Inside the Glenn Extreme Environments Rig (GEER), you can visit anywhere in the cosmos.
By Joe Pappalardo
Imagine what it’s like to be a spacecraft. Your service life begins with a violent explosion skyward, followed by a hypersonic struggle to escape Earth’s gravity, and, if you’re lucky, the reward of reaching the minus-270-degree vacuum of space. Then, after months or, in some cases, years, you might get to land on an alien planet with an environment seemingly designed to melt, corrode, compress or irradiate you out of existence.
One particularly lethal planet is Venus, where NASA plans to send a probe by 2020. To make sure the expensive machinery survives the mission, scientists at the Glenn Research Centre, a NASA outpost near Cleveland, Ohio, have been testing samples in a 14-ton steel tank called the GEER. With eight gas streams and the ability to mimic the extreme temperatures and pressures of Venus, it can help scientists find the absolute limits of man-made objects before they face them in space. Here’s how it works.
A closer look at GEER:
Each of four cabinets contains two independent gas cylinders to create a mix of up to eight gases, which can recreate an alien atmosphere to the parts per million.
(See Recipe for Venus, below.)
To make sure the corrosive gases don’t damage the GEER itself, a majority of the tubing is treated with a non-reactive protective coating called Sulfinert. It reduces corrosion and prevents the gases from adsorbing on, or sticking to, the tube walls.
This machine blends the gases, also adding any necessary water and pumping the blend into the sealed vessel, where the test materials await.
The vessel is constructed of low-carbon 304-type stainless steel, which is nearly tough enough to resist the Venusian atmosphere on its own. In addition, the internal walls are polished to a mirror finish, so that there are no nicks or rough spots to give corrosion a foothold.
Heat and pressure increase
The atmosphere of Venus is primarily composed of “supercritical” carbon dioxide. It’s under so much pressure that it doesn’t behave like a liquid or a gas, but somewhere in between. Once the gas mix is inside the vessel, the heat and pressure increase to this level, so researchers can find out what it might do to potential probe materials.
Once the machine is up to Venus’s conditions, a gas sample is run through a mass spectro-meter. In the future, a window will be added to the container, allowing a laser to measure chemical composition and the vessel to remain sealed for the duration of the test.
Using the ingredients for this hellish brew isn’t as dangerous as it sounds. Since the concentrations GEER uses are so low, the amount of gases used at the facility over the course of a year doesn’t even violate the Environmental Protection Agency’s daily allowable limit. Still, when GEER vents after the end of an experiment, a fan on the building’s roof draws in air to dilute the exhaust.
A closer look at Venus:
Recipe for Venus
965 000 parts per million
35 000 ppm
less than 1%:
poisonous and also flammable
poisonous, flammable, explosive, and smells like rotten eggs
a main component of hydrochloric acid, which breaks down food in your stomach
a main component of hydrofluoric acid, which can dissolve glass
Raise to 1340 psi at 470 degrees Celsius. Good luck.