Electromagnetic Formation Flight NRO DI Final review Friday, August 29, 2003 National reconnaissance office Headquarters Chantilly, VA LOCKHEED MART Massachusetts Institute of Lockheed Martin Corporation Technology Advanced Technology Center Space Systems Laboratory
• Massachusetts Institute of Technology • Space Systems Laboratory • Lockheed Martin Corporation • Advanced Technology Center Electromagnetic Formation Flight Electromagnetic Formation Flight NRO DII Final Review Friday, August 29, 2003 National Reconnaissance Office Headquarters Chantilly, VA
大 Outline Motivation Fundamental principles MIT EMFFORCE Testbed Governing Equations Design Trajectory Mechanics Calibration Stability and Control Movie Mission Applicability Space Hardware Design Issues Sparse Arrays Thermal Control Filled Apertures Power System Design Other Proximity Operations High b-Field Effects Mission Analyses Conclusions Sparse Arrays Filled Apertures Other Proximity Operations DIl EMFF Final review ug.29,2003
DII EMFF Final Review Aug. 29, 2003 Outline Outline • Motivation • Fundamental Principles – Governing Equations – Trajectory Mechanics – Stability and Control • Mission Applicability – Sparse Arrays – Filled Apertures – Other Proximity Operations • Mission Analyses – Sparse Arrays – Filled Apertures – Other Proximity Operations • MIT EMFFORCE Testbed – Design – Calibration – Movie • Space Hardware Design Issues – Thermal Control – Power System Design – High B-Field Effects • Conclusions
大 Motivation Traditional propulsion uses propellant as a reaction mass Advantages ability to move center of mass of spacecraft (Momentum conserved when propellant is included) Independent (and complete) control of each spacecraft Disadvantages Propellant is a limited resource Momentum conservation requires that the necessary propellant mass increase exponentially with the velocity increment(AV) Propellant can be a contaminant to precision optics DIl EMFF Final review ug.29,2003
DII EMFF Final Review Aug. 29, 2003 Motivation Motivation • Traditional propulsion uses propellant as a reaction mass • Advantages – Ability to move center of mass of spacecraft (Momentum conserved when propellant is included) – Independent (and complete) control of each spacecraft • Disadvantages – Propellant is a limited resource – Momentum conservation requires that the necessary propellant mass increase exponentially with the velocity increment (∆V) – Propellant can be a contaminant to precision optics
大 Question Is there an alternative to using propellant? Single spacecraft Yes. If an external field exists to conserve momentum Otherwise. not that we know of Multiple spacecraft Yes, again if an external field exists OR, if each spacecraft produces a field that the others can react against Problem: Momentum conservation prohibits control of the motion of the center of mass of the cluster, since only internal forces are present DIl EMFF Final review ug.29,2003
DII EMFF Final Review Aug. 29, 2003 Question I: Question I: • Is there an alternative to using propellant? • Single spacecraft: – Yes, If an external field exists to conserve momentum – Otherwise, not that we know of… • Multiple spacecraft – Yes, again if an external field exists – OR, if each spacecraft produces a field that the others can react against – Problem: Momentum conservation prohibits control of the motion of the center of mass of the cluster, since only internal forces are present
大 Question / Are there missions where the absolute position of the center of mass of a cluster of spacecraft does not require control? Yes! In fact most of the ones we can think of Image construction u-v filling does not depend on absolute position Earth coverage As with single spacecraft, Gravity moves the mass center of the cluster as a whole, except for perturbations Disturbance(perturbation) rejection The effort to control perturbations affecting absolute cluster motion(such as J2) is much greater than that for relative motion Only disturbances affecting the relative positions(such as differential J2) NEED controlling to keep a cluster together Docking Docking is clearly a relative position enabled maneuver DIl EMFF Final review ug.29,2003
DII EMFF Final Review Aug. 29, 2003 Question II: Question II: • Are there missions where the absolute position of the center of mass of a cluster of spacecraft does not require control? • Yes! In fact most of the ones we can think of… – Image construction • u-v filling does not depend on absolute position – Earth coverage • As with single spacecraft, Gravity moves the mass center of the cluster as a whole, except for perturbations… – Disturbance (perturbation) rejection • The effort to control perturbations affecting absolute cluster motion (such as J2) is much greater than that for relative motion • Only disturbances affecting the relative positions (such as differential J2) NEED controlling to keep a cluster together – Docking • Docking is clearly a relative position enabled maneuver