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March 26, 2012

Carnival of Space 242

The Carnival of space 242 is up at DearAstronomer. Universe Today - Nearly ten years ago, astronomers were stunned to discover a star that had been apparently flung from its own system and travelling at over a million kilometers per hour. Over the years, a question was brought up: If stars can be ejected at a high velocity, what about planets?
The mechanics responsible for the super-fast planets are similar to those responsible for “hypervelocity” stars. With stars, if a binary system drifts too closely to a supermassive black hole (such as the ones in the center of galaxies), the gravitational forces can separate the stars – sending one outward at incredible speeds, and the other in orbit around the black hole. Interestingly enough, “Warp Speed” planets can theoretically travel at a few percent of the speed of light. The team, which includes Loeb and Ginsburg, created computer models to simulate the outcome if each star had planets orbiting it. The outcome of the model showed that the star shot into interstellar space would keep its planets, but the star “captured” into orbit around the black hole would have its planets stripped and sent outward at incredible speeds. Typical speeds for the planets range from 11-16 million kilometers per hour, but given the proper conditions could approach even higher velocities.
Centauri Dreams - the work of Forward, Norem, Matloff and Johnson on thrustless turning reminds us that interactions with the medium itself may become a component of starship design, just as the magnetic sail idea — braking against a stellar wind — uses the ambient environment to do something that would otherwise demand onboard fuel. Nextbigfuture -Elon Musk has a plan for inexpensive trips to Mars. A fully reusable Spacex system would have roundtrip costs to Mars of half a million dollars. He conceded the figure was unlikely to be the opening price - rather, the cost of a ticket on a mature system that had been operating for about a decade. Nonetheless, Musk thought such an offering could be introduced in 10 years at best, and 15 at worst. Nextbigfuture - Consider a PowerSat launched by a Falcon 9 assuming a mass of 100g/m2, which at 45g/m2 for the collection area leaves 2.6tons for all other systems. This leads to a square PowerSat 210 meters on a side. Assuming 8% sunlight-to-grid-power efficiency (20% solar cell and 40% transmission efficiency) this system would deliver roughly 5.28MW to the grid. A recent DOD report suggests that the U.S. military is willing to pay $1/kwh for power beamed to forward bases in Asia. Trucks transporting diesel can be ambushed, IR power beams cannot, and football-field sized receivers could fit on the larger bases. A 5MW system at this price would provide up to $46 million per year revenue, enough to pay for the launch in a little over a year. For commercial customers, the highest price this author could find world wide was $0.29 per kwh for industrial users in Italy in 2008. This could deliver up to $13.4 million per year { requiring a little over three years to pay for the launch. Nextbigfuture - Elon Musk claims that, using fully reusable hardware, the cost of launching payloads to space could eventually go as low as $10 per pound. Other low-cost proposals for putting payloads into orbit have been covered by Nextbigfuture, including airships to orbit as well as laser propulsion and startram. Aerospace engineer Ajay Kothari of the Astrox corporation has spent the past decade thoroughly studying various concepts for reducing space costs. In an interview with Sander Olson for Next Big Future, Kothari argues that vertically launched scramjet vehicles may be the best way in the short run to inexpensively launch payloads into space. Kothari believes that scramjet or fully reusable rockets could eventually bring the cost to Low Earth Orbit down to $100 per pound. Nextbigfuture - A constellation of 12 or more mirror satellites is proposed in a polar sun synchronous orbit at an altitude of approximately 1000 km above the earth. Each mirror satellite contains a multitude of 2 axis tracking mirror segments that collectively direct a sun beam down at a target solar electric field site delivering a solar intensity to said terrestrial site equivalent to the normal daylight sun intensity extending the sunlight hours at said site by about 2 hours at dawn and 2 hours at dusk each day. Each mirror satellite in the constellation has a diameter of approximately 10 km and each terrestrial solar electric field site has a similar diameter and can produce approximately 5 GW per terrestrial site. Assuming that approximately 50 terrestrial solar electric field sites are evening distributed in sunny locations near cities around the world, this system can produce more affordable solar electric power during the day and further into the morning and evening hours. The typical operating hours for a terrestrial solar electric field site can thus be extended from approximately 8 hours per day by 50% to approximately 12 hours per day. Assuming a cost of electricity of 10 cents per kWh and a projected launch cost to orbit of $1500/kg for the SpaceX Falcon Heavy launch vehicle, the cost of this mirror constellation system should be recovered in approximately 2.7 years from the additional solar electricity sales



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