Spacecraft designed for repeated use and reusability
A
reusable spacecraft
is a class of
spacecraft
that have been designed with repeated launch, orbit, deorbit and atmospheric reentry in mind. This contrasts with conventional spacecraft which are designed to be expended (thrown away, allowed to burn during reentry) after use. Examples of reusable spacecraft are
spaceplanes
(such as the
Space Shuttle orbiters
and the
Dream Chaser
) and
space capsules
like the
SpaceX Dragon
. Such spacecraft need mechanisms to prevent the disintegration of the spacecraft and its occupants/cargo during reentry. Failure of such systems may be catastrophic, as what happened in the
Space Shuttle
Columbia
disaster
.
Design
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Atmospheric entry
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Reusable spacecraft include mechanisms to deorbit and
reenter the atmosphere
in a controlled fashion. For this purpose, the
Space Shuttle
included
OMS pods
, and the
SpaceX Dragon
included its own engines, used for deorbiting. Deorbiting slows the spacecraft down, lowering its perigee to inside the atmosphere where the vehicle descends to Earth.
[1]
[2]
As a rough rule of thumb, 15% of the landed weight of an atmospheric reentry vehicle needs to be
heat shielding
.
[3]
Thermal Protection Systems
(TPS) can be made of a variety of materials, including
reinforced carbon-carbon
and
ablative materials
.
[4]
Historically these materials were first developed on ICBM
MIRVs
. 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.
[5]
Ablative heat shields are reliable, but they can only be used once, and are heavy.
Reinforced carbon-carbon
heat tiles like those used on the Space Shuttle are fragile, and this was proved on the Space Shuttle Columbia disaster. Making a resistant yet lightweight and effective heat tile poses a challenge. The
LI-900
material was used on the Space Shuttle.
Landing and refurbishment
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Spacecraft that land horizontally on a runway require wings and undercarriage. These typically consume about 9-12% of the spacecraft mass,
[
citation needed
]
which either reduces the payload or increases the size of the spacecraft. Concepts such as
lifting bodies
offer some reduction in wing mass,
[
citation needed
]
as does the
delta wing
shape of the
Space Shuttle orbiter
.
Vertical landings
can be accomplished either with parachutes or propulsively.
SpaceX Dragon
was an example of
space capsule
with parachute reusability. Its derivative,
Dragon 2
, was originally intended to propusively land on land. However, such concept of reusability was canceled in 2017 and now Dragon 2 uses parachutes to land in the ocean.
After the spacecraft lands, it may need to be refurbished to prepare it for its next flight. This process may be lengthy and expensive, taking up to a year. And the spacecraft may not be able to be recertified as human-rated after refurbishment. There is eventually a limit on how many times a spacecraft can be refurbished before it has to be retired, but how often a spacecraft can be reused differs significantly between the various spacecraft designs.
[6]
[7]
List of reusable spacecraft
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U.S. And ESA
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Active
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In development
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Retired
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Canceled
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Russian/Soviet
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In development
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Canceled
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Others
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In development
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Canceled
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See also
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References
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Launch systems
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Spacecraft
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