Chair Force Engineer

Wednesday, April 06, 2011

Building a Bigger Falcon

When Elon Musk speaks, the space community listens. Once-skeptical industry observers have to take his bold vision for the future of space travel seriously after the successful launches of Falcon I, Falcon 9, and most recently the Dragon spacecraft. With little hyperbole he's now predicting that his SpaceX team will launch Falcon Heavy, the world's largest current launch vehicle, by 2013.

If "Falcon Heavy" sounds familiar, that's because it is. The original Falcon 9 plan called for a "Falcon 9 Heavy" that would consist of three first stages in a parallel cluster with an upper stage on top. Each 1st stage booster would have nine Merlin engines, for a total of 27 engines igniting at liftoff. The mere thought of 27 engines is usually enough to give a mission assurance engineer nightmares. It draws comparisons to the Soviet N1 moon rocket, which was doomed by the complexity of its 30 first stage engines. But Falcon Heavy should be different. For starters, the N1's engines were designed and built by the inexperienced Kuznetsov design bureau. SpaceX also has the benefit of holding its rockets down after engine ignition to assess their performance before releasing it for flight.

The difference between the current Falcon Heavy design and previous plans for Falcon 9 Heavy are in the size of the payload. Falcon 9 Heavy would have competed with the current Delta IV Heavy, which currently flies about once or twice per year. But Elon Musk predicts that Falcon Heavy will now lift payloads twice as large as planned, roughly 50 tons. Among all American-made launchers, only the Saturn V and Shuttle were mightier. Why the change? I suspect it had a lot to do with the Augustine Commission's findings from 2009 that a larger launcher was needed for missions beyond earth orbit, especially Jeff Greason's belief that 50 tons was the upper limit for a single payload element. (After all, this was the approximate mass of the fully-fuelled Apollo spacecraft and Lunar Module.) This larger payload will likely be made possible after SpaceX develops its hydrogen-burning upper-stage. Stretching the first stage propellant tanks is also a possibility.

What would you do with a rocket that big? Elon Musk wants to send a manned Dragon spacecraft around the moon and back. For the wealthiest adventure seekers, shooting the moon would be the ultimate ride. Falcon Heavy would also be a key element in any effort to send humans to an asteroid, as President Obama has proposed. But in my eyes, a vehicle like Falcon Heavy opens the solar system to just about anywhere once in-space assembly and propellant transfer are perfected.