Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of sp... more Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of space and the near-weightlessness there make it possible to deploy very long and thin tethers. By exploiting basic principles of physics, tethers can provide propellantless propulsion and enable unique applications such as the provision of comfortable artificial gravity or the removal of space debris. Nevertheless there are still no tether applications in use today - there appears to be a "gap of scepticism". A safe tether and deployer system has therefore been designed and verified with the help of simulation and innovative ground testing equipment. Through a hands-on educational approach, the YES and YES2 low-cost space tether experiments have been launched into orbit. In September 2007, all 32 km of the YES2 tether are deployed in orbit. With the help of this tether, a student-built re-entry capsule is deorbited over Kazakhstan. This work reports this design and analysis effort, with the aim to raise confidence in the use of space tethers.
A 35 km tether in pendulum motion can deliver the required Delta-V for a re-entry capsule to retu... more A 35 km tether in pendulum motion can deliver the required Delta-V for a re-entry capsule to return from space (LEO) to Earth, if the tether is cut near the vertical. Goal of this work is to show the feasibility of achieving a high landing site accuracy making the tethered re-entry a serious candidate for a frequent sample return system for the International Space Station. In order to optimize the landing site accuracy, a strategy was developed, called StarTrack: Swinging Tether Assisted Re-entry Through Robust Actively Controlled Kinetics. The StarTrack philosophy includes the concept of an end-to-end simulator. It respectively simulates: • the separation of the re-entry capsule; • the tether deployment, swing and cut; • the atmospheric entry and landing on the Earth's surface.
Four tools were developed and found to be of major importance for reaching an accurate landing site:
• A two stage deployment including a deployment break to recover from the major source of dispersion during the first km of deployment. A first stage length of 1500 m was found to give good results. • The Energy Feedback during the deployment to a large angle. Paths towards a large angle were found that were suitable for the robust Starfrack strategy. Even for large disturbances the Energy Feedback showed excellent performance. Only length and length rate measurements are needed. • The Flex End Brake (FEB), avoiding longitudinal tether oscillations. This braking method is very successful in avoiding residual oscillations in a tether at the end of deployment. At most a 4 meter amplitude for a 35 km tether was observed. It is very fast, there is no loss in Delta-V due to the FEB. No tether slackness is induced. • A cutting time minimizing the influence of the disturbances. Different optimal cutting times exist for the two cases, with and without GPS. With GPS the optimal cutting time can be updated during the swing. For the case without GPS the cutting time is determined by a focussing effect of the disturbances influences. This focussing effect was found thanks to the StarTrack end-to-end philosophy.
Technical report and algorithms for the Lunar Visibility Calculator, a tool that determines visib... more Technical report and algorithms for the Lunar Visibility Calculator, a tool that determines visibility, lighting conditions for lunar topography, intended for study of the Peaks of Eternal Light near the Lunar South Pole, with a test area derived using Clementine data.
Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science, 2001
A satellite mission for synchronized multi point measurements over tens of km in the lower thermo... more A satellite mission for synchronized multi point measurements over tens of km in the lower thermosphere is possible at low cost and in a short time frame. This paper offers three options for providing coordinated multi-point sensing in the lower thermosphere. The ...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, 2003
Artificial gravity through structural rotation is the only known and most direct method that can ... more Artificial gravity through structural rotation is the only known and most direct method that can be expected, when in orbit, to fully prevent bone impairment, musculature decline and reduced autoimmune system. Such a system is thus of special significance for long duration interplanetary flights. Both the NASA and the ESA have manned Mars exploration on their agenda. Currently only the extremes of zero or (greater than) one gee have been investigated for humans. It is shown that only a tether system can yield a lightweight solution to provide a large rotational radius avoiding the disorienting effects usually associated with rotation like the Coriolis force, gravity gradient and gyroscopic cross-coupling. A LEO precursor is necessary to help us understand effects of simulated gravity (rotating reference) on human physiology and select the simulated gravity level during transit. As an important additional benefit, it will allow us a window to the physiological effects of being in a reduced gravity environment such as on the surface of a planet. A unique scientific spin-off is that various data-points can be produced to help prepare for long duration reduced-gravity surface operations (e.g. Moon or Mars). A tethered man-rated LEO facility is thus proposed dubbed "MARS-g": Manned Antecedent for Reduced and Simulated Gravity.
