Space tether missions
The sub-satellite is released from the base assisted by a spring ejection system, centrifugal force or gravity gradient effects.
When there are no simplifying assumptions, the dynamics become overly difficult because they are then governed by a set of ordinary and partial nonlinear, non-autonomous and coupled differential equations.
These conditions create a list of dynamical issues to consider:[2] 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 the Smithsonian Astrophysical Observatory, and Giuseppe Colombo, of Padua University.
[3] 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.
A more descriptive explanation of these results can be found in Thompson, et al.[15] Improvements have been made in modeling the electron charging of the shuttle and how it affects current collection,[11] and in the interaction of bodies with surrounding plasma, as well as the production of electrical power.
As an example, 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.
The payload returned data for 8 hours until its battery died; during this time tether torque spun it up to 4 rpm.
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.
[21][22] 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 the mission configuration could function as an orbit-boosting motor as well as a generator, by converting orbital energy into electricity.
In that time, the results demonstrated that current is fully reversible, and therefore was capable of generating power and orbit boosting modes.
[24] 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 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).
[33] CubeSats are small, low-cost satellites that are typically launched as secondary payloads on other missions, often built and operated as student projects.
[37][38] 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 a CubeSat secondary payload aboard H-IIA flight 15, which also launched GOSAT.
[39] After launch, the satellite was named KUKAI, and consisted of two subsatellites, "Ku" and "Kai,"[40] to be linked by a 5-meter (16 ft) tether.
[46][47] 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.
[53] TEPCE used two nearly identical endmasses with a STACER[54] spring between them to start the deployment of a 1 km long braided-tape conducting tether.
[55] 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.
In 2015, NASA selected MiTEE as a University CubeSat Space Mission Candidate,[58] and the project successfully delivered hardware for flight.
[60][61] 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.
Secondary objectives were related to plasma processes associated with direct current and pulsed firings of a low-power electron beam source.
[62] 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.
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.
[9] OEDIPUS ("Observations of Electric-field Distribution in 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.
[63] 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.
[citation needed] OEDIPUS C was launched on 6 November 1995 from 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).
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 bare-tether concept was to be tested first during NASA's Propulsive Small Expendable Deployer System (ProSEDS) mission.
