Flying Squirrels #6 – FS#1 Mission and goals, What’s the point?
The Mission
Before I can describe the flight software I need to make clear what the specific mission goals of Flying Squirrel #1 (FS#1) are. The software design is based upon these goals and an understanding of the goals will make the software easier to understand.
In a nutshell the goal of FS#1 is to provide a test bed of some of the basics of a balloon flight. It is a first attempt at failure (See side bar below) to learn what I need to do and plan for next time.
Failure is part of the mission and how we learn stuff.
A ham friend of mine, Mike KA9CQL, gave me the phrase “To learn anything you have to get to ‘Fail’ first.” In my engineering experience, I instinctively knew this but, that simple statement really sums it all up succinctly.
It would be nice if everything works as expected with nothing unexpected happening during a mission. This probably almost never happens in a new scientific/engineering endeavor. Failure is always an option, it is expected and will even be desired in this case.
FS#1 is designed to fail. How it will fail and why it failed is unknowable until it happens. At best the balloon will fail (burst), that is a given for a latex Helium balloon. The teaching moment will come when something fails, and we endeavor to figure out what failed and hopefully answer why it failed so we can adjust accordingly next time. The only real failure will be to learn nothing from this endeavor.
Let’s face it our dear Flying Squirrel #1 is doomed to fail, ultimately violently in free fall. In it’s sacrifice for science, we will learn something and share it. Failure is how we learn.
Goals
The mission of FS#1 is designed to answer these questions:
- How much balloon and Helium do I need to lift the weight of the antenna and flight computer package?
- What are the logistical challenges of a launch?
- Does the flight hardware hold up under the stresses of winds,temperature and altitude?
- How long will I/we be able to “hear” the balloon on the radio before contact is lost?
- Does the FSQ protocol work as expected? What baud rate works best?
- What ground equipment do I need and what I need to do to get ready for a flight?
- What is the ascent rate of the balloon?
- How high will this flight go?
- How cold is it up there?
- What did I forget/not think of?
How Far & Away?
One key mission decision about a balloon is how fast do you want it to rise, how high will it will burst and where it might come down. Since FS#1 will not have a GPS, I can only guess where it may go. Possibly, but not very likely it will be found someday, and I will hear from the person who found it and where they found it. I don’t expect this to happen.
In lieu of GPS tracking, there is an interesting site that will help estimate the path of the balloon at http://s3research.com/tools/flightpredictor . Using some guesses entered into the estimator, I can get a sense of what might be possible for FS#1 My inputs to the estimator are:
For my estimates, I am using a location in the Mojave Desert called Johnson Valley – Cougar Buttes.
This may or may not be my launch location but it is one possible choice. A lot will depend on the weather on the day of launch.
I ran test calculations on different days (different winds), using reasonable guestimates of the ascent rate with the having the balloon bursting at 10K, 20k & 30k feet. One estimate had FS#1 travelling to Denver Colorado. Other estimates were shorter, still within California near the Arizona border. Generally, the prevailing winds go from West to East, however there are conditions in southern California called Santa Ana winds that reverse this air flow usually in the winter after a storm front has moved through the area. One estimate, with Santa Ana wind conditions, had the balloon travelling only slightly West of the launch location.
The ascent rate is a big guess. Five hundred feet/min seems reasonable to me, but I really don’t know. I am counting on FS#1 telemetry to tell me what the real rate is so I can make better predictions next time. I can use the ascent rate information to estimate, after the fact, where FS#1 did travel. This is one of the key bits of data I hope to learn more about on this mission.
Where the balloon goes will depend on the strength and direction of the wind. Also affecting the distance is the rate of ascent and height of the balloon burst. The longer the balloon climbs (slow ascent rate) and a higher the burst altitude, will keep the balloon in the wind for a longer duration and the balloon will travel a longer distance as a result.
I don’t plan to have FS#1 set an endurance record, so I will plan for it to rise quickly to burst altitude. This will keep the time I have to monitor the balloon down to a few hours maybe. (With luck). To get a quicker rise time the balloon needs more positive lift (The lift ability above the weight of the balloon package). This means the balloon will be more fully inflated, which will also reduce the burst altitude because the balloon will expand as it rises due to lessening barometric pressure as altitude increases. Ultimately the balloon will stretch past its limit and burst. The Ascent Rate and Burst height are related to one another and work together to control the flight time. I hope to learn more about the burst altitude of the latex balloons I will be using for FS#1.
The Data
To answer some of the measurement questions, the telemetry system will send the following key information:
My callsign – Required by the FCC Rules governing Ham Radio
A sequence number starting with 1 and incremented on each transmission.
The FSQ Baud Rate the message was sent with. FS#1 will alternate between 6 and 2 baud between odd/even telemetry messages. The goal is to see what difference the baud rate makes when signals get weak. Faster baud rates will conserve power with shorter duration transmissions. Lower baud rates, in theory, are better decoded when signals are more difficult due to noise and week signals.
Altitude in meters. This will let us know what the burst altitude was. The ascent rate can also be calculated by using this data and the sequence number
Temperature in degrees Celsius. How cold will it get?
Barometric pressure in Hectopascals (hPA). What is the pressure at altitude?
The FSQ protocol also includes some CRC check Digits to validate the message and an optional command to log the telemetry received into a log file fs1.txt. Details of the exact telemetry message will be discussed when I discuss the Arduino code for the flight.
FS#1 will wait one minute after finishing a transmission before starting the next one.
The larger program goals revisited.
The goals above are for the first Flying Squirrel of many. The Flying Squirrel program has a set of goals of its own, as discussed in the first article of this series . The whole program goals are as follows:
- Build a cheap, under $50 flight payload.
- Ability to circumnavigate the globe.
- Capable of global telemetry communication with an ability to track it on a map. 24hrs a day.
- Fly on a party balloon(s). Weight will be critical. Maybe 12 Grams is the limit. Final weight is still TBD.
- Share the process I have gone through and share what I have learned on the subject… in detail.
- Learn stuff.
- Have fun!
FS#1 will not meet all of the above program goals, but will support these goals in future missions. The goals #1,#4,#5,#6 & especially #7 are achievable with this first flight. The global goals of #2 and #3 were not designed to be part of the FS#1 mission. Now that I have built the FS#1 hardware the #4 sub goal of 12 grams is way off. However, it will be able to fly on a balloon that was obtained from a party supply store at a low cost. I have not yet added up all the mission costs, but I think FS#1 is well under the $50 goal defined in #1 above. I will verify this and give a costing of the parts and supplies in a later post.
Next up the flight computer software will be discussed.
73s de Don KJ6FO
