Avionics System Project Team D3 Dylan Carter, Jesse Cummings, Kenneth Murphy, Rajesh Yalamanchili
Link Budgets for Communication Communication needs during the mission are divided into distinct phases, each with its own set of assumptions: o Earth-Lunar Transit o Lunar Operations o Lunar EVA
Earth-Lunar Transit The assumptions made for the first phase of the mission were: Communication with TDRSS, not DSN o Diameter of receiving antenna of 4.9m o Receiver system noise temperature of 100K Slant range was selected as the apogee radius of the moon as a worst case scenario
Ku and S Band to Earth Link Budgets The chosen diameter of the receiving antenna is 25.4 centimeters (1 foot) and is used for all subsequent transmissions from the crew vehicle to TDRSS Link Margin for Ku Band is 3.22 db, which is a safety factor of 2.1, with a transmitter power of 0.75 Watts Link Margin for S Band is 3.15 db, which is also a safety factor of 2.1, with a transmitter power of 17 Watts
Lunar Operations The assumptions made for the second phase of the mission were: o The distance from the moon to the L2 point is 60,000 km o The diameter of the receiving antenna of the L2 relay satellite is 4.9 meters (based off of TDRSS receiver diameter) o The diameter of the L2 relay satellite transmitter was assumed to be 2 meters (based off of TDRSS transmitter diameter)
Ka Band to L2 Relay Satellite Because of the proximity of the satellite, the transmitter diameter for communication to the L2 Relay Satellite was assumed to be 10 centimeters The link margin for this signal was determined to be 57.5 db, which results in an extremely large safety factor of 566,218 with a transmitter power of 1 Milliwatt Because of the huge link margin, communication is practically guaranteed with the L2 Relay Satellite barring malfunction of hardware
Ku Band of L2 Relay Satellite to TDRSS The transmitter diameter was 2 meters, as per the specifications of the TDRSS satellites The link margin for this signal was determined to be 3.19 db, which is a safety factor of 2.1 with a transmitter power of 0.01 Watts
Lunar EVA The assumptions made for this phase of the mission were: o A maximum slant range of 15 kilometers, based on an expansion of the 12.1 kilometer distance achieved during the Apollo 17 mission o A receiver system noise temperature of 100K o An omni-directional transmitter/receiver
EVA UHF Band The link margin for this signal was determined to be 10.87 db (safety factor of 12.2), with a transmitter power of 0.01 Watts The low power consumption of this system is advantageous to this phase of the mission, where low power requirements are necessary for periods of time when the vehicle will not be exposed to the sun to generate power. The same holds true for the Ka to L2 Relay Satellite Band.
Sensors Many sensors required to measure and regulate state of the craft o Regulate crew cabin conditions o Identify relative attitude and position in free space o Track usage of propellants and consumables o Measure power requirements and consumption
Crew Systems Sensors Life support of crew is of the highest importance o Unwanted deviation from design conditions can cause reduced human performance or death o Excessively high or low temperature may damage components o Improper depressurization prior to EVA wastes valuable oxygen stores o If emergency redundancy systems are in place, must be aware of system failures
Measured Quantities: o Cabin Pressure o o o Crew Systems Sensors Used at all times by O2 and N2 resupply systems Also monitored during airlock operation Atmosphere Composition Regulate relative composition of O2 and N2 Measure CO2 and H2O for proper scrubbing Tank Pressures Pressure transducer data used by helium pressurization system for O2 and N2 tanks Consumables Remaining Flow rate monitored during operation to track usage
Crew Systems Sensors Measured Quantities (continued): o Waste Tank Level o o Monitored for proper waste ejection Temperature Internal and external thermocouples for best thermal control Used at all times by thermal regulation system Radiation Geiger counter to identify unexpected radiation Alerts crew to hazardous conditions
Attitude and Position Sensors Accurately determining relative position and orientation in space is critical to mission success o Attitude must be correctly estimated to perform successful orbital maneuvers o Entry, descent, and landing rely on accurate proximity and relative position measurements o Can be very difficult to determine exact relative position and velocity in free space
