SpaceX is planning to launch a Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral at 21:04 UTC on 2022-06-08 to place Nilesat 301, a communication satellite, into a geostationary transfer orbit for eventual service at the 7° west slot in geostationary orbit. Nilesat 301 is owned by Egyptian government company Nilesat, and will provide broadcast television and broadband Internet service to customers in Egypt, oil fields in the eastern Mediterranean, and new customers in east and sub-Saharan Africa.
The Falcon 9 booster, B1062, will be making its seventh flight and will land on an offshore drone ship. Both fairing halves have flown before.
The launch was delayed from its originally scheduled date because the satellite, which was originally planned to be delivered from the manufacturer in France to Cape Canaveral by a Russian-operated Antonov cargo plane, had to be shipped by sea due to sanctions against Russia.
The launch, booster landing, and payload deployment were all completely successful. I have cued the replay video to start one minute before launch. Scroll back if you want to see the preliminaries, including information on the Nilesat payload.
Interestingly, this was SpaceX’s first launch to geosynchronous transfer orbit (GTO) in 2022. Not long ago, the commercial launch business seemed to be dominated by launches of communication satellites to geostationary orbit. A principal design goal of Ariane 5 was to reduce the cost of these launches by carrying two unrelated payloads to geostationary orbit on each launch. Now, with the increased lifetime of communication satellites and much of the growth being in low Earth orbit constellations, geostationary launches are becoming a decreasing fraction of the launch business.
I am repeatedly struck by the absence of vibration evident in videos of ascending boosters (and second stages after their engines ignite). My intuition (that’s all I have to go on) tells me significant engineering effort has gone into removing whatever vibration inheres in controlling rocket engines of various sorts. Is vibration, indeed, an inherent and problematic property of rocket engines? Is there an interesting history of taming it?
There are two main sources of vibration during rocket flight. The first is inherent to the engine, where combustion is a violent process, subject to instabilities and, even when they are quickly damped out, a source of vibration transmitted to the structure of the rocket. The second source is acoustic pressure waves (intense sound) of the rocket exhaust and its interaction with ambient air. If you watch the ascent of the Falcon 9 in the video above, you’ll see shaking of the ground-based tracking camera, located more than kilometre from the launch pad, due to the sound waves from the rocket shaking its mounting. The effect of this on the rocket is profound during the early part of the flight (the “rain birds” that spray water around the pad during ignition and initial climb suppress the sound radiated back to the rocket by using part of its energy to break up droplets of water). This is a more important function than cooling the launcher. One of the functions of the payload fairing is protecting the payload from this noise-induced vibration—there is acoustic insulation on the inside of the fairing. The effects of noise do not, however, last for long, because as the rocket climbs, the thinner air around it cannot transmit sound as well and once the rocket goes supersonic, sound from the engines transmitted through the air cannot reach the payload.
Because combustion instability imposes stress on engine components and, if uncontrolled, can tear an engine apart, a great deal of effort has been expended to understand and reduce it and, over the years, engineers have gotten better at making their engines run smoother. A small engine will generally be less prone to instabilities and vibration than a large one, which is why the Soviets/Russians opted for engines with multiple smaller combustion chambers instead of huge engines like the Americans. They were heavier and less efficient, but they didn’t have to spend years trying to figure out how to keep them from blowing up as the U.S. did with the Saturn V first stage engine and Space Shuttle Main Engine. The Falcon 9 doubtless runs much smoother for having nine smaller engines than if it had just one or two big ones.
