{"id":1484,"date":"2018-11-22T21:58:20","date_gmt":"2018-11-22T11:58:20","guid":{"rendered":"http:\/\/leederville.net\/rocket\/?p=1484"},"modified":"2018-11-22T22:00:37","modified_gmt":"2018-11-22T12:00:37","slug":"performing-ejection-tests","status":"publish","type":"post","link":"https:\/\/leederville.net\/rocket\/index.php\/2018\/11\/22\/performing-ejection-tests\/","title":{"rendered":"Performing Ejection Tests"},"content":{"rendered":"

38mm CTI and AeroPak motors come buy default with approx 1.4 grams of Black Powder for their ejection charges. Based on this and the fact my rocket has half of volume blocked off by engine block, I decided to start my ejection charge tests at 0.75 grams. Ultimately I got up to 1.76 grams of BP. This post discusses this in detail.<\/p>\n

 <\/p>\n

How the system is packed.<\/h2>\n

This is probably the best place to describe how the recovery system was packed, because the tests identified a possible issue with the set-up.<\/p>\n

\"View<\/a>
View of all the components to be packed into air-frame – prior to folding and attaching igniters, cable cutter.<\/figcaption><\/figure>\n

You will notice in this photo there are TWO Nomex blankets. The left one\u00a0 covers the shock-cord (but its primary purpose is add additional drag) and the other Nomex blank protects the parachute. The right Nomex blanket is held in place with a Cable Cutter, the right is simply wrapped into a bundle.<\/p>\n

The parachute is on a Swivel and uses a 4mm Quick-Link. The Shock-cord is 5 metres in length, with 0.5 meters inside the air-frame. Notice the use of Z-Folds.<\/p>\n

 <\/p>\n

 <\/p>\n

How the Parachute is folded<\/h2>\n

Here are some photos of how it was folded.<\/p>\n

\"Making<\/a>
Making sure parachute has no damage and shroud lines are not tangled.<\/figcaption><\/figure>\n
\"Laying<\/a>
Laying out the parachute, shroud lines taut.<\/figcaption><\/figure>\n

 <\/p>\n

\"Making<\/a>
Making sure all the parachute gores are equally aligned and neat.<\/figcaption><\/figure>\n
\"Ensuring<\/a>
Ensuring all gores are split evenly on each side of the shroud lines.<\/figcaption><\/figure>\n
\"Putting<\/a>
Putting most of shroud lines about 3\/4 up the parachute skirt.<\/figcaption><\/figure>\n
\"Folding<\/a>
Folding bottom “third” up….and then top third down.<\/figcaption><\/figure>\n
\"Folding<\/a>
Folding over again.<\/figcaption><\/figure>\n
\"z-folding<\/a>
z-folding into three.<\/figcaption><\/figure>\n

 <\/p>\n

Protecting Parachute with Nomex Blanket<\/h3>\n
\"Place<\/a>
Place bundle in the centre of the Nomex blanket, with the shroud lines pointing to the right. Make sure the quick link is just outside the bundle.<\/figcaption><\/figure>\n

 <\/p>\n

\"Pardon<\/a>
Pardon for lack of focus. Fold from RHS to about 1\/3 way left.<\/figcaption><\/figure>\n
\"Fold<\/a>
Fold bottom up<\/figcaption><\/figure>\n
\"Fold<\/a>
Fold Left piece to the right. The tightly role up.<\/figcaption><\/figure>\n
\"Place<\/a>
Place the Cable Cutter\/cable Tie around it. Make sure the screw\/end is at shroud end.<\/figcaption><\/figure>\n

I made double sure that the parachute was attached to the shock-cord and the quick link was taped up.<\/p>\n

Loading the recovery systems into the Air-frame.<\/h2>\n

Here are some photos of how I did it.<\/p>\n

\"3rd<\/a>
3rd test: Checking that there is chance of cable cutter migrating further away from the nose cone.<\/figcaption><\/figure>\n
\"3rd<\/a>
3rd Test: Measuring length of igniter for Black Powder Charge well. Should be about 27cm.<\/figcaption><\/figure>\n
\"Determining<\/a>
Determining any potential issues with igniters\/charge well\/shock cord.<\/figcaption><\/figure>\n
\"3rd<\/a>
3rd Test: Tape igniter cable to shock cord, at two points with painting tape. Just trying to keep things orderly.<\/figcaption><\/figure>\n
\"3rd<\/a>
3rd Test: Packing parachute bundle into air-frame.<\/figcaption><\/figure>\n

 <\/p>\n

Results of the Ejection Test<\/h2>\n

After the test we observed:-<\/p>\n

    \n
  • No tangles. Great!<\/li>\n
  • One of the Z-folds opened up, two left to open up (This is good). The reason this is good is because we expect the load to be “fairly” significant when the parachute inflates and these Z-folds will help reduce load on the rocket components.<\/li>\n
  • There was no damage to any component (though the charge well is showing some wear after three tests. It is still in good enough condition for use in launches.<\/li>\n
  • The Cable Cutter still attached to the parachute<\/li>\n
  • The e-match wiring in-tact<\/li>\n<\/ul>\n

     <\/p>\n

    Here are some photos and a movie.<\/p>\n

     <\/p>\n