Doubling Down on Doge - Engineering Flight Test (EFT) 4

Our fourth Dogeship launch went up over Virginia this past weekend, racking up a second successful flight!  The Doge appears to have attained an altitude of roughly 65,000 feet with a flight time of one and a half hours.  The winds were light on launch day, so the total distance traveled was roughly 26 miles through the Shenandoah Valley.  A more thorough post of the flight will come in the next few weeks after we've gotten a chance to analyze the data.

For this launch we attempted to fly two video cameras - one knockoff Go-Pro which was cheap enough to be considered expendable, and our trusty Canon digital camera which was space qualified on EFT3.  Unfortunately the videos all terminated after around 25 minutes of flight.  The Canon, mounted on the outside appears to have frozen.  The Faux-Pro was inside the Doge and overheated due to the heat of the hand warmers.  One major observation was the recurrence of a high frequency rolling motion of the payload combined with a downright violent spinning of the entire system during the climb.  Once we post the video this will become immediately apparent - it'll make you sick!

Many more lessons learned on this flight, but the big success was the second flight of the telemetry tracker, and the first flight with our enhanced mission code, which is just begging for a future blog post.  This system is smart enough to detect launch and land, and has a number of fault codes that trigger various actions to attempt to provide locations in the event of an in-flight emergency.  More on this one to come soon.

The Doge has Landed! - Engineering Flight Test (EFT) 3

Date: 14 March 2015Equipment:  DS Rev 3 (aka Dogeship-3) Launch: Greensboro, NC Landing: Warrenton, NC Time of Flight: 89 Minutes Distance Travelled: 91 miles Burst Altitude: TBD (~61,000 ft)

After our first successful balloon launch with EFT-2 (still to be recovered), plans for EFT-3 were immediately underway with great enthusiasm and vigor. The biggest planned improvement (aside from launching in a warmer location) to the hardware arsenal for EFT-3 would aim to prevent the payload from getting stuck in the tree, by means of a “cut-down” circuit.

The thought of the cut-down circuit would be to attach the payload to the parachute via a single string, and activate a mechanism which would sever that attachment and allow the payload to fall from the tree while the parachute remains suspended in any branches. The original concept would use the phone as the activation mechanism. By playing an audio signal (none other than the Star Spangled Banner for us) from the phone, it would trigger a signal in a circuit and trigger a relay to dump current from a small battery through a piece of Nichrome wire. The hot Nichrome wire would melt the attachment to the parachute, and voila! The payload would fall from the tree. Unfortunately, the cut-down circuit was abandoned last-minute due to insufficient time for prototyping and getting the circuit ready. However, there are plans to use the cut-down circuit as a means for delaying the deployment of the parachute on descent in the future to further reduce mission distance.

In addition to the cut-down prototype, we were ready to try for a higher altitude in order to capture more spectacular pictures. The Kaymont 600 balloon has a published burst altitude of 75,000-90,000 feet. The plan was to fill it with an entire 125 cu ft. tank again, which is an overfill condition and would result in a pre-mature burst altitude somewhere below the published burst altitude, but would allow us a shorter driving distance for recovery.

The last major detail was planning the location. Priority 1: it should be warmer than the first two launches. Priority 2: again, let's do a warm launch! The team decided to take a flight to Durham, NC to visit a family member currently attending Duke University there and launch in North Carolina (warm!).

---

Pre-Flight

The launch date was selected for the March 13 weekend and plane tickets were booked. A Test Readiness Review (TRR) meeting was held again 1 week prior to ensure that nothing was overlooked and that the pre-flights were completed and go/no-go launch criteria established.

Mission Objectives

Primary Objectives (Mission Critical):

1. Verify Telemetry (TM) system utility, including collection of lost frames
2. Verify Payload Cutdown System
3. Verify validity and assumptions of flight simulation using TM and Flight Data Recorder (FDR) data
4. Finalize TRR, Preflight, and Launch Procedures
5. Optional Objective: Record photos during ascent and descent

EFT-2 Flight Hardware

The hardware configuration for EFT-3 was exactly the same as with EFT-2, with the exception of using a smaller parachute for a faster descent, and a Kaymont 600 balloon instead of a 350 for additional altitude before burst. The cell phone was a different model, but served an identical purpose by running the latest TM software for EFT-3.

Risks

In addition to much more rigorous flight planning, the highest risks for EFT-2 were determined as outlined in the chart below. The cut-down device had been originally planned to retire the "tree landing" risk, but had to be abandoned last minute due to lack of testing.

Telemetry

The Telemetry (TM) software was updated for EFT-3 to allow for a few improvements and to test some theories for future flights.

