Dragon CRS-2 SpX-35

Dragon SpX-35 is SpaceX’s thirty-fifth resupply run to the Station, the eighteenth flown by the Cargo Dragon 2 variant since it took over from the original Dragon in late 2020. The vehicle docks autonomously to the zenith port of the Harmony module and stays for about a month while the crew unloads, then reloads it with returnables — the only resupply vehicle that brings things back instead of burning them up. Splashes down off the Florida coast within hours of undocking, then drives by truck to the NASA labs in Houston.

What makes Cargo Dragon different

Among the freighters that serve the Station — Progress, Cygnus, HTV-X — Cargo Dragon is the only one designed for a return trip. After undocking, it performs a deorbit burn and splashes down under parachutes off the Florida coast. The capsule is recovered by a SpaceX vessel, and the cargo inside — experiment samples, hardware for analysis, film canisters, biological specimens — is in the hands of scientists within hours.

This return capability matters for science. Many experiments on the Station generate results that can only be analysed on the ground: protein crystals that need to be examined under X-ray diffraction, cell cultures that must be preserved at precise temperatures, and materials samples whose properties can only be measured with equipment too large for the Station.

The payload

The notable payload on this flight is a new science freezer rack — the third generation of the GLACIER hardware, capable of holding biological samples at minus 80°C for the entire return cruise. That cold chain matters for the Station’s protein-crystal and stem-cell experiments: a thaw on the way home would erase a year of work in the lab.

In addition to the freezer, SpX-35 carries the usual mix of crew provisions, replacement hardware, and new experiment kits for the US, European, and Japanese laboratory modules.

Docking and operations

Cargo Dragon approaches the Station using the same autonomous docking system as the crewed variant. It navigates using a combination of GPS, relative navigation sensors, and the docking adapter’s alignment guides. The crew monitors the approach but does not need to intervene.

Once berthed, unloading takes several days. The crew transfers cargo bag by bag, scanning barcodes as they go so that the ground teams can track every item’s location. Inventory management in microgravity is a serious logistical challenge — a misplaced item can float behind a panel and remain lost for months.

Departure

After roughly a month attached to the Station, Dragon is loaded with return cargo, sealed, and released. It fires its engines, drops out of orbit, and splashes down. The turnaround from splashdown to the cargo reaching Houston labs is typically under twenty-four hours.