 |
||||||
|
Home Page / FAQ About 1000 Planets Current Projects Space Settlements Mars Colony Space/1KP News Marketplace Help/Join Us Academia Just for Fun Communicate Open Forum Open Chat Suggestion Box 1KP SETI Team |
1000 Planets ORSON OMV An analogy for an OMV is a taxi taking passengers and cargo from an airport to their destination. For an OMV the airport is the orbit where the payload has been initially placed by the launch vehicle and the destination can be LEO, GEO, a space station or platform etc. An OMV is a more economical, efficient, flexible and cheaper method of transportation in Earth orbit compared to launch vehicles or independent propulsion (equipping satellites to function like an OMV i.e. movement from LEO to GEO). A standard method of calculating the benefits of an OMV is comparing the financial cost of OMV transport with conventional transport (satellite rocket boosters) methods. Furthermore, the reduction in transportation costs results in market expansion and company market share. It should also be noted that transport from LEO to GEO is only one such transportation service an OMV can offer. An OMV may provide services such as satellite constellation maintenance etc. as well as refueling, maintenance and upgrading of space assets. These services may be launched (no pun intended) at a later date be creating a modular OMV architecture and simply adding components/modules. ORSON CHARACTERISTICS: The major sections of an OMV (are in order of decreasing complexity): Command control and communications are the "brains" of the OMV. At best we will be able to directly control Orson for only a few minutes, intermittently depending on Orsonís present orbit, heading etc. A ring of microsatellites (3-4) in GEO could provide the ěcompleteî coverage required for direct control however, such a system has not been constructed nor designed and by definition would be costly. Moreover, some technical hurdles remain i.e. one can use a ěmotileî antennae for a directed comm. beam or simply ědrenchî orbit with comm. signals either way problems stand i.e. power requirements, reliability, legal etc. An autonomous ability may be provided by a combination of tradition/"top-down" and modern/îbottom-upî A.I. program/agent. For example a neural network can be utilized to ěflyî Orson from one point to another. Obviously, safeguards and monitoring must be in place but this is required for all space activities regardless of method indeed, A.I. techniques can drastically reduce risk compared to conventional methods. A.I techniques are increasingly being considered for command and control. DS1 and other New Millennium spacecraft will rely on A.I to succeed in their missions, i.e. DS1ís Remote Agent software, to determine, diagnose, notify and ěrepairî any problems i.e. malfunctioning thrusters etc. that may occur independently of ground control in addition to guidance. NASA hopes to use a neural network for docking to the ISS. It can be seen that an autonomous system will be required in both the OMV and Mission Control (M.C.) and an autonomous system such as Remote Agent should be implemented. An off the shelf RTOS (Real-time Operating System) such as VxWorks can be used as the underlying system layer, this RTOS has been used with great success on the Pathfinder mission, ISS and Space Shuttle. VxWorks is able to run on a variety of platforms including Power PC and Intel based architectures. Power PC is a RISC-type architecture. A RISC (Reduced Instruction Set Computer) has the advantage of running at lower clock speeds, requiring less power, and thus requiring being cooler, and being smaller than while being as or more powerful then Intel Architecture. The only disadvantage of RISC is the greater relative complexity of the software required to run under it. However, software development does not pose a problem though in some ways it may be more complex. Therefore, it is suggested that a RISC based computer be utilized. An alternative computer system could utilize redundant LRH-3000Vflight systems; these space-qualified systems relatively large, with a published weight of 20kg. Electronics should utilize low voltage components and thus, would have low power requirements and generate less waste heat. Computers and electronics have to be radiation hardened (a radiation hardened PowerPC derivative exists) and thus, will literally be custom built (Sojourners 2Mhz processor took IBM a month to produce and deliver; radiation hardened components are typically made on demand). The command software is able to control the main engines and also the various maneuvering thrusters that are needed so that the OMV can pilot through space. The command software will be more complex than a satellite or an OTV due to its increased mission diversity and flexibility. The networking of the modules requires the use of an advanced network structure able to deal with great noise and error propagation i.e. due to radiation. On the ground a simple program can be used to ědrag and dropî the appropriate commands into the ěControl Stack.