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.

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]

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]

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. 

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].

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.