Mainly, the TM software was updated to be able to receive commands once back on the ground, to allow for changes in the message length, the frequency of which messages are sent, and a few other parameters. The software also accepts the “sever” command for the cut-down mechanism, which may prove to have use in future flights as a cut-down or parachute delay mechanism.

Launch Day

Parameter	Imperial	S.I.
Final Payload Weight	1.8 lbs.	0.8 kg
Measured Nozzle Lift	6.2 lbs.	2.8 kg
Free lift (Nozzle lift – payload weight)	4.5 lbs.	2.0 kg
Estimated Burst Altitude	79,000 ft.	24,000 m

Launch Log:

0 minutes – with a small speech and the dual-salute, EFT-3 is sent off. She disappears into light mist falling from the thick clouds. We flew down to NC for this; we weren't about to scrap our launch just because of a little rain!

1 minutes – Communications have already ceased. Although not unexpected this flight, we had hoped to maintain communications a little longer before losing contact. A plot of temp vs. time shows that the temperature is much more reasonable with 2 hand-warmers. And now we wait.

75 minutes – modeled landing time. Still no messages have been received.

90 minutes – CONTACT. EFT-3 is on the ground in the middle of no-where. She appears to be right on the fringe of what appears to be a grove where very tall trees meet some very short bushes.  We route towards the landing zone and wishfully hope that it is in the small bushes…

100 minutes – our team parks at a Methodist Church just outside the tree farm. After reading the posted signs that just forbid firearms and hunting on the land without a permit, we proceed to walk the mile or so towards EFT-3. SMS messages are still coming in loud and clear.

As we proceed along the banks of a small stream, we near the location where the EFT-3 TM beacon has been emitting from. Tall trees on our right, but small trees to our left….still praying that EFT-3 landed a little to the left.

120 minutes – we see her, and she’s on the ground! After de-tangling the lines from thorn bushes, we start the trek back out.

---

Conclusions:

EFT-3 marks the first successful recovery of a launch, including access to both the FDR data and camera pictures. Although it appears that the balloon may have burst earlier than anticipated (even for the overfill condition), the descent ended up going much longer than expected, so we lucked out in not having it go as high as it could have.

The pictures up at the high altitudes indicated that the payload was experiencing severe sway, potentially flipping end over end at times. It is also worth noting that the balloon to parachute attachment line had wound itself around the parachute suspension lines about half way up, which effectively reduces the line length and hence reduces the drag coefficient of the parachute. For future launches, a longer balloon to parachute attachment line should help increase stability, and hence make it more stable on ascent. Furthermore, a parachute deployment mechanism (potentially utilizing the cut-down device hardware) that waits until a prescribed altitude before deploying the parachute would decrease the changes of any lines tangling and reduces the distance and time that would be required for recovery.

Comparison of the actual GPS (red) with pre-flight predictions (yellow) show good correlation with winds, taking into account earlier than expected burst of actual system.

For those interested, the plot of temperature vs. altitude shows that our hand-warmers and cooler insulation design maintained the cell phone temperature within a desirable range for the duration of the flight.

The Most 1337 Doge Yet - Engineering Flight Test (EFT) 2

Date: 10 January 2015Equipment:  DogeShip Rev 2 (aka DS-2) Launch: Albany, NY Landing:  Nashua, NH (targeted), Bernardston, MA (actual) - [More on that “near miss" later] Time of Flight: 84 minutes Distance Traveled: 62 miles Burst Altitude: TBD (~56,600 ft) Payload Status: Still in a tree...

With one launch under our belts, but the hardware being several hundred miles out at sea, we were determined and eager to head back to the skies as soon as we could reasonably determine the root cause of the failure on EFT-1. After analyzing the Telemetry data, we were able to tweak the input parameters in our Python flight simulator model, and obtained our best educated guess as to demise of the ill-fated EFT-1.

Despite the bone-numbing, frigid conditions of our first launch back in November, here we were again packing the car at 7AM in balmy 3F conditions. After having driven out to Albany, NY the previous night to crash at a friend's apartment, the car was packed and we embarked for the launch site.

---

Launch Plan:

With a planned launch date of January 10th, the winds for the weekend necessitated a trip out to Albany, NY for an estimated recovery around Nashua, NH. Parametric studies were run for various configurations of nozzle lift (total lift minus the weight of the balloon), weight, and descent drag of the parachute to ensure that we would have all the information necessary on launch day to bound our predictions.

