Centaur (rocket stage)

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https://en.wikipedia.org/wiki/Centaur_(rocket_stage) 

 

Centaur III

A single-engine Centaur III being raised for mating to an Atlas V rocket
Manufacturer	United Launch Alliance
Used on	Atlas V: Centaur III Vulcan: Centaur V Titan IV Space Shuttle: Shuttle-Centaur (cancelled due to Challenger disaster)
General characteristics
Height	12.68 m (499 in)
Diameter	3.05 m (120 in)
Propellant mass	20,830 kg (45,920 lb)
Empty mass	2,247 kg (4,954 lb), single engine 2,462 kg (5,428 lb), dual engine
Centaur III
Powered by	1 or 2 RL10
Maximum thrust	99.2 kN (22,300 lbf), per engine
Specific impulse	450.5 seconds (4.418 km/s)
Burn time	Variable
Propellant	LH2 / LOX
Associated stages
Derivatives	Centaur V Advanced Cryogenic Evolved Stage
Launch history
Status	Active
Total launches	245 as of January 2018
First flight	May 9, 1962

A dual engine Centaur stage

 

Centaur stage during assembly at General Dynamics, 1962

 

Diagram of the Centaur stage tank

The Centaur is a family of rocket propelled upper stages produced by U.S. launch service provider United Launch Alliance, with one main active version and one version under development. The 3.05 m (10.0 ft) diameter Common Centaur/Centaur III flies as the upper stage of the Atlas V launch vehicle, and the 5.4 m (18 ft) diameter Centaur V is being developed as the upper stage of ULA's new Vulcan rocket. Centaur was the first rocket stage to use liquid hydrogen (LH₂) and liquid oxygen (LOX) propellants, a high-energy combination that is ideal for upper stages but has significant handling difficulties.

Characteristics

Common Centaur is built around stainless steel pressure stabilized balloon propellant tanks with 0.51 mm (0.020 in) thick walls. It can lift payloads of up to 19,000 kg (42,000 lb). The thin walls minimize the mass of the tanks, maximizing the stage's overall performance.

A common bulkhead separates the LOX and LH₂ tanks, further reducing the tank mass. It is made of two stainless steel skins separated by a fiberglass honeycomb. The fiberglass honeycomb minimizes heat transfer between the extremely cold LH₂ and relatively warm LOX.

The main propulsion system consists of one or two Aerojet Rocketdyne RL10 engines. The stage is capable of up to twelve restarts, limited by propellant, orbital lifetime, and mission requirements. Combined with the insulation of the propellant tanks, this allows Centaur to perform the multi-hour coasts and multiple engine burns required on complex orbital insertions.

The reaction control system (RCS) also provides ullage and consists of twenty hydrazine monopropellant engines located around the stage in two 2-thruster pods and four 4-thruster pods. For propellant, 150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks and fed to the RCS engines with pressurized helium gas, which is also used to accomplish some main engine functions.

Current versions

As of 2019, all but two of the many Centaur variants had been retired: Common Centaur/Centaur III (active) and Centaur V (in development).

Current engines

Version	Stage used on	Dry mass	Thrust	Isp, vac.	Length	Diameter
RL10A-4-2	Centaur III (DEC)	168 kg (370 lb)	99.1 kN (22,300 lbf)	451 s		1.17 m (3.8 ft)
RL10C-1	Centaur III (SEC), (DCSS)	190 kg (420 lb)	101.8 kN (22,900 lbf)	449.7 s	2.12 m (7.0 ft)	1.45 m (4.8 ft)
RL10C-1-1	Centaur V	188 kg (414 lb)	106 kN (24,000 lbf)	453.8 s	2.46 m (8.1 ft)	1.57 m (5.2 ft)

Centaur III/Common Centaur

Common Centaur is the upper stage of the Atlas V rocket. Earlier Common Centaurs were propelled by the RL10-A-4-2 version of the RL-10. Since 2014, Common Centaur has flown with the RL10-C-1 engine, which is shared with the Delta Cryogenic Second Stage, to reduce costs. The Dual Engine Centaur (DEC) configuration will continue to use the smaller RL10-A-4-2 to accommodate two engines in the available space.

The Atlas V can fly in multiple configurations, but only one affects the way Centaur integrates with the booster and fairing: the 5.4 m (18 ft) diameter Atlas V payload fairing attaches to the booster and encapsulates the upper stage and payload, routing fairing-induced aerodynamic loads into the booster. If the 4 m (13 ft) diameter payload fairing is used, the attachment point is at the top (forward end) of Centaur, routing loads through the Centaur tank structure.

The latest Common Centaurs can accommodate secondary payloads using an Aft Bulkhead Carrier attached to the engine end of the stage.

Single Engine Centaur (SEC)

Most payloads launch on Single Engine Centaur (SEC) with one RL10. This is the variant for all normal flights of the Atlas V (indicated by the last digit of the naming system, for example Atlas V 421).

Dual Engine Centaur (DEC)

A dual engine variant with two RL-10 engines is available, but only in use to launch the CST-100 Starliner crewed spacecraft and possibly the Dream Chaser ISS logistics spaceplane. The higher thrust of two engines allows a gentler ascent with more horizontal velocity and less vertical velocity, which reduces deceleration to survivable levels in the event of a launch abort and ballistic reentry occurring at any point in the flight.

Centaur V

Centaur V will be the upper stage of the new Vulcan launch vehicle currently being developed by the United Launch Alliance to meet the needs of the National Security Space Launch (NSSL) program. Vulcan was initially intended to enter service with an upgraded variant of the Common Centaur, with an upgrade to the Advanced Cryogenic Evolved Stage (ACES) planned after the first few years of flights.

In late 2017, ULA decided to bring elements of the ACES upper stage forward and begin work on Centaur V. Centaur V will have ACES' 5.4 m (18 ft) diameter and advanced insulation, but does not include the Integrated Vehicle Fluids (IVF) feature expected to allow the extension of upper stage on-orbit life from hours to weeks. Centaur V will use 2 different versions of the RL10-C engine with nozzle extensions to improve the fuel consumption for the heaviest payloads. This increased capability over Common Centaur will permit ULA to meet NSSL requirements and retire both the Atlas V and Delta IV Heavy rocket families earlier than initially planned. The new rocket publicly became the Vulcan Centaur in March 2018. In May 2018, the Aerojet Rocketdyne RL10 was announced as Centaur V's engine following a competitive procurement process against the Blue Origin BE-3. Each stage will mount two engines. In September 2020, ULA announced that ACES was no longer being developed, and that Centaur V would be used instead. Tory Bruno, ULA's CEO, stated that the Vulcan’s Centaur 5 will have 40% more endurance and two and a half times more energy than the upper stage ULA currently flies. “But that’s just the tip of the iceberg,” Bruno elaborated. “I’m going to be pushing up to 450, 500, 600 times the endurance over just the next handful of years. That will enable a whole new set of missions that you cannot even imagine doing today.”

