Polar-Orbiting Environment Watcher Launches Atop Second-to-Last Delta II

After two foiled launch attempts on Tuesday and Wednesday, the second-to-last Delta II took flight at 1:47:36 a.m. PST on Saturday, 18 November. Photo Credit: ULA/Walter Scriptunas III

Today’s crackling growl of a Delta II taking flight is expected to be repeated only once more, before this impeccably reliable launch vehicle retires from operational service in the fall of 2018. For almost three decades, Delta IIs have risen from Earth 154 times and lofted payloads for communications, national security, science and planetary and deep-space exploration. At 1:47:03 a.m. PST on Saturday, 18 November, a Delta II successfully delivered the first of four Joint Polar Satellite System (JPSS) spacecraft into polar orbit, on behalf of the National Oceanic and Atmospheric Administration (NOAA).

An initial attempt on Tuesday was scrubbed due to a “Red” (“No-Go”) declaration from the Western Range and a late launch vehicle alarm. Due to the brevity of the launch window, there was insufficient time to fully co-ordinate a resolution to the problem. A day later, on Wednesday, upper-level winds proved out-of-limits and a second attempt was scrubbed. With the outlook not expected to improve in time for another 24-hour turnaround, the launch was rescheduled for the weekend.

Saturday’s flawless launch occurred from Space Launch Complex (SLC)-2W at Vandenberg Air Force Base, Calif. The JPSS-1 satellite, to be renamed “NOAA-20” when it enters active service, represents the initial thrust of the United States’ next-generation environmental monitoring network, increasing the timeliness and accuracy of climatic and weather forecasting to minimize risks to human life and property.

As outlined in AmericaSpace’s JPSS-1 preview, this mission has already seen several of its core technologies trialed on the 2011-launched Suomi National Polar-Orbiting Environmental Satellite System (NPOESS) Preparatory Project (Suomi NPP) spacecraft. Originally scheduled to fly earlier in 2017, the mission has met with some delay, partly in response to an intermittent cable short within one of JPSS-1’s scientific instruments and a lengthy campaign to identify and resolve the problem. At length, the 5,000-pound (2,300 kg) satellite was delivered from prime contractor Ball Aerospace & Technologies Corp. of Boulder, Colo., to Vandenberg Air Force Base, Calif., in early September, for final pre-launch processing. JPSS-1 was fueled and encapsulated within its payload fairing, ahead of integration atop the Delta II. A failed battery aboard the rocket forced a four-day delay from 10 November until today.

Flight profile for the JPSS-1 launch. Image Credit: ULA/Twitter

In traditional style, the Delta II for the JPSS-1 launch received a four-digit designation of “7920”, which describes its membership of the 7000-series of the rocket (“7”), the presence of nine strap-on solid-fueled motors (“9”) and a second stage (“2”) and the absence (“0”) of an upper stage. Of the nine strap-on boosters—officially known as Graphite Epoxy Motors (GEM)-40, on account of their 40-inch (101-centimeter) diameter—six would be “ground-lit” at T-0, whilst the remainder were to be “air-lit” in flight. The GEM-40s arrived at Vandenberg in summer 2015, followed by the Delta II core a year later. The vehicle was then vertically stacked and kept in storage until the arrival of JPSS-1.

 

Launch Attempt 1: Tuesday, 14 November

With a 70-percent likelihood of acceptable weather on the West Coast, countdown operations at SLC-2W proceeded normally on Monday evening, heading towards a launch in the small hours of Tuesday morning. Air Force meteorologists from the 30th Weather Squadron at Vandenberg predicted ground winds which may equal or exceed the 26-knot limit as a primary concern which might violate an on-time launch. The Mobile Service Tower (MST) was retracted and secured, roadblocks around the launch complex were established and the blast danger area was cleared, before formal countdown operations got underway at 9:47 p.m. PST Monday.

With nine GEM-40 boosters strapped around its core stage, the second-to-last Delta II stands ready at Vandenberg. Photo Credit: NASA/Twitter

Loading of the Delta II’s 85.6-foot-long (26-meter) first stage with 66,140 pounds (30,000 kg) of a highly refined form of rocket-grade kerosene (known as “RP-1”) began shortly after 11 p.m. Shortly thereafter, the Launch Director conducted a poll for liquid oxygen tanking. All told, the booster required 147,710 pounds (67,000 kg) of oxidizer to propel JPSS-1 into polar orbit. Liquid oxygen loading got underway at about midnight and all tanks were verified at close to 100-percent full, allowing for a nominal cryogenic boil-off and replenishment until close to T-0.

