2/28 Vacuum Chamber Piston Test

Vacuum Chamber Piston Test

Conducted by: Claire J, Tamara H

Location/Date: Blast Chamber/5:30-7:30pm, 2/28/2023

Safety Precautions:

• All participants must wear safety glasses.

• Range safety officer must audibly countdown before the test and ensure that everyone is paying attention.

• Test articles should not fragment into sharp, hard pieces during the test sequence.  This is ensured by eliminating any unfastened materials within the body sections, and limiting the amount of pyrotechnic charge used.

• The SO should inspect all test articles prior to initiating the piston test.

• Appropriate PPE will be used when installing the charge prior to the test (i.e. safety goggles and nitrile gloves). There will never be skin contact with the charge

• If a misfire occurs:  wait at least 60 seconds and disconnect the battery (or use an alternative method to disable the testing mechanism) before allowing anyone to approach the test article.

• Strict 25 foot keep-out zone must be established, which all test participants must obey. Members should ensure that no bystanders are present. The SO must ensure that no one is in the expected path of the projectile regardless of distance from the test articles. Mark of the test area (such as with caution tape) or otherwise guard entrances from bystanders.

• All debris must be cleared out of the blast chamber when the test is complete.

• Call MIT Police 617-253-1212 to report an emergency.

Goals:

• Evaluate the performance of black powder ignition for piston actuation at high altitude (low pressure)
• Validate the manufacturing and integration of our hardware components

Materials:

• Black powder (.2 g per firebolt)

• Piston

• 2 Firebolts (passed all testing)

• Piston T fitting

• 2 Brass NPT Plugs

• Gloves

• Alligator clips

• Weighboats and popsicle sticks

• Teflon tape

• bricks/weights

• Vacuum chamber & pump

• Safety glasses 

• Close toed shoes

• A very long wire

• 9V battery

• Scale

Check-offs:

• Fit check

• Reserve the blast chamber

Piston Integration Procedures: 

• Using a 1/4 inch torque wrench, ensure that the bolts holding the piston together are tight (100 inch-pounds of torque). If the bolts are loose, the piston will lose pressure as it extends. (torque wrench adapter in piston box)

• Integrate Firebolt into NPT Plug

• Use multimeter to check continuity of Firebolt (should be about 1.0-1.4 ohms) and twist the wires to short it. Two people should visually confirm that it is shorted. 

• Wrap the Firebolt with five wraps of Teflon tape. 

• Use the 7/16 wrench to screw firebolt into the NPT plug as far as possible. Highly recommend using the threaded brass plugs since it is threaded all the way.

• Repeat steps a through c for a second firebolt and plug

• Integrate black powder

• Everyone put on safety glasses. From now on, everyone within the vicinity of the pyrotechnics must wear safety glasses.

• Measure out 0.2 g of black powder and pour it into the other side of the plug, holding over a weigh boat to catch any fallout. This should be close to filling the plug and may overflow slightly if you screwed the firebolts all the way in. 

• Seal the opening by wrapping over the head and opening three times with Teflon tape. Make sure Teflon tape is flush on the inside.

• Repeat steps a through c for a second fully integrated plug

• Screw a fully integrated plug into the left side of the tee fitting (relative to the tee fitting orientated like a "T"). Tap the tee fitting several times and make sure no black powder falls out after screwing in the plug. If any black powder falls out, remove the plug and repeat the integration of black powder.

• Repeat step (4) for the second fully integrated plug, but screw it into the right side of the tee fitting (again relative to the tee fitting orientated like a "T")

• Compress the piston completely!

• Screw the entire fitting assembly into the piston NPT hole. Make sure that the fitting assembly is pointed up (in the direction of the bore) and rotate tee fitting until the side plug is as close to the body of the piston as possible.

• Test the piston by pulling up rod for 5 secs and checking that it is sealed

• Log Firebolts

Piston Testing Procedures:

• Perform integration according to the Piston Integration Procedures above.

• Run wires from outside to inside the blast chamber. Make sure that the wires are shorted on the outside of the blast chamber. On the inside, unshort the e-match leads and connect it to the wires.

• Place the piston in the vacuum chamber (firebolt-fitting assembly pointing down).

• Clamp the piston between two bricks. 

• Put the lid on the chamber and turn on the vacuum pump until pressure level reaches 0 psi. 

• Only after exiting the chamber and closing the door, perform a countdown and connect the outside wires to a voltage source (battery).

• In the event of a misfire, disconnect the battery and wait at least 60 seconds before allowing anyone to enter the chamber/approach the test article.

• After firing, wait at least 60 seconds before entering the blast chamber.