î Fail safes and warnings can be used in case the ěControl Stackî has commands which may cause Orson to fail. By including a layer of abstraction people with minimal programming skills are able to operate Orson. Other programming languages could be used to create this system, Ada for example. A ring-laser gyro inertial navigation system can be utilized to determine the ěaltitude,î position, speed and heading of Orson. Simple computer programs implemented in flash re-programmable read-only-memory can utilize the data from the inertial navigation system to determine the distance from min. altitude, min. velocity (to maintain orbit) etc. These data can be used in a simple program to maintain Orson in orbit: the program will utilize the minimum acceptable values (i.e. minimum speed to maintain a particular orbit) to override/prevent certain actions/reactions from taking place. This software will also be used to provide ěstation-keepingî commands for Orson to maintain a particular ěaltitude,î speed, heading etc. In addition, an emergency rocket i.e. solid fuel, mounted on the skeleton, may be triggered automatically by the software when the radar altimeter etc. indicate a too low altitude or speed (i.e. danger of re-entry) i.e. a kind of reflex arc. An alternative or back-up for the ring-laser gyro is a star tracker. Star trackers have dropped in price in recent years A radar used in conjunction with an A.I can provide collision avoidance and close-in "docking" back-up. At any time Orson may be directly controlled. A software program from Microcosm Inc. can maintain and predict the orbit of any satellite. An evaluation paper extract: "Microcosm, under Air Force Research Laboratory (Space Vehicles Directorate) and internal funding, developed and flew the first fully autonomous, on-board orbit determination and in-track and cross-track control system. Results show the technology maintaining in-track position to ± 1 km indefinitely while using less propellant than traditional orbit maintenance. Implementing autonomous orbit control significantly reduces operations costs, eliminates many of the traditional payload planning cycles, and creates added system robustness. In addition, this technology provides a capability never previously available: specifying a satelliteís position months, if not years, in advance with great ease and accuracy with simple geometric calculations rather than complex orbital mechanics and propagation. This will allow all system components (ground based and on-orbit) to know factors such as the current location of all satellites in the system, location and direction to the nearest satellite, parameters of current or future ground passes, when satellite transitions occur, and when a given satellite will next be over any location for all future times. This paper provides results of the flight demonstration and discusses the cost reduction associated with implementing this technology." The advantages are obvious: we can utilize this program in conjunction with the ring-laser gyro navigation system as the primary navigation and command software. One copy of the Microcosm Inc. orbit prediction software is utilized by the modified Remote Agent software to predict the orbits of all orbiting satellites etc. When a satellite is placed in Earth orbit, data given by the company and by simple monitoring are utilized to enter the satellites position into the computer simulation. Once an orbit has been predicted the Remote Agent-type software is utilized to optimize an approach to the payload and to determine the necessary commands. These commands are transmitted to the OMV, which transits to the vicinity utilizing its ring-laser gyro nav. system. While nearing the commanded location, within +/- 1km, the OMV's own basic ESM-type sensor (add one back-up) "picks up" the payloads pulsed radio beacon containing its ID (i.e. satellite reg. Number, type etc.) which it utilizes to positively identity and near the payload. Once in range the OMV's additional sensors can be utilized to perform close in and automated "docking." These close-in/docking sensors (require at least two sensors and two others for back-up) can be two Marshall Space Flight Center Video Guidance Sensors (VGS), these sensors are heavy (20kg) and require significant power but are space qualified and a prove heritage. One VGS camera looks forward the other aft, both cameras are recessed as much as possible. Four Sandia National Labs scanner-less range imagers provide secondary back-up, two cameras on each side in a similar configuration. Utilizing two sets of sensors provides full redundancy. The approach, close-in and "docking" are all automated and stored in flash re-programmable memory. Once "docking" is complete Orson proceeds to the location of payload release by utilizing a second set of commands transmitted