MOJAVE SPHINX: AN OPEN-SOURCE LIQUID-FUEL ROCKET
A fully open amateur liquid-bipropellant rocket with a free build guidebook — schools and university teams are actually launching it.
RocketryAerospace
- difficulty
- ●●●●●
- time
- a serious project
- license
- GPL-3.0
- repo
- repo ACTIVE28 stars
●●●●● · a serious project · GPL-3.0 · 28 stars · repo ACTIVE
WHAT YOU’LL NEED
- 3D printer + filament — printable parts — files are in the repo
Partner
COMPAREE VERDICT
This is the most advanced project in our catalog, and we're presenting it with real caution: Mojave Sphinx is a genuine open-source amateur liquid-bipropellant rocket, published by Half Cat Rocketry with a free, complete build-and-launch guidebook. The engineering openness is remarkable — SolidWorks CAD, STEP and STL, flat-cut DXF parts, OpenRocket simulations, and 22+ registered builds by schools and university teams. But this is not a maker weekend: it uses a nitrous-oxide oxidizer and fuel under pressure, produces serious thrust, and reaches thousands of feet. It demands a proper launch range, the right permits and permissions, experienced mentorship, and strict safety procedure — Half Cat is explicit that you build and fly at your own risk. Admire it, learn from the guidebook, and only pursue it within an experienced, authorized rocketry context.
IN THE REPO
NOT IN THE REPO
- —Full open-hardware package: SolidWorks CAD, STEP + STL, DXF flat-cut parts, OpenRocket simulation and a complete PDF guidebook
- —Licensed GPL-3.0
- —Serious hazards: nitrous-oxide oxidizer and fuel under pressure, high thrust — this is advanced amateur rocketry
- —Documented by 22+ registered builds at schools and universities
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the project page (overview and the free guidebook)
- 2.Study the guidebook first (HCR-5100 build/integration/launch — read fully before anything)
- 3.Review the CAD and simulations (SolidWorks, STEP/STL, OpenRocket)
- 4.Find an experienced, authorized range (never launch without supervision and permits)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- This is advanced amateur rocketry — nitrous-oxide oxidizer and fuel under pressure, high thrust; it demands experience, permits and a proper range
- Half Cat explicitly disclaims liability — you build and fly at your own risk
- No verified demo video — the free guidebook is the real reference
- Not a project to attempt solo or without experienced mentorship
Is this really a liquid-fuel rocket you can build?
Yes — it's a genuine open-source amateur liquid-bipropellant rocket with a complete free guidebook, and 22+ teams (including schools and universities) have registered builds. But it requires serious experience and authorization.
Why is it flagged so heavily?
It uses a nitrous-oxide oxidizer and fuel under pressure and produces high thrust, reaching thousands of feet. That's real hazard territory needing a proper range, permits and supervision.
What's actually published?
A full open-hardware package: SolidWorks CAD, STEP/STL, flat-cut DXF parts, OpenRocket simulations and the HCR-5100 guidebook, under GPL-3.0.
What does it cost?
Band $$ — remarkably cheap for a liquid rocket. The guidebook has current details.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
More than 22 registered teams — including schools — are building this liquid-bipropellant rocket from a free guidebook. Is open-sourcing a nitrous-fed engine a great equalizer or a liability nightmare?
Half Cat Rocketry
Published a complete open-source amateur liquid rocket with a free build-and-launch guidebook, aiming to make liquid rocketry approachable for experienced, safety-minded teams — and schools are building it.
DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo ago
What stood out when we verified the claims: this isn't a paper project — 22-plus builds are formally registered, several at schools and universities, all working from the free HCR-5100 guidebook. There's deliberately no flashy demo video; the guidebook itself is the reference, alongside SolidWorks CAD, DXF flat-cut parts and OpenRocket sims under GPL-3.0. Anyone here flown amateur liquids and can compare it to solids culture?