Continuing from the previous article, we will see some of the cool and important experiments that have been carried out at ISS (and couldn’t have been possible elsewhere).
Fire: Ignite and Extinguish
The physics of flames in microgravity is quite interesting. The “flame extinguishment study” in a designed facility whereby tiny droplets of fuel, which form into spheres under microgravity, are ignited. Flames on Earth assume their familiar shape because gravity-driven convection results in an up-draught of air, drawing the burning mixture of fuel and gas upwards. In microgravity, there is no updraught and so a flame assumes a diffuse spherical shape around the combustion source. Further, the yellow color of a flame is produced by the incandescence of tiny soot particles. Soot forms from incomplete burning of the fuel and is a pollutant.
In microgravity, the combustion of a fuel is more complete and hence more efficient. A candle flame that would appear yellow on Earth actually burns with a blue color in microgravity and produces much less smoke. This kind of research enables the study of soot formation processes which have negative impacts on the environment and human health, and how droplets of fuel in a combustion engine transition from a liquid to a gas as they burn. This may one day lead to more efficient designs for combustion engines on Earth.
Trying out a 13-mile space tether
Two different shuttle missions — Atlantis’ STS-46 in 1992 and Columbia’s STS-75 in 1996 — took a crack at deploying a satellite, then dragging it through space connected by a 13-mile-long (21-kilometer) conducting tether.
The experiment, called the Tethered Satellite System (TSS), was a joint effort between NASA and the Italian space agency. The idea was to show that tethered satellites could generate electric current as they cruised through Earth’s magnetic field.
During STS-46, the tether unspooled just 840 feet (256 meters) from Atlantis before the reel jammed. Four years later, 12.2 miles (19.7 km) of cable were released before the 0.1-inch (0.25 centimeter) tether snapped, sending the probe shooting away into a higher orbit.
Though neither attempt was 100 percent successful, the TSS belongs on this list for its scale and ambition alone. And the 1996 experiment did return some interesting results. Before the tether snapped, the TSS had been generating 3,500 volts and up to 0.5 amps of current, according to NASA officials.
Space roses smell different
It sounds like some sort of symbolic or ceremonial gesture: The shuttle Discovery carried a single rose to orbit on its STS-95 mission in 1998.
But there was science, and business, behind the move. The company International Flavors and Fragrances (IFF) wanted to see how microgravity altered the sweet and familiar scent of a rose — and if a new perfume component might come out of the experiment.
So IFF sent a miniature rose plant up, and shuttle astronauts sampled its volatile oils, which carry the essential odors of the flower. It turned out that the space rose produced fewer volatiles than its counterparts did back on Earth. And, more importantly, its overall fragrance was entirely different.
IFF commercialized the space rose odor, which has since been incorporated into “Zen,” a perfume put out by the company Shiseido Cosmetics. NASA flew another rose on a space shuttle in 2007, but that flower was destined for the annual New Year’s Rose Parade in Pasadena, Calif., not a perfume.
The fragility of the human body
The effects of the space environment on the human body during long-duration spaceflight are of significant interest if we want to one day venture far beyond the Earth. A crewed journey to Mars, for example, may take a year, and the same time again for the return leg. Microgravity research on the ISS has demonstrated that the human body would lose considerable bone and muscle mass on such a mission. Mitigation technology, involving the use of resistive exercise devices, has shown that it is possible to substantially alleviate bone and muscle loss. Coupled with other studies into appropriate nutrition and drug use, these investigations may lead to improvements in the treatment of osteoporosis, a condition affecting millions of people across the globe.
