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89-430: A number of space tethers have been deployed in space missions. Tether satellites can be used for various purposes including research into tether propulsion , tidal stabilisation and orbital plasma dynamics. The missions have met with varying degrees of success; a few have been highly successful. Tethered satellites are composed of three parts: the base-satellite; tether; and sub-satellite. The base-satellite contains

178-461: A "characteristic length", L c , which is also known as its "self-support length" and is the length of untapered cable it can support in a constant 1 g gravity field. where σ is the stress limit (in pressure units) and ρ is the density of the material. Hypersonic skyhook equations use the material's "specific velocity" which is equal to the maximum tangential velocity a spinning hoop can attain without breaking: For rotating tethers (rotovators)

267-551: A 1-km tether. Two of the CubeSat modules ("Ted" and "Ralph") were intended as end-masses on the deployed tether, while the third ("Gadget") served as a climber that could move up and down the tether. The experiment used a multi-line " Hoytether " designed to be damage–resistant. The objectives of the MAST experiment were to obtain on-orbit data on the survivability of space tethers in the micrometeorite/debris orbital environment, to study

356-416: A 32 km tether to deorbit a small re-entry capsule, "Fotino." The YES2 satellite was launched on 14 September 2007 from Baikonur . The communications system on the capsule failed, and the capsule was lost, but deployment telemetry indicated that the tether deployed to full length and that the capsule presumably deorbited as planned. It has been calculated that Fotino was inserted into a trajectory towards

445-576: A 35 km (22 mi) double-strand tether, and planned to deorbit a probe at near-interplanetary speed by swinging deployment of the tether system. The orbit achieved was not as initially planned for the tether experiment and, for safety considerations, the tether was not deployed. 10 years after YES, its successor, the Young Engineers' Satellite 2 (YES2) was flown. The YES2 was a 36 kg student-built tether satellite, part of ESA 's Foton-M3 microgravity mission. The YES2 satellite employed

534-526: A 4,000 meter tether. The two tethered objects were called "Ralph" and "Norton". TiPS was visible from the ground with binoculars or a telescope and was occasionally accidentally spotted by amateur astronomers. The tether broke in July 2006. This long-term statistical data point is in line with debris models published by J. Carroll after the SEDS-2 mission, and ground tests by D. Sabath from TU Muenchen. Predictions of

623-412: A CubeSat secondary payload aboard H-IIA flight 15, which also launched GOSAT . After launch, the satellite was named KUKAI, and consisted of two subsatellites, "Ku" and "Kai," to be linked by a 5-meter (16 ft) tether. It was successfully separated from the rocket and transferred into the planned orbit, but the tether deployed only to a length of several centimeters, "due to the launch lock trouble of

712-710: A Skyhook, while spacecraft bound for higher orbit, or returning from higher orbit, would use the upper end. In 2000, NASA and Boeing considered a HASTOL concept, where a rotating tether would take payloads from a hypersonic aircraft (at half of orbital velocity) to orbit . A tether satellite is a satellite connected to another by a space tether. A number of satellites have been launched to test tether technologies, with varying degrees of success. There are many different (and overlapping) types of tether. Momentum exchange tethers are one of many applications for space tethers. Momentum exchange tethers come in two types; rotating and non-rotating. A rotating tether will create

801-452: A University CubeSat Space Mission Candidate, and the project successfully delivered hardware for flight. In January 2021, MiTEE-1 launched to space on Virgin Orbit 's LauncherOne test flight. The Cooperative High Altitude Rocket Gun Experiment (CHARGE) 2 was jointly developed by Japan and NASA, to observe the current collection along with other phenomena. The major objective was to measure

890-426: A controlled force on the end-masses of the system due to centrifugal acceleration. While the tether system rotates, the objects on either end of the tether will experience continuous acceleration; the magnitude of the acceleration depends on the length of the tether and the rotation rate. Momentum exchange occurs when an end body is released during the rotation. The transfer of momentum to the released object will cause

979-407: A current that can generate either thrust or drag from a planetary magnetic field , in much the same way as an electric motor does. These can be either rotating tethers, or non-rotating tethers , that capture an arriving spacecraft and then release it at a later time into a different orbit with a different velocity. Momentum exchange tethers can be used for orbital maneuvering , or as part of

