Vehicle Configurations

Vehicle Components

Dot-com multimillionaire Elon Musk established SpaceX Corporation in June 2002 in an El Segundo, California warehouse, intent on developing the small "Falcon" launch vehicle and the rocket engines to power it.  By early 2003, the company was testing early prototypes of its 40-tonne-thrust-class Merlin first stage engine and 3.17 tonne thrust Kestrel second stage engine at its McGregor, Texas test site. 

Merlin was a gas generator cycle engine that used a pintle style injector, an injector design adapted from the Apollo Lunar Module engine.  Turbopump exhaust provided roll control.  The engine had an ablatively cooled thrust chamber and nozzle. 

Kestrel, which also used a pintle injector, was a pressure fed design.  Kestrel had a radiatively cooled Niobium nozzle and an ablatively cooled chamber and throat. 
 

Enter Falcon 5

On December 3, 2003 in Washington D.C., during its Falcon "protovehicle" unveiling ceremonies, Elon Musk announced that SpaceX planned to follow-up Falcon (thereafter called "Falcon 1") with a more powerful 3.7 meter diameter launch vehicle named "Falcon 5" that would  be capable of hauling 4.2 tonnes to low earth orbit (LEO) and 1.25 tonnes to geosynchronous transfer orbit (GTO).  Falcon 5 launches would be priced at $12 million.

Falcon 5 would stand about 29 meters tall and weigh about 130 tonnes at liftoff.  Its first stage would be powered by five Merlin engines producing a total of 162.13 tonnes of thrust at liftoff and 192 tonnes in vacuum.   Two upgraded Kestrel engines would boost the second stage, producing nearly 6.8 tonnes of total thrust.  Like Falcon 1, Falcon 5 would usa a "pressure assisted stabilized" graduated monocoque friction stir-welded aluminum design with a common bulkhead between its aft kerosene tank and its forward liquid oxygen tank.  Both stages would be helium pressurized and would be designed to be recovered at sea after floating down beneath parachutes.   SpaceX hoped to recover parts of the stages for reuse. 

Musk also described a concept for a follow-on Falcon 5 equipped with more powerful Merlin engines, producing 227 tonnes of liftoff thrust.  This Falcon 5 would be fitted with a liquid hydrogen second stage powered by one or more RL10 engines.  It would be able to lift about 9 tonnes to LEO and 4.5 tonnes to GTO.

At the ceremony, Elon described goals that seem hopelessly optimistic in retrospect.  He expected to fly the first Falcon 5 in November 2005 and to launch six Falcon 1 and four to six Falcon 5 missions per year by 2010 from still-to-be-developed launch sites at Cape Canaveral, Vandenberg, and Omelek Island at Kwajalein Atoll in the Marshall Islands.

Development realities intervened during 2004, when SpaceX struggled with Merlin development.  Cast aluminum manifolds cracked during tests, requiring replacement with heavier inconel manifolds.  The engines were not quite as efficient as planned, requiring thrust to be increased to offset the lower specific impulse.  Merlin had to be redesigned and retested, a process that extended through the year.   

By late 2004, SpaceX listed a launch schedule that included a Falcon 5 launch of a test payload for Bigelow Aerospace.  By then the Falcon 5 design had been beefed up to haul 6 tonnes to LEO.  Higher thrust "Merlin 1B" engines were now assigned to power the first stage, producing nearly 193 tonnes of liftoff thrust, and a single Merlin replaced the Kestrel pair on the second stage.  The second stage Merlin would use a large nozzle extension to increase specific impulse to as high as 340 seconds in vacuum.  This was a Delta II category launch vehicle design.  
 
Falcon 9 Announced

During 2005, SpaceX began Falcon 5 fabrication and development.  Plans called for 12 Merlin 1B engines to be completed during the year, but in September 2005, the plans changed.  SpaceX announced that it would develop "Falcon 9", powered by nine Merlin 1B first stage engines, to meet the needs of an unnamed government customer.   Falcon 9 would be able to boost more than 9 tonnes to LEO or more than 3 tonnes to geosynchronous transfer orbit (GTO) for $27 million.  Even more powerful versions, with parallel Falcon booster strap-ons, were projected for the future.  Falcon 9S5 would use two Falcon 5 strap-on boosters.  Falcon 9S9 would use two Falcon 9 strap-on boosters.  No longer a Delta II class launch vehicle, Falcon 9 entered the EELV payload category.

