SpaceX Falcon 9 Full Thrust - Inmarsat-5 Flight 4 - Launching May 15, 2017
Screenshot from SpaceX Webcast of Inmarsat 5
Mission Rundown: SpaceX Falcon 9 FT - Inmarsat-5 F4
Written: January 27, 2021
Another launch and forget rocket
SpaceX is targeting the launch of Inmarsat-5 Flight 4 from historic Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida. The 51-minute launch window opens on Monday, May 15, at 7:20 p.m. EDT, or 23:20 UTC. SpaceX will not attempt to land Falcon 9’s first stage after launch due to mission requirements.
This is the NOTAM area where booster B1034 will end its maiden voyage after launching I5F4
The Payload
Inmarsat (LSE: ISAT) is a British satellite telecommunications company, offering global mobile services. It provides telephone and data services to users worldwide, via portable or mobile terminals which communicate with ground stations through thirteen geostationary telecommunications satellites.
Inmarsat's network provides communications services to a range of governments, aid agencies, media outlets and businesses (especially in the shipping, airline and mining industries) with a need to communicate in remote regions or where there is no reliable terrestrial network. The company was listed on the London Stock Exchange until it was acquired by Connect Bidco, a consortium consisting of Apax Partners, Warburg Pincus, the CPP Investment Board and the Ontario Teachers' Pension Plan, in December 2019.
The Inmarsat I-5 satellite provides global coverage using four geostationary satellites. Each satellite supports 89 Ka-band beams, giving a total coverage of approximately one-third of the Earth's surface per satellite. In addition, 6 steerable beams are available per satellite, which may be moved to provide higher capacity to selected locations.
On the technical side of the Inmarsat I-5 satellite it is known that it takes 4 days to load it safely with 2 437 kilos of propellant. That is 40% of its mass, and that propellant will be used to reach its intended geostationary orbit and keep its position during the next 15 years or duration of its service life.
6070 - 2437 = 3 633 kg. Doing some math tells us that burning all propellant at an ISP of 320 implies a total delta-V of 320 x 9.8 x ln(6070/3663) = ~1600 m/s. Assuming the same F9 performance as the lighter Echostar 23 and it had more than this to go to reach GEO, much less do its stationkeeping.
If they are doing a Super-Synchronous Geostationary Transfer Orbit with a Block 4 second stage with a more powerful Merlin 1D+ vacuum engine and by reducing inclination they could possibly get the Inmarsat I-5 satellite into orbit with that amount of propellant.
After reading some more data on the Inmarsat I-5 satellite it’s known to have a regular liquid apogee engine with 445 Newton of thrust and 8 electrical powered station keeping thrusters fueled with Xenon. The Xenon Ion Propulsion thrusters consist of 4 x 22 Newton Axial Thrusters and 4 x 10 Newton Radial Thrusters.
Sadly lack of coverage
In March 2014, Malaysia Airlines Flight 370 disappeared with 239 passengers and crew enroute from Kuala Lumpur to Beijing.
After turning away from its planned flight plan and disappearing from radar coverage, the aircraft's satellite data unit remained in contact with Inmarsat's ground station in Perth via the IOR satellite (Indian Ocean Region, 64° East). The aircraft used Inmarsat's Classic Aero satellite phone service. Analysis of these communications by Inmarsat and independently by other agencies determined that the aircraft flew into the southern Indian Ocean and that data was used to guide the search for the aircraft.
Whoever flew Flight 370 got lost, tired and sadly ran out of time and fuel.
If the cabin crew only had a satellite emergency phone in the cabin, then the stewardesses or the passengers could have raised the alarm, before they crashed in the Indian Ocean.
20x20 hindsight tells a story of a pilot tired of debt and a wish to find a deserted island.
Whatever went wrong the passenger and crew shouldn't have been unable to raise the alarm midflight, but that's the tragedy of it. Most people didn't know until sunrise, when the sun came up in the wrong place, and nobody knew what had happened.
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