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1068-478: A cut 3.7 days after deployment. The payload reentered (as expected) within hours, but the 7.2 km (4.5 mi) length at the Delta end survived with no further cuts until re-entry on 7 May 1994. The tether was an easy naked-eye object when lit by the sun and viewed against a dark sky. In these experiments, tether models were verified, and the tests demonstrated that a reentry vehicle can be downwardly deployed into

1157-778: A landing site in Kazakhstan , but no signal was received. The capsule was not recovered. The Kounotori Integrated Tether Experiment (KITE) was a test of tether technology on the Japanese H-II Transfer Vehicle (HTV) 6 space station resupply vehicle, launched by the Japan Aerospace Exploration Agency (JAXA) in December 2016. After undocking from the International Space Station on 27 January 2016, it

1246-414: A mass of 84 and 131 kg, connected by a spinning tether. The flight established a record for the length of an electrodynamic tether in space at that time, 958 m (3,143 ft). The tether was a teflon -coated, stranded tin-copper wire of 0.85 mm (0.033 in) diameter and it was deployed from a spool-type reel located on the forward subpayload. OEDIPUS C was launched on 6 November 1995 from

1335-542: A maximum of two years survivability for TiPS based on some other ground tests have shown to be overly pessimistic (e.g. McBride/Taylor, Penson). The early cut of the SEDS-2 therewith must be considered an anomaly possibly related to the impact of upper stage debris. The Advanced Tether Experiment (ATEx), was a follow on to the TiPS experiment, designed and built by the Naval Center for Space Technology. ATEx flew as part of

1424-403: A modular staged tether system maybe used to achieve the same goal. Multiple tethers would be used between stages. The number of tethers would determine the strength of any given cross-section. For rotating tethers not significantly affected by gravity, the thickness also varies, and it can be shown that the area, A, is given as a function of r (the distance from the centre) as follows: where R

1513-688: A planetary-surface-to-orbit / orbit-to-escape-velocity space transportation system. This is typically a non-conductive tether that accurately maintains a set distance between multiple space vehicles flying in formation. A form of solar wind sail with electrically charged tethers that will be pushed by the momentum of solar wind ions . A concept for suspending an object from a tether orbiting in space. Many uses for space tethers have been proposed, including deployment as space elevators , as skyhooks , and for doing propellant-free orbital transfers. Konstantin Tsiolkovsky (1857–1935) once proposed

1602-531: A protective coating is needed, including relative to UV and atomic oxygen . For applications that exert high tensile forces on the tether, the materials need to be strong and light. Some current tether designs use crystalline plastics such as ultra-high-molecular-weight polyethylene , aramid or carbon fiber . A possible future material would be carbon nanotubes , which have an estimated tensile strength between 140 and 177  GPa (20.3 and 25.7 million psi; 1.38 and 1.75 million atm), and

1691-547: A proven tensile strength in the range 50–60 GPa (7.3–8.7 million psi; 490,000–590,000 atm) for some individual nanotubes. (A number of other materials obtain 10 to 20 GPa (1.5 to 2.9 million psi; 99,000 to 197,000 atm) in some samples on the nano scale, but translating such strengths to the macro scale has been challenging so far, with, as of 2011, CNT-based ropes being an order of magnitude less strong, not yet stronger than more conventional carbon fiber on that scale). For some applications,

1780-534: A reentry orbit using tethers. A follow-on experiment, the Plasma Motor Generator (PMG), used the SEDS deployer to deploy a 500-m tether to demonstrate electrodynamic tether operation. The PMG was planned to test the ability of a Hollow Cathode Assembly (HCA) to provide a low–impedance bipolar electric current between a spacecraft and the ionosphere. In addition, other expectations were to show that

1869-481: A set of ordinary and partial nonlinear, non-autonomous and coupled differential equations . These conditions create a list of dynamical issues to consider: In 1966, Gemini 11 deployed a 30 m (98 ft) tether which was stabilized by a rotation which gave 0.00015 g. Tethered Satellite System-1 (TSS-1) was proposed by NASA and the Italian Space Agency (ASI) in the early 1970s by Mario Grossi, of

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1958-461: A single point, rather than two objects. The experimenters suggest that this may have been due to the tether extending, but being tangled by rebound. A third STARS mission, the STARS-C cubesat, was a 2U cubesat designed to deploy a 100 m (330 ft) aramid fiber tether with a diameter of 0.4 mm (0.016 in) between a mother satellite and a daughter satellite. The cubesat was designed by

