SpaceX made a fourth – and successful – attempt to launch its Falcon 9 v1.1 – tasked with orbiting six OG2 satellites for Orbcomm’s second generation constellation – on Monday. The latest attempt – from Space Launch Complex 40 (SLC-40) at Cape Canaveral – launched at 11:15 am local time, following a slight delay due to Ground Support Equipment (GSE) issue.
Falcon 9 v1.1 Mission:
SpaceX’s first Orbcomm launch consisted of a single satellite deployed as a secondary payload to the CRS-1 Dragon mission to the ISS in October 2012.
This ended in failure after a first stage engine malfunction left the rocket unable to reach the Orbcomm’s designated deployment orbit, despite unloading its Dragon payload successfully.
As a result the satellite was left in an unusable orbit from which it quickly decayed, unable to fulfil its mission. This anomaly, overall a partial failure, remains the only blemish on the Falcon 9’s launch record.
Eighteen Orbcomm Generation 2 (OG2) satellites have been produced; of these one was lost in the 2012 failure, six are aboard this launch, with the remaining eleven expected to fly together aboard a single Falcon 9 later this year.
Orbcomm has options for up to thirty more satellites which can be produced for replenishment or to increase the size of the constellation should it be necessary.
The prime contractor for the program is the Sierra Nevada Corporation, with Argon ST of Virginia producing their communications subsystems.
Each spacecraft is based on Sierra Nevada’s SN-100A bus, with a mass of 172 kilograms (380 lb) and is designed for an operational lifespan of at least five years. The spacecraft are each powered by a gallium-arsenide solar panel producing 400 watts of electrical power.
Each OG2 spacecraft is three-axis stabilised with hydrazine thrusters used for attitude control.
The satellites’ communications systems offer transfer rates up to four megabits per second at VHF frequencies between 137 and 153 megahertz, with each vehicle also carrying an Automatic Identification System (AIS) receiver to pick up identification and tracking signals broadcast by ships at sea – Orbcomm intends to sell this data to coastguard services.
The second-generation constellation is expected to increase the capacity of the Orbcomm network six to twelve times over.
Not including this launch, forty seven Orbcomm spacecraft have been launched to date, with the first being the Orbcomm-X spacecraft which was deployed by an Ariane 4 in July 1991.
A technology demonstrator for the remainder of the constellation, no signals from the spacecraft were ever received. Two further demonstration launches occurred in 1993, followed by the first two operational satellites in April 1995.
The majority of the first-generation satellites were deployed in cluster launches which made use of Orbital Sciences’ Pegasus-XL rocket.
Three groups of eight satellites and one group of seven were launched between 1997 and 1999, with two more spacecraft flying atop a Taurus in 1998.
The original satellites were designed to operate for four years, however it was not until 2008 that a replenishment launch took place, with a Russian Kosmos-3M carrying five Orbcomm Quick Launch satellites and the CDS-3 technology demonstrator.
Most of these satellites failed within a year of the launch due to problems with their attitude control systems, while those that were not rendered completely unusable could not be used to their full capacity, and within two years all six spacecraft were unserviceable.
Orbcomm was forced to lease two VesselSat satellites from LuxSpace to provide interim capacity; these spacecraft were launched in October 2011 and January 2012.
This launch was conducted by the Space Exploration Technologies Corporation, better known as SpaceX.
The company was initially awarded a contract to launch the eighteen OG2 satellites in 2009, using its smaller Falcon 1 rocket. Expected to use the enhanced Falcon 1e configuration, which ultimately never flew, the satellites were transferred to Falcon 9 launches after SpaceX opted to withdraw the Falcon 1 from service.
The Falcon 1 had been SpaceX’s first rocket. The vehicle’s first three launches, in 2006, 2007 and 2008 all failed, however after a successful demonstration launch in September 2008, Malaysia’s RazakSat satellite was deployed in 2009 by what would turn out to be the final Falcon 1 launch.
While SpaceX initially attempted to develop the stretched and re-engined Falcon 1e, this was quickly abandoned in favour of launching more satellites as secondary payloads aboard the Falcon 9.
Falcon 9 launches at Cape Canaveral take place from a former Titan launch pad, Space Launch Complex 40 (SLC-40). The pad was built in the 1960s for the Titan III, and served Titan IIIC, III(34)D and IV launches until the final Titan launch from the Cape in 2005.
Following the demolition of the Titan service towers in 2008, SpaceX began to convert SLC-40 to a clean pad for its rocket. The first Falcon 9 went vertical at the pad in January 2009, however it was not until June 2010 that the type made its maiden flight with the deployment of the Dragon Spacecraft Qualification Unit, a “boilerplate” mockup of the Dragon spacecraft which later flights were expected to carry.
In December 2010 the Falcon 9’s second launch carried the first functional Dragon spacecraft, which completed two orbits of the Earth before being deorbited and recovered successfully.
The next three launches carried Dragon missions which resupplied the International Space Station; the first a test, with the next two as operational flights.
The first five Falcon 9 launches used a configuration which has become known retrospectively as the v1.0. In September 2013 it was replaced with the more powerful v1.1 configuration, which stretched both stages, reorganised the first stage engines into an octagonal arrangement rather than the square used on earlier missions and upgraded those engines from the Merlin-1C to 1D specification.
California’s Vandenberg Air Force Base was the scene of the v1.1’s maiden flight – this remains the only Falcon 9 mission to date not to originate from Cape Canaveral.
