A flight spare is a copy of a spacecraft or spacecraft part which is held in reserve in case it is needed for the mission. Flight spares are built to the same specifications as the original equipment (the "flight model"), and can be substituted in the case of damage or other problems with the flight model, reducing launch delays. The extra cost of building a flight spare can be justified by the enormous cost of delaying a launch by even a short amount of time.
Flight spares are constructed as contingencies. As such, spare parts may be swapped onto a craft before launch, or completed spare spacecraft may be launched if the flight model is lost.
NASA has two basic types of spares, development spares and operational spares. NASA makes a determination about which parts need spares based on whether parts are custom built, and the lead-time for procurement. It also makes determinations about the quantities of spares, based on whether the part is critical to system operation, failure rate, and the expected life of the part. [2]
The flight spare can also be useful during a space mission if a change to the original plan is required, since the effect of changes can be safely tested on the ground.
Flight spares that go unused in their initial missions are still considered valuable. A 2017 NASA report on flight spare inventory control mentions hundreds of millions of dollars' worth of inventory, not all of it catalogued properly. [3]
Individual spare components manufactured for one mission may eventually fly on another. As a cost-saving measure, the Magellan spacecraft was made largely out of such parts: [4]
| Component | Origin |
|---|---|
| Attitude control computer | Galileo |
| Bus | Voyager program |
| Command and data subsystem | Galileo |
| High- and low-gain antenna | Voyager program |
| Medium-gain antenna | Mariner 9 |
| Power distribution unit | Galileo |
| Propellant tank | Space Shuttle auxiliary power unit |
| Pyrotechnic control | Galileo |
| Radio-frequency traveling-wave tube assemblies | Ulysses |
| Solid rocket motor | Space Shuttle Payload Assist Module |
| Star scanner | Inertial Upper Stage |
| Thrusters | Voyager program |
Since few space probes return to Earth intact, flight spares are useful for posterity, and may go to museums. The Mariner 10 flight spare is such an example. [1]
Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System. Uncrewed space probes have flown to all the observed planets in the Solar System as well as to dwarf planets Pluto and Ceres, and several asteroids. Orbiters and landers return more information than fly-by missions. Crewed flights have landed on the Moon and have been planned, from time to time, for Mars, Venus and Mercury. While many scientists appreciate the knowledge value that uncrewed flights provide, the value of crewed missions is more controversial. Science fiction writers propose a number of benefits, including the mining of asteroids, access to solar power, and room for colonization in the event of an Earth catastrophe.
The Mariner program was conducted by the American space agency NASA to explore other planets. Between 1962 and late 1973, NASA's Jet Propulsion Laboratory (JPL) designed and built 10 robotic interplanetary probes named Mariner to explore the inner Solar System – visiting the planets Venus, Mars and Mercury for the first time, and returning to Venus and Mars for additional close observations.
Mariner 4 was the fourth in a series of spacecraft intended for planetary exploration in a flyby mode. It was designed to conduct closeup scientific observations of Mars and to transmit these observations to Earth. Launched on November 28, 1964, Mariner 4 performed the first successful flyby of the planet Mars, returning the first close-up pictures of the Martian surface. It captured the first images of another planet ever returned from deep space; their depiction of a cratered, dead planet largely changed the scientific community's view of life on Mars. Other mission objectives were to perform field and particle measurements in interplanetary space in the vicinity of Mars and to provide experience in and knowledge of the engineering capabilities for interplanetary flights of long duration. Initially expected to remain in space for eight months, Mariner 4's mission lasted about three years in solar orbit. On December 21, 1967, communications with Mariner 4 were terminated.
Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is currently carried out mainly by astronomers with telescopes, its physical exploration is conducted both by uncrewed robotic space probes and human spaceflight. Space exploration, like its classical form astronomy, is one of the main sources for space science.
A spacecraft is a vehicle that is designed to fly and operate in outer space. Spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle.
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Mariner 6 and Mariner 7 were two uncrewed NASA robotic spacecraft that completed the first dual mission to Mars in 1969 as part of NASA's wider Mariner program. Mariner 6 was launched from Launch Complex 36B at Cape Canaveral Air Force Station and Mariner 7 from Launch Complex 36A. The two craft flew over the equator and south polar regions, analyzing the atmosphere and the surface with remote sensors, and recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys, in order to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter five days later.
Mariner 10 was an American robotic space probe launched by NASA on 3 November 1973, to fly by the planets Mercury and Venus. It was the first spacecraft to perform flybys of multiple planets.
Mariner 1, built to conduct the first American planetary flyby of Venus, was the first spacecraft of NASA's interplanetary Mariner program. Developed by Jet Propulsion Laboratory, and originally planned to be a purpose-built probe launched summer 1962, Mariner 1's design was changed when the Centaur proved unavailable at that early date. Mariner 1, were then adapted from the lighter Ranger lunar spacecraft. Mariner 1 carried a suite of experiments to determine the temperature of Venus as well to measure magnetic fields and charged particles near the planet and in interplanetary space.
The Magellan spacecraft was a 1,035-kilogram (2,282 lb) robotic space probe launched by NASA on May 4, 1989. Its mission objectives were to map the surface of Venus by using synthetic-aperture radar and to measure the planetary gravitational field.
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Orion is a partially reusable crewed spacecraft used in NASA's Artemis program. The spacecraft consists of a Crew Module (CM) space capsule designed by Lockheed Martin and the European Service Module (ESM) manufactured by Airbus Defence and Space. Capable of supporting a crew of four beyond low Earth orbit, Orion can last up to 21 days undocked and up to six months docked. It is equipped with solar panels, an automated docking system, and glass cockpit interfaces modeled after those used in the Boeing 787 Dreamliner. A single AJ10 engine provides the spacecraft's primary propulsion, while eight R-4D-11 engines, and six pods of custom reaction control system engines developed by Airbus, provide the spacecraft's secondary propulsion. Orion is intended to be launched atop a Space Launch System (SLS) rocket, with a tower launch escape system.
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