2047-399: A specific height above the surface of the celestial body, but lower than (A). Instead of rotating end for end, tethers can also be kept straight by the slight difference in the strength of gravity over their length. A non-rotating tether system has a stable orientation that is aligned along the local vertical (of the earth or other body). This can be understood by inspection of the figure on

2136-457: A spin rate is beyond the capability of the satellite's attitude control. Therefore, after rocket firing but before satellite release, the yo-yo weights are used to reduce the spin rates to something the satellite can cope with in normal operation (often 2-5 RPM). Yo-yo de-spin systems are commonly used on sub-orbital sounding rocket flights, as the vehicles are spin stabilized through ascent and have minimal flight time for roll cancellation using

2225-414: A station-keeping phase (in particular if the target state is a vertical system orientation), and, sometimes, if the deployment system allows, a retraction. The station-keeping phase and retraction phase need active control for stability, especially when atmospheric effects are taken into account. When there are no simplifying assumptions, the dynamics become overly difficult because they are then governed by

2314-539: A team from Shizuoka University . The satellite has a mass of 2.66 kg (5.9 lb). It was launched on 9 December 2016, from the JEM Small Satellite Orbital Deployer on the International Space Station, and re-entered on 2 March 2018. However, the signal quality was intermittent, possibly due to failure of deployment of the solar panel, and data on tether deployment was not obtained. Estimates from orbital drag measurements suggest that

2403-463: A tether satellite, which can operate on electromagnetic principles as generators , by converting their kinetic energy to electrical energy , or as motors , converting electrical energy to kinetic energy. Electric potential is generated across a conductive tether by its motion through the Earth's magnetic field. The choice of the metal conductor to be used in an electrodynamic tether is determined by

2492-401: A tower so tall that it reached into space, so that it would be held there by the rotation of Earth . However, at the time, there was no realistic way to build it. In 1960, another Russian, Yuri Artsutanov , wrote in greater detail about the idea of a tensile cable to be deployed from a geosynchronous satellite , downwards towards the ground, and upwards away, keeping the cable balanced. This

2581-579: A variety of factors. Primary factors usually include high electrical conductivity and low density . Secondary factors, depending on the application, include cost, strength, and melting point. An electrodynamic tether was profiled in the documentary film Orphans of Apollo as technology that was to be used to keep the Russian space station Mir in orbit. This is the use of a (typically) non-conductive tether to connect multiple spacecraft. Tethered Experiment for Mars inter-Planetary Operations (TEMPO³)

2670-427: A video of deployment was transmitted to the ground. Successful tether deployment was verified, as was the fast ignition of a hollow cathode in the space environment. The experiment demonstrated a "Foldaway Flat Tether Deployment System". The educational experiment featured the first bare tape tether deployment ( i.e. without insulation, the tether itself acts as anode and collects electrons). 130 m (430 ft) of

2759-405: Is a device used to reduce the spin of satellites , typically soon after launch. It consists of two lengths of cable with weights on the ends. The cables are wrapped around the final stage and/or satellite, in the manner of a double yo-yo . When the weights are released, the spin of the rocket flings them away from the spin axis . This transfers enough angular momentum to the weights to reduce

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2848-402: Is a proposed 2011 experiment to study the technique. A theoretical type of non-rotating tethered satellite system, it is a concept for providing space-based support to things suspended above an astronomical object. The orbital system is a coupled mass system wherein the upper supporting mass (A) is placed in an orbit around a given celestial body such that it can support a suspended mass (B) at

2937-568: Is fully reversible, and therefore was capable of generating power and orbit boosting modes. The hollow cathode was able to provide a low–power way of connecting the current to and from the ambient plasma. This means that the HC demonstrated its electron collection and emission capabilities. The Tether Physics and Survivability Experiment (TiPS) was launched in 1996 as a project of the US Naval Research Laboratory ; it incorporated

3026-463: Is the space elevator idea, a type of synchronous tether that would rotate with the Earth. However, given the materials technology of the time, this too was impractical on Earth. In the 1970s, Jerome Pearson independently conceived the idea of a space elevator, sometimes referred to as a synchronous tether, and, in particular, analyzed a lunar elevator that can go through the L1 and L2 points , and this

