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January 03, 2009

Carnival of Space Week 85

Carnival of Space week 85 is up at Cheap Astronomy.

This site provided information on space elevator tether strength requirements and development status

Centauri Dreams looks at interstellar mission possibilities.

A longbet was made: the first true interstellar mission, targeted at the closest star to the Sun or even farther, will be launched before or on 6 December 2025, and will be widely supported by the public.

True side of the bet: Tibor Pacher of Perefrinus Interstellar
False side of the bet: Centauri Dreams

Tibor of Pergrinus Interstellar makes his case.

One of the mission specs was a flight time of 2000 years or less to the star of choice. Assuming this is Proxima Centauri simply because of its, well, proximity, we arrive at a minimum average mission velocity of about 650 kilometers per second. That can be compared to Voyager 1’s 17.1 km/s to get an idea of the upgrade in velocity needed, but as we’ve noted in these pages before, the right kind of sail employing a Sun-diver maneuver might get at least close to that speed.

Useful data along the way? Tibor names the targets of opportunity: A craft traveling at 650 km/s gets out to the Kuiper Belt in about a year and reaches the heliosheath at 100 AU. Year two takes it out of the heliosphere entirely, while years five to ten are of note because they take us to the distance of the Sun’s gravitational focus, where Sol acts as a unique lens to magnify distant starlight. Recall that unlike optical lenses (where the light diverges after the focus), a gravitational lens has a focal line that extends to infinity. In other words, separations greater than 550 AU (where the gravitational lensing effect is first available) still offer unique observational possibilities.

Beyond 550 AU, the electromagnetic radiation from the occulted object under study is amplified by a factor of 10**8 (100 million times). The ’spot radius’ (distance from the centre line of the image at which the image intensity gain falls by a factor of 4) has been calculated…to be about 11 km for a Sun-spacecraft separation of 2,200 AU.






Somewhere around year 20 of the Pacher probe’s mission it reaches the Oort Cloud, an area of obvious interest that may, in fact, extend halfway to the target star. We might also mention the Pioneer anomaly, for an outbound Proxima Centauri probe can obviously be studied in terms of anomalous acceleration along its route. Two thousand years after launch, the probe reaches the Proxima Centauri system, but for those who object that surely faster probes would have passed it along the way, I can only agree with Tibor that such a probe would get much done along its route before that happens, given a properly configured mission.


Free Space at Discovery.com has an interview with Elon Musk of SpaceX

SpaceX and Orbital Sciences got a NASA contract for $3.5 billion to deliver stuff to the International Space Station. SpaceX’s share, totaling $1.6 B to start, covered 12 missions, while Orbital, which got an additional $300 million, was responsible for eight.

Elon: The difference is bigger than even the number of launches because our Dragon spacecraft has 50 percent more payload capability than Orbital. It’s actually, if you were to multiple it out, it’s as if we were doing 18 launches and they were doing eight launches.


21st Century Waves looks at an MIT study of the future of human spaceflight

MIT recommends that the International Space Station should be used by the U.S. and its international partners through 2020 to support human spaceflight to Mars. The Bush Vision of Moon exploration should be clarified and expanded so that it is “more, and not less ambitious.”


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