Uncrewed Capsules

Uncrewed missions to LEO

Not all missions that enter earth orbit and return carry a crew. Some missions carry experiments to LEO and return them safely. These missions can be flown on un-crewed crewed platforms such as the SpaceX Dragon capsule and the Russian Foton capsule. Others, such as Space Rider and X-37 have been developed especially for an uncrewed mission.


Operator: Roscosmos

Mission: Experiments in microgravity

First flight: 1985

Status:  Active

The Foton satellite program is a Russian platform for microgravity research. The satellite is launched onboard a Soyuz rocket and re-enters like the Vostok capsule. That means that the heat shield is all around the capsule, and the vehicle entries ballistically. The last Foton mission was flown in 2014 as Foton-M4, and the Foton-M5 mission is set for 202x.

Bion and Bion-M

Operator: Roscosmos

Mission: Biological experiments in microgravity

First flight: 1973-1996 (Biom), 2013 - active (Bion-M)

Status:  Active 

The Bion program was started in 1973 to perform biological research. The satellites carried all kinds of biological experiments on various living species ranging from fungi and plants to monkeys and tortoises. On average, the missions lasted 22-days. The return capsule was a modified Zenit-2 re-entry capsule. However, due to the Zenit-2 being a spy satellite, information is rather scarce. What can be assumed is that the cameras from the Zenit-2 were removed to make space for the experiments and also their life-support.

The Bion program ended in 1996 and was followed up by the Bion-M program. This has its first flight in 2013. This re-entry capsule is based on the Vostok capsule (link to chutes Vostok page). The capsule was also modified for biological experiments. However, compared to the original Bion experiments, the experiment's lifetime was extended to 6 months, and the scientific payload was increased by 100 kg. However, the first Bion-M mission only had a mission duration of one month. The second Bion-M mission was scheduled to be launched in 2020 but was delayed until 2023. [20, 21]

Bion-M spacecraft

Corona Discoverer

Operator:  USAF/DOD

Mission:  Spy capsule recovery

First flight: 1956

Status: Cancelled

In the midst of the cold war, aerial espionage was key for the United States to gather intelligence on the USSR’s capabilities. The U-2 spy planes had been flying successfully over the Soviet Union for many years, however the idea of using a spacecraft for espionage was very promising. Therefore the Corona spy satellite program was initiated in 1956. These satellites were tasked to fly over the USSR multiple times and then return the footage to the US. The missions were also named ‘Discover’ as a cover for the public, to whom was said that the objective was to fly scientific payloads to space, which did occasionally happen.

The re-entry capsule was a blunt cone with a spherical front, also referred to as ‘bucket’,  and used a two-stage parachute recovery system. A drogue chute decelerates the capsule, after which the main deploys. Instead of a water landing, an aircraft would snatch the capsule by catching the parachute mid-air. This proved to be challenging and often required multiple attempts per capsule, even with a trained pilot. Three different main parachute designs have been flown on the Corona capsules in an attempt to improve the mid-air capture success rate, although without much success. Apart from the mid-air recovery aircraft, there were ships and helicopters present within the recovery area to capture the capsule in case of a splashdown. These proved to be necessary in multiple occasions when the vehicle was off-course and landed outside of the recovery area. The retrieval experience gained during the Corona – Discoverer program proved very valuable during retrieval of the Apollo missions.

The Corona – Discoverer program was one with many failures and challenges that had to be tackled because of the fact that rocketry and satellites were a relatively new and unexplored territory of engineering. One of the early flights, Discoverer-8, encountered a failure that was attributed to the recovery system, where the parachutes failed to deploy, leading to a loss of the vehicle.  It was Discoverer-13 that successfully launched, entered orbit around the Earth and became the first man-made object to be recovered from Earth orbit in 1960, only 9 days before the USSR achieved the same result with one of the Sputnik probes. Although considered successful, the capsule's recovery didn’t go as planned: the capsule landed too far from the recovery aircraft and had to be quickly recovered by helicopter before it would sink. The first mid-air recovery of the corona capsule was Discoverer-14.

