SpaceX F9 - Inmarsat 6 F2 - SLC-40

Launch Date: February 18
Launch Window: 10:58pm EST (7:58pm PST, 03:58 UTC on the 18th)
Launch site: SLC-40, Cape Canaveral Space Force Station (CCSFS), Florida
Core Booster Recovery: ASDS - JRTI
Booster: B1077.3
Fairings: Reused
Mass: 5500 kg
Orbit: GTO
Yearly Launch Number: 12th

A SpaceX Falcon 9 rocket will launch the Inmarsat 6 F2 communications satellite for London-based Inmarsat. Built by Airbus Defense and Space, the satellite carries L-band and Ka-band payloads to provide mobile communications services to airplanes and ships.

I-6 satellites

The world's most sophisticated commercial communications satellites will power Inmarsat ORCHESTRA’s capabilities for the future.

www.inmarsat.com

Inmarsat-6 F1, 2 (GX 6A, 6B)

Inmarsat-6 is the sixth generation of satellites for the London-based global mobile satellite communications operator Inmarsat. They will have a du...

space.skyrocket.de

"SpaceX Falcon 9 1.1 Launch Sequence at Vandenberg AFB" by jurvetson is licensed under CC BY 2.0.
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[808?]

 

[Grendal]

Another successful GTO launch. A full one minute burn on stage 2 after reaching orbit. Deployment at 675 km and 34,000 km per hour. I'd expect that Inmarsat is very happy. I do not know orbital mechanics, but that seems like it will get the satellite into place with little to no fuel needed.

 

[bxr140]

Another successful GTO launch. A full one minute burn on stage 2 after reaching orbit. Deployment at 675 km and 34,000 km per hour. I'd expect that Inmarsat is very happy. I do not know orbital mechanics, but that seems like it will get the satellite into place with little to no fuel needed.

FWIW all GTO-inserted sats need to expend significant propulsive energy to get into GEO. Like most new mega sats this Airbus sat is electric propulsion so it’s much more efficient than biprop (and total mass of propellant is much smaller than chemical) but near as makes no difference this sat—like all GTOs regardless of propulsion type—will expend well over half of its propellant during orbit raising/circularization and making the inclination change.

 

[Grendal]

FWIW all GTO-inserted sats need to expend significant propulsive energy to get into GEO. Like most new mega sats this Airbus sat is electric propulsion so it’s much more efficient than biprop (and total mass of propellant is much smaller than chemical) but near as makes no difference this sat—like all GTOs regardless of propulsion type—will expend well over half of its propellant during orbit raising/circularization and making the inclination change.

Thanks. I thought you would know.

 

[Electroman]

stupid question: is it possible for any rocket to inject the sat directly into its final parking GEO?

 

[Grendal]

stupid question: is it possible for any rocket to inject the sat directly into its final parking GEO?

The latest FH launches that discard the center core have been "direct to GEO" launches. bxr140 may be able to give more details on that.

 

[ggr]

The latest FH launches that discard the center core have been "direct to GEO" launches. bxr140 may be able to give more details on that.

For a bit more detail, the second stage second burn takes the stage and the payload from a mostly circular low-medium orbit and puts it into an elliptical orbit with its maximum altitude at the right height and place for its intended geosynchronous (Clarke) orbit. However, unless more delta-v is added, it will all just drop back down again. Now theoretically the second stage could add that delta-v, but then you end up with both the satellite and the second stage in orbit up there, which you don't want. So after that second burn to head to GEO, the stage ejects the satellite, and de-orbits itself somehow (thrusters might even be enough given that almost all the weight is gone). The satellite then uses its station-keeping thrusters to stabilize/circularize at the top of the elliptical orbit.

 

[bxr140]

stupid question: is it possible for any rocket to inject the sat directly into its final parking GEO?

Most bigger rockets could direct inject something to GEO (number of upper stage relights willing)…it's just that it’s kind of a suboptimal exercise all around. The main thing is that It’s less energy efficient than GTO so you can’t stuff as much revenue generating mass on your satellite. But also, realistically it’s higher risk, practically it’s more expensive, and it’s no faster than chemical propulsion sats. The only real upside is that it can cut a months long orbit raising phase if a satellite is all electric propulsion.

It’s kinda analogous to wanting a 1000 mile range EV.

It really is a novelty concept. There’s no significant market.

 

[bxr140]

The satellite then uses its station-keeping thrusters to stabilize/circularize at the top of the elliptical orbit.

Perhaps a bit pedantic, in the chemical propulsion use case satellites all have a single large thruster for the GTO—>GEO burns (usually 4-5) that are give or take 25x the thrust of the station keeping thrusters. Its overall more efficient that way. ***There have been contingency cases where the SK thrusters have raised a sat, but that’s generally not preferred because you’d rather not push that much propellant through the SKs…and also the thermal load on the tiny thrusters really drags out the whole exercise.

For all electric sats the thrusters are on gimbals and so they can be oriented for efficient orbit raising burns and then reoriented once on station (and they also track the moving Cg of the sat as the propellant load burns down). Thrust is so low that there’s really no upside to having both low and high thrust variants and the units inherently have enough total impulse for a geo mission, so first principals dictates they double duty the orbit raising and on station work.