Weather briefings, wind assessments and propellant topping-off activitiesa occupied much of the final hour, before the countdown entered a final, ten-minute hold at the T-4 minute mark. It was expected that the clock would resume counting at 1:43 a.m., to yield an on-time liftoff at 1:47 a.m. However, during this period, a “Hold” condition was reached, due to two issues. The first was the presence of a boat, which had strayed into the offshore danger zone, where the GEM-40 boosters would fall. This raised unpleasant reminders of a similar issue which caused Orbital ATK’s Antares launch to scrub last weekend. The second issue related to a troublesome yaw actuator current on the Thrust Vector Control (TVC) of the Delta II’s second stage. Due to the shortness of the launch window, timed to occur at 1:47:35 a.m., there was not enough time to resolve the issue and Tuesday’s attempt was scrubbed. The MST was returned to enclose the vehicle, prior to a second retraction late Tuesday afternoon, in readiness for the second launch attempt.

 

Launch Attempt 2: Wednesday, 15 November

Moving into a second launch attempt for 1:47:36 a.m. Wednesday, an identical countdown regime was adopted. Weather conditions were better, at 80-percent favorable, although ground winds remained the principal concern. “Weather looks good,” tweeted ULA CEO Tory Bruno late Tuesday evening, as countdown operations began. This was followed by a ULA confirmation that Air Force meteorologists were predicting a 100-percent probability of acceptable weather conditions at T-0.

By 12:30 a.m. Wednesday, liquid oxygen fueling had concluded and the Delta II pressed into topping operations. However, Wednesday was also not to be ULA’s day. Following a hearty discussion on the countdown net about the weather, it was reported that upper-level winds were classified as “Red” (“No-Go”) and at 1:31 a.m. PST Mr. Bruno noted that a scrub had been declared.

 

Launch Attempt 3: Saturday, 18 November

With the upper-level wind situation anticipated to worsen on Thursday and Friday, a decision was made in consultation with the Western Range to reschedule the launch for 1:47 a.m. PST Saturday, 18 November. As a consequence, for the third time in less than a week, the countdown proceeded in the late hours of Friday evening. “The @30thSpaceWing launch weather officer predicts a 100-percent chance of acceptable conditions for liftoff,” ULA tweeted at 11:50 p.m. PST Friday, a little under two hours before T-0. “Skies are clear, visibility is good with no fog, ground winds are light and winds aloft have eased.”

Piercing the darkness, the Delta II’s core stage and six ground-lit GEM-40 boosters ignite at 1:47:36 a.m. PST Saturday, 18 November. Photo Credit: ULA

For the third time, tanking of the Delta II with liquid oxygen got underway shortly before midnight Friday. “Weather is still showing green,” tweeted Mr. Bruno a few minutes later. “Wayward Boat in the neighborhood, but heading off the range. No issues at this time.” By 12:30 a.m. PST Saturday, the rocket stood, fully fueled, and waiting only on the continued suitability of the weather. Steering checks of the first- and second-stage engine nozzles came next and T-0 was realigned for 1:47:36 a.m. PST, halfway through the 66-second “window”.

In keeping with long-held ULA tradition, the Delta II for today’s launch paid tribute to deceased employees. Emblazoned on the side of the booster were the names of the late Eric G. Lemmon and George Dean.

Entering the final minutes, the rocket’s Launch Enable Switch was moved to the “on” position at 1:32 a.m. Final status polls were completed without incident by Launch Director Scott Barney and at 1:40 a.m., just 6.5 minutes before T-0, the JPSS-1 spacecraft was transferred to Internal Power, running off of its on-board batteries until such time as it could deploy its electricity-generating solar array in space. The Launch Director issued a definitive “Go for Launch” and the Western Range verified its readiness. The countdown emerged from its final hold at T-4.

Six of the GEM-40 boosters were ignited at ground-level, with the others air-lit at altitude. Image Credit: ULA

With four minutes to go, the Delta II itself moved to Internal Power, its ordnance and the ignition systems of its nine GEM-40 boosters armed for flight. Propellant tanks were confirmed at flight pressure and at T-60 seconds the Launch Enable Switch was moved to “Flight” mode. At 30 seconds, the liquid oxygen fill-and-drain valves were closed and shortly before launch the call “Green Board” confirmed that all relevant assets were declaring no issues which might prevent an on-time liftoff.

