SpaceX launched its eighth Dragon resupply mission, on a flight that was scheduled to loft cargo to the International Space Station – along with a docking adaptor for future manned missions. However, the launch failed just over two minutes into the ascent from Cape Canaveral’s Space Launch Complex 40 at 10:21 local time (14:21 UTC), due to a presumed second stage issue.
The mission was lost 139 seconds into first stage flight, resulting in SpaceX’s first major failure since the loss of the third Falcon 1 launch.
The first stage was expected to fire for around 159 seconds before its engines shut down – with stage separation occurring four seconds later.
However, just prior to the point staging was to occur, visual issues were noticed with the vehicle during the live webcast, showing a problem potentially between the first and second stage.
The view was obscured by the failing rocket, prior to the vehicle being destroyed.
It was later revealed by SpaceX’s Elon Musk that there was an overpressure issue in the LOX tank of the second stage, which is the initial root cause of the loss of the vehicle.
A post failure press conference noted the review of the data was still ongoing.
The CRS-7 mission was to be Dragon’s ninth flight; the eighth to the ISS and the seventh under the Commercial Resupply Services (CRS) contract that NASA awarded to SpaceX in December 2008.
CRS initially called for twelve Dragon missions, along with eight flights of Orbital Sciences’ Cygnus vehicle; however SpaceX’s contribution has since been revised to fifteen flights. CRS followed on from the Commercial Orbital Transportation Services (COTS) program, under which the Dragon and Cygnus were initially developed.
First flown in December 2010, SpaceX’s Dragon became the first commercial spacecraft to visit the International Space Station when it berthed during its second and final COTS test flight, C2+, in May 2012.
In October 2012 the first operational CRS mission was conducted and since then Dragon has made regular visits to the ISS. Its most recent mission, CRS-6, launched in April and successfully concluded its mission five weeks later with splashdown in the Pacific Ocean.
Dragon is the only recoverable vehicle used for unmanned resupply missions to the space station, allowing it to return larger items of cargo from orbit to Earth.
The Dragon spacecraft consists of a pressurised capsule and an unpressurized Trunk section. Measuring 4.4 metres in length with a diameter of 3.7 metres (14 by 12 feet), the Dragon can carry up to 6.0 tonnes (5.9 imperial or 6.6 US tons) of cargo to the space station.
Twin solar arrays, mounted on the Trunk section, provide the spacecraft with power while eighteen Draco thrusters, each generating 400 newtons (90 pounds-force) of thrust, are used for attitude control and propulsion.
In addition to its usual cargo of food, supplies, scientific equipment and station hardware for the Expedition 44 crew aboard the ISS, CRS-7 was carrying the first International Docking Adaptor, IDA-1. A second adaptor is expected to launch with the CRS-9 mission at the end of the year.
Constructed by Boeing, the two IDAs represent NASA’s first steps towards developing a universal docking system.
Derived from the APAS-95 standard used by the Space Shuttle – itself an adaptation of the docking system built for the Soviet Union’s Buran spacecraft and a descendent of technology that was originally developed for the Apollo-Soyuz mission in 1975 – the IDA implements the International Docking System Standard (IDSS) through the Soft Impact Mating Attenuation Concept (SIMAC).
The IDAs are designed to be mounted on the existing Pressurized Mating Adapters (PMAs), attaching via the PMAs’ own APAS docking ports. IDA-1 was to be affixed to the PMA-2 adaptor which was launched aboard Space Shuttle Endeavour during the STS-88 mission in December 1998.
The first Shuttle mission to the International Space Station, STS-88 carried the Unity module and two PMAs – with PMA-1 being used to attach Unity to the station, which at the time of Endeavour’s arrival consisted solely of the Zarya module that had launched aboard a Proton-K rocket two weeks earlier.
PMA-2 was the primary docking port for the Space Shuttle, and is currently on the forward-facing side of the station’s Tranquility module.
The other IDA is set to be mounted on PMA-3. Delivered by Discovery during STS-92 in October 2000, PMA-3 served as the Shuttle’s backup docking port and has only been used twice; by Endeavour during STS-97, which delivered the first large section of the station’s truss structure, including the first set of US solar arrays; and by Atlantis during the next mission, STS-98, when the delivery of the Destiny module required that PMA-2 be uncoupled from the station and relocated.
IDA-1 was contained within the Dragon’s Trunk structure. Had Dragon safely berthed at the station, it would have been extracted using the CanadArm2 remote manipulator system and placed at the end of PMA-2.
The ISS are currently reviewing if they can work with one IDA – which would impact on a handover preference during commercial crew missions – or to aim to launch a replacement in the future.
Eight Flock-1 CubeSats were also being transported aboard the Dragon, for deployment from the Japanese Kibo module. The three-unit Flock-1f spacecraft were to form part of Planet Labs’ constellation of imaging satellites.