The Falcon 5 design was changed yet again, becoming a partially loaded Falcon 9 stripped down to only 5 Merlin first stage engines.  The change meant that Falcon 5's LEO payload fell to 4 tonnes while its price rose to $18 million.

The first Falcon 1 launch campaign at Omelek extended through the final months of 2005 into the early months of 2006, culminating with an inaugural flight failure on March 24, 2006.  SpaceX spent much of 2006 evaluating, and recovering from, the failure.  

Dragon, NASA COTS, and Merlin 1C

In September, 2006, SpaceX won one of two NASA Commercial Orbital Transportation Services contracts. The $278 million award was for three flight demonstrations by SpaceX of its to-be-developed 7 tonne "Dragon" spacecraft on Falcon 9 launch vehicles.  The launches, planned at the time to begin in late 2008, would demonstrate Dragon's ability to haul 3.1 tonnes of cargo to the International Space Station (ISS) and to return cargo to Earth.

During 2006, Elon Musk also announced that SpaceX had decided to begin work on a "Merlin 1C" engine with a regeneratively cooled thrust chamber.  In early February 2007, SpaceX updated its web site with revised design information for both Merlin and Falcon.  The data was said to be effective for vehicles launched in 2009 or later.  Merlin 1C was shown to produce 46.259 tonnes of sea-level thrust - a 32% increase over the thrust produced by Merlin during the initial Falcon 1 launches.  Falcon 9 was shown using nine Merlin 1C engines, providing a 20% thrust increase over the previously announced Merlin 1B engines. 

By the time a revised Payload User's Guide was published in May 2007, Falcon 5 had disappeared from the company's catalog altogether.  Falcon 9 and Falcon 9S9 (now called Falcon 9 Heavy) payloads had grown by more than 10% from earlier specifications. 

The second Falcon 1 failed on March 21, 2007, a victim of second stage propellant sloshing that caused loss of flight control about 5 minutes after liftoff.  While the company labored to learn more lessons from its little Falcon, it forged ahead with Falcon 9 development and fabrication. 

Cape Canaveral Launch Site Selection

In April 2007, SpaceX signed an agreement to lease Cape Canaveral Space Launch Complex 40, a mothballed Titan IV pad, for five years for Falcon 9 launches.  The original agreement included use of the ex-Titan IVB SMARF high bay for Falcon 9 integration, but the company subsequently decided to build a smaller horizontal integration hanger near the launch pad itself.  The Titan IV umbilical tower was removed as a first step.  On April 27, 2008, the massive Titan IV mobile service tower, once called the world's largest moving object, was taken down with demolition charges.   SpaceX planned to use the Titan IV exhaust duct, lightning towers, and other structures, but Falcon 9 processing would use a "clean" pad without use of a large mobile tower.

Meanwhile, in October 2007, SpaceX moved from El Segundo to a larger (51,000 square meter) facility in Hawthorne, California.  Vought Aircraft had formerly used the site to fabricate 747 fuselages for Boeing.  SpaceX planned to employ 400 at the site, along with 50 in Texas and elsewhere.     

Falcon 9 Testing Begins  

On November 12, 2007, SpaceX announced that it had completed Merlin 1C engine development with a 170 second hot fire test at its Texas Test Facility near McGregor, Texas.  The development engine test program included 125 hot fire tests totaling more than 3,000 seconds duration.  This first Merlin 1C could produce 43 tonnes of thrust at sea level and 49 tonnes in vacuum. 

SpaceX shipped its first Falcon 9 first stage to McGregor in mid-2007.  The stage was erected into the company's massive Big Falcon Test Stand during August.  During November, 2007 the first Falcon 9 hot fire test, using only one Merlin 1C engine, was performed.  This was followed by a two engine test in January 2008 and a three-engine test in early March, 2008.  Five engine testing occurred in late May, 2008.  The first nine engine test was performed on June 31, 2008, in a test that produced 385.5 tonnes of total thrust.  Two more less-than-full-duration 9-engine tests followed.

