Wed. Dec 7th, 2022
Musk at the launch pad on Monday with Ars.
enlarge / Musk at the launch pad on Monday with Ars.

LAUNCH COMPLEX 39A, FLORIDA — Elon Musk confidently stepped out of a black SUV Monday afternoon, his mouth spreading in a wide grin as he surveyed the nearby launch pad. Just a quarter of a mile away, his Falcon Heavy rocket loomed high in the sky, the sunlight glinting on the three white boosters.

“It’s small, don’t you think?” he joked. “I think we need to improve our game.”

Thus began our interview with the founder of SpaceX on the eve of the launch of the most powerful rocket on Earth. During our time on the launch pad, we were most interested in the risks of such a test flight, with a brand new rocket containing the equivalent of four million pounds of TNT. And Musk was happy to oblige.

Biggest Concerns

“One of my biggest concerns is the interaction between booster and booster,” Musk explains. “You have a lot of dynamics there. Those missiles are very flexible; if they bend in unexpected ways, they can potentially affect each other.

With three Falcon 9 cores, the acoustic sound generated by the launch is three times greater than a single Falcon 9 launch. SpaceX engineers think they understand these interactions, but they haven’t tested them in flight. An unexpected resonance can cause a structural failure. These systems have all been extensively tested on the ground, but in the end nothing beats a real flight test.

“A lot can go wrong,” Musk admitted. “A really huge amount. I would really like to emphasize that the chance of success is not super high. I don’t want to mess it up – I’m inclined to say. Because I feel super optimistic. But I have the feeling that that optimism has no basis in fact. I feel like we have a two-thirds chance of success, but in reality we only have a 50-50 chance.”

get technical

Dressed in a black blazer and white t-shirt, with black designer jeans, Musk was in an exuberant mood on Monday. He had just driven up to the platform to see the rocket, and his family had joined him for the superlative of seeing such a large rocket within easy reach of the engines. When asked about the Falcon Heavy rocket’s ability to suffer an engine failure during launch, he replied, “I can get technical, right?”

“This is for Ars Technica,” we replied.

After a happy fit of laughter, Musk said, “OK.”

For a typical Falcon 9 launch, the booster can fail one of nine engines, right next to the pad. (A single Falcon 9 first stage engine failed in flight only once). The first stage can even survive two failures if the payload is not too heavy or if it goes into geostationary orbit. With the Falcon Heavy, the rocket could lose as many as six engines and still go into orbit — in theory.

“Something would have gone terribly wrong,” Musk said. “The chances of us losing six bikes and not really having anything bad gone wrong are pretty slim.”

Because this is a test flight, Musk said it’s a “softball mission.” This means that SpaceX will not push the boundaries in terms of dynamic pressure during launch. While the potential maximum dynamic pressure for a Falcon Heavy flight is “pretty high,” Musk said the maximum dynamic pressure for this launch will be about 15 or 20 percent less than a Falcon 9 going into geostationary orbit.

Beyond GEO

Despite the mixed potential for success, this won’t be just a test flight with a splashing payload. Musk said Monday that he hopes to demonstrate that it is possible to send payloads directly to geostationary orbit. This is one of the main requests of the US Air Force, which has requirements for the launch of national security. So with this mission, the upper stage will roll out for six hours before being re-ignited for the final time to send the Tesla Roadster into deep space.

“The six-hour coast is necessary for many of the major Air Force intelligence missions for direct injections into GEO,” Musk said. This six-hour period will be about twice as long as the longest coasts the Falcon 9 rocket has made.

After launch and the six-hour cruise, the Falcon Heavy’s upper stage will fire a third time to send the Tesla into orbit between Earth and Mars. This should take the Tesla as far as Mars’ orbit around the sun, or even a little further. Musk said the vehicle should get as far as 380 to 450 million km from Earth, depending on how the third burn progresses.

So how close is the Roadster to Mars? Musk did not offer a definitive answer. “Well, spatially close. Most people don’t realize how far apart things are in space. In sci-fi movies, everyone looks up close, as opposed to a bunch of distant, tiny, silent dots.”

Go to discussion…

By akfire1

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