Power optimal single-axis articulating strategies

Power optimal single axis articulating PV array motion for Space Station Freedom is investigated. The motivation is to eliminate one of the articular joints to reduce Station costs. Optimal (maximum power) Beta tracking is addressed for local vertical local horizontal (LVLH) and non-LVLH attitudes. Effects of intra-array shadowing are also presented. Maximum power availability while Beta tracking is compared to full sun tracking and optimal alpha tracking. The results are quantified in orbital and yearly minimum, maximum, and average values of power availability

SOYUZ escape trajectory analysis from Space Station Freedom

It has been proposed to utilize the Russian built SOYUZ as an assured crew return vehicle (ACRV) for Space Station Freedom. Three departure directions (nadir, zenith, minus velocity) are evaluated to determine escape path clearances. In addition, the effects of the following parameters were also evaluated: delta-V magnitude, configuration dependent ballistic coefficients, atmospheric density, Freedom attitude control, and canted docking adaptors. The primary factor influencing the escape trajectory was station contingency attitude rate. The nadir and zenith departures were preferable to minus velocity. The impact of atmospheric density and relative ballistic coefficients was minimal

Spacecraft attitude control momentum requirements analysis

The relationship between attitude and angular momentum control requirements is derived for a fixed attitude, Earth orbiting spacecraft with large area articulating appendages. Environmental effects such as gravity gradient, solar radiation pressure, and aerodynamic forces arising from a dynamic, rotating atmosphere are examined. It is shown that, in general, each environmental effect contributes to both cyclic and secular momentum requirements both within and perpendicular to the orbit plane. The gyroscopic contribution to the angular momentum control requirements resulting from a rotating, Earth oriented spacecraft is also discussed. Special conditions are described where one or more components of the angular momentum can be made to vanish, or become purely cyclical. Computer generated plots for a candidate space station configuration are presented to supplement the analytically derived results

Paper Session III-B - Utilization of Common Pressurized Modules of Space Station Freedom

Typical of past space projects following preliminary design review, most of the major Space Station critical subsystems will be required to reduce costs, weight, and power consumption prior to flight article hardware production. One such subsystem consists of the pressurized modules which provide the environment in which the crew members live and work. The current baseline station has two types of U.S. pressurized vessels: four resource nodes, and two modules 44 feet in length which must be transported to orbit nearly empty due to structural weight alone. Thus, user and system racks must be outfitted on-orbit rather than integrated on the ground. In this feasibility study, a shorter common pressurized module concept is assessed. The size, transportation, location, and accommodation of system racks and user experiments are considered and compared to baseline. It is shown that the total number of flights required for station assembly can be reduced, assuming both nominal Space Shuttle capacity, as well as Advanced Solid Rocket Motor capability. Baseline module requirements regarding crew size and rack accommodation are preserved. Considering the criteria listed above and current weight estimates, a six module option appears optimal. The resulting common module is 28 feet in length, and, in addition to two end cones, contains three radial ports near one end, which allows for a racetrack configuration pattern. This pattern exhibits several desirable attributes, including dual egress capability from any U.S. module, logical functional allocation distribution, no adverse impact to international partner accommodation, and favorable air lock, cupola, Assured Crew Return Vehicle, and logistics module accommodation

Utilization of common pressurized modules on the Space Station Freedom

During the preliminary design review of Space Station Freedom elements and subsystems, it was shown that reductions of cost, weight, and on-orbit integration and verification would be necessary in order to meet program constraints, particularly nominal Orbiter payload launch capability. At that time, the Baseline station consisted of four resource nodes and two 44 ft modules. In this study, the viability of a common module which maintains crew and payload accommodation is assessed. The size, transportation, and orientation of modules and the accommodation of system racks and user experiments are considered and compared to baseline. Based on available weight estimates, a module pattern consisting of six 28 ft. common elements with three radial and two end ports is shown to be nearly optimal. Advantageous characteristics include a reduction in assembly flights, dual egress from all elements, logical functional allocation, no adverse impacts to international partners, favorable airlock, cupola, ACRV (Assured Crew Return Vehicle), and logistics module accommodation, and desirable flight attitude and control characteristics

