Tuesday, March 16, 2010

Getting ready part N..

I've made my cat pack. I've built new tethers, the only thing left on my list is re zero the one vane I had to take apart and do final electronics checkout. In the next day or so I'll modify the software to match what I'm flying in simulation.

I'll probably leave for FAR Friday night and do a tethered flight very early Saturday. I've done a lot of simulations and a flight to the 1200 ft limit of G airspace. (1000 ft to give me some margin) and back to the pad is easily within the most pessimistic performance parameters. So if the tether flight goes without problems I'll make that attempt on Saturday.

Higher than that and I'll need FAA authorization to enter controlled airspace. (Which they are unlikely to grant me until I actually stop being lazy and formally ask for it. )

When I get that I'll try the flight to 11K ft and back to beat DCX. With out some aerodynamic drag on the way down it has ~3% margin. As a result I've ordered a parachute from Fruity Chutes (blue of course) and I will setup to deploy the drogue at apogee and basically fall back to 1200 ft or so before powering up to land. The purpose of the chute is to keep the vehicle upright and limit the speed to 60mph or so. This will either require a very calm day or compensation for winds aloft. I need to mdoel this. I can just use forecast winds, or I have to study the FAA rules to learn what I need to do to release a small balloon to measure the winds right before launch.
(A small Xbee transmitter and GPS cost less than $100 and is very light so I can actually fly a small instrumented balloon.)

Rough calculation says 11K ft to 1K ft at 60mph takes 113 seconds. So a 10mph wind would cause 1600 ft of displacement. I'll need to be very close on the wind calcs to land back on the pad. I might be better off to fly from the lake bed near FAR.

1 comment:

loyalj said...

The regulations for balloons in the US are pretty free and easy. Basically as long as your balloon payload is under 4lbs you're alllll right.

The FAA does like it when you notify them, but it's not required under that weight. That should be enough to get you one of the 3.7v mini-arduinos, an X-bee and a li-po to a decent altitude.

Kaymont's got one called the kci-1200 that gives you a total payload of 1050 grams. The next jump down is (an inconvenient) 250 grams total payload weight.