History

The Centaur concept originated in 1956 when Convair began studying a liquid hydrogen fueled upper stage. The ensuing project began in 1958 as a joint venture among Convair, the Advanced Research Projects Agency (ARPA), and the U.S. Air Force. In 1959, NASA assumed ARPA's role. Centaur initially flew as the upper stage of the Atlas-Centaur launch vehicle, encountering a number of early developmental issues due to the pioneering nature of the effort and the use of liquid hydrogen. In 1994 General Dynamics sold their Space Systems division to Lockheed-Martin.

Centaur A-D (Atlas)

An Atlas-Centaur rocket launches Surveyor 1

 

Main article: Atlas-Centaur

The Centaur was originally developed for use with the Atlas launch vehicle family. Known in early planning as the 'high-energy upper stage', the choice of the mythological Centaur as a namesake was intended to represent the combination of the brute force of the Atlas booster and finesse of the upper stage.

Initial Atlas-Centaur launches used developmental versions, labeled Centaur-A through -C. The only Centaur-A launch on 8 May 1962 ended in an explosion 54 seconds after liftoff when insulation panels on the Centaur separated early, causing the LH₂ tank to overheat and rupture. After extensive redesigns, the only Centaur-B flight on 26 November 1963 was successful. Centaur-C flew three times with two failures and one launch declared successful although the Centaur failed to restart. Centaur-D was the first version to enter operational service, with fifty-six launches.

On 30 May 1966, an Atlas-Centaur boosted the first Surveyor lander towards the Moon. This was followed by six more Surveyor launches over the next two years, with the Atlas-Centaur performing as expected. The Surveyor program demonstrated the feasibility of reigniting a hydrogen engine in space and provided information on the behavior of LH₂ in space.

By the 1970s, Centaur was fully mature and had become the standard rocket stage for launching larger civilian payloads into high Earth orbit, also replacing the Atlas-Agena vehicle for NASA planetary probes.

By the end of 1989, Centaur-D and -G had been used as the upper stage for 63 Atlas rocket launches, 55 of which were successful.

Saturn I S-V

Main article: S-V

 

A Saturn I launches with a ballasted S-V stage

The Saturn I was designed to fly with a S-V third stage to enable payloads to go beyond low earth orbit (LEO). The S-V stage was intended to be powered by two RL-10A-1 engines burning liquid hydrogen as fuel and liquid oxygen as oxidizer. The S-V stage was flown four times on missions SA-1 through SA-4, all four of these missions had the S-V's tanks filled with water to be used a ballast during launch. The stage was not flown in an active configuration.

Centaur D-1T (Titan III)

A Titan IIIE-Centaur rocket launches Voyager 2

The Centaur D was improved for use on the far more powerful Titan III booster in the 1970s, with the first launch of the resulting Titan IIIE in 1974. The Titan IIIE more than tripled the payload capacity of Atlas-Centaur, and incorporated improved thermal insulation, allowing an orbital lifespan of up to five hours, an increase over the 30 minutes of the Atlas-Centaur.

The first launch of Titan IIIE in February 1974 was unsuccessful, with the loss of the Space Plasma High Voltage Experiment (SPHINX) and a mockup of the Viking probe. It was eventually determined that Centaur's engines had ingested an incorrectly installed clip from the oxygen tank.

The next Titan-Centaurs launched Helios 1, Viking 1, Viking 2, Helios 2, Voyager 1, and Voyager 2. The Titan booster used to launch Voyager 1 had a hardware problem that caused a premature shutdown, which the Centaur stage detected and successfully compensated for. Centaur ended its burn with less than 4 seconds of fuel remaining.

Centaur (Atlas G)

Centaur was introduced on the Atlas G and was carried over to the very similar Atlas I.

Shuttle-Centaur (Centaur G and G-Prime)

Main article: Shuttle-Centaur

 

Illustration of Shuttle-Centaur with Ulysses

Shuttle-Centaur was a proposed Space Shuttle upper stage. To enable its installation in shuttle payload bays, the diameter of the Centaur's hydrogen tank was increased to 4.3 m (14 ft), with the LOX tank diameter remaining at 3.0 m (10 ft). Two variants were proposed: Centaur G Prime, which was planned to launch the Galileo and Ulysses robotic probes, and Centaur G, a shortened version, reduced in length from approximately 9 to 6 m (30 to 20 ft), planned for U.S. DoD payloads and the Magellan Venus probe.

After the Space Shuttle Challenger accident, and just months before the Shuttle-Centaur had been scheduled to fly, NASA concluded that it was too risky to fly the Centaur on the Shuttle. The probes were launched with the much less powerful solid-fueled IUS, with Galileo needing multiple gravitational assists from Venus and Earth to reach Jupiter.

Centaur (Titan IV)

The capability gap left by the termination of the Shuttle-Centaur program was filled by a new launch vehicle, the Titan IV. The 401A/B versions used a Centaur upper stage with a 4.3-meter (14 ft) diameter hydrogen tank. In the Titan 401A version, a Centaur-T was launched nine times between 1994 and 1998. The 1997 Cassini-Huygens Saturn probe was the first flight of the Titan 401B, with an additional six launches wrapping up in 2003 including one SRB failure.

Centaur II (Atlas II/III)

Main article: Atlas II

Centaur II was initially developed for use on the Atlas II series of rockets. Centaur II also flew on the initial Atlas IIIA launches.

Centaur III/Common Centaur (Atlas III/V)

Main article: Atlas III

Atlas IIIB introduced the Common Centaur, a longer and initially dual engine Centaur II.

Atlas V cryogenic fluid management experiments

Most Common Centaurs launched on Atlas V have hundreds to thousands of kilograms of propellants remaining on payload separation. In 2006 these propellants were identified as a possible experimental resource for testing in-space cryogenic fluid management techniques.