Train passengers and authorities demand trains’ timeliness, comfort, safety and energy efficiency... more Train passengers and authorities demand trains’ timeliness, comfort, safety and energy efficiency. Train fleets, over their multiple-decade lifetimes, will therefore typically undergo various modernizations, in order to improve fleet monitoring and management. It is then advantageous if additional equipment is highly integrated due to lack of on-train space. The IRISS project (Intelligent Railways via Integrated Satellite Services) proposes such an integrated service. It provides Train Operating Companies with essentially uninterrupted monitoring of train stock based on terrestrial and satellite communications, satellite navigation and conventional train metering. IRISS is a feasibility study initiated by the European Space Agency’s Integrated Applications Programme.
"Pipeline integrity management systems (PIMS) are a key concept in the g... more "Pipeline integrity management systems (PIMS) are a key concept in the gas and pipeline industry that aims to ensure that pipeline systems are safe and full-time operational. It addresses infrastructure design & construction, inspection & maintenance, management and documentation. Space Assets for PIMS is a feasibility study of the European Space Agency’s Integrated Application Promotion program. Its objective is to investigate and define services that provide added value to PIMS-related activities by integration of multiple space assets, i.e. Earth Observation (EO), Satellite Navigation and Satellite Communication. The application of PIMS has been particularly successful in steadily reducing the number of incidents in pipeline operation, due to e.g. accidental third party intervention, sabotage, corrosion or landslides. Nevertheless, pipeline monitoring as performed today remains costly and therefore incomprehensive. Significant improvement can still be achieved by more ubiquitous use of Geographical Information Systems (GIS), such as PIMOA, and other innovations. S&T together with EuroPIMS are about to conclude the PIMS Space Assets feasibility study. Involved users are the gas pipeline operators SASOL (South Africa) and GasUnie (The Netherlands). These users have expressed, as a primary need, their interest in a cost reduction of pipeline inspections (surveys) and a more frequent and comprehensive monitoring of various threats to the pipeline integrity. In particular, third party interference has to be better avoided, especially in South Africa. The study has next addressed the added value, feasibility, viability and sustainability of novel services based on integration of multiple space assets into PIMS activities. For example satellite images (SAR, hyperspectral, optical) can be used to detect large industrial vehicles or areas where landslides occur or subsidence takes place. In remote areas the pipeline could be equipped with sensor networks that transmit in-situ measurements via satellite communication to a central data processing facility, where the data is then checked for signs of corrosion and other anomalies. Finally satellite navigation can improve the georeferencing of pipelines and the measurements, overcoming the drawbacks in using traditional station coordinates or paper drawings of the pipeline. The study has so far resulted in a PIMS service design that integrates the PIMS PIMOA software suit with a multi-source and wide area network of sensors. The sensor suite comprises EO imagery instruments (optical & radar) for observing the surrounding conditions of the pipeline, in-situ sensors measuring basic pipeline data, and a communication network to transmit all data into a centralised database for further analysis and processing. The development of a pre-operational service together with the involved users is foreseen as a next step."
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010
The second Young Engineers' Satellite,YES2, is the longest manmade structure launched in 2007 and... more The second Young Engineers' Satellite,YES2, is the longest manmade structure launched in 2007 and is space piggybacked on the Foton-M3 microgravity platform with the objective of a controlled deployment of a 32km tether. This paper introduces the object and the flight results of YES2 and the performance of the satellite is studied in comparison of the simulations and ground tests with respect to the flight results.
