Marimo Labs @ Cambridge Science Carnival

September 21, 2025 – Kendall/MIT Open Space – Cambridge, Massachusetts, USA

Part of the 2025 Cambridge Science Carnival

Hosted each year by the MIT Museum, the Carnival is the capstone STEAM event of the Cambridge Science Festival.

20,000 visitors explored over 100 booths showcasing free STEAM activities hosted by everyone from global corporations to school robotics clubs.

  • 600+ Marimo Labs booth visitors

    "Of all the booths, the water rockets were the best."

    - 11-year-old local expert

  • 270 water rocket launches

    In only 4 hours - on average more than one a minute.

Launches from the most innovative square mile on the planet

Next to MIT, filled with startup incubators and global tech and biotech firms, one subway stop away from Harvard, Kendall Square has been called "the most innovative square mile on the planet."

It's a hard crowd to impress. But we tried (and did!)

Presenting... The Marimo Labs Water Rocket High Jump

Prep: Building rocket bodies and cores

Volunteers prepared rocket bodies and Cores before the Carnival.

Rocket bodies were made from 0.5L PET seltzer bottles and 3D-printed parts. Each bottle was ready for customization with interchangeable nosecones and fins.

The "Core" is the central subassembly of the Marimo Labs launcher that corks each rocket with a water- and air-tight seal. They are made from off-the-shelf O-rings, auto tire parts, and straws. Like the rest of the launcher design, Cores require no adhesives and are reusable.

Build: Attach nosecone and fins

Participants chose from different nosecones and fins that had different masses, shapes, and surface areas. These were made from soft 3D-printed TPU for safety and reusability.

Fill: Pour in water and cork the rocket

A critical decision: how much water should you put in your rocket? More water means more reaction mass but less space for the compressed air that stores the energy.

After loading with water, each rocket was corked with a Core. Cores keep the water and pressurized air in the rocket and interface with the launcher.

Load into launchers and pressurize

A step reserved for our responsible adult volunteers, three rockets are loaded into three launchers. Clamps lock the rockets in place, launch trigger pins are placed, and and hoses are connected to the Cores.

After a safety check and rocket pressurization with a bike pump, rockets are ready on the pad...

3 – 2 – 1... LAUNCH!

With a pull of the launch cord, the retaining pin pulls out, rubber bands pull down a retention collar, clamps open and... blast off!

Thank you to our volunteer partners

  • Kids in Tech (KIT) runs After School Tech Clubs embedded directly in schools and community centers across Lowell, Boston, and Somerville, bringing STEM enrichment to over 8,000 students since 2016. Special thanks to Natty, Adriany, Jazmin, and Safwan.

    Kids in Tech 

  • Macy Makes 3D is a 3D printing shop and YouTube channel based in Lenoir, North Carolina, and a key community manufacturing partner for Marimo Labs.

    MacyMakes3D 

  • And to the many friends that came to lend a hand and make a memorable day for thousands of kids. Looking at you, Anthony, Eleanor, Heather, Brynn, Tyler, Cameron, and Laura. Thank you!

FAQ

  • Safety? Looks crowded!

    Yes! We took special precautions.

    • Low-pressure 15-20 psi launches
    • Small-volume bottles with soft TPU rocket parts
    • Emergency launch abort decompression vents available
    • Lots of responsible adults (some of the type that would save your life in the emergency department) monitoring range safety, wind, and rocket construction.

  • 3 rockets with one pump?

    • We used a custom manifold that pressurized all rockets simultaneously. Ball valves then isolated each rocket so launch timing did not have to be exact.
    • The manifold had its own pressure gauge and emergency decompression vents.
    • Get in touch if you'd like the manifold plans.

  • Do you do kids' birthday parties?

    No, but I'd love to help you plan your own activity. Please get in touch on the site's About page. I'd love to hear from you!

  • Will you be at the Carnival in 2026?

    Sadly probably not - it was incredible fun and we were invited back, but my personal bandwidth is limited.

    I'm looking for educational partner organizations that would be up for running a water rocket booth. I'm happy to provide assistance. Please let me know if interested!

  • Where can I learn more about water rocketry or how to build my own launcher?

    All designs are free. Follow the link below:

    Water Rocketry Home 

  • Photo/Video Credits

    • Launch video: Tara Doherty
    • Pressurize video: Macy Hicks
    • Photos as marked: Michael J. Clarke
    • All others: Ted Liao for Marimo Labs