SpaceX successfully launched the latest Commercial Resupply Services (CRS) mission to the International Space Station (ISS) on Friday. Following repairs to a a helium valve in the stage separation pneumatic system – which was responsible for Monday’s scrub, the Falcon 9 v1.1 was readied for its next attempt, with the launch of the CRS-3 Dragon from Cape Canaveral’s Space Launch Complex 40 (SLC-40) taking place at 19:25 UTC (15:25 local time).
SpaceX’s Dragon spacecraft was just over an hour away from setting sail on her CRS-3/SpX-3 mission from SLC-40 atop a Falcon 9 v1.1 rocket at 20:58 UTC (16:58 local time) on Monday. With NASA TV coverage beginning, the decision to scrub for the day was part of the introduction to the webcast, that ended moments later.
SpaceX later noted that preflight checks detected that a helium valve in the stage separation pneumatic system was not holding the right pressure. This meant that the stage separation pistons would be reliant on a backup check valve.
The mission would likely have been a success via the back up system. However, per the breach in Launch Commit Criteria (LCC), the launch as called off, the vehicle detanked and repairs to replace the valve initiated once the Falcon 9 was back into its horizontal position.
Those repairs have since been completed, allowing for a new attempt to take place at the next available opportunity, which had already been set for Friday.
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In addition to deploying Dragon, the mission is expected to take a major step towards SpaceX’s ambitions of developing a reusable Falcon 9; the carrier rocket will be equipped with landing gear – in the form of deployable legs at the base of the first stage – for the first time.
This mission had already been delayed several times due to issues beyond SpaceX’s control. Originally expected to occur last December, the CRS-3 mission was initially rescheduled to allow Orbital Sciences Corporation to conduct a Cygnus mission which had been scheduled for around the same time.
A cooling problem aboard the space station forced the Cygnus mission to be delayed while astronauts worked to repair the station, with the Cygnus finally lifting off in January.
The knock-on delays from the Cygnus mission pushed the CRS-3 launch into March, when a combination of payload contamination and a range instrumentation failure led to further delays. The launch had been slated for the end of the month; however the same range problem which delayed last week’s Atlas V launch with NROL-67 – now in orbit and renamed USA-250 – led to another slip in SpaceX’s schedule.
There were concerns that the recent failure of a Multiplexer/Demultiplexer unit (MDM) in the ISS’ truss would force a further postponement to the launch, however NASA have developed a plan which will allow the Dragon mission to launch on time.
The failure affects redundant control of several external components on the US side of the station, including rotation of the solar arrays. In order to avoid any problems should the primary controller fail, the solar arrays will be fixed into a suitable position to accept berthing of the Dragon as soon as the supply craft has launched.
An EVA, planned for April 23 – now Dragon launched on Friday – will replace the faulty unit.
Developed under NASA’s Commercial Orbital Resupply Services (COTS) program, Dragon measures 3.66 metres (12 feet) in diameter with a length of 5.9 metres (19.3 ft). It can accommodate up to 3.31 tonnes (7,300 lb) of cargo, contained within a recoverable pressurised module or its unpressurised trunk section.
The pressurised module gives it the capability, unique among the ISS’ unmanned resupply fleet, to return equipment to the Earth.
Dragon connects to the International Space Station by means of a Common Berthing Mechanism, allowing it to be attached to any of the nodes on the US Segment. The Nadir port of the Harmony module is typically used – the same port also accommodates Cygnus and Kounotori resupply vehicles flown by Orbital Sciences and the Japan Aerospace Exploration Agency, respectively.
The CRS-3 mission marks the fifth flight of SpaceX’s Dragon spacecraft, which debuted in December 2010 with a brief test flight which completed two orbits before being recovered successfully.
After the success of this mission the next flight, which had been planned as a longer-duration test culminating in a rendezvous with the International Space Station, was re-manifested as a cargo delivery mission with berthing conditional on it first completing its other test objectives. In May 2012 this mission saw Dragon successfully arrive at the Space Station.