3115-585: Is the radius of tether, v is the velocity with respect to the centre, M is the tip mass, δ {\displaystyle \delta } is the material density, and T is the design tensile strength. Integrating the area to give the volume and multiplying by the density and dividing by the payload mass gives a payload mass / tether mass ratio of: where erf is the normal probability error function . Let V r = V / V c {\displaystyle V_{r}=V/V_{c}\,} , then: This equation can be compared with

3204-458: Is used. Such an arrangement is colloquially named a "yo-weight." When the final stage is a solid rocket , the stage may continue to thrust slightly even after spacecraft release. This is from residual fuel and insulation in the motor casing outgassing , even without significant combustion. In a few cases, the spent stage has rammed the payload, for example in the fourth launch attempt of Ohsumi , third stage of Lambda 4S rocket collided with

3293-411: Is very unlikely that multiple redundant cables would be damaged near the same point on the cable, and hence a very large amount of total damage can occur over different parts of the cable before failure occurs. Beanstalks and rotovators are currently limited by the strengths of available materials. Although ultra-high strength plastic fibers ( Kevlar and Spectra ) permit rotovators to pluck masses from

3382-552: The Poker Flat Research Range north of Fairbanks, Alaska on a Black Brant XII sounding rocket. The flight reached an apogee of 843 km (524 mi) and deployed a tether of the same type used in the OEDIPUS-A to a length of 1,174 m (3,852 ft). It included a Tether Dynamics Experiment to derive theory and develop simulation and animation software for analyses of multi–body dynamics and control of

3471-453: The STEX (Space Technology Experiment) mission. ATEx had two end masses connected by a polyethylene tether that was intended to deploy to a length of 6 km (3.7 mi), and was intended to test a new tether deployment scheme, new tether material, active control, and survivability. ATEx was deployed on 16 January 1999 and ended 18 minutes later after deploying only 22 m of tether. The jettison

3560-703: The Smithsonian Astrophysical Observatory , and Giuseppe Colombo , of Padua University. It was a joint NASA- Italian Space Agency project, was flown in 1992, during STS-46 aboard the Space Shuttle Atlantis from 31 July to 8 August. The purposes of the TSS-1 mission were to verify the tether concept of gravity gradient stabilization, and to provide a research facility for investigating space physics and plasma electrodynamics. This mission uncovered several aspects about

3649-496: The University of Michigan is a cubesat experiment designed measure electrical current along a tether at different lengths between 10 and 30 meters (33 and 98 ft). It was to deploy a subsatellite of approximately 8 cm × 8 cm × 2 cm (3.15 in × 3.15 in × 0.79 in) from a 3U CubeSat to test satellite electrodynamics tethers in the space environment. In 2015, NASA selected MiTEE as

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3738-603: The Van Allen belts can have markedly lower life than those that stay in low earth orbit or are kept outside Earth's magnetosphere. Tether properties and materials are dependent on the application. However, there are some common properties. To achieve maximum performance and low cost, tethers would need to be made of materials with the combination of high strength or electrical conductivity and low density. All space tethers are susceptible to space debris or micrometeoroids. Therefore, system designers will need to decide whether or not

3827-401: The lunar surface. It would also be able to hold 100 cargo vehicles, each with a mass of 580 kg (1,280 lb), evenly spaced along the length of the elevator. Other materials that could be used are T1000G carbon fiber, Spectra 2000, or Zylon. For gravity stabilized tethers, to exceed the self-support length the tether material can be tapered so that the cross-sectional area varies with

3916-465: The rocket equation , which is proportional to a simple exponent on a velocity, rather than a velocity squared. This difference effectively limits the delta-v that can be obtained from a single tether. In addition the cable shape must be constructed to withstand micrometeorites and space junk . This can be achieved with the use of redundant cables, such as the Hoytether ; redundancy can ensure that it

4005-414: The " yo-yo de-spin " mechanism, often used in systems where a probe set spinning during a solid rocket injection motor firing, but needs the spin removed during flight. In this mechanism, weights on the end of long cables are deployed away from the body of the spinning satellite. When the cables are cut, much or all of the angular momentum of the spin is transferred to the discarded weights. As an example,

