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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The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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.
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.
That 5% is assuming NO avoidance maneuvers.
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.
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.
How big is the radiator needed to get rid of 100kw of continuous heat?
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).