55th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, 2004
Several future applications for space tethers such as tethered artificial gravity, space hooks an... more Several future applications for space tethers such as tethered artificial gravity, space hooks and the space elevator, feature high-tension tether deployment of fail-safe tethers. This paper presents the design of a deployer for high-tension flat space tethers that should further strengthen the case for future high-tension space tether applications. The presented tether deployer features two sets of linearly activated pinching plates, which are elastically hinged on cross-flexures. The elastically deforming design avoids the use of bearings and gearboxes. The fixation of the (flat) tether between flat pinching plates avoids bending of the tether, which occurs in a design using friction wheels. The bending of the tether around a friction wheel lowers the allowable tension in the tether, which is avoided in the presented design. The use of elastic hinges in space is growing, but usually the forces that occur are quite small. In the case of the presented tether deployer, the forces are extremely large, which is possible because the width of the tether is about one meter. The plate flexures are as wide as the tether, allowing very large forces. The width of the plate flexures also makes the mechanism very rigid, which is important when the force in the tether is large. The tether deployer design presented in this paper is performed for the case of MARS-g, a low Earth orbit artificial gravity test facility. The tension in the tether can be as high as 400 kN while the resulting tether deployer mechanism weighs only about 500 kilogram for low speed deployment. The design can be adapted for high speed deployment simply by adding a more powerful motor; the tension in the tether will remain the same, only more power is required. The design is therefore easily adaptable for other uses such as space hooks or the space elevator.
Vector-borne diseases such as Malaria, Chikungunya, Dengue and West Nile are a persistent public ... more Vector-borne diseases such as Malaria, Chikungunya, Dengue and West Nile are a persistent public health concern. International trade and travel. as well as changing environmental conditions favours colonisation of new areas by foreign (especially arthropod) species. Some of these species transmit diseases to human, and so their spread represents a significant health risk which needs to be quantified and mapped to facilitate strategic preparedness. VECMAP is a project of the European Space Agency's Integrated Application Promotion program (IAP). Based on needs expressed by national public health agencies and regional mosquito controllers a consortium led by Avia-GIS is developing a service for predicting potential mosquito-related health risks (early warning) and for reducing nuisance (targeted control effort). VECMAP enhances and simplifies traditional mathematical distribution modelling, field and laboratory work with the help of Satellite Navigation and Earth Observation.). Th...
Two new spacecraft attitude determination algorithms, Douma and DUDE (Delta-Utec Douma Extension)... more Two new spacecraft attitude determination algorithms, Douma and DUDE (Delta-Utec Douma Extension), have been developed for star pattern recognition from CCD camera data without a priori knowledge. They combine low memory requirements in the range from 50 to 500 kB and an extremely fast search strategy, independent of the size of the database. It supports a reliability >99.99 and accuracy of 1 arcsec level. This makes the algorithms especially interesting for compact real-time autonomous star sensor units. Goal of the study is to gain the necessary basis to develop a low cost autonomous star sensor for small satellites. The Douma algorithm combines the advantages of the existing Liebe and Quine algorithms. Liebe searches a database of all star triangles that could possibly be observed as being the closest one. Quine includes only the brightest triangles around target stars. Douma searches a list of the triangles that are the 'most likely' ones to be observed by the camera ...
Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of sp... more Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of space and the near-weightlessness there make it possible to deploy very long and thin tethers. By exploiting basic principles of physics, tethers can provide propellantless propulsion and enable unique applications such as the provision of comfortable artificial gravity or the removal of space debris. Nevertheless there are still no tether applications in use today - there appears to be a "gap of scepticism". A safe tether and deployer system has therefore been designed and verified with the help of simulation and innovative ground testing equipment. Through a hands-on educational approach, the YES and YES2 low-cost space tether experiments have been launched into orbit. In September 2007, all 32 km of the YES2 tether are deployed in orbit. With the help of this tether, a student-built re-entry capsule is deorbited over Kazakhstan. This work reports this design and analysis effort, with the aim to raise confidence in the use of space tethers.
A 35 km tether in pendulum motion can deliver the required Delta-V for a re-entry capsule to retu... more A 35 km tether in pendulum motion can deliver the required Delta-V for a re-entry capsule to return from space (LEO) to Earth, if the tether is cut near the vertical. Goal of this work is to show the feasibility of achieving a high landing site accuracy making the tethered re-entry a serious candidate for a frequent sample return system for the International Space Station. In order to optimize the landing site accuracy, a strategy was developed, called StarTrack: Swinging Tether Assisted Re-entry Through Robust Actively Controlled Kinetics. The StarTrack philosophy includes the concept of an end-to-end simulator. It respectively simulates: • the separation of the re-entry capsule; • the tether deployment, swing and cut; • the atmospheric entry and landing on the Earth's surface.
