High Altitude Balloon Project

#1

DMS High Altitude Balloon Project

Before I get to the meat of this post, I have a couple questions:

  • Who is already involved and in what capacities?
  • What have other people done?

The intent of this post is to try to coordinate with the rest of the people who intend to be involved. I’ll say what I know / have heard about as much as I can, but the project is still pretty malleable at this stage, unless the info I have is very wrong.


Information I have:

The HAB project is meant to result in a balloon that can launch a glider drone that’ll return to home. My understanding is that the current vision is 2 missions: the first develops team competency with actually managing balloon launching and should also clue us into what particular sticking points high-altitude missions should have, in case it’s not predicted correctly. The second mission should be the actual drone launch. (It was originally supposed to be one mission, but I think we decided that’s a little much for people who don’t know what they’re doing. If there’s someone who knows what they’re doing and wants to be involved, that could change back.)

The original target altitude was 60,000ft, but I believe we turned the hard requirement down to 30,000ft. I believe 60 is still a stretch goal. I forget; it’s been a year since we had this discussion.

We have a balloon, a styrofoam box, and a regulator / valve thing (I’ve forgotten what they’re called). And electronics somewhere, so I am told. If there aren’t electronics somewhere, I can run the Featherweight Raven I’m getting for rocketry, so long as it takes <45m for the parts of the mission we care about. Otherwise, someone can hack something together with an Arduino or something.

When Romeo and I sat down last year, we hashed out a bunch of other general subjects of concern, including:

  • battery technology (probably lipo, possible temp. concerns)
  • drone airframe (considered simplest part, likely an off-the-shelf foam craft with an Ardupilot or something simple)
  • atmospheric data (I found a decent website on this last year, need to re-find it)
  • temperature control / insulation needs
  • FAA regulations
  • testing (cold / low pressure chamber?)

What I should probably do is spend a chunk of time reading details on previous projects documented online. I remember doing this last year and not finding much to go on.


Anyway, if you intend to get involved, I intend to give this project some momentum.

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#2

I have interest in this project. Please keep me in the loop.

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#3

Current status:

We have electronics. Andrew LeCody had some he’s been hanging on to for 5 years or so (this project is that old). There is custom firmware on the DMS Github; I will need to find that Github. We have a sensor board and a radio for transmitting position during flight; we will need to get a different battery though, since the one provided is likely to be too old / bad.


I have interest from the following people:

  • Ken Purcell
  • Travis Zinger
  • Justin Edwards
  • Romeo España (theoretically)

I’ll have to schedule a meeting sometime soon. Agenda will probably include:

  • overview / discussion of high level project direction (the multi-mission model, with at least 1 learning launch and 1 drone launch)
  • acquisition of other hardware (lift gas, ground support hardware, funding source)
  • fabrication and testing requirements / scheduling (whether we want to test thoroughly or throw things at the sky, who builds what)
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#4

I am interested in participating. I can help with software engineering.

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#5

Could we possibly have weekly meeting about HAB project(s)? Maybe Tuesday or Thursday evenings at 6p or 7p?

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#6

The firmware is here:

And I’ve got notes on the wiki:
https://dallasmakerspace.org/wiki/Near_Space_Balloon

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#7

For those of you interested, the UTD amateur radio group is hosting another class this summer for high school students who will design, build and launch a high altitude balloon. The telemetry data is available for anyone with a radio to monitor, and I would be surprised if they wouldn’t accept help with some of the corralling of the students.

Andrew KoenigJun 5 10:01 AM
It’s not officially with PARKBalloon, but we’ll be having two launches with
UTD this summer. It’s part of an Intro to Space camp with local high
school students. The campers will be designing a tracking and telemetry
system (based around Arduinos and a TinyTrak4), and coordinating a lot
of aspects of the launch.

Details (subject to change):

Date/Time: July 1st (Weds) @ ~10:00AM

APRS: K5UTD-11 144.34MHz (TT4 + Telem)
APRS: KE5GDB-11 144.39MHz (RasPi)
SSTV: 144.5 (Robot 36?)
Crossband Repeater: 446.050MHz (110.9) uplink, 147.500MHz downlink

There will be a second, similar launch in early August too.

