Developing the HTTP-3S Sounding Rocket Avionics and Ground Station System

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"With the advantage of built-in processor and auxiliary FPGA, the NI sbRIO is able to accommodate all needs dedicated to diversity of applications. Also, tremendous amount of examples and design tips drastically shorten the development time which is an ideal prototyping platform from concept to reality."

- Cheng Chun-Chi , Mechanical Engineering Department, National Chiao Tung University

The Challenge:
Designing a system between the navigation computer and the ground of a 1,000 kgf sounding rocket and rapidly performing system modification and program changes based on the task requirements.

The Solution:
Using LabVIEW software and Single-Board RIO hardware to rapidly design the sounding rocket navigation computer and the dual-band ground station, and to pass the test and verification in harsh environments.

Author(s):
Cheng Chun-Chi - Mechanical Engineering Department, National Chiao Tung University
高 碩聰 - 成功大學工程科學所 - 博士生
趙 冠舜 - 交通大學前瞻火箭研究中心 - 專任助理
劉 訓彰 - 台北科技大學電子工程系 - 碩士生
鐘 聖彥 - 銘傳大學資訊管理研究所 - 碩士生
陳 庭維 - 交通大學前瞻火箭研究中心 - 專任助理
周 子豪 - 交通大學機械所 - 博士生
賴 冠融 - 交通大學機械所 - 博士生
魏 世昕 - 交通大學機械所 - 博士生
林 哲緯 - 交通大學前瞻火箭研究中心 - 專任助理

The Sounding Rocket Team

The team members of HTTP Sounding Rocket Team are professors, researchers, and more than 30 master’s and PhD students from the four regions of Taiwan, including Hsinchu, Taipei, Tainan, and Pingtung. The hub of HTTP Sounding Rocket Team is the Advanced Rocket Research Center (ARRC) founded at the National Chiao Tung University in 2012 partially from the donations of individuals and companies. Our goal is to build rocket engineering and scientific research capability in Taiwan’s academia locally. Rocket engineering is a demanding cross-disciplinary engineering project that must integrate technologies such as mechanics, electromechanical control, communication, composite materials, combustion, propulsion and aerodynamics. Through restless efforts and improvements, ARRC has migrated from the primitive Sugar Rocket of tens of kgf to the hybrid fuel rocket of more than 1000 kgf now. It is our dream to build a safe, reliable and affordable space transportation vehicle for Taiwan’s near space research in the future.

Figure 1. Scales of Sounding Rockets Developed by ARRC

Figure 2. Static Tests of Two Sounding Rocket Engines

Mission Description

Our mission is to design the navigation computer onboard the HTTP-3S sounding rocket and its ground stations. The HTTP-3S rocket is 6.35 meters long and 0.4 meters in diameter propelled by a multi-cluster vortex mixed booster (patent acquired in both Taiwan and the United States) hybrid engine which employs N2O as oxidizer. The engine is capable of delivering a world leading 1,000 kgf (with Isp up to 250 seconds) thrust for more than tens of seconds. With this engine, ARRC is able to build the largest sounding rocket in Taiwan’s academia. The goal of this launch campaign is to test functions of all subsystems during the drastic high-speed flight scenario. In the meantime, the flight data can be help the 2nd stage rocket design of the future dual-stage sounding rocket and the validation of launch site safety measure.

Figure 3. HTTP Team Group Just Before the HTTP-3S Sounding Rocket Launch

Figure 4. HTTP-3S Launch on March 24, 2014 in Southern Taiwan

HTTP-3S Sounding Rocket System Architecture

The HTTP-3S sounding rocket (Figure 5) comprises distributed avionics system, dual-frequency long-distance communication system, distributed network ground station, real-time interactive display system, dual-stage side-opening parachute system, yo-yo despin system, carbon fiber wrapped pressure container for N2O storage, composite material fuselage and launch rail system (13 meters tall). In this section, we will elaborate more about the distributed avionics system, dual-frequency long-distance communication system, distributed network ground stations and real-time interactive display interface developed based on NI products.

Figure 5. Key Components of HTTP-3S

What NI can do in this project?

Within this particular task, NI products played significant roles in development of the navigation computer and the ground station. The navigation computer of HTTP-3S sounding rocket is developed in the dual avionics architecture (Figure 6) to shoulder the data acquisition load between computers and sensors such as advanced GPS receiver for position/velocity, digital IMU sensor for altitude, acceleration, angular speed and tank pressure that can reveal fuel level. Also, the navigation computer shall be able to activate flow servo control valve at the correct timing to ignite the engine and calculate/predict proper timing to open the parachute for smooth landing. On top of those, the system will face the harsh environment all the way from launch to reentry.

