Orbital Flush

What?

Orbital Flush is exactly what it sounds like: a toilet on Earth that flushes whenever an astronaut aboard the International Space Station (ISS) flushes in space. It’s mounted on a rotating platform that tracks the ISS as it orbits Earth, making sure it’s always pointing… uh… in solidarity.

Yes, it’s dumb. Yes, it’s perfect.

(Also: Chris Hadfield liked our tweet)

CHRIS HADFIELD LIKED MY TWEET

AAAAAAAAAA https://t.co/Sv0u3u0FHY pic.twitter.com/Ap5O6rkHrJ
— kai 🥰 (@kaisoapbox)
January 29, 2025

Peak human achievement? Possibly.

Why?

It all started with this extremely cursed idea:

A Discord chat screenshot discussing a GitHub project called "pISSStream," a macOS menu bar app that shows in real-time how full the International Space Station’s urine tank is. The first message shares a GitHub link with a preview of the repository. Several users react with emojis and comments, including a joke about data updates and a humorous mention of "issomeonepeeinginspace.com." Calvin comments imagining linking the app to a smart toilet that flushes every time someone on the ISS flushes, with laughing emojis reacting.

Shoutout to pISSStream, the macOS menu bar app that displays real-time urine tank levels from the ISS, because humanity’s reach exceeds its grasp, but our curiosity about astronaut pee is limitless.

Naturally, I saw this and thought: What if a real toilet flushed whenever the astronauts flushed?

Some ideas are too good to ignore.

How?

ISSLive! (Gone but not forgotten)

Back in 2011, NASA released a web/mobile game called ISSLive! that let you play around in a simulated Mission Control. You could poke around real telemetry, including, wait for it, the live urine tank levels. Truly, the golden age of space data.

Sadly, ISSLive was axed in 2015 (RIP), but the urine data stream lives on. Because NASA priorities.

The key screen? The third page of the ETHOS’s life support console where you can see the urine tank stats, updated in real-time:

A diagram titled "ETHOS Regenerative Life Support Display" showing the flow of water and oxygen recycling systems on the International Space Station. The left section highlights the Urine Processor Assembly (UPA) in a red box, displaying a urine tank level at 49% and a state of "STANDBY." Below it is the Oxygen Generator Assembly (OGA) showing an O₂ production rate of 2.76 kg/day. On the right is the Water Processor Assembly (WPA) with wastewater tank (77.06%), clean water tank (56.71%), and processor state "STANDBY." The diagram includes NASA logos and navigation options for live data, operations, and resources.

We wired everything up to track any jump in urine tank levels, triggering a flush on Earth. A Raspberry Pi does the brainwork; a motor keeps the toilet pointed at the ISS, thanks to orbital data from NORAD (North American Aerospace Defense Command). When it’s flush time, a beefy stepper motor yanks a chain inside the toilet tank, completing the sacred Earth–Space toilet ritual.

Which tank are we even talking about?

Turns out there are at least 3 toilets up there, plus a whole separate Urine Processor Assembly (UPA) tank.

We went deep down the rabbit hole reading NASA tech docs (highly recommended bathroom reading):

Thankfully, someone from Mission Control confirmed that, yes, it’s the UPA Wastewater Storage Tank Assembly (WSTA) we’re seeing. You know it’s real when the experts chime in:

@kaisoapbox

ISS Electrical (SPARTAN/PRO) here. Current ETHOS Expedition/Increment Lead tells me that it IS the UPA tank, called the Wastewater Storage Tank Assembly (WSTA). To confirm, I plotted UPA WSTA and verified the same value at the same time as your screenshot. pic.twitter.com/lTVR6awEzv
— Stephen Patlan (@StevePatlan)
January 10, 2025

Thanks, Stephen ❤️!

Build

Prototype 1: The Toilet Awakens

Four young adults—Bill, Kai, Calvin, and Chloe—pose indoors in front of a toilet mounted on a small platform draped with gray fabric. They are smiling and casually dressed; Chloe, on the far right, is flashing a peace sign. The background features a classroom setting with large blackboards and blue accent lighting along the wall. The atmosphere is playful and lighthearted.

We debuted Prototype 1 (aka: “it flushes, but it doesn’t turn”) at the Atelier Showcase in January 2025.

We hit up Home Depot for the cheapest toilet that still looked presentable (sorry, fancy Toto models). Bonus: we checked they stocked the same model in Waterloo, because, let’s face it, flying a toilet cross-country is not the dream.

Prototype 2: Spin Me Right Round

Pro Tip: Always secure the toilet tank before spinning the toilet

By March, we had a spinning version ready to flex at the Symposium. We CNC’d the whole platform in Vancouver, thanks to a heroic effort from a CNC router, plywood, and way too much last-minute caffeine. We also sprinted into Home Depot minutes before closing so many nights in a row that the lady at the door started waiting for us. (Shoutout to her for the moral support—and the side-eye.)

Symposium Build: Oh God, Logistics

We thought we’d just bring the electronics to Waterloo and CNC everything locally. It was actually cheaper to ship the wood across the country lmao. Lesson learned.

Huge thanks to Sienci Labs (pronounced C-N-C) for letting us take over their CNC router—Scott even moved his day off to help us get everything cut at their HQ. Absolute legends (Scott and Andy 💖).

Also: the Canadian TSA found my giant stepper motor very sus:

A close-up of an item inside a cardboard box, wrapped in bubble wrap and sealed with security tape. The tape reads "Inspected / Inspecté" in red text and features the CATSA (Canadian Air Transport Security Authority) and ACSTA logos, which include a maple leaf and a stylized shield. The tape is slightly crumpled, indicating the package was opened and re-sealed after inspection.

A CATSA (Canadian Air Transport Security Authority) notice form titled "Notification of Checked Baggage Inspection," printed in both French and English. The document explains that the passenger’s bag was inspected for security reasons and provides instructions if items were removed. One checkbox is marked: "Search conducted. No item removed." Other boxes for "Dangerous goods removed" and "Illegal item removed" are unchecked. Handwritten notes include baggage tag reference number "CS47M9," airport code "YVR," checkpoint location "DL3," and a date stamp of March 12, 2025. The bottom of the form reads "For Internal Purposes Only."

Shoutout to Home Depot, Taobao, Amazon, and all the plywood sheets that gave their lives for this cause.

Thank you ❤️

Special shout-outs to the legends who made Orbital Flush happen:

Kai (kaisoapbox.com) - the glue of the whole project: assembling every prototype, wrangling logistics, and firing off the tweets that got Chris Hadfield’s attention. Peak team player.
Bill (billpan.info) - for helping build and test Prototype 1 and going above and beyond at the booth on the day: helping assemble the final setup and explaining to curious onlookers exactly what was going on.
Chloe (chloenguyen.info) - for helping build and test Prototype 1 (the “please just flush” stage).
Braeden (eng.brhall.dev) - for being the logistics MVP, helping hauled all that plywood from Home Depot to Sienci Labs. (A true friend is someone who helps move lumber.)
Scott and Andy from Sienci Labs (sienci.com) - for giving us CNC router access and serious workshop support. Extra love to Scott, who moved his day off to help us cut everything at their HQ. Legends.

What next?

I mean… Sotheby’s? Christie’s? There’s gotta be some billionaire out there who wants a space-synced toilet. (Honestly, have you seen what some of these art people buy?)

Or maybe we’ll just keep flushing for fun.

More info

Kai is cooking up a much longer, much more chaotic write-up with extra behind-the-scenes details. You can read that over here.