Reusable Spacecraft

Reusable spacecraft are spacecraft capable of repeated launch, atmospheric reentry, and landing or splashdown. This contrasts with expendable spacecraft which are designed to be discarded after use. Agencies operating reusable spacecraft aim to have lower costs and higher flight frequencies.

Reusable spacecraft may be crewed or uncrewed and orbital or sub-orbital. Examples include spaceplanes such as the Space Shuttle and the Boeing X-37B, and space capsules such as the SpaceX Dragon. The Blue Origin New Shepard is an example of a sub-orbital spacecraft.

History

On 17 July 1962, the North American X-15 rocket plane reached an altitude of 95.9km on a sub-orbital flight. In 1963, the X-15 completed two flights above 100km. These marked the first spaceflights with a reusable vehicle. The Gemini SC-2 capsule followed, making a sub-orbital flight in 1965 and another sub-orbital flight in 1966.

The first spacecraft to be reused in orbit was the Soviet VA spacecraft, a capsule that was part of the larger TKS spacecraft. A VA capsule that launched in 1977 was reflown in 1978.

The Space Shuttle was the first orbital spacecraft designed for reuse according to NASA, and first launched in 1981. Five orbiters would launch 135 times before the vehicle's retirement in 2011. Space Shuttle ''Discovery'' set the record of 39 spaceflights with a single spacecraft in 2011. The Space Shuttle program, however, faced criticism that it failed to reduce the cost of access to space and had safety concerns following the ''Challenger'' and ''Columbia'' disasters.

The SpaceX Dragon 1 first flew in 2010 and became the first commercially built and operated spacecraft to be recovered from orbit. In 2012, Dragon became the first commercial vehicle to attach to the International Space Station (ISS), after which it conducted regular cargo resupply flights for NASA. Its first reuse was in 2017, and the vehicle led to the development of the Dragon 2, which first reached orbit in 2019. Dragon 2 carries both cargo and crew, and has been described as the most cost-effective spacecraft ever used by NASA. In 2021, Dragon 2 conducted the first orbital flight with only private astronauts onboard.

SpaceShipOne, another rocket plane, completed the first private sub-orbital spaceflight in 2004 and led to the development of SpaceShipTwo. The Blue Origin New Shepard capsule conducts commercial sub-orbital spaceflights, as did SpaceShipTwo.

Development flights for SpaceX Starship test vehicles began in 2019. Starship is intended to be both a fully reusable spacecraft and launch vehicle. Starship's first integrated launch with its booster was in 2023, and it reached space the same year. In 2024, Starship successfully reentered the atmosphere and completed propulsive splashdowns in the Indian Ocean, although it has not been recovered from space intact.

Design

Reusable spacecraft must survive reentry and safely return to the surface. The mass of any hardware dedicated for this reduces potential payload mass.

Atmospheric entry

Orbital spacecraft initiate a deorbit burn and orient themselves for atmospheric entry. The Boeing Starliner and Orion discard their service modules, including most of their maneuvering engines. The SpaceX Dragon discards its trunk, which includes its solar panels and radiators, but retains its Draco engines in the capsule. The Space Shuttle was notable for recovering the entire spacecraft.

In general, around 15% of the landed weight of a vehicle is heat shielding. Thermal protection systems (TPS) can be made of a variety of materials, including reinforced carbon-carbon and ablative materials. Historically, these materials were first developed on ballistic missile reentry vehicles. However, the requirements of reusable space systems differ from those of single use reentry vehicles, especially with regards to heat shield requirements. In particular the need for durable high emissivity coatings that can withstand multiple thermal cycles constitutes a key requirement in the development of new reusable spacecraft. Current materials for such high emissivity coatings include transition metal disilicides.

Ablative heat shields are reliable, but are heavy and diminished with use. Reinforced carbon-carbon heat tiles such as those used on the Space Shuttle are fragile, contributing to the ''Columbia'' disaster. The Space Shuttle used the LI-900 material.

Landing and refurbishment

Runway landings from orbit became prevalent with the introduction of the Space Shuttle. Spaceplanes that land horizontally on a runway require lifting surfaces and landing gear. Designs include the Space Shuttle's delta wing and the Dream Chaser's lifting body. Spaceplanes require access to a long enough runway, a necessary consideration for the Space Shuttle launch abort modes.

The first recoverable space capsules landed under parachute, either on land or by splashing down in a body of water. Ground landings require additional cushioning, which Starliner accomplishes with deployable airbags. This was considered for Orion as well, but was ruled out due to the extra mass required. The sub-orbital New Shepard uses retro-rockets to slow down just before touchdown, a technique that has been used by the expendable Soyuz since the 1960s. Splashing down allows the water to cushion the spacecraft, but exposure to salt water can have adverse effects on the vehicle. Despite this, SpaceX began regularly reusing Dragon capsules after splashdown.

Dragon 2 was originally designed to propusively land using its SuperDraco engines; however, propulsive landings for Dragon were canceled and Dragon 2 also uses parachutes to splashdown in the ocean. Starship is designed to propulsively land using its Raptor engines. It aims to be "caught" by the launch tower, as is done for the Super Heavy booster. This eliminates the need for traditional landing legs on the vehicle and aims to lower the turnaround time between launches.

After a spacecraft is recovered, it may need to be refurbished before its next flight. Depending on the spacecraft design, this process may be lengthy and expensive, and there may be a limit to how many times a spacecraft can be refurbished before it has to be retired.

List of reusable spacecraft

Operational

Under development

Retired

Proposed

*SUSIE
*Avatar

Canceled

* Boeing X-20 Dyna-Soar
* Hermes
* Kliper
* MAKS
* HOPE-X
* Skylon

See also

* Reusable launch system

Notes

References

{{Reusable launch systems

Spacecraft