On November 23, 2008, SpaceX performed the first full-duration nine-engine Falcon 9 test at McGregor.  Producing 387.8 tonnes of total thrust while burning nearly 227 tonnes of propellant, the burn lasted 178 seconds. Two of the nine Merlin 1C engines shut down as planned after 160 seconds, a sequence that mimicked the planned flight shutdown method.  The late-evening test startled Central Texas residents more than 20 miles away.    

Testing at McGregor used a battleship-type "run tank".  After the full duration test, SpaceX planned to remove the "run tank" and send its engines to Cape Canaveral, where the first Falcon 9 flight stage was expected to arrive by the end of 2008.  That flight stage was expected to be used for facility testing at SLC 40, culminating in a static test firing in early 2009.   Another flight stage was expected to arrive at McGregor for formal qualification testing.  One of these stages would presumably perform the inaugural Falcon 9 launch sometime in 2009.

New Falcon Details Emerge

In April 2008, SpaceX revealed new details for the higher-thrust Merlin 1C that would power both Falcon 1e and a "Block 2" version of Falcon 9 that would fly in 2010 or later.  The upgraded Merlin 1C would produce 56.69 tonnes of sea-level thrust and 63.45 tonnes of thrust in vacuum, 1.5-1.6 times more than the original Merlin.  With more available liftoff thrust, Falcon 1e and Falcon 9, Block 2 both grew substantially heavier and more capable. 

The Block 2 Falcon 9 would be able to lift nearly 10.5 tonnes to LEO from Cape Canaveral and 4.54 tonnes to a 28.5 deg GTO.  Stage recovery attempts were planned when lighter payloads were launched, with unused payload mass apparently assigned to recovery hardware.  Block 1 Falcon 9, powered by the initial lower-thrust Merlin 1C engines, would perform the early COTS Demonstration flights.  

CRS Contract

On December 23, 2008, SpaceX won a $1.6 billion Commercial Resupply Services (CRS) contract to haul NASA cargo to the International Space Station.   The contract covered 12 missions planned to fly between 2010 and 2016.  SpaceX would use its Dragon spacecraft to perform the missions.

Cape Canaveral Validation

During the final days of 2008, SpaceX shipped its first Falcon 9 to Cape Canaveral SLC 40, along with the Falcon 9 launch stand and launch vehicle erector.  The launch vehicle, which SpaceX said included some flight components, was shipped in pieces on a series of trucks from Hawthorne, California.  The propulsion section used for the November 23, 2008 full-duration "run tank" test in Texas was also trucked to Florida, with all nine Merlin 1C engines installed, and attached to the Falcon 9 first stage.  The entire vehicle, with a satellite payload fairing, was assembled near the launch pad, in the open, using rented cranes, by the end of the year.  The launch mount and erector were also assembled.  The SLC 40 Falcon 9 hanger had not yet been completed.  Initial efforts appeared to be focused on mechanical fit-checks.

Merlin Vacuum Certification

On March 7, 2009, SpaceX performed a full mission duration firing of the new Merlin Vacuum engine at McGregor.  The engine fired for six minutes, consumed 45.36 tonnes of propellant, and demonstrated a vacuum specific impulse of 342 seconds, highest ever for a U.S. hydrocarbon rocket engine.  The engine produced 41.96 tonnes of thrust in vacuum conditions. 

The Merlin Vacuum engine is based on the Merlin 1C, but is fitted with a larger exhaust nozzle and an added radiatively cooled expansion nozzle attachment.  It has demonstrated throttling down to 75%, with plans to test down to 60% throttling.

First Flight Vehicle Acceptance Testing

During 2009 and early 2010, the first Falcon 9 flight vehicle stages were acceptance tested at McGregor.  Structural acceptance testing of both stages was completed by October 5, 2009.  The first stage was test fired for 10 seconds on October 12 and for 30 seconds on October 16, completing its testing program.   The stage was shipped to Cape Canaveral during November, 2009. 

The second stage was test fired in a second, smaller McGregor test stand for 40 seconds during November.  On January 2, 2010, the Falcon 9 second stage completed a full duration mission firing, its Merlin Vacuum engine producing 41.96 tonnes of thrust for 329 seconds.  The stage was shipped to the Cape, where it arrived on January 29, 2010.  There, it joined the first stage in the new SpaceX SLC 40 horizontal integration hanger.



