Les Johnson

Propulsive Small Expendable Deployer System Experiment

Relatively short electrodynamic tethers can extract orbital energy to “ push” against a planetary magnetic e eld to achieve propulsion without the expenditure of propellant. The Propulsive Small Expendable Deployer System experiment will use the e ight-proven Small Expendable Deployer System to deploy a 5-km bare aluminum tether from a Delta II upper stage to achieve o 0.4-N drag thrust, thus lowering the altitude of the stage. The experiment willuseapredominantly baretetherforcurrentcollection in lieuoftheendmasscollectorandinsulated tetherused on previous missions. The e ight experiment is a precursor to a more ambitious electrodynamic tether upper-stage demonstration mission that will be capable of orbit-raising, -lowering, and -inclination changes, all using electrodynamic thrust. The expected performance of the tether propulsion system during the experiment is described.

Mission Analysis of Spinning Systems for Transfers from Low Orbits to Geostationary

An analysis of the use of spaceborne spinning tethers for a reusable system to transfer payloads with a mass up to 4000 kg from low orbits to geostationary is presented. Results indicate that a two-stage system is lighter than a single-stage tethered system with present-day tether materials. A e rst stage in low orbit and a second stage in medium Earth orbit provide the required velocity increments for injecting the payload into geotransfer orbit with the e nal orbit circularization provided by the satellite kick motor. The orbits of the stages are resonant in order to provide periodic encounters and are optimized with the goal of reducing the overall system mass. The close-approach dynamics between the second stage and the payload released from the erst stage is simulated to demonstrate the salient features of the rendezvous process. A total of 10 transfers over two years of operation without refueling is adopted for computing the propellant needed to reboost the stages. A preliminary analysis leads totheconclusion that atwo-stage tethered system is more competitive, on amassbasis, than achemicalupper stage after two transfers.

Overview of future NASA tether applications

Abstract The groundwork has been laid for tether applications in space. NASA has developed tether technology for space applications since the 1960s. Important recent milestones include retrieval of a tether in space (TSS-1, 1992), successful deployment of a 20-km-long tether in space (SEDS-1, 1993), closed loop control of tether deployment (SEDS-2, 1994), and operation of an electrodynamic tether with tether current driven in both directions—power and thrust modes (PMG, 1993). Various types of tethers and systems can be used for space transportation. Short electrodynamic tethers can use solar power to “push” against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The planned Propulsive Small Expendable Deployer System (ProSEDS) experiment will demonstrate electrodynamic tether thrust during its flight in early 2000. Utilizing completely different physical principles, long nonconducting tethers can exchange momentum between two masses in orbit to place one body into a higher orbit or a transfer orbit for lunar and planetary missions. Recently completed system studies of this concept indicate that it would be a relatively low-cost, in-space asset with long-term, multimission capability. Tethers can also be used to support space science by providing a mechanism for precision formation flying and for reaching regions of the upper atmosphere that were previously inaccessible.

International Space Station electrodynamic tether reboost

The International Space Station (ISS) will require periodic reboost due to atmospheric aerodynamic drag. This is nominally achieved through the use of thruster firings by the attached Progress M spacecraft. Many Progress flights to the ISS are required annually. Electrodynamic tethers provide an attractive alternative in that they can provide periodic reboost or continuous drag cancellation using no consumables, propellant, nor conventional propulsion elements. The system could also serve as an emergency backup reboost system used only in the event resupply and reboost are delayed for some reason. The system also has direct application to spacecraft and upper stage propulsion. Electrodynamic tethers have been demonstrated in space previously with the plasma motor generator (PMG) experiment and the Tethered Satellite System Reflight (TSS-1R). The advanced electrodynamic tether proposed for ISS reboost has significant advantages over previous systems in that higher thrust is achievable with significantly shorter tethers and without the need for an active current collection device, hence making the system simpler and much less expensive.The International Space Station (ISS) will require periodic reboost due to atmospheric aerodynamic drag. This is nominally achieved through the use of thruster firings by the attached Progress M spacecraft. Many Progress flights to the ISS are required annually. Electrodynamic tethers provide an attractive alternative in that they can provide periodic reboost or continuous drag cancellation using no consumables, propellant, nor conventional propulsion elements. The system could also serve as an emergency backup reboost system used only in the event resupply and reboost are delayed for some reason. The system also has direct application to spacecraft and upper stage propulsion. Electrodynamic tethers have been demonstrated in space previously with the plasma motor generator (PMG) experiment and the Tethered Satellite System Reflight (TSS-1R). The advanced electrodynamic tether proposed for ISS reboost has significant advantages over previous systems in that higher thrust is achievable with significantly sh...