4094-528: The Ionospheric Plasma ;— a Unique Strategy") consisted of two sounding rocket experiments that used spinning, conductive tethers as a double probe for measurements of weak electric fields in the aurora. They were launched using Black Brant 3-stage sounding rockets. OEDIPUS A launched on 30 January 1989 from Andøya in Norway. The tethered payload consisted of two spinning subpayloads with

4183-579: The Japanese Aerospace Exploration Agency (ISAS/JAXA), was launched on sounding rocket S-520-25 from Uchinoura Space Center , Japan, reaching a maximum altitude of 309 km (192 mi). T-Rex was developed by an international team led by the Kanagawa Institute of Technology/Nihon University to test a new type of electrodynamic tether (EDT). The 300 m (980 ft) tape tether deployed as scheduled and

4272-558: The changing resistance in the tether, the charged particle distributions around a highly charged spherical satellite, and the ambient electric field. In addition, a significant finding concerns the current collection at different potentials on a spherical endmass. Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three. A more descriptive explanation of these results can be found in Thompson, et al. Improvements have been made in modeling

4361-422: The coast of Mexico. The reentry was accurate enough that a pre-positioned observer was able to videotape the payload re-entry and burnup. SEDS-2 was launched on a Delta (along with a GPS Block 2 satellite) on 9 March 1994. A feedback braking limited the swing after deployment to 4°. The payload returned data for 8 hours until its battery died; during this time tether torque spun it up to 4 rpm. The tether suffered

4450-444: The deployment mechanism and prevented deployment to full extension. Despite this issue, the results showed that the basic concept of long gravity-gradient stabilized tethers was sound. It also settled several short deployment dynamics issues, reduced safety concerns, and clearly demonstrated the feasibility of deploying the satellite to long distances. The voltage and current reached using the short tether length were too low for most of

4539-446: The dynamics of tethered formations of spacecraft and rotating tether systems, and to demonstrate momentum-exchange tether concepts. The experiment hardware was designed under a NASA Small Business Technology Transfer (STTR) collaboration between Tethers Unlimited, Inc. and Stanford University , with TUI developing the tether, tether deployer, tether inspection subsystem, satellite avionics, and software, and Stanford students developing

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4628-405: The dynamics of the tethered system, although the satellite did not fully deploy. It stuck at 78 meters; after that snag was resolved its deployment continued to a length of 256 meters (840 ft) before sticking again, where the effort finally ended (the total proposed length was 20,000 meters (66,000 ft)). A protruding bolt due to a late-stage modification of the deployment reel system, jammed

4717-601: The electron charging of the shuttle and how it affects current collection, and in the interaction of bodies with surrounding plasma, as well as the production of electrical power. A second mission, TSS-2, had been proposed to use the tether concept for upper atmospheric experimentation, but was never flown. Longer tether systems have also been used on satellite missions, both operationally (as yo-yo despin systems) and in missions designed to test tether concepts and dynamics. Short tether systems are commonly used on satellites and robotic space probes. Most notably, tethers are used in

4806-628: The experiments to be run. However, low-voltage measurements were made, along with recording the variations of tether-induced forces and currents. New information was gathered on the "return-tether" current. The mission was reflown in 1996 as TSS-1R. Four years later, as a follow-up mission to TSS-1, the TSS-1R satellite was released in latter February 1996 from the Space Shuttle Columbia on the STS-75 mission. The TSS-1R mission objective

4895-406: The feasibility of the idea and gave direction to the study of tethered systems, especially tethered satellites. In 1990, Eagle Sarmont proposed a non-rotating Orbiting Skyhook for an Earth-to-orbit / orbit-to-escape-velocity Space Transportation System in a paper titled "An Orbiting Skyhook: Affordable Access to Space". In this concept a suborbital launch vehicle would fly to the bottom end of

4984-415: The first successful flights of long tethers in orbit, and demonstrated both mechanical and electrodynamic tether operation. The first fully successful orbital flight test of a long tether system was SEDS-1, which tested the simple deploy-only Small Expendable Deployer System. The tether swung to the vertical and was cut after one orbit. This slung the payload and tether from Guam onto a reentry trajectory off

5073-409: The improved versions listed here, but these are currently tracked on radar and have predictable orbits. Although thrusters could be used to change the orbit of the system, a tether could also be temporally wiggled in the right place, using less energy, to dodge known pieces of junk. Radiation, including UV radiation tend to degrade tether materials, and reduce lifespan. Tethers that repeatedly traverse

