scholarly journals Low-cost precursor of an interstellar mission

2020 ◽  
Vol 641 ◽  
pp. A45
Author(s):  
René Heller ◽  
Guillem Anglada-Escudé ◽  
Michael Hippke ◽  
Pierre Kervella
Keyword(s):  
Hollow Sphere ◽  
Interplanetary Space ◽  
Low Cost ◽  
Small Mass ◽  
The Sun ◽  
Cross Section Area ◽  
Section Area ◽  
Infrared Signature ◽  
Interplanetary Mission ◽  
Escape Speed

The solar photon pressure provides a viable source of thrust for spacecraft in the solar system. Theoretically it could also enable interstellar missions, but an extremely small mass per cross section area is required to overcome the solar gravity. We identify aerographite, a synthetic carbon-based foam with a density of 0.18 kg m−3 (15 000 times more lightweight than aluminum) as a versatile material for highly efficient propulsion with sunlight. A hollow aerographite sphere with a shell thickness ϵshl  =  1 mm could go interstellar upon submission to solar radiation in interplanetary space. Upon launch at 1 AU from the Sun, an aerographite shell with ϵshl  =  0.5 mm arrives at the orbit of Mars in 60 d and at Pluto’s orbit in 4.3 yr. Release of an aerographite hollow sphere, whose shell is 1 μm thick, at 0.04 AU (the closest approach of the Parker Solar Probe) results in an escape speed of nearly 6900 km s−1 and 185 yr of travel to the distance of our nearest star, Proxima Centauri. The infrared signature of a meter-sized aerographite sail could be observed with JWST up to 2 AU from the Sun, beyond the orbit of Mars. An aerographite hollow sphere, whose shell is 100 μm thick, of 1 m (5 m) radius weighs 230 mg (5.7 g) and has a 2.2 g (55 g) mass margin to allow interstellar escape. The payload margin is ten times the mass of the spacecraft, whereas the payload on chemical interstellar rockets is typically a thousandth of the weight of the rocket. Using 1 g (10 g) of this margin (e.g., for miniature communication technology with Earth), it would reach the orbit of Pluto 4.7 yr (2.8 yr) after interplanetary launch at 1 AU. Simplistic communication would enable studies of the interplanetary medium and a search for the suspected Planet Nine, and would serve as a precursor mission to α Centauri. We estimate prototype developments costs of 1 million USD, a price of 1000 USD per sail, and a total of < 10 million USD including launch for a piggyback concept with an interplanetary mission.

Wire-Electric Gyroscope

2013 ◽  
Author(s):  
Vadym Avrutov
Keyword(s):  
Electric Current ◽  
Low Cost ◽  
Angular Rate ◽  
Good Choice ◽  
Angular Rate Sensor ◽  
Cross Section Area ◽  
Section Area ◽  
New Type ◽  
The Wire ◽  
Rate Sensor

The wire-electric gyroscope (WEG) is a new type of the angular rate sensor. The basic principle of the WEG is based on the hypothesis of invariance of the electric current speed for the same wire (coil). It is similar to the Sagnac effect for the speed of light. The method of angular rate determination is described. The voltage difference between two wire coils with different line coupling can be expressed in applied rotation (angular) rate and velocity of electric current. The scale factor depends on the magnitude of the current, number of the coil turns, the coil’s radius, the cross-section area of the wire and specific (unit) resistance of the wire. WEG can be produced cost-effectively and can be a good choice for low-cost applications.

Some General Considerations of the Heating of Satellites

1959 ◽  
Vol 81 (4) ◽  
pp. 308-314 ◽  
Author(s):  
Alfred J. Eggers ◽  
Thomas J. Wong ◽  
Robert E. Slye
Keyword(s):  
Interplanetary Space ◽  
Astronomical Unit ◽  
The Sun ◽  
Small Particles ◽  
Radiation Heat ◽  
Heating Rates ◽  
Earth’S Atmosphere ◽  
Auxiliary Power ◽  
Earth's Atmosphere ◽  
Escape Speed

Heating of satellites is treated in connection with flight in planetary atmospheres and in interplanetary space. Heating during entry into the earth’s atmosphere is generally more severe than that encountered during launch or exit, although it can be substantially reduced by employing blunt shapes and small entry angles. Decelerations and heating rates during entry can be further reduced by employing lifting satellites. These techniques in combination with known radiation, heat-sink, and ablation cooling techniques appear adequate to handle the entry problem at speeds up to escape speed. Return flights from distant planets like Saturn and beyond may be characterized by much higher entry speeds, and more advanced techniques for coping with the heating problem may be required. Heating during entry into the atmospheres of planets neighboring Earth tends to be more or less severe than that in the earth’s atmosphere depending on whether the planets are larger or smaller than Earth. Heating in interplanetary space due to solar radiation becomes severe only if a satellite approaches to within a small fraction of an astronomical unit of the sun, or if the vehicle has an inefficient radiation shield. A cooling problem is encountered in the outer portion of our solar system, and an auxiliary power source may be required to supplement the reduced amount of heat from the sun. The sputtering or erosion of material from the surface of a satellite, caused by impact at hypervelocities with small particles in space, may also pose direct or indirect heating problems. Further research is required to assess the magnitude of these problems.

scholarly journals Muscle spindles of the rat sternomastoid muscle

2018 ◽  
Vol 28 (4) ◽  
Author(s):  
Walter Giuriati ◽  
Barbara Ravara ◽  
Andrea Porzionato ◽  
Giovanna Albertin ◽  
Carla Stecco ◽  
...  
Keyword(s):  
Cross Section ◽  
Muscle Tissue ◽  
Low Cost ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Fiber Types ◽  
Positive Type ◽  
Cross Section Area ◽  
Partial Data ◽  
Section Area

