Almost three months since its last flight and since winning a $2.6 billion slice of NASA’s Commercial Crew transportation Capability (CCtCap) “pie,” SpaceX—the Hawthorne, Calif.-based launch services company, headed by entrepreneur Elon Musk—stands primed to launch its seventh Falcon 9 v1.1 booster of 2014. Liftoff of the two-stage rocket from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., is currently scheduled to occur no sooner than 1:20 p.m. EST on Friday, 19 December, whereupon the fifth dedicated Dragon cargo ship will embark on a two-day rendezvous profile to reach the International Space Station (ISS). The spacecraft will deliver more than 3,700 pounds (1,680 kg) of experiments, technology demonstrations, and supplies for the incumbent Expedition 42 crew and will remain berthed at the station for about four weeks.
Although nearly three months have elapsed since the Cape last shook to the roar of the Falcon 9 v1.1’s nine Merlin 1D first-stage engines, 2014 has long since shaped up to be the company’s most successful year to date. First trialed in June 2010, the Falcon 9 achieved a flight rate of only two missions per annum through the end of 2012, before executing three launches in 2013. These included a Dragon cargo mission to the ISS in March, the maiden voyage of the uprated Falcon 9 v1.1 in September, and SpaceX’s first commercial geostationary payload, the SES-8 communications satellite, in December. The latter mission was covered by AmericaSpace’s imagery team in an expansive Photo Feature. Having thus picked up the baton, SpaceX continued to run with it and triumphantly delivered a second geostationary satellite (Thaicom-6) into orbit in January 2014, followed by two more Dragon missions to the ISS in April and September.
However, the Falcon 9 v1.1’s fortunes proved mixed during a frustrating summer, which saw its Orbcomm OG-2 mission delayed repeatedly, before a successful launch on 13 July. SpaceX also received some criticism from several areas of the media after initially announcing that it would not televise the launch. In the aftermath of the OG-2 flight, a “personal best” was established on 5 August, when another Falcon 9 v1.1 delivered the AsiaSat-8 communications satellite into geostationary transfer orbit, marking the first occasion on which SpaceX had flown twice in as little as three weeks. It also surpassed the company’s 2013 record by marking a fourth flight in a single calendar year. This latter achievement was itself broken on 7 September, when another Falcon 9 v1.1 delivered AsiaSat-6 into orbit … and again on 21 September, when the second Dragon cargo mission of 2014 roared perfectly into orbit. With Friday’s upcoming flight, SpaceX will close out 2014 by launching a third Dragon within a single calendar year for the first time.
The SpX-5 mission is the fifth of 12 dedicated Dragon flights, executed under the language of SpaceX’s $1.6 billion Commercial Resupply Services (CRS) contract with NASA, signed back in December 2008. Under the provisions of the contract, the company is required to deliver a combined total of 44,000 pounds (20,000 kg) of equipment and supplies to the ISS. Dragon accomplished an initial Commercial Orbital Transportation Systems (COTS) test flight to the station in May 2012, before kicking off the first of its 12 dedicated missions (CRS-1) in October of the same year. Further missions followed in March 2013, April 2014, and September 2014, with the launch of CRS-5 slightly delayed from its original target of no earlier than 16 December, as a result of the juggling of payloads and cargo priorities in the aftermath of Orbital Sciences’ Antares explosion and the loss of the ORB-3 Cygnus cargo ship on 28 October.
Assuming that NASA and SpaceX press ahead with the plan to launch SpX-5 on Friday—a decision which is expected to be finalized in a press briefing at the Kennedy Space Center (KSC) on Thursday, 18 December—the weather forecast anticipates mostly cloudy conditions, a 20 percent likelihood of rain, and a 10 percent chance of lightning. The Falcon 9 v1.1 will be transferred to SLC-40 and will undergo a standard “hot-fire” test of the nine Merlin 1D first-stage engines, after which it will be fueled with liquid oxygen and a highly refined form of rocket-grade kerosene (known as “RP-1”). The cryogenic nature of the oxygen, whose liquid state exists within a temperature range from -221.54 degrees Celsius (-368.77 degrees Fahrenheit) to -182.96 degrees Celsius (-297.33 degrees Fahrenheit), requires the fuel lines of the engines to be chilled, in order to avoid thermally shocking or fracturing them. All propellants should be fully loaded within one hour, and at 1:07 p.m. EST Friday the countdown will reach its final “Go-No Go” polling point of all stations at T-13 minutes. Due to the nature of its destination, this launch window will be an “instantaneous” one, with no margin to accommodate technical issues or poor weather. If the vehicle cannot launch on time, the attempt will be scrubbed and the clock recycled.
