Impressive start, classified payload-this is short sum up of NROL-37 mission which started today from Cape Canaveral.
Finally after 48 hours delay Delta IV Heavy lifted off from SLC-37 in Cape Canaveral AFS. At T-4' rocket was already fueled and ready for delivering to orbit top secret payload for National Reconnaissance Office. Weather was described as favorable with slight wind and temperature at 28°C. At 17:45 GMT everything was set for "go" along with opinions given by launch and mission directors. At 17:47 GMT countdown was resumed and final preparations before launch were performed: at T-4' liquid oxygen tanks in second stage were secured, at T-3'32" first stage and booster hydrogen and oxygen tanks were also secured and their valves were closed. At T-27' final readiness of the rocket was confirmed. At T-4” all three engines from Common Booster Cores ignited. Punctually at 17:51 GMT rocket performed lift off covering launch pad with smoke. During first seconds of flight rocket performed correction to set South Eastern trajectory. At T+1'20" rocket reached speed of sound and passed point of maximum stress point at T+1'30". At T+1'49" rocket reached altitude of 17 km and speed of 2800 km/h. At T+2'56" rocket reached speed of 5 Ma on altitude of 50 km. At T+4' engines of the boosters were cut off and separation from central core was performed. Now central core started to operate with full thrust (at T+4'17") and giving rocket speed of 15 Ma at T+4'32". Main engine cut off was performed after partial thrust command at T+6'. Separation of the first and second stage took place according to plan few seconds after MECO. Next ten seconds after second stage started engine and at T+6'54" payload fairing was jettisoned. Due the classified profile of this mission live coverage was finished before separation and no further details were unveiled.
Delta IV Heavy is largest (with height over 70 m) operated by ULA launch vehicle and is offering favorable technical specification for delivering to orbit extremely large and heavy payloads. It is equipped with 5 m long payload fairing and weight of GTO mission’s cargo up to 14220 kg. Heavy version construction is based on three long for over 40 m CBC (Common Booster Core) and second stage-it is main difference to Medium version, which is relying only on one core first stage. Two additional CBC are operating with full thrust from start to separation helping in reducing fuel consumption of core stage which is providing half of thrust at the same time. Each of weighing 224600 kg CBC is powered with one RS-68 engine fueled with 202000 kg of liquid oxygen and liquid hydrogen with thrust at 3140 kN. After separation core stage is starting to work with full thrust until separation with second stage. Second stage is 5 m long DCSS (Delta Cryogenic Second Stage) and is powered with RL-110-B-2 engine with thrust at 110 kN. It is fueled with 27220 kg of LH2/LOX. Second stage is similar to second stage utilized in Medium version with one difference; interstage in Medium fairing is narrowing from 5m to 4m in diameter; in Heavy fairing is cylindrical (diameter 5m).
NROL-37 is classified mission but according to some sources payload was 9th Orion reconnaissance satellite. These satellites are operating since 1995 and previously were launched on atop of Titan or Delta rockets. Orion satellites are SIGINT satellites designed for collecting intelligence data from space-for example they are intercepting telemetry data from spacecrafts and satellites. They are heavy satellites with assumed weight around 5200 kg with large deployable antennas with span even around 100 m after extending.