Satellite Communications and Space Space Qualified Components Informational

What is the outgassing requirement for RF materials used in space and how is it tested?

Q: What happens if a material fails outgassing requirements?

Options when a preferred material exceeds TML or CVCM limits: (1) Bake-out: pre-heat the assembled component or material at 100-125°C in vacuum for 24-48 hours to remove volatiles before integration with the spacecraft. Many materials pass after bake-out that fail in the as-received condition (moisture and residual solvents are removed). (2) Barrier coating: apply a low-outgassing conformal coating (Parylene C) over the high-outgassing material to slow the volatile release rate. (3) Isolation: physically separate the high-outgassing material from sensitive surfaces using baffles or thermal shields. Place venting ports so that outgassing products exit toward deep space rather than toward antennas. (4) Material substitution: find an alternative material with equivalent RF/mechanical properties that meets outgassing requirements (check the NASA outgassing database for alternatives). (5) Waiver: for some applications, a material that slightly exceeds limits may be accepted with a documented contamination analysis showing that the deposition on critical surfaces remains below performance thresholds.

Q: Is outgassing only a concern in vacuum?

Outgassing rate depends on both temperature and pressure: in vacuum (space): outgassing rate is highest because there is no atmospheric pressure to suppress volatile release. At ground ambient pressure: outgassing still occurs but at lower rates, and volatiles disperse into the atmosphere rather than depositing on nearby surfaces. During launch: the transition from atmospheric pressure to vacuum occurs over 3-5 minutes (fairing jettison). Materials with weakly bonded volatiles may release a burst of gas during this transition. Thermal cycling in orbit: outgassing rate increases exponentially with temperature (approximately doubling for every 20°C increase). Hot surfaces (sun-facing equipment panels at +80°C) outgas faster than cold surfaces. The worst-case contamination scenario is often the first few orbits, when components experience their highest temperatures after months of ambient storage.

Q: How do I find outgassing data for a specific material?

Three primary sources: (1) NASA Outgassing Database (https://outgassing.nasa.gov): over 10,000 materials tested per ASTM E595. Searchable by material name, manufacturer, and generic type. Includes TML, CVCM, and WVR for each entry. (2) ESA ECSS-Q-ST-70-02 database: European equivalent with similar data. (3) Manufacturer datasheets: space-qualified component and material suppliers (Rogers, Gore, Henkel/Loctite, 3M) publish outgassing data for their space-grade products. If no data exists for your specific material: submit samples for ASTM E595 testing at qualified laboratories (NASA Goddard, Jet Propulsion Laboratory, and commercial labs like NTS, EAG). Test cost: $500-1,500 per material sample, with 2-4 week turnaround.

Outgassing is the release of volatile substances (water vapor, solvents, plasticizers, monomers) from materials when exposed to the vacuum and thermal environment of space. For RF systems, outgassed contaminants can deposit on antenna surfaces, optical elements, thermal radiators, and sensitive electronics, degrading performance. NASA ASTM E595 testing measures two parameters: (1) Total Mass Loss (TML): the percentage of mass lost when a material sample is heated to 125°C in vacuum (10^-5 Torr) for 24 hours. Requirement: TML < 1.0%. (2) Collected Volatile Condensable Material (CVCM): the percentage of mass that deposits on a collector plate maintained at 25°C during the TML test. Requirement: CVCM < 0.1%. Materials meeting both criteria are generally acceptable for space use. NASA maintains a database of outgassing test results for thousands of materials (https://outgassing.nasa.gov). RF-specific outgassing concerns: (1) Antenna feeds and reflectors: volatile contamination on reflector surfaces increases surface resistance and scattering, degrading antenna efficiency by 0.1-0.5 dB. On feed windows: contamination creates lossy films that increase noise temperature. (2) Waveguide and coaxial assemblies: outgassing from adhesives, conformal coatings, and cable insulation can deposit on connector interfaces, increasing contact resistance and creating passive intermodulation (PIM). (3) PCB and component assemblies: flux residues, solder paste volatiles, and substrate outgassing must be controlled through proper cleaning (IPA, plasma cleaning) and material selection (low-outgassing solder flux, space-qualified conformal coatings like Parylene C or Humiseal 1A33). (4) Thermal management: outgassed materials contaminating thermal radiators reduce emissivity, causing thermal control issues.

Category: Satellite Communications and Space

Updated: April 2026

Product Tie-In: Space-grade Components, Radiation Testing

Space Material Outgassing Control

Outgassing control is a fundamental space materials discipline that directly affects the long-term performance and reliability of RF payloads. Contamination that accumulates over a 15-year GEO mission can significantly degrade antenna performance and increase system noise temperature.

Parameter	GEO	MEO	LEO
Altitude	35,786 km	2,000-35,786 km	200-2,000 km
Latency (one-way)	~270 ms	50-150 ms	1-20 ms
Coverage per Sat	Full hemisphere	Regional	Local footprint
Handover	None	Periodic	Frequent
Path Loss (Ku-band)	~206 dB	190-206 dB	170-190 dB

Link Budget Allocation

The standard outgassing test: (1) Sample preparation: cut material sample to approximately 200-300 mg. Condition at 50% RH, 23°C for 24 hours to establish a consistent moisture baseline. (2) Test setup: place sample in a heated compartment (125°C) with a collector plate (25°C) positioned to capture volatiles exiting the sample. The entire system is pumped to <7×10^-3 Pa (<5×10^-5 Torr). (3) Duration: 24 hours at temperature and vacuum. (4) Post-test: weigh the sample (mass loss = TML), weigh the collector plate (mass gain = CVCM), and optionally recondition the sample at 50% RH to determine Water Vapor Recovered (WVR). (5) Reporting: TML (%), CVCM (%), WVR (%). The net non-water outgassing = TML - WVR. Interpretation: TML < 1.0% and CVCM < 0.1% is the standard pass criterion. More stringent requirements apply for optical and thermal-critical surfaces: CVCM < 0.01% for Class A optical surfaces. Some programs require micro-VCM (vapor pressure testing at multiple temperatures) for more detailed contamination modeling.