5162-413: The lower mass. The system must move at a single speed, so the tether must therefore slow down the lower mass and speed up the upper one. The centrifugal force of the tethered upper body is increased, while that of the lower-altitude body is reduced. This results in the centrifugal force of the upper body and the gravitational force of the lower body being dominant. This difference in forces naturally aligns

5251-401: The mission configuration could function as an orbit-boosting motor as well as a generator, by converting orbital energy into electricity. The tether was a 500 m length of insulated 18 gauge copper wire. The mission was launched on 26 June 1993, as the secondary payload on a Delta II rocket. The total experiment lasted approximately seven hours. In that time, the results demonstrated that current

5340-646: The more efficient and lighter the tether can be in relation to the payloads that they can carry. Eventually however, the mass of the tether propulsion system will be limited at the low end by other factors such as momentum storage. Proposed materials include Kevlar , ultra-high-molecular-weight polyethylene , carbon nanotubes and M5 fiber . M5 is a synthetic fiber that is lighter than Kevlar or Spectra. According to Pearson, Levin, Oldson, and Wykes in their article "The Lunar Space Elevator", an M5 ribbon 30 mm (1.2 in) wide and 0.023 mm (0.91 mils) thick, would be able to support 2,000 kg (4,400 lb) on

5429-589: The payload charging and return currents during periods of electron emission. Secondary objectives were related to plasma processes associated with direct current and pulsed firings of a low-power electron beam source. On 14 December 1985, the CHARGE mission was launched at White Sands Missile Range , New Mexico. The results indicated that it is possible to enhance the electron current collection capability of positively charged vehicles by means of deliberate neutral gas releases into an undisturbed space plasma. In addition, it

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5518-478: The payload's attitude control system. As an example of yo-yo de-spin, on the Dawn spacecraft , roughly 3 kilograms (6.6 lb) of weights, and 12-metre (39 ft) cables, reduced the initial spin rate of the 1,420-kilogram (3,130 lb) spacecraft from 46 RPM to 3 RPM in the opposite direction. The relatively small weights have a large effect since they are far from the spin axis, and their effect increases as

5607-408: The right where two spacecraft at two different altitudes have been connected by a tether. Normally, each spacecraft would have a balance of gravitational (e.g. F g1 ) and centrifugal (e.g. F c1 ) forces, but when tied together by a tether, these values begin to change with respect to one another. This phenomenon occurs because, without the tether, the higher-altitude mass would travel slower than

5696-621: The rotating tether to lose energy, and thus lose velocity and altitude. However, using electrodynamic tether thrusting, or ion propulsion the system can then re-boost itself with little or no expenditure of consumable reaction mass. A skyhook is a theoretical class of orbiting tether propulsion intended to lift payloads to high altitudes and speeds. Proposals for skyhooks include designs that employ tethers spinning at hypersonic speed for catching high speed payloads or high altitude aircraft and placing them in orbit. Electrodynamic tethers are long conducting wires, such as one deployed from

5785-469: The satellite structures and assisting with the avionics design, as a part of the University CubeSat program. In April 2007 the MAST was launched as a secondary payload on a Dnepr rocket into a 98°, 647 km × 782 km (402 mi × 486 mi) orbit. The experiment team made contact with the "Gadget" picosatellite, but not with "Ted", the tether-deployer picosatellite. While

5874-500: The spin of the satellite to the desired value. Subsequently, the weights are often released. De-spin is needed since some final stages are spin-stabilized , and require fairly rapid rotation (now typically 30-60 rpm; some early missions, such as Pioneer , rotated at over 600 rpm ) to remain stable during firing. (See, for example, the Star 48 , a solid fuel rocket motor.) After firing, the satellite cannot be simply released, since such

5963-507: The spinning tether configuration, provide dynamics and control expertise for the suborbital tethered vehicle and for the science investigations, develop an attitude stabilization scheme for the payloads and support OEDIPUS C payload development, and acquire dynamics data during flight to compare with pre-flight simulation. On 31 August 2010, an experiment by the Japan Aerospace Exploration Agency (JAXA) on space tether experiment called "Tether Technologies Rocket Experiment" (T-REX), sponsored by

