Small satellites live and die by mass. Every gram of structure is a gram that can’t be payload — which is why nearly every modern satellite propulsion system stores its gases in a composite overwrapped pressure vessel, or COPV.
This guide explains what a COPV is, how small satellite teams use them, and how to think about sourcing one — whether for ground testing or a custom program.
What Is a COPV?
A composite overwrapped pressure vessel has two components: 1. Liner — a thin inner vessel (aluminum alloy in Type III designs, polymer in Type IV) that seals the gas. 2. Overwrap — continuous carbon fiber filament-wound over the liner, carrying almost all of the pressure load.
The combination delivers working pressures of 300 bar (4,350–4,500 psi) and higher at a fraction of the weight of an equivalent steel tank. That strength-to-weight ratio is exactly what space missions pay for: launch cost is driven by mass.
Where Small Satellites Use COPVs
- Pressurant storage — helium or nitrogen used to push propellant into thrusters.
- Cold-gas propulsion — nitrogen or other gases stored at high pressure, expanded through a nozzle for attitude control and small maneuvers. Simple, cheap, and popular on CubeSats.
- Electric propulsion feed — xenon or krypton stored for ion and Hall-effect thrusters on longer missions.
- Chemical / green propellants — newer propellants need compatible tank materials, which is why liner selection matters.
Type III vs Type IV: Which Do Teams Ask About?
Type III (metal liner + carbon overwrap) is the workhorse: well understood, widely used in ground and industrial applications.
Type IV (polymer liner + full carbon wrap) is lighter and corrosion-resistant, increasingly discussed for demanding environments.
The right choice depends on your gas media, pressure, temperature range, and qualification path — there is no universal answer, which is why talking to the manufacturer early helps.
Ground Testing: Where Stock Cylinders Fit
Before any flight program, teams test on the ground: feed-system checkout, valve and regulator development, pressurization procedures, and university rocketry experiments. For this phase, an off-the-shelf composite cylinder certified to DOT or CE standards for terrestrial pressure-vessel use is a practical, affordable option — and it ships far faster than custom flight hardware.
Note: stock DOT/CE cylinders are terrestrial pressure vessels. They are not space-qualified flight hardware, and flight programs require mission-specific design and qualification.
What to Specify When You Request a Custom COPV
If your program needs something beyond catalog sizes, manufacturers will ask for:
- Water volume and envelope (max diameter and length your structure allows)
- Operating pressure (MEOP) and any proof/burst factors your program requires
- Thread and port configuration (e.g. M18x1.5 standard; specials like M25x2 possible)
- Gas media and temperature range
- Quantity — custom configurations are typically produced in factory batches (for reference, our factory schedules runs of around 200 cylinders), so single prototypes are harder to arrange than batch orders
The more of this you provide up front, the faster you get a feasible quote.
How Acecare Can Help
We manufacture carbon fiber composite cylinders — DOT-certified 6.8L and 9L and CE-certified 12L sizes stocked in California for immediate ground-test and R&D needs — and we develop custom / OEM COPVs with programs that have specific volume, pressure, or interface requirements.
Working on a small satellite, rocket test stand, or university propulsion project? Contact us with your target volume, operating pressure, thread/interface, gas media, and quantity — we’ll review feasibility with our engineers and reply with pricing.
Disclaimer: This article is educational. Pressure vessels must be selected, filled, and operated per applicable standards and your institution’s safety procedures, especially when handling energetic propellants.