They have done this for several years, and I believe were never able to recover last years payload (~ $1500). Andrew is active in several local HAM groups and I can help you get in touch with him if you have any questions or want to volunteer to help. Just remember this groups for the high school students to do the bulk of the work.

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#8

I have had an idea bouncing around in my head for several years now for a HAB project. I have some detail around my idea in a Google Doc. The general idea is to combine the concepts of a sealed gas balloon with that of a hot air balloon. Comments good or bad are welcome.

Balloon Project Doc

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#9

Sorry, I’ve been taking time off due to a death in the family. I’ll get back to this as soon as I can. I’ll try to get back into this before the month is out.

First order of business is probably going to be a kickoff meeting where we can agree on basic details, tasks, perform coordination, etc.; we’ve got a lot of ideas but not many people have had direct input. I like bi-weekly at 7pm Tues myself. Suggestions about time / day / frequency are welcome.

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#10

I took a look at your balloon proposal. In order to go higher it would essentially need to be lighter / generate more lift than the extra components subtract from it in weight. I started looking into some of the math involved and I wasn’t able to clearly see whether you could get enough additional lift.

I think one way of thinking about it is “lift per unit of helium / hydrogen”. Adding heat essentially increases the efficiency of a given quantity of lift gas in lift production, but max height will be dictated by bursting diameter, which will be a function of internal gage pressure. At max altitude, you are essentially trading weight from lift gas with weight of your heater and recirculation system. If the mass of gas you save by heating it is greater than the mass added by the heater and recirculation system, you get more lift, which means you can pull a bit of gas out (pre-launch) and postpone bursting ever so much longer, and thereby go higher.

A 3S 3000mAh LiPo at 30C will theoretically max at 90 amps at ~11V, or about 1kW, and weighs some 8 oz or so, I think. The heater you’re proposing pulls 1.5kW. So you’ll need a pretty heavy LiPo just to power the heater.

The amount of gas in a balloon at launch … for an 8ft dia. balloon is about 270 cubic feet, at STP (unpressurized) is some 3lbs of helium according to these online calculators, so maybe you could get it hot enough to save a pound of gas? (How hot would it need to be? 100°F? 150? Is it a polytropic process, making the math that much harder?) Whether or not you could save that would depend on so many factors, though, and I’m personally concerned with what the heat loss will be at altitude; it’ll be hotter than atmospheric if you heat it, but it needs to be way hotter (delta-T of some 100°F or better, I’m guessing) to get the necessary efficiency to offset the additional weight, and I’d have to do the math / research, but I feel like a thin layer of latex will not be great at preventing heat loss.

A lot of smaller concerns I remember. With a closed hydrogen-only system, you technically can’t start a fire no matter how hot the heater gets (must have oxygen, period), so unless there’s a good chance of accidentally letting it get oxygen I wouldn’t be concerned about that aspect of overheating. I’m not particularly concerned about a fan; added weight for a function I’d hope I could fulfill with convection, and fancy ductwork or something if I had to do something to cool the heater. I want to see what a 1500W heater looks like; I did stuff with resistance wire (NiCr) a while ago and I’d expect 1500W-worth to be quite a lot of wire (i.e. kinda heavy). I would not add any extra weight I didn’t absolutely have to, so no valves, no sideways jet valves, absolutely nothing fancy at all, unless I had a compelling case it’d make it more efficient.

Basically, for a variety of reasons I think your proposed balloon would be too heavy and inefficient (in heating the gas and keeping it hot) to actually achieve a higher altitude as intended, and I don’t think it has any practical use outside of achieving a higher altitude that a normal balloon couldn’t fulfill more simply. (Keep in mind I don’t actually have much experience with weather balloons, so I could be totally off-base.)

I think if you had a better (i.e., higher power to weight ratio with a reasonable energy to weight ratio) power source than a LiPo, it might become more realistic. I’d say some kind of fuel (gasoline, kerosene), but then you need oxygen from somewhere, making the system more complex, maybe intractably so. At that point, it’s pretty much a regular hot air balloon anyway.

