Atlas V launches 70th mission with NROL-79 from Vandenberg

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The Atlas V rocket marked its 70th mission to space on Wednesday as the veteran rocket lofted the National Reconnaissance Office’s NROL-79 spacecraft to Low Earth Orbit (LEO).  Liftoff took place from SLC-3E at Vandenberg Air Force Base, California, at 0950 PST (1750 UTC).

The NROL-79 Atlas V 401 can be expected to follow an LEO ascent profile, with the RD-180 engine producing 860,000 lbf at liftoff, a level of thrust that will gradually increase to 933,000 lbf as the vehicle breaks through Earth’s atmosphere and enters the vacuum of space.

In its 401 configuration, the Atlas V reached Max Q – the moment of maximum dynamic pressure and mechanical stress on the vehicle – 88 seconds after liftoff at an altitude of 11.6 km (37,970 ft) with a total Max Q of 490 psf.

Throughout the first 100 seconds of flight, the RD-180 engine thrusted at 100% of total throttle, stepping down to 95% of rated thrust from 100 seconds through 210 seconds, at which point a throttle drop off occurred as the booster maintained a 5G acceleration limit in preparation for Booster Engine Cutoff (BECO).

BECO occurred just prior to Atlas/Centaur separation at the T+ 246 second mark at an altitude of ~157.6 km (~517,015 ft).

Ten seconds after Atlas core stage separation, the Centaur single-engine upper stage ignited at the T+ 256 second mark.

Payload fairing jettison followed at T+ 264 seconds at an altitude of 193. km (633,100 ft).

https://www.nasaspaceflight.com/2017/03/atlas-v-nrol-79-vandenberg/

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