Inaugural Launch Campaign

SpaceX assembled its first flight Falcon 9 at Cape Canaveral SLC 40 during February, 2010.  The rocket was powered up and put through an integrated systems test before being rolled out to its pad on February 20.  On February 26, the rocket was loaded with propellant during its first wet dress rehersal countdown. 

The rocket performed a 3.5 second "hot fire" static test on March 13, 2010, during which the nine Merlin 1C first stage engines ignited and ramped up to full thrust.  The successful test took place four days after the initial attempt had been scrubbed only two seconds before ignition.  The scrubbed test identified a problem with the launch sequencer, which failed to issue a command to open a ground helium valve.

SpaceX Falcon 9 Inaugural Launch (Updated June 9, 2010)

The first SpaceX Falcon 9 two-stage kerosene rocket launched from Cape Canaveral on June 4, 2010.   Liftoff from Space Launch Complex 40 occurred at 18:45 UTC.    The rocket carried a Dragon spacecraft simulator toward a planned 250 km x 34.4 deg low earth orbit. 

Falcon 9's nine Merlin first stage engines developed 387.825 tonnes of liftoff thrust to slowly lift the 320-333 tonne, 47 meter tall rocket off its launch platform.  The rocket rolled slightly immediately after liftoff, but steadied itself as it cleared the pad.  Falcon 9 then flew smoothly through its initial ascent and pitch profile as it projected a thunderous roar back down onto observers at the Cape and Kennedy Space Center. 

The center two Merlin engines shut down as planned about 165 seconds into the flight.  The remaining first stage engines cut off at about 181 seconds.

Staging and second stage engine start - the first in-space start of a Merlin engine - appeared nominal, but a roll developed during the five minute long burn of the second stage Merlin Vacuum engine.  It was not clear if the roll had any effect on velocity performance.  The roll began about 5 minutes after liftoff, after the turbopump exhaust nozzle stopped vectoring.  Merlin shut down about 517 to 524 seconds after liftoff, just as the stage completed its fourth roll.  The stage was rolling about three times per minute at second stage engine cutoff. 

SpaceX claimed that the stage and payload had reached orbital parameters very close to the planned orbit, but initial U.S. orbital tracking data showed a less precise, 235 x 276 km x 34.5 deg orbit.  Subsequent tracking showed the stage in a 242 x 269 km x 34.5 deg orbit. 

During a teleconference after the launch, Elon Musk of SpaceX stated that the second stage Merlin Vacuum engine had performed a brief "burp" restart during its first orbit as an engineering test, but provided no details of the burn.  Later reports suggested that an attempted restart had failed shortly before the stage passed over Australia. 

Observers in eastern Australia saw the stage pass overhead about 65 minutes after liftoff.  Video of the pass showed that the stage was still rolling out of control, venting gas to form a spiral pattern.  The observations raised questions about whether the second stage on-board cold-gas three-axis control system had either failed or if an operational system was even flown during this test.  

The stage and its attached Dragon simulator were tracked until they reentered the Earth's atmosphere on June 27, 2010.

Falcon 9 No. 1 produced more thrust at liftoff than any U.S.-powered kerosene-fueled rocket since Saturn IB SA-210 carried the Apollo Soyuz Test Project spacecraft with three crew into orbit on July 17, 1975.  Merlin Vacuum performed the first U.S. turbopump-fed kerosene engine air-start since the last Titan I ICBM flew in 1965.

Falcon 9 Orbits Dragon C1

The second SpaceX Falcon 9 successfully boosted the company's Dragon C1 spacecraft into orbit from Cape Canaveral on December 8, 2010.  The two-stage, 313 tonne, kerosene/LOX rocket thundered aloft off from Space Launch Complex 40 at 15:43 UTC.  After a nearly nine-minute propulsion phase and a 20 second coast, Dragon C1 separated from Falcon 9's second stage, leaving its aft "trunk" section attached to the stage on this test flight, into a reported 288 x 301 km x 34.53 deg orbit, beginning a test flight planned for at least two orbits.  

Dragon subsequently completed two orbits, demonstrating active flight control through use of its 18 Draco thrusters.  According to some reports, one Draco failed to function, but redundancy in the flight control system design allowed the flight to continue.  Elon Musk himself said after the flight that all thrusters worked.  After two orbits, Dragon fired four Dracos beginning at about 18:17 UTC to initiate reentry.  The capsule reentered over the Pacific Ocean and splashed down at about 19:02 UTC beneath three parachutes about 800 km off the northwest coast of Mexico.  