Four tools were developed and found to be of major importance for reaching an accurate landing site:
• A two stage deployment including a deployment break to recover from the major source of dispersion during the first km of deployment. A first stage length of 1500 m was found to give good results. • The Energy Feedback during the deployment to a large angle. Paths towards a large angle were found that were suitable for the robust Starfrack strategy. Even for large disturbances the Energy Feedback showed excellent performance. Only length and length rate measurements are needed. • The Flex End Brake (FEB), avoiding longitudinal tether oscillations. This braking method is very successful in avoiding residual oscillations in a tether at the end of deployment. At most a 4 meter amplitude for a 35 km tether was observed. It is very fast, there is no loss in Delta-V due to the FEB. No tether slackness is induced. • A cutting time minimizing the influence of the disturbances. Different optimal cutting times exist for the two cases, with and without GPS. With GPS the optimal cutting time can be updated during the swing. For the case without GPS the cutting time is determined by a focussing effect of the disturbances influences. This focussing effect was found thanks to the StarTrack end-to-end philosophy.
Technical report and algorithms for the Lunar Visibility Calculator, a tool that determines visib... more Technical report and algorithms for the Lunar Visibility Calculator, a tool that determines visibility, lighting conditions for lunar topography, intended for study of the Peaks of Eternal Light near the Lunar South Pole, with a test area derived using Clementine data.
Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science, 2001
A satellite mission for synchronized multi point measurements over tens of km in the lower thermo... more A satellite mission for synchronized multi point measurements over tens of km in the lower thermosphere is possible at low cost and in a short time frame. This paper offers three options for providing coordinated multi-point sensing in the lower thermosphere. The ...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, 2003
Artificial gravity through structural rotation is the only known and most direct method that can ... more Artificial gravity through structural rotation is the only known and most direct method that can be expected, when in orbit, to fully prevent bone impairment, musculature decline and reduced autoimmune system. Such a system is thus of special significance for long duration interplanetary flights. Both the NASA and the ESA have manned Mars exploration on their agenda. Currently only the extremes of zero or (greater than) one gee have been investigated for humans. It is shown that only a tether system can yield a lightweight solution to provide a large rotational radius avoiding the disorienting effects usually associated with rotation like the Coriolis force, gravity gradient and gyroscopic cross-coupling. A LEO precursor is necessary to help us understand effects of simulated gravity (rotating reference) on human physiology and select the simulated gravity level during transit. As an important additional benefit, it will allow us a window to the physiological effects of being in a reduced gravity environment such as on the surface of a planet. A unique scientific spin-off is that various data-points can be produced to help prepare for long duration reduced-gravity surface operations (e.g. Moon or Mars). A tethered man-rated LEO facility is thus proposed dubbed "MARS-g": Manned Antecedent for Reduced and Simulated Gravity.
Train passengers and authorities demand trains’ timeliness, comfort, safety and energy efficiency... more Train passengers and authorities demand trains’ timeliness, comfort, safety and energy efficiency. Train fleets, over their multiple-decade lifetimes, will therefore typically undergo various modernizations, in order to improve fleet monitoring and management. It is then advantageous if additional equipment is highly integrated due to lack of on-train space. The IRISS project (Intelligent Railways via Integrated Satellite Services) proposes such an integrated service. It provides Train Operating Companies with essentially uninterrupted monitoring of train stock based on terrestrial and satellite communications, satellite navigation and conventional train metering. IRISS is a feasibility study initiated by the European Space Agency’s Integrated Applications Programme.
