How Humans Have Traveled From the ISS: Methods, History, and Future Options

Leaving the International Space Station (ISS) is a tightly choreographed sequence of events that begins with departure and ends with safe recovery on Earth or continued operation in orbit. This article explains how humans have gotten to and from the ISS to date, focusing on the Soyuz spacecraft and Crew Dragon as primary crew transport systems, supported by cargo vehicles that demonstrate reentry and disposal techniques. Current return processes rely on atmospheric reentry, parachutes, and splashdown in the Pacific Ocean, with ongoing evolution toward regular commercial crew rotation and eventual lunar missions. The following sections define key terms, review historical and contemporary missions, and outline planned advances.

Departure from the ISS

Before undocking, the ISS crew reviews procedures, packs personal items, and secures experiments. The spacecraft docked at the port typically performs a departure burn to move away from the station, followed by a safe distance check to ensure no collision risk. For crewed taxis such as Soyuz and Crew Dragon, the process is designed to return astronauts to Earth or to a free-flying vehicle. Cargo vehicles, including Cygnus and previously SpaceX Dragon cargo variants, demonstrate controlled reentry and intentional destruction over the Pacific Ocean as part of disposal operations.

Undocking and Return Timeline

Standard undocking sequences occur in phases: final checks, hatch closure, flyaround to assess clearance, deorbit burn, and reentry. Soyuz provides a quick, direct return profile measured in hours; Crew Dragon also targets same-day undocking to splashdown but allows flexible scheduling. Table 1 summarizes representative metrics for human and cargo returns. Note that arrival (launch) timelines are referenced only where relevant to contrast with departure operations.

Notable Details

• Deorbit burn timing adjusts orbital parameters to ensure entry within the atmospheric corridor.
• Parachute deployment occurs in stages, culminating in main parachute inflation.
• Recovery forces stand by for splashdown coordination, medical checks, and crew egress.

Crewed Transportation Systems

To date, the only operational crew vehicles transporting humans from ISS are Russia’s Soyuz MS spacecraft and SpaceX’s Crew Dragon. Soyuz has provided continuous crew rotation and emergency return capability since 2011. Crew Dragon, certified for operational crew rotation, follows a similar mission architecture but leverages modern avionics and splashdown profiles. Both systems employ proven reentry and parachute technologies to deliver crews safely to ocean recovery zones.

Cargo Vehicle Demonstrations

Cargo resupply missions, such as SpaceX Dragon and Northrop Grumman Cygnus, perform controlled reentries designed to end in destructive splashdown. These missions validate critical elements such as heat shield performance, parachute systems, and navigation that also apply to crewed return strategies. While cargo vehicles do not carry humans, they offer essential testbeds for return, recovery, and disposal processes under real flight conditions.

Reentry and Splashdown Physics

Atmospheric reentry converts kinetic energy into heat through friction, requiring precise entry angles to manage g‑loads and heating. Parachutes slow the vehicle to survivable speeds for ocean impact, where recovery ships retrieve the crew and capsule. Modern designs refine capsule shape, thermal protection, and parachute deployment sequencing to maintain consistent performance and crew safety across varied mission profiles.

Future Crew Return Options

Planned architecture beyond ISS includes lunar missions using Orion and commercial landers, with returns leveraging advanced heat shields and parachutes suited to higher energy entries. For low Earth orbit, commercial crew flights are expected to remain a primary method, while evolving concepts explore reusable capsules, enhanced recovery operations, and standardized return procedures to improve reliability and reduce risk.

Summary of Key Return Metrics