With its COTS test flights complete, SpaceX began it Commercial Resupply Services (CRS) missions in October 2012. Despite an engine failure during first stage flight, CRS-1 arrived at the International Space Station as planned and completed a successful mission.
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The most recent CRS flight, CRS-2, was conducted last year. Although a thruster failure caused problems early in the mission, the Dragon was again able to complete its mission successfully.
The cargo aboard the CRS-3 mission has a total mass of 2,089 kilograms (4,605 lb).
This consists of 476 kilograms (1,050 pounds) of supplies for the crew, 715 kg (1,600 lb) of equipment for scientific research, 204 kg (450 lb) of replacement parts and hardware for the space station, 123 kg (270 lb) of equipment for conducting extra-vehicular activities, 600 grams (1.3 lb) of computer equipment and 571 kilograms (1,260 lb) of equipment in the unpressurised part of the spacecraft’s trunk.
On its return to Earth the Dragon will be carrying 1,563 kg (3,450 lb) of equipment, including 740 kilograms (1,630 lb) of scientific research.
While many experiments are being carried to the space station, the highlights are the High Definition Earth Viewing (HDEV), Optical Payload for Lasercomm Science (OPALS), T-Cell Activation in Space (TCAS), the Vegetable Production System (VEGGIE) and a pair of legs for the Robonaut 2 prototype which has been aboard the space station since its launch on STS-133 in 2011.
The HDEV system consists of four off-the-shelf cameras which will be used to return external footage of the space station as it orbits Earth.
OPALS will be used to see if optical communications with the ground are practical, a technology which has the potential to increase the station’s communications throughput by at least an order of magnitude.
The T-Cell experiment is expected to study how deficiencies in the human immune system are affected by a microgravity environment. VEGGIE will see the station’s crew grow lettuce aboard the outpost for scientific research, air purification and ultimately human consumption.
In addition to the Dragon, the Falcon 9 launch deployed five CubeSats as part of NASA’s Educational Launch of Nanosatellites (ELaNa) program. These spacecraft, which comprise the ELaNa-V mission, were released from four Poly Picosatellite Orbital Deployers (PPODs) attached to the second stage of the Falcon 9.
ALL-STAR, the Agile Low-cost Laboratory for Space Technology Acceleration and Research, is a three-unit CubeSat built by the University of Colorado at Boulder.
Equipped with the Telescopic High-definition Earth Imaging Apparatus (THEIA) camera, it will be used to return colour images of the Earth, however its primary mission is to test the underlying spacecraft platform for future missions and to provide experience of designing, building and operating a satellite to the university’s students.
KickSat, which was developed by Cornell University and funded through a campaign on the KickStarter website, deployed a constellation of 104 “Sprites” or “ChipSats”. Thin 3.2-centimetre (1.26 in) squares, Sprites carry miniaturised solar cells, a gyroscope, magnetometer and a radio system for communication.
Designed to allow miniaturised experiments, lowering the cost of access to space, the first batch of Sprites are expected to be used to reward members of the public who funded the program via KickStarter.
Sprites are expected to decay from orbit quickly, avoiding concerns which could otherwise arise from deploying so many spacecraft in a single mission. The deployment spacecraft is a three-unit CubeSat.
PhoneSat-2.5, a single-unit CubeSat, is the latest spacecraft in NASA’s PhoneSat program, which has developed small satellites using off-the-shelf smartphone technology.
The fifth PhoneSat to launch, 2.5 is intended to serve as a technology demonstrator for NASA’s planned Edison Demonstration of Smallsat Networks (EDSN) constellation, aimed at using a constellation of picosatellites to conduct coordinated scientific research. EDSN is scheduled for launch on the maiden flight of the University of Hawaii’s SPARK rocket later this year.
SporeSat will be operated by NASA’s Ames Research Center. Developed in conjunction with Purdue University, the satellite will study how the plant ceratopteris richardii grows in space, particularly whether its roots are able to respond to artificial gravity induced by spinning the samples at different rates. A three-unit CubeSat, the spacecraft has a mass of 5.4 kilograms (12 lb).
