Friday saw the first launch of a Delta IV Heavy with the upgraded Pratt & Whitney Rocketdyne RS-68A main engines. The Delta IV was lofting the secret spy satellite code named NROL-15 into orbit for the USA National Reconnaissance Office.
The launch was successfully completed by United Launch Alliance and the USAF at 9:15am EDT after two hours of delays due to technical issues that were resolved over 3 halts to the launch sequence.
The Delta IV Heavy is currently the largest and most powerful rocket in service for the United States. It has a triple core first stage enabling it to lift the heaviest payloads into orbit. At launch the boosters generate over 2.1 million pounds of thrust.
The launch was scheduled for 6:13am EDT and countdown proceeded normally to the T-4 hold. Prior to coming out of the T-4 hold all stations were polled and a GO FOR LAUNCH was given. A minute or so later the countdown resumed and the clocks started running. This was short-lived though as a there was a voltage spike as the rocket switched to internal power.
The problem was analysed and resolved and the countdown was reset at T-4. During the delay the sun had risen over the Cape Canaveral launch pad a glowing orange ball of flame ascended into the sky shilouetting the rocket. T-0 was set for 6:50 and after another successful GO NO-GO poll the clock started again. Once again the launch was foiled, this time by a faulty fill and drain valve.
The same issue on another valve thwarted the next launch attempt. Finally at 9:11 EDT the countdown restarted for the final time. This time the terminal countdown ran all the way to T-0 and launch.
The Delta IV heavy is a spectacular rocket as it launches. As the main cores are lit a cloud of surplus hydrogen gas ignites engulfing the booster cores in a flaming ball. As the ball of flame extinguishes the rocket’s main engines come up to full power and the hold downs are released.
The Delta IV slowly rises into the sky with all three engines burning brightly, and surprisingly cleanly. There is very little smoke to block our view as the rocket gains height. The central core now ramps down to just under 55 percent thrust whilst the external cores are running at 108% and pushing the rocket towards orbit.
After 90 seconds of flight the Delta IV has reached the speed of sound and the maximum aerodynamic pressures are being exerted on the structure. This is called MAX-Q and you can often see a halo of vapour around the nose cone at this time.
At four minutes the two outer boosters have done their work and start to shut down. After engine shutdown they are ejected start their tumble down to earth. This is an interesting thing to watch as they appear to be higher than the main rocket, but this is just due to the curvature of the earth.
The main core now throttles back up to full power for the remainder of the first stage flight, about another minute and a half. At just over 5 and a half minutes into the flight the fist stage has completed its task and the main core engine is shutdown. MECO: Main Engine Cut-Off. A few seconds later the spent core separates from the upper stage and starts its tumble back to earth.
Now the second stage engine starts just over 6 minutes into the flight. Shortly after the payload fairing is ejected and the NROL-15 satellite as exposed. The flight now enters a media blackout as the NRO does not want to broadcast the location and purpose of the satellite. Indeed there has been much speculation about the deployment method for this spacecraft, some suggesting that the increased thrust was required as the NRO were putting up a decoy to cloak the real location of the NROL-15 satellite. The most likely explanation is that the upper stages were carrying extra fuel to allow the spacecraft to perform some evasive manoeuvres allowing it to be positioned without the knowledge of other nations.
Due to the number of holds that we experienced we are unable to provide our normal launch video but we do have a short scene from liftoff and some stunning images of the Delta IV Heavy as it rose into the Floridian skies.