The 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 booster which will need to be developed. Plans for a new 20kNs, 110mm OD, monolithic grain design APCP motor are in the works.
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- Rocket – Fine tuned design based on GIGA II, glass fiber airframe, true minimum diameter, experimental rocket.
- Diameter – 86mm.
- Length – <2300mm*.
- Weight fully loaded – * kg.
- Apogee: 15+ km*
- Maximum velocity: Mach 2,5-3,0*.
- Sustainer Motor – experimental KILO moonburner “lite” motor (86mm).
- Propellant: Slow White (77,5% solids).
- Total impulse: approx 10.500*Ns.
- Isp: approx 205s.
- Burn time: 8*s.
- Propellant mass: 5,27*kg.
- Equivalent to a baby N1300.
- Flight control – RDAS Tiny.
- Onboard camera – Mobius mini.
- Tracking – Talky GPS, 1 Watt by LD; 433mHz AM emergency beacon.
Note: * – to be updated according to as-built values
- Successfully fly the GIGA III as a sustainer in a 2-stage rocket configuration.
Develop a monolithic, “moon burner” APCP motor.Motor tested but asymmetric thrust could be seen hence abandoned
- Reduce the weight of the rocket with at least two kg.
- Redesign and successfully recover the rocket with a single break point, single stage recovery.
Expected: Flights of Experimental Rockets (LRE) / Drawsko Pomorskie, April 2019.
Design & Construction
KISS design – Form Follows Material, the non-optimised rocket geometry follows from matching, readily available materials.
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.
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.
Currently the KILO 5GXL motor on a Slow White reload, as flown on GIGA II, is foreseen.
Abondaned Sustainer Motor design
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.
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).
Single stage recovery by means of ballute or 15-18″ Fruity Chute deployed at apogee.