Crewed Space Capsule

Overview

A crewed space capsule carries astronauts from the launch pad to orbit, supports them during the mission, and returns them safely through the atmosphere to a water or ground landing. It is the most safety-critical pressurized vehicle in common production: a single hull failure, a heat shield breach, or a parachute that fails to open is unsurvivable. Every subsystem is built with redundancy, and the whole vehicle is qualified to keep the crew alive through a launch abort at any point in ascent.

The capsule described here follows the modern blunt-body class flown by Crew Dragon, Orion, and Soyuz: a truncated cone roughly 4 m across at its base, with a habitable pressure vessel for the crew and a service section carrying propellant, radiators, and solar power. It launches atop an expendable or reusable booster, separates after second-stage cutoff, maneuvers and docks to a station, then later deorbits, sheds its service section, and reenters protected by an ablative heat shield. Descent is staged through drogue and main parachutes to a survivable landing.

Pressure vessel and structure

The primary structure is a sealed cabin that holds about one atmosphere of breathable gas against the vacuum of space. The crew module shell is built from machined aluminium-lithium hull panels joined by friction-stir welds and stiffened with isogrid rings, a layout that gives high strength at low mass. Forward and aft pressure bulkheads close the cabin, and the load from launch and landing is carried into the backshell support frame.

Crew see out through cabin windows made of triple-pane fused silica in titanium retainer frames, each pane separately pressure-rated so a single crack is not a leak path. The side hatch seals on a silicone seal driven by six latches and a motorized actuator, with a pressure sensor confirming the seal before launch. The forward docking adapter mates to a station using a soft-capture ring and petals that absorb closing energy, then twelve hard-capture latches pull the interface airtight against its seals.

Thermal protection

Reentry from low Earth orbit converts the vehicle's 7.8 km/s of velocity into heat. The thermal protection system keeps that heat outside the cabin. The forward heat shield is the hottest part, reaching roughly 1650 C at peak heating. It is built from PICA ablator blocks bonded into a honeycomb on a composite carrier structure; the ablator chars and sheds material, carrying energy away rather than conducting it inward. The cooler conical sides are covered with silica backshell tiles, held by standoff hardware with ceramic isolators so heat does not bridge into the structure. On orbit, multi-layer insulation blankets handle the gentler thermal swings between sunlight and shadow.

Propulsion and reaction control

The propulsion system runs on storable hypergolic propellants: nitrogen tetroxide and monomethylhydrazine, which ignite on contact and need no separate ignition source. MMH and NTO tanks use elastomer diaphragms to feed propellant in zero gravity, pressurized by helium from a carbon-overwrapped tank held near 310 bar and stepped down by regulators. Service thrusters perform orbit maneuvers, while powerful launch abort thrusters can pull the capsule clear of a failing booster in under two seconds. Flow is controlled by isolation valves through a network of stainless feed lines.

Fine attitude control comes from the reaction control system, four thruster pods of small attitude thrusters that point the vehicle for docking and hold it stable through reentry.

Avionics and GNC

The avionics suite flies the vehicle. Three flight computers, each built on a radiation-hardened CPU, run guidance, navigation, and control in triple modular redundancy, with voting logic discarding any computer that disagrees. Position and attitude come from redundant inertial measurement units, optical star trackers that match star fields to an onboard catalog, and GPS receivers in orbit. A rendezvous lidar provides relative range and bearing for the final approach to a station. The crew monitor and command the vehicle through touchscreen glass displays, all tied together over a redundant data bus.

Life support and power

The environmental control and life support system keeps the cabin habitable. CO2 scrubbers pull exhaled carbon dioxide from the air using amine sorbent beds, oxygen tanks replace what the crew consume, and circulation fans keep the atmosphere mixed so no stagnant pockets form in weightlessness. A pumped coolant loop with a condensing heat exchanger and radiator panels removes metabolic and equipment heat and controls humidity, while pressure regulators hold cabin pressure and an atmosphere sensor pack watches oxygen, carbon dioxide, and humidity continuously.

Electrical power comes from the power system. Body-mounted solar arrays of triple-junction cells charge lithium-ion battery modules, and a power distribution unit switches and protects the 28 VDC buses feeding every load through the power harness.

Recovery

After the deorbit burn and reentry, the recovery system slows the capsule for landing. Two drogue parachutes deploy first to stabilize and decelerate the vehicle while it is still moving fast, fired clear by gas mortars. The drogues then release four main ringsail canopies that bring descent down to about 7 m/s. For a water landing, the flotation system inflates bags that keep the capsule upright and afloat; a ground-landing variant instead uses energy-absorbing landing legs with crushable cartridges to soften touchdown.

Crew accommodations and variants

Inside, the crew accommodations hold the astronauts safely through high-load phases. Each seat is a contoured couch with a custom liner on stroking shock attenuators and a five-point restraint. A suit interface panel connects each pressure suit to cabin air, cooling, and communications, so the crew stay protected if cabin pressure is ever lost. Manual override is available through the control panel with hand controllers and a switch panel, and cargo rides in restrained stowage.

The same airframe supports several mission types. A crew of four is standard for station rotation flights of up to about 210 days docked, while a denser seating layout carries up to seven for short free-flight missions. Cargo variants remove the seats and life support to deliver pressurized supplies and return experiments to the ground, reusing the structure, heat shield, and recovery hardware unchanged.