to it (part of the original commands but to be "run" when "docking" was completed). A Remote Agent-type program on-board the OMV will interpret the commands received and cope with unforeseen difficulties if necessary Mission Control can assume direct control. If the M.C. Computer commands an action that may lower Orsonís altitude and/or speed or in any other way endanger it, Orson will respond by requesting confirmation and authorization i.e. password. Passwords etc. will be local, only affecting a particular action and others for a type of action, in addition to a Master Password to override any and/or all safety features. These features are part of the "station-keeping" program. This program is a modified version of the satellite version of the Microcosm Inc. program. These features may seem excessive but are entirely doable and desirable. Such an Orson command and control system will drastically reduce risk of Orson loss with or without payload and thereby reducing insurance costs, risks and increasing investor and customer confidence etc. In fact, the risk of Orson failure would be lower than a conventional booster or OMV with such a command system. One need only remember the recent Ariane 5 failure and the disastrous Progress re-supply mission to Mir where an inattentive Progress operator/îpilotî ploughed through Mir itself. Not nice at all. Two commercially available TDRSS transponders and three commercially available UHF transponders from Motorola can provide communications. The UHF transponders have built-in encryption technology which satisfy a NASA requirement. The TDRSS transponders lack this encryption capability. The three UHF transponders would make the comm. system doubly redundant. This capability is advantageous to prevent a loss of communications during approach, close-in and "docking" and allows the OMV to function with the ISS (the comm. requirements are satisfied). (B) PROPULSION Purchasing an ion-engine of the necessary power for main propulsion is improbable, the DS1 ion-engine is the largest ion-engine flight tested and it would not be adequate for Orson. Therefore, to provide the required main thrust it will require the use of numerous "off-the-shelf" satellite ion thrusters (the largest thrusters). Satellite ion thrusters i.e. Hall thrusters may be used for maneuvering but would need to be multiplied. The advantage of using a large number of such "off-the-shelf" thrusters include: (C) POWER Multiple parallel power circuits offer a system that can survive the loss of one circuit (at least two circuits will be required for power). One power circuit for low power i.e. electronics, the other circuit for high power i.e. ion engines; with simple mechanical receptacles for attaching lines and components, i.e. power, comm. plugs etc, to virtually any location on Orsonís truss skeleton. All hardware, even the power and comm. lines will be modular attaching to the truss this will enable easy repair, expansion and modification. The communication system may be made of fiber optic cabling (provide the materials utilized are radiation resistant i.e. glass) as a conventional communication system may be interfered by the Van Allen belts. The SCARLETT array would be an ideal solar array requiring an area of only ~ 61-62m squared to power a 300Kw Orson. Although the SCARLETT array has a degree of radiation protection, it will be necessary to provide additional protection: this can be obtained by the use of a glass PV cover, a removable covering i.e. shape memory-alloy (SMA), reinforced cloth and solar cell annealing by heating the PV panels to 400k. A commercial company is marketing a T-shirt, with embedded shape memory-alloy fibers, for 2000 pounds that automatically rolls up when a personís body temp. increases and lowers when the temp. decreases. Therefore, it is possible to develop a covering that may cover/uncover the PV panels on demand. A communication antenna may also be formed by a SMA mesh and could in fact be ěself-reparableî to a degree. Note: shape memory-alloys have been space qualified and are being marketed for such purposes. Rechargeable batteries may be nickel-cadmium or nickel-hydrogen. (D) THERMAL MANAGEMENT Protection against the thermal space environment is provided by multi-layer insulation covering the vehicle. External radiative coatings (aluminised secondary surface mirror coating or absorptive black paint) are optimized locally. Passive radiators and active heaters are also used where necessary, in particular during the attached phase. A thermophotovoltaic system can be utilized to recover some of the waste heat, producing additional electricity. A shade may be utilized to further lower the temperature i.e. to cryogenic temperatures. This shade may be covered with solar cells and may be in the form of a shape memory-alloy (SMA), solar cell cloth. (E) DOCKING AND REFUELING STRUCTURES A simple method of docking is preferred, coupled with a means of