YOU CAN BUILD A LIQUID-METAL SPACE THRUSTER ON A BENCH THAT PRODUCES REAL, MEASURABLE THRUST
A homemade liquid-gallium field-emission thruster in a vacuum chamber that produced about 15 micronewtons of thrust and about 3,100 seconds of specific impulse.
by Breaking Taps
ScienceWorkshop
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- ●●●●●
- time
- months
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- license not specified
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- repo FINISHED0 stars
●●●●● · months · license not specified · 0 stars · repo FINISHED
WHAT YOU’LL NEED
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COMPAREE VERDICT
This is not a project you download and replicate on a Saturday. It is a filmed build of a liquid-metal field-emission electric thruster - the kind designed to nudge small satellites - with the physics explained as it happens and two months of failed prototypes shown honestly. Breaking Taps pulled gallium off sharpened tungsten tips and glass capillaries with fields in the 7,000 to 10,000 volt range inside a turbo-pumped vacuum chamber, saw the faint blue plasma glow, and then measured it: a Faraday cup and picoammeter for the ion current, and mass loss over a 30-minute run, giving about 15 micronewtons of thrust and about 3,100 seconds of specific impulse, which he himself calls mediocre for this type of thruster. What is missing is a written parts list, a schematic and step-by-step instructions, so you work from the footage. You need to know high voltage, vacuum systems and liquid-metal handling already, or be prepared to learn all three at once. The most likely things to go wrong are the ones he hit: arcing, resistors not rated for the voltage, and gallium that refuses to wet the tip.
IN THE REPO
GOOD TO KNOW
- —This is a filmed build with physics worked through on camera, not a downloadable project
- —No repository, no parts list, no CAD files, no schematic
- —The video shows the build process and measurement but does not include step-by-step instructions
- —Requires high-voltage power supplies, vacuum hardware, and gallium handling
- —No licence information because there is no code or design file to licence
- —This is documentation of a working build, not a how-to guide
Parts to buy
7 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
Creator’s build video
Full build and measurement, physics explained on camera
More builds like this
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Watch the video in full to understand the physics and the setup (This is the only documentation)
- 2.Source a vacuum chamber and pump capable of maintaining the required pressure(Specifics not given in the video)
- 3.Acquire or build a high-voltage supply capable of the field strength needed at the needle tip(The video gives a range of roughly 7,000 to 10,000 volts; use resistors rated for it)
- 4.Prepare a sharpened needle and source gallium(Needle material and sharpening method shown but not detailed)
KNOWN ISSUES
- There is no parts list or schematic — you are engineering this from a video, which means filling in every gap yourself
- High voltage kills, and vacuum chambers implode under atmospheric pressure — this is not forgiving hardware
- Getting a stable emission at the tip is harder than it looks: the creator fought arcs, dying resistors and gallium that would not wet the tip, and the video gives the voltage range (about 7,000 to 10,000 volts) but not exact electrode geometry
- Gallium wets most metals and is difficult to clean up once it spreads
- Measuring thrust needs a Faraday cup and a picoammeter, and specific impulse needs a scale precise enough to weigh the tiny propellant loss over a long run
- If you do not already have vacuum and HV experience, this project will teach you the hard way
Is there a repository or parts list?
No. This is a filmed build, not a downloadable project. The video shows the work and explains the physics, but you have to reverse-engineer the specifics yourself.
What are the actual voltages used?
The video gives the range: an extraction field of roughly 7,000 to 10,000 volts. The creator also burned out resistors that were not rated for 10,000 volts, and found the tungsten spike ran best with a 100 megaohm series resistor and the glass capillary with 50 megaohms. Exact electrode geometry you will have to work out yourself.
Can I skip the vacuum chamber?
No. The ion beam requires vacuum to travel without scattering off air molecules.
Is gallium dangerous?
Low toxicity, but treat it as a lab chemical: wear gloves, it wets and attacks many metals (especially aluminium) and is very messy. Keep it away from anything structural.
What is this used for in real labs?
This exact device is a space thruster for small satellites such as CubeSats. The same sharp-tungsten-tip gallium source is used in focused ion beam microscopes, and the creator notes FIB historically grew out of this thruster work.
Community builds
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Discussion1
FROM THE COMPAREE TEAM
A sharpened tungsten tip, a blob of liquid gallium and ten thousand volts in a vacuum chamber produce real, measurable thrust. Would you push this toward a better thruster, or turn it into a homemade focused ion beam microscope like the creator suggests?
Breaking Taps
Breaking Taps builds and films experimental physics on a bench. This ion source is one of several high-voltage and vacuum projects documented on the channel, showing that advanced physics hardware can be built outside a funded lab.
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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 agoedited
Practical notes from our verification: the only documentation is a single Breaking Taps video. It walks through the physics and the many failed attempts, and it mentions the operating range (an extraction field of roughly 7,000 to 10,000 volts on a gallium-coated tip), but there is no written parts list, no schematic and no step-by-step guide. What the video does measure: a 30-minute run gave about 15 micronewtons of thrust and roughly 3,100 seconds of specific impulse, which the creator himself calls mediocre for this type of thruster. He also explains that ions in such thrusters typically reach 20 to 40 kilometres per second. Replicating this means engineering backward from footage, with a turbomolecular-pumped vacuum chamber, a Faraday cup and a picoammeter in the setup. If you do not already know high voltage and vacuum systems, this is not the project to learn on. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.