Mission Objectives

1. Verify Test Readiness Review (TRR) and launch procedure effectiveness
2. Verify Telemetry (TM) system utility and reliable recovery techniques
3. Verify validity and assumptions in Python flight simulation using TM and Flight Data Recorder (FDR) data
4. Verify utility of the common fill/mounting system
5. Optional Objective: Record photographs during ascent and descent

---

Risks

In addition to much more rigorous flight planning, the highest risks for EFT-2 were assessed and ranked to maximize the probability of success.

Both the cell phone life at cold and cell phone coverage at the landing zone were the highest impact risks, since either occurrence would likely mean we would not be able to find and recover EFT-2. Lesser risks included flight sim model inaccuracies resulting in an uncertain landing location, and the very high probability that EFT-2 would land in a tree and could be found but not easily recovered.

---

Telemetry

Similar to EFT-1, the Telemetry (TM) phone would act as a Flight Data Recorder (FDR) in-flight by recording accelerator data, temperature, GPS, and much more for us to analyze. In terms of recovery, the phone would send us an SMS text message once back on the ground in order to locate the payload for recovery.

---

Launch Execution:

After final pre-flight checks the night before (OK, maybe it was 2AM the morning of...), the launch-site selected was at a school just south of Albany, NY, ensuring that we were outside of controlled airspace and not in line with any of Albany’s runways.

A team of five people were present to help out, which proved invaluable since the temperature was a frigid 10F at launch, and the extra help allowed us turns to swap out and warm our hands.

The QuikFill inflation system worked wonders! A quick attach/detach allowed for periodic nozzle lift checks, and the direct attachment to the CGA-580 valve on the helium tank meant there was no chance of any Helium leaking during the fill.

After preparing the payload, enabling the TM phone, and completing the filling of the balloon, the initial launch parameters were recorded and EFT-2 was determined a GO!

Parameter	Value	Units
Final Payload Weight	1.5	Lbs.
Measured Nozzle Lift	7.2	Lbs.
Free lift (Nozzle lift – payload weight)	5.6	Lbs.
Estimated Burst Altitude (GPS data not yet retrieved)	56,600	ft

Launch Log:

0 minutes – and she’s away! Godspeed, EFT-2.

https://www.youtube.com/watch?v=K6OI5Xx3cDM

2 minutes - with the balloon climb rate seeming to be on target, the first few minutes of the launch seemed to bode well for EFT-2.

3 minutes - communications unexpectedly cease.

Noticing how the temperature had been slowly creeping up over time from 25C all the way to 50C at our last telemetry response, a sinking feeling developed in our stomachs (and yes, we did in fact just switch to SI units...much more useful when doing anything except describing the temperature outside!). Pre-flight testing with the TM phone indicated that it would shut-down due to overheating somewhere around 56C. Is it possible that the phone shut-down and EFT-2 would suffer the same un-recoverable fate as EFT-1? Only time will tell.

60 minutes - still not a single comms message has been received since 3 minutes. Powered off a mix of caffeine and adrenaline, we frantically continue monitoring for any sign of the Dogeship, but concerns continue to grow that the phone shut-down due to over-temp and that there will be no way to find it once she lands.

75 minutes - if the balloon burst as expected and the flight simulator was accurate, EFT-2 should be landing at any moment. Every agonizing minute that goes by suggests more and more that we won’t be hearing again…

84 minutes - CONTACT! SMS messages with GPS coordinates have been received, and EFT-2 is on the ground in Bernardston, MA (Zip code 01337 – yes, 1337). Re-route the car GPS and off we go to shoot up Rt. 91 from the Mass Pike.

90 minutes - only miles away from EFT-2, a major accident on the highway has traffic backed up for miles, and we’re caught right in the middle of it. Excited yet frustrated that we aren’t moving faster, we press on.

120 minutes – we arrive at the site, and spot something orange from the road. It’s a decent way in on someone’s property. Knocking on their door, we obtained permission to take a closer look and headed out to find EFT-2.

Unfortunately, EFT-2 will not be recovered today (or any time soon). She’s 80+ft. up in one of the tallest trees amidst branches.  Stay tuned for updates on the recovery efforts thus far and the one planned that will hopefully bring her down.

---

Conclusions:

Overall, EFT-2 was a giant success, despite the fact that she is still 80 ft. up in a tree in Bernardston, MA. All primary objectives were accomplished, and the tree landing was not unexpected, as predicted by our top pre-flight risks.

On future flights, it will be expected that we will lose communications after takeoff, but that the FDR will record all the data for us to recover after, and that the TM phone will prove a reliable location technique once the payload is back on the ground.

Also, we wanted to give a shout-out to the awesome launch crew that helped us out: a huge thanks to Dave, Andrey and Brian for helping with the launch!