GIGA III – Two stage

20190427_141101The GIGA II flew in April 2018 to 8.8km on a 10kNs APCP motor. This flight was considered a huge success and was a stepping stone for the next challenge: to fly the GIGA III rocket as a sustainer in a 2-stage rocket configuration. This flight will require a short burn / high thrust booster motor which will need to be developed.

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Rocket Outline

  • BOOSTAR-ONE / GIGA III 86mm sustainer, minimum diameter, experimental, two stage rocket.
    • Diameter – 90/86mm.
    • Length – 4030mm.
    • Weight fully loaded – 31.0kg.
    • Motors: LD 12 point star core XL / KILO 5GXL.
    • Apogee: +15km
    • Maximum velocity: 836m/s / Mach 2,68.

Sustainer: GIGA III

  • Rocket – Shortend design based on GIGA II, aluminium airframe, true minimum diameter, experimental rocket.
    • Diameter – 86mm.
    • Length – 2100mm.
    • Weight fully loaded – 14.5kg.
    • Apogee: +15+km
    • Maximum velocity: 836m/s / Mach 2,68.
  • Sustainer Motor – experimental KILO 5GXL “lite” motor (86mm) with head-end-ignition.
    • Propellant: Slow White (77,5% solids).
    • Total impulse: approx 10.500Ns.
    • Isp: approx 205s.
    • Burn time: 8s.
    • Propellant mass: 5,25kg.
    • Equivalent to a baby N1300.
  • Payload
    •  Flight control – RDAS Tiny.
    •  Onboard camera – Mobius mini.
    •  Tracking – Talky GPS, 1 Watt by LD; 433mHz AM emergency beacon.

Booster – BOOSTAR-ONE built by LD

  • Rocket – Booster built by LD, aluminium airframe, minimum diameter, experimental booster.
    • Diameter – 90mm.
    • Length – 1930mm.
    • Weight fully loaded – 16.5kg.
    • Apogee: 3.5km.
    • Maximum velocity: 395m/s*.
  • Booster Motor – experimental LD 12 point star core XL (90mm).
    • Propellant: 65/10 AP/Al with RIO (75,5% solids).
    • Total impulse: approx 14.600Ns.
    • Isp: approx 229s*.
    • Burn time: 4s.
    • Propellant mass: 6,38kg.
    • Equivalent to a N3650.
  • Payload
    •  Flight control – Stratologger*.
    •  Onboard camera – 2 pcs.
    •  Tracking – Talky GPS, 1 Watt by LD; 433mHz AM emergency beacon.

Note: * – to be updated according to as-built values

Goals

  • Successfully fly the GIGA III as a sustainer in a 2-stage rocket configuration.
  • Add head-end-ignition to the KILO 5GXL motor.
  • Develop a high thrust / short burn booster motor.
  • Develop a robust staging mechanism.

Flight

The BOOSTAR-ONE / GIGA III two stage rocket successfully flew to +15km and all parts were safely recovered during the Flights of Experimental Rockets (LRE) / Drawsko Pomorskie 27-04-2019 event.

Design & Construction

KISS design – Form Follows Material, the non-optimised rocket geometry follows from matching, readily available materials.

Compared to the GIGA II the following changes were implemented:

  • Airframe length reduced with 200mm in both the apogee shock cord section as the main parachute section.
  • Apogee shock cord changed into 25mm wide, 10m long kevlar strap. Instead of 3/8″ tubular kevlar.
  • Bolted retention of nozzle and forward closure changed from 12pcs M5 to 18pcs M4 bolts.

Booster Motor

KILO monolithic 12 point star XL – static test 1

20190203 - KILO 6 finocyl - FlameOn February 3rd we had a nice day of testing with blue skies, little wind and 6° Celsius. Two motors were to be tested both with the goal of having high thrust and short burns so they could be used as a booster for the forthcoming 2 stage rocket.

