Level 3 Project - Into the Blue

I thought I'd share my experiences of attempting to gain Level 3 certification with either UKRA or Tripoli. The easiest way is to do this as a kind of online diary or blog, as I go along.
I'll be putting in links to pics, info, news etc., and will try to keep track of a total expenditure. Below you can find the 'blog', with the latest entry at the top, and each entry will link to all kinds of interesting resources.

More ideas and Hybrids


Can't believe it has been so long. Thought a bit more about the L3 rocket, and seriously considering making it capable of Contrail 98mm and/or 75mm Hybrid compatible too. In theory this should just be a longer 60" booster section (and probably larger chute). I will certainly make the top half at least capable of taking the longer booster, so I have the option of flying it with either booster.

Level 2


Finally got my Level 2 cert flight done at KLOB, after postponing it from UKRA and IRW. The cert flight was on a somewhat modified Rebel Pirate. The original was shipped with a 29mm MMT in a 4inch dia rocket, so I scrapped that, and replaced it with a 54mm KwikSwitch and a 38mm KS adapter. Flight was estimated to be about 5000ft, with ejection at apogee, and the rocket landed abou thalf mile away.
Didn't fly anything at ALRS, as the weather was so bad for most of the weekend. Hopefully next year is better!

Failure Modes Analysis


First up is Main parachute firing at apogee. If flown at Black Rock, this may not be the end of the world, as there is plenty of open drop-space. In the UK, however, with its annoying permanent stiff breeze and higher population density, this could be a real pain in the proverbial. Obviously the rocket needs to be designed such that the risk of main at apogee occurring is minimised, but given that over $1000 of investment will go into the rocket, an evaluation needs to be made as to the worst case drop range. Given that the UK also has cloud and haze, and that this rocket flight and recovery will be almost certainly invisible for the most part, a full evaluation of the potential drift range needs to be performed. This will make it much easier when attempting to recover with radio trackers.

Simulating my backup design first (6inch version), and setting the Main Chute to deploy at apogee suggests a drift range of 16500ft (=3.125miles). Launching at Pete's Farm, would mean landing way past the village. Launching at Folly Gate would be perfectly feasible if the wind is in the prevailing direction. Launching at Fairlie Moor is also perfectly feasible, assuming that it is FL245 there and Glasgow ATC can cooperate, and that the reservoir a few miles away is avoided. So with figures like that, BALLS and/or LDRS are possibly the best solutions.

Backup Solutions


My current L3 design has some pretty impressive performance figures, and also can only fly on motors which are potentially tricky to obtain. AP reloads are also pretty expensive when you start talking M class ($320+ for a baby M). So now is the time to start thinking about alternative designs using a more readily available motor, with less raw performance, that is also cheaper. The main criteria for the backup solution are:

1. Only the booster section will differ in basic design. This is to allow the original booster to be usable with the PL and recovery bay, but with smaller motors (tentatively 54mm K motors).
2. The booster section shall be able to accept both 75mm and 54mm motors. 98mm is optional.
3. If the booster is longer than 1m, then it shall be possible to split it in 2 for transport.

Now forgive me for not revealing the details, but I don't want monopolistic dealers snapping this one up as yet another UK exclusive distibutorship. This Hobby is already far too politically polarised, and I don't want to give those dealers ideas.
But to put you out of your misery/tease you further(*) here are some specs:
Diameter = 6inches, Max. Velocity = 300m/s, Max Acceleration = 15G, Max Altitude = 11,500ft
(*) Delete as applicable

Review of Part Manufacturers


I had a few concerns about some of the parts I had intended using, following on from a thread on a private forum. In particular the nosecone and airframe were in need of review, and possibly also the parachute.

Nosecone: I had seen many concerns about one dealer being a bit slack to deliver, and also a mix of both enthusiasm and discontent toward the quality of the products. I have a potential backup supplier, so if I am not impresed with the nosecone, then I have a spare for a future subsonic project.

Airframe: Still not sure whether to get a load of carbon-fibre to reinforce my already existing phenolic tubes, or to buy a set of filament wound glass tubes. Again there seems to be both discontent and enthusiasm for both, and this time on 2 different forums.

Parachute: It seems that the packing space required for a L3 chute capable of bringing a 10kg rocket down safely is a little more than I would have liked. At the moment, I think the best thing is to get the parachute and the recovery harness, and see how well I can get it to fit a 4inch tube. It may be that I have to go with 6inch after all, in which case this will swing my decision regarding the resolution of airframe concerns.

