On 5/18/12 North Texas Near Space (NTNS-2) achieved a maximum altitude of 87959 ft over a sparsely populated section of North Texas. The flight was partially successful and full duration telemetry and camera data were recoverd.
• Vehicle departed from controlled flight, did not navigate to the landing site and was severely damaged
• Modified SW version 2.50 to utilize new AHRS code
• Modified Stinger 64 airframe
• Surface winds calm
• Trajectory was close to prediction
• Ascent was nominal
• Ascent terminated early on balloon failure at 88k ft. APM released on free fall indication and routed autopilot outputs to servos. Balloon not recommended since bursts at 86k and 88k on NTNS-1&2. 2# free lift.
• Higher than expected descent rate experienced and the plane spun down to ~17000 ft and began semi-controlled flight. The A/F managed to fly despite issues with the attitude reference and control saturation.
• Impact occured due to additional loss of reference. The roll autopilot was tracking commands.
• Maximum Mach number was about 0.5
• Minimum internal temperature was 48F.
• Airframe held up very well. One aileron horn was damaged (inconclusive considering the impact).
• Just Plain Strange: Almost crashed on my ranch. The airspeed probe is re-usable.
• Likely root case (s):
- dynamic pressure measurement low by 0.5
- gain scaling issues causing pitch and roll oscillations.
- pitch reference and finally roll reference is lost
- roll reference loss responsible for final dive
- contributing: agressive airspeed targets
• Todo:
- duplicate pitch oscillation with the stinger UAV; may need to duplicate A/S measurement issue in SW
- simulation reconstruction
- new A/F build, upgrades, noted SW changes (see spreadsheet), merge to 2.60 or latest stable build, gains
Comments
Update: I found a pinhole in the pitot dynamic proble. This could be crash damage, a manufacturing defect, or an assembly issue. Potenially significant to others is that I have tested both my DIYdrones AS probes and they both leak from the dynamic to the static port. i.e. when I apply pressure to the dynamic port and plug the end I get "some" gas expelled through the static port holes. I would like to get a set of the old probes, but the seem to be out of print on all of the websites that I've checked. Decided to roll my own here since it's not exactly hard.
Starting NTNS-2 flight reconstructions with the Stinger UAV today or tomorrow. The issue here is that the pitch inertia is lower than what was flown on the HAB flight. LG
I agree with you Monroe but, as Larry points out, being rule-bound doesn't guarantee safety and harmlessness. The focus on achieving the safest practicable outcome is in my opinion much more important than meeting regulatory requirements. Most of the time these two goals intersect, but we all know that in sometimes lawyers will demand guarantees of 100% safety, whilst crossing the street to the courthouse to make the demand...
We are never 100% within the law on a daily basis and so I believe that whilst we shouldn't set out to break the law, like da Vinci and other great scientists before us, we shouldn't necessarily let the last letter of the law impede a worthwhile experiment...
This thread is really mostly about the data. Not necessary, but completed was a range safety analysis that showed < 1X10-7 probabilities of a major issue with aircraft. I haven't done the work but I believe it much more likely to hit a buzzard on the way down below 1500 ft (by several orders of magnitude). What is a major risk are the batteries and the likelyhood of grassfires. This is a safety consideration that did not get mitigated that a lot of us are VERY sensitive to. Besides considerations mentioned above I will be considering some mitigation to include elimination of the LiPO cells that were flown last time.
Once I get back from the Ranch and have some BW I'll post updated plot and data.
passerby, I do hope you take as much care to ensure that the Canada Geese and similar are all filing for the appropriate clearances and waivers before they V1 and rotate for migration. I'm certain they've all been TSA cleared and have filed IFR flight plans too...
I was not trying to imply that the NAR is a ruling force for model rocketry... My statement was that even model rocket enthusiasts are aware of the regulations... and if you clicked on the link you would have seen that the url leads to a number of FAA rules that they follow when enjoying their hobbies..
It's only my goal to keep people informed here.. There are rules. But I suppose we'll leave it up to the FAA when they see this site and the activity posted..
