saadzmirza
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- Joined
- Nov 12, 2013
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Yep... Hopefully will have an APRS beacon for recovery, no waiver (Class 1 and following 101.D balloons), spin stabilization with fin cant, insulated avbay, nozzle with enlarged exit cone for 25:1 pressure ratio (0.01 atm), Magnelite igniters for vacuum, and a little plug in the bottom of the motor nozzle to keep it pressurized, maybe clay or cork.
For recovery thinking confined BP charge.
Yep... Hopefully will have an APRS beacon for recovery, no waiver (Class 1 and following 101.D balloons), spin stabilization with fin cant, insulated avbay, nozzle with enlarged exit cone for 25:1 pressure ratio (0.01 atm), Magnelite igniters for vacuum, and a little plug in the bottom of the motor nozzle to keep it pressurized, maybe clay or cork.
For recovery thinking confined BP charge.
What are the benefits of a boosted dart? I thought it was mostly the mass loss, and also drag reduction...
Uh oh! Any suggestions? I really want to avoid spinning up a launch pad...
Openrocket says it will spin... but I question its accuracy over your experience. but, there should be SOME airflow by the time it hits Mach 3.5
Lugs:
You can have a pop lug, since you're doing 2 stage in a much thinner atmosphere, having 45 degree angle cut lugs (trapezoid shaped) or wire arches (like the ones on a paper clip) on the booster should be sufficient and more reliable. That or you can get or make a pop lug.
If you are worried about rod flexing, use a launch rail. There are different sizes, but since I'm not familiar with the conditions at launch altitude, I won't try to recommend anything. With rails, there are rail buttons, rail guides, and pop guides, which are like pop lugs but for a launch rail.
Commercial pop lug:
https://www.fliskits.com/products/components/misc.htm
(listed as PL001, Competition 2inch pop lug)
Weight:
If you into getting every tenth of a gram squeezed out, custom fiberglass tubes are the way to go. The problem is fragility comes with thin walls, and thin walls come from light tubes. Also, get the electronics and electronics bay light, no threaded steel rods, for example. Shroudlines are heavy. Most chute material is heavy. 1/4 mil Mylar and lots of sewing thread would work in theory, but would problably break in practice. Although the air could be thin enough that there isn't much drag from the drouge chute and the rocket slows down much more gently. Fillets are heavy, paint is heavy, etc.
Spinning:
Spinning up the rocket to a certain rate should produce roughly the same drag at different altitudes. What changes is the angle or size of the fins. Think about it this way: To spin up the rocket, you need passing air to impart its energy into the side of the fin. The energy pushing the fin sideways depends on how much air hits it, if the speed is constant. So by increasing the fin area or canting the fin to catch the same amount of air should mean that the same amount of air is also pulling it back, e.g. Drag.
I missed something, right? Mindsim can't do Navier Stokes, Mindsim can't calculate wake currents, Mindsim can't even solve algebra well.
Are you defining Mach as Mach at altitude or Mach at ground level?
You'll need a small hole in each section of the rocket somair pressure won't pop the tubes apart.
If if you have any questions, post them and I will make sure to take a guess and present it as fact. Make sure to check everything I tell you, since I'm not perfect and I'm not paying you if the rocket fails resulting from my data. Think of it as a research lead, or something similar.
Regarding the spin: I don't think it's desirable at all. One of the OP's goals stated a camera payload for capturing the event. Spinning the rocket up to a conservative 30 rev/s will degrade the footage from the camera package and it sounds like he doesn't have the weight to add in a despin for that section.
Regarding the lugs/rails/tower: This rocket has to endure a balloon flight to at least 80k. Have you calculated the expected forces that the ride will put on the lugs/rail buttons if you use them? My intuition says you would be far better off tower launching. It's a little extra weight for the balloon but it eliminates most of the carry risk. You will want to run the numbers to be sure.
Regarding a launch tower, that WOULD be ideal... but the FAA only allows a 6lb payload total under the balloon. We're awfully close right now - with a 6 ft carbon fiber rod. I imagine a rail, or a tower (could be constructed with 3 of the rods) would put us over.
Check out this launch some Stanford students did:
[video=youtube;H-AcSucRBbw]https://www.youtube.com/watch?v=H-AcSucRBbw[/video]
I don't think they used any spin, or even a rod/rail - and from the looks of it, it didn't seem to fly very straight.
They definite could've, but it was a proof-of-concept.
I think that their fins were also too small.
@Incongruent
But all of that is irrelevant - we talked to the FAA Office of Commercial Space Transportation and the Air Traffic Organization - the federal ones. The local FSDO office didn't want to deal with us. We now need to be approved, even though it's a Class I rocket. And the coordinator said 'of 12 rockoon proposals, I'm proud to say that I've never approved one.'
In other news, I'm now building my L1 cert. It's a LOC IV. I'll probably use a CTI 38mm 1 grain to make sure it doesn't get too high.
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