Recovery Electronics Configuration


It seems there could be some potential issues with using both an RDAS and Altacc in dual-redundant configuration. If the RDAS detects apogee first, and fires the drogue charge, then this can cause the Altacc to fire its Main! One reason is if the RDAS charge causes the Altacc charge to fire (eg due to poor isolation), then the Altacc detects a discontinuity on the e-match, and then does an emergency fire all of its charges. This is something that can be disabled by putting a 10ohm resistor across the drogue channel, but the other problem is potentially more serious, and affects all altimeters. The main deployment is based on barometric measurement, and this could possibly be upset by a pressure spike caused when the drogue charge fires. I will investigate using some thin foam over the vent hole to create some kind of damping or filter.

Initial Parameters


The first main issue about this rocket is that I want to be able to freight this rocket to BALLS etc. by plane. That implies it must be small and strong. Initially I am considering a 4inch rocket, with no section more than an inch or 2 longer than a standard 34in PML tube. So things like anti-zipper coupler poking out of the booster would be a bad thing, but having said that, I'll probably be making a shipping crate, so that is not critical.
Next up is the 'Rules of Thumb' for rocket design:
- L/D should be around 10-20 : 1
- Fin Root/Span/Chord should be approx 2D/D/D, where D = airframe diameter
- Chute diameter in feet should be approx 2 * SQRT (weight in pounds)
- Average Thrust : Weight should be > 5 : 1

I knocked together a very quick design in Rocksim, just to get a rough idea of the kind of performance to expect with a 4 inch dia. rocket which conforms loosely to the above rules of thumb. I'm initially planning on 2.5 PML tubes + nose cone, which exceeds the L:D by a foot, but that is nothing to worry about. Rocket mass will be around 10kg all in, so chute diameter is going to be of the order of 100-120in, and minimum average thrust needs to be > 500N, which fits in very well with an M motor! That very draft first iteration is suggesting a peak altitude in the region of 13000ft, and the rocket is below the optimal mass for maximum altitude. Maximum velocity is between mach 1.3 - 1.5, but simulations were all using the Rocksim defaults. This will need to be resimmed with proper weather conditions and accurate component masses etc. Follow the links for the Rocksim Design, and Altitude plots. Hit back in browser to return here.

Planning 2

February 2005

New PC has arrived, Rocksim et al installed, latest thrustcurves added. If you really interested, the spec is: AMD64 3500+ 90nm Winchester core, 1Gb Corsair CAS2 DualChannel DDR, 160Gb HDD, DVD+/-RW.
Next things to battle through are to create a basic spec and design for the rocket, so at least I have something to show when contacting TRA TAP members, and UKRA S+T.
Current concept is...
- Airframe = 4in PML reinforced with Aerosleeve, with option for identical design with 6in
- Motor Mount = PML 75mm
- Centering rings = 1/2" ply
- Fins = G10 TTW
- Nose cone = hand made glassfibre 5:1 Ogive
- Altimeter = RDAS + Altacc2C
- Motor = possibly Pro75 M1400

Planning 1

February 2005

Well I finally decided to actually get down to some real business. There is a lot to plan, especially as I need to arrange access to motor casing, order lots of parts, arrange L3 mentor to agree and sign things off etc., and all that is in addition to actually designing and building the rocket!
I have been collating all the data required for...
- UKRA/TRA paperwork
- Thrustcurves
- Casing sizes
- Suitable motor retainers


January 2005

On the Tripoli/UKRA L3 form, there is a box to fill in, which is entitled "What are the mission goals?". Duh! silly question!
OK, let's be serious. As I have no entries on the UKRA records table, now is the time to do something about it. So listed below are my mission goals...
1. To get a place on the UKRA record table
2. To exceed mach 1 (ca. 340m/s)
3. To exceed 15,000ft

Hmmm! Level 3

September 2004

A couple of things gave me this idea. Firstly was Cath and Marcus attempting (and Cath succeeding) their Level 3 at BALLS. Secondly was seeing a number of M motors fly at ALRS V in Switzerland. That, and my 100% score in the very long overdue UKRA L2 exam, made me realise that Level 3 is not out of reach on the technical side.
So I mulled things over and came up with a fairly simple dual-deployment design in my head (not really necessary for Black Rock, but the rocket would make a very good L2 one back home). Needless to say, the design would end up as a dual-deployment version of a cross between Cath and Marcus' L3 attempts. The plan would be to fly the L3 cert flight at either LDRS or BALLS in 2005.