The first motor made by LD was a stretched monolithic 12 point star grain. Thanks to a different supplier a new, 1200mm long, phenolic liner is now available with the same dimensions as the PML 3" phenolic body tube which fits perfectly inside our 80mm ID motors. This motor contained a different formulation than the Slow White propellant. Now containing 65% AP, 10% Al with RIO as burn rate modifier and some additives like BDO and TETA for cross linking and bonding agent. The motor showed a clean  burn with little erosive burning, high thrust and short burn. By the looks of this we now have a superior booster for the forthcoming 2 stage launch.

 

 

Second motor was a full length PML phenolic liner, 6 fin true finocyl of which the construction photos and notes can be found here. This core shape consisted out a thin 6 fins around a central core AKA finocyl . Since erosive burning at start up was expected the motor was designed to burn progressively. Core Mass Flux (CMF) simmed at 1.7 lb/sec-in². I erroneously installed a 1000psi pressure transducer whereas normally I use the 2500psi version. So the pressure transducer maxed out at start up. However the load cell picked up the thrust spike at 7000N. Obviously this motor is not flight worthy but nonetheless a nice data set was obtained. For future finocyls it is not recommended to use thin long fins but shorter and wider fins as typically seen in large monolithic finocyls such as the Qu8k rocket.

I also tried a new ignition mix of 3gr BP, 6gr CuO/RIO/Mg thermite with 12gr of fine APCP shavings which resulted in a pressure spike of 55bar but no ignition. Clearly it is easier to light this APCP heavy on Al with a longer burning, pressureless ignition mix. The traditional thermite only igniter in some heat shrink, kindly provided by LD, together with some APCP shavings sprinkled into the motor saved the day and reliably lit the motor.


Sustainer Motor

Currently the KILO 5GXL motor on a Slow White reload, as flown on GIGA II, is foreseen.

KILO 5GXL - Head end ignition

Below is a quick representation of the head-end-ignition setup as used on the GIGA III rocket. There are many different configurations which work, including a more integrated, pyrotechnic, flame thrower type solution. However for the sake of robustness and proven designs I remained close to the modified NERO style M10x1 head end igniter body and the LD style heat shrink tubing thermite igniter.

Below


Avionics

The same avionics as flown in GIGA II.

Recovery

Two stage recovery by means of:

  1. Drogueless tumble recovery at apogee – 25mm wide 10m kevlar strap.
  2. 60″ Iris Fruity Chute as main parachute set to deploy at 300-500m.

Developments

Abandoned Sustainer Motor design

KILO monolithic moonburner – static test 1

On 20.09.2018 we tested 3 motors of which the monolithic moonburner was my own and a monolithic finned core / star grain was a joint venture with LD. The moonburner burn was succesful and the thrust curve spot on according to Bursim simulations. At the end of the burn there seems some off-center thrust. Upon post firing inspection it was noticed that the liner, even at its thickest point with 3 overlapping PML phenolic tube parts, did suffer a burn through although the casing seems to look untouched at the inside. Furthermore the 2mm thick HTPB inhibitor coating at the top of the grain resembled charred paper. Because of the liner burn through and off-center thrust I doubt this will make it as flight motor.

Specs / data:
  • Initial Kn: 295
  • Max Kn: 435
  • Action / burn time: 15.1 seconds
  • Fmax: 1880 N
  • Favg: 700 N
  • Isp: 209.1 s
  • Total impulse: 10.940 Ns
  • Destination: N700 - 3%

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KILO monolithic moonburner – liner

To cope with the extended exposure to hot gases due to the moonburner grain configuration I decided to apply additional phenolic protection on the inside of the liner. Rather than adding a full length casting tube I decided to cut the casting tube in two pieces and applied an additional layer of phenolic near the core of the moonburner and no extra liner protection on the opposite site.