After a successful launch that deployed the CASSIOPE satellite for Canada, the Falcon 9 was cleared for commercial geostationary launches; deploying Luxembourg’s SES-8 in December 2013 and Thailand’s Thaicom 6 in January 2014.
The rocket’s most recent launch deployed another Dragon mission to the ISS, marking the first launch for the Dragon atop a Falcon 9 v1.1.
Intended to eventually allow spent stages to be recovered and potentially reused, these legs once again featured on this launch.
Early reports note the stage returned for a propulsive splashdown, but suffered a structural failure as it was hitting the water and was destroyed.
On the Dragon mission SpaceX were able to demonstrate controlled flight up until the stage reached the ocean, and it is hoped that this launch will bring SpaceX a step closer to being able to attempt a land recovery. For this mission, however, the stage is expected to land in the sea.
A two-stage rocket, the Falcon 9 burns RP-1 propellant, oxidised by liquid oxygen, in both of its stages. The first stage is powered by nine Merlin-1D engines, while a vacuum-optimised version of the Merlin-1D propels the second stage.
The rocket is named after the Millennium Falcon spacecraft in the Star Wars films.
In preparation for launch, the Falcon 9 went through powerup procedures, which occurred thirteen and a half hours before the beginning of the launch window.
Controllers began final preparations for the vehicle’s launch, with fuelling starting around three hours and fifty minutes before liftoff with oxidiser tanking, while propellant loading began ten minutes later.
By the three hour, 15-minute mark this was complete apart from continual replenishment of the oxygen throughout the count as it boils off.
At T-10 minutes the automated sequence took over control of the countdown.
Controllers then entered the terminal count, with the rocket transferred to internal power at the six minute mark in the countdown.
Following this, the ‘strongback’ structure used to transport it to the pad, erect it and support umbilicals was retracted; occurring between five and four minutes ahead of the liftoff.
At around T-3 minutes, thirty seconds the flight termination system – the self-destruct system used to ensure that the rocket cannot inadvertently hit a populated area if it goes out of control during ascent – was transferred to internal power and subsequently armed.
The launch director confirmed the rocket was go’ for launch at the two and a half minute mark, with the range control officer confirming that he was ready to proceed thirty seconds later.
One minute before launch the vehicle began its startup sequence and its fuel tanks were pressurised. Also around this time the pad’s water deluge system was turned on to protect the complex from the Falcon’s engine exhausts.
The nine first stage engines ignited about two seconds ahead of the rocket lifting off, giving time to ensure they have started correctly before the rocket was released.
About a minute after launch the rocket was travelling at the speed of sound, Mach 1, with the rocket passing through the area of maximum dynamic pressure, max-Q, about fifteen seconds later.
The first stage engines burned for two minutes and 38 seconds, with the spent stage separating around three seconds after the burn is complete. Following a further eight second coast the second stage engine was ignited.
The payload fairing, which protects the satellites from the atmosphere during ascent, separated from the nose of the rocket around the forty-five seconds after ignition.
Second stage flight lasted six minutes and 46 seconds, and its conclusion marked the end of powered flight nine minutes and 39 seconds after liftoff.
Deployment of the six OG2 satellites will begin approximately five minutes later.
The satellites are attached to the rocket by means of two EELV Secondary Payload Adaptors (ESPAs), devices which were developed by Moog Incorporated to allow Atlas V and Delta IV rockets to carry six additional payloads mounted below their primary passenger.
Instead for the Orbcomm launch the ESPA has been modified so as to only carry four satellites, with two fitted together to provide eight slots.
Mass simulators have been bolted to the two unused slots either side of the lower ESPA.
The Falcon 9’s target orbital parameters are a perigee of 615 kilometres (382 statute miles, 332 nautical miles), an apogee of 750 kilometres (466 miles, 405 nautical miles) and inclination of 52 degrees. It appears SpaceX were well within the parameters.
Monday’s attempt was approved following last week’s Static Fire test, that proved to be successful, and was subsiquently rubber stamped by the Launch Readiness Review (LRR) on Sunday morning.
This was the fourth attempt, with the vehicle getting past a number of issues, one of which related to the problem surrounding the rocket’s helium pressurization system that scrubbed a previous Static Fire.
Notably, that previous test allowed SpaceX to attempt to launch this Falcon 9 v1.1 last month. However, following a second stage issue on the first attempt and a weather scrub on the second, the following day brought up another hardware issue.
While the attempt was a long shot – based on the poor weather throughout what was an extended launch window – a problem with what was described by L2 sources as a TVC actuator on the rocket’s first stage was classed as a “potential concern”, resulting in a scrub being called for the day.
With another element coming into play – namely the Eastern Range and its requirement for a maintenance period – SpaceX decided it would be prudent to realign the launch into July.
This launch was the third Falcon 9 launch of the year, with the rocket’s next launch slated to take place in August with the AsiaSat-8 communications satellite.
For the United States, the Falcon launch is the country’s twelfth launch of the year.
It follows the Delta II that made its first flight since 2011 when it orbited the OCO-2 satellite for NASA, and Sunday’s Antares-120 that successfully sent next Cygnus mission on its way to resupply the International Space Station.
(Images: via L2′s SpaceX section, now containing thousands of unreleased photos of all Dragon missions to the ISS. Other images via Jacques van Oene/Spacepatches.nl, SpaceX Orbital and NASA).
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