Low Ballistic Coefficient Re-Entry Probe

1. Low Ballistic Coefficient Re-Entry Probe K. Ramus (kevinramus@vandals.uidaho.edu)1,B. Holmes1,A. Camery1, D. Eld1, R. Riggs1, R. Gunn1, D.H. Atkinson1, M. Murbach2, and the Univ. Idaho RISE Student Launch Team1 1University of Idaho, 2 NASA Ames Research Center Abstract: There are regions of the Earth’s atmosphere that are especially difficult to study. One of these is between 30km and 100km. NASA Ames has been developing scientific payloads to fly on sounding rockets to reach this region. Since 2007, the University of Idaho Near Space Engineering program has worked with the SOAREX program at NASA Ames to develop low-ballistic coefficient descent systems for slow descent through the 30-100 km region. The current project comprises a small 2.2 kg probe beneath a parachute with an area of about 1.35 square meters. This system allows the probe to descend very slowly and allows for large amounts of data to be gathered in the upper atmosphere. The probe, equipped with a PCB board that includes 3 temperature sensors, 2 pressure sensors, an accelerometer, a Geiger counter, a GPS unit and a beacon for tracking, and an SD card for data acquisition and storage, will be deployed at about 85-90 km. The data is recorded as a function of altitude, and the pressure and temperature sensors are used to determine the elevation and descent speed. Since a GPS is being used for tracking, the accuracy of the calculated descent trajectory profile can be determined. Measurements of atmospheric pressure and temperatures will characterize the atmospheric structure along the descent path. The probe will be sent to Ames for vibration, shock, and thermal/vacuum testing prior to launch from NASA Wallops Flight Facility in Virginia. Background: In 2008 the SOAREX program at NASA Ames Research Center provided funding for a University of Idaho senior engineering project to design, build, and fly a low ballistic coefficient descent probe. The probe is to be launched aboard a sounding rocket from NASA Wallops Flight Facility. The Idaho Vandal Atmospheric Science Team (VAST), the University of Idaho chapter of the Idaho Space Grant Consortium (ISGC) RISE student launch program, continued work on the capsule following the completion of the senior design program. VAST is a student led class that consists of around 20 graduates and undergraduates from many disciplines, including electrical, mechanical, and computer engineering and physics. The main purpose of this project is to improve the physical design of the probe, and to achieve a ballistic coefficient of 1. The probe carries temperature and pressure sensors, accelerometers, and a radiation detector. Data is stored on board, so all data is recorded for later retrieval and analysis after the probe is recovered. The probe payload uses a redundant tracking system that includes a tracking beacon and a GPS receiver/transmitter. The tracking beacon will assist with locating the probe after reaching the surface, while the GPS receiver/transmitter will allow the probe flight path to be tracked. Instrumentation Flight Plan Capsule Design The structural design is based on a preliminary design as part of a engineering senior design project, but many improvements have been made. In particular, the body length has been extended, an improved seal and end cap system were designed to better seal the probe and to make the interior more accessible. The structure is sufficiently buoyant so that the antennas will remain above the water line. To protect the capsule from the mild descent heating, Teflon was chosen for a simple, light-weight and low cost TPS system. • The data logger was designed by the VAST team. An existing set of cubesat boards has been flown successfully on many previous high altitude balloon launches. A new data logger was needed that would fit into the 4” diameter probe body. This new design copied the old boards as much as possible for reliabilities sake. The board has the following important features: • Arm – 7 Microprocessor • SD Card for storing data from the following sensors: • Pressure • Temperature • 3 Axis Accelerometer • Radiation • Gravity-Switch activated power circuit (Allows power flow when the launch is detected) • 10 Hz Sampling Rate • GPS Receiver The University of Idaho capsule will be launched from Wallops Flight Facility on an Improved Orion Sounding Rocket. Launch is tentatively planned for late 2010 or early 2011. • The Body • 13” Long Aluminum Body • 4” diameter • Machined Aluminum End Caps • O-Ring seals • The Nose Cone • 3” Long • Machined Teflon • Houses large pressure sensors Power Due to the nature of launches, which are highly dependent on weather, a design was needed to power the instrumentation at launch, and also have it in standby for an extended period of time. An 11.1V battery pack is attached to a latching relay circuit. The latching relay is routed through a 2 parallel g-switches, which will trigger on launch, and the latching relay will move power to the rest of the electronics for the duration of the flight. The batteries are located near the nosecone to help the capsule float nose-down in the water. The battery pack is a Lithium battery, due to the power required. Tracking Accurate and reliable tracking is an essential part of the probe launch system, since the probe must be recovered to analyze the gathered data. For redundancy, the probe carries two independent tracking systems. The first is the Microtrak 8000FA. This is a commercial product that has a GPS receiver and transmitter, and provides the probe location and elevation. This will allow the path of the probe to be known, and will help determine the approximate location of the probe when it enters the ocean. The probe will also have a radio beacon, and with the use of a directional antenna, the beacon should lead the recovery boat straight to the probe. How the Microtrak works with the GPS to determine the probe’s location. Timeline • Fall 2009 / Spring 2010 • The VAST team picked up the project, and began to work on improving the design. Accomplishments for the semester include: • Lengthening the probe body for improved buoyancy and payload volume with a small impact on probe mass. • Redesigning the data logging board to record temperature, pressure, accelerometry, and radiation versus elevation. • Chose a reliable, previously used, tracking system and the beacon. • Fall 2010 / Spring 2011 • Final testing of the data logging board will be completed, followed by system integration and integration testing. The fully integrated flight probe will be sent to NASA Ames for thermal-vac, vibration, centrifugal (g), and shock testing. Launch is anticipated in Spring, 2011. The Microtrak GPS Unit Acknowledgments Summary The University of Idaho VAST team would like to acknowledge the support provided by the Marc Murbach and the NASA Ames SOAREX program, Dr. David Atkinson and the NASA Idaho Space Grant Consortium. The goals of this project are to demonstrate that a low-cost, low ballistic coefficient capsule to study the upper atmosphere can be developed at low cost, and to introduce undergraduate and graduate science and engineering students to aerospace design. Univ. Idaho RISE Student Launch Team: G. Wilson, S. Wagoner, C. Abraham, K. Baird, S. Rainsdon, M. Zarate, J. Brubaker, G. Korbel, W. Taresh, G. Gallagher, T. Lenberg D. Rickford, C. Lawrence, C. Birkinbine, C. Gonzalez, B. Kisling, J.Henry, J. Law, D. Taylor, C. Booth