Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

 
Unfortunately, that is exactly where that journey takes him.

 
The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.


He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

 
Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit.
 

Company defends its satellite constellation from NASA criticism

The founder of AST & Science, the company that wishes to launch a constellation of 243 communications satellites, has defended its effort from criticisms expressed by NASA in a comment to the FCC.

“We’re not a bunch of cowboys launching satellites,” said Abel Avellan, founder of AST & Science, in an interview. “This is a serious, well-funded project.” … Avellan said the “SpaceMobile” satellites do indeed have a very large cross-sectional area perpendicular to the ground, as this is the only way to deliver direct satellite-to-broadband signals. “There is no magic,” he said. “If you want something to connect directly to a handset, it’s not going to be a CubeSat.”

Each of the satellites will include a large antenna, comprising an area as large as 900 meters squared. However, Avellan said the satellites will fly edge-on, “like a frisbee, but without the spinning.” He said the satellites’ cross-section along the direction of motion is only about 3 meters squared. The company has calculated that the probability of a collision occurring at random—assuming no avoidance maneuver—to be only about 1-in-5,000 over its lifetime, or 1-in-20 across the entire constellation.

It appears that neither the company nor NASA has as yet begun direct discussions about these issues. NASA’s concerns however could seriously hamper the company’s future.

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8 comments

  • MDN

    A one in twenty lifecycle risk of a random collision seems enormous to me given the debris implications that would have. i’ve seen no reference to the specific orbital zone for this system, but from the data shared infer it is at a higher altitude with MUCH slower decay dynamics than lower altitude orbits where Starlink et al operate.

    I’m supportive of private sector innovation and the allure of global handset connectivity is very alluring. But we need to be careful with licensing the higher things go because the cost of an accident could be significant and persistent. And given what I know so far I side with NASA if the collision risk is just 1:20.

  • MDN: The orbits for this constellation are higher, 720 km.

  • MDN

    Bob:

    Precisely, so potential collisions and the aftermath debris hazards are much, much more important because orbits this high decay quite slowly vs. low Earth orbits. Thus NASA’s critique seems quite reasonable and appropriate. I certainly think the stated 5% probability for a “random” collision over the life cycle of the constellation is prohibitively high for this class of orbit.

  • john hare

    That 5% is assuming NO avoidance maneuvers.

  • Edward

    From the article:
    He said the satellites’ cross-section along the direction of motion is only about 3 meters squared.
    and:
    Still, these are indeed very large and complex satellites. The company has said it is developing a ‘mechanical deployment system’ that will enable on-orbit extension of arrays to produce ‘ultra-high-power generation’ of 100kW, or more.

    First: based upon the article’s description of the antenna being 900 meters squared, although I think they really mean 900 square meters (100 feet by 100 feet for 10,000 square feet rather than 3,000 feet by 3,000 feet for 9 million square feet), their description of the satellite’s cross-section is probably 3 square meters rather then 9 square meters.

    Also, I think that the article’s calculation of a potential 36,000 square meters of space junk is off a bit, and the correct number for the given parameters is only 27,000 square meters.

    Second: to produce 100kW, each satellite will need much more than 9 square meters of solar arrays. In fact, it will require hundreds of square meters of solar arrays, which is a larger cross section than the company let on. Perhaps 400 to 600 square meters, which would be facing the sun rather than the Earth. It seems to me that the chances of a collision is likely much higher than the company has calculated. Although a collision hazard exists with active satellites (dead Cosmos 2251 hit active Iridium 33, in 2009), There is less collision avoidance capability with dead satellites, and NASA’s concern is that new manufacturers tend to have a high loss rate for their new satellites. This is why they are worried about a 10%, 15%, or 30% failure rate for the first 200 satellite constellation.

    So, under normal operating conditions, the constellation has a cross-section along the direction of motion of 60,000 to 100,000 square meters, two or three times as much as for the potential, or expected, space junk.

    If NASA’s concern is based upon the company’s 1/20 chance due to 3 (or 9) square meter cross-section, then NASA’s true concern should be even greater.

  • Jay

    Edward,
    I had to go back and read the article again when I saw you post about the 100kw demand. Yep, they wrote 100kw. The ISS produces about 120kw with its four arrays covering 2,500 square meters. That is a lot of surface area.

  • John Fisher

    How big is the radiator needed to get rid of 100kw of continuous heat?

  • Edward

    John Fisher asked: “How big is the radiator needed to get rid of 100kw of continuous heat?

    Excellent question. 5kW to 10kW geostationary communication satellites have somewhere in the neighborhood of 100 square feet of radiator surface on their north-facing side and south-facing side combined (around 50 on each).

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