Spectre II
Part 4, 13 January, 2005
By Mark Uitendaal and Leon Krancher
- Spectre II, part 1, 30 June, 2004
- Spectre II, part 2, 7 July, 2004
- Spectre II, part 3, 22 October, 2004
- Spectre II, part 5, 9 June, 2005
- Spectre II, part 6, 23 September, 2005
- Spectre II, part 7, 2 January, 2006
- Spectre II, part 8, 15 April, 2006
Disclaimer: all liability waved! The contents of this page is presented for informational purposes only. Do not try to recreate any experiments presented in this page. The NAVRO and the author of this article cannot assume responsibility for any use readers make of this information. In The Netherlands it is forbidden by law to own this type of propellant if you do not have an exemption of the "Wet Explosieven Civiel Gebruik" (WECG).
After a very busy period, we have continued the constructions of the airframe. First, the fins were attached to the motor tube. In order to align it properly on the centre line of the rocket we have used a marriage jig.
Marriage jig.
Benjamin Wilkosz has carefully turned a retainer on his lathe. He did a tremendously good job! The retainer is based on a snap ring and has exactly the right diameter to attach it to our motor tube. We have attached it to the motor tube via 24 hour epoxy.
Retainer.
The camera hatch is also ready. It is laminated in glass fibre/epoxy.
Camera hatch.
The hatch is placed over the hatch gap. This gap is made in the lower fuselage. To make it possible to pull some electrical wiring from the power supply to the camera, we have glued an aquarium hose in de lower fuselage.
Hatch gap.
Top end.
The nose cone is made from glass fibre/epoxy. The faring was ordered by Caveman Rocketry. This product was modified by us and will be connected with PVC using 24 hour epoxy.
The glass fibre faring is transparent for radio waves, so this is ideal for the housing of our 10 mW localizer transmitter.
Nose cone.
The transmitter must be accessible through the back end of the nose cone. In order to do this, we attached a ring in the back end of the nose cone.
Nose cone.
The lower fuselage with camera hatch will ultimately look like this.
Lower fuselage.
The outside of our electronics canister is also produced. The inside of it is still under construction, but a picture of the uncompleted product can also be seen.
Electronics canister.
Electronics.
A friend of ours, Floris, sewed the shock cord on a professional sewing machine. The tubular nylon we have used is rated 25 KN, that's more than 2,5 metric tons!
Kevlar shock cord with kevlar flame shielding.
Before laminating the fins, we have sanded the fins to achieve the best possible product.
Sanded fins.
Laminated fins.
Close up of the laminated fins.
The finished fuselage.
The retainer.
A test was done with the nylon shear bolts. This was done by a special test stand with 1.5 grams of black powder.
Shear bolt.
The shear bolt ejection test stand.
The bulkhead after the test.
The test was a complete success! With 1.5 grams of black powder we can easily shear two shear bolts. The shear bolts can resist a static shear of 250 N, so this is enough to withstand the aerodynamic and inertial forces during the flight.
We have also conducted a motor test. This wasn't such a success. So we will have to come up with an altered motor design.
The moulds in which the propellant is poured.
A grain.
The motor was put in a hole in the ground and after several safety checks it was lit. Probably a second after the motor roared to life the motor exploded.
The motor in a field.
The remains of the nozzle were discovered after some intense searching.
Parts of the nozzle.
The altered design will look like below and we are currently in the stages of planning another test.
PVC 75mm K-motor concept
The altered design will have better nozzle retaining properties. A kind of "C" ring is glued inside, and also some shear bolts are incorporated in the design, to prevent the nozzle from sliding.
Nozzle retainer.
Next part: Spectre II, part 5, 9 June, 2005
