ISO 15859-3:2004

Overview

ISO 15859-3:2004 - "Space systems - Fluid characteristics, sampling and test methods - Part 3: Nitrogen" defines composition limits, sampling plans and test methods for nitrogen used in space systems. The standard covers both gaseous (Type I) and liquid (Type II) nitrogen across grades for purging/pressurizing, crew breathing and specialized uses. It applies to fluids at the flight-vehicle interface or storage points and is intended to verify nitrogen purity before entry into launch vehicles or spacecraft.

Key topics and technical requirements

• Composition limits: Specifies permitted impurity levels (water, total hydrocarbons, oxygen, hydrogen, argon, CO₂, CO, aromatic/halogenated/chlorinated hydrocarbons, particulates and total impurities) and examples of nitrogen purity requirements (ranging up to >99.99% for higher grades).
• Types and grades: Distinguishes Type I (gaseous) and Type II (liquid) nitrogen and multiple grades (e.g., Grade A for purging/pressurizing, Grade B for crew breathing).
• Sampling plan: Requires an approved sampling plan specifying sampling points, procedures, frequency, sample size and responsibilities. Sampling is typically at storage or flight-vehicle interface and is performed annually or per agreement.
• Sampling methods: Describes safe methods for gaseous sampling (simultaneous filling, withdrawal without intermediate regulators, or direct connection to analyzers) and for liquid sampling (collecting representative liquid and vaporizing for analysis).
• Test and verification methods: Allows direct and indirect purity measurement. Accepted analytical techniques include gas chromatography (e.g., 5Å zeolite columns), mass spectrometry, flame‑ionization detectors for total hydrocarbons, dew-point and sorption hygrometers for water, electrochemical/paramagnetic/zirconia oxygen analysers, and other calibrated detectors.
• Rejection rules: Fluids failing verification tests must be rejected; disposal and corrective actions are determined by the customer.
• Safety: Notes asphyxiation risk of gaseous nitrogen and severe cold injury from liquid nitrogen - handling and storage safety required.

Applications

• Pre-launch verification of nitrogen used for purging, pressurizing, thermal systems, and ECLSS (environmental control and life support systems).
• Quality control at spaceports, launch sites, ground support equipment, propellant and pressurant supply chains.
• Supplier acceptance testing and contractual verification between nitrogen suppliers and launch/spacecraft integrators.

Who should use this standard

• Space agencies, launch service providers and prime contractors
• Ground support and launch-pad engineers
• ECLSS and life-support system designers and test labs
• Gas suppliers, quality assurance teams and analytical laboratories performing gas purity testing

Related standards

• Other parts of ISO 15859 (Part 1: Oxygen; Part 2: Hydrogen; Part 4: Helium; Parts 5–13 for other fluids)
• ISO 9000 (quality management vocabulary and fundamentals)

Keywords: ISO 15859-3, nitrogen purity, space systems, sampling and test methods, gaseous nitrogen, liquid nitrogen, launch vehicle, gas chromatography, mass spectrometer, dew-point analyser.