DEMOSAT TESTING
PROCEDURES
DemoSat team members preparing for drop test
Summer 2011
Author: Caleb Ogg
Revision 1.2
These testing recommendations are a result of many years of DemoSat
testing and are designed to help uncover failures modes commonly seen
during DemoSat flights. Some tests are required and others are
recommended. These test start during the Preliminary Design Phase and
conclude with testing required in the days before launch.
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PHASE ONE TESTING: STRUCTURAL
The first set of tests is designed to measure the payload’s structural integrity. No electronics are
required (or encouraged) for these tests. Components should be replaced with foam or plastic mock-ups of
equal dimensions and mass. By accurately loading the structure, the most meaningful results may be
obtained. If very accurate mock-ups are used, this will also provide an opportunity to plan a well-balanced
layout through experimentation. This test should also provide perspective on possible integration issues
and wiring needs. Typically this is completed after PDR and before CDR.
Preliminary Whip Test
Purpose
Procedure
To prove the payload is secured to the flight string.
1. Attach the weighted payload to flight string
 Thread a two meter piece of flight string through the flight tube.
 Secure on both ends with paper clips (make sure paper clips are snug against
washers).
2. Begin spinning the payload above your head, slowly building speed. Continue to
swing payload for about 30 seconds (40-50 RPM).
3. Transition to more chaotic motion. Whip/jerk the flight string to simulate worst case
accelerations.
4. Inspect paper clips and flight tube afterwards and internal structure for damage or
stress.
A properly secured payload should remain on the flight string for the duration of the
test. The flight tube and paper clips should look the same as before the test (no
movement).
Electrical components are simulated with weighted foam mock-ups.
Must make sure testing area is free of bystanders. Performing test over grass will
minimize payload damage if it comes unattached.
High; all teams should complete a preliminary whip test to address structural issues early
on.
Expectations
Limitations
Safety
Applicability
Drop Test
Purpose
Procedure
Expectations
Limitations
Safety
Applicability
s df
To verify the payload’s structural integrity in a worst-case impact.
1. Assemble payload structure.
2. Weight payload with component mock-ups. Seal payload with hot glue and
aluminum tape.
3. Drop payload from 20 feet onto concrete.
4. Open payload and inspect damage.
Foam core/insulation exterior should remain intact. Splitting or tearing near the
impact region is common. All component mock-ups should remain inside the
payload.
Electrical components are simulated with weighted foam mock-ups.
Must make sure testing area is free of bystanders.
Required; all teams must complete a drop test.
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PHASE TWO TESTING: ELECTRICAL AND SOFTWARE (Flat-Sat) TESTING
The electrical testing procedure is heavily dependent upon the specific components/subsystems
being flown. The main theme is data collection. For example, to test solar cells the necessary electronics
(solar cells, PCB, Arduino) were placed in direct sunlight for an hour. The data files were checked to see
that the system had been operating as anticipated. Typically this is completed after CDR before
complete system electrical and mechanical integration.
In a “Flat-Sat” Test, the entire electronics system is assembled and tested independent of the
structure. The electronics should be laid out on a table and electrically assembled.
Flat Sat Test (Data Collection)
Purpose
To check that the system is functioning prior to integration.
Procedure
1. Assemble components or subsystem.
2. Turn on system and complete a visual check.
3. Run assembled electrical system for an hour or more. The conditions and details of
the test are usually specific to each payload.
Expectations
A properly functioning system should return analyzable data.
Safety
There should be no considerable safety hazards; however it is important to monitor your
system for the duration of the test. Make sure to lay out your system on a stat-mat to
avoid damage by ESD (electrostatic discharge)
Applicability
Required
as
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PHASE THREE TESTING: ENVIRONMENTAL
These final tests are intended for the completed and fully assembled payload and should start 2
weeks before the flight. They serve as a final check of payload readiness by simulating flight conditions.
To prove the payload is secured to the flight string and to confirm the payload will operate as anticipated
during the flight as anticipated, specifically confirming workmanship including electrical connections.
The goal is to not damage the payload but so simulate the flight.
Cold Test
Purpose
Procedure
Limitations
Safety
Applicability
To ensure the payload remains operable through the Tropopause (local temperature
minimum).
1. Place functional (sealed) payload in climate chamber with 20 pounds of dry ice.
2. Monitor external (testing chamber) temperature using temperature sensor of a
multimeter. Verify that testing chamber achieves temperature around -55℉ or colder.
3. Remove payload after three or four hours. Open payload and examine internal
temperature data. Open all data files to check that the electronics continued to operate
as the payload cooled.
There were no observed limitations. This test exposes the payload to the coldest
temperatures it will encounter during flight, but for a much extended duration. It is a
worst-case scenario test.
Use gloves when handling dry ice.