"Pipeline integrity management systems (PIMS) are a key concept in the g... more "Pipeline integrity management systems (PIMS) are a key concept in the gas and pipeline industry that aims to ensure that pipeline systems are safe and full-time operational. It addresses infrastructure design & construction, inspection & maintenance, management and documentation. Space Assets for PIMS is a feasibility study of the European Space Agency’s Integrated Application Promotion program. Its objective is to investigate and define services that provide added value to PIMS-related activities by integration of multiple space assets, i.e. Earth Observation (EO), Satellite Navigation and Satellite Communication. The application of PIMS has been particularly successful in steadily reducing the number of incidents in pipeline operation, due to e.g. accidental third party intervention, sabotage, corrosion or landslides. Nevertheless, pipeline monitoring as performed today remains costly and therefore incomprehensive. Significant improvement can still be achieved by more ubiquitous use of Geographical Information Systems (GIS), such as PIMOA, and other innovations. S&T together with EuroPIMS are about to conclude the PIMS Space Assets feasibility study. Involved users are the gas pipeline operators SASOL (South Africa) and GasUnie (The Netherlands). These users have expressed, as a primary need, their interest in a cost reduction of pipeline inspections (surveys) and a more frequent and comprehensive monitoring of various threats to the pipeline integrity. In particular, third party interference has to be better avoided, especially in South Africa. The study has next addressed the added value, feasibility, viability and sustainability of novel services based on integration of multiple space assets into PIMS activities. For example satellite images (SAR, hyperspectral, optical) can be used to detect large industrial vehicles or areas where landslides occur or subsidence takes place. In remote areas the pipeline could be equipped with sensor networks that transmit in-situ measurements via satellite communication to a central data processing facility, where the data is then checked for signs of corrosion and other anomalies. Finally satellite navigation can improve the georeferencing of pipelines and the measurements, overcoming the drawbacks in using traditional station coordinates or paper drawings of the pipeline. The study has so far resulted in a PIMS service design that integrates the PIMS PIMOA software suit with a multi-source and wide area network of sensors. The sensor suite comprises EO imagery instruments (optical & radar) for observing the surrounding conditions of the pipeline, in-situ sensors measuring basic pipeline data, and a communication network to transmit all data into a centralised database for further analysis and processing. The development of a pre-operational service together with the involved users is foreseen as a next step."
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010
The second Young Engineers' Satellite,YES2, is the longest manmade structure launched in 2007 and... more The second Young Engineers' Satellite,YES2, is the longest manmade structure launched in 2007 and is space piggybacked on the Foton-M3 microgravity platform with the objective of a controlled deployment of a 32km tether. This paper introduces the object and the flight results of YES2 and the performance of the satellite is studied in comparison of the simulations and ground tests with respect to the flight results.
55th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, 2004
Several future applications for space tethers such as tethered artificial gravity, space hooks an... more Several future applications for space tethers such as tethered artificial gravity, space hooks and the space elevator, feature high-tension tether deployment of fail-safe tethers. This paper presents the design of a deployer for high-tension flat space tethers that should further strengthen the case for future high-tension space tether applications. The presented tether deployer features two sets of linearly activated pinching plates, which are elastically hinged on cross-flexures. The elastically deforming design avoids the use of bearings and gearboxes. The fixation of the (flat) tether between flat pinching plates avoids bending of the tether, which occurs in a design using friction wheels. The bending of the tether around a friction wheel lowers the allowable tension in the tether, which is avoided in the presented design. The use of elastic hinges in space is growing, but usually the forces that occur are quite small. In the case of the presented tether deployer, the forces are extremely large, which is possible because the width of the tether is about one meter. The plate flexures are as wide as the tether, allowing very large forces. The width of the plate flexures also makes the mechanism very rigid, which is important when the force in the tether is large. The tether deployer design presented in this paper is performed for the case of MARS-g, a low Earth orbit artificial gravity test facility. The tension in the tether can be as high as 400 kN while the resulting tether deployer mechanism weighs only about 500 kilogram for low speed deployment. The design can be adapted for high speed deployment simply by adding a more powerful motor; the tension in the tether will remain the same, only more power is required. The design is therefore easily adaptable for other uses such as space hooks or the space elevator.
