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Burning and Suppression of Solids – II (BASS-II)

The BASS-II ’s Quad Chart provides an overview of the study’s technical scope.

Burning and Suppression of Solids – II (BASS-II) utilizes slightly modified Smoke Point In Co-flow Experiment (SPICE) hardware within the Microgravity Science Glovebox (MSG) for observations of burning solid materials on board the ISS.

BASS-II consists of 100 fuel samples and associated igniter wires. There are three categories of samples: flat samples, rod samples, and a section of a large solid sphere. Thin flat samples (10 cm long by 1 and 2 cm wide) yield concurrent or opposed-flow spread rates, limiting flame lengths, and extinction limits. The flat sample materials will include acrylic films and sheets of different thicknesses, and a cotton-fiberglass fabric blend Solid Inflammability Boundary at Low-Speeds (SIBAL) fuel which was previously tested in BASS. The rod samples are made of black or clear acrylic, and will provide solid fuel regression rates and extinction limits for both opposed and concurrent flow. The large solid spherical section, also made of acrylic, will be used to study ignition of thick materials and flame growth over the thick material.

ESA astronaut Alexander Gerst removes hardware for the combustion experiment known as the Burning and Suppression of Solids (BASS-II) from the Microgravity Science Glovebox (MSG) while NASA astronaut Reid Wiseman, flight engineer, looks on.

The important experimental observations from BASS-II with respect to the burning process include flame shape and appearance as a function of ambient oxygen concentration, flow speed, flame spread rate (how fast the flame develops), and flame dynamics (pulsations, oscillations, etc.). With respect to extinction, the critical observations and data are the time to extinction as a function of fuel geometry, flow, and ambient oxygen concentration. The dynamics of the flame before extinction are also important for comparison to the modeling work.

The modeling effort includes:

Science Objectives

Image taken during a BASS-II (Burning and Suppression of Solids – II) experiment flame test.

The Burning and Suppression of Solids –II (BASS-II) investigation examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The BASS-II experiment will guide strategies for materials flammability screening for use in spacecraft as well as provide valuable data on solid fuel burning behavior in microgravity. BASS-II results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

Science Results

BASS-II tests produced data on how ambient oxygen, ventilation, and fuel affect combustion and burning. Theoretical formulas and data on flame spread do not always match in normal gravity. With data from microgravity, scientists determined thin and thick fuel spread rates and a formula for transition from thin to thick fuels. Models predict higher spread rates than observed, so need improvement. Data also allowed calculation of combustion completeness, heat release rates, and fuel-to-oxygen global equivalence ratios and supported theoretical models for quenching boundaries. Results will guide choice of materials for future spacecraft and advance fire detection and suppression in space and on Earth.

Research Overview

Space Applications

A primary goal of BASS-II is improved spacecraft fire safety, improved understanding of combustion in space and how to avoid it. If you’re on a mission far from Earth, a fire can be catastrophic. BASS-II helps engineers select the safest materials and improve firefighting methods on future space missions.

Earth Applications

In outer space, fuels burn as oval balls rather than with an upward pointed cone flame as they do on Earth. This simpler combustion process enables researchers to evaluate computer models of fuel burning. These models can then be used to more accurately study flames on Earth, such as in wildfires, building fires, energy recapture from waste recycling, and other combustion problems.

Operational Requirements and Protocols

BASS-II is conducted inside the sealed MSG work volume. The crewmember is involved throughout the experiment to load fuel samples, adjust nitrogen gas (GN2) concentration in the working volume vitiation of the working volume, initiate tests, ignite the fuel, monitor and record data, exchange fuel samples, and replace the igniter. Forty-one test samples will be burned in a variety of flow conditions for a total of 89 test points.Data is downlinked via video during or immediately after each flame test. Digital photos are downlinked after selected flame tests for ground confirmation before proceeding. BASS-II testing session must be conducted during periods when no major reboost or docking procedures are underway on the International Space Station (ISS).

The crewmember installs the BASS-II hardware in the MSG work volume. The BASS-II hardware consists of a small flow duct with an igniter and a small nozzle along with exchangeable fuel samples. During BASS-II operations a fan produces a co-flow of air through the duct. An anemometer is used to measure the actual flow rate. The crewmember adjusts the airflow from 5 to 50 cm/s. Nitrogen vitiation of the working volume is then initiated using station GN2 at a flow rate of up to 500 cc/min for a prescribed time. The flame is ignited and allowed to burn for about a minute. A radiometer measures flame output. The crewmember conducts each test. They install the correct fuel assembly and set the air flow rate through the duct before igniting the flame. When the flame is ignited, the crewmember allows some time for the flame to stabilize then adjusts the flow of nitrogen suppressant through the nozzle until the flame goes out. After the test, the crewmember turns off the nitrogen flow and prepares for the next test. The science team on the ground monitors the video downlink to assist the crewmember in determining any peculiar flame behaviors and reviews the sensor data overlaid on the video image. Upon completion of the tests the crewmember stows the hardware and the stored images and data are returned to Earth for analysis.


Contact Information

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