Attitude and Position Sensors Measured Quantities: o Attitude o Sun sensor measures attitude relative to the Sun Star tracker compares star profile against database to obtain attitude relative to stars (free space) Magnetometer gets attitude relative to geomagnetic field (only effective near Earth) IMU and gyros track angular changes over time Rotation Gyros and MEMS measure angular rotation IMU tracks angular acceleration over time to obtain velocity
Attitude and Position Sensors Measured Quantities (continued): o Position o o Laser rangefinder determines distance from lunar surface during landing IMU tracks position changes over time Velocity IMU and MEMS can determine velocity from acceleration changes Acceleration IMU and MEMS measure instantaneous acceleration
Propellant Sensors Proper staging and engine performance rely on accurate measurements of propellant usage o o Helium pressurization requires constant pressure measurement Spent stages detach when tanks are empty o Measured Quantities: o o Propellant Tank Pressure Same type of system as on crew consumables tanks Used by helium pressurization system Propellant Usage Same type of system as on crew consumables tanks Flow rate monitored during operation to track usage
Power Consumption Sensors Important to track power consumption and production, and demand on power supply Measured Quantities: o H2 Levels in Fuel Cells Determines remaining fuel in power supply o Power Consumption Multimeter measures power draw from all systems
Sensor List Sensor Sensor Type Sampling Rate Location Number Criticality* Atmospheric O2 Apogee Instrument 0.084 Hz Radially-mounted on inside 4 1 Oxygen Sensors cabin wall Atmospheric N2 OxyCheq R-33N Nitrogen Sensors 0.1 Hz Unique locations inside the cabin 2 2 Atmospheric CO2 CO2Meter Carbon Dioxide Sensors 2 Hz Radially-mounted on inside cabin wall 4 1 Cabin Pressure Setra Model 270 100 Hz Mounted inside cabin 2 1 Oxygen Tank Nitrogen Tank Cabin Humidity Water Tank GEMS SENSORS Flow rate sensor Swagelok Explosion-Proof Pressure Transducer GEMS SENSORS Flow rate sensor Swagelok Explosion-Proof Pressure Transducer Omega Relative Humidity Sensor GEMS SENSORS Flow rate sensor Swagelok Explosion-Proof Pressure Transducer 30 Hz Mounted in-line with feed lines 2 2 1 khz Mounted inside tank 2 3 30 Hz Mounted in-line with feed 2 2 lines 1 khz Mounted inside tank 2 3 Mounted inside cabin 2 3 30 Hz Mounted in-line with feed 2 2 lines 1 khz Mounted inside tank 2 3
Sensor List Sensor Sensor Type Sampling Rate Location Number Criticality* Radiation Edmund Scientifics Portable Geiger Counter 250Hz 50kHz Mounted inside cabin 2 3 Power Fluke Digital Multimeters 625 Hz Connected to each major power-using device 10 2 Internal Temperature External Temperature Omega Thermocouples 100 Hz Mounted inside cabin 4 2 Omega Thermocouples 100 Hz Mounted to outer shell 4 2 Fuel Cell Fluke Digital Multimeters 625 Hz Connected to output of fuel cells 8 2 Sparkfun Hydrogen Sensor N/A Mounted near fuel cells to detect leaks 8 2 Propellant Tank GEMS SENSORS Flow rate sensor 30 Hz Mounted in-line with feed lines 2 2 Swagelok Explosion-Proof Pressure Transducer 1 khz Mounted inside tank 2 3
Sensor List Sensor Sensor Type Sampling Rate Location Number Criticality* Position On Semiconductor High Accuracy Star Tracker 5 MHz Mounted on outer shell 4 1 CubeSat Sun Sensor 10 Hz Mounted on outer shell 4 1 Sparkfun IMU 1 khz Mounted inside the cabin 4 1 Rate Altheris Single-Axis Gyroscope 55 Hz Radially-mounted, in-plane with center of gravity inside the cabin 4 1 Altheris Dynamics Measurement Unit 45 Hz Radially-mounted, in-plane with center of gravity inside the cabin 4 1 Proximity Banner Engineering Laser Rangefinder 115 khz Mounted next to docking mechanism and landing gears 4 1 Landing Gear Kavlico Landing Gear Control N/A Mounted inside cabin, connected 2 1
Basic Avionics Sensor Architecture
DBTE Project Idea #1 Research Objective: o To examine the effects of close confinement with other people as well as assess the human factors when designing a crew cabin, such as comfortability and ergonomics. Required Test Apparatus: o A partially-functioning full scale model of the crew cabin.
DBTE Project Idea #1 Test Operations: o A group of three volunteer students in the class would go through a partial mission simulation of the most stressful mission phase, Earth-Lunar transit. The "realness" of the simulation could be varied as deemed appropriate. Students partaking in the simulation would keep a log of what could be changed about the layout of the crew cabin and the functionality of certain components.