information transfer. A multiple prong structure, similar to electrical cord prongs, mounted upon one or more ends of Orson i.e. one on each side will allow modules to be added to the OMV. Orson would simply "plug" into an electrical outlet-type structure found upon the payload or another OMV. This outlet-type structure may similarly be present on one or more ends. Data and power could also be transmitted through the prongs and outlets. The advantage of passive structures, i.e. prongs and outlets, are their great simplicity and reliability. Refueling can be accomplished by a system similar to the "probe and drogue" aircraft system. An OMV would "fly" (at >1m/s) it's needle-like probe mounted upon the OMV "nose" into a drogue. The drogue is a funnel-like structure (~1m in diameter) with an automatic coupling mounted upon a semi-flexible hose (impregnated with shape memory-alloy strands to give it some rigidity) mounted upon a fuel tank module. The fuel tank module would contain an inert gas (i.e. nitrogen, helium) bladder, which would pressurize the liquid fuel. Upon automatic coupling of the probe and drogue the pressurized fuel would flow from the fuel tank to the OMV. A sensor in the OMV would signal a "full fuel tank" causing the OMV to detach from the drogue by decreasing the OMV velocity. To refuel the fuel tanks a tanker OMV would attach to the drogue like normal however, its fuel would be under greater pressure (caused by an inert gas bladder with a greater amount of gas) and thus, the fuel would enter and re-pressurize the fuel tank. IN appearance the drogue and fuel tank would resemble a curved road light; the refueling process would resemble that of hummingbird and a flower. Each fuel tank can have several drogues arcing upwards (due to low-g). To provide guidance to the OMV, the drogue funnel would have a low powered radio beacon; numerous lights, beacons etc. would be mounted upon the fuel tank and hose functioning as warning lights, beacons etc. Electricity would be provided by a small solar power system mounted upon the fuel tanks which would inturn be mounted upon a "space tower" in GEO this modular tower would function as a comm. relay to the OMVs etc. When a fuel tank becomes empty a sensor triggers an automated radio signal which triggers the "space tower" to send an signal to M.C. to send a fuel tanker. This fuel tank signal replaces that of the normal drogue funnel signal and thus prevents an OMV from docking and refueling (it does not "see" the funnel of the drogue) however, the tanker can only "see" this signal and will dock to the signal-emitting drogue funnel and thus, refuel the fuel tank. (F) MODULAR STRUCTURE A modular structure can be created by assembling individual modular components upon a modular ěskeletonî via technology analogous to ěplug and playî PC tech. combined with household/commercial electrical systems. A ěskeletonî comprised of an expandable truss segment, i.e. an ISS truss (made of titanium-alloy), with parallel communication and power circuits. The modules themselves will be made of two layers of carbon fiber composites ěsandwichingî a layer of insulation (i.e. modified ET tank etc.) The modules are then to be wrapped I several layers of carbon fiber/Kevlar/ceramic cloth to provide added protection; a titanium-alloy framework can be used for added strength and as a mounting ěcage.î The electronics modules will have to have an additional layer for radiation protection: three carbon composite layers with the first gap enclosing a dense metal i.e. lead-alloy the second gap containing the insulation as stated above. Careful attention must be paid to the use of materials that can be utilized in the space environment i.e. extreme temperatures, high radiation exposure, elemental oxygen in LEO etc. Some materials stated above may prove to be not acceptable i.e. titanium-alloy may need to substitute for carbon composites, coatings may be required, though Kevlar and ceramic cloth may be used in space. Microcosm Inc. in 2000 designed an OTV (Orbital Transfer Vehicle: a simpler less robust version of an OMV) which would have utilized a monocoque shell made of IM7/PEEK (a type of composite) and support structures made of aluminum. Making the shell with Kevlar (1.35mm thick) would satisfy LEO transportation structural requirements and possibly the micrometeoroid safety requirements. A shell of 1.875mm of Kevlar would give "substantial impact protection while maintaining nearly the same mass as an IM7/PEEK composite." High Efficiency: Structural, thermal and electrical structures may be combined. As few moving parts as possible (preferably none) should be utilized to increase reliability. Orson should be of appropriate mass for a given payload mass. It would not make much sense to have a 20 ton vehicle and a 1 ton payload. Click here to go back to the Projects.
Copyright © 2005 - 1000 Planets Inc.
Ethics & Privacy Policies Comments - Questions - Suggestions |