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Sep 19, 2006, 06:50 PM
Aircraft Designer Guy
AJWoods's Avatar
Build Log

Solar Powered UAV Project


Hi Everyone,

My name is Adam and I'm a senior in the Aero/Astro department at MIT. My partner and I are designing/building/testing a solar powered UAV for our senior capstone course, Experimental Projects I/II. It is a two semester course consisting of pairs of students who design and carry out their own experimental project. Last semester was dedicated to the design of our aircraft and the associated testing scheme. This semester we will actually build the aircraft, and test it to se how closely its performance matches the various computer models we've developed. I figured I'd start a build log for the project, so that I'll be able to remember where a year of my life went

The course administrators place a $500 budget cap on each project, and since we have essentially all the supplies inhouse we needed to put the vehicle together, we decided we would use the $500 mark as a cap on our Solar Array cost. Since we were going to devote so much time to the project, we decided to make the aircraft meet the FAI f5sol requirments, so we could qualify for any duration records we might set along the way (current record is 11+hrs). As a result the design constraints were as follows.

$500 array limit (we sized it for $400 so we could replace broken cells if needed)
900g minimum weight limit
0.75m^2 projected wing + stab area
3.5m span limit (for transportation and fabrication reasons)

We wrote a multidisciplinary optimization script in MATLAB that maximized power margin (details for those who are interested) to come up with an optimized wing configuration, then we selected motor/number of cells/stab areas to match the wing.

Our Final A/C configuration is as follows:

S=0.72m^2
B=3.31m
AR=13.6
Weight~10N
Airfoil=NG01
Cruise Thrust= 0.33N @ 5m/s

The Array will consist of 18 A-300 Sunpower Solar Cells (we are still looking for a supplier if anyone has any ideas), which will put out about 56watts at full power. There will be an pic controller onboard that serves as a maximum power point tracker and automatically regulates motor power to maximize the array's efficiency.

The generous people at Maxon Motors have provided us with 90% brushed motors and Polecat Aero has supplied us with EZ bubble dancer stab parts, which will make construction a bit easier.

I guess thats about it for now. We finished cutting wing cores today and will start layup later this week. Questions and discussion are welcome. Pics will follow.

-Adam
Latest blog entry: Giant LEGO Helicopter
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Sep 19, 2006, 07:41 PM
Professor of Wood
kd7ost's Avatar
Good stuff Adam,

Although I don't know a source for the panels, I do recall some threads in the past that might be helpful to you. The guys that did the 48 hour endurance flight have posted on here. One looks pretty prolific. You might concider contacting them via email if they allow it or at least PM for some information on purchasing the cells. They used the same ones you're looking for.

Please keep posting here. It sounds fun and we would like to watch.

Dan

https://www.rcgroups.com/forums/showthread.php?t=378861

http://www.acpropulsion.com/

http://www.acpropulsion.com/ACP_PDFs...lar%20Cells%22
Sep 19, 2006, 07:47 PM
Aircraft Designer Guy
AJWoods's Avatar
Quote:
Originally Posted by kd7ost
Good stuff Adam,

Although I don't know a source for the panels, I do recall some threads in the past that might be helpful to you. The guys that did the 48 hour endurance flight have posted on here. One looks pretty prolific. You might concider contacting them via email if they allow it or at least PM for some information on purchasing the cells. They used the same ones you're looking for.

Please keep posting here. It sounds fun and we would like to watch.

Dan

https://www.rcgroups.com/forums/showthread.php?t=378861

http://www.acpropulsion.com/

http://www.acpropulsion.com/ACP_PDFs...lar%20Cells%22
Thanks for the heads up on those threads. The so-long 48 hour guys used A-300's on their aircraft. We were going to ask them about where they purchased their cells, nice to see some of them are fellow rcgroupers .

We tried to get cells from the supplier who provides a-300 for the MIT solar car team, but they have an agreement with sunpower to sell only encapsulated cells, and we need just the bare cells.

Anyways I'll be sending out a bunch of pm's and see if anyone's got a line on A-300's
Latest blog entry: Giant LEGO Helicopter
Sep 19, 2006, 07:55 PM
Professor of Wood
kd7ost's Avatar
Quote:
Originally Posted by MIT KID
We tried to get cells from the supplier who provides a-300 for the MIT solar car team, but they have an agreement with sunpower to sell only encapsulated cells, and we need just the bare cells.
Bummer,

I take it you've tried to get them direct from sunpower after explaining your project and the need for getting them without the packaging?

http://www.sunpowercorp.com/solarpanels/

Dan
Sep 19, 2006, 09:00 PM
RCAPA #14
Myron's Avatar
Hey MIT Kid,

We tinkered with the idea of using some solar power in one of our birds.. We found an outfit here in Austin that is doing some incredible stuff with solar power. They have a coating that is kinda painted on. Its a little pricey at 300.00 per watt but I am sure the price will come down as technology gets better... Google them up at Heliovolt...

