|Why the SpaceX Falcon Heavy Rocket Just Might Work|
If Elon Musk wants to get to Mars, SpaceX will have to combine three rockets into one mammoth engine. Will it work? An expert weighs in.
By Bobak Ferdowsi
Jul 31, 2017
SpaceX CEO Elon Musk has made it pretty clear he wants to die on Mars (just not on impact!). He believes we should be a multi-planetary species, and SpaceX has been marching toward that goal since its founding in 2002. Every new rocket engine, every launch, every trip to the International Space Station is not just a business transaction but also an opportunity to upgrade SpaceX's engineering savvy and expand its portfolio of launch capabilities. Because before Elon can retire overlooking Olympus Mons, the company is going to need to get a lot of people and payload into space. That's why, before the year is out, they hope to launch what will be the most powerful rocket on the planet: the Falcon Heavy. It will be a challenge unlike any yet faced in the era of private spaceflight. Can the team at SpaceX pull it off?
To get larger things into orbit requires larger launch vehicles—there's a reason the Saturn V used for the Apollo lunar missions was, and remains, the most powerful rocket ever launched. Getting humans to Mars will require even more power, but building a larger vehicle today wouldn't make economic sense—there wouldn't be enough customers to justify the development and cost. (Consider that Sputnik, the first human-made satellite, was the size of a beach ball, whereas modern satellites used for communication are often the size of a school bus.) The other option is to augment an existing design with additional boost—like adding more locomotive cars to a train to pull more freight. This is what SpaceX is doing, with one wrinkle: Rockets are usually disposable, one-mission-only devices. SpaceX has been perfecting reusable rockets. You don't throw away a locomotive at the end of the trip.
A modern launch vehicle involves two stages: a first stage, the majority of what you see standing on the launchpad, responsible for pushing most of the way into orbit; and a second stage to finish the job. By jettisoning the extra mass of the first stage when it's done burning its fuel, a smaller, more efficient engine can get just the upper stage and payload into orbit. It's like a delivery service that uses airplanes, barges, and semi-trucks to move packages most of the way around the world, then does the last leg to your house with a van.
So how much rocket is the first stage of the world's most powerful launch vehicle? The Falcon Heavy combines three first stages from the Falcon 9, SpaceX's current launcher, whose moniker refers to its power source: nine of SpaceX's proprietary Merlin engines (its predecessor, the Falcon 1—a pioneer in private space launches—had only one). So the Falcon Heavy will have a total of 27 Merlin engines, each producing 190,000 lb-ft of thrust at sea level. (Generally, the thrust of a rocket engine increases with altitude as atmospheric density decreases.) That's enough to put 119,000 pounds into orbit, which SpaceX notes is "a mass equivalent to a 737 jetliner loaded with passengers, crew, luggage, and fuel." To get the most payload into orbit, the Heavy could let its engines burn as long as possible—but that would leave no fuel to change trajectory, which is required for SpaceX to press its big advantage: recovery.
The Falcon 9's cycle—launch, then return of the first stage to terra firma or to a drone ship in the ocean—is becoming routine. Musk has already indicated he's planning to return all three components of the Falcon Heavy's first stage to Earth. The Falcon Heavy will use a common procedure for the three-part stage: The side boosters, clones of its center booster (essentially, each the first stage of a Falcon 9), burn out prior to the center and are jettisoned. The likely plan is to land the two outer boosters on solid ground, as their shorter burn times mean they will not have traveled as far, while the center booster will use a drone-ship landing, which has the flexibility to be placed wherever in the ocean is convenient, based on the rocket's trajectory. The more stages SpaceX can successfully recover, the cheaper launches will be for its customers.
If SpaceX's schedule holds, the first launch will happen before the holiday season. (In fact, Musk just tweeted that he plans for the maiden launch in November.) It carries a fair amount of risk in many phases of the mission, from the challenge of integrating three Falcon 9s to the recovery of three boosters—two by land, one by sea—in rapid succession. SpaceX's commitment to making Mars accessible means it will have to demonstrate that this scaled-up Falcon Heavy works and is reusable. Besides satellite launches, it is a key element to its planned Red Dragon capsule mission to Mars: an intermediate unmanned step toward sending people to the Red Planet. A demonstration of the Red Dragon is currently scheduled to launch in 2020 and land in 2021. While it may not be successful on the first try, Musk and company have shown patience and a willingness to learn from mistakes to get things right. Ultimately, they'll make the extraordinary become routine.
Bobak Ferdowsi is a systems engineer who helped land the Curiosity rover and is designing a satellite to observe Earth processes such as ice-sheet collapse. The opinions in this column are his own and not endorsed by his employer, NASA's Jet Propulsion Laboratory, where he is sometimes known as Mohawk Guy.