“Flight computers now in control of the vehicle…”
It is 2013. At first glance, the rocket about to fly from Space Launch Complex (SLC)-4E at Vandenberg Air Force Base in California looks strangely familiar, bearing some hallmarks of SpaceX’s Falcon 9, juxtaposed with a size and bulk more in keeping with United Launch Alliance’s Delta IV Heavy. It stands 227 feet tall and across the breadth of its trio of first-stage “cores” it measures 38 feet wide. Weighing 1,400 tons at liftoff, it can insert 120,000 pounds of payload into low-Earth orbit and propel as much as 26,000 pounds to higher geostationary altitudes. Taking into account its low-Earth orbit mandate, it falls into a category of rockets classed by NASA as “super-heavy-lift.” Its name: the Falcon Heavy.
“Standing by for the propellant tanks to flight pressure…First and second stages are pressing to their flight positions…”
Developed under the auspices of Elon Musk’s SpaceX organisation, the new booster is a direct outgrowth of the Falcon 9, which has to date despatched a pair of Dragon cargo ships toward the International Space Station. Like the Falcon 9, the Heavy boasts nine Merlin engines on its first stage. Yet the similarities stop there. Whereas the current Falcon 9 is powered by Merlin-1C engines, the Heavy will utilise the upgraded Merlin-1D, which underwent a full-flight-duration test-firing at SpaceX’s Rocket Development Facility in McGregor, Texas, in June 2012. Moreover, with two additional strap-on cores—each of which is also powered by nine Merlin-1Ds—the Heavy carries tremendous potential to execute missions into Earth orbit…and beyond.
“…T-minus 30 seconds…”
The Merlin-1D engine is fed by refined, rocket-grade kerosene (known as ‘RP-1’) and liquid oxygen and has a propulsive yield of over 1.1 million pounds at liftoff, effectively producing a 16-percent thrust increase at sea level over the Merlin-1C. It is also capable of throttling from 100 percent to 70 percent of rated performance during flight. Moreover, with an advertised 160:1 thrust-to-weight ratio, it promises to be one of the most efficient rocket engines ever built. In its first incarnation, the engine will replace the Merlin-1C on the Falcon 9—with a first launch in this new configuration anticipated sometime next year—but is expected to enter service as a Falcon Heavy powerplant at around the same time. In May 2011, Musk declared his intent for the first Falcon Heavy hardware to arrive at Vandenberg by the end of 2012, “with liftoff to follow soon thereafter” and added that “first launch from our Cape Canaveral launch complex is planned for late 2013 or 2014.”
“…T-minus 15 seconds…”
Concurrently, the Falcon 9 will also see its first use of the Merlin-1D engine. Present planning suggests that Flight 6 of the rocket—scheduled to launch next year, carrying a Canadian weather research and communications satellite into a highly elliptical low-Earth orbit—will be the first mission to utilise a full complement of Merlin-1Ds. Musk’s excitement for the new engine is evident. “This is another milestone in our efforts to push the boundaries of space technology,” he said earlier in the year. “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.” The nature of those “payloads” whets the appetite, for on paper the Heavy is reportedly 50 percent more powerful than the Delta IV Heavy—currently the most powerful US launch vehicle in active service—and only 50 percent less powerful than the Saturn V, which still retains first place as the most powerful rocket ever brought to operational status in human history.
“…Ten, nine, eight…”
Already, SpaceX is progressing toward making both the first and second stages of the Falcon 9 and Falcon Heavy fully reusable and capable of returning to their launch site under their own power for refurbishment and reuse. In time, Musk hopes that the vehicles and the new engine itself will offer a more reliable and flexible launch architecture, which could reduce the cost of delivering a pound of payload into low-Earth orbit to less than a thousand dollars. In fact, the Heavy received its first firm commercial booking last May, when Intelsat contracted with SpaceX to launch a major telecommunications satellite into geostationary orbit in 2015.
“…Seven, six, five…”
At the time of the Intelsat booking, Musk was unworried by the relative paucity of contracts for the Heavy, although October’s hairy Falcon 9 ascent to send the second Dragon to the International Space Station has inevitably given cause for concern. A fuel dome above one of the first-stage engines ruptured and, although the engine itself did not explode, the incident caused a pressure loss and enforced an automatic shutdown. This required the Merlin’s eight siblings to burn for longer to compensate for the thrust shortfall and demonstrated an advertised capability of the Falcon that it can recover from “engine-out” contingencies and still complete its primary mission. This is a capability which will serve the Heavy well on its own ambitious plate of future flights.
“…Four, three, two…”
At three seconds, a sheet-like flame flares out from the base of the Heavy. The Merlin-1D engines of all three cores will ignite, but until the propellant is expended in the strap-on boosters, the central core is expected to use little or none of its own load. The Heavy benefits from a unique “propellant crossfeed” mechanism, whereby fuel and oxidiser is fed to power most of the engines on the central core until the strap-on boosters are almost empty and close to burn-out and separation. In essence, this means that the central core can operate a full power throughout the opening minutes of the ascent and still be left with a full propellant load—as opposed to a partial load—after the strap-on boosters are gone. After the separation of the boosters, the first stage will continue the climb towards orbit under the impulse of its nine Merlin-1Ds. The Heavy’s second stage boasts one “vacuum” version of the Merlin-1D, which will insert the primary payload into orbit. On 30 September 2012, SpaceX successfully tested the ‘1D-Vac’ at its McGregor facility and Musk tweeted the news: “Now test-firing our most advanced engine, the Merlin-1D-Vac.”
Musk expects the Heavy to eventually operate from both Vandenberg’s SLC-4E and the Kennedy Space Center’s Complex 39, with perhaps ten launches per year of the new rocket. The nature of its missions—aside from launching Intelsats—are driven by Musk’s claim that it can ferry more payload to escape velocity than any other vehicle, save the Saturn V. He has made no secret of the fact that he intends to support human expeditions to Mars within the next two decades and just last year NASA’s Ames Research Center developed a concept for a low-cost mission to the Red Planet involving the Heavy and an uncrewed Dragon spacecraft, to be launched as early as 2018. This “Red Dragon” would drill into Mars’ soil in an effort to find the molecular bases for life.
In spite of its recent woes, the Falcon 9 and the Merlin engine have both amply demonstrated impressive capabilities, successfully delivering primary payloads into orbit and also delivering on pledges that they can recover from in-flight failures to still complete their primary missions. When one looks back at the history of SpaceX itself—founded only a decade ago, yet now bound into a $1.6 billion Commercial Resupply Services contract with NASA to supply the greatest engineering endeavour in human history—it is hard not to be left in awe. Musk is only a man, and SpaceX is only a company, and many other start-ups and plans and proposals in the past have failed. Yet there is something about Musk’s conviction that is both appealing and riveting. If SpaceX can recover from its October mishap and fly a near-perfect CRS-2 mission to the space station in March, then trial the Merlin-1D engine on a real mission a few months later, then launch the Heavy before the end of next year, it will silence many of its critics.
“…and Liftoff of the Falcon Heavy launch vehicle…”
Let the journey begin.