STS-94 Space Shuttle Mission
Droplet Combustion Experiment Results
In April and July 1997, the first isolated, space-based droplet combustion experiments were conducted on Microgravity Science Laboratory-1 aboard the Space Shuttle Columbia during the STS-83 and STS-94 missions. In the Droplet Combustion Experiment (DCE), isolated n-heptane droplets were deployed into a helium/oxygen oxidizing environment and ignited by a pair of hot-wire igniters. Tests were conducted over a wide range of initial droplet diameters (1.5 to 5 mm), oxygen mole fractions (20% to 50%) and pressures (0.25 to 1.0 atm). The STS-94 mission lasted for 16 days starting on July 1, 1997.
Prof. Forman A. Williams of the University of California at San Diego is the Principal Investigator of the DCE Experiment. Prof. Frederick L. Dryer of Princeton University is the co-Investigator and Dr. Vedha Nayagam of Analex Corporation is the program scientist. During the 16 day mission, Prof. Anthony Marchese worked along with Williams, Dryer and Nayagam as a fellow member of their science team at the Payload Operations Control Center at Marshall Space Flight Center in Huntsville, AL.
The figure above shows the test hardware during an experiment on DCE. The hardware is virtually identical to that which has been used previously in drop tower experiments conducted by Prof. Marchese. The previous experiments were conducted in the 2.2 second drop tower at NASA Lewis Reearch Center.
Prior to the mission, Marchese discussed the implications of his research with Dan Fiorucci of Channel 17 WPHL in Philadelphia. Marchese explained that the droplet combustion research conducted aboard STS-94 can have immediate impact in terms of fire safety of flammable liquids aboard manned orbiting spacecraft. The potential tragedy associated with a fire aboard a manned spacecraft was foreshadowed by the recent fire aboard the space station Mir.
In terms of the long-term payoff, the experimental results are important in increasing the understanding of the way liquid fuels burn. Today, despite efforts to develop and utilize renewable energy sources, 85% of all energy consumed in the U.S. is derived from the combustion of fossil fuels. Moreover, the combustion of liquid petroleum-based fossil fuels accounts for 39% of all energy consumption and an astounding 97% of energy consumption in the transportation sector! As we continue to rely on these fuels as a major energy source, it is of paramount importance to maximize the efficiency of the devices which burn these fuels. The most effective way to achieve this goal is through a fundamental understanding
of liquid vaporization and combustion processes. The simplest way to examine the underlying physical phenomena of liquid fuel combustion is to study the spherically symmetric combustion of a single, isolated liquid fuel droplet. At right, Prof. Marchese explains to an NJN reporter how the weightless environment aboard the space shuttle results in a perfectly spherical flame surrounding the spherical fuel droplet.
The Droplet Combustion Experiment, conducted aboard Space Shuttle Columbia as part of the first Microgravity Science Laboratory on shuttle flights STS-83 and STS-94, represents the first space-based, isolated droplet combustion experiment.
On
July 1, 1997 at 2:02 p.m. EST, the Shuttle Columbia, carrying seven astronauts,
blasted off from Launch Pad 39-A at the Kennedy Space Center to return
to orbit to complete a microgravity science mission cut short in April
by a fuel cell problem.
Commander Jim Halsell, Pilot Susan Still,
Mission Specialists Janice Voss, Mike Gernhardt and Don Thomas and Payload
Specialists Roger Crouch and Greg Linteris lifted off at 2:02 p.m. EST,
just 12 minutes behind schedule to enable forecasters to make a final check
of clouds near the launch site.
Spacelab missions provide a laboratory on the Shuttle where scientists in space (Payload Specialists) can work with and be guided by a team of flight controllers and scientists on the ground. The team on the ground, called the Cadre, works in the Payload Operations Control Center (POCC) in Huntsville, Alabama. The Cadre analyses experiment science and hardware operations, monitor onboard system performance, and make adjustments to the plan (called a "timeline") for payload operations.
In the photo at the left, science team members Prof. Fred Dryer of Princeton University, Prof. Marchese and Dr. Vedha Nayagam of NASA Lewis Research Center are monitoring DCE activities over the communications loop. Professor Dryer is the co-Investigator of DCE and Dr. Nayagam is the Program Scientist. Prof. Forman A. Williams of the University of California at San Diego is the Principal Investigator of the Experiment.
Spacelab missions, such as STS-94, provide a laboratory on the Shuttle where scientists in space (i.e. astronauts) can work on a variety of experiments. At left, Payload Specialist Greg Linteris and Mission Specialist Don Thomas are shown executing experiments in the Spacelab module.
The Spacelab is a reusable laboratory designed to allow scientists to perform experiments in microgravity conditions while orbiting Earth. It was developed by the European Space Agency (ESA) and is mounted inside the cargo bay of NASA's Space Shuttle. Carried to orbit in the Shuttle, Spacelab provides a versatile laboratory where scientists conduct research in many different fields of science.