With carefully designed and manufactured compartment, the NI embedded system is able to prevail the shock and random vibration tests that are set to reproduce the harsh launch environment (Figure 7).

Figure 6. The HTTP-3S Dual-Avionics System Architecture Diagram and Key Avionics Components

Figure 7. The Impact and Vibration Test of the Avionics System

The rocket communication subsystem is partitioned into two parts: The onboard RF component that transmits data via two different frequencies, 434MHz and 2.4GHz (Figure 7 & 8), and the ground stations working as a distributed network. Through the two frequency bands at 434 MHz and 2.4 GHz, the avionics data and scientific data could be transmitted to multiple ground stations simultaneously (Figure 9). Note that the onboard RF component also survives the same harsh environment tests that navigation computer went through. The backbone of ground station is LabVIEW software with Single-Board RIO hardware (Figure 10). With the distributed network architecture, the ground station can alleviate the data loss problem due to antenna dead angles by resemble downlink data from multiple stations. Also, to accommodate unknown number of flight data users without overloading the ground station, the scalability of LabVIEW helps to display the test data from the ground station in real-time at launch site and to transmit those data back to the PXI server located in National Chiao Tung University through the common 3G network. Each engineer can rapidly customize the HMI using LabVIEW Data Dashboard to visualize the data in near real time for decision making. Meanwhile, we visualize the rocket trajectory on Google Earth to one of the ground stations in near real time manner.

Figure 8. 434 MHz Communication Components

Figure 9. 2.4 GHz Communication Components

Figure 10. Dual-Frequency Long-Range Communication Network for HTTP-3S.

Figure 11. The Distributed Network Ground Stations and Near Real-Time Interfaces.

Benefits of NI Software and Hardware

After careful evaluation, we introduced NI software and hardware to the rocket’s avionics and ground system because NI provides:

  • A set of program development software that applies to many hardware platforms
    An embedded system with FPGA and processor is a common solution to many problems in industry and the solution for our navigation computer and the ground stations whose backbone is LabVIEW and Single-Board RIO. With FPGA, we can simply just revise the circuit slightly when we need to interface with a new sensor or the peripheral interface instead of reconstructing the entire hardware architecture. Note that complicated algorithms such as calculation in floating point, prediction and control are not easy to implement in FPGA, the processor of Single-Board RIO provides an ideal resolution for those needs. Clearly, users will have difficulty to master both different languages and coordinate the interaction of both devices.  Fortunately, on NI platform, we could perform program development in a well-coordinated manner simply on LabVIEW platform such as the computer or in the real-time system, the FPGA, or the embedded system using just.
  • Rich technical resources
    LabVIEW offered tremendous resources that saved time for development and helped the team can focus more efforts on system development. For example, the LabVIEW FPGA IPNet provided examples of FPGA application development programs, the sample programs referenced in the development of the SPI interface of the sounding rocket navigation computer. The NI Instrument Driver Network (IDNet) offered many driver programs for the device interface so that the team did not need to reprogram the monitoring devices for the environment testing system. There are several useful technical articles on the NI website that helped the team to gain a quick inside of the practical applications and speed up their development.
  • Strong support
    NI provided a number of support services to the users. Conventional development platforms only support network inquiry, literature search, or asking teachers and seniors as indirect solutions to break through bottlenecks or problems. The LabVIEW development platform offers technical discussion over the phone and troubleshooting with local application engineers onsite, in addition to the technical information provided on the NI website.

Our Vision for the Future

In this project, NI product, LabVIEW along with Single-Board RIO, proves itself an ideal platform to the development of 1000-kgf HTTP-3S onboard navigation computer and ground stations after a series of stringent environment tests and real flight test. With this platform, HTTP team plan to introduce more sophisticated and reliable flight control technology aiming at more complicated and rigorous flight condition of the next generation HTTP-3 dual stage sounding rocket propelled by greater propulsion system. The rocket is scheduled to reach an altitude of 130 to 150Km for ionospheric related experiment by the collecting various scientific data around that region, a project that will get our team closer to the dream of space exploration.

Author Information:
Cheng Chun-Chi
Mechanical Engineering Department, National Chiao Tung University
pocky917@hotmail.com

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