A mighty United Launch Alliance (ULA) Delta IV Medium+, carrying the third Global Positioning System (GPS) Block IIF satellite, followed by SpaceX’s impressive Falcon 9, laden with the first Dragon cargo ship under its $1.6 billion Commercial Resupply Services contract with NASA, will both thunder into orbit this week from Cape Canaveral Air Force Station. Current plans call for the Delta to roar uphill at 8:10 am EDT on Thursday 4 October and the Falcon – in what promises to be a spectacular liftoff under the cover of darkness – at 8:34 pm on Sunday 7th.
The Delta will fly from Space Launch Complex (SLC)-37 in its ‘4-2’ configuration, equipped with a 4-metre-wide (13-foot) payload fairing and two Alliant-built strap-on Solid Rocket Motors (SRMs). The vehicle has the capability to insert a payload of up to 12,890 pounds into geostationary transfer orbit. (Interestingly, the launch will come just a few weeks shy of the tenth anniversary of the first Delta IV flight in November 2002.) Its first stage, known as the Common Booster Core, is fed by Rocketdyne’s throttleable RS-68 engine. Liquid hydrogen and oxygen propellants for this engine will be loaded aboard the rocket in a complex, four-and-a-half-hour procedure, terminating a little over two hours before launch. Ignition of the RS-68 will occur at T-5 seconds, followed by the ignition of the 53-foot-tall SRMs at T-0.1 seconds. Pummelling the pad surface with 663,000 pounds of thrust, the Delta will initiate a complex pitch and yaw manoeuvre, eight seconds after liftoff, to establish itself on the proper 105-degree flight azimuth.
Forty-six seconds into the climb, it will go supersonic, under the combined power of its RS-68 and the SRMs. The strap-on rockets will be jettisoned at around T+100 seconds, after which the Common Booster Core will also shut down and be cut loose. Fifteen seconds later, the second stage – known as the Delta Cryogenic Second Stage – will commence its own multi-stage burn to inject the GPS IIF-3 satellite into its preliminary orbit. This second stage, fed by a Pratt & Whitney RL-10B2 engine and capable of delivering 24,750 pounds of thrust, has a potentially exciting future, for it has been tipped to serve on the Block I variant of NASA’s Space Launch System (SLS). At length, three and a half hours after launch, GPS IIF-3 will separate from its payload attach fitting, preparatory to injection into its operational orbital ‘slot’ at an altitude of around 11,047 nautical miles and an inclination of 55 degrees.
Images of the Boeing-built satellite being encapsulated in its composite bisector (two-piece) shell-like fairing were last week released by United Launch Alliance. The 38.5-foot-tall fairing caps off the gigantic Delta IV Medium+, which stands some 206 feet in height. Much of the work to encapsulate the payload, together with the integration of the two SRMs, was done under the protection of the Mobile Service Tower, which will not be retracted from the vehicle until about ten hours ahead of liftoff.
The 3,600-pound GPS IIF-3 is the latest in an ‘interim’ class of GPS satellites to keep the Navstar network operational until the next-generation GPS Block IIIA comes online. The GPS IIF boasts, among other features, improved positioning, velocity and timing accuracy, a reprogrammable processor, an interference-free civilian signal for commercial aviation search and rescue and better resistance to electronic jamming. Two previous satellites in the IIF series were launched in May 2010 and July 2011, before the delivery of this third craft in July of this year, aboard a C-17 Globemaster III airlifter, to Cape Canaveral Air Force Station for final processing. “As each IIF satellite becomes operational, we continue the seamless transformation of the GPS constellation into an even more accurate, reliable and durable navigation resource for the US military and the global civilian user community,” said Craig Cooning, vice-president and general manager of Boeing Space & Intelligence Systems. “Our efficient pulse-line manufacturing process, adapted from Boeing’s commercial airplane production lines, also ensures that we deliver each spacecraft on time and on cost.”
Thursday’s scheduled launch of the Delta will be followed, on Sunday night, by the much-anticipated first dedicated Dragon cargo mission to the International Space Station. Although the spacecraft – developed by entrepreneur Elon Musk’s SpaceX organisation, based in Hawthorne, California – triumphantly completed a voyage to the station in May 2012, Sunday’s launch marks the first of a dozen contracted flights under the $1.6 billion Commercial Resupply Services agreement, signed with NASA in December 2008. At the present time, it appears that both the Dragon itself (whose mission is designated ‘CRS-1’ or ‘SpX-1’) and the Falcon 9 booster are primed and ready to go from SLC-40 at Cape Canaveral Air Force Station. Late in August, SpaceX concluded a launch-readiness evaluation, known as a Wet Dress Rehearsal, for the booster. Last Saturday, 29 September, the Falcon’s nine Merlin-1C engines were successfully hot-fired in a test which enabled SpaceX controllers to rehearse countdown protocols.
Loading of RP-1 propellant (a rocket-grade form of kerosene) and liquid oxygen aboard the Falcon is scheduled to begin around two and a half hours ahead of launch. As the countdown proceeds, the vehicle will be transferred to internal power at T-4 minutes, followed by the arming of the flight termination system – used to destroy it in the event of an off-nominal situation during ascent – and the final topping of oxidiser levels.
Capable of delivering up to 29,000 pounds into low-Earth orbit, the 227-foot-tall Falcon 9’s first stage of nine Merlin-1C engines produces a total liftoff thrust of 1.1 million pounds, whilst the second stage houses a single Merlin-1C. Although the vehicle has not accomplished enough missions for detailed reliability analyses to be made, Elon Musk has emphasised the simplicity of the Falcon 9’s components and systems – including a capability to run the engines up to full power, whilst still secured to the pad, to ensure that all systems are operating normally before liftoff – as a key factor in its favour. This was amply demonstrated on its maiden voyage in June 2010, when its first launch attempt was aborted after first-stage ignition and a ‘fail-safe abort’ was implemented. Ground personnel were able to recycle the rocket for a second (successful) launch attempt later that same day.
The pace at which SpaceX produces these vehicles is impressive: two years ago, Musk’s company reportedly possessed the capability to churn out Falcons and Dragons every three months, with an expectation to double that rate by 2012. The successful flight of an operational Dragon in December 2010 and the spectacular visit to the International Space Station in May of this year certainly contributed in no small measure to SpaceX being one of three companies recently awarded contracts under NASA’s Commercial Crew integrated Capability (CCiCap). Sunday’s launch of the first dedicated Dragon mission is expected to carry around 1,000 pounds of equipment and supplies to the station’s Expedition 33 crew and after a month-long stay will return an estimated 730 pounds of scientific materials and 500 pounds of hardware back to Earth. Although Dragon’s downmass limit is a far cry from the enormous capacity of the Shuttle, it is presently the only operational unpiloted cargo vehicle with the capability to return large quantities of materials to Earth.
Although the arrival and berthing of Dragon at the station – to be effected using the Canadarm2 robotic arm, controlled from workstations in the Cupola – will be a highlight of the next few days, the Falcon 9 will also carry a ‘piggyback’ passenger: a prototype second-generation Orbcomm communications satellite. This 330-pound payload will be deployed from the Falcon’s second stage into a 200 x 470-nautical-mile insertion orbit, inclined 52 degrees to the equator. SpaceX is currently under a $46.6 million contract to launch a total of 18 second-generation Orbcomms by late 2014. Meanwhile, the Dragon cargo missions to the International Space Station are expected to intensify, with the second such flight tentatively planned for January 2013, followed by three per annum thereafter until 2015.Missions » ISS » COTS » Missions » GPS »