DECA V – Two-Stage

Rocket outline

Rocket – Two stage rocket

Motors – DECA 8 grain KNDX & Cesaroni 54mm J1055 Vmax – 2G

Booster – Newly constructed similar to the DECA IV fin can method –  with enlarged fins to allow for a high static stability margin upon lift off.

Separation – By ignition of the second stage.

Recovery Sustainer – Design as per DECA IV.

Recovery Booster – motor delay set at 7s.

Payload – IMU, I-AM and Beeline GPS tracker into nosecone and #11 HD camera looking down

Documentation – Full NERO RSDS, parachute simulation sheet, SolidRocketMotor file & RockSim file.

Diameter: 58mm

Length: 2446mm

Weight fully loaded as-built: 6476gr of which was 1153gr propellant

Cd derrived from flight data: xxx

Motor: DECA 8 grain KNDX. Total impuls & Isp from flight data: xxxNs. Isp xxx,xs

Goals

  • Fly in a two stage configuration to ± 3,4km.
  • Use head end ignition on the DECA 8 grain KNDX motor
  • Separate sustainer from booster by sustainer motor ignition.
  • Use a Cesaroni  54mm 3G casing with spacer on a Cesaroni J1055 Vmax reload (2G) and use the motor delay to recovery the booster.

Flight 1 DECA V two stage – Friday 26.04.2013

 On Friday 26.04.2013 we woke up and the fog was hard to miss from our hotel window. Temperatures plummeted from comfortable 16-18° C to 7-9° Celsius with a 4-7m/s wind blowing from the North. On top of that it never stopped drizzling throughout the day and the rain ranged from a drizzle to a hefty shower. The weather reminded us of an unfavorable launch in 2004. Clouds were estimated to be at 200m. With only a few active flyers on the NERO side we had some trouble with erecting the tower to the rather unusual 20° azimuth. Lessons learned: set up the launch rail on Thursday and focus on flying rockets on Friday.

DECA V – By that time a fellow NERO rocketeer LD decided not to risk his 3+km rocket and did not fly. Quite understandable when seeing the extensive Arduino payload in the nosecone. The same risks could be opted about the DECA V two stage with a simulated apogee of 3,4km. However with a Beeline GPS in the nose cone and a GSM GPS tracker attached to the shock cord and no experimental launch day scheduled within the coming moths I decided to fly the two stage rocket anyway. Eventough only the first 200m could be witnessed. Rocket prep was easy, the GPS trackers were confirmed to function and within the hour the DECA V was sitting in the launch rail. One problem popped up which would later be the cause of flight anomaly. Because of the rain the plastic nosecone became wet. Normally the payload module is activated though the nosecone end after which the nosecone is put on and secured by aluminium tape. This had worked flawless during the last 4 launchs however this time the tape holding the nosecone to the airframe would not stick due to the rain. A quick fix was deemed to be found when the aluminium tape was exchanged for duct tape. After the launch area was cleared the recovery and sustainer ignition electronics were powered on & armed (quite a tense moment with the sustainer motor being a mere 30cm away). But the reliable RDAS Tiny functioned just fine. Secondly the Cesaroni igniter was inserted into the J-1055 Vmax and the DECA V two stage was ready for launch at 12:45.

After a quick count down the Cesaroni Vmax hauled the two stage rocket quickly out of the rail into a straight and stable ascent, quickly disappearing into the clouds. The seconds were counted down and right on que (considering the 3s coast delay and 2 additional seconds for distance to be covered at the speed of sound) the sustainer came up to full pressure. With a muffled sound and absolutely no visual confirmation the sustainer was thought to be on its way to 3,4km. However, only seconds into the flight we stopped receiving the Beeline GPS coordinates (later the cause was tracked to the nosecone separating from the airframe and taking along the antenna and half of the Beeline GPS) and about a minute into the flight the rocket was spotted under parachute at an unlikely angle from the launch rail. This made recovery of the sustainer easy but straight away stopwatches were checked as the rocket landed way too soon. But nobody knew what happened because of the clouds. Landing location of the sustainer as sent by the GSM GPS: 52.395768 005.922133. While writing this report the booster is still misplaced and has yet to be found. Recovery of the booster should have been simple trusting on the Cesaroni motor ejection set at 7-8s with the recovery harness consisting of Kevlar and the parachute wrapped in a Kevlar burrito. Nobody saw it landing.

Onboard video of the DECA V two stage flight also capturing the booster separation by sustainer ignition: 

After analyzing the onboard camera footage and extracting still images from the video with Quicktime it was discovered that just before or at sustainer burn out the nose cone separated from the rocket sending it into and unstable flight with lots of spin. The spin and curved trajectory likely being cause by a previous camera hole looking out the airframe now serving as a jet exhaust with 300m/s air rushing in from the top where the nose cone normally would be. A video still of the nosecone & Beeline GPS antenna fly by at the left of the rocket can be found below.

Landing spot DECA V:

The DECA V reached an  altitude of 1310m at a peak velocity of 1050 km/h.  