Passing through the polls at T-13 minutes, the Terminal Countdown will get underway at T-10 minutes. During this phase, the Merlin 1D engines will be chilled, preparatory to their ignition sequence. All external power utilities from the Ground Support Equipment (GSE) will be disconnected, and at 1:15 p.m. EST the roughly 90-second process of retracting the “strongback” away from the vehicle will get underway. The Flight Termination System (FTS), which is tasked with destroying the Falcon 9 v1.1 in the event of a major accident during ascent, will be placed onto internal power and armed.
By T-2 minutes and 15 seconds, the first stage’s propellant tanks will attain flight pressure. The Merlin 1D engines will be purged with gaseous nitrogen, and at T-60 seconds the SLC-40 complex’s “Niagara” deluge system of 53 nozzles will be activated, flooding the pad surface and flame trench with 30,000 gallons (113,500 liters) of water, per minute, to suppress acoustic energy radiating from the engine exhausts. At T-3 seconds, the Merlins will roar to life, ramping up to a combined thrust of 1.3 million pounds (590,000 kg). Following computer-commanded health checks, the stack will be released from SLC-40 to commence SpaceX’s seventh and last mission of 2014.
Immediately after clearing the tower, the booster will execute a combined pitch, roll, and yaw program maneuver, which is designed to establish it onto the proper flight azimuth to inject the CRS-5 Dragon spacecraft into low-Earth orbit. Eighty seconds into the climb uphill, the vehicle will exceed the speed of sound and experience a period of maximum aerodynamic duress—colloquially dubbed “Max Q”—on its airframe. At about this time, the Merlin 1D Vacuum engine of the second stage will undergo a chill-down protocol, ahead of its own ignition later in the ascent. At 1:22 p.m. EST, 130 seconds after liftoff, two of the first-stage engines will throttle back, under computer command, in order to reduce the rate of acceleration at the point of Main Engine Cutoff (MECO).
Finally at T+2 minutes and 58 seconds, the seven remaining first-stage engines will be shut down, and, a few seconds later, the lower component of the Falcon 9 v1.1 will separate from the rapidly ascending stack. The turn will then come for the restartable second stage, whose Merlin 1D Vacuum engine—with a maximum thrust of 180,000 pounds (81,600 kg)—will come to life to continue the boost into orbit. Based upon previous Dragon missions, it will burn for about six minutes and 45 seconds to inject the cargo ship into a “parking orbit.” During this time, the protective nose fairing, which covers Dragon’s berthing mechanism, will be jettisoned. Ten minutes after departing the Cape in a blaze of night and noise, the sixth overall ISS-bound Dragon will separate from the second stage and unfurl its electricity-generating solar arrays, deploy its Guidance and Navigation Control (GNC) Bay Door to expose critical rendezvous sensors, and begin the intricate sequence of maneuvers to reach the ISS on Sunday, 21 December.
In charge of the successful arrival of CRS-5 at the space station are the Expedition 42 crew, commanded by NASA’s Barry “Butch” Wilmore, and also consisting of Russian cosmonauts Aleksandr Samokutyayev and Yelena Serova, as well as recent arrivals Anton Shkaplerov, U.S. astronaut Terry Virts and Italy’s first woman in space, Samantha Cristoforetti. As part of preparations for Dragon, the crew will install the Centerline Berthing Camera System (CBCS) inside the Earth-facing (or “nadir”) hatch of the station’s Harmony node and route video equipment to permit imagery to be obtained by the Robotics Workstation (RWS) in the cupola and by Mission Control in Houston, Texas. As with previous Dragons, CRS-5 will approach the ISS along the “R-Bar” (or “Earth Radius Vector”), which provides an imagery line from Earth’s center toward the station, effectively approaching its quarry from “below.”
In doing so, Dragon will take advantage of natural gravitational forces to provide braking for its final approach and reduce the overall number of thruster firings it needs to perform. By the morning of Sunday, 21 December, it will reach the vicinity of the ISS. A carefully orchestrated symphony of maneuvers will then bring the cargo ship to a “Hold Point” about 1.5 miles (2.4 km) from the space station, whereupon it must pass a “Go-No Go” poll of flight controllers in order to draw closer. Further polls and holds will be made at distances of 3,700 feet (1,130 meters) and 820 feet (250 meters), after which Dragon will creep toward its target at less than 3 inches (7.6 cm) per second.
Critically, at 650 feet (200 meters), it will enter the “Keep-Out Sphere” (KOS), which provides a collision avoidance exclusion zone, and its rate of closure will be slowed yet further to just under 2 inches (5 cm) per second. After clearance has been granted for the robotic visitor to advance to the 30-foot (10-meter) “Capture Point,” the final stage of the rendezvous will get underway, bringing Dragon within range of the 57.7-foot-long (17.6-meter) Canadarm2 mechanical arm. Wilmore will be at the controls for the capture and berthing, with Cristoforetti backing him up. Both astronauts will be stationed within the multi-windowed cupola. Following the initial capture of Dragon—an event anticipated to take place at about 6 a.m. EST Sunday—it will be maneuvered to its berthing interface on the nadir port of the Harmony node.