The sternomastoid (SM) muscle in rodents presents a peculiar distribution of fiber types with a steep gradient from the ventral, superficial, white portion to the dorsal, deep, red region, where muscle spindles are restricted. Cross section of the medial longitudinal third of the rat SM contains around 10,000 muscle fibers with a mean diameter of 51.28±12.62 (μm +/- SD). Transverse sections stained by Succinate Dehydrogenase (SDH) reaction clearly presents two distinct regions: the dorsal deep red portion encompassing a 40% cross section area contains a high percentage of packed SDH-positive muscle fibers, and the ventral superficial region which contains mainly SDH-negative muscle fibers. Indeed, the ventral superficial region of the rat SM muscle contains mainly fast 2B muscle fibers. These acidic ATPase pH 4.3-negative and SDH-negative 2B muscle fibers are the largest of the SM muscle, while the acidic ATPase pH 4.3-positive and SDH-positive Type 1 muscle fibers are the smallest. Here we show that in thin transverse cryosections only 2 or 3 muscle spindle are observed in the central part of the dorsal deep red portion of the SM muscle. Azan Mallory stained sections allow at the same time to count the spindles and to evaluate aging fibrosis of the skeletal muscle tissue. Though restricted in the muscle red region, SM spindles are embedded in perimysium, whose changes may influence their reflex activity. Our findings confirm that any comparisons of changes in number and percentage of muscle spindles and muscle fibers of the rat SM muscle will require morphometry of the whole muscle cross-section. Muscle biopsies of SM muscle from large mammals will only provide partial data on the size of the different types of muscle fibers biased by sampling. Nonetheless, histology of muscle tissue continue to provide practical and low-cost quantitative data to follow-up translational studies in rodents and beyond.

Solar Filaments as Tracers of Subsurface Processes

2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Intermediate Stage ◽  
Coronal Plasma ◽  
Magnetic Helicity ◽  
The Sun ◽  
New Paradigm ◽  
Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

EFFECT OF BEDLOAD SEDIMENT NATURAL COMPOSITION ON GEOMETRIC AND DINAMIC CHARACTERISTICS OF CHANNEL FORMS

2018 ◽  
pp. 36-39
Author(s):  
N Ikramov ◽  
T Majidov
Keyword(s):  
Research Work ◽  
Laboratory Data ◽  
Hydroelectric Station ◽  
Negative Consequences ◽  
Movement Velocity ◽  
Reservoir Volume ◽  
Pump Station ◽  
Cross Section Area ◽  
Section Area ◽  
Bedload Sediment

The article brings up data on sediment diversity at watercourse bed and on their movement in the form of ridges. The ridge form movement of sediment leads to the reduction of reservoir volume and canal cross section area, which has an effect on their carrying capacity, filling of pump station forechambers and hydroelectric station pressure basins with sediment. The presence of sediment in flow leads to abrasive deterioration of pumps, water motors and pressure pipes and to other negative consequences. Research work tasks on the study of these effects have been examined with the purpose of preventing such negative consequences. On the basis of laboratory data diagrams and relationships were obtained for ridge length, height and movement velocity vs. sediment hydraulic and geometric sizes.

scholarly journals A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Kazuo Shiokawa ◽  
Katya Georgieva
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Solar Wind Plasma ◽  
The Sun ◽  
Scientific Program ◽  
Solar Cycles ◽  
Grand Minimum ◽  
The Earth ◽  
Earth Connection ◽  
Near Future

AbstractThe Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI.

scholarly journals Long-term evaluation of rootstock effects on cropping and tree parameters of selected sweet cherry cultivars

2020 ◽  
Vol 47 (No. 1) ◽  
pp. 13-20
Author(s):  
Jitka Blažková ◽  
František Paprštein ◽  
Lubor Zelený ◽  
Adéla Skřivanová ◽  
Pavol Suran
Keyword(s):  
Sweet Cherry ◽  
Cross Section Area ◽  
Section Area ◽  
Natural Tendency ◽  
Term Evaluation ◽  
The Mean ◽  
Sweet Cherry Cultivars ◽  
Tree Characteristics ◽  
Gisela 5

The cropping of six sweet cherry cultivars that originated in the Research and Breeding Institute of Pomology at Holovousy, and a standard one, ‘Burlat’, were evaluated on three rootstocks in the period of 2007–2017. Trees planted in a spacing of 1.5 m × 5.0 m were trained as tall spindle axes utilising their natural tendency to develop a central leader. On the standard rootstock, P-TU-2, ‘Tim’ was the most productive with a mean total harvest of 47.6 kg per tree. ‘Sandra’ yielded the most on the PHLC rootstock with 56.2 kg per tree and ‘Helga’ yielded the most on Gisela 5 with a mean total harvest of 55.9 kg per tree. The mean impact of the rootstock on the tree vigour, measured upon the trunk cross section area, ranged from 148.4 cm2 on the standard rootstock P-TU-2 to 114.1 cm2 on the PHLC and 125.2 cm2 on Gisela 5 . On the standard rootstock P-TU-2, the most vigorous one according to this criterion was ‘Jacinta’ (178.0 cm2) whereas ‘Justyna’ (109.7 cm2) was the least vigorous. On the PHLC, the most vigorous was ‘Sandra’ (147.2 cm2) and the least was ‘Amid’ (94.0 cm2). The other tree characteristics were mainly dependant on the cultivar and minimally, or not at all, influenced by the rootstock vigour.

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