1045pm ET Update: About 15 minutes before the Falcon 9 rocket was due to liftoff on Wednesday evening from Florida, the launch was scrubbed. The culprit? Unfavorable upper-level winds. Fortunately, SpaceX has a back-up window that opens again at 10:30pm ET Thursday.
Original post: If the weather and Falcon 9 rocket cooperate, the first batch of SpaceX's Internet satellites will launch from Florida on Wednesday evening. With a mass of 18.5 tons, this will be the company's heaviest launch to date for either the Falcon 9 or Falcon Heavy rocket.
Wednesday's rocket will boost 60 Starlink satellites, each weighing 227kg, to an altitude of 440km. This is the first block of Starlink satellites for what should eventually be a much larger constellation, and they will help SpaceX gauge its performance and conduct tests of several key systems. Over the coming months, these first satellites will be joined by six additional launches carrying similarly sized payloads. These launches will bring the constellation to an initial "operational" capability.
There is no guarantee all will go well, SpaceX founder Elon Musk said during a teleconference with reporters on Wednesday evening. "This is very hard," Musk said. "There is a lot of new technology, so it's possible that some of these satellites may not work. There's a small possibility that all of these satellites will not work."
Launch and release
The launch window opens at 10:30pm Wednesday (02:30 UTC Thursday) and closes 90 minutes later. A back-up launch window will open at the same time Thursday. Weather conditions are currently forecast to be 80 percent favorable for launch.
The initial part of the launch will be familiar to people who have watched a SpaceX launch before. This Falcon 9 first stage has flown twice before, and it will attempt to make a landing on the Of Course I Still Love You droneship in the Atlantic Ocean. The real action will come about 1 hour 2 minutes after launch, when the second stage begins to deploy the Starlink satellites.
— Elon Musk (@elonmusk) May 12, 2019
In order to save mass, each of the 60 satellites will not have its own release mechanism, such as a spring. Instead, Musk explained, the Falcon rocket's upper stage will begin a very slow rotation, and each of the satellites will be released in turn with a different amount of rotational inertia.
"It will almost seem like spreading a deck of cards on a table," Musk said. There may actually be some contact between the Starlink satellites, he added, but they are designed to handle it.
After deployment, the satellites will begin to power up their ion drives and open their solar panels. They will move to an altitude of 550km under their own power. Musk said he is concerned about the solar panel deployment, and he noted that there are two different deployment mechanisms on the satellites for this purpose. He also said the satellites have incorporated new technology with the thrusters as well as phased array antennas that have yet to be fully tested in space.
The satellites are designed to control costs. For example, each will maneuver with Hall-effect thrusters—ion thrusters in which propellant is accelerated by an electric field. The conventional fuel for such a thruster is xenon, which offers high performance. The Starlink satellites, however, will use a different noble gas: krypton. It has a lower density, so the satellite fuel tanks need to be larger, and it has offers less performance than xenon. But krypton can be bought at just one-tenth the cost of xenon, which matters if a company wants to fuel thousands of satellites.
"It costs a heck of a lot less than xenon," Musk said of krypton. (He also joked, in response to a question from Ars about this fuel, that the satellites would be immune to invasion from Superman's native world).
During the call, Musk said each Starlink satellite costs more to deliver into orbit than it costs to manufacture. The list price for a Falcon 9 launch is $62 million. Factoring in a reuse discount and wholesale rates, this means the Starlink satellites cost significantly less than $1 million each to build.
SpaceX is competing with about a half-dozen other companies to develop low-latency, high-bandwidth Internet from space. One competitor, OneWeb, Read More – Source