It’s a very interesting math / physics problem, though. I came up with a differential equation for balloon lift; I’m guessing it’ll have to be numerically solved, and I will also need stress-strain for the balloon material, which I’m having trouble finding. Given enough development, I might be able to simulate the flights, which would remove a lot of the difficulty, the same way OpenRocket makes rocket design relatively simple.

The forces that matter most are gravity, buoyancy / gas pressure (same thing), and drag. Wind is not very relevant unless it’s going to cause a balloon material failure; I’m not trying to predict anything besides altitude at this point, so I don’t care much about moving sideways. Balloon material restorative force is relevant in a lot of the internal dynamics that have implications on the growth of the balloon, as well as the heat stuff (the balloon growing actually makes the thermodynamics a bitch of a problem for me).

When you set up Newton’s Law, you get acceleration is dependent on the square of velocity (drag) multiplied by a few things which are altitude dependent (density, drag coefficient (also depends on velocity), cross sectional area (which depends on pressure differential primarily, which will depend on altitude and lift gas temperature / density)). The lift will depend on balloon diameter (only, I think), which will depend on altitude and lift gas state (which I need to relate to altitude or velocity somehow if I can). Thus it all becomes a differential equation with the dependent variable of altitude and independent variable of time, but it’s very nonlinear, and unless a lot of simplifications can be made or accidentally have one of those nonlinear DEs that have solutions, it will have to be solved numerically.

There’s some simpler analyses on the internet that make a lot of assumptions, and a few altitude vs. time plots. They all suggest that assuming a constant lift rate is reasonable, since as drag reduces due to lower density, the balloon grows in frontal area to essentially balance it out again, keeping lift rate essentially constant, and the data shows straight(ish) lines that suggest it’s a reasonable assumption. So for the time being a super-detailed analysis is likely unnecessary … unless you start heating it up, then things get weird (unless there’s some simplifications I haven’t seen). Anyway, I think that for the upcoming mission, I won’t have to do really hard math, but for your balloon it might be useful.

I need to stop.

ANYWAY, so that’s a lot of my thoughts regarding your balloon proposal. I hope I’m not coming off too poorly or too critical; FWIW the way I see it is if you have good answers for most questions / criticism, you’re probably on a good track, and if you don’t, it’s probably better to learn it’s not tractable and abandon such “dead-horse” tracks before you burn 100 hours and $2,000 on something you can’t get to work.

It’ll probably fly, but I don’t think it’ll be better than modern designs without a bunch of consideration.

Just though of one other thing: hot latex might have different material properties (i.e. a different burst point). Something to consider.

Ok, stopping now.

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#11

ALSO

I think 7pm on Tuesday the 30th is a good time for a first meeting.

Agenda:

  • Discussion of current status, including current mission statement, hardware in hand, etc.
  • Community agreement on mission
    — Discuss overall plan / 2 mission concept
    — Decide approach
  • Divvy up tasks
    — Launch point finding
    — FAA compliance work
    — Construction and testing jobs
    ----- Electronics (programming, hardware)
    ----- Ham radio guy(s)
    ----- Balloon hardware people
    ----- Drone building
  • Decide meeting schedule
  • Decide deadlines for tasks
  • Decide extent of ground testing to be done
  • Decide extent of calculating / math / physics / heat transfer work / mathematical optimization / paper design to be done

Target meeting end time is 8pm.

If everyone has good background knowledge, we might not dedicate a ton of time to background research, but I don’t know what to expect, so we may spend a bit of time doing background work. That’ll depend on what people think at the meeting. I know when I was at UTA, rocket team people had to spend a month or two doing background work on new things, but then again nobody came in really knowing what to do. There’s some folks at the makerspace who don’t need to spend a month researching. We will see.

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#12

Thank you so much for the analysis. I have been assuming all along that there are flaws in the idea. I think the biggest eye opener is the amount of heat I might need in order to make a difference. I have been assuming that if I can increase the temp by 10-20c that it would add significant lift. Maybe not. I need to study the gas laws more.

My thought is that I want to optimize lift (by decreasing density) at just below the burst diameter by regulating pressure. Keeping the balloon from bursting is all about pressure, but keeping the balloon rising is all about density. The unknown for me is how much does heat help reduce the density.

