Shepard Test Stand Initial Questions v2.0

Below is a list of questions and proposed answers to help us narrow down the requirements for this project. You can view the original forum discussion here .

This is a newer document based on this one , and you should refer to that original version if you want to see the revision history.

Q1. Why are we making this?

A1. The Shepard Test Stand is the first step toward developing an open source test stand for flight capable rocket engines. It's focus on low power, commercially available amateur rocket motors is intended to provide a safe first experience for both designers (low power and low cost lead to little penalty for failing to meet design goals the first time around) and operators (low power leads to lower cost if accidentally misused during early training). Additionally, as one of Mach 30's earliest open source hardware projects, it will give us practical experience in open source hardware development and managing projects on Open Design Engine (ODE). Finally, we have received interest in performing live demonstrations of the test stand as part of educational and outreach activities, so it is expected the test stand will become an educational and marketing tool.

Q2. Who is this for?

A2. The Shepard Test Stand is for anyone wanting to learn about measuring the performance of rocket motors. This includes open source spaceflight designers who will design and build future test stands (at Mach 30 or elsewhere), Mach 30 operators who will use future test stands in other Mach 30 projects, students and educators who want to bring rocket engineering into the classroom, and anyone else interested in how rockets are tested. To ensure the Shepard Test Stand will be accessible to the entire user community, including users with no experience in spacecraft engineering, the Shepard Test Stand team has selected a representative user with limited experience in spacecraft engineering and testing hardware. This representative user is a middle school (6th through 8th grade in the U.S.) teacher who does not have the support of an IT department, and who does not have computer expertise beyond how to connect a USB cable and install software, but has the desire to introduce their students to rocket science in a safe and hands-on way.

Q3. How will this be used?

A3. The final test stand will be used for verification of typical motor performance metrics such as thrust and casing temperature. The thrust metric will be compared against benchmark values provided in the Estes motor documentation . The test stand will then be used as a tool to teach rocket engineering in classrooms, and to do demonstrations at various conferences and educational events (outdoor only).

Q4. What features does it need to have (now)?

A4. The test stand needs to:
  • Provide a stable base on which to test model rocket motors.
  • Accommodate Estes rocket motor sizes A through E.
  • Provide the ability to measure motor thrust while keeping an accurate timestamp for each data point.
  • Provide the ability to measure motor case temperature or flame temperature while keeping an accurage timestamp for each data point.
  • Allow for the thermal sensor to be moved so it can either measure case temperature or flame temperature. Note, when measuring the case temperature the DAQ will need to collect data for longer than the thrust duration to capture the temperature change in the case after the motor finishes firing.
  • Keep cleanup and maintenance to a minimum between consecutive test firings.
  • Have a motor mount which will survive motor failure or be relatively easy to replace in the event of a motor failure.
  • Be easily set up and torn down for demonstration purposes. Specifically, the setup and tear down procedures should be tool-less, or at a maximum require simple tools such as screwdriver and/or hammer rather than something like a masonry drill bit.
  • Be easy to package for shipment to any event at which it will be used. Be particularly aware of dimensions and weight and how they impact shipping costs. Note, CCSSC intends to use up to 10 test stands at a time, so transportation considerations should also take into account transporting multiple test stands.
  • Conform to the safety requirements as outlined in section 8.3 of the NAR Standards & Testing Committee Motor Testing Manual Version 1.5 .
  • Be "hackable" so users and makers are encouraged to experiment with the design of the test stand.
  • Provide space for labels to be added for safety warnings, branding, etc.
  • Have desktop control software that will run on all three major PC platforms (MS Windows, Mac OS X, and Linux).
  • Include a DAQ system that uses standard connections back to the control software (for example, USB, Ethernet, or similar connections).

Q5. What features does it need to have (later)?

These features will not necessarily make it into any version of Shepard, but should be kept in mind for any of its larger sibling test stands later on.

  • High and low speed video capture of the tests from multiple angles.
  • Integrated ignition system so the test management software can control the entire test.
  • Additional measurements.
  • Higher resolution measurements.
  • Higher sample rates.
  • Accommodation of:
    • High power commercial solid motors.
    • Small hybrid motors (on the thrust scale of high power commercial solid motors).
    • Larger thrust hybrid motors.
    • Small liquid engines.
    • Medium liquid engines.
    • Large liquid engines.

Q6. What are the legacy requirements?

A6. Two features of the v1.x test stand are very desirable in future versions.

  1. The structure should easily mount to a concrete block without the need for special tools or modifying the block.
  2. The DAQ should use an Arduino as the interface between the sensors and the data collection computer.

Q7. Who's going to build this?

A7. The designs will be open so that anyone, without necessarily a technical education in rocketry, propulsion, or engineering, would be able to build and operate a Shepard Test Stand. Specifically, in order to support the use of the Shepard Test Stand in classrooms, teachers and students should be able to build the test stand from parts or kits.

Q8. How many do we want to make?

A8. Previous efforts focused on developing the single initial prototype. The success of this prototype and the very strong interest in the use of the Shepard Test Stand in schools (middle school through college) has led Mach 30 to decide it will sell Shepard Test Stand kits for use in schools, scouting troupes, and makerspaces. This means developing the Shepard Test Stand into a finished product. So, the short answer to this question is "as many as the market demands."

Q9. What is the budget?

A9. Based on feedback form CCSSC, the final cost for Shepard Test Stand kits needs to be around $200 (though having a data component and being reusable like Shepard could allow for higher prices). Using the standard OSHW cost multiplier of 2.6, the total cost for parts and labor needs to be around $78 (note, the most recent experiments in structure design have a materials cost of about $40). To allow for several additional prototypes while still holding the materials cost down, the updated structure budget has a threshhold (maximum value) of $150 and an objective of $100.

Q10. What is the timeline?

A10. The v2.0 prototype (completed structure integrated with existing v2.0 prototype DAQ) needs to be complete and have its initial test firing by Dec 31, 2013. This timeline works with the efforts by the Coca-Cola Space Science Center to develop curriculum for the Shepard Test Stand (as long as they have early access to new structure prototypes).

Q11. What waste products will be produced by the manufacture and/or operation of this?

A11. Spent Estes motors will be a waste product of the operation of this test stand, and any residual materials should be treated as hazardous. Disposal of these motors should conform to all local, state, and federal guidelines. Estes motors are based on black powder propellant, so any motors that do not fire properly or are damaged can be disposed of in an ordinary manner by first soaking them in water until the casing unwraps and the propellant falls apart. Possible electronic waste items may include batteries from the ignition control box, and circuit boards. These must also be disposed of according to all local, state, and federal guidelines. If the frame of the test stand is damaged beyond repair during operation, proper disposal/recycling guidelines must be followed for the materials used in its construction.

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