In October 2009, the Air Force and United Launch Alliance (ULA) performed an experimental demonstration on the modified Centaur upper stage of DMSP-18 launch to improve "understanding of propellant settling and slosh, pressure control, RL10 chilldown and RL10 two-phase shutdown operations. DMSP-18 was a low mass payload, with approximately 28% (5,400 kg (11,900 lb)) of LH₂/LOX propellant remaining after separation. Several on-orbit demonstrations were conducted over 2.4 hours, concluding with a deorbit burn. The initial demonstration was intended to prepare for more-advanced cryogenic fluid management experiments planned under the Centaur-based CRYOTE technology development program in 2012–2014, and will increase the TRL of the Advanced Cryogenic Evolved Stage Centaur successor.

Mishaps

Although Centaur has a long and successful flight history, it has experienced a number of mishaps:

• April 7, 1966: Centaur did not restart after coast — ullage motors ran out of fuel.
• May 9, 1971; Centaur guidance failed, destroying itself and the Mariner 8 spacecraft bound for Mars orbit.
• April 18, 1991: Centaur failed due to particles from the scouring pads used to clean the propellant ducts getting stuck in the turbopump, preventing start-up.
• August 22, 1992: Centaur failed to restart (icing problem).
• April 30, 1999: Launch of the USA-143 (Milstar DFS-3m) communications satellite failed when a Centaur database error resulted in uncontrolled roll rate and loss of attitude control, placing the satellite in a useless orbit.
• June 15, 2007: the engine in the Centaur upper stage of an Atlas V shut down early, leaving its payload — a pair of National Reconnaissance Office ocean surveillance satellites — in a lower than intended orbit. The failure was called "A major disappointment," though later statements claim the spacecraft will still be able to complete their mission. The cause was traced to a stuck-open valve that depleted some of the hydrogen fuel, resulting in the second burn terminating four seconds early. The problem was fixed, and the next flight was nominal.
• August 30, 2018: Atlas V Centaur passivated second stage launched on September 17, 2014 broke up, creating space debris.
• March 23–25, 2018: Atlas V Centaur passivated second stage launched on September 8, 2009 broke up.
• April 6, 2019: Atlas V Centaur passivated second stage launched on October 17, 2018 broke up.

Centaur III specifications

Source: Atlas V551 specifications, as of 2015.

• Diameter: 3.05 m (10 ft)
• Length: 12.68 m (42 ft)
• Inert mass: 2,247 kg (4,954 lb)
• Fuel: Liquid hydrogen
• Oxidizer: Liquid oxygen
• Fuel and oxidizer mass: 20,830 kg (45,922 lb)
• Guidance: Inertial
• Thrust: 99.2 kN (22,300 lbf)
• Burn time: Variable; e.g., 842 seconds on Atlas V
• Engine: RL10-C-1
• Engine length: 2.32 m (7.6 ft)
• Engine diameter: 1.53 m (5 ft)
• Engine dry weight: 168 kg (370 lb)
• Engine start: Restartable
• Attitude control: 4 27-N thrusters, 8 40-N thrusters
  • Propellant: Hydrazine

Dragonfly (spacecraft)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Dragonfly_(spacecraft) 

Dragonfly

Spacecraft concept illustration
Mission type	Rotorcraft on Titan
Operator	NASA
COSPAR ID
Website	https://dragonfly.jhuapl.edu/
Mission duration	10 years (planned) Science phase: 3.3 years
Spacecraft properties
Spacecraft type	Rotorcraft lander
Manufacturer	Applied Physics Laboratory
Landing mass	≈450 kg (990 lb)
Power	70 watts (desired) from an MMRTG
Start of mission
Launch date	June 2027 (planned)
Rocket	Atlas V 411 or equivalent performance (actual launch vehicle will be selected later)
Launch site	TBA
Contractor	TBA
Titan aircraft
Landing date	2034
Landing site	Shangri-La dune fields
Distance flown	8 km (5.0 mi) per flight (planned)
Instruments
Dragonfly Mass Spectrometer (DraMS) Dragonfly Gamma-Ray and Neutron Spectrometer (DraGNS) Dragonfly Geophysics and Meteorology Package (DraGMet)
Dragonfly Mission Insignia New Frontiers program ← OSIRIS-REx

Dragonfly is a planned spacecraft and NASA mission, which will send a robotic rotorcraft to the surface of Titan, the largest moon of Saturn. It would be the first aircraft on Titan and is intended to make the first powered and fully controlled atmospheric flight on any moon, with the intention of studying prebiotic chemistry and extraterrestrial habitability. It will then use its vertical takeoffs and landings (VTOL) capability to move between exploration sites.

Titan is unique in having an abundant, complex, and diverse carbon-rich chemistry on the surface of a water-ice-dominated world with an interior water ocean, making it a high-priority target for astrobiology and origin of life studies. The mission was proposed in April 2017 to NASA's New Frontiers program by the Johns Hopkins Applied Physics Laboratory (APL), and was selected as one of two finalists (out of twelve proposals) in December 2017 to further refine the mission's concept. On 27 June 2019, Dragonfly was selected to become the fourth mission in the New Frontiers program.

Overview

Mission concept illustration

Dragonfly is an astrobiology mission to Titan to assess its microbial habitability and study its prebiotic chemistry at various locations. Dragonfly will perform controlled flights and vertical takeoffs and landings between locations. The mission will involve flights to multiple different locations on the surface, which allows sampling of diverse regions and geological contexts.

Titan is a compelling astrobiology target because its surface contains abundant complex carbon-rich chemistry and because both liquid water and liquid hydrocarbons can occur on its surface, possibly forming a prebiotic primordial soup.

A successful flight of Dragonfly will make it the second rotorcraft to fly on a celestial body other than Earth, following the success of a Martian technology demonstration UAV helicopter, Ingenuity, which landed on Mars with the Perseverance rover on 18 February 2021 as part of the Mars 2020 mission and successfully achieved powered flight on 19 April 2021.

History

The previously passed over TSSM mission proposed a Titan aircraft in the form of a Montgolfier balloon with a boat-lander gondola.

The initial Dragonfly conception took place over a dinner conversation between scientists Jason W. Barnes of Department of Physics, University of Idaho, (who had previously made the AVIATR proposal for a Titan aircraft) and Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory, and it took 15 months to make it a detailed mission proposal. The principal investigator is Elizabeth Turtle, a planetary scientist at the Johns Hopkins Applied Physics Laboratory.

The Dragonfly mission builds on several earlier studies of Titan mobile aerial exploration, including the 2007 Titan Explorer Flagship study, which advocated a Montgolfier balloon for regional exploration, and AVIATR, an airplane concept considered for the Discovery program. The concept of a rotorcraft lander that flew on battery power, recharged during the 8-Earth-day Titan night from a radioisotope power source, was proposed by Lorenz in 2000. More recent discussion has included a 2014 Titan rotorcraft study by Larry Matthies, at the Jet Propulsion Laboratory, that would have a small rotorcraft deployed from a lander or a balloon. The hot-air balloon concepts would have used the heat from a radioisotope thermoelectric generator (RTG).

