What goes up…

by | Apr 9, 2020 | Big Ideas, Spring 2020 | 0 comments

Some experiments can’t be carried out on Earth. But it’s also impractical to send every experiment that requires microgravity to the International Space Station. Instead, many experiments are conducted in drop towers that provide a microgravity environment.

Martin Castillo ’99, PhD ’04, head of material science at University of Bremen’s Center of Applied Space Technology and Microgravity (ZARM), works with the world’s most capable drop tower (pictured right) to synthesize materials in this specialized environment. We sat down with Castillo to talk about how drop towers work and the benefits of microgravity research.

What happens to materials in microgravity?

Martin Castillo: Two things happen in microgravity: number one, you suppress gravity-driven buoyancy forces. We’re able to suspend really heavy, dense objects and produce a very homogeneous material.

The second thing is that you suppress gravity-driven convection. The way heat is passed through materials is a little different than on Earth, and you can use this to create novel materials.

Walk us through what it would be like to carry out an experiment in the drop tower.

Castillo: Let’s say I have a chemical mixture I wanted to react. I measure out the amount of chemicals inside a glove box. I assemble the materials I want to react in microgravity and put them into combustion chambers. I put the chambers in a capsule which goes into the tower.

All the air gets pumped out of the tower, which is 147 meters tall; the tube itself is around 120 meters
and the fall distance is 110 meters.
If it’s not windy outside, which causes the tower to shake, I’ll be able to do a drop and obtain 4.74 seconds of microgravity.

We also have the world’s only capability for doing a catapult. We can shoot our capsule from the bottom of the tower, and it’ll go up and down approximately 212 meters. This vertical parabola gives you 9.3 seconds of microgravity.

What will microgravity research enable us to do in the future?

Castillo: A lot of people are reinventing what was done 30 to 40 years ago. We’re advancing materials and trying to implement new techniques. Now that we have such great control and precision with these instruments and doing measurements on atomic scales, we can do quite a bit more. We can evaluate what we couldn’t in the past and make new steps.

What are you working on?

Castillo: I’m making an advanced semiconducting material that emits light. LCDs don’t work in space, but I can make a two- to three-color display that works in extreme environments. This would be a good replacement for the printed flipbooks that astronauts use on external missions. They would now just have a screen on the outside of their suit and connect with the Wi-Fi to upload or download new commands for what they’re doing on the space station. I’m also working on improving the energy efficiency of screens and displays so that you only have to charge your phone once per week.