High; it is crucial to check that the system won’t shut down during the intense cold of the
stratosphere.
Vacuum Test (where applicable)
Purpose
To test the effects of low pressure on the payload.
Procedure
1. Place functional (sealed) payload in prepped vacuum chamber. See vacuum chamber
guidelines for procedures.
2. Leave payload in vacuum chamber for at least an hour. Check pressure gauge to
ensure vacuum chamber achieves an acceptably low pressure.
3. Turn off pump. Open valves and let chamber reach equilibrium.
4. Remove payload and check data.
Limitations
There are no considerable limitations.
Safety
It is important to read the vacuum chamber user manual before operation.
Applicability Variable; it is particularly important for payloads carrying pressure sensitive items or
optical payloads concerned about outgassing.
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String-Up Test
Purpose
To check flight tube clearance. It is important that the payload may be easily attached in a
few minutes or less. A fully functional payload is useless if it cannot be secured to the
flight string.
Procedure
Limitations
Safety
Applicability
1) Assemble payload
2) Thread a section of flight string through the payload’s flight tube.
3) Secure flight string on either side of payload using paperclips. The flight string should
move freely through the tube when it is fed from one end to the other and it should take
no more than one minute to string. Inspection of the tube should reveal no possible
abrasion points. The paperclips should not interfere with the flight string.
There are no limitations.
No considerable safety hazards.
Required
Expectations A properly secured payload should remain on the flight string for the duration of the
test. The flight tube and paper clips should look the same as before the test (no movement).
Limitations Electrical components are simulated with weighted foam mock-ups.
Safety
Must make sure testing area is free of bystanders. Performing test over grass will minimize
payload damage if it comes unattached.
Applicability High; all teams should complete a preliminary whip test to address structural issues early on.
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Shake Test
Purpose
Procedure
Limitations
Safety
Applicability
Verify the (mechanical) integrity of the electrical connections and component mounts.
1) Seal functioning/integrated payload using aluminum tape.
2) Shake payload 60 seconds. Try to make the shaking as random and varied as possible.
The point of the shaking is to loosen any potentially weak electrical connections so they
may be improved prior to flight.
3) Carefully open payload and examine the system, looking for broken connections and
checking for functionality.
There are no significant limitations. While the test does not replicate the external forces
that will act on the payload during flight exactly, it simulates a worst case scenario in
which electrical connections could potentially loosen or break.
No considerable safety hazards. Make sure to have a firm grip on the payload before
shaking.
High
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Functionality Test (Data Collection)
Purpose
To run a full flight simulation with your assembled/integrated payload. To ensure mission
success by checking that the system will function for the expected duration of the flight.
(A typical flight lasts around two and half hours; 90 minutes for ascent and 45-60
minutes on descent)
Procedure
Procedure
1. Integrate payload and complete visual check
2. Run system for two and a half hours.
3. Analyze the data.
Expectations A properly functioning system should return analyzable data. Check that the system
collected data for the duration of the test. Also check that the data agrees with the
anticipated results.
Limitations
There are no significant limitations.
Safety
There are no considerable safety hazards; however it is important to monitor your
payload for the duration of the test.
Applicability Required
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Tips for a Successful Mission
I) External Indicators: During integration it is very easy to check the completed systems functionality.
However, once the payload is sealed this becomes a much more difficult task. Many teams in the past
have used LEDs (secured to the payload exterior) to indicate the system’s status. This technique is
highly recommended. It allows the team to launch the payload, confident of its operation.
II) Integration Procedure: It is essential to develop a procedure prior to integration. A well-written
procedure should lay out the order in which components are installed as well as a brief description of
installation. A good integration procedure will minimize clutter within the payload; making accessing
and servicing the system much easier.
III) Electronics Staking: Electrical connections (rather than structural) are often the first to fail during the
intense vibration of flight. It is crucial that the electrical connections are further secured using a glue
or epoxy. This process is referred to as “staking” electronics. While there are many expensive staking
compounds available, hot glue is adequate and affordable. Similarly, if any components have buttons
or switches it is important to secure them in the “activated” or “on” position. The vibration of flight
can flip these switches, prematurely shutting down the system.
IV) Wire Routing: When wiring the electronics it is a good idea to leave wires longer than originally
expected. This eliminates tension in wires, which is one of the main causes of failure for electrical
connections. Having excess wire also allows a redesign or modification of the layout without having
to rewire the components. Remember, it is much easier to secure excess wire than it is to make wires
longer.
V) Layout: There are multiple factors to consider while designing the payload’s layout. The first is the
center of gravity requirement, which states that the payload must be balanced about the flight tube.
The second consideration is payload servicing. For example, if you have a battery or SD card that will
need repeated replacing after testing (and before flight) it would be wise to put this near the panel that
opens, for ease of accessibility.
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