I'm glad to see you file the waivers, etc. with the FAA.. That was my whole pont...
Thank you for agreeing with me that people should not just do this without considering the safety of others... It's all of our hobby, I'd hate to lose the right because someone didn't care and did something that ruins it for the rest of us..
Enjoy!
So, just out of curiosity.... Did you happen to have FAA clearance to do this? I think we all know it's a federal crime to pilot an RC or unmanned vehicle to altitudes above 400ft AGL... As far as I remember, anything above FL600 is specifically prohibited to anything other than military or NASA, etc..
As I'm both a pilot and a UAV/Drone enthusiast.... I beg you guys, don't screw this up for the rest of us... Of course, I'm assuming you did this without clearance...but it's that kind of stuff that forces them to make more rules to restrict us all... I love projects like this, but this isn't the wild west...there's rules and they are actually in place for a good reason........ I'd hate to run into someone's project and end up dead because they didn't make a simple phone call and file for clearance allowing the pilots in the area to avoid that airspace... I know, personally I would consider any RC vehicle in my path that wasn't cleared to be not only a dangerous threat to my life....but a threat to my rights since if the right people found out it was there, or someone runs into it... We can all expect sad consequences... Just as I try to stay out of military zones, ADIZ, or other airspace without permission in a real airplane...those rules apply to anything in the air...from 6 inches to 600 feet...
Some good guidlines to follow:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircul...
More:
http://www.faa.gov/about/office_org/headquarters_offices/ato/servic...
Here's an explanation of airspace classes...
http://en.wikipedia.org/wiki/Airspace_class_(United_States)
Some supplimental info:
http://en.wikipedia.org/wiki/Flight_level
Even model rocket enthusiasts are aware of these regulations and hopefully follow them...
http://www.nar.org/cabinet/waiverinst.html
The folowing link has video frame by frame from apogee + several other key frames where the autopilot was performing well. The orginal video was not completely recovered and video editing SW has some difficulty with frame count. This could be and issue later in the video when roll attitude and heading don't match up with telemetry for these frames. At the start of the video the attitudes seems at least plausable. I didn't include the raw magnetometer measurements on the video, but they are in the telemetry file. Note that I did update the original video with some altitude stamps. Still working on data, but thought I'd post the video. The attitudes appear to diverge later just before the final dive, but this video isn't available.
Regards, LG
Frames Video
Thanks Carl. The A/F was at angle of attack and pulling about 4G in the spin... which gets erratic and looks like a departure stall. We'll see where this goes.
Mostly what I would have wanted was near zero tip-off. Of course we got a bunch as Andrew observed. I don't know about the attitude, but it seems that distance could help with disturbance loading. I also wonder what axial loads are being applied. The response would depend on the initial condition.
The best answer is probaly dropping before burst. I will use a longer line next time out.
It would also be great to be wings level on ascent for pictures and such. I didn't figure out a way to do this and cleanly release. I'm sure there's a way.
Still working on video...
Hey thanks for the raw data Larry! It's fascinating!
You can actually see the massive pitch-up from nose-down to nose-up when the balloon ruptures!
Actually, thinking about this, I wonder if the explosive release of gas in such a low density environment is enough of a wind to disturb the airframe orientation? I guess with the balloon at full stretch, it could concievably have several "atmospheres" of gas pressure in it, given that an atmosphere at 88000' is 30mBar or thereabouts...
It makes me wonder whether the aircraft should be oriented nose-up on ascent.
BTW Larry, if you look at |A|, it seems like you could detect rupture release nearly 10s earlier than you did. Might be useful to help avoiding balloon debris
I read Carl's post and he mentioned departure stall (can't find this on this thread but don't know why). The Stinger will depart, but it takes an aft CG or really slowing it down. That doesn't mean that this isn't occuring (not sure the exact frame; yet). I had been attributing the departure to attitude matrix issues and A/P wrap point. But, it's best to open the aperature.
For those interested in the data, I have posted file that I'm currently working in (36M, .xlxs) Corrected Link
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