Leveraging proven rotorcraft systems and technologies, Dragonfly will use a multi-rotor vehicle to transport its instrument suite to multiple locations to make measurements of surface composition, atmospheric conditions, and geologic processes.

Dragonfly and CAESAR, a comet sample return mission to 67P/Churyumov–Gerasimenko, were the two finalists for the New Frontiers program Mission 4, and on 27 June 2019, NASA selected Dragonfly for development; it will launch in June 2027.

Funding

The CAESAR and Dragonfly missions received US$4 million funding each through the end of 2018 to further develop and mature their concepts. NASA announced the selection of Dragonfly on 27 June 2019, which will be built and launched by June 2027. Dragonfly will be the fourth in NASA's New Frontiers portfolio, a series of principal investigator-led planetary science investigations that fall under a development cost cap of approximately US$850 million, and including launch services, the total cost will be approximately US$1 billion.

Science objectives

Titan is similar to the very early Earth, and can provide clues to how life may have arisen on Earth. In 2005, the European Space Agency's Huygens lander acquired some atmospheric and surface measurements on Titan, detecting tholins, which are a mix of various types of hydrocarbons (organic compounds) in the atmosphere and on the surface. Because Titan's atmosphere obscures the surface at many wavelengths, the specific compositions of solid hydrocarbon materials on Titan's surface remain essentially unknown. Measuring the compositions of materials in different geologic settings will reveal how far prebiotic chemistry has progressed in environments that provide known key ingredients for life, such as pyrimidines (bases used to encode information in DNA) and amino acids, the building blocks of proteins.

Areas of particular interest are sites where extraterrestrial liquid water in impact melt or potential cryovolcanic flows may have interacted with the abundant organic compounds. Dragonfly will provide the capability to explore diverse locations to characterize the habitability of Titan's environment, investigate how far prebiotic chemistry has progressed, and search for biosignatures indicative of life based on water as solvent and even hypothetical types of biochemistry.

The atmosphere contains plentiful nitrogen and methane, and strong evidence indicates that liquid methane exists on the surface. Evidence also indicates the presence of liquid water and ammonia under the surface, which may be delivered to the surface by cryovolcanic activity.

Design and construction

Titan has a dense atmosphere and low gravity compared to Earth, two factors facilitating propelled flight.

 

The multi-mission radioisotope thermoelectric generator of Mars Science Laboratory, sent to the surface of Mars to power that robotic rover.

Dragonfly will be a rotorcraft lander, much like a large quadcopter with double rotors, an octocopter. Redundant rotor configuration will enable the mission to tolerate the loss of at least one rotor or motor. Each of the craft's eight rotors will be about 1 m (3.3 ft) in diameter. The aircraft will travel at about 10 m/s (36 km/h; 22 mph) and climb to an altitude of up to 4 km (13,000 ft).

Flight on Titan is aerodynamically benign as Titan has low gravity and little wind, and its dense atmosphere allows for efficient rotor propulsion. The radioisotope thermoelectric generator (RTG) power source has been proven in multiple spacecraft, and the extensive use of quad drones on Earth provides a well-understood flight system that is being complemented with algorithms to enable independent actions in real-time. The craft will be designed to operate in a space radiation environment and in temperatures averaging 94 K (−179.2 °C).

Titan's dense atmosphere and low gravity mean that the flight power for a given mass is a factor of about 40 times lower than on Earth. The atmosphere has 1.45 times the pressure and about four times the density of Earth's, and local gravity (13.8% of Earth's) will make it easier to fly, although cold temperatures, lower light levels and higher atmospheric drag on the airframe will be challenges.

Dragonfly will be able to fly several kilometers, powered by a lithium-ion battery, which will be recharged by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) during the night. MMRTGs convert the heat from the natural decay of a radioisotope into electricity. The rotorcraft will be able to travel ten kilometers on every battery charge and stay aloft for a half hour each time. The vehicle will use sensors to scout new science targets, and then return to the original site until new landing destinations are approved by mission controllers.

The Dragonfly rotorcraft will be approximately 450 kg (990 lb), and packaged inside a 3.7 m (12 ft) diameter heatshield. Regolith samples will be obtained by two sample acquisition drills and hoses, one on each landing skid, for delivery to the mass spectrometer instrument.

An artist's concept of the Dragonfly rotorcraft-lander approaching a site on Titan.

The craft will remain on the ground during the Titan nights, which last about 8 Earth days or 192 hours. Activities during the night may include sample collection and analysis, seismological studies like diagnosing wave activity on the northern hydrocarbon seas, meteorological monitoring, and local microscopic imaging using LED illuminators as flown on Phoenix lander and Curiosity rover. The craft will communicate directly to Earth with a high-gain antenna.

The Penn State Vertical Lift Research Center of Excellence is responsible for rotor design and analysis, rotorcraft flight-control development, scaled rotorcraft testbed development, ground testing support, and flight performance assessment.

Scientific payload

• DraMS (Dragonfly Mass Spectrometer) is a mass spectrometer to identify chemical components, especially those relevant to biological processes, in surface and atmospheric samples.
• DraGNS (Dragonfly Gamma-Ray and Neutron Spectrometer), consists of a deuterium-tritium Pulsed Neutron Generator and a set of a gamma-ray spectrometer and neutron spectrometer to identify the surface composition under the lander.
• DraGMet (Dragonfly Geophysics and Meteorology Package) is a suite of meteorological sensors including a seismometer.
• DragonCam (Dragonfly Camera Suite) is a set of microscopic and panoramic cameras to image Titan's terrain and scout for scientifically interesting landing sites.
• In addition, Dragonfly will use multiple engineering and monitoring instruments to determine characteristics of Titan's interior and atmosphere.

Trajectory

Dragonfly is expected to launch in June 2027, and will take seven years to reach Titan, arriving by 2034. The spacecraft will perform a gravitational assist flyby of Venus, and three passes by Earth to gain additional velocity. The spacecraft will be the first dedicated outer solar system mission to not visit Jupiter as it will not be within the flight path at the time of launch.

Entry and descent

The cruise stage will separate from the entry capsule ten minutes before encountering Titan's atmosphere. The lander will descend to the surface of Titan using an aeroshell and a series of two parachutes, while the spent cruise stage will burn up in uncontrolled atmospheric entry. The duration of the descent phase is expected to be 105 minutes. The aeroshell is derived from the Genesis sample return capsule, and the PICA heat shield is similar to MSL and Mars 2020 design and will protect the spacecraft for the first 6 minutes of its descent.

