Search found 282 matches

by Andrew Burns
Wed Jun 27, 2012 8:56 am
Forum: Hybrid - Crossbreeding Rocketry
Topic: Micro-Hybrids
Replies: 246
Views: 59403

Re: Micro-Hybrids

My 16 gram microhybrid functions exactly the same as the 8 gram, everything is just scaled up. I used the same piercer dimensions as the 8 gram but made the injector bigger, the nozzle and fuel grain dimensions were also changed to meet the higher thrust level I wanted. My design uses threaded closu...
by Andrew Burns
Sun Jan 01, 2012 6:42 pm
Forum: Electronics
Topic: My CNC Lathe conversion
Replies: 101
Views: 20872

Re: My CNC Lathe conversion

Speaking of the micron fairy I can recall a customer at work complaining that they couldn't see the motor moving on a job I was doing, of course each move the motor made translated into a linear motion of 1 or 2 microns...
by Andrew Burns
Mon Nov 07, 2011 5:16 pm
Forum: Electronics
Topic: Going MAD
Replies: 147
Views: 33096

Re: Going MAD

Not even then PK, my microhybrid at WWW this year used a uMad as sole ejection system and I launched it off a 1/4" steel rod with no problems.
by Andrew Burns
Thu Oct 13, 2011 7:23 pm
Forum: Support & Recovery & Misc.
Topic: amount BP req'd for deployment?
Replies: 18
Views: 3759

Re: amount BP req'd for deployment?

The online calculator probably assumes that all of the BP goes completely into pressurising the tube and the nose cone doesn't come off. I'd assume if the body tube was perfectly sealed and the nose was glued on the tube would rupture (well before it got to 1000psi).
by Andrew Burns
Wed Oct 12, 2011 7:27 pm
Forum: Support & Recovery & Misc.
Topic: amount BP req'd for deployment?
Replies: 18
Views: 3759

Re: amount BP req'd for deployment?

In all my years of rocketry I've never seen one fail from too much BP, but I've seen plenty fail from too little BP. If you keep your recovery harnesses long and robust then a little more bang is just the sound a rocket makes when it thanks you for a good deployment.
by Andrew Burns
Fri Oct 07, 2011 8:56 pm
Forum: News & Events
Topic: Derek Devilles BALLS Flight
Replies: 14
Views: 1879

Re: Derek Devilles BALLS Flight

Once you get to those kinds of altitudes (100k feet+) the hard work really is done, air resistance is nearly non-existent due to the drop in air density so if you're carrying enough speed you'll just coast forever. In simulations I've seen predicted maximum altitudes increase completely out of propo...
by Andrew Burns
Fri Oct 07, 2011 7:40 pm
Forum: News & Events
Topic: Derek Devilles BALLS Flight
Replies: 14
Views: 1879

Re: Derek Devilles BALLS Flight

Yeah that's probably one of the best things I've ever seen...

Too bad they didn't get a GPS lock at max altitude, to my calibrated eye that was definitely over 100k feet.
by Andrew Burns
Fri Oct 07, 2011 5:25 pm
Forum: Hybrid - Crossbreeding Rocketry
Topic: Show us your hybrid
Replies: 83
Views: 15225

Re: Show us your hybrid

As has been mentioned, I've made a simple time-variant computer model of a self pressurised nitrous hybrid including (again simple) nitrous boiling and physical properties. After the case Strud mentioned I did several simulations of the same hybrid with initial nitrous temperatures from 15 to 32 deg...
by Andrew Burns
Thu Sep 29, 2011 8:40 pm
Forum: Higher, Faster, Further
Topic: Construction of a fin
Replies: 80
Views: 14598

Re: Discovery Science Fastest to 10,000' Race (LDRS30)

Andrew, So in theory, in a perfect world, in laminar flow (planar to the fin surface) this feedback should not occur. Would you tend to agree? No I don't think it would occur in laminar flow with no angle of attack to the fin however no rocket will ever have laminar flow with no angle of attack ove...
by Andrew Burns
Thu Sep 29, 2011 7:55 pm
Forum: Higher, Faster, Further
Topic: Construction of a fin
Replies: 80
Views: 14598

Re: Discovery Science Fastest to 10,000' Race (LDRS30)

As I understand it (which isn't very well) what Paul said is on the mark, gust of wind/disturbance cause an angle of attack on the fin which results in lift being generated. Because the lift force of a flat plate (and with any kind of aerofoil you'd find on a rocket) averages out to occur on the 1/4...
by Andrew Burns
Thu Sep 29, 2011 11:06 am
Forum: Higher, Faster, Further
Topic: Construction of a fin
Replies: 80
Views: 14598

Re: Discovery Science Fastest to 10,000' Race (LDRS30)

Also note that it's not stifness but resonance frequency that matters for flutter. You want the resonance frequency to be higher which means you want more stiffness and less mass. Therefore it may be better to insert a lightweight sandwich material into your fins than simply make them thicker out of...
by Andrew Burns
Mon Sep 26, 2011 6:16 am
Forum: How to's
Topic: Mandral jig
Replies: 73
Views: 22638

Re: Mandral jig

Here is a curious thing that I hoped that some of you clever scientific folks would have an explanation for... I rolled a glass tube this weekend, and this evening while peeling off the peel ply, I noticed faint blue flashes of light from the area being peeled. It doesn't look like static discharge...
by Andrew Burns
Fri Sep 23, 2011 5:56 pm
Forum: How's the Weather..?
Topic: Merit badges in rocketry
Replies: 25
Views: 3841

Re: Merit badges in rocketry

Dont get me wrong I am all for safety and knowledge just dont make it expected. I think at least safety should be expected :P I don't think people are trying to make rocketry a nerds club where you gain status through knowing things with this idea, it's more about giving new people (especially youn...
by Andrew Burns
Thu Sep 22, 2011 8:21 am
Forum: Higher, Faster, Further
Topic: Discovery Science Fastest to 10,000' Race (LDRS30)
Replies: 10
Views: 4640

Re: Discovery Science Fastest to 10,000' Race (LDRS30)

Yeah fin flutter is just a feedback system between aerodynamic oscilations of the fins and the structural stiffness of the fin. If the aerodynamic frequency of the fins matches to the structural resonance frequency of the fins or one of its harmonics you get destructive levels of oscilation. As flig...
by Andrew Burns
Thu Sep 22, 2011 6:10 am
Forum: Hybrid - Crossbreeding Rocketry
Topic: Project 50k
Replies: 30
Views: 6825

Re: Project 50k

but the ones that prepared this are associated with ASRI :D Well no offence but you have to admit that the Ausroc 2.5 project is a bit of a basket case these days. It's true that I'm talking from the outside looking in and if there's a lot of good stuff going on that I'm not seeing then I'd be very...

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