The ground of Cape Canaveral Air Force Station, Fla., shook under 1.3 million pounds (590,000 kg) of thrust this morning (Saturday, 10 January), as SpaceX’s Falcon 9 v1.1 booster—laden with the fifth dedicated Dragon cargo mission (CRS-5) to the International Space Station (ISS)—roared away from Space Launch Complex (SLC)-40 precisely at 4:47:10 a.m. EST. It was notable that the company which last September won contracts to possibly launch the first U.S. astronauts from U.S. soil since the end of the shuttle era has now achieved the first launch of a U.S. vehicle from U.S. soil in 2015. At the time that this article was being prepared, the Dragon spacecraft had successfully separated from the second stage of the booster and had successfully deployed its electricity-generating solar arrays, its Guidance and Navigation Control (GNC) Bay Door, and critical rendezvous sensors, ahead of a scheduled capture and berthing at the space station by Expedition 42 Commander Barry “Butch” Wilmore and Flight Engineer Samantha Cristoforetti on Monday morning.
Originally planned for launch last month, the CRS-5 mission—which marks the fifth dedicated Dragon flight under the language of SpaceX’s $1.6 billion Commercial Resupply Services contract with NASA, signed back in December 2008—was delayed into the New Year by “an abundance of caution” in the aftermath of a troubled Static Fire Test of the nine Merlin 1D engines on the Falcon 9 v1.1’s first stage. Although the test was repeated, with apparently full success, on 19 December, it was decided to delay until January and provide SpaceX engineers with sufficient time to examine their data and confidently commit to a revised launch schedule.
An opening attempt at 6:20:29 a.m. EST on Tuesday, 6 January, appeared charmed, as weather conditions at the Cape steadily improved from 60 percent favorable to 90 percent favorable, jeopardized by the slight risk of violating the Thick Cloud Rule. Both the Falcon 9 v1.1 and her CRS-5 Dragon payload also enjoyed a smooth processing flow and countdown, passing through the standard poll of all ground stations at T-13 minutes and heading into the Terminal Count at T-10 minutes. However, a “Hold, Hold, Hold” call emerged from a member of the SpaceX launch team at T-85 seconds and the clock was halted shortly thereafter, at T-81 seconds. Since the ISS rendezvous commitment of this mission gave it just a single second in which to launch, it was immediately obvious that a delay was inevitable. In the minutes after the scrub, SpaceX and NASA reported that “drift on one of the two thrust vector actuators on the second stage” was the root cause, and that had engineers not spotted the problem and manually halted the countdown, it would “likely have caused an automatic abort,” closer to T-0, as this was outside the bounds of acceptable Launch Commit Criteria (LCC).
In the meantime, the problematic thrust vector actuator—manufactured by Tempe, Ariz.-based Jansen’s Aircraft Systems Controls, Inc. (JASC)—was replaced and tested. The second actuator was unaffected and was not replaced, but was subjected to exhaustive testing. According to JASC, the 13.4-pound (6.1-kg) actuators are “designed to control the thrust vector angle of the SpaceX Falcon 9 first- and second-stage engines.” Intended for high vibration and shock loads, the actuators also benefit from excellent frequency-response characteristics. It was initially hoped that a second attempt at 5:09 a.m. EST Friday, 9 January, but SpaceX opted to err on the side of caution and moved to 4:47 a.m. EST Saturday, 10 January, placing the launch about 2.5 hours before sunrise in Florida.
Both days benefited from an 80 percent likelihood of acceptable weather conditions, with Flight Through Precipitation and Thick Cloud identified as the primary factors of violation. “Late Friday and into Saturday, winds back northerly in response to a high-pressure surge in the Southeast U.S., but a slight risk of precipitation remains,” the 45th Weather Squadron at Patrick Air Force Base reported. “Also on Saturday, an upper-level feature transits the northern portions of the Florida Peninsula, bringing upper-level cloudiness and a slight risk of thick clouds.”
Unperturbed, the Falcon 9 v1.1 booster was elevated into a vertical orientation on SLC-40 and the process of fueling with liquid oxygen and a highly refined form of rocket-grade kerosene (known as “RP-1”) got underway. 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), required the fuel lines of the engines to be chilled, in order to avoid thermally shocking or fracturing them. With all propellants aboard the vehicle, the countdown reached its final “Go-No Go” polling point of all stations at T-13 minutes at 4:34 a.m. EST Saturday.