Propagation Effects

Low-outgassing materials approved for space RF: (1) Substrate/PCB: Rogers 4003C/4350B (TML < 0.2%, CVCM < 0.01%), ceramic (alumina, AlN: negligible outgassing), Kapton polyimide (TML 1.0%, CVCM < 0.01% for type HN film). (2) Adhesives: Epoxy Technology EPO-TEK 301 (TML 0.8%, CVCM 0.01%), Hysol EA 9394 (TML 0.6%, CVCM 0.02%), Master Bond EP21TCHT-1 (TML 0.5%, CVCM < 0.01%). Avoid RTV silicones in RF systems (high CVCM from siloxane outgassing, which creates conductive films on antenna surfaces). (3) Conformal coatings: Parylene C (TML 0.1%, CVCM < 0.01%, excellent moisture barrier), Humiseal 1A33 acrylic (TML 0.3%, CVCM 0.02%). (4) Cables: Gore space-grade coaxial cables use ePTFE insulation (TML < 0.01%), PTFE connectors. Standard PVC-jacketed cables are NOT acceptable for space (TML 2-5%, high CVCM from plasticizers). (5) Solder flux: no-clean flux residues must be evaluated; clean all assemblies with IPC-standard cleaning processes and verify with ionic contamination testing (ROSE test or ion chromatography).

Terminal Requirements

For a satellite RF payload, a contamination budget allocates the maximum allowable deposition to each sensitive surface: (1) Antenna reflector: maximum allowable contamination film thickness typically 1-5 nm over the mission life. Thicker films increase surface resistivity and scattering. At Ka-band: a 10 nm hydrocarbon film increases reflector loss by approximately 0.05 dB (acceptable). A 100 nm film: 0.5 dB loss (significant). (2) Feed window: maximum contamination < 1 nm (feed windows are often fused silica or sapphire, which are easily contaminated). (3) Solar cells: contamination reduces power output (1% power loss per μm of film for typical contaminants). Protection: contamination bake-out procedures before launch (bake the satellite at 50-80°C under vacuum for 24-48 hours to drive off volatiles before the thermal blankets and antenna feeds trap them). In-orbit management: position high-outgassing components (battery, wiring harnesses) away from sensitive surfaces, and orient the satellite so that outgassing products flow away from critical optics and antennas.

Performance verification: confirm specifications against the application requirements before finalizing the design
Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture

Orbit Considerations

When evaluating the outgassing requirement for rf materials used in space and how is it tested?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

Common Questions

Frequently Asked Questions

What happens if a material fails outgassing requirements?

Options when a preferred material exceeds TML or CVCM limits: (1) Bake-out: pre-heat the assembled component or material at 100-125°C in vacuum for 24-48 hours to remove volatiles before integration with the spacecraft. Many materials pass after bake-out that fail in the as-received condition (moisture and residual solvents are removed). (2) Barrier coating: apply a low-outgassing conformal coating (Parylene C) over the high-outgassing material to slow the volatile release rate. (3) Isolation: physically separate the high-outgassing material from sensitive surfaces using baffles or thermal shields. Place venting ports so that outgassing products exit toward deep space rather than toward antennas. (4) Material substitution: find an alternative material with equivalent RF/mechanical properties that meets outgassing requirements (check the NASA outgassing database for alternatives). (5) Waiver: for some applications, a material that slightly exceeds limits may be accepted with a documented contamination analysis showing that the deposition on critical surfaces remains below performance thresholds.

Is outgassing only a concern in vacuum?

Outgassing rate depends on both temperature and pressure: in vacuum (space): outgassing rate is highest because there is no atmospheric pressure to suppress volatile release. At ground ambient pressure: outgassing still occurs but at lower rates, and volatiles disperse into the atmosphere rather than depositing on nearby surfaces. During launch: the transition from atmospheric pressure to vacuum occurs over 3-5 minutes (fairing jettison). Materials with weakly bonded volatiles may release a burst of gas during this transition. Thermal cycling in orbit: outgassing rate increases exponentially with temperature (approximately doubling for every 20°C increase). Hot surfaces (sun-facing equipment panels at +80°C) outgas faster than cold surfaces. The worst-case contamination scenario is often the first few orbits, when components experience their highest temperatures after months of ambient storage.

How do I find outgassing data for a specific material?

Three primary sources: (1) NASA Outgassing Database (https://outgassing.nasa.gov): over 10,000 materials tested per ASTM E595. Searchable by material name, manufacturer, and generic type. Includes TML, CVCM, and WVR for each entry. (2) ESA ECSS-Q-ST-70-02 database: European equivalent with similar data. (3) Manufacturer datasheets: space-qualified component and material suppliers (Rogers, Gore, Henkel/Loctite, 3M) publish outgassing data for their space-grade products. If no data exists for your specific material: submit samples for ASTM E595 testing at qualified laboratories (NASA Goddard, Jet Propulsion Laboratory, and commercial labs like NTS, EAG). Test cost: $500-1,500 per material sample, with 2-4 week turnaround.

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