Dragon C1 was the first SpaceX flight for NASA's Commercial Orbital Transportation Services (COTS) contract.  It was the first spacecraft successfully launched and recovered from orbit by a commercial company.  Only countries - the United States, Russia, China, Japan, India, and the European Space Agency  - have previously performed the feat.

After Dragon deployed, several "CubeSat" microsatellites were released into low Earth orbit, likely from the Dragon trunk section that remained attached to the top of the orbiting Falcon 9 second stage on this test mission.  One flew for the Naval Research Laboratory.   Another, the first U.S. Army built satellite in more than 50 years, was identified as the Space and Missile Defense Command - Operational Nanosatellite Effect, or SMDC-ONE.

After the flight, CEO and Chief Engineer Elon Musk announced that the second stage Merlin Vacuum engine had successfully restarted in a test, propelling the stage to a 288 x 11,083 km x 34.6 deg elliptical orbit.  The first stage was not recovered, but telemetry of the stage reentry was recovered through use of a data pod. 
 

Merlin 1D, Falcon Heavy, and the future of Falcon 9

On April 5, 2011, SpaceX announced that it would develop a triple-body Falcon Heavy powered by an upgraded engine named Merlin 1D.   Each of the rocket's 27 Merlin 1D engines would produce 63.5 tonnes thrust at sea level, nearly 1.5 times more than the Merlin 1C engines that powered the first two Falcon 9 rockets.  Using the new engines, combined with propellant crossfeeding from the twin boosters to the central core, Falcon Heavy would be able to lift a surprising 53 tonnes to LEO, 19 tonnes to GTO, or 13.6 tonnes toward Mars.  Plans called for the first Falcon Heavy to fly a demonstration mission in 2013 from Vandenberg AFB Space Launch Complex 4 East, the former Titan 4 pad. 

SpaceX also divulged plans for a two-stage Falcon 9 powered by nine Merlin 1D engines.  This Falcon 9, substantially more capable than either Falcon 9 Block 1 or Block 2, would be able to lift 16 tonnes to LEO or 5 tonnes to GTO, would stand 69.2 meters, and would weigh 480 tonnes at liftoff.  The company continued to show Falcon 9 Block 2 as the baseline in its Payload Users Guide. 

On April 25, 2011, Elon Musk, in a Space News interview, confirmed that Falcon Heavy would use a "stretched" Falcon 9 stage augmented by two additional "first stages".  He stated that Merlin 1D would fly in mid-2012 on a Falcon 9 mission, most likely on the seventh flight of the rocket.   Mr. Musk described how the Merlin 1D combustion chamber is being explosively formed, streamlining the production process.  He noted that a fully integrated Merlin 1D was already being test-fired. 

During the August 2011 Joint Propulsion Conference, SpaceX VP of Propulsion Tom Mueller said that the Merlin 1D test engine had demonstrated a thrust to weight ratio greater than 160:1 and a vacuum specific impulse greater than 309 seconds. 

Design details of Falcon Heavy, and of Merlin 1D performance, have not been divulged.  In order to achieve the payload capability claimed by SpaceX, the new rocket engine will have to provide improved specific impulse and the stages will have to provide very high propellant mass ratios.  SpaceX claimed that the two "first stage" strap-on units will achieve a 30 to 1 gross mass to dry mass ratio, implying an unprecedented propellant mass fraction of better than 0.966.

One possible approach for growing Falcon 9 could be to stretch the Block 1 first stage, while keeping the Block 1 second stage, to create Block 2.  The next step could be to stretch the second stage, while leaving the Block 2 first stage unchanged, to create Block 3.  SpaceX has not announced whether it intends to use such an approach.   

Vehicle Configurations

Vehicle Components

References

Falcon 9 Data Sheet, SpaceX, 2008
Falcon 9 Users Guide, SpaceX, 2009
Falcon Family Brochure, SpaceX, 2011
Updates at www.spacex.com
Tom Mueller (SpaceX VP) comments at August 2011 Joint Propulsion Conference

Last Update:  August 6, 2011