Vector-borne diseases such as Malaria, Chikungunya, Dengue and West Nile are a persistent public ... more Vector-borne diseases such as Malaria, Chikungunya, Dengue and West Nile are a persistent public health concern. International trade and travel. as well as changing environmental conditions favours colonisation of new areas by foreign (especially arthropod) species. Some of these species transmit diseases to human, and so their spread represents a significant health risk which needs to be quantified and mapped to facilitate strategic preparedness. VECMAP is a project of the European Space Agency's Integrated Application Promotion program (IAP). Based on needs expressed by national public health agencies and regional mosquito controllers a consortium led by Avia-GIS is developing a service for predicting potential mosquito-related health risks (early warning) and for reducing nuisance (targeted control effort). VECMAP enhances and simplifies traditional mathematical distribution modelling, field and laboratory work with the help of Satellite Navigation and Earth Observation.). Th...
Two new spacecraft attitude determination algorithms, Douma and DUDE (Delta-Utec Douma Extension)... more Two new spacecraft attitude determination algorithms, Douma and DUDE (Delta-Utec Douma Extension), have been developed for star pattern recognition from CCD camera data without a priori knowledge. They combine low memory requirements in the range from 50 to 500 kB and an extremely fast search strategy, independent of the size of the database. It supports a reliability >99.99 and accuracy of 1 arcsec level. This makes the algorithms especially interesting for compact real-time autonomous star sensor units. Goal of the study is to gain the necessary basis to develop a low cost autonomous star sensor for small satellites. The Douma algorithm combines the advantages of the existing Liebe and Quine algorithms. Liebe searches a database of all star triangles that could possibly be observed as being the closest one. Quine includes only the brightest triangles around target stars. Douma searches a list of the triangles that are the 'most likely' ones to be observed by the camera ...
54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, 2003
This paper reports on the testing of a novel tool for batch processing of star sensor imagery and... more This paper reports on the testing of a novel tool for batch processing of star sensor imagery and camera performance and design assessment. Star sensors based on pattern recognition provide the most accurate attitude solution available for spacecraft, even when using large field of view cameras. Due to advances in CCD, CMOS, integrated circuit technologies, and robust algorithms, star sensors are becoming more and more a viable alternative to solutions that were traditionally cheaper. A great many star sensor hardware is thus currently under development worldwide. This trend creates a market for generic design support software, automated batch processing of imagery resulting from real-sky tests and automated camera performance assessment. For this purpose, the Attitude Determination Test Environment (ADTE) tool was developed. The major novelty of the ADTE is that it contains a generic interface to batch process real-sky test imagery that provides as output the average directional accuracy of the camera, lens deviation correction estimates and performance distributions as a function of star magnitude or star class. No sophisticated test setup or idealized mathematical performance analysis is necessary. The tool includes camera simulation settings and up-to-date detection/rejection, centroiding and pattern recognition algorithms including upgraded versions of Liebe, Quine and Delta-Utec Douma Extension (DUDE). Pattern data storage and retrieval is based on the very fast multidimensional pointer-based array algorithms. Various recursive validation techniques maximize the number of recognized stars per image. The ADTE tool was first used for the real-sky test of the MEFIST-II camera in the Negev desert. This paper shortly explains the functionality of the tool and algorithms behind it and focuses on the analyses and results performed for MEFIST-II.
AIAA Atmospheric Flight Mechanics Conference and Exhibit, 2008
... and Michiel Kruijff Delta Utec Space Research and Consultancy, Leiden, 2312TT, The Netherlan... more ... and Michiel Kruijff Delta Utec Space Research and Consultancy, Leiden, 2312TT, The Netherlands Delft University of Technology, Delft, 2629HS, The Netherlands This paper highlights the plasma chamber testing of an innovative lightweight heatshield. ...
The 2nd Young Engineers Satellite (YES2) is a 36 kg student-built experiment that piggybacked on ... more The 2nd Young Engineers Satellite (YES2) is a 36 kg student-built experiment that piggybacked on the Foton-M3 microgravity platform in September 2007. Its mission was tethered SpaceMail: a propellantless sample return from an orbital platform. The experiment included a two-stage tether deployment, leading to a swing of the tether towards the local vertical, where finally a capsule was released from the bottom of the tethered system into a re-entry trajectory. The first deployment stage of 3.4 km was completed within
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A safe tether and deployer system has therefore been designed and verified with the help of simulation and innovative ground testing equipment. Through a hands-on educational approach, the YES and YES2 low-cost space tether experiments have been launched into orbit. In September 2007, all 32 km of the YES2 tether are deployed in orbit. With the help of this tether, a student-built re-entry capsule is deorbited over Kazakhstan.
