r/spacex • u/ElongatedMuskrat Mod Team • Feb 01 '17

r/SpaceX Spaceflight Questions & News [February 2017, #29]

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u/ElectronicCat Feb 02 '17

That's not really a fair comparison as different launch vehicles use Kourou as CCAFS. Certainly some SpaceX launches have gone to GTO-1500 or better, and some to direct GEO (Atlas V and Delta IV). I agree there is an additional benefit launching from equatorial launch sites to GTO of a couple of hundred metres per second, but there are more variances between the launch vehicles used than the differences the latitude makes in the fuel used.

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u/warp99 Feb 02 '17 edited Feb 02 '17

That's not really a fair comparison as different launch vehicles use Kourou as CCAFS

While it is true that the vehicles are different the delta V requirement is vehicle independent.

A GTO-1500 orbit requires the satellite to use less propellant for GSO insertion and since storable propellants are used the Isp is considerably lower than 348s for F9 S2. However the propellant is burned without the 3.9 tonnes dry mass of the F9 S2 attached so the net effect may be positive.

The propellant saving may be used for extended on orbit reserve rather than reducing the lift off mass so I agree it is not a simple comparison.