Full Mission Simulation Test Report

SloshSAT

University of Northern Colorado Team Members:

Sage AndorkaDan Welsh

Motoaki HondaMaurice Woods III

Zach Sears

5-12-2010

Due to acceleration of their containers, on board liquids manifest reactive forces on their containers that can have

adverse effects on the performance of the vehicle. 

However, understanding these reactive forces is limited and modeling is computationally intense.

 Our goal is to create a simpler analytical model to describe

liquid slosh. This simplified model, although not comprehensive, may yield practical results.

Mission Overview

Changes Since Subsystem Integration 

The only changes since SITR pertain to payload mass (added to meet necessary minimum mass requirements)[1] and modification of

the inner canister's end-cap design and adhesion method.  

The changes made only affect overall mission mass requirements, and alter the design and assembly method for the inner canister.

 This modification improves the canister's resistance to failure due to

the forces exerted on the canister, and eliminates the unwanted 'piston' effect that occurred during earlier tests.

Results are pending final subsystem tests.

Pictures

[1]Mass was increased to meet Wallops' minimum payload mass requirements by adding aluminum rings around the cylinders

PICS!

Test Description• Full Systems Testing has been delayed due to

small leaks found in our inner cylinder.  Further design review and testing is taking place to ensure proper function before full mission tests can be performed.

• However, through the development of more resilient and reliable cylinder designs, the following tests have been conducted:o Extensive pressure testso Temperature and environmental testingo These tests have confirmed that the new canister/end-cap

designs will endure the payloads flight, will be confidently self contained, and will not fail.

• Other (informal) tests include:o Center of mass test (not including testing with CSU)[2]o Spin testing: Successful

[2]Center of Mass test setup

Testing DescriptionWe determined that our canister manifested some small leaks

by the observation of fluid within the exterior cylinder and outside the interior cylinder.  The canister was dismantled and the inner cylinder was cooled in order to observe leaks (cooling

the canister helped emphasize the escaping liquid Galden, which would normally evaporate in a warm, open environment)

  Three pinhole leaks were observed along the junction between

the end-cap and the inner cylinder. We suspect that these leaks were caused by the heat generated by the heated needle tool that was used to cut notches in the canisters end caps[3]

to allow proper air flow around the canister, preventing the problematic 'piston effect'.

[3]Notches cut in the end caps (abandoned method) to allow top-to-bottom air flow within the containment cylinder, preventing the unwanted piston effect

Testing Description

A method of creating notches in the end caps which does not generate excessive heat (which may melt the glue holding the

end-cap to the cylinder) was determined and employed.

The canister was then put into a sealed jar and placed in a hot vehicle to increase the pressure inside the canister and force a

failure if one were to occur.

This second canister failed as well.  We suspect that an air bubble in the adhesive prevented a full seal of the canister. 

Due to the color of JB Weld, such air bubbles are undetectable when applying to the canister.

Testing DescriptionWe have now re-examined the adhesion method and overall design of our inner canister.  We have deemed that it may be necessary to change the material of the inner canister's end caps to one that will allow the use of

chemical welding of the end caps, to ensure proper sealing and structural integrity (i.e. resistance to heat and pressure failure).

This new angle on the design uses 'plugs' instead of end-caps to close the cylinder[4], thereby eliminating the need for modifications to compensate

for the piston effect.

This also improves the overall impact resistance of the inner canister, as the new plugs will be set snug into the ends of the cylinder and welded to the cylinder via chemical bond - essentially making it one piece of plastic

instead of three components glued together.

*Note: The exterior canister has not failed, and has, in all instances of inner canister failure, succeeded in acting as the redundant fluid containment system, as it was it's intended design.

[4]New, chemical welded fluid containment system (using plugs instead of end-caps)

New cylinder design with accelerometer

Testing Description

The individual subsystems not affected by the canister issues are all functioning properly.

Full systems testing and data analysis has not yet been completed due to the canister issues we have experienced, but

are expected to be completed shortly.

Again, some informal tests have been done throughout the building process, ensuring that few adjustments will need to be

made upon payload completion(these tests include center of mass, spin, and AVR/accelerometer/electronics functionality)

Overall Analysis

• Are you • ready• ready for launch?

o We are not yet ready to launch. o Come May 21st, we expect to be at launch readiness.

• Are you happy with the results?o Full testing success is expected and soon to come, provided

that the new subsystems designs and tests have proven successful.

o Great happiness is anticipated upon completion of full mission testing.

• What work still needs to be completed?o Full assembly of the cylinder and Galden containment systemo Full system integrationo "Life In The Day" / Full systems testing

 

Lessons Learned• "Get it done sooner" mentality has greatly benefitted the

team, and has proven necessary to this project. Considering the issues that are being encountered now, we are glad to find them sooner rather than later.

• Best practices? What has worked well?• Next time, it would be helpful to have created multiple,

usable versions of the payload design, so that when changes need to be made, the planning and assembly process has already been completed.

Conclusions• Issues and concerns?• New construction methods and step-by-step

"build and test, build and test" method is proving to be very productive, has improved production time, and is reducing the chance of critical failure.