DBTE Project Idea #2 Research Objective: o To design and build a functional docking mechanism for the capsule. A compact docking mechanism inside the nose cone of the capsule is critical for a staged mission to the moon. Required Test Apparatus: o A full-scale model of the nose cone geometry for use in the neutral buoyancy tank in the Space Systems Laboratory.
DBTE Project Idea #2 Test Operations: o A group of students (ideally belonging to the structures group) designs and builds a functioning model of the docking mechanism and what it couples to. Using the neutral buoyancy tank, scuba-certified students will simulate docking using real approach rates according to NASA standards. Assuming successful docking, functionality and improvements to the design will be assessed based on the results of the simulation.
Capsule in Neutral Buoyancy Lab http://wmahsj.org/wp-content/uploads/2011/07/buoyancy-lab1.jpg
DBTE Project Idea #3 Research Objective: o To examine the dynamics of the crew cabin to assess the effectiveness of the attitude control system. Required Test Apparatus: o A scaled or full-scale model of the crew cabin with attached motors that will provide a scaled similar amount of force as an actual attitude control system. This will all be performed in the Neutral Buoyancy Facility on campus.
DBTE Project Idea #3 Test Operations: o A team would first determine how to attach foam blocks onto the cabin to make it neutrally buoyant while minimizing the effects this has on the dynamics of the object. After that is completed, underwater thrusters would be attached to the cabin to simulate real attitude control thrusters, and the effectiveness of the system can be roughly approximated.
Similar to SCAMP Testing
Sensor Links CO2 Meter. CO2Meter. 14 Dec. 2012 <http://www.co2meter.com/collections/co2-sensors>. Digital Multimeters. Fluke Instruments. 14 Dec. 2012 <http://www.fluke.com/fluke/usen/products/categorydmm.htm?id=dmmfunnel-en>. Flow Rate Sensor. GEMS SENSORS. 14 Dec. 2012 <http://www.grainger.com/grainger/gems- SENSORS-Flow-Rate-Sensor-4ARL1>. High Accuracy Star Tracker. ON Semiconductor. 14 Dec. 2012 <http://www.onsemi.com/powersolutions/product.do?id=has2>. Hydrogen Gas Sensor. Sparkfun. 14 Dec. 2012 <https://www.sparkfun.com/products/10916>. IMU Digital Combo Board. Sparkfun. 14 Dec. 2012 <https://www.sparkfun.com/products/10121>. "Landing Gear Control (LGC)." Landing Gear Control (LGC). Kavlico Sensing Solutions. 14 Dec. 2012 <http://www.kavlico.com/catalog/landing_gear_control.php?section=products>.
Sensor Links Laser Sensors. Banner Engineering. 14 Dec. 2012 <http://www.bannerengineering.com/en- US/products/8/Sensors/38/Laser-Sensors>. Model 270. Setra. 14 Dec. 2012 <http://www.setra.com/productdetails/270_baro.htm>. OxyCheq. OxyCheq. 13 Dec. 2012 <www.oxycheq.com/index.php?main_page=product_info&cpath=1_6&products_id=28>. Oxygen Sensors. Apogee Instruments. 14 Dec. 2012 <http://www.apogeeinstruments.com/oxygensensor/>. Portable Geiger Counter. Edmund Scientifics. 14 Dec. 2012 <http://www.scientificsonline.com/portable-geiger-counter.html>. Pressure Transducers. Swagelok. 14 Dec. 2012 <http://www.swagelok.com/products/measurement-devices/pressure-transducers.aspx>.
Sensor Links Relative Humidity Sensor. Omega. 14 Dec. 2012 <http://www.omega.com/ppt/pptsc.asp?ref=hx15&nav=temhu06>. Silicon MEMS Single-Axis Gyros. Altheris. 14 Dec. 2012 <http://www.altheris.com/products/angular-rate-silicon-mems-single-axis-gyros.htm>. Sun Sensor. Cubesat. 14 Dec. 2012 <http://www.cubesatshop.com/index.php?page=shop.product_details&product_id=104&flyp age=flypage.tpl&pop=0&option=com_virtuemart&itemid=65&vmcchk=1&itemid=65>. Thermocouples. Omega. 14 Dec. 2012 <http://www.omega.com/prodinfo/thermocouples.html>. SCAMP Testing. 8 Aug. 2007 <http://spacecraft.ssl.umd.edu/ssl.photos/nbtest.photos/nbtest.2007/070808.nb07-078/070808.nb07-078.19.jpg>.