I found these a one point in my research. I will try to find them again. If I remember correctly there were at least 3 models for elasticity and none were perfect. For one thing, I think the full effects of freezing and becoming brittle aren’t well understood.

It’s more an issue of density than mass. However, your point is just as valid. A battery has a very high density compared to the atmosphere at 30km.

I am also wondering if simply keeping the balloon above freezing may have a significant positive impact. One of my concerns with using a latex ballon is that latex becomes brittle when frozen. The temperature at 30km is well below freezing. Part of my thought was that if I can keep the balloon above freezing maybe it would stay elastic enough to continue to expand (to a point).

I am guessing that the pressure difference between inside and outside the balloon would remain near constant or growing slightly linearly as the pressure outside decreases and the balloon compensates by expanding. However, when the balloon freezes or when it nears it’s breaking point the pressure difference would begin to rise more dramatically due to the lack of elasticity to compensate.

My intent was to use a USB phone charger with two ports. One port (5V 1A) for my computer and one the other port (5V 2A) for the fan/heater. It’s 10,000mAh and weighs 213 grams.

That is the question I have. How much heat is needed to be worth it. I agree that the balloon will be leaking heat very quickly.

Another potential idea is to heat the gas on the ground. There will be a max temperature dictated by the latex balloon and other components, but the balloon wouldn’t need to carry the power needed to heat the gas while still on the ground.

On the point of Helium or Hydrogen: My initial plan was to use Hydrogen as it is lighter. However, Helium has a significantly lower Specific Heat, meaning that is takes less energy to heat it than Hydrogen. (5.19 vs 14.32) This again leaves the choice dependent on the feasibility of heating the gas.

-Robert

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#13

I am considering what you have said. I have not looked at the equations…however I had a thought.
Do not consider time in the equation at first. Using standard pressure/temperature charts can resolve the math without the interim velocity needed. (remember that velocity is more related to thermal gain/loss and down range drift …both in action and reaction to heat).
atl (M) temp © Pressure (hPa) Density K/m3
0000, 15.0, 1013, 1.2
9000, -43.5, 310, 0.47

Once basic data is compiled for launch and terminal altitude…then other factors can be considered much more easily. In fact, the data can be compiled at known standard altitude data before you begin therefore giving you a simple equation derived from those points to start with.

Now one can look at what the velocity and lift may be at those points…and even add heat from there at given points to find the new volumes etc. This breaks down the process not to actual altitudes but to standards. Looking at only points will give you a derivitive formula. From there you can expand your data to include temperature, added heat and heat loss, again possibly at points…then derive again.
I would remind you that if the balloon rises faster than the heat loss (at least until it hits an inversion layer) then the ballon is constantly “adding heat” relative to the surrounding air. (about 1.5C per 1000M altitude). As long as your ballon loses less heat than that, it is getting relatively warmer. I think this may be the case for you if all goes well.

The optimum case would be that the ballon design would retain enough heat to increase its lift through the rise to burst point. Possibly one could calculate this from ony the first 1000 ft data?

I found Standard altitude temp pressure data at this site. I have not checked it against other sites. I think that this will simplify your process.

http://usatoday30.usatoday.com/weather/wstdatmo.htm

Hope that this helps.

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#14

Here is some additional proof of this. Here is a classroom science experiment using a regular party balloon.

This shows that while being inflated the pressure difference (inside vs outside) remains relatively constant as the elasticity of the balloon allows for the pressure to equalize (minus some constant). However, once it has reach the upper bounds of the elasticity then it begins to act more like a solid container where the pressure will continue to rise in relation to the outside pressure until the balloon bursts.

Here is another experiment using a larger balloon which shows the pressure difference. Unfortunately they didn’t burst the balloon though.

http://scipp.ucsc.edu/outreach/balloon/labs/InflationExp.htm

In that experiment, the pressure difference was around 0.5kPA. What I don’t know is how far beyond the elastic point the pressure will rise in the Kaymont 1500 balloon I am planning to use. The sensor I have chosen is a 0-10kPA differential sensor. It seems likely that while the balloon is elastic I will only need 0-1kPA, but I don’t know how much over that I will need while the balloon is “solid”. It seems likely I will need to burst at least one to find out.

