Conscious Choice cover

From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


Available everywhere for $3.99 (before discount) at Amazon, Barnes & Noble, and all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.

LightSail 2 released from cubesat; establishes contact

The Planetary Society’s LightSail-2 technology demonstration satellite was released from its carrier vehicle today and successfully established communications with the ground.

The CubeSat, about the size of a loaf of bread, was scheduled to leave Prox-1 precisely 7 days after both spacecraft successfully flew to orbit aboard a SpaceX Falcon Heavy rocket. Following deployment from its spring-loaded enclosure known as a P-POD, LightSail 2 deployed its radio antenna and began transmitting health and status data, as well as a morse code beacon indicating its call sign. The mission team received LightSail 2’s first signals on 2 July at 01:34 PDT (08:34 UTC), as the spacecraft passed over Cal Poly.

…The team will spend about a week checking out LightSail 2’s systems, exercising the spacecraft’s momentum wheel, and taking camera test images before and after deployment of the CubeSat’s dual-sided solar panels. Following the successful completion of these tests, the team will deploy the 32-square-meter solar sail, about the size of a boxing ring. A time for the solar sail deployment attempt will be announced later.

If they successfully deploy the solar sail and use it to maneuver in space, it will the second time the Planetary Society has done it, having deployed LightSail-1 in 2015. That mission has some communications problems, but eventually succeeded in its main engineering mission by testing the sail deployment system.

LightSail-2 will also be the third time a light sail has been flown in space, with the first, Ikaros, deployed by the Japanese in 2010 and flown in solar orbit through 2012. That mission was successful in using sunlight to accelerate the sail.


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  • Diane Wilson

    Worth noting that the Mercury MESSENGER spacecraft used solar sailing, via its solar power panels, to reduce the number of thruster firings needed to achieve orbit.

  • Diane Wilson: I hadn’t know that! Thank you.

  • On this note, I now wonder if radiation pressure from the Sun has been included in the orbital calculations for the Parker Solar Probe.

  • Diane Wilson

    Given how close Parker is flying to the Sun, I would hope they’ve included radiation pressure! I expect they have; some parts of NASA are still functional. I’m impatient for some reporting on Parker’s findings, but it looks like that will be a while. Parker has completed its second perihelion, but its next major event will be a gravity assist from Venus in December.

  • A couple of comments:

    * The use of ‘trim tabs’ on a spacecraft (applying solar pressure to create small torques on the spacecraft) is not solar sailing per se. These techniques change spacecraft attitude, not the orbit. Solar sailing in the context of the LightSail program means employing solar pressure as the primary propulsion scheme for generating changes in spacecraft velocity (delta V) and thus changing the orbit. The only spacecraft to have done this so far was Japan’s IKAROS spacecraft, on a path between the Earth and Venus.
    * The principal objective of the LightSail-1 mission was to demonstrate solar sail deployment and prove out selected spacecraft subsystems (power, telecom, imagers, etc.). Once deployed, the spacecraft attitude was uncontrollable because of the low orbit (lots of drag), so no solar sailing was possible or attempted. LightSail 2, if successful in its higher orbit, will be the first spacecraft to perform solar sailing in any Earth orbit. (My firm, Ecliptic Enterprises Corporation, is the lead system contractor for the LightSail spacecraft.)

  • Edward

    Space Systems/Loral sometimes (or often) uses a conical, highly reflective structure that they call a solar sail to balance the torque from solar pressure on solar arrays that extend from only one side of their satellites. See figure 3 in the paper below:
    A boom-mounted solar sail in the opposite direction of the solar array, serves as attitude actuator by providing a counterbalance to the solar pressure.

    As Rex notes, above, this is not the solar sail used for propulsion and orbit change. It seems that the term “solar sail” is used whenever this concept of light pressure is used, whether for attitude control or for orbital propulsion.

    I first heard of solar sails when I was a teenager. It seemed like a good idea, but I worried about how close a solar sail could be to the Earth before the atmosphere overpowered the solar propulsion. Based upon (poor?) assumptions, I calculated that coming closer than 1,000 miles could be a problem for a solar sail. LightSail-2 is operating at around 720 km (about 450 miles), so that long-ago calculation seems to be in error by a factor of 2.

    That calculation brought about another thought: would a solar sail caught in Earth’s atmosphere slow down enough when it was high enough that it did not burn up during reentry? Imagine a square-mile aluminized-Mylar sheet settling on a farmer’s field.

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