The TestSat-Lite, or TSAT, mission will use a two-unit CubeSat to study the use of satellite communications to relay data to ground stations.
Developed by Taylor University of Indiana, in partnership with the University of Chile, the satellite will conduct plasma and ionospheric research using energetic particle detectors, a Langmuir probe and a magnetometer. Data will be returned via the GlobalStar constellation of satellites in Low Earth orbit, before being transmitted to the University over the internet.
The Falcon 9 is a two stage rocket developed by Space Exploration Technologies Corporation (SpaceX) of Hawthorne, California.
Formed in 2002 by PayPal founder Elon Musk, SpaceX has to date conducted thirteen orbital launches, ten of which have achieved orbit.
The company’s first launch, which occurred in 2006, made use of the smaller Falcon 1 rocket and did not achieve orbit due to a first stage engine failure caused by corrosion.
Further launches in March 2007 and August 2008 were not much more successful; the former being lost due to unplanned gyrations in second stage flight, and the latter due to residual thrust in the first stage engine causing the first and second stages to collide at separation.
The fourth Falcon 1 launch was SpaceX’s first successful mission; placing a demonstration satellite, RatSat, into low Earth orbit. This was followed the next year by the successful deployment of Malaysia’s RazakSat spacecraft; however the Falcon 1 was withdrawn from service after this mission.
The larger Falcon 9 debuted the following year, and has now conducted eight missions with only one partial failure.
The CRS-3 launch will make use of the v1.1 configuration of the Falcon 9, which is now the standard for all missions. With nine Merlin-1D engines, arranged in an octagonal formation, powering the first stage, the Falcon is designed to survive the failure of an engine early in its mission.
The second stage is powered by an additional Merlin-1D, optimised to provide maximum thrust in a vacuum environment. Both stages are fuelled by RP-1 propellant, oxidised by liquid oxygen.
The launch marked the first time a Dragon spacecraft has launched atop the Falcon 9 v1.1, with previous launches having used the earlier v1.0 configuration. It was also the first time the v1.1 has flown without a payload fairing.
The launch was the ninth for the Falcon 9 overall and the fourth of the v1.1 variant, which first flew last September when it placed Canada’s CASSIOPE satellite, and several secondary payloads, into low Earth orbit in a mission from California’s Vandenberg Air Force Base.
To date, this is the only launch the Falcon 9 has made from Vandenberg, however SpaceX plan to use the site heavily next year.
In its eight launches to date the Falcon 9 has recorded seven successful missions and one partial failure.
This anomaly occurred during the CRS-1 launch, the penultimate flight of the Falcon 9 v1.0, in November 2012. The failure of one of the first stage’s Merlin-1C engines resulted in a loss of first stage performance.
Although the second stage was able to correct this sufficiently for the Dragon to still reach the ISS as planned, the Orbcomm satellite which the rocket was also carrying was deployed into a far lower orbit than had been planned. This satellite was declared a total loss and decayed from orbit after only a few days.
In preparation for launch, the Dragon spacecraft was powered-up around fifteen and a half hours ahead of liftoff, with the rocket itself powering up around the ten hour mark. Fuelling began four hours before the planned T-zero, with oxidiser loading starting forty minutes later.
By T-3 hours and fifteen minutes fuelling was completed and the majority of the oxidiser tanks were full, however topping continued throughout the countdown.
The terminal count began at T-10 minutes, with the spacecraft entering its own automated sequence four minutes later. With final approval for launch from the launch director and range being given between 120 and 90 seconds before liftoff, the vehicle’s tanks were pressurised with around forty seconds to go.
The CRS-3 mission began with ignition of the Falcon’s nine Merlin-1D engines three seconds ahead of liftoff, which is itself timed to occur when the countdown reaches zero. Seventy seconds into its flight the Falcon reached Mach 1, before passing through the area of maximum dynamic pressure at T+83 seconds.
The first stage burn lasted two minutes and forty one seconds, with stage separation occurring three seconds after cutoff. Ignition of the second stage was initiated after staging, beginning a six minute, fifty five second burn.
