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J. Simmons, 05/20/2012 11:47 pm

Shepard Test Stand Requirements Document v1.0


This requirements document is currently being discussed on the forums here. The requirements list matches up to the Initial Questions in step one of the Systems Engineering process as shown below. Each requirement is labeled with STSR (Shepard Test Stand Requirement), followed by the number of the initial question that the requirement corresponds to, followed by a dot and then the ID number of the requirement.

  • STSR 1.x - Why are we making this?
  • STSR 2.x - Who is this for?
  • STSR 3.x - How will this be used?
  • STSR 4.x - What features does it need to have (now)?
  • STSR 5.x - What features does it need to have (later)?
  • STSR 6.x - What are the legacy requirements?
  • STSR 7.x - Who's going to build this?
  • STSR 8.x - How many do we want to make?
  • STSR 9.x - What is the budget?
  • STSR 10.x - What is the timeline?
  • STSR 11.x - What waste products will be produced by the manufacture and/or operation of this?

Technical Requirements

Technical requirements are those requirements which include measurable performance values. Each technical requirement should be verified through testing to ensure the design meets the requirement.

  • STSR 1.1 The STS must accommodate low power, commercially available amateur rocket motors sized A through E.
  • STSR 1.2 The STS must be mobile enough to enable live demonstrations as part of educational and outreach activities.
    • STSR 1.2.1 The STS total weight shall be less than 25 lbs. or be able to break into components that weigh no more than 25 lbs each (based on OSHA recommendations).
    • STSR 1.2.2 The STS must be transportable by 1 person.
  • STSR 4.1 The STS shall be easily set up and torn down for demonstration purposes.
    • STSR 4.1.1 unpack and set up time should be less than 45 min.
    • STSR 4.1.2 clean up and storage time should be less than 90 min.
  • STSR 4.2 The STS shall be easy to package for shipment to any event at which it will be used meaning the whole test stand system shall fit in the backseat or trunk of a standard 4-door sedan.
  • STSR 4.4 IAW (In Accordance With) NAR testing manual requirements specified in Section 8.5, the STS shall use a data collection system where the sample rate is "1000 samples per second or greater for motors with a burn time of less than 1 second, and at least 500 samples per second for all other motors" 1
  • STSR 4.5 Load cell requirements
    • STSR 4.5.1 IAW NAR testing manual requirements specified in Section 8.5, the STS shall use a “load cell calibrated with a NIST traceable weight standard”. 1
    • STSR 4.5.2 IAW NAR testing manual requirements specified in Section 8.5, the STS shall use a data collection system "where the least significant bit (LSB) has a value that is" 0.006 lbs ("less than 0.33% percent of the average thrust of the motor under test"). 1
  • STSR 4.6 Thermocouple requirements
    • STSR 4.6.1 IAW NAR testing manual requirements specified in Section 8.6, the STS shall use thermocouples with "a low thermal mass, and including the amplifier and readout system still be accurate to 10 degrees C" 1
    • STSR 4.6.2 IAW NAR testing manual requirements specified in Section 8.6, the STS shall use thermocouples with a thermal response of "5 seconds or less" 1
    • STSR 4.6.3 IAW (partial) NAR testing manual requirements specified in Section 8.6, a thermocouple will be attached to the motor under test "where the propellant and nozzle meet". 1 Full compliance with this requirement has been moved to the future requirements section below.
  • STSR 4.7 IAW NAR testing manual requirements specified in Section 8.5, the STS shall "store the collected data into a general use data formats [sic], such as a .txt, .csv" 1
  • STSR 4.8 The data collection system must have a threshold (minimum) of 2 ADC (Analog to Digital Converter) channels, with 4 being the objective.
  • STSR 6.1 Any desktop computer based control software for the STS should run on all three major PC platforms (MS Windows, Mac OS X, and Linux).
  • STSR 6.2 The STS must use standard connections to the computer running the control software (for example, USB, Ethernet, or similar connections).

Project Requirements

Project requirements are the remaining requirements which are not tied to specific performance values.

  • STSR 2.1 The STS must be well documented so as to meet the needs of open source spaceflight designers who will design and build future test stands (at Mach 30 and elsewhere).
  • STSR 2.2 The STS documentation and procedures must be complete enough that Mach 30 operators, students and educators who want to bring rocket engineering into the classroom, and anyone else interested in how rockets are tested can learn how to use it.
  • STSR 2.3 The STS documentation must cover the engine testing procedure from test stand setup, to running tests, and ending with stowing the test stand.
  • STSR 3.4 The STS shall be operated IAW the safety procedures which are outlined in Section 8 of the NAR testing manual.
  • STSR 4.3 The STS shall provide a fixed base on which to test model rocket motors.
    • STSR 4.3.1 The test stand will remain stationary during motor firings.
    • STSR 4.3.2 The test stand components will not experience undo vibration during motor firings.
  • STSR 7.1 All STS design documentation must be open and complete enough so that ANYONE, without necessarily a technical education in rocketry, propulsion, or engineering, would be able to build and operate the test stand.
  • STSR 8.1 The design of the STS must enable the completion of at least one operational test stand.
  • STSR 8.2 Whenever and wherever possible, considerations should be made so that the design of this STS can be used as a kit in the future.
  • STSR 9.1 The cost of the first operational STS must not exceed $200 excluding "consumables" and tools.
  • STSR 10.1 If at all possible, the STS should be completed within 3 months of formal launch as an exercise in agile design.
  • STSR 11.1 Disposal of the spent Estes motors should conform to all local, state, and federal guidelines.
  • STSR 11.2 Electronic waste items, including batteries and circuit boards, must also be disposed of according to all local, state, and federal guidelines.
  • STSR 11.3 If the frame of the STS is damaged beyond repair during operation, proper disposal/recycling guidelines must be followed for the materials used in its construction.
  • STSR 11.4 Wherever possible, the STS design should make it as easy as possible to replace components which are consumable or relatively easy to damage.

Future V2.0 Requirements

These are for reference only so that future features can be accommodated in the current design where practical.

Version 2.0:
  • STSR 5.1 High and low speed video capture of the tests from multiple angles.
  • STSR 5.2 Integrated ignition system so the test management software can control the entire test.
  • STSR 5.3 Additional measurements including:
    • STSR 5.3.1 The STS must meet the second part of the NAR testing manual requirement for casing temperature measurements and have a second thermocouple "3/4 of the way down the motor casing as measured from the nozzle end." 1
    • STSR 5.3.2 The STS must be able to record exhaust temperature vs time of Estes motors and transport that data to a laptop computer.
  • STSR 5.4 Higher resolution measurements.
Beyond Version 2.0 (Accommodation of):
  • STSR 5.5 High power commercial solid motors.
  • STSR 5.6 Small hybrid motors (on the thrust scale of high power commercial solid motors).
  • STSR 5.7 Larger thrust hybrid motors.
  • STSR 5.8 Small liquid engines.
  • STSR 5.9 Medium liquid engines.
  • STSR 5.10 Large liquid engines.


ADC - Analog to Digital Converter
consumables - Items that are used and then discarded, i.e. rocket motors.
IAW - In Accordance With
LSB - Least Significant Bit
NAR - National Association of Rocketry
STS - Shepard Test Stand
STSR - Shepard Test Stand Requirement

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