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Archive for September, 2007

27-Sep-07 | Delta flight 327 – Dawn

Two Dawns over Florida

Twenty-one minutes after local sunrise today, a three-stage Delta II-Heavy lifted off from Cape Canaveral’s SLC-17B into a gorgeous deep blue sky. Aboard was the Dawn spacecraft, which has successfully begun its eight-year asteroid tour.

No major technical issues arose during the three-hour terminal countdown, which began at 04:20 EDT. The weather forecast improved throughout the count, as isolated rain showers remained over Patrick Air Force Base to the south of the Cape and did not violate launch rules. Meanwhile, the countdown’s final hold at T-minus 4 minutes was extended for nearly fifteen minutes due to a civilian ship that had intruded into the offshore hazard area. The Coast Guard quickly shooed away the interloper and the countdown was able to resume for a T-zero near the middle of the twenty-nine-minute launch window. The official range liftoff time was 07:34:00.372 EDT.

The Delta 7925-Heavy, with its upsized GEM-46 booster motors, sprinted from the launch pad and performed typical first and second stage firings, placing itself just over nine minutes later in a nominal parking orbit of 99.99 by 100.6 nautical miles altitude with an inclination of 28.6 degrees. After a 42.5-minute coast phase, the second stage re-lit to achieve an elliptical orbit with a 95.29-mile perigee and 3681-mile apogee. The third stage and spacecraft spun up, separated, and fired to place the spacecraft in a heliocentric departure orbit. Dawn was released at T+plus 61 minutes, 58 seconds, and within a couple of hours was judged by mission controllers to be “stable, power positive, and safe.”

NASA Launch Director Omar Baez summed up the Delta II performance by saying, “we’re right on the money.” The launch extended Delta II’s record-setting benchmark for reliability, which now stands at 76 consecutive successes.

Dawn is the ninth mission* in NASA’s highly successful Discovery Program. Dawn’s mission plan includes a gravitational swing-by of Mars in February 2009 prior to intercepting asteroid Vesta in August 2011. It will remain there for about nine months before departing for asteroid Ceres, a six-month visit that is expected to occur in 2015. Dawn will navigate toward these rendezvous using a xenon ion engine similar to that used on the highly successful Deep Space 1 mission, which launched aboard Delta 261 in 1998.

24-Sep-07 | Dawn delayed by a day

Stormy weather at Cape Canaveral prevented hypergolic propellant loading of the Delta II second stage on Sunday. This has been a common issue lately: Phoenix slipped by a day in August, and before that Dawn also saw a one-day slip prior to its two-and-a-half-month postponement. The launch of Dawn is now scheduled for Thursday, 27 September, with a 29-minute window opening at 11:20 UTC.

20-Sep-07 | A question about the west coast’s final “Super Six”

A reader e-mailed with an interesting hypothesis about a possible error buried deep within the Flight Log:

I have a question on one of the last flights from pad 2E at Vandenberg AFB—or perhaps one of the first Delta flights from pad 2W.

Something seems a little odd with the sequence as it’s commonly listed:

The Jan. 23, 1970 flight of Tiros-M (ITOS-1) on a Delta N-6 (Delta 76) was the first flight off Pad 2W after, as you note, its modification to accept the six solid configuration.

The Dec. 11, 1970 flight of ITOS-A (NOAA 1) on a Delta N-6 (Delta 81) also is listed off Pad 2W. So far, so good.

The next Delta N-6 flight from Vandenberg comes on Oct. 21, 1971 (Delta 86) with the launch of ITOS-B. It’s listed as coming off Pad 2E however, not 2W. This seems rather odd to me as it would require 2E to have been modified for the N-6 when there’s already a perfectly capable pad available, and 2E would soon be torn down. The two remaining launches off 2E do not involve the six solid configuration.

This makes a lot of sense. On-line sites all concur about the flight having been from 2-East, but they are likely cribbing from each other. This site’s original source was the 1991 edition of Steven J. Isakowitz’s International Reference Guide to Space Launch Systems, which may well have had a typo—after all, W and E are adjacent on the keyboard. A check of the updated 2004 edition is pending. Meanwhile, readers with further information on this conundrum are asked to comment on this post.

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19-Sep-07 | Next launch

The next Delta II launch will be NASA’s Dawn spacecraft, expected to launch from Cape Canaveral on 26 September. This flight was delayed from July in order to accommodate the tight launch window of Phoenix, which is now on its way to Mars. Dawn is an asteroid tour that will last eight years.

19-Sep-07 | Delta flight 326 – WorldView 1

On Tuesday, 18 September 2007, a two-stage Delta II launched WorldView 1 for the DigitalGlobe system.

The United Launch Alliance flight team produced yet another flawless countdown, with no apparent issues to address. Upper level winds, initially a concern, improved throughout the morning and were not a factor.

The Delta 7920 model, flying with a 10-foot-diameter composite fairing, leapt off the pad at SLC-2W at the opening of its fourteen-minute window, at an official range liftoff time of 11:35:00.526 PDT. As is typical for Delta II launches from Vandenberg, the vehicle retained its ground-lit solid boosters for more than 20 seconds after burn-out in order to avoid dropping them near off-shore oil platforms; a dog-leg manoeuvre was also included in the flight profile to correct for a path that initially aimed toward the southwest, for similar safety reasons.

Following first and second stage burns and an approximately 43.5-minute coast phase, the second stage relit for a brief orbit adjustment, then imparted a gentle spin to the spacecraft for stabilization prior to release into a nearly-circular polar orbit, about 270 nautical miles in altitude. (For a complete play-by-play, check out Justin Ray’s always informative Mission Status Report at SpaceflightNow.com.)

WorldView 1 is a new commercial imaging satellite with impressive capabilities, not least of which is half-meter resolution. From its polar orbit it will be able to image any point on Earth with an average revisit time of 1.7 days, and its high-capacity on-board memory can store up to 290,000 square miles of half-meter imagery per day. Given its potential for intelligence gathering, it comes as no surprise that the U.S. government is already signed on as a customer. WorldView’s predecessor, Quickbird 2, also launched on a Delta II in 2001.

The flight, the 130th for Delta II since its debut in 1989, set a new all-time record for consecutive launch successes at 75. Previously, the Delta II had been tied with the Ariane 4, which saw its final launch in 2003.

Many people involved with Tuesday’s launch had strongly positive words for Delta II reliability, including Kris Walsh, United Launch Alliance’s director of NASA and commercial programs for Delta, who said, “It’s a great little rocket. I’ll continue to fly it as long as I can.” Nevertheless, with the U.S. Air Force moving to the larger Delta IV and NASA uncertain about maintaining the Delta II infrastructure by itself, the production line is shutting down, and only 25 vehicles remain to be flown.

Close observers of the Delta II may have noticed that the Delta insignia on the vehicle no longer includes the stars signifying consecutive successes (as detailed in the FAQ), something that has been eliminated since ULA began managing launches. Perhaps someone realised how cluttered 75 stars can be! (Kudos and congratulations to everyone at ULA for this “stellar” record… pardon the pun.) -ed.

     

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