Myron
Sep 20, 2006, 01:37 AM
Registered User
Yay for Matlab!!!! catia is sweet also
Sep 20, 2006, 08:09 AM
Aircraft Designer Guy
AJWoods's Avatar
Quote:
Originally Posted by rclinks2002
Yay for Matlab!!!! catia is sweet also
HAHA yah. Whenever I click on my start bar Matlab is at the top of the most used programs...kind of sad
Latest blog entry: Giant LEGO Helicopter
Sep 20, 2006, 07:18 PM
Aircraft Designer Guy
AJWoods's Avatar

Wing cutting


So after about 6hrs of cutting, all the cores are done. We did all the cutting on the department's CNC hot wire. It's notoriosly finicky (all the error messages are in french) and hadn't been used since last semester, so it took about 8 practice cuts to get everything working smoothly. We were a bit worried about cutting the tips because the airfoil is only about 5.5% thick and we have a tip cord of only 10cm, but the everything came out really good. We did the tip pannel in two sections to prevent melting, so we've ended up with a 7 pannel wing
Core prep is scheduled for tomorrow, and we should be ready to start laying things up this weekend.

BTW we used Dow Highload-60 foam for everything
Latest blog entry: Giant LEGO Helicopter
Sep 21, 2006, 12:17 PM
Registered User
Tophinater's Avatar
This isn't fair. You guys are doing what I wanted to do for my senior project.

Anyways, what are you guys going to be using for a power plant? Also what do you expect your total solar wattage to be in direct sunlight? And what equipment are you guys going to be using and how much power do you expect it to consume?
Sep 21, 2006, 02:24 PM
De-Brushed user
Awesome project, I am lookin forward to seeing it come together.

I remember seeing your plane spiral in, that was an awesome job getting it flying again for the next day.
Sep 22, 2006, 12:40 AM
Aircraft Designer Guy
AJWoods's Avatar
Quote:
Originally Posted by Tophinater
This isn't fair. You guys are doing what I wanted to do for my senior project.

Anyways, what are you guys going to be using for a power plant? Also what do you expect your total solar wattage to be in direct sunlight? And what equipment are you guys going to be using and how much power do you expect it to consume?
here's our motor:

http://www.maxonmotorusa.com/files/c...f/05_077_e.pdf

Our open circut array voltage is 12v but we'll be opperating at about 70%, which is where the cells are at max eff. Our array's maximum array wattage is 55watts, but the aircraft is specked to cruise at about 4watts. This provides us with a power margin of 13.75, which will allow us to sustain flight when the sun is only about 6.5 degrees above the horizon. Our motor is rated for 15watts which will provide a climb rate of 140 ft/min, not spectacular, but we had to compromise to max out the propulsion systems eff.
Latest blog entry: Giant LEGO Helicopter
Sep 22, 2006, 06:07 PM
Aircraft Designer Guy
AJWoods's Avatar

Core Prep


Today we readied th cores for bagging. We cut the polyhedral angles, trimmed the TE's, smoothed out the LE's, and cut all of the spar pockets. I also started work on the wing joiner blocks, and did a bit of work on the pod.

we have a 3 day weekend so I'll be putting in some long hours on the project.
Latest blog entry: Giant LEGO Helicopter
Sep 26, 2006, 05:46 PM
Aircraft Designer Guy
AJWoods's Avatar

We have Solar Cells.....


...but they are made out of paper . Kidding aside, we have finally found a supplier who can get us A-300's. He will wire and encapsulate the cells, and then we will attach the panels to the wing. Today I cut out 1:1 scale cells to finalize the layout and come up with plans for our cell supplier to work from.

The encapsulated panels will only be about 1mm thick so we shouldn't have any problems with them doing bad things to the airflow. Prof. Drela said that the NG01 airfoil we're using likes to have a turbulator near the LE so the step created by mounting the panels ontop of the glass might actually help out.

As far as wing progress goes, we're almost done with the prep for glassing, all thats left to do is mount the joiner blocks and install wing bolt hardpoints.
Latest blog entry: Giant LEGO Helicopter
Sep 27, 2006, 12:59 AM
Aircraft Designer Guy
AJWoods's Avatar

MPPT Design


Here's a schematic of our maximum power point tracker. Now back to writing my stupid paper for "History and Theory of Architecture," I really dislike the humanities requirement
Latest blog entry: Giant LEGO Helicopter
Oct 07, 2006, 06:55 PM
Aircraft Designer Guy
AJWoods's Avatar

Lots-O-Updates


the plane is starting to come together. Tips are finished, and the center section is ready for bagging tomorrow (we've prebagged the hardpoints, spars, and unicaps to make the actual layup easier). Fuselage bulkheads are also done, and the stabs are framed up and ready for sanding. Its a 4day wekend, so Hopefully the airframe will be done, or almost done by wednesday.
Latest blog entry: Giant LEGO Helicopter


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