Early in second stage flight, at around T+205 seconds, the shroud covering the spacecraft’s nose – including its Common Berthing Mechanism – separated to reduce the mass of the vehicle as it ascends towards orbit.
Around 35 seconds after the end of powered second-stage flight, the Dragon separated from the Falcon 9.
The second stage then reoriented to permit deployment of CubeSats from the PPODs attached to the second stage. This deployment occurred within a few minutes of Dragon separation.
After separation, the Dragon deployed its solar arrays and begin a series of manoeuvres to bring it to rendezvous with the International Space Station. Dragon is expected to arrive at the ISS two days later, where it will be grappled by the Canadarm2 robotic arm.
Following capture the Dragon will be berthed with the nadir port of the Harmony module for equipment transfer.
After up to a month berthed at the Harmony module, Canadarm2 will again be used, to unberth and release the Dragon. After departure, the Dragon spacecraft will make a series of three separation burns, followed by a deorbit burn to bring it into the atmosphere over the Pacific Ocean.
Following jettison of the Trunk module, the Dragon will reenter the atmosphere and land under three parachutes in the Pacific Ocean off the west coast of California. The spacecraft will be recovered by ship and returned to SpaceX for unloading.
The launch was classed as another step towards SpaceX’s ambitious goal of developing a fully-reusable rocket.
The first stage flew with legs attached; demonstrating the ability of the first stage to fly with them attached and deploy the legs during descent.
Although no attempt will be made to return the first stage to dry land, the legs are expected to be deployed prior to a controlled landing at sea. On future flights it is hoped the legs will allow the first stage to return to the launch site for recovery on land.
Updates on how this went are still being evaluated. However, while the high sea states may mean the booster can’t be recovered, SpaceX head Elon Musk did note they saw good data on the stage’s return, control and targeting – with confirmation of a soft landing occurring. A new article will be published on Saturday to further outline the effort.
Reusability has always been a goal for SpaceX, with even their earlier Falcon 1 rocket designed to allow recovery of the first stage. To date, SpaceX have not been successful with their attempts to recover a spent stage – either by parachute or powered descent, however each attempt brings them closer to their objective.
The launch pad which was used for the launch was Space Launch Complex 40 at the Cape Canaveral Air Force Station. Built for the Titan IIIC in the late 1960s, the pad was later used by Titan III(34)D, Commercial Titan III and Titan IV rockets, ending with the penultimate Titan IV launch in April 2005 which orbited an Onyx radar imaging satellite for the National Reconnaissance Office.
The fixed and mobile service towers of the old launch pad were torn down in 2008 after the complex had been turned over to SpaceX. In June 2010 the Falcon 9 made its maiden flight from the pad, successfully orbiting a boilerplate mockup of the Dragon spacecraft.
The CRS-3 launch, which marked the eighth time a Falcon 9 has flown from SLC-40, was the sixty-second mission overall to lift off from the pad.
The launch marked the seventh of the year for the United States and the second for SpaceX, following the previous Falcon 9 launch in early January which placed Thailand’s Thaicom-6 communications satellite into orbit. Overall CRS-3 is the twenty-first launch in a year which is yet to see a failure.
SpaceX will follow up the Dragon launch with a mission to deploy six Orbcomm satellites. This was originally scheduled for the end of April, however it is unclear whether the delays to CRS-3’s launch have affected this projection.
Further launches this year will orbit AsiaSat-8, AsiaSat-6, Turkmensat, eleven more Orbcomm spacecraft on a single rocket and two further Dragons on separate rockets conducting CRS missions.
Orbital Sciences have already conducted one CRS mission this year, with their Cygnus spacecraft successfully lifting off on its first operational mission in January. Two further Cygnus flights to the Space Station are planned by the end of the year.
(Images: SpaceX, USAF, NASA, All Star, KickSat SporeSat and via L2′s SpaceX Special Section, which includes over 1,000 unreleased hi res images from Dragon’s three flights to the ISS.)
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