How College Students Built a Satellite With AA Batteries and a $20 Microprocessor (popsci.com) 55
With all the space junk cluttering our orbits, Popular Science writes, "Lowering costs while also shortening satellite lifespans is important if space exploration and utilization is to remain safe and viable.
"As luck would have it, a group of students and researchers at Brown University just made promising headway for both issues." Last year, the team successfully launched their breadloaf-sized cube satellite (or cubesat) aboard a SpaceX Falcon 9 rocket for the comparatively low production cost of $10,000, with a dramatically shortened lifespan estimated at just five years. What's more, much of the microsat was constructed using accessible, off-the-shelf components, such as a popular $20 microprocessor powered by 48 AA batteries. In total, SBUDNIC — a play on Sputnik as well as an acronym of the students' names — is likely the first of its kind to be made almost entirely from materials not specifically designed for space travel.
Additionally, the group attached a 3D-printed drag sail made from Kapton film that unfurled once the cubesat reached orbit roughly 520 kilometers above Earth. Since tracking began in late May 2022, the students' satellite has already lowered down to 470 kilometers — well below its fellow rocketmates aboard the Falcon 9, which remain around 500 kilometers high.
"As luck would have it, a group of students and researchers at Brown University just made promising headway for both issues." Last year, the team successfully launched their breadloaf-sized cube satellite (or cubesat) aboard a SpaceX Falcon 9 rocket for the comparatively low production cost of $10,000, with a dramatically shortened lifespan estimated at just five years. What's more, much of the microsat was constructed using accessible, off-the-shelf components, such as a popular $20 microprocessor powered by 48 AA batteries. In total, SBUDNIC — a play on Sputnik as well as an acronym of the students' names — is likely the first of its kind to be made almost entirely from materials not specifically designed for space travel.
Additionally, the group attached a 3D-printed drag sail made from Kapton film that unfurled once the cubesat reached orbit roughly 520 kilometers above Earth. Since tracking began in late May 2022, the students' satellite has already lowered down to 470 kilometers — well below its fellow rocketmates aboard the Falcon 9, which remain around 500 kilometers high.
Gumption (Score:3)
Re:Gumption (Score:5, Informative)
Typical sized batteries have always been used. The issue is they are unreliable. I think we put ours through many cycles of charges to weed out the defective batteries, but it was still a risk a bank would fail. It is a concern as small risks and errors are what doom. Like a fuse.
What determines success is it make it into orbit in one piece and is able to at least begin the science. When it is said failure is not an option, it is talking about catastrophic failure. If they can collect data, that is a success.
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How did you deal with the extreme temperatures? I haven't looked into it much, but it seems like the batteries would perform poorly in the cold and suffer degradation in the heat, unless quite well insulated.
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From TFA:
including an Arduino processor and AA Energizer batteries
.
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It keeps orbiting, and orbiting, and orbiting....
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Does it have a transmitter?? I didn't see any reference to that in the articles.
I get the impression that it's simply being tracked by radar from the ground and that all it actually did was unfurl a Kapton sail to provide proof of concept that this is a way to help de-orbit satellites in LEO.
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Re:Wait (Score:4, Informative)
Another site lists this as the radio:
TTC
Tracking, Telemetry and Control
Radio communication will be achieved with a Ham radio-based Arduino add-on like the Hamshield Mini shown to the right. A long strand of nickel titanium wire will be used as the antenna. This solution is widely used among 3U CubeSats.
https://sbudnic.space/about [sbudnic.space] [sbudnic.space]
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Does someone know if it was ever active?
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So what’s stopping you?
Re:Wait (Score:5, Funny)
So what’s stopping you?
Everything I've ever tried sending into orbit using common household items comes crashing back down into the neighbor's yard. Achieving orbital velocity must be like rocket science, or something.
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They didn’t build a rocket, they hitched a ride on one. They only built the cubesat which at this point is not a challenge since designs for them with step by step instructions can be found all over the internet. Objectively speaking a cubesat in itself is not a major technical achievement.
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-grunt-
here
https://sbudnic.space/about [sbudnic.space]
Tracking, Telemetry and Control at
https://engineering.brown.edu/news/2022-05-16/sbudnic-satellite-launch [brown.edu]
More I read, the more fluffy it sounds for all the adults involved.
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Probably the reluctance to spend $100k or whatever it is for a Falcon 9 seat to toss a box of middle school science fair hardware out the window?
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Oh, I dunno...maybe the fact they got a free ride into space, which isn't available to most people?
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They probably bought a common off the shelf cubestat frame, that's half the money gone already. The kill switches are probably certified/standardized too, so a couple more k$.
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PS. looking around you can DIY the kill switches, but the qualification testing (and pre-testing) will still cost a ton of money to perform.
Re:Wait (Score:4, Informative)
The $20 is likely for the whole microcontroller board (in this case an Arduino), not just the CPU.
The Arduino uses an AVR processor. If you underclock it, it can tolerate a significant undervoltage and remain reliable. To the point that if you want to keep things really simple, you can power one from an un-regulated 18650. That also makes it more power efficient since you avoid losses from the regulator. The I/O pins arte equally forgiving if input voltages aren't as close to spec as you might like. Notably, the environment in low orbit can be unfriendly to electronics, so the larger features on the AVR die can be a plus. Then there's the fact that the ram, and flash are built in to the chip.
So, if the battery pack is wires as 3S16P (I suspect it is) and unregulated, it will keep the processor running for quite a while.
Cortex M is great, but it isn't right for all applications.