Passing through the polls, the Terminal Countdown commenced at T-10 minutes. During this phase, the nine Merlin 1D engines were chilled, ahead of ignition, and all external power utilities from the Ground Support Equipment (GSE) were disconnected. At 4:41 a.m., the Falcon 9 v1.1 transitioned to internal power and, a couple of minutes later, the roughly 90-second process of retracting the “strongback” arm from the stack got underway. The Flight Termination System (FTS)—which would destroy the rocket in the event of a major accident during ascent—was placed onto internal power and armed at 4:44 a.m.
Hissing and whining like a real dragon, about to break the shackles of Earth, the vehicle moaned through its final stages of tanking and pressurization. The Merlin 1D engines were purged with gaseous nitrogen and the Launch Director issued a definitive “Go for Launch.” This was followed by a clipped “Range Green” from the Range Operations Co-ordinator (ROC), and at T-60 seconds the SLC-40 complex’s “Niagara” deluge system of 53 nozzles was 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 nine Merlin 1Ds roared to life, ramping up to a combined thrust of 1.3 million pounds (590,000 kg). Following computer-commanded health checks, the stack was released from SLC-40 at 4:47:10 a.m. EST to kick of the first U.S. space mission of 2015, a year which will also see the major reconfiguration of the ISS to someday handle dockings by SpaceX’s Dragon V-2 crew capsule.
Immediately after clearing the tower, the booster executed a combined pitch, roll, and yaw program maneuver to establish it onto the proper flight azimuth to inject the CRS-5 Dragon spacecraft into low-Earth orbit. Coming 2.5 hours before sunrise in Florida, the ascent proved electrifying for observers and turned night into day across the marshy landscape. Eighty seconds into the climb uphill, the vehicle exceeded the speed of sound and experienced 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 underwent a chill-down protocol, ahead of its own ignition later in the ascent. At 4:49 a.m., 130 seconds after liftoff, two of the first-stage engines throttled 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 engines shut down and, a few seconds later, the first stage separated from the rapidly ascending stack, heading for an experimental landing on SpaceX’s Autonomous Spaceport Drone Ship (ASDS) in the Atlantic Ocean. Although the ASDS was a brightly lit target for the first stage, it was nonetheless remarkable that this first landing attempt was made in the hours of darkness. With the departure of the first stage, the turn then came for the restartable second stage, whose Merlin 1D Vacuum engine—with a maximum thrust of 180,000 pounds (81,600 kg)—came to life to continue the boost into orbit. It burned 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, was jettisoned. Ten minutes after departing the Cape, the sixth overall ISS-bound Dragon will separate from the second stage and unfurl its two 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 Monday, 12 January.
Another complicating factor is that Dragon must arrive at the ISS as quickly as possible, due to the presence of several science experiments which cannot survive for a long period in transit. In total, the CRS-5 payloads will support 256 separate investigations during the current Expedition 42 and the following increment, Expedition 43, which is expected to run under Terry Virts’ command from mid-March until mid-May 2015. One of these experiments will study planarian flatworms—which are capable of rebuilding body organs and nervous systems after damage—to better understand the process of wound healing in space. “Gravity, and the lack thereof, influences the way cells behave and their ability to rebuild tissue,” SpaceX explained in its CRS-5 press kit. “Studying planarians in space may reveal new aspects of how cells rebuild tissue, which could lead to breakthroughs in medical treatment for humans.”
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, Yelena Serova, and 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 at the Johnson Space Center (JSC) 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 Thursday morning, 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 Monday—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.
As for the first stage Falcon-9 booster landing attempt….
Laden with more than 3,700 pounds (1,680 kg) of experiments, technology demonstrations, and supplies, 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 Dragon vehicle on 8 October. In addition to CATS, the CRS-5 mission also carries an IMAX camera for filming during four upcoming ISS increments, together with tools to be used during a series of U.S. spacewalks to support the arrival of two International Docking Adapters (IDAs) in June and December.
Present plans envisage the CRS-5 Dragon remaining berthed at the ISS for about four weeks, with its robotic unberthing, departure and return to Earth anticipated in early February. 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), Russia’s Progress, and Orbital Sciences’ Cygnus—are loaded with trash and intentionally incinerated in the dense upper atmosphere.
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