Riding the triumphant coattails of last month’s Dragon demo flight to the International Space Station – the Commercial Orbital Transportation Services (COTS) 2+ mission – SpaceX has successfully concluded a full-duration firing of its new Merlin 1D engine, destined for use aboard the Falcon 9 and Falcon Heavy vehicles. The test occurred at the company’s Rocket Development Facility in McGregor, Texas, ahead of current plans for the engine’s debut, sometime next year. The Merlin 1D is the newest version of a powerplant which has helped propel the dreams of entrepreneur Elon Musk’s company from its birth in 2002 to its present position as one of the world’s most promising providers of commercial cargo and crew services. As it burned hot and hard for 185 seconds, delivering an impressive 147,000 pounds of thrust, the Merlin 1D proved itself to carry great value for SpaceX’s ambition to confer full reusability on both the Falcon 9 and the forthcoming Falcon Heavy.
In its current guise, the Falcon 9 carries nine Merlin 1C engines in its first stage, fed by refined, rocket-grade kerosene (known as ‘RP-1’) and liquid oxygen, with a propulsive yield of over 1.1 million pounds at liftoff. The Merlin 1D upgrade produces a 16 percent thrust increase at sea level over its predecessor and is capable of throttling from 100 percent to 70 percent of rated performance. Moreover, with an advertised 160:1 thrust-to-weight ratio, it promises to be one of the most efficient rocket engines ever built. At the same time, it will maintain the structural and thermal margins necessary to transport human passengers safely into orbit.
Heritage-wise, it draws heavily upon the design of the Merlin 1C, under whose thrust the Falcon 9 first rose to orbit in June 2010, followed by the first Dragon test mission the following December and, most recently, last month’s docking flight to the space station. For his part, Elon Musk is confident that more efficient manufacturing processes – including the use of robotic construction techniques – will contribute to expanding the number of engines produced from eight per month to an eventual goal of 400 per year.
Video Credit: SpaceX
“This is another milestone in our efforts to push the boundaries of space technology,” Musk said. “With the Merlin 1D powering the Falcon 9 and Falcon Heavy rockets, SpaceX will be capable of carrying a full range of payloads to orbit.” If the nature of these payloads is exciting, then the potential for the rockets themselves also serves to whet the appetite. The giant Falcon Heavy – standing 227 feet tall and slated for its maiden launch in 2013 – will effectively comprise three Falcon 9 ‘cores’, each boasting nine Merlin 1D engines, to produce a colossal 3.8 million pounds of thrust and deliver a payload of up to 53 metric tons into low-Earth orbit. This capability reportedly makes it 50 percent more powerful than the Delta IV Heavy and only 50 percent less powerful than the Saturn V, which still holds first place as the most powerful rocket ever brought to operational status.
SpaceX also has its sights set on making both the Falcon 9 and the Falcon Heavy reusable. During the McGregor test, the Merlin 1D executed multiple engine restarts at target thrust levels and specific impulses, both of which are key requirements in the drive for reusability. Last September, Musk unveiled plans for the first and second stages of both rockets to be able to return to their launch site, under their own power, for refurbishment and reuse. He even went so far as to declare that he would “consider us to have failed” if this reusability went unachieved by SpaceX.
Musk’s plan encompasses a nominal launch and staging, whereupon the entire first stage would rotate through 180 degrees and three of its nine Merlin 1Ds would be restarted to boost it back towards a landing. Video simulations reveal that the first stage will touch down vertically on deployable landing legs. Meanwhile, the second stage will continue towards orbital insertion and, after releasing its payload, it too will perform a 180-degree about-turn, burning its engines for the return home. During its fiery descent back through the atmosphere, it will be protected from thermal extremes by a phenolic impregnated carbon ablator, akin to the one already trialled successfully by Dragon.
In his September 2011 remarks to the National Press Club, Musk declared his conviction that such reusability would have a profound impact upon reducing launch costs. “If you look at the cost of a Falcon 9 rocket – which is a big, one-million-pounds-of-thrust rocket, yet the lowest-cost rocket in the world – it’s still $50-60 million,” he said, “but if you look at the cost of the fuel and oxygen and so forth, it’s only about $200,000. Obviously, if we can reuse the rocket, say, one thousand times, then that would make the capital cost of the rocket, per launch, only about $50,000.” To press his point, Musk compared it to a Boeing 747, which costs several hundred million dollars to build, but whose inherent reusability ultimately brings down the cost to fare-paying passengers to a “relatively small” figure that covers little more than “fuel, pilots and incidentals”.
The success of the Merlin 1D test has removed another obstacle on the road to an increasingly more reliable and flexible launch architecture; one which Musk believes could eventually reduce the cost of delivering a pound of payload to low-Earth orbit to a thousand dollars or less. In the meantime, hardware for the first Falcon Heavy is due to arrive at Vandenberg Air Force Base in California before the end of 2012 and the first complement of Merlin 1Ds will probably fly on Falcon 9 Flight 6, early next year.
SpaceX also appears unruffled by the relative paucity of firm customer bookings for the Falcon Heavy. Certainly, its growing public image and success rate is paying dividends; in the wake of the Dragon mission to the International Space Station, the company’s value doubled to approximately $4.8 billion. Only last month, a few days after the Dragon launch, Intelsat became the Falcon Heavy’s first customer and the booster will loft a major telecommunications satellite to geostationary orbit.
In the meantime, a tentative launch date of 5 October has been set for the first ‘real’ Dragon cargo flight to the International Space Station. With the flight of ‘SpX-1’ – conducted under the requirements of the $1.6 billion Commercial Resupply Services contract, signed between SpaceX and NASA in December 2008 – the company will begin the first of a dozen such cargo delivery missions between 2012 and 2015. Parallel to these efforts are dozens of other commercial satellite launches and Musk hopes to conduct the first manned voyage of the DragonRider crew capsule by 2015 and perhaps a Mars sample return mission at some point thereafter. He has made it clear that the company’s eventual goal is to establish a permanent human presence on Mars. A few years ago, such an outlandish proposal would have been laughable; indeed, to a great extent, it still is. Yet the dramatic strides taken by SpaceX in such a short span of time are now causing many observers to wonder.