Draft)
Science Objective / Measurement Objective / Measurement Requirement / Instrument SelectedHow does the magnetic field interact with particles in coronal mass ejections? / Flux of the sun’s magnetic field / Direction and strength of the magnetic field. / Magnetometer
Measure the most abundant particles in solar wind and there properties. / Density, velocity and kind particles in the solar wind and CME. / Velocity, density, and temperature / Faraday cup
Table 2. Instrument Required Resources (Draft)
Instrument / Mass (kg) / Power (W) / Volume (cm3)Magnetometer / .71 kg / .86 / 3cm by 10 cm
Faraday Cup / 4 kg / 1.3 W / 790 cm3
Communications / .05 kg / 50mW / 10.8by 0.025
3.0Alternative Concepts
Concept 1 is the Mercury surface mission. It consists of a camera to record images, a hydrogen generator as a converter to propel the device since Mercury’s atmosphere contains hydrogen, and a laser that will cut through the surface of Mercury into its deep surface. The device uses solar panels to provide power. The device is made of diamond steel which is durable and lightweight. It separates into two parts exposing the expose the instruments.
Figure 1. Group 1 Concept
Concept 2. This is a solar sail similar to the IKAROS sail mission. It will provide information about the solar wind and how it affects the Earth. This was the selected concept because it was exciting to find something relatively new that can study the sun.
Figure 2. Group 2 Concept
2Decision Analysis
The L-MOS team, like all engineering team used the Figure of Merit Method to come up with the best solution to their project.
4.1 Faraday Cup vs. Coronal Imager
One decision that the team had to make was whether to use the Faraday Cup (Concept 1), or the Coronal Imager (Concept 2). They came up with some Figures of Merit (FOM) to help them decide, and weighted each FOM on a 1,3,9 scale with 1 being the least important deciding factor to the project, and 9 being the most important deciding factor to the project. Each FOM and weight is depicted in the table below.
Table 5. Payload Decision Analysis
Figure of Merit / Weight / Group 1 Concept / Group 2 ConceptMass / 9 / 9 / 3
Volume / 9 / 9 / 3
Been on Past Missions / 3 / 9 / 3
Based on the table above, the L-MOS team decided to use the Faraday Cup (Concept 1) because it was more efficient on mass and volume, than the Coronal Imager.
4.2 Inflatable Deployment vs. Spinning Deployment
The L-MOS team had to decide on which deployment method to use. The two methods that were debated were to either use an Inflatable Deployment Method (Concept 1) or to use a Spinning Deployment Method (Concept 2). As in the previous Decision Analysis, the team had to create some FOMs and weight each one on the 1,3,9 scale. As before, the FOMs and their weights are shown in the table below.
Table 5. Payload Decision Analysis
Figure of Merit / Weight / Group 1 Concept / Group 2 ConceptSimplicity / 9 / 9 / 3
Effectiveness / 9 / 9 / 3
Reliability / 9 / 9 / 3
Based on the table shown above, the team decided to use the Inflatable Deployment Method as opposed to the Spinning Deployment Method. The Inflatable Deployment Method is easier for the team to use because it is more simple, effective and reliable.
5.0Payload Concept of Operations
The L-Mos will ride along the Mercury spacecraft until the Mercury Lander is jettisoned from the cruise stage. Just after this happens, and the Lander is safely away from the cruise stage, the L-MOS a computer program will signal the helium left over from the cruise stage to begin to fill the inflation tubes that will extend the solar sail to its full distance. A pyrotechnic valve will begin the inflation and another pyrotechnic valve will close once it is inflated. A small burst of helium will push the sail from the cruise stage and the tether will cut loose.
5.1 The solar sail is propelled by the pressure of photons. The sail will head away from the sun until it reaches an orbit of the sun at about 82 million km from the sun. Here is will continue to orbit the sun and stay as close as possible between the Earth and the sun. Once it hits this orbit the magnetometers and Faraday cup will operate continuously.
Figure 3. Payload Concept of Operations
6.0Engineering Analysis
The team has to do some mathematical calculations to determine the size of the sail. The size of the sail was determined by the position of the sail from the sun, the mass of the payload and the material the sail is made of.
7.0Final Design
7.1 L-MOS solar sail will orbit the sun at 82 million kilometers. They will be orbiting between the sun and earth at all times and will be orbiting 20% above the ecliptic plane so that the planets will not interfere with the transmissions.
7.2The payload, upon UAH Lander separation, will separate from the cruise stage and move a safe distance away from the Cruise stage remaining connected through a tether. A pyrotechnic burst opens and excess helium flows through the fore-mentioned tether. The helium inflates booms that expand the sail to its full size. These booms are made of a dense mesh of Kevlar fiber impregnated with resin called sub-Tg which becomes rigid. The cold of space caused it to become rigid and the booms, fully extend the sail. The pyrotechnic valve fires once again, closing the helium tanks off from the tether. The payload then disconnects from the tether, causing the higher pressure helium to escape out of the booms, pushing the payload away from the cruise stage. A small portion of the helium is used to orient the space craft. Mounted on the sail are a-Si thin film solar cells, these solar cells power the space craft.
7.2 For the team’s mission to observe the sun, the instruments will need to with stand the extreme conditions of this environment. The main instrument package (DPU, magnetometer, and communication antennas) for the mission will be placed behind the solar sail which will act as a sun shade. The temperature behind the solar sail is significantly reduced due to the fact that a majority of suns radiation (heat, light, and particles) is either reflected away from the solar sail or absorbed by the solar panels on the sail or the faraday cup which is placed directly in front of the sail. The faraday cup is placed in front of the sail because it is constructed with materials capable of enduring the sun’s radiation and also needs to be directly exposed to the radiation to capture particles emitted by the sun.
7.3 All electric components of the solar sail and payload will be internally grounded. The L-MOS team will not have the electronic components grounded to the casing, if so the casing will become electrically charged. This will cause the electronic components to be fried or interfere with the readings of the instruments.
Figure 4. Payload Final Design
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