Propulsive Small Expendable Deployer System (ProSEDS) space experiment

ProSEDS is a secondary (i.e. piggyback) payload on a Delta-11 GPS 8 mission scheduled for launch in August 2000. It will test the feasibility of generating generate electrodynamic thrust without propellant using a 5 kilometer conducting wire (tether). The ProSEDS obtains thrust as the tether cuts across the magnetic field, a voltage is induced across the wire. Electrons are attracted to the positively based far end of the wire. Electrons flow downward through the conductive tether. Earths magnetic field exerts a drag force on the current in the tether segments, that is mechanically transferred via the wire to the stage. The primary objective for the ProSEDs mission is to demonstrate that a significant, measurable electrodynamic thrust through a tether in space. The primary mission will last one day, as the primary battery assures at least three orbits of data will be collected, the remaining power will be provided by the secondary battery, which uses tether generated power to recharge. The extended mission begins using the power provided through the tether, and wil terminate when a system ceases to function; (i.e., either degradation of the tether,through Atomic Oxygen contact, a micrometeoroid or other debris impact, or another malfunction.) The technology has many potential applications. Amongst the applications, which are reviewed in detail, are: (1) satellite deorbit, (2) reboost of the International Space Station, (3) propellantless reusable Orbit Transfer Vehicles, (4) Propulsion and power generation for future Jovian missions.

Near Earth Asteroid (NEA) Scout

NASA is developing solar sail propulsion for a near-term Near Earth Asteroid (NEA) reconnaissance mission that will lay the groundwork for the future use of solar sails. The NEA Scout mission will use the sail as primary propulsion allowing it to survey and image one NEAs of interest for future human exploration. NEA Scout will launch on the first mission of the Space Launch System (SLS) in 2018. After its first encounter with the Moon, NEA Scout will enter the sail characterization phase by the 86 square meter sail deployment. A mechanical Active Mass Translation (AMT) system, combined with the remaining ACS propellant, will be used for sail momentum management. The spacecraft will perform a series of lunar flybys to achieve optimum departure trajectory before beginning its two year-long cruise. About one month before the asteroid flyby, NEA Scout will start its approach phase using optical navigation on top of radio tracking. The solar sail will provide NEA Scout continuous low thrust to enable a relatively slow flyby of the target asteroid under lighting conditions favorable to geological imaging. Once complete, NASA will have demonstrated the capability to fly low-cost, high delta V CubeSats to perform interplanetary missions.

Gossamer Roadmap Technology Reference Study for a Multiple NEO Rendezvous Mission

A technology reference study for a multiple near-Earth object (NEO) rendezvous mission with solar sailcraft is currently carried out by the authors of this paper. The investigated mission builds on previous concepts, but adopts a strong micro-spacecraft philosophy based on the DLR/ESA Gossamer technology. The main scientific objective of the mission is to explore the diversity of NEOs. After direct interplanetary insertion, the solar sailcraft should—within less than 10 years—rendezvous three NEOs that are not only scientifically interesting, but also from the point of human spaceight and planetary defense. In this paper, the objectives of the study are outlined and a preliminary potential mission profile is presented.

Electrodynamic Tethers for Reboost of the International Space Station and Spacecraft Propulsion

The International Space Station (ISS) will require periodic reboost due to atmospheric aerodynamic drag. This is nominally achieved through the use of thruster firings by the attached Progress M spacecraft. Many Progress flights to the ISS are required annually. Electrodynamic tethers provide an attractive alternative in that they can provide periodic reboost or continuous drag cancellation using no consumables, propellant nor conventional propulsion elements. The system could also serve as an emergency backup reboost system used only in the event resupply and reboost are delayed for some reason. The system also has direct application to spacecraft and upper stage propulsion. Electrodynamic tethers have been demonstrated in space previously with the Plasma Motor Generator (PMG) experiment and the Tethered Satellite System (TSS-IR). The advanced electrodynamic tether proposed for ISS reboost has significant advantages over previous systems in that hi-her thrust is achievable with significantly shorter tethers and without the need for an active current collection device, hence making the system simpler and much less expensive.

Solar Sails: Technology And Demonstration Status

Solar Sail propulsion has been validated in space (IKAROS, 2010) and soon several more solar-sail propelled spacecraft will be flown. Using sunlight for spacecraft propulsion is not a new idea. First proposed by Frederick Tsander and Konstantin Tsiolkovsky in the 1920’s, NASA’s Echo 1 balloon, launched in 1960, was the first spacecraft for which the effects of solar photon pressure were measured. Solar sails reflect sunlight to achieve thrust, thus eliminating the need for costly and often very-heavy fuel. Such “propellantless” propulsion will enable whole new classes of space science and exploration missions previously not considered possible due to the propulsive-intense maneuvers and operations required.

Propulsive Small Expendable Deployer System (ProSEDS) Space Demonstration

The Propulsive Small Expendable Deployer System (ProSEDS) space experiment will demonstrate the use of an electrodynamic tether propulsion system. The flight experiment is a precursor to the more ambitious electrodynamic tether upper stage demonstration mission which will be capable of orbit raising, lowering and inclination changing—all using electrodynamic thrust. ProSEDS, which is planned to fly in 2000, will use the flight-proven Small Expendable Deployer System (SEDS) to deploy a tether (5-km bare wire plus 15-km spectra) from a Delta II upper stage to achieve ∼0.4N drag thrust, thus deorbiting the stage. The experiment will use a predominantly ‘bare’ tether for current collection in lieu of the endmass collector and insulated tether approach used on previous missions. ProSEDS will utilize tether-generated current to provide limited spacecraft power. In addition to the use of this technology to provide orbit transfer of payloads and upper stages from low-Earth orbit (LEO) to higher orbits, it may also be an attractive option for future missions to Jupiter and any other planetary body with a magnetosphere.