Physical berthing will occur in two stages, with Wilmore’s crew overseeing “First Stage Capture,” in which hooks from the node’s nadir Common Berthing Mechanism (CBM) will extend to snare the cargo ship and pull their respective CBMs into a tight mechanized embrace. “Second Stage Capture” will then rigidize the two connected vehicles, by driving 16 bolts, effectively establishing Dragon as part of the ISS for the next four weeks. Shortly afterwards, the Expedition 42 crew will be given a “Go” to pressurize the vestibule leading from the Harmony nadir hatch into the cargo ship.
Laden with more than 3,700 pounds (1,680 kg) of experiments, technology demonstrations, and supplies—and, doubtless, Christmas gifts for the crew and perhaps birthday presents for Wilmore, who turns 52 on 29 December—the CRS-5 Dragon will support much of the scientific research to be undertaken during Expedition 42. One key payload is NASA’s Cloud Aerosol Transport System (CATS), to be installed on the Exposed Facility (EF) of Japan’s Kibo laboratory module. This instrument will spend between six months and three years measuring the location, composition, and distribution of pollution, dust, smokes, aerosols, and other particulates in the atmosphere, using Light Detection and Ranging (LIDAR).
Operating at three wavelength bands—at 1,064, 532, and 355 nanometers—the data from CATS will be utilized to explore the properties of cloud and aerosol layers, as well as helping to develop and refine climate models and provide insights for future observations of Mars, Jupiter, and other planetary bodies. In readiness for launch, CATS departed NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Md., on 30 September, bound for SpaceX’s facility at Cape Canaveral, for final pre-launch processing. It was installed aboard the unpressurized “Trunk” of the CRS-5 Dragon vehicle on 8 October.
Present plans envisage the spacecraft remaining berthed at the ISS for about four weeks, with its robotic unberthing, departure, and return to Earth anticipated on 19 January. It will be loaded with supplies, hardware, and computer equipment, as well as experiment results, which it will transport back through the atmosphere to a parachute-assisted splashdown off the coast of Baja California. At present, Dragon is the only unpiloted cargo craft capable of returning safely to Earth; by contrast, its partners—Europe’s Automated Transfer Vehicle (ATV), Japan’s H-II Transfer Vehicle (HTV) “Kounotori” (“White Stork”), Russia’s Progress, and Orbital Sciences’ Cygnus—are loaded with trash and intentionally incinerated in the dense upper atmosphere.
Of particular significance on the CRS-5 mission is that the launch phase is expected to conclude with an attempt to return the first stage of the Falcon 9 v1.1 rocket to a soft landing on a 300 x 160-foot (90 x 50-meter) floating platform in the Atlantic Ocean. Known as the Autonomous Spaceport Drone Ship (ASDS), this vast barge—whose appearance was revealed by Elon Musk in a tweeted photograph last month—will be unanchored, but is reportedly capable of precisely holding its position to within 10 feet (3 meters), “even in a storm,” using Differential Global Positioning System (GPS) hardware and four diesel-powered azimuth thrusters, repurposed from deep-sea oil rigs.
Unsurprisingly, Musk has explained that he anticipates no higher than a 50-50 chance of the first stage making a successful landing on the ASDS on its first attempt. However, if it works as advertised, this will mark the first occasion on which SpaceX has returned its Falcon 9 v1.1 flight hardware from the high atmosphere and landed it smoothly onto a solid surface. The company has performed several water splashdowns between September 2013 and September 2014, with mixed results.
Equipped with four fold-out landing legs—made from carbon-fiber and aluminum honeycomb, weighing 4,400 pounds (2,000 kg) and spanning 60 feet (18 meters) when fully deployed—the 150-foot-tall (46-meter) first stage made its initial attempt to return softly to water during the maiden voyage of the Falcon 9 v1.1 in September 2013. Unfortunately, it experienced an uncontrolled roll during descent, which overwhelmed the capabilities of its attitude-control system to compensate. This forced a planned final “burn” of the center Merlin 1D engine to be shortened, due to the centrifugal effect on propellant against the tank walls, which damaged the baffles and allowed for debris intrusion into the powerplant.
A second attempt during the ascent of the CRS-3 Dragon cargo mission in April 2014 met with greater success, experiencing no spin and zero vertical velocity, as planned. This marked the first successful controlled oceanic touchdown of liquid-fueled orbital booster, but due to rough seas the first stage was not recovered. SpaceX’s third attempt took place during the Orbcomm OG-2 ascent in July 2014, and was again successful, although the first stage’s hull integrity was breached when it toppled from vertical to horizontal in the Atlantic and it was not retrieved. Most recently, during the CRS-4 Dragon launch in September 2014, another successful splashdown was logged, but again no attempt was made to recover the first stage, as it was known that it would not survive the tip-over from a vertical to a horizontal orientation into the ocean.
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