Astronauts get a welcome boost from a SpaceX Dragon | On the International Space Station Sept. 1-5, 2025

Expedition 73 activities continued this week with bone loss and cardio studies, as well as a first-of-its-type reboost operation for the orbital complex.

Orbital observation

Students from the Computer School in New York had a chance to record questions for Expedition 73 crewmates Jonny Kim of NASA and Kimiya Yui of JAXA (Japan Aerospace Exploration Agency) to answer during a live broadcast from the International Space Station (ISS) on Friday (Sept. 5). Among the topics that the middle school students asked about was why we explore.

"Personally I think humankind is always in need of a frontier in order to live happily, so that's why you keep doing exploration," said Yui.

"I think exploring that frontier is so important to inspiring the next generation," added Kim.

Another student asked if, given a choice between living in space or on Earth, which would they choose?

"I have a lot of fun up here in space," said Kim. "We enjoy the views of Earth together, sharing stories over dinner, and the work we do is very rewarding. But Earth is still my favorite place to be. It's my home, and it's where everyone I love is still there. And so of course for me, I'd rather live on Earth."

You can watch the entire Q&A below.

NASA and JAXA Astronauts Discuss Life in Space With New York Students - YouTube

Watch On

Science status

Among the research that was conducted by the Expedition 73 crew aboard the space station this week was:

Cardiobreath — Flight engineer Mike Fincke helped collect data to improve future crews' exercise regimes by wearing a headband and vest connected to sensors while he rode a stationary bike in the U.S. Destiny laboratory.

Microgravity Associated Bone Loss-B — Jonny Kim prepared bone stem cell samples that were being treated with a therapeutic agent. The study may improve our understanding why astronauts' skeletal systems undergo changes over the course of their missions.

Station keeping

The Expedition 73 crewmates also took part in activities to maintain the space station's systems and prepare for future research.

Multi-use Variable-g Platform — Kimiya Yui of JAXA swapped out the moisture-absorbing cassettes for this microwave-size device that can be used to spin up scientific samples to up to twice the force of Earth's gravity.

European Enhanced Exploration Exercise Device — Yui also gave a the 34D a good look over for its ability to support bicycling, rowing and resistive capabilities, as well as train with rope pulling and climbing.

CRS-33 — Jonny Kim and Zena Cardman worked on unloading science and logistical supplies from the Dragon cargo spacecraft that arrived at the space station last week.

Ground controllers also reoriented the station and tested the new Dragon reboost kit to increase the orbiting complex's altitude above Earth. This was the one of the first times a SpaceX spacecraft had been used to reboost the station.

Astronaut activity

NASA astronaut Jonny Kim used a spacesuit to demonstrate the difference between being weightless and having mass in the microgravity environment of space.

"How do we translate large heavy objects in space? Carefully and with the slightest of inputs," he posted on his social media accounts.

By the numbers

As of Friday (Aug. 15), there are 7 people aboard the International Space Station: Expedition 73 commander Sergey Ryzhikov of the Russian space agency Roscosmos; fellow cosmonauts Alexey Zubritsky and Oleg Platonov; Jonny Kim, Zena Cardman and Mike Fincke of NASA; and Kimiya Yui of JAXA, all flight engineers.

There are two docked crew spacecraft: SpaceX's Dragon "Endeavour" attached to the zenith port of the Harmony module and Roscosmos' Soyuz MS-27 attached to the Earth-facing port of the Prichal node.

There are three docked cargo spacecraft: Roscosmos' Progress MS-30 (91P) attached to the aft port of the Zvezda service module, and Progress MS-31 (92P) docked to the space-facing port of the Poisk module. SpaceX's CRS-33 Dragon spacecraft is docked to the forward port of Harmony Node 2.

As of Friday, the space station has been continuously crewed for 24 years and 10 months and 3 days.