Re:Wait (Score:5, Informative)
You can buy rad-hardened AVRs. The part number has an additional S, so ATmegaS128 instead of ATmega128. The "S" means "Space".
The main (only?) difference is the use of depleted boron-11 as a semiconductor dopant rather than conventional boron (~20% boron-10).
Boron-10 has a very high neutron cross-section, which makes it more likely to cause SEUs. Boron-11 has a tiny neutron cross-section.
Boron enriched in Boron-10 is used in nuclear reactor control rods because it sucks up neutrons so readily. The leftover "depleted boron" is used in rad-hardened semiconductors.
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You can buy rad-hardened AVRs.
But they didn't. They grabbed a stock standard Arduino Uno. AVRs are also NOT available rad-hardened off the shelf. They are special order items that you can't get for the $20 much less get the entire board for that.
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It will cost $50. It is special order, but it's not like they have to go fab one for you, it's just that the usual suspects don't keep them in inventory.
Fortunately you can do your development on a plain old ATmega128 while you wait. It wouldn't be hard at all to swap out the processor on an Arduino Nano or a clone.
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It's PR for aerospace university departments, university professors tend to be pretty good at PR. It's almost certainly economically rational.
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This thing could probably die before it even reaches orbit and it would not make a difference. It is a stunt, nothing else.
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Saying that regular batteries dislike cold is an understatement.
Pack them in an aerogel insulator.
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OTOH, insulation is fairly easy since it will be operating in a vacuum. The hard part is getting the amount of insulation right so they neither cook nor freeze.
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I'm scratching my head at the math. The really expensive part about most communications satellites is not the satellite itself (unless it's something very, very cutting edge or very large for some other reason). It's the part where you lift it out of planet's gravity well. The amount of energy necessary is massive, and systems that can generate this energy and survive are very expensive and complex. I.e. rockets. There's a reason why we tend to mention "rocket science" as a stereotypical example of somethin
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What you're missing is that commercial launches typically include inert ballast. If you ask nicely, part of that ballast can be your cubesat. It's not a deluxe launch package, they just dump your cubesat out when the payload deploys. It ends up where it ends up.
Don't tell DeSantis (Score:5, Funny)
Additionally, the group attached a 3D-printed drag sail
Known in Florida as an "air brake device", because we can't expose students to drag. /s
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Don't forget Tennessee where our Governor "General Lee" put a state ban on public drag shows "cause of chirlen being exposed to overtly sexual acts" but when he did it, it was perfectly fine "good natured fun"
Can someone tell me... (Score:2)
...where I can buy AA batteries that last for five years?
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Haha.. buried the lead there!
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Lots of places if the current draw is in the range of microamps.
More info at their website (Score:3)
There is considerably more detail on the project website in case anyone is interested;
https://sbudnic.space/about [sbudnic.space]
The document describing the electrical system says the AA battery can deliver 3350 mAh, and they have 30 of them. The Arduino pulls 20 mA and the radio draws 210 mA, but they will take just 5 pictures per day for transmission so the draw for that is intermittent. They say the batteries will last about 66 days, nowhere near 5 years.
48 AA batteries? (Score:2)
Each AA battery weighs approximately 23 grams. Therefore, 48 AA batteries would weigh about 1104 grams (48 x 23 = 1104).
A custom lithium-ion battery pack that provides the same voltage and capacity as the 48 AA batteries could weigh around 200-300 grams.
So, if we subtract the weight of the custom battery (let's say 250 grams) from the weight of the 48 AA batteries (1104 grams), we get a weight difference of approximately 854 grams.
Therefore, by replacing 48 AA batteries with a single custom battery, one cou
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Li-ion is a pretty poor choice for space applications with no solar panels due to internal resistance climbing rapidly as temperature drops as well as fairly high self discharge rate.
Frankly one thing where alkaline is actually very much at the top of the pile among both primary and secondary cells is self-discharge rate. There are very few battery technologies that are as good as alkaline batteries at just holding their charge over long period of time.
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alkaline is actually very much at the top of the pile
Hahahahah! Nice one, Centurian!
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Maybe they aren't alkaline AAs? SAFT Lithium-Thionyl Chloride AA cells are 2600mAh @ 3.6V and 17 g. That's pretty high. But the original article from 2022 specified Energizer batteries and I don't think they make Li-SOCI2 cells. They do make Li-FeS2 cells, AA is 3500 mAh at about 1.6 V and 15 g.
Still, that is about 370 Wh/kg for AA Energizer batteries. What would be so much better? 2170 li-ion cells are only about 270 Wh/kg.
The name could have been worse (Score:2)
"SBUDNIC - a play on Sputnik as well as an acronym of the students' names"
Well, it could have been NUBDICS.
AA batteries in space? (Score:2)
3d printed kapton? (Score:2)
How the heck did they 3d print Kapton, a polyimide? I thought Kapton was a thermoset?
Re: 3d printed kapton? (Score:2)
I'm sure the article used "3D printed" as a buzzword/clickbait. Maybe the frame the kapton is attached to is printed but not the foil itself.
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They could do it like this [wikipedia.org], but I suspect they actually printed the frame and attached pre-formed kapton film.
The entire cost in in LIFT (Score:2)
This is stupid. I can make a satellite for free, just go outside and find a rock. The entire cost is the lift to orbit. If a 100k battery can shave a little weight off those AA off the shelf batteries, you save money.
This sounds like someone donated the lift to these students, so they made stupid and inefficient design choices.