At a speed of Mach 1.5, a drogue parachute will deploy, to slow the capsule to subsonic speeds. Due to Titan's comparably thick atmosphere and low gravity, the drogue chute phase will last for 80 minutes. A larger main parachute will replace the drogue chute when the descent speed is sufficiently low. During the 20 minutes on the main chute, the lander will be prepared for separation. The heat shield will be jettisoned, the landing skids will be extended, and sensors such as radar and lidar will be activated. At an altitude of 1.2 km (0.75 mi), the lander will be released from its parachute, for a powered flight to the surface. The specific landing site and flight operation will be performed autonomously. This is required since the high gain antenna will not be deployed during descent, and because communication between Earth and Titan takes 70–90 minutes, each way.

Landing site

Shangri-La is the large, dark region at the center of this infrared image of Titan.

 

The Selk impact crater on Titan, as imaged by the Cassini orbiter's radar, is 90 km (56 mi) in diameter.

The Dragonfly rotorcraft will land initially in dunes to the southeast of the Selk impact structure at the edge of the dark region called Shangri-La. It will explore this region in a series of flights of up to 8 km (5.0 mi) each, and acquire samples from compelling areas with a diverse geography. After landing it will travel to the Selk impact crater, where in addition to tholin organic compounds, there is evidence of past liquid water.

The Selk crater is a geologically young impact crater 90 km (56 mi) in diameter, located about 800 km (500 mi) north-northwest of the Huygens lander. (7.0°N 199.0°W) Infrared measurements and other spectra by the Cassini orbiter show that the adjacent terrain exhibits a brightness suggestive of differences in thermal structure or composition, possibly caused by cryovolcanism generated by the impact — a fluidized ejecta blanket and fluid flows, now water ice. Such a region featuring a mix of organic compounds and water ice is a compelling target to assess how far the prebiotic chemistry may have progressed at the surface.

Germanium

From Wikipedia, the free encyclopedia

Germanium, ₃₂Ge

Germanium
Pronunciation	/dʒɜːrˈmeɪniəm/ ​(jur-MAY-nee-əm)
Appearance	grayish-white
Standard atomic weight Ar°(Ge)	72.630±0.008 72.630±0.008 (abridged)
Germanium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Si ↑ Ge ↓ Sn gallium ← germanium → arsenic
Atomic number (Z)	32
Group	group 14 (carbon group)
Period	period 4
Block	p-block
Electron configuration	[Ar] 3d10 4s2 4p2
Electrons per shell	2, 8, 18, 4
Physical properties
Phase at STP	solid
Melting point	1211.40 K ​(938.25 °C, ​1720.85 °F)
Boiling point	3106 K ​(2833 °C, ​5131 °F)
Density (near r.t.)	5.323 g/cm3
when liquid (at m.p.)	5.60 g/cm3
Heat of fusion	36.94 kJ/mol
Heat of vaporization	334 kJ/mol
Molar heat capacity	23.222 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1644 1814 2023 2287 2633 3104
Atomic properties
Oxidation states	−4 −3, −2, −1, 0, +1, +2, +3, +4 (an amphoteric oxide)
Electronegativity	Pauling scale: 2.01
Ionization energies	1st: 762 kJ/mol 2nd: 1537.5 kJ/mol 3rd: 3302.1 kJ/mol
Atomic radius	empirical: 122 pm
Covalent radius	122 pm
Van der Waals radius	211 pm
Spectral lines of germanium
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered diamond-cubic
Speed of sound thin rod	5400 m/s (at 20 °C)
Thermal expansion	6.0 µm/(m⋅K)
Thermal conductivity	60.2 W/(m⋅K)
Electrical resistivity	1 Ω⋅m (at 20 °C)
Band gap	0.67 eV (at 300 K)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−76.84×10−6 cm3/mol
Young's modulus	103 GPa
Shear modulus	41 GPa
Bulk modulus	75 GPa
Poisson ratio	0.26
Mohs hardness	6.0
CAS Number	7440-56-4
History
Naming	after Germany, homeland of the discoverer
Prediction	Dmitri Mendeleev (1869)
Discovery	Clemens Winkler (1886)
Main isotopes of germanium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 68Ge syn 270.95 d ε 68Ga 70Ge 20.52% stable 71Ge syn 11.3 d ε 71Ga 72Ge 27.45% stable 73Ge 7.76% stable 74Ge 36.7% stable 76Ge 7.75% 1.78×1021 y β−β− 76Se
Category: Germanium references

Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbors silicon and tin. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature.

Because it seldom appears in high concentration, germanium was discovered comparatively late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element along with silver and sulfur, in an uncommon mineral called argyrodite. Although the new element somewhat resembled arsenic and antimony in appearance, the combining ratios in compounds agreed with Mendeleev's predictions for a relative of silicon. Winkler named the element after his country, Germany. Today, germanium is mined primarily from sphalerite (the primary ore of zinc), though germanium is also recovered commercially from silver, lead, and copper ores.

Elemental germanium is used as a semiconductor in transistors and various other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Presently, the major end uses are fibre-optic systems, infrared optics, solar cell applications, and light-emitting diodes (LEDs). Germanium compounds are also used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a large number of organogermanium compounds, such as tetraethylgermanium, useful in organometallic chemistry. Germanium is considered a technology-critical element.

Germanium is not thought to be an essential element for any living organism. Some complex organic germanium compounds are being investigated as possible pharmaceuticals, though none have yet proven successful. Similar to silicon and aluminium, naturally-occurring germanium compounds tend to be insoluble in water and thus have little oral toxicity. However, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins.

History

Prediction of germanium, "?=70" (periodic table 1869)

In his report on The Periodic Law of the Chemical Elements in 1869, the Russian chemist Dmitri Mendeleev predicted the existence of several unknown chemical elements, including one that would fill a gap in the carbon family, located between silicon and tin. Because of its position in his periodic table, Mendeleev called it ekasilicon (Es), and he estimated its atomic weight to be 70 (later 72).

