A rocket pumped microgravity into an artificial, simulated heart for the sake of biology and fluid science. This biomedicine experiment, called KRABS, flew human blood samples up to 260 km high to study how weightlessness alters the behaviour of red blood cells.

The module enjoyed a 13-minute ride to the edge of space – half of it in microgravity conditions – alongside a dozen other European experiments onboard SSC Space’s sounding rocket Suborbital Express-5 launched on 31 May.

When blood circulation slows down, red blood cells naturally tend to stick together and form temporary clusters, making blood more viscous. Changes in blood circulation during long space missions can cause blood in the veins to slow or pool temporarily, increasing its thickness and, over time, the risk of dangerous blood clots.

Understanding how blood cell aggregation and blood viscosity evolve is important for predicting risks to astronauts’ circulatory health and for advancing treatments for blood disorders on Earth.

The KRABS experiment mimicked a circulatory system. Researchers injected blood samples into tiny channels and measured how hard blood needs to be pumped to flow, and observed how viscosity varied following changes in flow rate.

The experiment used an advanced microscopy technique called digital holography to capture the formation and rupture of individual red blood cell clusters. Teams from the French National Centre for Scientific Research at University of Grenoble Alpes and the Free University of Brussels are behind the experiment.

ESA has used sounding rockets to investigate phenomena under microgravity from Esrange Space Center in northern Sweden for nearly 40 years.

The MASER research rocket that launched on Sunday hosted twelve experiments from nine countries, enabling researchers to study physical and biological processes under conditions not possible on Earth.

While the two other ESA modules contained research on metallurgy (XRMON) and the behaviour of the cells lining the walls of blood vessels (IMEDYS), a fourth “rideshare module” gave another nine projects a ticket to space. This shared space took research projects on human immune cells, stem cells and the solidification of metal alloys to the next level.