This work reports this design and analysis effort, with the aim to raise confidence in the use of space tethers.
Goal of this work is to show the feasibility of achieving a high landing site accuracy making the tethered re-entry a serious candidate for a frequent sample return system for the International Space Station.
In order to optimize the landing site accuracy, a strategy was developed, called StarTrack: Swinging Tether Assisted Re-entry Through Robust Actively Controlled Kinetics.
The StarTrack philosophy includes the concept of an end-to-end simulator. It respectively simulates:
• the separation of the re-entry capsule;
• the tether deployment, swing and cut;
• the atmospheric entry and landing on the Earth's surface.
Four tools were developed and found to be of major importance for reaching an accurate landing site:
• A two stage deployment including a deployment break to recover from the major source of dispersion during the first km of deployment. A first stage length of 1500 m was found to give good results.
• The Energy Feedback during the deployment to a large angle.
Paths towards a large angle were found that were suitable for the robust Starfrack strategy. Even for large disturbances the Energy Feedback showed excellent performance. Only length and length rate measurements are needed.
• The Flex End Brake (FEB), avoiding longitudinal tether oscillations. This braking method is very successful in avoiding residual oscillations in a tether at the end of deployment. At most a 4 meter amplitude for a 35 km tether was observed. It is
very fast, there is no loss in Delta-V due to the FEB. No tether slackness is induced.
• A cutting time minimizing the influence of the disturbances.
Different optimal cutting times exist for the two cases, with and without GPS. With GPS the optimal cutting time can be updated during the swing. For the case without GPS the cutting time is determined by a focussing effect of the disturbances influences. This focussing effect was found thanks to the StarTrack end-to-end philosophy.
Papers by Michiel Kruijff
A safe tether and deployer system has therefore been designed and verified with the help of simulation and innovative ground testing equipment. Through a hands-on educational approach, the YES and YES2 low-cost space tether experiments have been launched into orbit. In September 2007, all 32 km of the YES2 tether are deployed in orbit. With the help of this tether, a student-built re-entry capsule is deorbited over Kazakhstan.
This work reports this design and analysis effort, with the aim to raise confidence in the use of space tethers.
Goal of this work is to show the feasibility of achieving a high landing site accuracy making the tethered re-entry a serious candidate for a frequent sample return system for the International Space Station.
In order to optimize the landing site accuracy, a strategy was developed, called StarTrack: Swinging Tether Assisted Re-entry Through Robust Actively Controlled Kinetics.
The StarTrack philosophy includes the concept of an end-to-end simulator. It respectively simulates:
• the separation of the re-entry capsule;
• the tether deployment, swing and cut;
• the atmospheric entry and landing on the Earth's surface.
Four tools were developed and found to be of major importance for reaching an accurate landing site:
• A two stage deployment including a deployment break to recover from the major source of dispersion during the first km of deployment. A first stage length of 1500 m was found to give good results.
• The Energy Feedback during the deployment to a large angle.
Paths towards a large angle were found that were suitable for the robust Starfrack strategy. Even for large disturbances the Energy Feedback showed excellent performance. Only length and length rate measurements are needed.
• The Flex End Brake (FEB), avoiding longitudinal tether oscillations. This braking method is very successful in avoiding residual oscillations in a tether at the end of deployment. At most a 4 meter amplitude for a 35 km tether was observed. It is
very fast, there is no loss in Delta-V due to the FEB. No tether slackness is induced.
• A cutting time minimizing the influence of the disturbances.
Different optimal cutting times exist for the two cases, with and without GPS. With GPS the optimal cutting time can be updated during the swing. For the case without GPS the cutting time is determined by a focussing effect of the disturbances influences. This focussing effect was found thanks to the StarTrack end-to-end philosophy.