Restructured Freedom configuration characteristics

In Jan. 1991, the LaRc SSFO performed an assessment of the configuration characteristics of the proposed pre-integrated Space Station Freedom (SSF) concept. Of particular concern was the relationship of solar array operation and orientation with respect to spacecraft controllability. For the man-tended configuration (MTC), it was determined that torque equilibrium attitude (TEA) seeking Control Moment Gyroscope (CMG) control laws could not always maintain attitude. The control problems occurred when the solar arrays were tracking the sun to produce full power while flying in an arrow or gravity gradient flight mode. The large solar array articulations that sometimes result from having the functions of the alpha and beta joints reversed on MTC induced large product of inertia changes that can invalidate the control system gains during an orbit. Several modified sun tracking techniques were evaluated with respect to producing a controllable configuration requiring no modifications to the CMG control algorithms. Another assessment involved the permanently manned configuration (PMC) which has a third asymmetric PV unit on one side of the transverse boom. Recommendations include constraining alpha rotations for MTC in the arrow and gravity gradient flight modes and perhaps developing new non-TEA seeking control laws. Recommendations for PMC include raising the operational altitude and moving to a symmetric configuration as soon as possible

Space Station Freedom assembly and operation at a 51.6 degree inclination orbit

This study examines the implications of assembling and operating Space Station Freedom at a 51.6 degree inclination orbit utilizing an enhanced lift Space Shuttle. Freedom assembly is currently baselined at a 220 nautical mile high, 28.5 degree inclination orbit. Some of the reasons for increasing the orbital inclination are (1) increased ground coverage for Earth observations, (2) greater accessibility from Russian and other international launch sites, and (3) increased number of Assured Crew Return Vehicle (ACRV) landing sites. Previous studies have looked at assembling Freedom at a higher inclination using both medium and heavy lift expendable launch vehicles (such as Shuttle-C and Energia). The study assumes that the shuttle is used exclusively for delivering the station to orbit and that it can gain additional payload capability from design changes such as a lighter external tank that somewhat offsets the performance decrease that occurs when the shuttle is launched to a 51.6 degree inclination orbit

Агро- и микроклиматическая оценка условий формирования урожайности винограда

Проблема агроклиматического обеспечения аграрного сектора экономики остается важнейшей задачей агрометеорологов и направлена на оценку агроклиматических ресурсов территорий с целью оптимизации размещения сельскохозяйственных культур как условия повышения продуктивности и стабильности отрасли. Актуальность исследований в этом направлении обусловлена отсутствием информации о реально достижимой урожайности отдельных сельскохозяйственных культур как в региональном разрезе, так и на локальном уровне.Проблема агрокліматічеського забезпечення аграрного сектора економіки залишається найважливішою задачею агрометеорології і направлена на оцінку агрокліматічеськіх ресурсів територій з метою оптимізації розміщення сільськогосподарських культур як умови підвищення продуктивності і стабільності галузі. Актуальність досліджень в цьому напрямі обумовлена відсутністю інформації про реально досяжну врожайність окремих сільськогосподарських культур як в регіональному розрізі, так і на локальному рівні

Space Station Freedom contingency reboost and resupply strategies

The objective of this study was to determine the requirements necessary to ensure a viable Space Station Freedom (SSF) in the event of a delay in the date of the first element launch, and/or in the event that the nominal assembly sequence is interrupted, perhaps due to a delay in the Space Shuttle Launch Schedule. Orbit lifetimes, reboost fuel requirements, and controllability requirements were calculated for each stage of the SSF assuming anywhere from a 6 to 24 month delay/interruption in the baseline SSF assembly sequence. These results were assessed in order to formulate strategies to assure SSF viability in the presence of assembly sequence delays and interruptions

Orbiter utilization as an ACRV

Assuming that a Shuttle Orbiter could be qualified to serve long duration missions attached to Space Station Freedom in the capacity as an Assured Crew Return Vehicle (ACRV), a study was conducted to identify and examine candidate attach locations. Baseline, modified hardware, and new hardware design configurations were considered. Dual simultaneous Orbiter docking accommodation were required. Resulting flight characteristics analyzed included torque equilibrium attitude (TEA), microgravity environment, attitude controllability, and reboost fuel requirements. The baseline Station could not accommodate two Orbiters. Modified hardware configurations analyzed had large TEA's. The utilization of an oblique docking mechanism best accommodated an Orbiter as an ACRV