In mid-1885, at a mine near Freiberg, Saxony, a new mineral was discovered and named argyrodite because of its high silver content. The chemist Clemens Winkler analyzed this new mineral, which proved to be a combination of silver, sulfur, and a new element. Winkler was able to isolate the new element in 1886 and found it similar to antimony. He initially considered the new element to be eka-antimony, but was soon convinced that it was instead eka-silicon. Before Winkler published his results on the new element, he decided that he would name his element neptunium, since the recent discovery of planet Neptune in 1846 had similarly been preceded by mathematical predictions of its existence. However, the name "neptunium" had already been given to another proposed chemical element (though not the element that today bears the name neptunium, which was discovered in 1940). So instead, Winkler named the new element germanium (from the Latin word, Germania, for Germany) in honor of his homeland. Argyrodite proved empirically to be Ag₈GeS₆. Because this new element showed some similarities with the elements arsenic and antimony, its proper place in the periodic table was under consideration, but its similarities with Dmitri Mendeleev's predicted element "ekasilicon" confirmed that place on the periodic table. With further material from 500 kg of ore from the mines in Saxony, Winkler confirmed the chemical properties of the new element in 1887. He also determined an atomic weight of 72.32 by analyzing pure germanium tetrachloride (GeCl
₄), while Lecoq de Boisbaudran deduced 72.3 by a comparison of the lines in the spark spectrum of the element.

Winkler was able to prepare several new compounds of germanium, including fluorides, chlorides, sulfides, dioxide, and tetraethylgermane (Ge(C₂H₅)₄), the first organogermane. The physical data from those compounds—which corresponded well with Mendeleev's predictions—made the discovery an important confirmation of Mendeleev's idea of element periodicity. Here is a comparison between the prediction and Winkler's data:

Property	Ekasilicon Mendeleev prediction (1871)	Germanium Winkler discovery (1887)
atomic mass	72.64	72.63
density (g/cm3)	5.5	5.35
melting point (°C)	high	947
color	gray	gray
oxide type	refractory dioxide	refractory dioxide
oxide density (g/cm3)	4.7	4.7
oxide activity	feebly basic	feebly basic
chloride boiling point (°C)	under 100	86 (GeCl4)
chloride density (g/cm3)	1.9	1.9

Until the late 1930s, germanium was thought to be a poorly conducting metal. Germanium did not become economically significant until after 1945 when its properties as an electronic semiconductor were recognized. During World War II, small amounts of germanium were used in some special electronic devices, mostly diodes. The first major use was the point-contact Schottky diodes for radar pulse detection during the War. The first silicon-germanium alloys were obtained in 1955. Before 1945, only a few hundred kilograms of germanium were produced in smelters each year, but by the end of the 1950s, the annual worldwide production had reached 40 metric tons (44 short tons).

The development of the germanium transistor in 1948 opened the door to countless applications of solid state electronics. From 1950 through the early 1970s, this area provided an increasing market for germanium, but then high-purity silicon began replacing germanium in transistors, diodes, and rectifiers. For example, the company that became Fairchild Semiconductor was founded in 1957 with the express purpose of producing silicon transistors. Silicon has superior electrical properties, but it requires much greater purity that could not be commercially achieved in the early years of semiconductor electronics.

Meanwhile, the demand for germanium for fiber optic communication networks, infrared night vision systems, and polymerization catalysts increased dramatically. These end uses represented 85% of worldwide germanium consumption in 2000. The US government even designated germanium as a strategic and critical material, calling for a 146 ton (132 tonne) supply in the national defense stockpile in 1987.

Germanium differs from silicon in that the supply is limited by the availability of exploitable sources, while the supply of silicon is limited only by production capacity since silicon comes from ordinary sand and quartz. While silicon could be bought in 1998 for less than $10 per kg, the price of germanium was almost $800 per kg.

Characteristics

Under standard conditions, germanium is a brittle, silvery-white, semi-metallic element. This form constitutes an allotrope known as α-germanium, which has a metallic luster and a diamond cubic crystal structure, the same as diamond. While in crystal form, germanium has a displacement threshold energy of ${\displaystyle 19.7_{-0.5}^{+0.6}~{\text{eV}}}$. At pressures above 120 kbar, germanium becomes the allotrope β-germanium with the same structure as β-tin. Like silicon, gallium, bismuth, antimony, and water, germanium is one of the few substances that expands as it solidifies (i.e. freezes) from the molten state.

Germanium is a semiconductor. Zone refining techniques have led to the production of crystalline germanium for semiconductors that has an impurity of only one part in 10¹⁰, making it one of the purest materials ever obtained. The first metallic material discovered (in 2005) to become a superconductor in the presence of an extremely strong electromagnetic field was an alloy of germanium, uranium, and rhodium.

Pure germanium is known to spontaneously extrude very long screw dislocations, referred to as germanium whiskers. The growth of these whiskers is one of the primary reasons for the failure of older diodes and transistors made from germanium, as, depending on what they eventually touch, they may lead to an electrical short.

Chemistry

See also: Category:Germanium compounds

Elemental germanium starts to oxidize slowly in air at around 250 °C, forming GeO₂ . Germanium is insoluble in dilute acids and alkalis but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce germanates ([GeO
₃]²⁻
). Germanium occurs mostly in the oxidation state +4 although many +2 compounds are known. Other oxidation states are rare: +3 is found in compounds such as Ge₂Cl₆, and +3 and +1 are found on the surface of oxides, or negative oxidation states in germanides, such as −4 in Mg
₂Ge. Germanium cluster anions (Zintl ions) such as Ge₄²⁻, Ge₉⁴⁻, Ge₉²⁻, [(Ge₉)₂]⁶⁻ have been prepared by the extraction from alloys containing alkali metals and germanium in liquid ammonia in the presence of ethylenediamine or a cryptand. The oxidation states of the element in these ions are not integers—similar to the ozonides O₃⁻.

Two oxides of germanium are known: germanium dioxide (GeO
₂, germania) and germanium monoxide, (GeO). The dioxide, GeO₂ can be obtained by roasting germanium disulfide (GeS
₂), and is a white powder that is only slightly soluble in water but reacts with alkalis to form germanates. The monoxide, germanous oxide, can be obtained by the high temperature reaction of GeO₂ with Ge metal. The dioxide (and the related oxides and germanates) exhibits the unusual property of having a high refractive index for visible light, but transparency to infrared light. Bismuth germanate, Bi₄Ge₃O₁₂, (BGO) is used as a scintillator.

Binary compounds with other chalcogens are also known, such as the disulfide (GeS
₂), diselenide (GeSe
₂), and the monosulfide (GeS), selenide (GeSe), and telluride (GeTe). GeS₂ forms as a white precipitate when hydrogen sulfide is passed through strongly acid solutions containing Ge(IV). The disulfide is appreciably soluble in water and in solutions of caustic alkalis or alkaline sulfides. Nevertheless, it is not soluble in acidic water, which allowed Winkler to discover the element. By heating the disulfide in a current of hydrogen, the monosulfide (GeS) is formed, which sublimes in thin plates of a dark color and metallic luster, and is soluble in solutions of the caustic alkalis. Upon melting with alkaline carbonates and sulfur, germanium compounds form salts known as thiogermanates.

