“We were pretty naïve about that,” Mr. Musk said in July at a conference in Washington, D.C. “At first, it sounds really easy. Just stick two first stages on as strap-on boosters. How hard can that be? But then everything changes. All the loads change. Aerodynamics totally change. You’ve tripled the vibration and acoustics.”
The central core was redesigned and reinforced to handle the stresses, one of the key reasons that the Heavy is more than three years behind schedule. While the two side boosters are reused from earlier Falcon 9 launches, the core is all new, as is the second stage.
Another tricky aspect is the large number of rocket engines. A Falcon 9 booster has nine of SpaceX’s Merlin engines, each putting out 190,000 pounds of thrust. The Heavy triples that to 27 engines and a total of more than 5 million pounds of thrust.
All of the parts of the Heavy finally arrived in Florida late last year. Since then, SpaceX has been modifying the launchpad to handle the larger rocket. In the coming days, the company is expected to conduct a critical test that would light all 27 engines at once with the rocket anchored to the pad.
If the test flight succeeds, SpaceX has four additional Heavy launches on its manifest, including one for the United States Air Force. SpaceX also announced last year that a Heavy would be used to sling two space tourists on a weeklong trip around the moon, although it has offered no further information in almost a year.
Going big in an era of rockets on a diet
Some wonder how much business exists for a rocket as big as the Heavy. “I’ve always scratched my head, why would you do this?” said Jim Cantrell, who was part of the founding team of SpaceX in 2002 but left soon afterward. He is now chief executive of Vector, which is building rockets much smaller than SpaceX’.
With advances in electronics and miniaturization, satellites have been getting smaller, and the trend among rocket start-ups — has been toward smaller and smaller rockets. (Jeffrey P. Bezos’ Blue Origin is a notable exception.)
For $1.5 million, Vector will launch a 140-pound payload, with flights beginning this year. Other new companies aiming at small payloads include Rocket Lab, which over the weekend had its first successful orbital test flight, and Richard Branson’s Virgin Orbit.
“There’s pretty good financial and technical reasons for going smaller,” Mr. Cantrell said.
Some suggest that NASA could take advantage of the Falcon Heavy as a cheaper alternative to the Space Launch System it is developing to launch robotic probes and astronauts out into the solar system. Although the NASA rocket would be larger and more powerful than the Heavy — in fact it would rival the Saturn 5 — it is also much more expensive and would fly only once every few years at a cost likely to exceed $1 billion a launch.
The Trump administration has declared that sending astronauts back to the moon is a priority and has advocated a greater role in the space program for private companies. Its budget proposal for 2019, which will be released next month, should include more details of what it plans to do.
Charles Miller, a former NASA official who served in the Trump administration’s transition team, thinks the agency should consider turning to cheaper, commercial alternatives like the Falcon Heavy.
“It’s the core around which I would build a near-term return-to-the-moon strategy,” Mr. Miller said.