Although many flights never returned safely or even didn’t reach space, the Corona satellites managed to provide valuable footage of the USSR. After the last flight of a corona spy satellite, in 1972, the KH-9 Hexagon spy satellite continued to provide footage for the United States. The satellite carried multiple corona-like capsules that it could deploy at different moments in time. [30, 31, 32]

Corona capsule captured in mid air

Fanshui Shi Weixing

Operator: China

Mission: Recoverable satellite 

First flight: 1974

Status: Retired

Much like the US Corona and the Soviet Zenit satellites, China had their own recoverable satellite called Fanshui Shi Weixing. Their main objective was to act as spy satellites, later variants also served as biosatellites much like the Soviet Bion capsules. One interesting feature was the thermal protection of the FSW satellites, this was done using impregnated oak. This allowed for quickly produced ablative thermal protection. 

The FSW satellites also briefly served as the baseline for China's second crewed capsule after the Shuguang spacecraft was cancelled. However, some sources suggest that this program was solely for propaganda purposes and never designed for operation. 

Space Rider

Operator: ESA

Mission: Reusable payload delivery vehicle

First flight: Unflown 

Status: In development

Space Rider, Space Reusable Integrated Demonstrator for Europe Return, is a small spaceplane developed by Italy in collaboration with ESA. Space Rider will launch on the Italian built Arianespace operated Vega-C launcher. The objective is to bring a payload of 800 kg to orbit and back. The vehicle is designed for at least six flights. 

Space Rider in orbit showing the capsule and the service module

Atmospheric Entry

The space rider capsule is a lifting body type spacecraft. That means that, much like the space shuttle, the capsule generates lift. A lift generating capsule is more complex than a ballistic entry capsule, but the maximum deceleration and thermal loads are lower. Space Rider's ability to perform a gliding entry was tested in the ESA IXV mission, which flew a suborbital trajectory using a Vega launcher in 2015. From the render, one can see that the spacecraft does not have any wings; this is due to the lifting body design, which means that the spacecraft body itself generates sufficient lift to perform a gliding entry. This is unlike the US Space Shuttle or Russian Buran. This also means that the capsule cannot land by itself and requires a parachute system for a safe landing. 

Parachute system

Even though the Space Rider has a lift generating body, it cannot generate sufficient lift for a safe landing. Therefore it requires a parachute system for the final landing. The space rider parachute system consists of two drogue parachutes and a parafoil main parachute. The parafoil can be seen below during an X38 test flight. Parafoils are lift generating parachutes. This means that they work much like the wing of an aircraft. 


Operator: ASI

Mission: Experiments in microgravity 

First flight: Unflown 

Status: Cancelled

The CARINA Space System (CApsula di RIentro Non Abitata [138], meaning ‘uninhabited re-entry capsule’) was a project of the Italian Space Agency (Agenzia Spaziale Italiana, ASI) that was started in 1990 [139] with the aim of developing a spacecraft that could carry microgravity experiments into orbit and return them to Earth. The spacecraft, which would have had a lift-off mass of approximately 600 kg, would carry up to 165 kg worth of experiments into a 360 km orbit [138]. While in orbit, the experiments would be supported by a service module. Five days into the mission, the vehicle would perform a deorbit manoeuvre, and the service module would separate at an altitude of approximately 130 km [138]. The re-entry capsule, which was of the blunt body type, would safely carry the experiments through the atmosphere until the speed had decreased enough for the parachutes to be deployed, after which the vehicle would splash down in the Indian Ocean [138]. No further information about the parachute system is known, and the project was cancelled in 1995 [139].

CARINA capsule [140]


Operator: NASA, ESA, DLR

Mission: Crew return vehicle

First flight: Unflown 

Status: Cancelled

The X-38 was an experimental NASA vehicle that could be launched on an Ariane 5 launcher. The project was cancelled in 2002. The launching on top of the Ariane 5 reminds one of the Hermes spacecraft, which was cancelled in 1987. Later, the X-38 research was used in the Crew Return Vehicle (CRV). The CRV would be used if a fast evacuation of the international space station (ISS) would be required. The X-38 would have used a 100 ft drogue parachute and a parafoil main parachute, much like the Space Rider.

A backup parachute system was designed to safely land the vehicle in case of an emergency. This system contained a hybrid continuous ribbon-ringslot main parachute of 36.6 m diameter and a 7.9 m ribbon drogue parachute. The pilot chute and mortar of the backup system were identical to that of the primary recovery system and nearly identical to that of the Space Shuttle brake chute system.