6052-419: The square of the length of the cables. Yo-yo de-spin was invented, built, and tested at Caltech 's Jet Propulsion Laboratory . Yo-yo hardware can contribute to the space debris problem on orbital missions, but this is not a problem when used on the upper stages of earth escape missions such as Dawn , as the cables and weights are also on an escape trajectory. Sometimes only a single weight and cable

6141-611: The sub-satellite and tether until deployment. Sometimes the base-satellite is another basic satellite, other times it could be a spacecraft, space station, or the Moon. The tether is what keeps the two satellites connected. The sub-satellite is released from the base assisted by a spring ejection system, centrifugal force or gravity gradient effects. Tethers can be deployed for a range of applications, including electrodynamic propulsion, momentum exchange, artificial gravity, deployment of sensors or antennas etc. Tether deployment may be followed by

6230-509: The surface of the Moon and Mars, a rotovator from these materials cannot lift from the surface of the Earth. In theory, high flying, supersonic (or hypersonic ) aircraft could deliver a payload to a rotovator that dipped into Earth's upper atmosphere briefly at predictable locations throughout the tropic (and temperate) zone of Earth. As of May 2013, all mechanical tethers (orbital and elevators) are on hold until stronger materials are available. Yo-yo de-spin A yo-yo de-spin mechanism

6319-509: The system along the local vertical, as seen in the figure. Objects in low Earth orbit are subjected to noticeable erosion from atomic oxygen due to the high orbital speed with which the molecules strike as well as their high reactivity. This could quickly erode a tether. Simple single-strand tethers are susceptible to micrometeoroids and space junk . Several systems have since been proposed and tested to improve debris resistance: Large pieces of junk would still cut most tethers, including

6408-508: The system was designed so that the satellites would separate even if communications were not established to the tether deployer, the system did not fully deploy. Radar measurements show the tether deployed just 1 meter. The Space Tethered Autonomous Robotic Satellite (STARS or Kukai ) mission, developed by the Kagawa Satellite Development Project at Kagawa University , Japan, was launched 23 January 2009 as

6497-493: The tensile force on the tether is projected to be less than 65 newtons (15 lbf). Material selection in this case depends on the purpose of the mission and design constraints. Electrodynamic tethers, such as the one used on TSS-1R, may use thin copper wires for high conductivity (see EDT ). There are design equations for certain applications that may be used to aid designers in identifying typical quantities that drive material selection. Space elevator equations typically use

6586-405: The tether broke. The break was attributed to an electrical discharge through a broken place in the insulation. Despite the termination of the tether deployment before full extension, the extension achieved was long enough to verify numerous scientific speculations. These findings included the measurements of the motional EMF, the satellite potential, the orbiter potential, the current in the tether,

6675-425: The tether deployed to a length of about 30 meters. ESTCube-1 was an Estonian mission to test an electric sail in orbit, launched in 2013. It was designed to deploy a tether using centrifugal deployment, but the tether failed to deploy. Tether Electrodynamic Propulsion CubeSat Experiment (TEPCE) was a Naval Research Laboratory electrodynamic tether experiment based on a "triple CubeSat " configuration, which

6764-481: The tether reel mechanism." A follow-on satellite, STARS-II, was a 9 kg (20 lb) satellite designed to fly a 300 m (980 ft) electrodynamic tether made from ultra-thin wires of stainless steel and aluminium. One objective of this program was to demonstrate possible technology for de-orbiting space debris. The mission launched on 27 February 2014 as a secondary payload aboard an H-2A rocket, and re-entered two months later, on 26 April 2014. The experiment

6853-419: The third stage of NASA's Dawn Mission utilized two weights with 1.44 kg (3.2 lb) each deployed on 12-meter (39 ft) cables. In 1993 and 1994, NASA launched three missions using the "Small Expendable Deployer System" (SEDS), which deployed 20 km (12 mi) (SEDS-1 and SEDS-2) and 500-meter (1,600 ft) (PMG) tethers attached to a spent Delta-II second stage. The three experiments were

6942-415: The total load at each point along the length of the cable. In practice this means that the central tether structure needs to be thicker than the tips. Correct tapering ensures that the tensile stress at every point in the cable is exactly the same. For very demanding applications, such as an Earth space elevator, the tapering can reduce the excessive ratios of cable weight to payload weight. In lieu of tapering