Germane is similar to methane.

Four tetrahalides are known. Under normal conditions GeI₄ is a solid, GeF₄ a gas and the others volatile liquids. For example, germanium tetrachloride, GeCl₄, is obtained as a colorless fuming liquid boiling at 83.1 °C by heating the metal with chlorine. All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide. GeCl₄ is used in the production of organogermanium compounds. All four dihalides are known and in contrast to the tetrahalides are polymeric solids. Additionally Ge₂Cl₆ and some higher compounds of formula Ge_nCl_2n+2 are known. The unusual compound Ge₆Cl₁₆ has been prepared that contains the Ge₅Cl₁₂ unit with a neopentane structure.

Germane (GeH₄) is a compound similar in structure to methane. Polygermanes—compounds that are similar to alkanes—with formula Ge_nH_2n+2 containing up to five germanium atoms are known. The germanes are less volatile and less reactive than their corresponding silicon analogues. GeH₄ reacts with alkali metals in liquid ammonia to form white crystalline MGeH₃ which contain the GeH₃⁻ anion. The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.

Nucleophilic addition with an organogermanium compound.

The first organogermanium compound was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with diethylzinc yielded tetraethylgermane (Ge(C
₂H
₅)
₄). Organogermanes of the type R₄Ge (where R is an alkyl) such as tetramethylgermane (Ge(CH
₃)
₄) and tetraethylgermane are accessed through the cheapest available germanium precursor germanium tetrachloride and alkyl nucleophiles. Organic germanium hydrides such as isobutylgermane ((CH
₃)
₂CHCH
₂GeH
₃) were found to be less hazardous and may be used as a liquid substitute for toxic germane gas in semiconductor applications. Many germanium reactive intermediates are known: germyl free radicals, germylenes (similar to carbenes), and germynes (similar to carbynes). The organogermanium compound 2-carboxyethylgermasesquioxane was first reported in the 1970s, and for a while was used as a dietary supplement and thought to possibly have anti-tumor qualities.

Using a ligand called Eind (1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) germanium is able to form a double bond with oxygen (germanone). Germanium hydride and germanium tetrahydride are very flammable and even explosive when mixed with air.

Isotopes

Main article: Isotopes of germanium

Germanium occurs in 5 natural isotopes: ⁷⁰
Ge
, ⁷²
Ge
, ⁷³
Ge
, ⁷⁴
Ge
, and ⁷⁶
Ge
. Of these, ⁷⁶
Ge
is very slightly radioactive, decaying by double beta decay with a half-life of 1.78×10²¹ years. ⁷⁴
Ge
is the most common isotope, having a natural abundance of approximately 36%. ⁷⁶
Ge
is the least common with a natural abundance of approximately 7%. When bombarded with alpha particles, the isotope ⁷²
Ge
will generate stable ⁷⁷
Se
, releasing high energy electrons in the process. Because of this, it is used in combination with radon for nuclear batteries.

At least 27 radioisotopes have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is ⁶⁸
Ge
, decaying by electron capture with a half-life of 270.95 days. The least stable is ⁶⁰
Ge
, with a half-life of 30 ms. While most of germanium's radioisotopes decay by beta decay, ⁶¹
Ge
and ⁶⁴
Ge
decay by
β⁺
delayed proton emission. Ge
through ⁸⁷
Ge
isotopes also exhibit minor
β⁻
delayed neutron emission decay paths.

Occurrence

See also: Category:Germanium minerals

 

Renierite

Germanium is created by stellar nucleosynthesis, mostly by the s-process in asymptotic giant branch stars. The s-process is a slow neutron capture of lighter elements inside pulsating red giant stars. Germanium has been detected in some of the most distant stars and in the atmosphere of Jupiter.

Germanium's abundance in the Earth's crust is approximately 1.6 ppm. Only a few minerals like argyrodite, briartite, germanite, renierite and sphalerite contain appreciable amounts of germanium. Only few of them (especially germanite) are, very rarely, found in mineable amounts.Some zinc-copper-lead ore bodies contain enough germanium to justify extraction from the final ore concentrate. An unusual natural enrichment process causes a high content of germanium in some coal seams, discovered by Victor Moritz Goldschmidt during a broad survey for germanium deposits. The highest concentration ever found was in Hartley coal ash with as much as 1.6% germanium. The coal deposits near Xilinhaote, Inner Mongolia, contain an estimated 1600 tonnes of germanium.

Production

About 118 tonnes of germanium were produced in 2011 worldwide, mostly in China (80 t), Russia (5 t) and United States (3 t). Germanium is recovered as a by-product from sphalerite zinc ores where it is concentrated in amounts as great as 0.3%, especially from low-temperature sediment-hosted, massive Zn–Pb–Cu(–Ba) deposits and carbonate-hosted Zn–Pb deposits. A recent study found that at least 10,000 t of extractable germanium is contained in known zinc reserves, particularly those hosted by Mississippi-Valley type deposits, while at least 112,000 t will be found in coal reserves. In 2007 35% of the demand was met by recycled germanium.

Year	Cost ($/kg)
1999	1,400
2000	1,250
2001	890
2002	620
2003	380
2004	600
2005	660
2006	880
2007	1,240
2008	1,490
2009	950
2010	940
2011	1,625
2012	1,680
2013	1,875
2014	1,900
2015	1,760
2016	950
2017	1,358
2018	1,300
2019	1,240
2020	1,000

While it is produced mainly from sphalerite, it is also found in silver, lead, and copper ores. Another source of germanium is fly ash of power plants fueled from coal deposits that contain germanium. Russia and China used this as a source for germanium. Russia's deposits are located in the far east of Sakhalin Island, and northeast of Vladivostok. The deposits in China are located mainly in the lignite mines near Lincang, Yunnan; coal is also mined near Xilinhaote, Inner Mongolia.