Conclusion

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Post flight analysis – by BO

  • ***

Design & Construction

Sustainer:

Mass sustainer ready: 4877gr.

DECA IV – same configuration as the single stage flight of 2012.

Sustainer Motor – DECA 8 graing KNDX:

Actual stack length (8grains)= 551mm. Length motor chamber 570mm; liner length 56xmm; clearance 1mm.

Average coating on the grains (pinch of NC lacquer combined with isopropanol and finely ground commercial BP: near nozzle, six grains only ends coated with 0.3gr BP / grain. Two grains near forward closure painted all surfaces  0,5-0,6gr BP / grain. Total BP coating 2.9gr.

Average grain length: 63,8mm. Average grain density (actual/ideal): 98%. Average grain mass: 144,1 gr. Core diameter 20,5mm.

Igniter: 5,0gr (2,5gr commercial 3F BP + 2,5gr of magnesium.

Sustainer igniter hooked up to RDAS Tiny Igniter 3 output being brown wire. Set at: 3s.

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Sustainer Recovery

Main parachute 800mm diameter + 1m tubular kevlar with end spliced for connection to d-shackle. 5m  tubular kevlar with both ends spliced for d-shackle. Payload with M6 eye bolt for connection to d-shackle. Burrito style parachute bag. Kevlar cloth 350 x 235mm. Length = spare (60mm) + length parachute (150mm) +GPS tracker (70mm) + overlap (70mm) = 350mm. Width = 1,5 · π · ID tube = 255mm.

Tumble free fall equals an (fictive) hemispherical parachute  of 0,45m diameter with Cd of 1,75.

Under parachute is an hemispherical parachute of 0,8m diameter with Cd of 1,8.

Above mentioned values are derived from the DECA IV descent actuals verified in flight I 09-10-2012:

  • Tumble free fall DECA IV rocket = 26,0m/s
  • Under parachute  = 12,4m/s.
  • Rocket mass =  3,740kg

A 2,0gram apogee straw charge was used – checked 16.03.2013

Booster:

  • Booster length = 580mm.
  • Booster mass incl motor retention hook, rail button & shock cord retention: 676gr
  • Recovery harness incl parachute & kevlar parachute protector: 42gr
  • Booster without motor but including, rail button, recovery harness & parachute: 715gr.
  • Booster fully loaded incl 2G Vmax in a 3G casing: 1599gr.

Booster Motor – Cesaroni Pro54-2G J1055 Vmax

  1. Motor length 3G = 320mm of which 10mm is rear closure.
  2. Casing 3G – 54mm – 232.6gr
  3. Rear closure – 44.4gr
  4. Case Spacer length = 85mm
  5. Case Spacer 58-60gr
  6. Unmodified forward closure: 82.9gr. After setting the delay 82,2gr.
  7. Set delay removal at max. in this case it indicates 9. So minus 9 sec. Actual depth hole in delay grain: 9,8mm
  8. Grain A (near nozzle): 180,0gr. Core 22,5
  9. Grain B (near forward closure): 180,1gr. Core 22,5
  10. 4,2mm between top grain and top of liner
  11. Motor reload mass 546gr.
  12. Motor loaded = 882gr (3G casing + spacer). Normal motor loaded: 772gr. ==> Extra weight penalty for 3G casing + space = 110gr.
  13. Gap closure and liner 1,1-1,3mm

[Show picture list]

Booster Recovery

Parachute 410mm diameter. Parachute rolled: length 60mm (4part zigzag), diameter 35mm, mass 20gr. 1,6m tubular kevlar (4mm) with both ends spliced for d-shackle. Burrito style parachute bag. Kevlar cloth 350 x 235mm. Length = overlap (70mm) + length parachute (60mm) + overlap (70mm) = 200mm. Width = 1,3 · π · ID tube (54mm) = 220mm.

2stage:

  • Mass 6476gr
  • Cg 2-stage @ 1550mm from tip

 

 

Payload

Payload built by BO and will contain:

  • RDAS Tiny
  • IMU
  • I-AM sensor package
  • Big Red Bee GPS tracker – mass 56,5gr
  • 640×480, 30fps – Turnigy camera – looking out

Rocket will further more contain:

  • 1280×720, 30fps – “#11 HD Key Chain camera” – looking down
  • real time mini GPS tracker

Assembled rocket & payload. Determined Cp & Cg. Static margin of 4,83 cal.

Notes

Length:

  • Parachute in tube 1/6: 200mm
  • Parachute in tube 1/4: 260mm
  • First stage kevlar shock cord: 100mm
  • GPS tracker: 65mm

Glass Body tube

  • OD = 57.8mm
  • ID = 54.6mm

Glass Coupler tube

  • OD  54.5mm
  • ID = 50.9mm

Machining the glass tube to length: While cutting the tube square on a lathe don’t go all the way and leave 0,4mm wall thickness remaining. Final cut by hand with sharp hobby knife. This to prevent glass fiber weave to catch up with cutting tool thereby causing delamination of inner layer of glass fiber.

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