7031-527: The total of 300 m (980 ft) of tether was deployed fire-hose style, purely driven by inertia and limited by friction, following a powerful, spring-initiated ejection. Accurate differential GPS data of the deployment was recorded, and video taken from the endmasses. The use of a bare section of a space-borne electrodynamic tether for an electron-collection device has been suggested as a promising alternative to end-body electron collectors for certain electrodynamic tether applications. The bare-tether concept

7120-403: The value used is the material's 'characteristic velocity' which is the maximum tip velocity a rotating untapered cable can attain without breaking, The characteristic velocity equals the specific velocity multiplied by the square root of two. These values are used in equations similar to the rocket equation and are analogous to specific impulse or exhaust velocity. The higher these values are,

7209-577: Was built by 2012 and due to be launched in 2013, but eventually launched as a secondary payload as part of the STP-2 launch on a Falcon Heavy in June 2019. The tether deployed in November 2019 to detect electrodynamic force on the tether's orbit. TEPCE used two nearly identical endmasses with a STACER spring between them to start the deployment of a 1 km long braided-tape conducting tether. Passive braking

7298-483: Was found to be possible with materials then existing. In 1977, Hans Moravec and later Robert L. Forward investigated the physics of non-synchronous skyhooks , also known as rotating skyhooks, and performed detailed simulations of tapered rotating tethers that could pick objects off, and place objects onto, the Moon , Mars and other planets , with little loss, or even a net gain of energy. In 1979, NASA examined

7387-609: Was intended to deploy a 700-meter (2,300 feet) electrodynamic tether, however, a failure resulted in the tether not deploying. The vehicle burned up in the atmosphere without deployment. The experiment did successful demonstrate a carbon nanotube field-emission cathode. CubeSats are small, low-cost satellites that are typically launched as secondary payloads on other missions, often built and operated as student projects. Several CubeSat missions have attempted to deploy tethers, so far without success. The Multi-Application Survivable Tether (MAST) launched three 1-kg CubeSat modules with

7476-411: Was observed that the release of neutral gas or argon gas into the undisturbed plasma region surrounding a positively biased platform has been found to cause enhancements to electron current collection. This was due to the fact that a fraction of the gas was ionized, which increased the local plasma density, and therefore the level of return current. OEDIPUS ("Observations of Electric-field Distribution in

7565-399: Was only partially successful, and tether deployment could not be confirmed. The orbit decayed from 350 km (220 mi) to 280 km (170 mi) in 50 days, considerably faster than the other CubeSats launched on the same mission, an indirect indication that its tether deployed, increasing the drag. However, telescopic photography of the satellite from the ground showed the satellite as

7654-806: Was to be tested first during NASA's Propulsive Small Expendable Deployer System (ProSEDS) mission. While the mission was canceled after NASA's space shuttle Columbia accident, the concept could potentially be undertaken in the future. ElectroDynamic Debris Eliminator (EDDE) was proposed in 2012 as an affordable system to deorbit or gather large orbital debris. The tether is flat for resistance to micromeroid impacts, and would carry large solar panels. Space tether Tether satellites might be used for various purposes, including research into tether propulsion , tidal stabilization and orbital plasma dynamics. Five main techniques for employing space tethers are in development: Electrodynamic tethers are primarily used for propulsion. These are conducting tethers that carry

7743-453: Was to deploy the tether 20.7 km (12.9 mi) above the orbiter and remain there collecting data. The TSS-1R mission was to conduct exploratory experiments in space plasma physics. Projections indicated that the motion of the long conducting tether through the Earth's magnetic field would produce an EMF that would drive a current through the tether system. TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when

7832-546: Was triggered by an automatic protection system designed to save STEX if the tether began to stray from its expected departure angle, which was ultimately caused by excessive slack tether. As a result of the deployment failure, none of the desired ATEx goals were achieved. In 1997, the European Space Agency launched the Young Engineers' Satellite (YES) of about 200 kg (440 lb) into GTO with

7921-528: Was used to reduce speed and hence recoil at the end of deployment. The satellite was intended to drive an electrodynamic current in either direction. It was intended to be able to raise or lower the orbit by several kilometers per day, change libration state, change orbit plane, and actively maneuver. A large change in its decay rate on 17 November suggests the tether was deployed on that date, leading to its rapid reentry, which occurred on 1 February 2020. The Miniature Tether Electrodynamics Experiment (MiTEE) from

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