The ore concentrates are mostly sulfidic; they are converted to the oxides by heating under air in a process known as roasting:

GeS₂ + 3 O₂ → GeO₂ + 2 SO₂

Some of the germanium is left in the dust produced, while the rest is converted to germanates, which are then leached (together with zinc) from the cinder by sulfuric acid. After neutralization, only the zinc stays in solution while germanium and other metals precipitate. After removing some of the zinc in the precipitate by the Waelz process, the residing Waelz oxide is leached a second time. The dioxide is obtained as precipitate and converted with chlorine gas or hydrochloric acid to germanium tetrachloride, which has a low boiling point and can be isolated by distillation:

GeO₂ + 4 HCl → GeCl₄ + 2 H₂O

GeO₂ + 2 Cl₂ → GeCl₄ + O₂

Germanium tetrachloride is either hydrolyzed to the oxide (GeO₂) or purified by fractional distillation and then hydrolyzed. The highly pure GeO₂ is now suitable for the production of germanium glass. It is reduced to the element by reacting it with hydrogen, producing germanium suitable for infrared optics and semiconductor production:

GeO₂ + 2 H₂ → Ge + 2 H₂O

The germanium for steel production and other industrial processes is normally reduced using carbon:

GeO₂ + C → Ge + CO₂

Applications

The major end uses for germanium in 2007, worldwide, were estimated to be: 35% for fiber-optics, 30% infrared optics, 15% polymerization catalysts, and 15% electronics and solar electric applications. The remaining 5% went into such uses as phosphors, metallurgy, and chemotherapy.

Optics

A typical single-mode optical fiber. Germanium oxide is a dopant of the core silica (Item 1).

1. Core 8 µm
2. Cladding 125 µm
3. Buffer 250 µm
4. Jacket 400 µm

The notable properties of germania (GeO₂) are its high index of refraction and its low optical dispersion. These make it especially useful for wide-angle camera lenses, microscopy, and the core part of optical fibers. It has replaced titania as the dopant for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle. At the end of 2002, the fiber optics industry consumed 60% of the annual germanium use in the United States, but this is less than 10% of worldwide consumption. GeSbTe is a phase change material used for its optic properties, such as that used in rewritable DVDs.

Because germanium is transparent in the infrared wavelengths, it is an important infrared optical material that can be readily cut and polished into lenses and windows. It is especially used as the front optic in thermal imaging cameras working in the 8 to 14 micron range for passive thermal imaging and for hot-spot detection in military, mobile night vision, and fire fighting applications. It is used in infrared spectroscopes and other optical equipment that require extremely sensitive infrared detectors. It has a very high refractive index (4.0) and must be coated with anti-reflection agents. Particularly, a very hard special antireflection coating of diamond-like carbon (DLC), refractive index 2.0, is a good match and produces a diamond-hard surface that can withstand much environmental abuse.

Electronics

Silicon-germanium alloys are rapidly becoming an important semiconductor material for high-speed integrated circuits. Circuits utilizing the properties of Si-SiGe junctions can be much faster than those using silicon alone. Silicon-germanium is beginning to replace gallium arsenide (GaAs) in wireless communications devices. The SiGe chips, with high-speed properties, can be made with low-cost, well-established production techniques of the silicon chip industry.

Solar panels are a major use of germanium. Germanium is the substrate of the wafers for high-efficiency multijunction photovoltaic cells for space applications. High-brightness LEDs, used for automobile headlights and to backlight LCD screens, are an important application.

Because germanium and gallium arsenide have very similar lattice constants, germanium substrates can be used to make gallium arsenide solar cells. The Mars Exploration Rovers and several satellites use triple junction gallium arsenide on germanium cells.

Germanium-on-insulator (GeOI) substrates are seen as a potential replacement for silicon on miniaturized chips. CMOS circuit based on GeOI substrates has been reported recently. Other uses in electronics include phosphors in fluorescent lamps and solid-state light-emitting diodes (LEDs). Germanium transistors are still used in some effects pedals by musicians who wish to reproduce the distinctive tonal character of the "fuzz"-tone from the early rock and roll era, most notably the Dallas Arbiter Fuzz Face.

Other uses

A PET bottle

Germanium dioxide is also used in catalysts for polymerization in the production of polyethylene terephthalate (PET). The high brilliance of this polyester is especially favored for PET bottles marketed in Japan. In the United States, germanium is not used for polymerization catalysts.

Due to the similarity between silica (SiO₂) and germanium dioxide (GeO₂), the silica stationary phase in some gas chromatography columns can be replaced by GeO₂.

In recent years germanium has seen increasing use in precious metal alloys. In sterling silver alloys, for instance, it reduces firescale, increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked Argentium contains 1.2% germanium.

Semiconductor detectors made of single crystal high-purity germanium can precisely identify radiation sources—for example in airport security. Germanium is useful for monochromators for beamlines used in single crystal neutron scattering and synchrotron X-ray diffraction. The reflectivity has advantages over silicon in neutron and high energy X-ray applications. Crystals of high purity germanium are used in detectors for gamma spectroscopy and the search for dark matter. Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.

Germanium is emerging as an important material for spintronics and spin-based quantum computing applications. In 2010, researchers demonstrated room temperature spin transport and more recently donor electron spins in germanium has been shown to have very long coherence times.

Germanium and health

Germanium is not considered essential to the health of plants or animals. Germanium in the environment has little or no health impact. This is primarily because it usually occurs only as a trace element in ores and carbonaceous materials, and the various industrial and electronic applications involve very small quantities that are not likely to be ingested. For similar reasons, end-use germanium has little impact on the environment as a biohazard. Some reactive intermediate compounds of germanium are poisonous (see precautions, below).

Germanium supplements, made from both organic and inorganic germanium, have been marketed as an alternative medicine capable of treating leukemia and lung cancer. There is, however, no medical evidence of benefit; some evidence suggests that such supplements are actively harmful.

Some germanium compounds have been administered by alternative medical practitioners as non-FDA-allowed injectable solutions. Soluble inorganic forms of germanium used at first, notably the citrate-lactate salt, resulted in some cases of renal dysfunction, hepatic steatosis, and peripheral neuropathy in individuals using them over a long term. Plasma and urine germanium concentrations in these individuals, several of whom died, were several orders of magnitude greater than endogenous levels. A more recent organic form, beta-carboxyethylgermanium sesquioxide (propagermanium), has not exhibited the same spectrum of toxic effects.

U.S. Food and Drug Administration research has concluded that inorganic germanium, when used as a nutritional supplement, "presents potential human health hazard".

Certain compounds of germanium have low toxicity to mammals, but have toxic effects against certain bacteria.

Precautions for chemically reactive germanium compounds

Some of germanium's artificially produced compounds are quite reactive and present an immediate hazard to human health on exposure. For example, germanium chloride and germane (GeH₄) are a liquid and gas, respectively, that can be very irritating to the eyes, skin, lungs, and throat.