CPI Thermal Switches – Keeping Astronauts Safe on the ISS

The International Space Station (ISS) may be one of the most underappreciated technological (and geopolitical) marvels on, or off the planet. While it has been under development since the 1990’s it is actually the joint effort of five different space agencies representing 15 countries, all of whom contributed technology and resources to the ISS, especially the United States and Russia. It is a shining example of what scientists across borders can do together when focused on a common technological challenge.

The space station is the largest structure ever assembled in space.  Orbiting at about 248 miles above the earth it is so large that it is often visible at night to the naked eye.  It is longer than a football field (including the end zones) and can sleep 7 astronauts. It has habitable space often compared to that on a 747 jumbo jet, or about the size of a 5 bedroom house.

Astronaut Peggy Whitson aboard ISS

The ISS has been populated by astronauts since November of 2000 and has been populated non-stop for the almost 18 years since.  Its useful accomplishments range over almost the entire spectrum of scientific discovery. For instance, scientists were able to grow proteins in space with a near-perfect crystalline structure. These proteins have unique properties that prove useful in the development of new drugs. Also the detection of “dark matter” long predicted by physicists, was accomplished using the Alpha Magnetic Spectrometer, deployed on the space station. This discovery sent shock waves through the scientific community, a moment as pivotal as Einstein’s E=MC2.  These achievements and many more were only possible over a long period in the pure gravity free environment afforded by the ISS.

Technology and Experiments Aboard the ISS

Needless to say, the ISS houses some of the most sophisticated technology and experiments that NASA and other space agencies can think of. Safety of the astronauts and “space tourists” that visit and reside there is of paramount importance. The stringent testing and documentation required by vendors and space agencies providing parts and subsystems to NASA, is well known to every subcontractor.

One of the experiments headed for the ISS from NASA is called the Flow Boiling and Condensation Experiment (FBCE), a joint effort between the Purdue University Boiling and Two-Phase Flow Laboratory (BTPFL) and the NASA Glenn Research Center. The experiment will fly aboard the International Space Station sometime in 2020 for two years or longer.  The purpose of the FBCE project is to develop an integrated two-phase flow boiling and condensation experiment for the ISS to serve as a primary platform for obtaining two-phase flow and heat transfer data in microgravity.

Technicians at work preparing the FBCE for launch in 2020.

One of the key safety concerns of the FBCE experiment involves preventing the formation of a highly dangerous gas during the boiling phase of the experiment. The system uses a special fluid called perfluorohexane as the primary boiling/condensation substance, however when this substance exceeds 200C it can degrade into a highly toxic gas called Perfluoroisobutene (PFIB).   PFIB when inhaled can cause pulmonary edema and other heart disorders. The goal is to have thermal switching in place at setpoints well below the 200C to prevent such an occurrence.

CPI’s Thermal Safety Solution for the FBCE.

CPI was approached by NASA to consider the use of a thermal switch solution based on our M1102 “PlugStat” series of thermal switches. The PlugStat Series of close tolerance, bimetal thermal switches act as a robust and accurate temperature control switch in a wide variety of thermal control systems at temperature ratings from 17C (0F) to 343C (650F).  This is a slow make and break, open-on-rise device that is hermetically sealed, with 1/2-20UNF-3A  thread mounting.

Despite NASA’s stringent material and electrical requirements, CPI’s off-the-shelf M1102 met their need for a reliable, space deployable, thermal safety switch solution.

Our switch uses:

  • Stainless Steel type 304
  • Stainless Steel type 321
  • Inconel Alloy 600
  • Stycast type 2651
  • Platinum Contacts

Our standard electrical rating of 2A at 28V was able to meet the electrical needs of NASA in the application. Additionally CPI provided all applicable CoC’s, Material Test Reports, and Chemical Analysis’ required to meet NASA’s stringent quality control.

CPI Thermal Switches – Good for the International Space Station…Good For You Too.

Sometimes a robust thermal switch is what you need, remote sensors and controls systems have their place, but in tough applications, they have their limits too.

The chances are that the team at CPI can fit our thermals into whatever application you have, without expensive customization.

Call the thermal switch engineering team today to discuss your application!