A sub-scale version of the parachute was tested during drop tests where the parachute’s performance and new manufacturing methods were evaluated. The X-38 program was eventually cancelled in 2002, however, the parachute system lived on. The design was transferred to the US army’s LVAD program (Low-Velocity AirDrop system), where it would be used to land equipment from aircraft. Several tests showed skirt inversion and canopy inflation, likely caused by the high angle of attack encountered by the parachute when the payload is dropped out of the aircraft, in combination with the downwash. A temporary reefing system eventually solved the problem. [24, 25, 26]

Parafoil landing of the X-38, drop test


Operator: USAF

Mission: Unknown

First flight: 2010

Status: Active

The X37 is a spacecraft operated by the United States Airforce capable of performing a gliding entry. The spacecraft flies classified missions and is launched on board an Atlas V or Falcon 9. During the landing, the X-37 uses its lift generating capabilities to fly back to a runway where it lands like an aircraft. The X-37 can do this as the lift over drag ratio of the X-37 is higher at subsonic conditions compared to the Space Rider. The X-37 has had a troubled history where it was originally developed to fly in the Space Shuttle cargo bay. After the space shuttle's cancellation, the X37 was changed to be launched onboard a ULA Atlas V and the SpaceX Falcon 9. 


Operator: NASA

Mission: de-orbit demonstrator

First flight: 2012-current

Status: Active

To develop and improve technologies for small satellites, the Technology Educational Satellites are launched. These missions have the final goal of using and possibly land a small satellite on Mars or another planetary body [35]. Over the course of the past eight years, nine satellites have been launched, TechEdSat 1-8, and 10.

From TechEdSat 3 onwards, they include a passive exo-atmospheric de-orbit device, or in simpler terms, a parachute to be used in space environments for de-orbit, named Exo-Brake. This mylar parachute is deployed from the back of the satellite, aiming to replace the more complicated de-orbit systems, like thrusters, for small satellites. IT has a cross-shape and is supported by a hybrid system of mechanical struts and flexible chord. From TechEdSat 5 onwards, a control system was included that allowed the shape to be controlled in flight, much like the wright brothers did on their initial wing design [33]. The space-parachute onboard TechEdSat 5 had a size of approximately 0.35 m² and has a cross-shape.

The latest iteration TechEdSat, launched in 2020, has the largest Exo-Brake to date [37]. The Exo-brake can now be controlled from the ground to achieve a targeted re-entry and landing location. This should be useful for the de-orbit of satellites and sample return missions.

Exo-Brake parachute unfurling in space

RED capsules

Operator: SpaceWorks

Mission: Sample return capsule

First flight: 

Status: In development

The RED-25 capsule or Re-Entry Device with a payload capability of 25 kg. The organisation behind this capsule is SpaceWorks, an Atlanta-based company which houses legacy members of both Generation Orbit and Terminal Velocity Aerospace. RED-25 is designed to be carried towards orbit, after which it will provide weightlessness experiments that can be returned to earth and other types of sample and cargo return. The capsule weighs about 15 kg and is 1 meter in diameter. For safe landing, the capsule is equipped with a guided parafoil for precision landing [156]. 

SpaceWorks is working on a family of capsules including RED-50, RED-25, RED-12, and RED-8. The smallest has a diameter of about 0.5 meters and the larger capsule has a diameter of 1.3 meters. No orbital flights have been performed to date, however, the company conducted several drop tests that seem to be successful. Besides offering missions with a single payload the company is considering a RED-4U mission which holds four cubesat-style payloads, this capsule seems to be based on the RED-8 configuration as the total payload mass indicated is 8 kg [157]]. 

A smaller version of the RED capsules is the RED-DATA2. This capsule comes in with a diameter of 23cm and a height of 19 cm. The shape of the vehicle is very similar to the others but the mission is geared more towards TPS testing, atmospheric re-entry data gathering and flight environment profiling. Three RED-DATA2 capsules were included in the S.S. John Glenn Cygnus capsule. After Cygnus broke up due during re-entry the RED capsule did not communicate anything back to earth. Terminal Velocity Aerospace, the operator at that time, made several recommendations for future flights. [158, 159]