-Robert

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#15

Reminder: Meeting is TONIGHT at 7PM at the Makerspace. I still plan to be there, and I hope everyone who’s interested can make it as well.

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#16

So we had a meeting Tuesday and made some decisions:

Plan is three mission phases. First, we will launch with what we have asap in order to get some momentum going quickly and to get the non-UAV side nailed down. Second mission is a drone system test launch, where we basically do everything except drop the drone. Third mission will be the drone drop. In the event we find we need more than one launch to achieve the goals of one of the missions, we will add more launches.

The rest of the meeting focused on what we will do for the first mission. We agreed that keeping it simple was ideal.

For ground test needs, we decided electronics function and battery life as well as radio function and communication to ground HW would be the primary foci; no pressure chambers or dry ice testing.

For analysis, we can do basic things like burst altitude (there’s easy math and/or internet calculators for it) and ground path (with an internet calculator) for launch site planning purposes. We will also probably calculate parachute size. Keeping it simple, essentially.

The current to-do list is as follows:

  • Electronics testing
  • Radio testing
  • Launch site selection
  • Launch hardware construction / gathering
  • FAA compliance
  • Balloon construction

We will meet bi-weekly, Tuesday’s at 7pm, starting this coming Tuesday (the 7th, I believe). I need to learn how rooms are reserved.

Tasks were not assigned to anyone; instead we discussed doing things more workday style, where we will just all get together and just work.

There will be no hard deadlines.

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#17

Second meeting tonight at 7pm. We will be in the community room if it’s not too busy, otherwise we can park wherever (maybe lecture hall again). Also, the events system seems to think 7pm tonight is earlier than right now, so I can’t submit it.

This is a building / working meeting, there isn’t an agenda per se, but there is a task list (written above). Doing any single thing or combination of things on the to-do list is acceptable.

I will personally try to do some of the following:

  • Electronics basic function test (i.e. try to turn it on)
  • Read / browse code from github
  • Read manual for radio
  • Create list of needed ground hardware
    — Ground radio
    — Balloon filling stuff
    — Balloon tethering stuff
    — ???
  • Basic calculations (5 minute variety) & weigh current balloon h/w

I won’t try to turn on the radio unless Romeo’s there, since I don’t have a ham license yet. If he is there and there’s time left, I’ll look into getting the radio and electronics talking.

I think radio testing, electronics testing, and ground / launch hardware work are the most involved 3 things to do, so I will focus on those tonight.

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#18

I will be there tonight.

I think this is because they want you to schedule things 12 days in advanced. I can take care of schedule the next one.

Since the last meeting I studied for and passed the Amateur Radio Technicians exam. I don’t have my callsign yet (probably this weekend) so it won’t help for tonight as I’m not allowed to transmit until then, but it may help in the future if Romeo can’t be there.

-Robert

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#19

Hi All, Nick here.

I’ve been excited about this project since I first heard about it, and I’m really happy development is starting back up.

Launching a high-altitude balloon with an electronics payload and successfully recovering it sounds like a challenge, and having the payload fly itself back to a designated landing site will be very fun to try and achieve.

I have no experience with balloon launches, so I’ll rely on the knowledge of others for the plan to get it up! Where I can be more helpful is getting our payload back down. I have a few years experience with RC airplanes and autonomous flight. Previous projects have shown that it’s possible to use an APM/Pixhawk and detect the balloon break, activate a release mechanism, and switch the aircraft into auto mode to follow it’s return trajectory mission.

I can:

  • Help design/choose the airframe
  • Loan a Pixhawk/Pixhawk clone as the autopilot
  • Loan an RFD900+ long range telemetry system (1W 900mhz radio modem transceivers)
  • Recommend hardware for long-range RC control and FPV video transmission
  • Coordinate with our Amateur Radio committee to add a a backup APRS telemetry payload
  • Use my HAM callsign for communications systems that require an amateur radio license.
  • Integrate / tune / program the autopilot.

I look forward to meeting others that will be at tonight’s meeting.

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#20

More likely, he is confusing 7 a.m. with 7 P.M. The calendar uses a 24-hour clock.

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