The ignition system was armed at T-10 seconds, allowing for a rapid sequence of events, with the RS-27A engine of the rocket’s core roaring to life at T-2.5 seconds. Moments later, at T-0, the six ground-lit GEM-40s added their crackling tremor to the proceedings. A 1:47:36 a.m. PST, the second-to-last Delta II took flight under 789,000 pounds (357,880 kg) of thrust and rapidly gained altitude. “Making the U.S. a more Weather-Ready nation!” exulted NASA’s Mike Curie, providing launch commentary.

Thirty-two seconds into the flight, the vehicle passed the speed of sound and at 48 seconds encountered a period of maximum aerodynamic turbulence, known as “Max Q” on its airframe. The six ground-lit GEM-40s exhausted their solid propellant and were jettisoned 86 seconds into the flight, their 37.4-foot-long (11.4-meter) frames visible to long-range cameras as they fell away from the rapidly ascending stack.

Following the departure of the Delta II core, JPSS-1 rode the second stage onward to reach its operational polar orbit. Image Credit: ULA

Earlier, Mr. Bruno had described the vehicle as “a forest of SRBs”. In the meantime, the Rocketdyne-built RS-27A was joined by the ignition of the three remaining GEM-40s, which continued the boost towards orbit. After 4.5 minutes of continuous thrust, the Delta II’s first stage burned out and was discarded, making way for the ignition of the Aerojet-built AJ-10-11K second-stage engine to deliver JPSS-1 into orbit.

At 1:51 a.m. PST, the AJ-10-11K flared for the first time and burned for more than six minutes, before shutting down and placing JPSS-1 into a parking orbit at an altitude of 115 miles (185 km) x 407 miles (665 km), inclined 98.69 degrees to the equator.

The combo entered a lengthy phase of “coasting”, which lasted almost three-quarters of an hour, before the engine ignited a second time at 2:41 a.m. This second burn ran for only a handful of seconds, positioning JPSS-1 for deployment at 57 minutes and 30 seconds into the flight. By 2:55 a.m., its single solar array “wing” was confirmed to have unfurled without incident. The spacecraft was inserted into an orbit with a semi-major axis of 4,468.8 miles (7,191.8 km), inclined 98.7 degrees to the equator. “Spacecraft separation and solar array deployment are CONFIRMED,” tweeted JPSS-1 prime contractor Ball Aerospace. “#JPSS1 is power-positive and on its own in orbit!”

A third burn—only ten seconds in duration—followed at 75 minutes to prepare for the deployment of the Delta II’s load of five tiny CubeSats. A final burn then positioned the second stage for oceanic impact.

JPSS-1 undergoes thermal vacuum chamber testing, ahead of transportation from Ball Aerospace to Vandenberg for launch. Photo Credit: Ball Aerospace

Today’s flight marked the 154th and second-to-last launch of a Delta II, with only the ICESat-2 payload in September 2018 still on its books. First flown in February 1989, the earliest incarnation of the rocket was built by McDonnell Douglas and, most recently, by ULA since the latter was formed in December 2006. In the immediate aftermath of the loss of Challenger, plans to gradually phase out U.S. expendable vehicles in favor of the shuttle were avandoned and the reliable Delta was brought back into production as the Delta II.

Its inaugural mission boosted a Global Positioning System (GPS) Navstar into orbit and over the next two decades it sent seven orbiters and landers to Mars, including the two rovers, Spirit and Opportunity, in the summer of 2003. The Delta II also lofted the Near-Earth Asteroid Rendezvous (NEAR) in February 1996, the Genesis solar-wind sample-return spacecraft in August 2001, the ill-fated Comet Nucleus Tour (CONTOUR) in July 2002, the Spitzer Space Telescope in August 2003, the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) mission to Mercury in August 2004, Deep Impact in January 2005, Dawn in September 2007 and Kepler in March 2009.

In spite of a partial failure to deploy KoreaSat-1 into orbit in August 1995, due to the failure of one of its Solid Rocket Motors (SRMs) to separate properly, and a catastrophic explosion, just 13 seconds after liftoff, in January 1997, which destroyed the first GPS Block IIR satellite, the Delta II can boast a virtually unblemished service record. Its success rate hovers at 99.3 percent. Original plans called for it to phased out of service in 2011, following Air Force calls to discontinue its use as a satellite lifter. However, that September, NASA added the Delta II to its NASA Launch Services (NLS)-II contract, which provided for four more bookings, of which JPSS-1 is the third.

 

 

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