Flock satellites have previously been flown – as many as twenty eight at a time – aboard the CRS-5 and 6 Dragon missions, as well as Orbital Sciences’ CRS-1, 2, the unsuccessful CRS-3 mission and aboard a Russian Dnepr launch.
In total, 2,477 kilograms (6,461 lb) of cargo was aboard the Dragon, including provisions, care packages and food for the crew, hardware for the station’s healthcare, life support, electrical and computer systems, 529 kilograms (1,166 lb) of scientific hardware for NASA, ESA and JAXA and hardware for performing EVAs.
Dragon was expected to return 675 kilograms (1,488 lb) of cargo to Earth.
The research payloads that were onboard the CRS-7 included a JAXA experiment to investigate combustion in microgravity; a high resolution Earth-facing camera to watch for meteors entering the atmosphere in an attempt to study their compositions; Veg-03, a cabbage growth experiment; a bioscience investigation to study the effects of spaceflight on telomeres in the crew’s DNA and an array of student experiments.
All were lost, despite the Dragon falling clear of the failing Falcon 9. However, she was not designed to recover from such an incident and was lost when she impacted the water.
Dragon’s CRS-7 ill-fated mission began with a launch atop SpaceX’s Falcon 9 v1.1 rocket, flying in its partially reusable configuration to facilitate a further attempt at first stage recovery.
SpaceX’s was going to make a third attempt at a controlled landing atop one of its Autonomous Spaceport Drone Ship (ASDS) barges. Sunday’s mission was to mark the debut of a new barge named Of Course I Still Love You.
Like her sister barge, Just Read The Instructions, the new barge is named after a spacecraft in Iain M. Banks’ Culture series of science fiction novels. Just Read The Instructions appears to have been decommissioned as an ASDS, returning to service as a regular shipping barge.
The previous recovery attempts were made during the CRS-5 and CRS-6 missions earlier this year, with a planned attempt during the DSCOVR launch being called off due to rough seas. Both attempts to date have seen the first stage reach the barge but fail to perform a soft landing.
During the CRS-5 launch the vehicle ran out of hydraulic fluid on its final approach, impacting the barge on its side before exploding. On CRS-6 the stage toppled over as it came to rest and again exploded.
Once landings at sea have been perfected, SpaceX intend to begin recovering the first stages on land, using a new landing under construction on the site of Cape Canaveral’s Launch Complex 13 – a former Atlas-Agena launch pad.
The Falcon 9 was erected at Cape Canaveral’s Space Launch Complex 40 on Friday for its static fire test, which was conducted successfully marking the final major milestone before launch.
Launch operations began twenty eight hours ahead of liftoff with the Dragon being powered up. The Falcon was powered up ten hours in advance of liftoff, with fuelling operations underway around four hours and twenty minutes before liftoff.
The RP-1 propellant was loaded into the vehicle first, with the oxidiser – liquid oxygen – beginning tanking twenty minutes later.
By the ninety minute mark in the countdown loading was complete, however the liquid oxygen tanks continued to be topped up until the final minutes of the countdown as the cryogenic liquid boils off and is vented.
Beginning ten minutes before launch, the terminal countdown saw control of the countdown handed over to an automated sequence and the rocket’s computers.
Around four minutes and forty seconds before liftoff the Strongback, the structure used to transport the rocket to the launch pad, erect it and provide support while vertical, began to retract away from the Falcon.
The rocket’s Flight Termination System – or self-destruct – was placed on internal power three minutes and fifteen seconds before launch before being armed at around the three-minute mark.
Post failure notes are yet to clarify if the FTS was used during the Falcon 9 failure.
The final clearances for launch was given by the Launch Director two minutes and thirty seconds before liftoff and by the Range Control Officer half a minute later.
Sunday’s launch window was instantaneous, so any delay would have resulted in a scrub and at least a 24-hour turnaround.
In the last minute of the countdown the rocket performed its final prelaunch tests, the pad deluge system, or Niagara, was activated and at around the forty second mark the rocket’s propellant tanks were pressurised.
Ignition of the first stage’s nine Merlin-1D engines occurred three seconds before liftoff – with the launch marked when the count reached zero.
Ascending from the launch pad the rocket will erformed a series of manoeuvres to attain the correct azimuth for its target orbital inclination of 51.6 degrees. Passing through the sound barrier approximately 70 seconds after launch, Falcon encountered the area of maximum dynamic pressure, or Max-Q.
The countdown and launch were nominal. However, the mission ended just over two minutes into flight when the Falcon 9 suffered the failure resulting in the loss of the vehicle and mission.
Follow up articles will follow.
(Images: via L2, NASA and SpaceX)
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