  • The liner (3" PML phenolic airframe tube) and casting tube (3" PML phenolic coupler tube) were sanded from the inside with a honing device and 60grit sand paper taped to the stones. This worked surprisingly well.
  • The casting tube was indexed into 6 and marked on the outside for alignment.
  • The casting tube was cut to 897mm length so it is recessed in the liner approx. 9mm at both side corresponding with the nozzle and forward closure step(s).
  • This tube was then longitudinally cut in 2 pieces with table saw. A 240° and 120° piece or a 2/3 and 1/3 strips.
  • Both pieces were coated with a layer of HTPB on the outside. A 60gr batch of HTPB proved to be sufficient.
  • First the coated 240° piece was inserted into the liner at an angle (to prevent the HTPB to be scraped of) and secondly the 120° piece was inserted.
  • The casting base was wrapped in  food wrap and inserted into the liner to make sure the casting tube inserts were recessed at the correct distance.
  • Finally a 70mm OD aluminium rod was inserted to apply the necessary pressure and left to cure for 24 hours. Due to the casting base in place and a large overhang of the bar the pressure was not optimal at the casting base end. Next time make sure there is even pressure (no casting base in place, use a distance piece to position the inserts and keep the aluminium rod centered).


KILO monolithic moonburner - casting set up

This post is used as a repository. Pictures are pretty self explanatory.

Off set core 17,5mm.


Abandoned Booster Motor design

KILO monolithic 12 point star XL – static test 1

20190203 - KILO 6 finocyl - FlameOn February 3rd we had a nice day of testing with blue skies, little wind and 6° Celsius. Two motors were to be tested both with the goal of having high thrust and short burns so they could be used as a booster for the forthcoming 2 stage rocket.

The first motor made by LD was a stretched monolithic 12 point star grain. Thanks to a different supplier a new, 1200mm long, phenolic liner is now available with the same dimensions as the PML 3" phenolic body tube which fits perfectly inside our 80mm ID motors. This motor contained a different formulation than the Slow White propellant. Now containing 65% AP, 10% Al with RIO as burn rate modifier and some additives like BDO and TETA for cross linking and bonding agent. The motor showed a clean  burn with little erosive burning, high thrust and short burn. By the looks of this we now have a superior booster for the forthcoming 2 stage launch.

 

 

Second motor was a full length PML phenolic liner, 6 fin true finocyl of which the construction photos and notes can be found here. This core shape consisted out a thin 6 fins around a central core AKA finocyl . Since erosive burning at start up was expected the motor was designed to burn progressively. Core Mass Flux (CMF) simmed at 1.7 lb/sec-in². I erroneously installed a 1000psi pressure transducer whereas normally I use the 2500psi version. So the pressure transducer maxed out at start up. However the load cell picked up the thrust spike at 7000N. Obviously this motor is not flight worthy but nonetheless a nice data set was obtained. For future finocyls it is not recommended to use thin long fins but shorter and wider fins as typically seen in large monolithic finocyls such as the Qu8k rocket.

I also tried a new ignition mix of 3gr BP, 6gr CuO/RIO/Mg thermite with 12gr of fine APCP shavings which resulted in a pressure spike of 55bar but no ignition. Clearly it is easier to light this APCP heavy on Al with a longer burning, pressureless ignition mix. The traditional thermite only igniter in some heat shrink, kindly provided by LD, together with some APCP shavings sprinkled into the motor saved the day and reliably lit the motor.


KILO monolithic finocyl - static test 1

On September 20th, LD and JVDB static tested a joint monolithic motor project. JVDB provided the design, foam cores & motor hardware. LD developed the grain casting process, assembled the motor and provided the test stand. This motor was our first try at a monolithic grain motor with a complex foam core. We believe case bonded, monolithic grains are a requirement in case we wish to scale up our APCP motors. Hence we started with smaller 10-11kNs proof of concept motor cast in a PML 3" phenolic body tube mainly to investigate startup.

Core design:
The core design was gratefully provided by AV and duly copied by us. AV had tested the design with great results in an approx 20kNs motor. The shape can be considered a finocyl or a finned core. Below regression graphs, as copied from this great page about solid fuel regression, describes the difference between finned and slotted core regression. In the finned core design the propellant itself protect the casing from the hot gasses. We did experience quite some erosive burning at the beginning. This could be due to the Slow White propellant and / or the grain design. See below thrust curve picture with comments.