30 June, 2017

30 June, 2017.


MDRA trip was a resounding success.  The Jolly Logic Chute Release performed admirably.  We had 1 failure out of 5, but that was operator error –no fault of the unit.  I should have replaced the nonspec rubber bands after the first flight, but didn’t.  I used them in place of the OEM bands because even the small OEM band was too big for the BLS-15 on which it was being used.

Their recommendations for the bands are their small one for chutes up to 36″ or so in size, their larger band for larger than 36″ or so diameter chutes.  This may be a solid recommendation for most manufacturers, but Paramedichutes seem to pack a bit smaller than that.  We used the small band up to 48″ diameter without issue, and could probably do the BLS-60 in it as well.  We didn’t have one immediately available (nor an appropriately-sized rocket with us), but we’ll test that at another date.

As time permits, we’ll post photos of the packing techniques we used that seem to work for us.

Anyways… flight report:

Jolly Logic Altimeter Three data showing dual-deployment on a D-12 in a 1.6″ diameter airframe.

#1: Pemberton Technologies Kraken.   D-12-5.  Paramedichutes BLS-15.  Jolly Logic Altimeter Three and Chute Release @200′ (nonstandard bands).  Purpose of flight was to demonstrate Chute Release operation and achieve dual-deployment at low-power rocketry (LPR) levels  in the smallest recommended airframe for the Chute Release unit.  Apogee at 517 feet, descent to 200′ where chute was released.  Recovery weight was 0.441 lb.  Chute opened fully by 174 ft.  Landed 16 seconds later for descent rate of 10.875 ft/seconds.  Now we’d love to be able to say our chute has a Cd of ~2.5, but that’s just ridiculous.  There had to be a thermal or something it was riding.  We were expecting somewhere around a 14.5 ft/sec landing velocity.  Mission success.

#2: Pemberton Technologies Kraken.  E-22-6. Paramedichutes BLS-15.  Jolly Logic Altimeter Three and Chute release @200′. (same nonstandard bands).  Purpose of flight was to further explore dual-deployment in the LPR range with the larger LPR motors.  Apogee at 748 feet.  Nosecone separated from shock cord, carrying altimeter data with it.  Chute Release did not deploy properly due to use of nonstandard bands that were previously used.  Failure #1: failed to detect worn shock cord.  Failure #2: use of nonstandard bands.  Failure #3: failed to recognize loss of band elasticity, leading to slow opening of main.  Altimeter Three case and screen cracked upon landing.  Nosecone and rocket recovered with minimal damage (shock cord only)  Mission: failure.  Status: easily repairable.

Pem-Tech King Kraken recovering on a BLS-42.

#3: Pemberton Technologies King Kraken.  H-237SS-8.  Paramedichutes BLS-42(zp)  Jolly Logic Altimeter Three (damaged from previous flight, still able to record), Chute Release @ 300′.  Purpose of flight was to characterize ZP chutes and to serve as a benchmark for the next flight.  Unfortunately, I was called away from the pad to handle a developing situation and lost my place during prep work and neglected to start recording on the altimeter so no data was obtained on the flight profile with this particular chute.  The flight looked great, though, and the chute release worked well with the standard OEM small chute.  I don’t have a descent rate, but it was pretty slow.  Recovery weight was 3.28lb.  Mission: undetermined–no data.

Jolly Logic Altimeter Three data of the King Kraken flight on an experimental chute design.

#4: Pemberton Technologies King Kraken.  H-237-8.  Paramedichutes Experimental Chute Mark IX, 36″ diameter, zp).  Jolly Logic Altimeter Three (still damaged), Chute Release @300′.  Purpose of flight: to characterize ZP in this chute design, and compare descent rate vs. BLS 42 of identical material.   Apogee at 1412 feet.  Chute release at 300′.   Complete main inflation occurred at 35 seconds, 234 feet.  Landed 15 seconds later at an altitude of 3 feet, for a descent of 231 feet at 15.4 feet per second.  Cd is within expected range, however, oscillations were noted during descent that are normally absent with the standard chute material.  Venting should be sufficient to prevent this, but at this point it is unclear if it this may be a design flaw.   Mission is considered a partial success, given absence of comparative data.  Considerations: test again using standard material to compare vs. this flight.

#5:  Scratch-Built 4″ AIM-54c Phoenix.  I-243.  Paramedichutes BLS-48Featherweight Altimeters Raven 3, Jolly Logic Chute Release @ 400′.  Purpose of flight: 1: Confirm Raven 3 working.  2: Obtain base data for comparative future flight.  3: Straight liftoff to stop Bob’s razzing.

Raven 3 data of the Phoenix, recovering on a BLS-48.

Apogee at 1,480 feet.  Chute release @ 400′. Data suggests chute was released 309 feet (where one sees a corresponding 5.74 G spike, with approximately 2 seconds of elevated g-forces, as chute is released, lines extend, and main fully inflates). Chute is released at 29.6625 seconds. Inflation complete at 31.4325 seconds, 242 feet. Landed at an altitude of 5 feet at 45.8320 seconds, for a descent rate of 16.459 ft/sec, meaning the BLS 48 recovered the 6.283lb of weight at recovery with a Cd of 1.553–a nominal recovery.  Mission: success x3.  Bob conceded that it flew straight.

To be fair, Bob’s razzing was warranted: Phoenix models typically are vulnerable to making abrupt turns shortly after leaving the rail, and ours was no different in our initial shakedown flight.   Paramedichutes suggests keeping the end-of-rail speed on these models up above 65 feet per second or so.  So, if you have a Phoenix that tends to display such behavior, just remember that here, at least, in thrust we trust.  Consider stepping down your motor diameter and using a higher thrust motor of reasonable impulse for your field parameters.  See how it goes.

Looking forward to the next launch date!